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UBC Theses and Dissertations

The reclamation of Sullivan mine iron tailings Ames, Susan Eveline 1981

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THE RECLAMATION OF SULLIVAN MINE IRON TAILINGS SUSAN EVELINE AMES (B .Sc . Dalhous ie U n i v e r s i t y , 1976) A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE THE FACULTY OF GRADUATE STUDIES (Department of S o i l Sc ience) We accept t h i s t h e s i s as conforming to the requ i r ed standard by in THE UNIVERSITY OF BRITISH COLUMBIA May, 1981 c^ Susan Eve l i ne Ames In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of S o i l Science  The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date - A p r i l ?L, 1QS1 np.fi I 9 /Ten ABSTRACT The S u l l i v a n Mine i ron t a i l i n g s pose ser ious problems to rec lamat ion which r e s u l t from t h e i r high ac id producing p o t e n t i a l , extreme s a l i n e c ond i t i o n s , r e l a t i v e l y high concent ra t ions of heavy metals and tendency to cement upon o x i d a t i o n . Ox ida t ion r e s u l t s in the format ion of a hard imper-meable l ayer r e f e r r ed to as a fe r rug inous cap. Standard techniques of rec lamat ion o r i en ted towards vegeta t ion es tab-l ishment on the t a i l i n g s have been unsuccess fu l due to the adverse phys i ca l and chemical c h a r a c t e r i s t i c s of the t a i l i n g s . Covering the t a i l i n g s w i th s o i l or overburden may be the on ly s o l u t i on to t h i s d i f f i c u l t rec lamat ion problem. However, the quest ion a r i ses whether the a c i d s , s a l t s , and meta l s , r e s u l t i n g from cont inuous o x i d a t i o n , would migrate upwards under evaporat ing cond i t i ons and C a p i l l a r y movement. This may u l t i m a t e l y lead to the contaminat ion of the overburden, making i t i n e f f e c t i v e as a cover . To t e s t t h i s , a l abo ra to ry column study was set up under acce le ra ted c o n d i t i o n s . The experiment had two main ob j e c t i v e s : 1) t o t e s t whether overburden, p laced on the sur face of the ox i d i z ed i ron t a i l i n g s , would become contaminated, in t ime , by the a c i d s , s a l t s and metals from the t a i l i n g s ; and 2) to t e s t whether a b a r r i e r of grave l between the overburden and t a i l i n g s would e f f e c t i v e l y i n su l a t e the overburden from po t en t i a l contaminat ion from the t a i l i n g s . The experiment was o r i en ted towards examining the processes which would occur i f e i t h e r of the t reatments were adopted in a f i e l d s i t u a t i o n . P r e d i c t i o n s of the processes were made from the analyses of so l u t i on s ex t rac ted at s p e c i f i c l o ca t i on s on a monthly bas i s and from the analyses of - i i -overburden samples obta ined through de s t r u c t i v e sampling of the columns at 3 , 6 and 9 month i n t e r v a l s . Sampling at s p e c i f i c l o ca t i ons and at t ime i n t e r v a l s y i e l ded the data requ i red fo r a ra te of m igra t ion es t imat ion and an eva lua t i on of the f a c t o r of t ime. The r e s u l t s of the study i nd i ca ted that the b a r r i e r was e f f e c t i v e . The overburden in the columns wi th the grave l was not contaminated. The over -burden in the second treatment d id become contaminated due to the d i r e c t contact w i th the t a i l i n g s . In t h i s t reatment , ca lc ium s a l t s migrated r a p i d l y to the sur face in a l l of the columns w i th i n 1 month of the i n i t i a -t i o n of the experiment suggest ing that in a f i e l d s i t u a t i o n s a l i n i t y e f f e c t s may be the dominant f a c t o r i n i t i a l l y , i n ' i n h i b i t i n g vegeta t ion estab l i shment on an overburden cover p laced in d i r e c t contact wi th the ox i d i z ed i ron t a i 1 i n g s . The overburden was s e conda r i l y contaminated, to rough ly 20 cm (from the overburden t a i l i n g s boundary), by i r o n , z i n c , and copper s a l t s . A l l of the metals migrated to rough ly 20 cm, c on t r o l l e d by pH and most of the contam-i na t i on occurred w i t h i n the f i r s t 3 months of the exper iment. Above 20 cm a l k a l i n e cond i t i ons caused the p r e c i p i t a t i o n of the me ta l s . These metals were not i r r e v e r s i b l y p r e c i p i t a t e d however, as they were e a s i l y removed by ac id e x t r a c t i o n suggest ing tha t they would be remob i l i z ed wi th the development of ac id cond i t i ons s u f f i c i e n t to e f f e c t t h e i r s o l u b i l i t y . Iron d id not migrate to the same extent as the other meta l s . This metal became concentrated near the overburden- ta i1 ings boundary where i t i r r e v e r s i b l y p r e c i p i t a t e d in to a hard pan. Aluminum and manganese, which contaminated the overburden, were der ived from the overburden. This r e su l t ed from the des t ru c t i on of the overburden - i i i -minera l s by m ig ra t i ng ac ids and the consequental r e l ease of aluminum and manganese in to a so l ub l e form. The overburden in the treatment with the grave l became h i gh l y d e s i c c a t -ed as the connec t i on , through s i m i l a r p a r t i c l e s i z e , between the water t a b l e , l oca ted in the t a i l i n g s , and the overburden, was broken by the g r a v e l . Therefore i t i s p red i c ted that s i m i l a r cond i t i ons would occur in the f i e l d . Consequent ly, drought r e s i s t a n t p lant spec ies or supplemental i r r i g a t i o n would be requ i red i f the b a r r i e r approach were adopted. The r e s u l t s . i n d i c a t e that the column study was an e f f e c t i v e means of s tudy ing the k inds of processes which would occur i f the rec lamat ion of the t a i l i n g s was approached by cover ing them wi th overburden (or s o i l ) . I f the overburden i s p laced d i r e c t l y on the S u l l i v a n Mine ox i d i z ed i ron t a i l i n g s i t would become contaminated wi th t ime and i ron pan format ion would occur . Cover ing can be an e f f e c t i v e approach to rec lamat ion i f a grave l b a r r i e r i s used to separate the overburden from the t a i l i n g s . TABLE OF CONTENTS ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF PLATES LIST OF APPENDICES ACKNOWLEDGEMENT INTRODUCTION 1.0 Se t t i ng o f - t he S u l l i v a n Mine Iron T a i l i n g s Pond 1.1 In t r oduc t i on 1.2 Loca t ion 1.3 S u l l i v a n Mine Operat ion 1.4 S u r f i c i a l Geology 1.5 S o i l s 1.6 C l imate 1.7 B i ogeoc l ima t i c Zone 2.0 P rope r t i e s of the S u l l i v a n Mine I ron T a i l i n g s and The i r Imp l i c a t i on to Reclamat ion 2.1 In t roduc t i on 2.2 S u l l i v a n Mine Reduced T a i l i n g s 2.3 Ox id i zed I ron T a i l i n g s PAGE 3.0 L i t e r a t u r e Review of Var ious Approaches to the Reclamation 33 of Ac id and Metal Contaminated Mine Wastes 3.1 In t roduc t i on 33 3.2 Approaches t o Reclamation 33 3.2 .1 Ac id and Heavy Metal To le ran t P lan t Species 35 3.2.2 Liming 38 3 .2 .3 Leaching 43 3.2.4 F lood ing ' 44 3.2 .5 Bac te rc ides 45 3.2.6 Burying t 45 3.2.7 Cover ing ' 50 3.2.8 Amendments 54 3 .2 .9 Mix ing 55 3.3 Summary and Conc lus ions 56 4.0 Exper imenta l Design 62 4.1 In t roduc t i on 62 4.2 Ma te r i a l s 64 4.3 Methods 66 4 .3 .1 Sample P repara t i on 66 4 .3 .2 Column Design 68 4 .3 .3 Water Table Apparatus 71 4 .3 .4 Method of Pack ing 71 4 .3 .5 Tensiometer Apparatus 74 - v i -PAGE Exper imental Design (Cont inued) 4 .3 .6 So l u t i o n Sampling Apparatus 78 4 .3 .7 Rep l i c a t i on s 79 4 .3 .8 Promotion of Acce l e ra ted Cond i t ions 80 4 .3 .9 Column Layout P lan 81 4 .3 .10 So l u t i o n Sampling 81 4 .3 .11 Column S o i l Sampling 84 4.4 Evaporat ion and R e l a t i v e Humidity 86 Chemcial Ana l y s i s of So lu t i ons Co l l e c t ed from Overburden and T a i l i n g s 88 5.1 In t roduc t i on 88 5.2 Methods and Ma t e r i a l s 89 5.3 Resu l t s and D i scuss ion 89 5.3 .1 pH Ana l y s i s 90 5.3.2 Iron Ana l y s i s 93 5 .3 .3 Aluminum and Copper Ana l y s i s 106 5.3.4 Z inc and Manganese Ana l y s i s 113 . 5 .3 .5 N icke l Ana l y s i s 119 5.3.6 Other Meta ls 123 5.3.7 So lub le S a l t s 125 5.3.8 Ox ida t i on - Reduct ion P o t e n t i a l s 132 5.4 Summary and Conc lus ions 133 - v i i -PAGE 6.0 Chemical Ana l y s i s of Overburden " S o i l " Samples 136 6.1 In t r oduc t i on 136 6.2 Methods and Ma t e r i a l s 138 6 .2 .1 To ta l E lemental Ana l y s i s 138 6 .2 .2 Hydroch lo r i c A c i d E x t r a c t i o n 139 6 .2 .3 S o i l React ion 140 6 .2 .4 E l e c t r i a l C onduc t i v i t y . 141 6.2.5 S t a t i s t i c a l Ana l y s i s 141 6.3 Resu l t s and D i scuss ion 145 6.4 Summary and Conc lus ions 167 7.0 Summary and Conc lus ions 171 LITERATURE CITED 179 - v i i i -LIST OF TABLES PAGE 2.1 Chemical and phys i ca l p rope r t i e s of i ron t a i l i n g s in 17 o x i d i z ed and unox id i zed s t a t e s . 2.2 A l t e r a t i o n products of s u l f i d i c m ine ra l s . 22 3.1 The e f f e c t s of pH ( l ime l e v e l ) upon the s u r v i v a l of t r ee 42 seed l ings grown on smelter contaminated s o i l s . 3.2 Resu l t s of mean separa t ion procedures r e l a t i n g the 42 e f f e c t s of increased s o i l pH upon e x t r a c t i b i 1 i t y of heavy metals in a smelter contaminated s o i l . 6.1 S i g n i f i c a n c e r e s u l t s from the Analyses of Var iance t e s t 146 fo r the t o t a l e lemental a n a l y s i s , pH, and e l e c t r i c a l c o ndu c t i v i t y of the overburden. 6.2 S i g n i f i c a n c e r e s u l t s from the Analyses of Var iance t e s t 146 fo r the ac id e x t r a c t ab l e ana l y s i s of the overburden. - i x -PAGE 6.3 S i g n i f i c a n c e r e s u l t s from the Analyses of Var iance t e s t 148 f o r the t o t a l e lemental a n a l y s i s , pH, and e l e c t r i c a l c o n d u c t i v i t y of the overburden in Treatment 1. 6.4 S i g n i f i c a n c e r e s u l t s from the Analyses of Var iance t e s t 148 f o r the t o t a l e lemental a n a l y s i s , pH, and e l e c t r i c a l c o n d u c t i v i t y of the overburden in Treatment 2. 6 . 5 ( a ) - ( f ) S i g n i f i c a n c e r e s u l t s from the Mann Whitney U-Test; 163-164 t o t a l e lemental a na l y s i s , pH, e l e c t r i c a l c o n d u c t i v i t y of overburden at Leve l s 1-9 (a) 3 months (b) 6 months (c) 9 months; ac id e x t r a c t ab l e ana l y s i s of overburden at Leve l s 1-9 (d) 3 months (e) 6 months ( f ) 9 months. - x -LIST OF FIGURES PAGE 3.1 Su l f a t e c on t r i b u t i n g s po i l volume c on t r o l l e d by 51 d i f f u s i o n accord ing to p a r t i c l e s i z e . 4.1 Column Des ign. 69 5.1(a) pH p l o t t e d aga inst t ime f o r overburden at Leve l C, 92 Treatment 1 versus Treatment 2 (from monthly e x t r a c t i o n s ) . 5.1(b) pH p l o t t ed aga inst t ime fo r overburden at Level D, 92" Treatment 1 versus Treatment 2 (from monthly e x t r a c t i o n s ) . 5.2 Monthly ex t rac ted i ron from overburden at Level C, 9 5 Treatment 1 versus Treatment 2 (columns 10, 12 and 16) . 5.3 Monthly ex t rac ted i ron from t a i l i n g s at Level A, 101 Treatment 1 versus Treatment 2. 5.4 Monthly ex t rac ted aluminum from overburden at Level C, 107 Treatment 1 versus Treatment 2 (columns 10, 12 and 16) . - x i -PAGE 5.5 Monthly ex t rac ted copper from overburden at Level C, 107 Treatment 1 versus Treatment 2 (columns 10, 12 and 16) . 5.6 pH p l o t t e d aga inst t ime from overburden, column 10 (TR2) 111 versus column 12 (TR2) versus column 16 (TR2) (monthly e x t r a c t i o n s ) . 5.7 Monthly ex t rac ted aluminum from t a i l i n g s at Level A , 111 Treatment 1 versus Treatment 2. 5.8 Monthly ex t rac ted z i nc from overburden at Level C, 114 Treatment 1 versus Treatment 2 (columns 10, 12 and 16) . 5.9 Monthly ex t rac ted manganese from overburden at Level C, 114 Treatment 1 versus Treatment 2 (columns 10, 12 and 16) . 5.10 Monthly ex t rac ted z i nc from t a i l i n g s at Level A, 117 Treatment 1 versus Treatment 2. 5.11 Monthly ex t rac ted n i c ke l from overburden at Leve l C, 120 Treatment 1 versus Treatment 2 (columns 10, 12 and 16) . - x i i -PAGE 5.12 Monthly ex t rac ted n i c ke l from overburden at Leve l s C and 121 D, Treatment 1 versus Treatment 2 f o r : 3 month columns (a) 14 (b) 17 (c) 18; 6 months columns (d) 11 (e) 13 ( f ) 15; and 9 month columns (g) 10 (h) 12 ( i ) 16. 5.13 Monthly ex t rac ted lead from overburden at Levels C and ' 124 D, Treatment 1 versus Treatment 2 f o r : 3 month columns (TR2) (a) 14 (b) 17 (c) 18; 6 month columns (TR2) (d) 11 (e) 13 ( f ) 15; and 9 month columns (g) 10 (h) 12 ( i ) 16. 5.14(a) E l e c t r i c a l c o ndu c t i v i t y p l o t t ed aga inst t ime fo r 126 overburden at Level D, Treatment 1 versus Treatment 2 (from monthly e x t r a c t i o n s ) . 5.14(b) E l e c t r i c a l c o ndu c t i v i t y p l o t t ed aga inst t ime fo r 126 overburden at Leve l C, Treatment 1 versus Treatment 2 (from monthly e x t r a c t i o n s ) . 5.15 Monthly ex t rac ted ca lc ium from the overburden at Leve l D, 129 Treatment 1 versus Treatment 2. 5.16 Monthly ex t rac ted magnesium from the overburden at Level D, 130 Treatment 2 (columns 10, 12 and 16) . - x i i i -PAGE 5.17 Monthly ex t rac ted magnesium from the overburden at Level D, 131 Treatment 1 (columns 6, 7 and 8 ) . 6 .1(a) Tota l elemental manganese from overburden, Treatment 1 150 versus Treatment 2 (TR2) f o r 3, 6 and 9 month time pe r i od s . 6 .1(b) Ex t r a c t ab l e manganese from overburden, Treatment 1 150 versus Treatment 2 (TR2) f o r 3, 6 and 9 month t ime pe r i ods . 6.2(a) pH versus height in overburden, Treatment 2, 3 month 152 columns (columns 14, 17, 18 ) . 6.2(b) pH versus height in overburden, Treatment 2, 6 month 152 columns (columns 11 , 13, 15) . 6 .2(c ) pH versus height in overburden, Treatment 2, 9 month 153 columns (columns 10, 12, 16 ) . 6 .2(d) pH versus height in overburden, Treatment 2, 3 versus 6 153 versus 9 month columns. - x i v -PAGE 6.3(a) Tota l e lemental z i nc from overburden, Treatment 1 versus 156 Treatment 2 (TR2) f o r 3, 6 and 9 month t ime pe r i od s . 6.3(b) Ex t r a c t ab l e z i n c from overburden Treatment 1 versus 156 Treatment 2 (TR2) f o r 3, 6, and 9 month time pe r i ods . 6 .4(a) To ta l e lemental i ron from overburden, Treatment 1 versus 158 Treatment 2 (TR2) f o r 3 , 6 and 9 month pe r i od s . 6.4(b) Ex t r a c t ab l e i ron from overburden, Treatment 1 (TR1) 158 versus Treatment 2 (TR2) f o r 3, 6 and 9 months. 6.5 E l e c t r i c a l c o n d u c t i v i t y , Treatment 2 (TR2), 3 versus 6 166 versus 9 months, and Treatment 1 (TR1). - xv -LIST OF PLATES PAGE 1.1 A i r photograph of the S u l l i v a n Mine i ron t a i l i n g s pond. 6 2.1 View of the S u l l i v a n Mine i ron t a i l i n g s pond wi th wooden 12 launders b u i l t around the per imeter of the pond. 2.2 Formation of a l l u v i a l fans through depos i t i on of reduced 13 S u l l i v a n Mine i ron t a i l i n g s . 2.3 F l u v i a l channel ing and g u l l y i n g in the t a i l i n g s . 15 2.4 I n i t i a l stages of o x i da t i on of the i ron t a i l i n g s showing 24 c r a ck i ng of the sur face and s a l t c rus t fo rmat ion . 2.5 Advanced stages of ox i da t i on with s a l t c rus t format ion 24 and water ponded on the sur face d i s co l o r ed by ox i d i z ed i ron compounds. 2.6 Ferruginous caps forming dome- l ike s t r u c t u r e on the 29 sur face of the ox i d i zed i ron t a i l i n g s pond. - xv i -PAGE 2.7 P r o f i l e of i ron t a i l i n g s showing d i scont inuous hor izons 31 wi th v a r i a t i o n in s t r u c t u r e , t e x t u r e , and degree of weather ing wi th depth. 4.1 D i t c h , in stony g l a c i a l t i l l depos i t , l y i n g along the 65 north boundary of the S u l l i v a n Mine i ron t a i l i n g s pond. 4.2 G l a c i a l t i l l depos i t located north of the S u l l i v a n Mine 65 i ron t a i l i n g s pond. 4 .3 Narrow columns in p i l o t p ro jec t i l l u s t r a t i n g edge e f f e c t s . - 70 4.4 Wooden chamber const ruc ted in the S o i l Sc ience Dept . , 76 U.B.C. The manometer apparatus is attached to the ou t s i de of the chamber. 4.5 Front view of Treatment 2 column with sampling apparatus 77 at Leve ls A, B, C and D. Rear view of Treatment 1 columns with psychrometers located at Leve l s C and D and manometer apparatus at Leve ls A and B. 4.6 View of the i n t e r i o r of the "growth" chamber w i th 82 columns, thermohydrograph, thermostat , e t c . in p l ace . r. x v i i -PAGE 4.7 Treatment 1 column s p l i t and ready fo r sampl ing. 85 4.8 Treatment 2 column s p l i t and ready fo r sampl ing. 85 -5.1 Treatment 1 columns with s u l f u r and other compounds 96 p r e c i p i t a t e d on the unders ide of the grave l fragments as a consequence of excess wa te r ing . 5.2 Iron contaminat ion of the overburden by the t a i l i n g s , in 96 a Treatment 2 column, i nd i ca ted by the orange-brown co lor . ' 6.1 Ye l lowish-brown c o l o r , c h a r a c t e r i s t i c of j a r o s i t e , 160 v i s i b l e in the contaminated overburden. - x v i i i -LIST OF APPENDICES PAGE Appendix 1.1 C l ima t i c data f o r the Kimber ley area . 192 Appendix 2.1 Draf t of three undisturbed non-vegetated S u l l i v a n 193 Mine i ron t a i l i n g s p i t p r o f i l e s i n d i c a t i n g the amount of v a r i a b i l i t y across the pond. Appendix 2.2 P r o f i l e d e s c r i p t i o n of undisturbed non-vegetated 194 S u l l i v a n Mine i ron t a i l i n g s sample 7 4 - S F - l . Appendix 2.3 P r o f i l e d e s c r i p t i o n of undisturbed non-vegetated 195 S u l l i v a n Mine i ron t a i l i n g s sample 74-SF-2. Appendix 2.4 P r o f i l e d e s c r i p t i o n of undis turbed non-vegetated 196 S u l l i v a n Mine i ron t a i l i n g s sample 74-SF-3 . Appendix 3.1 P r o f i l e d e s c r i p t i o n of overburden. 197 Appendix 3.2 P a r t i c l e s i z e ana l y s i s of overburden. 198 Appendix 3.3 Water r e t en t i on data fo r overburden. 199 - x i x -PAGE Appendix 4.1 Rat io (%) of ex t rac ted i ron and i ron added 200 through contaminat ion at Level 1 in s o i l samples from overburden in Treatment 2 columns for 3, 6 and 9 months. Appendix 4.2 Rat io (%) of ex t rac ted z i nc and z inc added 201 through contaminat ion at Level 1 in s o i l samples from overburden in Treatment 2 columns f o r 3 , 6 and 9 months. Appendix 5.1 Tota l a n a l y s i s , pH and e l e c t r i c a l c o ndu c t i v i t y (E .C . ) 202 of overburden. Appendix 5.2 Chemical ana l y s i s of the overburden ac id e x t r a c t i o n s . 206 Appendix 6.0 Development of an " I n s i t u " Ox ida t i on Reduct ion 210 P o t e n t i a l Measurement Technique. - xx -ACKNOWLEDGEMENTS I wish to extend my g r a t i t ude and app rec i a t i on to Dr. L.M. Lavku l i c h as the supe rv i so r o f my t he s i s and f o r h i s constant encouragement., pa t i ence , gu idance, and suppor t , both f i n a n c i a l and mora l , throughout my program. Spec i a l thanks to W i l l y Hendershot, Compton Paul and G i l l e s Ga lzy f o r t h e i r he l p fu l sugges t i ons , c r i t i c i s m and f r i e n d s h i p . Spec ia l thanks to B i l l and Bev Herman f o r t h e i r i n d i v i d u a l a i d g iven so e n t h u s i a s t i c a l l y and in many c i r cumstances . I express my g r a t i t ude to Mark Sondheim f o r h i s i n va l uab l e a i d i n the s t a t i s t i c a l ana l y ses . Thanks are a l so extended to J u l i e Lans iquo t , Kath leen Renton, Rupert C la rk and Joyce Ho l l and who e n t h u s i a s t i c a l l y a s s i s t e d in the product ion o f my t he s i s and to Paul C h r i s t i e who o f f e r ed h i s support and encourangement,needed f o r the f i n a l product ion o f my t h e s i s . Thanks to the t e chn i c a l s t a f f i n the Department of S o i l Sc ience who a ided i n my research w i th extended g r a t i t ude to B i l l Cheang p a r t i c u l a r l y f o r the f i n e cons t r u c t i on o f the "growth chamber". T a l so wish to express my g r a t i t ude to Dr. Cha r l i e Rowles and Dr. Jan de V r i e s , Department of S o i l S c i ence , and Bob Gard ine r , Cominco L t d . , f o r t h e i r c r i t i c i s m and he l p fu l suggest ions in my t h e s i s . I wish to express my thanks to a l l o f the p ro fessors i n ' t h e Department o f S o i l Sc ience f o r t h e i r f r i e n d s h i p which g r e a t l y con t r i bu ted to the enjoyment o f my program. - xxi -F i n a l l y , very spec i a l thanks to Ed f o r h i s pa t ience dur ing the w r i t i n g of my t h e s i s . Th i s research was made po s s i b l e p r i m a r i l y through a grant from Cominco L t d . , T r a i l , B.C. - xxii -INTRODUCTION S u l l i v a n Mine, K imber ley , B.C. i s the l a rges t l e a d - z i n c - i r o n ore mine in B r i t i s h Columbia. I t was d i scovered in 1892 and has been in cont inuous opera t ion s ince 1909. Though the mine i s s t i l l a c t i v e , with a p red i c ted l i f e span to the year 2000, procedures are being developed f o r the u l t ima te rec lamat ion of the waste m a t e r i a l s . As the S u l l i v a n operat ion i s under-ground, rec lamat ion i s main ly concerned wi th the waste rock , the s i l i c e o u s , gypsum and i ron t a i l i n g s m a t e r i a l s . Problems in r e c l a im ing the i r on t a i l i n g s are p a r t i c u l a r l y over-whelming. The i ron t a i l i n g s have a high ac id and s a l t producing p o t e n t i a l , r e l a t i v e l y high concent ra t ions of manganese, aluminum, z i n c , copper, and i r on and upon exposure to atmospheric c ond i t i o n s , develop a hard impervious p l a t y s t r u c t u r e at or near the su r f ace , known as a fe r rug inous cap. The f r e sh t a i l i n g s are composed of 85% reduced i ron s u l f i d e s , dominant ly in the p y r r h o t i t e form, which i s h i g h l y r e a c t i v e . Under c e r t a i n cond i t i ons spontaneous combustion can occur . Attempts at the rec lamat ion of the S u l l i v a n Mine i ron t a i l i n g s , through standard techniques have met with f a i l u r e due to the adverse phys i ca l and chemical p r ope r t i e s of the i r on t a i l i n g s in the ox i d i z ed form. One procedure which may be cons idered invo lves the cover ing of the t a i l i n g s with overburden or s o i l to some depth and to e s t a b l i s h vege ta t i ve growth on the cover ing m a t e r i a l . The quest ion r a i s e d , however, i s : w i l l the ac id produced by the o x i d i z i n g t a i l i n g s s l ow l y migrate upwards, through the overburden and, with t ime, contaminate the overburden with a c i d s , so lub le s a l t s and heavy metals to make the overburden u l t i m a t e l y i n e f f e c i v e ? - 1 -To answer t h i s ques t i on , a l abo ra to ry study was set up with two main o b j e c t i v e s : 1) To t e s t whether overburden, app l ied d i r e c t l y onto the sur face of the S u l l i v a n Mine ox i d i zed i ron t a i l i n g s , would become seve re l y contaminated in t ime with contaminat ion occu r r i ng as a f unc t i on of the po t en t i a l upward m ig ra t i on of a c i d s , s a l t s and metals from the t a i l i n g s , and 2) to t e s t whether a b a r r i e r , in t h i s case a layer of g r a v e l , would prov ide " i n s u l a t i o n " to the overburden from the o x i d i z ed i r on t a i l i n g s , thus , i n h i b i t i n g po t en t i a l con tamina t ion . The c a rd i na l po int of the exper imental des ign of the study is the consequence of t ime. Apparent successes in rec lamat ion have proven to be u t t e r f a i l u r e s a f t e r supplemental a ids are removed (eg. f e r t i l i z e r s , i r r i g a t i o n , e t c . ) . Thus, the main t h ru s t of the experiment is the cons i d -e ra t i on of severe contaminat ion of the overburden with, respect to t ime as a consequence of the contact with t a i l i n g s . There fo re , the experiment was set up under acce le ra ted and c on t r o l l e d cond i t i ons in the l abo ra to ry as a column s tudy . The p ro j e c t was in opera t ion f o r 9 months but sub-sets of columns from each treatment were a lso d ismant led a f t e r 3 and 6 months. P r ed i c t i o n s of the k inds of processes which would occur i f the t a i l i n g s were covered d i r e c t l y or i f the grave l approach was adopted, were made from con t r i bu t i on s of data c o l l e c t e d by mon i to r ing and comparing chemical changes occu r r i ng in the two treatments on a monthly bas i s by s o l u t i o n e x t r a c t i o n and a f t e r the three t ime per iods through chemical analyses of the column m a t e r i a l s . - 2 -The experiment cannot s imu la te t r ue f i e l d c ond i t i o n s . I t was designed as a means of examining the k inds of processes which would occur i f the cover ing approach was adopted as a techn ique fo r the rec lamat ion of S u l l i v a n Mine i ron t a i l i n g s or ma te r i a l s s i m i l a r to them. - 3 -1.0 Se t t i ng of the S u l l i v a n Mine Iron T a i l i n g s Pond 1.1 In t roduc t i on The approach of t h i s study i s s p e c i f i c a l l y geared to the S u l l i v a n s i t u a t i o n . Informat ion on the mine l o c a t i o n , the composi t ion of the ore body, the l e v e l s of p roduc t i on , and the extent of the waste area are important to understanding the nature of the problem. Informat ion on the environment of the t a i l i n g s i s c r u c i a l to understanding the f e a s i b i l i t y of the approach adopted in the rec lamat ion of these p a r t i c u l a r t a i l i n g s . In p a r t i c u l a r , c l ima te and s u r f i c i a l ma te r i a l s have been incorporated in to the s tudy . For example, the rec lamat ion of t a i l i n g s s i m i l a r in chemical composi t ion and phys i ca l p rope r t i e s to the S u l l i v a n Mine i ron t a i l i n g s would be approached d i f f e r e n t l y i f they were located in a reg ion with a wetter c l ima t e . A l so the overburden used in t h i s experiment was removed from a depos i t of s u r f i c i a l ma t e r i a l s ne ighbour ing the t a i l i n g s pond. This chapter t h e r e f o r e , b r i e f l y d i scusses the l o ca t i on and nature of the mining ope ra t i on , the reg iona l c l ima te of the mine and t a i l i n g s s e t t i n g , b i ogeoc l ima t i c zone i n f o rma t i on , and the s o i l s , geology and s u r f i c i a l ma t e r i a l s c h a r a c t e r i s t i c of the area . 1.2 Loca t ion The S u l l i v a n Mine opera t ion i s located j u s t ou t s ide and northwest of the K imber ley towns i te in southeastern B r i t i s h Columbia ( l a t . 49°40' N, l o ng . 115°55' W) at an e l e va t i on between 1300 and 1400 metres . Reg i ona l l y , the K imber ley area l i e s on the eastern s lopes of the P u r c e l l Mountains border ing the intermounta in p l a i n s of the Rocky Mountain Trench. - 4 -1.3 S u l l i v a n Mine Operat ion The mine i s one of the o ldes t in the prov ince of B r i t i s h Columbia. The opera t ion cons i s t s of the underground mine, the concent ra to r , the waste rock dump and the s i l i c e o u s , gypsum and i ron t a i l i n g s ponds. The ore body is a hydrothermal or high temperature replacement of t h i n bedded a r g i l l a c eou s depos i t s o c cu r r i ng in the A l d r i dge Formation on the east s ide of the P u r c e l l Mountains (F reeze , 1961). The cen t ra l po r t i on of the ore i s dominant ly p y r i t e (FeS2) i n the west and p y r r h o t i t e ( FeySs ) in the eas t . Surrounding the p y r i t e and p y r r h o t i t e depos i t s i s a lead r i c h rock con ta i n i ng var ious amounts of s i l v e r , t i n , and antimony (Geo log i ca l Survey of Canada, 1970). The present output of the mine i s rough ly 7,700 tonnes of ore per opera t ing day, produc ing 770 tonnes of z i n c concentrate and 500 tonnes of lead concent ra te d a i l y . The t o t a l d i sposa l area of the mine i s approx imate ly 415 hectares (1025 acres) of which 241 are i ron t a i l i n g s (Gard iner and S t a t h e r s , 1975). A p lan view of the layout of the i ron t a i l i n g s pond is shown on an a e r i a l photograph ( P l a t e 1 .1) . The i r on t a i l i n g s pond has been b u i l t up s p a c i a l l y and in height through cont inuous despos i t i ons of t a i l i n g s over severa l decades. It i s g ene r a l l y devoid of vegeta t ion except f o r a s a l t marsh community which is p e r i o d i c a l l y observed in the undrained depress ion of the f r e sh t a i l i n g s . Robbins (1978) noted f i v e spec ies of p lan ts in undrained areas of which Typha ( c a t - t a i l ) predominated wi th l o c a l i z e d i n c l u s i on s o f Juncus ( r u sh ) . (The remaining three have not been i d e n t i f i e d . ) - 5 -P l a t e 1.1 A i r Photograph o f the S u l l i v a n Mine Iron T a i l i n g s Pond. - 6 -The i ron t a i l i n g s pond is s t i l l a c t i v e but la rge areas have been o x i d i z e d . The economic l i f e span of the mine is an t i c i pa t ed to reach at l e a s t the year 2000 and thus the i ron t a i l i n g s pond is p red i c ted to be a c t i v e u n t i l that t ime. 1.4 S u r f i c i a l Geology The landscape surrounding the mine area was modi f ied dur ing the P l e i s t o cene g l a c i a t i o n and unconso l idated overburden o v e r l i e s most of the su r f a ce . G l a c i a l t i l l , g l a c i o f l u v i a l and c o l l u v i a l ma te r i a l s are predom-inant and sma l le r areas of lake sediments, organic depos i t s and bedrock are s ca t t e r ed throughout the r eg i on . ( F u l t o n , 1968; C lague, 1974.) 1.5 S o i l s In the survey c a r r i e d out by K e l l y and Sprout (1956) the s o i l s surrounding the mine s i t e were found to belong to the Hyak Sandy Loam S e r i e s . These are g r a v e l l y g l a c i a l t i l l s o i l s ranging from a sandy loam to a s i l t loam. Accord ing to Morton (1976) the s o i l s adjacent to the d i sposa l ponds are c l a s s i f i e d as O r t h i c Humo-Ferr ic Podzols wi th a s i l t loam t e x t u r e . 1.6 C l imate K imber ley has been descr ibed as being in the 'd ry b e l t 1 of B r i t i s h Columbia (R i ce , 1937). The c l i m a t i c reg ion i s south-east i n t e r i o r . I t r ece i ves approx imate ly 378 mm of p r e c i p i t a t i o n of which rough ly 229 mm are r a i n f a l l . Summer temperatures reach a maximum of 32°C and K imber ley exper iences a r e l a t i v e l y long growing season (181 days ) . The c l i m a t i c data f o r K imber ley are given in Appendix 1.1. - 7 -1.7 B i ogeoc l ima t i c Zone The S u l l i v a n Operat ion l i e s w i t h i n the I n t e r i o r Douglas F i r b i ogeoc l ima t i c zone ( K r a j i n a , 1969). The land adjacent to the mine at 1300 to 1400 metres i s in the wetter Fa l se Boxwood subzone and has the c a p a b i l i t y f o r moderate f o r e s t y i e l d . The concent ra tor and the d i sposa l areas to the southeast of the town are w i t h i n the d r i e r P inegrass subzone. Areas adjacent to the d i sposa l s i t e s are best su i ted f o r na t i ve range. - 8 -2.0 P rope r t i e s of the S u l l i v a n Mine Iron T a i l i n g s and The i r Imp l i c a t i ons t o Reclamation 2.1 In t r oduc t i on A un i ve r sa l statement that can be app l ied to metal mine t a i l i n g s is tha t they are h o s t i l e to p l a n t s . Attempts at r e c l a im ing them through vege ta t i on es tab l i shment are o f ten unsuccess fu l due to poor phys i ca l p r o p e r t i e s , lack of organ ic mat ter , and a low na t i ve f e r t i l i t y s ta tus coupled w i th a n e g l i g i b l e ca t i on exchange c apa c i t y . D i f f i c u l t i e s in r e h a b i l i t a t i o n programs a r i s i n g from t h e i r adverse p rope r t i e s are enhanced by the inherent capac i t y of the s p o i l to change r a p i d l y as a f unc t i on of environmental f a c t o r s . This i s f u r t he r promoted by t h e i r f i n e p a r t i c l e s i z e . For i n s tance , the t a i l i n g s o r i g i n a t e from rock which was formed under h igh temperatures and pressures below the sur face of the e a r t h . In the mining opera t i on the minera l con ta in i ng rock i s f i n e l y crushed [ to 2 mm s i z e or less and can be as f i n e as 0.010 microns (Duncan, 1972) ] . Fo l low ing the crush ing process , the ground rock is subjected to a chemical ore e x t r a c t i o n ( f l o t a t i o n p r o ce s s ) . Once the ore i s removed by t h i s method, the waste or t a i l i n g s mate r i a l is t r a n s f e r r ed to an .impoundment area gene ra l l y in s l u r r y form. In the impoundment enc losure the t a i l i n g s are exposed to an environment of lower temperatures and pressures than c h a r a c t e r i s t i c of the geo l og i ca l cond i t i ons under which they were formed. At atmospheric c ond i t i o n s , the m ine ra l s are no longer s t a b l e . As dominant ly sand s i z e p a r t i c l e s or f i n e r , l a r ge su r face area i s exposed t o weather ing , making them extremely - 9 -su s c ep t i b l e to chemical r e a c t i o n s . The chemical r e a c t i o n s , by t h e i r na ture , may a f f ec t changes in the phys i ca l p rope r t i e s of the t a i l i n g s as new miner-a l s are formed. The S u l l i v a n Mine i ron t a i l i n g are such waste ma te r i a l s that are subject to tremendous chemical and phys i ca l changes once exposed in the t a i l i n g s pond. In the reduced form the S u l l i v a n i ron t a i l i n g s have those c h a r a c t e r i s -t i c s t y p i c a l of most metal -mine t a i l i n g s . The weather ing of these "raw", reduced t a i l i n g s , however, r e s u l t s in the format ion of a ma te r i a l which i s d i f f e r e n t from the o r i g i n a l f r e sh mate r i a l due to the ox i da t i on of reduced i r o n - s u l f i d i c compounds. These represent 90% of the t a i l i n g s m a t e r i a l s . Ree lamat ion i s t s must the re fo re cons ider the i ron t a i l i n g s of S u l l i v a n Mine or those of s i m i l a r minera logy in two d i f f e r e n t forms 1) as the f r e sh ma te r i a l and 2) as the ox i d i zed wastes and a gradat ion somewhere in between depending on the extent of o x i d a t i o n . Even wi th o x i d a t i o n , the t a i l i n g s c o n t i n u a l l y undergo change. Th is chapter c on s i s t s of a d i s cu s s i on of the phys i ca l and chemical p rope r t i e s of the S u l l i v a n Mine i ron t a i l i n g s in both the reduced and ox i d i zed forms, and a lso d i scusses the imp l i c a t i on s of these p rope r t i e s in r e l a t i o n to rec lamat ion through vegeta t ion es tab l i shment . 2.2 S u l l i v a n Mine Reduced T a i l i n g s As noted, the S u l l i v a n Mine unox id ized (reduced) t a i l i n g s r e f l e c t the phys i ca l p r ope r t i e s c h a r a c t e r i s t i c to most t a i l i n g s as many mines have adopted s i m i l a r p rocess ing and d i sposa l methods. The S u l l i v a n i ron t a i l i n g s are g ene r a l l y ground to a s i l t loam tex tu re of 33% sand ( 2mm - 0.5 mm), 64% s i l t (0.5 mm - 0.25 mm) and 3% c l a y (<0.25 mm). They are conveyed from the - 10 -concent ra to r to the pond in wooden launders ( P l a t e 2 . 1 ) . The coarse t a i l i n g s are used to b u i l d up the dams con f i n i ng the pond and the center i s c o n t i n u a l l y f e d . The impoundment area i s u l t i m a t e l y saucer shaped, l e ve l to depress iona l in the middle and bounded by gent le s lopes along the dam. At S u l l i v a n Mine the t a i l i n g s s l u r r y i s comprised of 60-70% of water by weight (Gard iner and S t a t h e r s , 1975). This f a c i l i t a t e s g r a v i t y t r anspor t of the t a i l i n g s from the concent ra tor to the ho ld ing area . As a r e s u l t of t r anspo r t in a s l u r r y form, f l u v i a l processes are ev ident in the pond. For example, ho r i z on t a l l a ye r i ng i s common in the impoundment area as the s o l i d s s e t t l e out dur ing the depos i t i on process and become segregated accord ing to s i z e . Gene ra l l y the heav i e r , coarser p a r t i c l e s drop from the s l u r r y near the out f low and the f i n e r p a r t i c l e s are c a r r i e d out towards the depressed areas . However, i t i s not a s imple p a t t e r n . The s ide launders which ca r r y the t a i l i n g s are moved at va r i ous d i s t ance i n t e r v a l s when sec t i ons of the pond have been hea v i l y fed and new areas are r e qu i r e d . This r e s u l t s in the coa l e sc ing of fans and the over-lapp ing of d i f f e r e n t p a r t i c l e s i zed l a y e r s , fo r example, c l ays over sands. P l a t e 2.2 i l l u s t r a t e s the format ion of " a l l u v i a l fans" near the ou t l e t w i th meandering pa t te rns t y p i c a l of water-worked m a t e r i a l . M i l l i n g a lso con t r i bu te s to v a r i a t i o n . Va r i ab l e grade seams of d i f f e r -ent chemical composi t ions are mined r e qu i r i n g changes in the f ineness of g r i n d i n g . This r e s u l t s in some add i t i ons to the pond con ta in ing a h igher p ropo r t i on of f i n e s than o the r s , which again a f f e c t s the pa t te rn of se t t l emen t . The d i f f e r en ce in t ex tu re and the phenomenon of l a ye r i ng u l t i m a t e l y a f f e c t s the r a t e of dra inage and ox i da t i on in the impoundment a rea . P l a t e 2.1 View of the S u l l i v a n Mine Iron T a i l i n g s Pond w i th Wooden Launders B u i l t Around the Per imeter of the Pond. - 12 -P l a t e 2.2 Formation o f A l l u v i a l Fans Through Depos i t ion o f Reduced S u l l i v a n Mine Iron T a i l i n g s . - 13 -Consequent ly, patch iness in hydra t ion and ox i da t i on pat terns are c rea ted , i n f l u enc i ng the movement and p r e c i p i t a t i o n of s a l t s in the ox i d i z ed s t a t e . The f r e sh t a i l i n g s are a lso e a s i l y eroded by excess water d r a i n i ng from the pond f o l l o w i n g d epo s i t i o n . The po t en t i a l f o r water e ros ion from p r e c i p i t a t i o n or from excess e f f l u en t i s the r e s u l t of the r e l a t i v e l y uniform p a r t i c l e s i z e of the mate r i a l and the lack of coarse f ragments, s t r u c t u r e , o rgan i c matter and sur face cover . P a r t i c l e s that are c a r r i e d in r i v l e t s are redepos i ted in other areas of the pond and the deepening of the g u l l y s r e s u l t i n g from e r o s i on , f u r t he r d i s r up t s the ho r i z on ten ta l l a ye r i ng ( P l a t e 2 . 3 ) . There fo re , desp i t e the average s i l t loam tex tu re of the t a i l i n g s p r i o r to d e l i v e r y to the impoundment area, the p a r t i c l e s i z e d i s t r i b u t i o n of the t a i l i n g s va r i e s over the sur face and with depth . The f r e sh t a i l i n g s are sub jec t to s lumping, when wet, thereby e xp l a i n i n g the requirement of dams. The sur face of the pond cannot be manipulated f o r c u l t i v a t i o n in the f r e sh s t a t e due to the e x ce s s i v e l y low bear ing capac i t y and the t h i x o t r o p i c nature of the t a i l i n g s when wet. The unox id i zed t a i l i n g s are composed of 85% p y r r h o t i t e (FeySs) , 5% p y r i t e (FeS2) , 1% s p h a l e r i t e (ZnS) , 1% galena (PbS) , 5% quar tz (SiOg) and minor amounts of other minera l s ( c h l o r i t e , muscov i te , t r e m o l i t e , garne t , b i o t i t e , and a l b i t e ) (Gard iner and S t a t he r s , 1975). The ana l y s i s of the f r e sh t a i l i n g s i nd i c a t e they are i n f e r t i l e , as p r e d i c t e d . They are d e f i c i e n t in p lant a v a i l a b l e n i t r ogen , phosphorus, and potass ium. Organic matter i s absent and the ca t i on exchange capac i t y and nu t r i e n t ho ld ing capac i t y i s low. The t a i l i n g s are moderately to s l i g h t l y ac id (pH 6.0) and s l i g h t l y to moderately s a l i n e ( e l e c t r i c a l c o ndu c t i v i t y , 2.6 mmhos/cm) in the reduced form. Metals may be a problem in the f r e s h - 14 -P l a t e 2.3 F l u v i a l Channel ing and Gu l l y i n g i n the Ta i 1 i ngs . - 15 -t a i l i n g s as e x t r a c t ab l e manganese, i r o n , z inc and lead are very high compared to an a g r i c u l t u r a l s o i l and the p lant a v a i l a b l e mois ture ho ld ing c apac i t y i s lower than an average s o i l . Low r e s i dua l l e v e l s of the f l o a t a t i o n reagents may be found in the t a i l i n g s such as s u l f u r i c a c i d , a e r o f l a t 25, and sodium i sop ropy l xanthate (Gard iner and S t a t he r s , 1975). ( A e r o f l a t 25 cons i s t s o f 25% c r e s y l i c ac id and and 75% phosphorus p en t a su l f i d e . Phosphorus pen ta su l f i d e decomposes on contact w i th water to form hydrogen s u l f i d e [Merk and Co . , I960] . ) A summary of the chemical and phys i ca l p rope r t i e s of the t a i l i n g s (both reduced and ox i d i z ed ) i s presented in Table 2 . 1 . To produce t h i s t a b l e 75 samples were c o l l e c t e d at the 0-10 cm depth on a 200 m i n t e r v a l g r i d (Gard iner and S t a t he r s , 1975). The p a r t i c l e s i z e ana l y s i s and the f i e l d c apa c i t y data of the ox i d i z ed t a i l i n g s were c a r r i e d out on the uncemented f i n e s . 2.3 Ox id i zed Iron T a i l i n g s As a l ready desc r i bed , the S u l l i v a n Mine i r on t a i l i n g s con ta in 90% reduced i ron s u l f i d e minera l s which reac t with oxygen and moisture producing s u l f u r i c a c i d . I n i t i a t i o n of the r eac t i on occurs as soon as the sur face of the f r e sh t a i l i n g s i s s u f f i c i e n t l y hydrated ( to f i e l d c apac i t y or l e s s ) a l l ow ing exposure of the minera l s to a i r . I n ve s t i g a t i on s in to the types of ac id r eac t i ons which occur in the S u l l i v a n t a i l i n g s are l im i t e d as most research has been o r i en ted towards dec iphe r i ng the i o n i c forms and mechanisms in p y r i t e ac id p roduc t i on . - 16 -Table 2.1 Chemical and Phys i ca l P r ope r t i e s of I ron T a i l i n g s in Ox id ized and Unox id ized S ta tes * P roper ty Colour Texture % Sand % S i l t % C lay F i e l d Capac i t y (1/3 atm) Permanent W i l t i n g Po int (15 atm) PH Exchange A c i d i t y A c t i v e A c i d i t y Res idua l A c i d i t y To ta l Sulphur CEC Exchangeable Ca(NH40Ac) Exchangeable Mg(NH40Ac) EC Water So lub le Ca Water So lub le Mg Water So lub le Ci~ SAR Sa tu ra t i on % Ex t r a c t ab l e Fe(NH40Ac) E x t r a c t ab l e Mn(CaCl2) E x t r a c t ab l e A l (CaC l2) E x t r a c t ab l e Zn(HCl) E x t r a c t ab l e Pb(HCl) Unox id ized Iron Ox id i zed Iron Uni ts T a i l i n g s T a i l i n g s Munsel l g ray -b lack 5Y3/1 orange-brown 10YR5/6 s i l t loam s i l t loam %(wt) 33 20 %(wt) . 6 4 59 %(wt) 3 21 %(wt) 12 29 %(wt) <1 10 6.0 2.2 meg/100 gm 3.0 572 lb /1 ,000 tons 4,050 512,500 tons/1,000 tons 1,121 178 % 34.0 7.3 meg/100 gm 1.1 5.1 meg/100 gm 7.0 4.8 meg/100 gm 1.4 1.5 mmhos/cm 2.6 18 meg/1 703 404 meg/1 170 247 meg/1 675 10 0.23 0.23 % 27 54 ppm 2,050 9,363 ppm 42 154 ppm <2 90 ppm 625 111 ppm 4,400 68 . * Gard iner , R.T. and J . E . S ta the r s , 1975. Mined - Land Reclamat ion Research at Cominco L t d . S u l l i v a n Opera t i ons , K imber ley, B.C. Progress Report 1975. Cominco L t d . T r a i l , B.C. ( P y r i t e i s the dominant i ron s u l f i d e minera l in coal s p o i l , the waste on which most of t h i s type of research has been concent ra ted . ) As a l ready noted the i ron t a i l i n g s conta in 5% p y r i t e (FeS2) and 85% p y r r h o t i t e ( F e y S s ) . However, p y r r h o t i t e i s h i gh l y r e a c t i v e , approx imate ly 81 t imes more than p y r i t e ( M i c h e i u t t i , 1974) and the re fo re is cons idered the dominant ac id producer in the S u l l i v a n i ron t a i l i n g s . M i c h e l u t t i d i scussed the mechanisms of ac id product ion in metal i f e rous t a i l i n g s , which is app l i c ab l e to the S u l l i v a n s i t u a t i o n : (1) Fe(S04)3 + FeS 2 + H 20 _ > 3 FeS04 + 2 S (2) S + 3 0 + H 20 _ > H 2 S0 4 He does not s t a t e whether ox i da t i on occurs chemica l l y or b i o l o g i c a l l y as both routes are p o s s i b l e . B i o l o g i c a l processes are a d i s t i n c t p o s s i b i l i t y in the S u l l i v a n i ron t a i l i n g s as Robbins (1979) found, in h i s s tud ies of t h i s m a t e r i a l , the presence of the b a c t e r i a Thiobaci11 us  f e r r oox i d an s , T. t h i opa ru s , T. neapo l i tanus and T. t h i oox i dans , a l l of which o x i d i z e reduced s u l f u r compounds. The l a t t e r three spec ies vary in t h e i r t o l e r an ce to ac id cond i t i ons and are cons idered to i n d i c a t e b a c t e r i a l success ion (Robbins, 1979). For i n s tance , T. th i opa rus are t o l e r an t to pH4, T. neapo l i tanus to pH3.3 and 1\_ th ioox idans to pH1.9 (Robbins, 1979). T h i o b a c i l l u s f e r roox idans i s deemed the most important s u l f u r o x i d i z i n g bac te r ium. It i s unique, ob ta i n i ng i t s energy f o r growth from the ox i da t i on of reduced fe r rous i r o n , as we l l as s u l f u r compounds. During the ox i da t i on process i t i s attached to the s u l f u r compounds and d i r e c t l y o x i d i z e s the i n s o l ub l e s u l f i d e s producing s u l f u r i c ac id (Duncan and Walden, 1975). - 18 -Duncan and Walden be l i e ve that the s u l f i d e ion i s at tacked by an enzyme con ta in ing a s u l f h yd r y l group r e s u l t i n g in the bu i l d -up of a p o l y s u l f i d e cha i n . Accord ing to t h e i r r epo r t , the s u l f u r atoms are u l t i m a t e l y ox id i zed to the s u l f a t e i on , which is re leased in to s o l u t i o n . They o f f e r an example of m i c r ob i a l ac id product ion us ing p y r i t e : 4 FeS 2 + 15 0 2 + 14 H 20 —> 4 Fe (0H) 3 + 8 H 2 S0 4 (1) This r ea c t i on requ i res the ox i da t i on of f e r rous i ron (Fe + 2) to f e r r i c i r on ( F e 3 + ) . S inger and Stumm (1970) have found that the ox i da t i on of the i ron may be represented by the f o l l ow i ng r eac t i on sequence using p y r i t e : I n i t i a t o r r e a c t i o n : F eS 2 ( s ) ( + 0 2 ) _ > F e 2 + + s - compound (2) Propagat ion c y c l e : . > F e 2 + + 0 2 ( aq ) + S - compound (3) F e 3 + F eS 2 ( s ) _ > F e 2 + + S 0 4 " 2 (4) Iron in the F e 2 + form is re leased in the i n i t i a t o r r ea c t i on e i t he r by s imple d i s s o c i a t i o n of i ron p y r i t e or by ox i da t i on of the p y r i t e by oxygen. A f t e r the sequence has been i n i t i a t e d , a c y c l e i s e s tab l i shed in which Fe2 + i s o x i d i z ed by oxygen to F e 3 + . Iron in the Fe3 + form is subsequent ly reduced by p y r i t e , thereby generat ing add i t i o na l F e 2 + and a c i d i t y . Accord ing to S inger and Stumm m i c rob i a l involvement acce le ra tes the r eac t i on by a f a c t o r l a rge r than 10&. In the r eac t i on s given by Duncan and Walden, one of the f i n a l products of m i c rob i a l o x i da t i on is bas i c f e r r i c hydrox ide . However they propose tha t i t is u n l i k e l y that a l l of the i ron i s p r e c i p i t a t e d as t h i s compound. I t may form ins tead other m inera l s such as j a r o s i t e , a bas i c f e r r i c s u l f a t e . The f o l l ow i ng equat ion desc r ibes i t s fo rmat ion: | J a r o s i t e — | 6 FeS 2 + 22 1/2 0 2 + 15 H 20 _ > 2 H F e 3 ( S 0 4 ) 2 ( 0 H ) 6 + 8 H 2 S0 4 J a r o s i t e i s a minera l commonly formed in ac id s u l f a t e s o i l s f o l l ow i ng the i n i t i a l r i p e n i n g , o x i da t i on and a c i d i f i c a t i o n of s u l f i d e s (Pons, 1972). I t s presence i s i nd i ca ted by pa le ye l l ow mott les which l i n e and f o l l ow cracks and root channe ls . These are apertures to under l y ing reduced s u l f i d e s such as p y r i t e . As the S u l l i v a n i ron t a i l i n g s have c h a r a c t e r i s t i c s s i m i l a r to ac id s u l f a t e s o i l s i t is l i k e l y that t h i s minera l can be formed. Robbins (1979) noted such ye l l ow mott les in the S u l l i v a n i ron t a i l i n g s and by X - ray d i f f r a c t i o n found that j a r o s i t e was present in t h i s mine waste m a t e r i a l . The presence of other metals such as copper, z i n c , and n i c ke l may a lso be r e spons i b l e f o r ac id product ion in the S u l l i v a n t a i l i n g s . I f c ha l co -p y r i t e (CuFeS 2) i s present i t can be ox i d i zed accord ing to the f o l l ow i ng r e a c t i o n (Duncan and Walden, 1975): 2 CuFeS 2+ 8 1/2 0 2+ 5H 20—>2 CuS0 4 + 2 Fe (0H) 3 + 2 H 2 S0 4 or 6 CuFeS 2 + 25 1/2 0 2+ 9 H 20—>6 CuS0 4 + 2 H F e 3 ( S 0 4 ) 2 ( 0 H ) 6 + 2 H 2 S0 4 - 20 -M i l l e r i t e (NiS) and s p h a l e r i t e (ZnS) which may be present in the S u l l i v a n t a i l i n g s can a lso be ox id i zed to t h e i r corresponding s u l f a t e s . The ox i da t i on of these two s u l f i d e s does not r e s u l t in the format ion of f r ee ac ids but they do have an ac id pH and must be neu t r a l i z ed to reduce heavy metal m o b i l i t y (Duncan and Walden, 1975). Many other products may be present in the S u l l i v a n Mine ox id i zed i ron t a i l i n g s due to chemical r eac t i ons occu r r i ng in the waste. Hawley (1972) prov ides a l i s t of p o t en t i a l compounds r e s u l t i n g from the ox i da t i on of va r i ous s u l f i d e s (Table 2 . 2 ) . The r eac t i on of the S u l l i v a n i ron t a i l i n g s decreases from pH6 to pH2.2 wi th ox i da t i on of the reduced m ine ra l s . A pH of 6.5. i s cons idered optimum f o r most p lant s pe c i e s . Even the gene ra l l y ac id t o l e r a n t spec ies such as pine cannot su rv i ve at l e v e l s o c cu r r i ng in the ox i d i zed t a i l i n g s . For example, PI ass (1974) p lanted seven d i f f e r e n t pine spec ies on ac id s p o i l . Su r v i v a l was poor at pH va lues below 3 .8 . Berg and Vogel (1968) found, in t h e i r r e sea r ch , that legumes gene ra l l y su f fe red below pH4. Although some spec ies su rv i ved at pH4, poor nodu la t ion occurred below pH4.5, thus e l im i n a t i n g the s e l f - s u s t a i n i n g po t en t i a l of legumes. Bennet (1973) found that b r i s t l e y b lack locus t (Robina h i s p i d a L.) su rv i ved at pH3.5. In f i e l d i n v e s t i g a t i o n s at S u l l i v a n Mine, the s u r v i v a l ra te of arnot b r i s t l y l ocus t p lanted on the ox i d i z ed i ron t a i l i n g s was zero percent (Gard iner and S t a t he r s , 1974). There fore , the ac id l e ve l s c h a r a c t e r i s t i c of the ox i d i z ed i r on t a i l i n g s are de l e t e r i ou s to most p l a n t s . - 21 -Table 2.2 A l t e r a t i o n Products of S u l f i d i c M ine ra l s M inera l A l t e r a t i o n Products p y r r h o t i t e ( F eyS s ) l imon i t e (Fe203.nH20) s i d e r i t e (FeCC^) i ron s u l f a t e s p y r i t e (FeS2) l imon i t e (Fe203.nH20) i ron s u l f a t e s s p h a l e r i t e (ZnS) g o s l a r i t e (ZnS04.7 H2O) hemimorphite (H2O.2 ZnO) sm i thson i te (ZnC03) galena (PbS) c e r u s s i t e (PbC03) ang l e s i t e (PbS04) pyrmorphite {Pb4(Pb,C l ) (P04)3 mimet i te ( Pb 4 ( Pb ,C l )(AsfJ4)3 phosgenite (PbC03.PbCl 2 ) co tunn i t e (PbCl2) - 22 -The ox i da t i on and a c i d i f i c a t i o n of the i ron t a i l i n g s is accompanied by the format ion of s a l t s . P l a t e 2.4 dep i c t s the i n i t i a l stages of o x i d a t i on and P l a t e 2.5 represents a more extreme stage of o x i d a t i o n . Excess ive amounts of s a l t accumulate on the S u l l i v a n t a i l i n g s pond coat ing the sur face and cracks where evaporat ion i s g r ea t e s t . E l e c t r i c a l c o n d u c t i v i t i e s inc rease from 2.6 mmhos/cm in the reduced t a i l i n g s to 18 mmhos/cm in the ox i d i z ed form (Gardiner and S t a t he r s , 1975). Condu c t i v i t i e s greater than 4 mmhos/cm are cons idered de l e t e r i ou s to most p l a n t s . The spec ies of s a l t s in the S u l l i v a n ox i d i zed i ron t a i l i n g s are some of those i ron s u l f a t e s a l ready mentioned which r e s u l t from the ox i da t i on of the reduced i ron s u l f i d e s , as we l l as other fe r rous s a l t s . The i ron s a l t s are a l so con t i nuous l y drawn up by c a p i l l a r y ac t i on from the under ly ing reduced t a i l i n g s to the sur face where they are p r e c i p i t a t e d . Add i t i o na l s a l t s are produced as ac ids breakdown the minera l s p resent , r e l e a s i ng metals such as copper, l e ad , z i n c , aluminum, and manganese. These metals u l t i m a t e l y e x i s t in t h e i r r e spec t i v e s u l f a t e s a l t fo rm. ( S t r u t h e r s , 1964). The ox i da t i on of the S u l l i v a n i ron t a i l i n g s changes the a v a i l a b i l i t y of the meta ls present depending on the s o l u b i l i t y of the new produc ts . For example, e x t r a c t ab l e lead and z inc decreases w i th o x i d a t i o n . E x t r a c t ab l e manganese, aluminum and i ron increases wi th o x i d a t i o n . In the S u l l i v a n t a i l i n g s , i ron increases from 2,050 ppm in the reduced form to 9,363 ppm in the ox i d i zed s t a t e . Manganese increases from 42 ppm to 154 ppm and aluminum from less than 2 ppm to 90 ppm (Gardiner and S t a t h e r s , 1975). F a i l u r e of vege ta t i on estab l i shment on the S u l l i v a n ox i d i z ed i r on t a i l i n g s is probably due to t o x i c concent ra t ions of the metals present as we l l as to the ac id and s a l i n e p r o p e r t i e s . Accord ing t o Smith and Bradshaw - 23 -P la te 2.4 I n i t i a l Stages of Ox ida t ion o f Iron T a i l i n g s Showing Crack ing o f the Sur face and S a l t C rus t Format ion. P l a t e 2.5 Advanced Stages o f Ox ida t ion w i th S a l t Crus t Formation and Water Ponded on the Sur face D i s co l o red by Ox id i zed Iron Compounds. - 24 -(1972), in an average s o i l , l e v e l s of heavy metals in excess of 500 ppm are t o x i c to v ege t a t i o n . The Montana Department of S ta te Lands (1977) has pub l i shed suspect l e v e l s of meta l s . The i r exper iences with heavy metals suggest tha t 8 ppm boron, 0 .1-1 ppm cadmium, 40 ppm copper, 10-20 ppm lead (depending on pH), 60 ppm manganese, 400-600 ppm mercury, 0.3 ppm molydenum, 1 ppm n i c ke l and 40 ppm z i n c are at the suspect l e v e l . A suspect l eve l f o r i ron i s not def ined because t h i s metal i s a chemical antagonis t to var ious other p o t e n t i a l l y t o x i c t r a ce elements (Dept. of S ta te Lands 1977) and because high l e v e l s of other t r ace elements depress i t . The standard f o r molybdenum is in re fe rence to animal consumption of v ege t a t i on , which may accumulate molybdenum to t o x i c l e v e l s . The Cu:Mo r a t i o in vege ta t i on i s cons idered the d i r e c t parameter to t o x i c i t y . Accord ing to Mi l tmore and Mason (1971) r a t i o s of l ess than 2.0 are assoc ia ted wi th symptoms of molybdenum induced copper d e f i c i e n c y (hypocupracemia). The p o s s i b i l i t y of hypocupracemia is r ea l on the S u l l i v a n i r on t a i l i n g s as p lan t s c o l l e c t e d from a marsh on the S u l l i v a n t a i l i n g s had Cu:Mo r a t i o s averaging 0.62 ( Lavku l i c h et a l . 1977). Al though the S u l l i v a n ox i d i z ed i ron t a i l i n g s were not analyzed f o r a l l of the elements mentioned above, the t a i l i n g s do conta in lead (68 ppm), manganese (154 ppm) and z inc (111 ppm) we l l above the s ta ted suspect l e v e l s . The adverse a f f e c t s of heavy meta l s , on p lants grown in the ox i d i zed i r on t a i l i n g s , may be d i r e c t or i n d i r e c t . For i n s tance , f r e e i ron has been found to a f f e c t f e r t i l i t y i n d i r e c t l y by f i x i n g phosphorus in to forms un-a v a i l a b l e to p l an t s (Gard iner and S t a t he r s , 1975). Smith and Bradshaw (1972) s t a t e that heavy metal t o x i c i t y causes "more or less complete i n h i b i -t i o n of root growth" . They a t t r i b u t e p lant m o r t a l i t y on heavy metal contam-25 -inated s o i l s to the s u s c e p t i b i l i t y of p lants to droughti 'ness as they lack s u f f i c i e n t root p r o l i f e r a t i o n . More d i r e c t l y , Lagerwerf f (1976) noted tha t heavy metals compete with and d i sp l a ce i ron and other ions in p lant enzyme systems, a l t e r i n g the s t e r eo s t r u c t u r e and the operat ion of the enzymes in the p l a n t ' s metabol ism. Zinc may be such a heavy metal a f f e c t i n g p lan ts d i r e c t l y . White et al • (1979) found from t h e i r s t ud i e s , that p lants subjected to excess ive concen-t r a t i o n s of z i n c , su f f e red Fe -de f i c i e n c y c h l o r o s i s . The e f f e c t of z i n c on i ron was impress i ve . Leaf i r o n , at pH5 decreased from 260 ppm to 90 ppm as z i n c concent ra t i ons increased from zero to 524 ppm. S im i l a r r e s u l t s were found by Car te r (1977) i n h i s research of heavy metal contaminated ac id s o i l s . He found that the major cause of p lant m o r t a l i t y was r e l a t ed to z i n c as seed l ings took up i n c r e a s i n g l y more z inc from the s o i l as the concent ra-t i o n of z i n c increased in the s o i l . White et a l . (1979) noted that z i nc d id not a f f e c t seed germinat ion but p lants at the seed l i ng stage or o lder were a f fec ted by z i n c t o x i c i t e s . High z i n c concent ra t i ons a lso reduce crop y i e l d s depending on the concen t ra t i on of the me ta l . For i n s tance , White et a l . (1979) found that a z i n c add i t i on to the s o i l of 131 ppm at pH5.5 reduced soybean crop y i e l d s by 69% dry weight and a loss of 90% dry weight y i e l d occurred wi th a z i n c concen t ra t i on in the s o i l ' of 262 ppm. S im i l a r to other s t u d i e s , they r e l a t ed the decreased y i e l d s to increased uptake of z i n c and i t s t r a n s l o c a -t i o n through the p lant system. Z inc s o l u b i l i t y is s e n s i t i v e to pH changes and White et a l . (1979) found that a f o u r f o l d decrease of z i n c uptake occur -red wi th an inc rease of 1 pH u n i t , from 5.5 to 6 . 5 . - 26 -Berg and Vogel (1968) found that aluminum and manganese caused s t u n t i n g , c h l o r o s i s , and reduced y i e l d s of c e r t a i n legumes. These f a c t o r s depended on the p lant spec ies type , the pH, and the concent ra t i on of the metals in the s o i l . For example, a spec ies named Black locus t was tw ice as r e s i s t e n t to manganese t o x i c i t y as a spec ies named Korean lespedeza. Under severe c h l o r o s i s (based on 70-100 percent of the lea f sur face as c h l o r i t i c ) , y i e l d s decreased as much as 95%. The l e ve l of aluminum caus ing t o x i c i t y was l e s s than 300 ppm and of manganese, l ess than 171 ppm. . White et a l . (1979) and Ca r t e r (1977) found that manganese s i m i l a r to z i n c , was taken up in to the p lan t system. White et a l . found that p lan t manganese was s i g n i f i c a n t l y r a i s ed by s o i l manganese. S im i l a r to z i n c , p lant manganese decreased s i g n i f i c a n t l y wi th an increase in pH. ( Inc reas ing the pH from 5.5 to 6.5 decreased manganese content in p lants two-to t h r e e f o l d . ) Aluminum t o x i c i t i e s were cons idered by Berg and Vogel (1968) to be r e l a t ed to the s tun t i ng of p lant root development. However, Car ter (1977) found high concent ra t ions of aluminum in Scotch pine which he a t t r i b u t ed to the death of the Scotch pine s eed l i n g s . S i m i l a r to Smith and Bradshaw (1972), Cox (1978) found that heavy metals can a f f e c t p l an t s i n d i r e c t l y through the suppress ion of root development. He found tha t root development was poor in moderate ly contaminated s o i l s and no root development occurred in a seve re l y me ta l -contaminated s p o i l , f o r example a s p o i l con ta in i ng 2880 ppm n i c k e l , 867 ppm copper, 66 ppm z i n c , 42 ppm l ead , and 4 ppm aluminum. In summary, the spec ies and concent ra t i ons of heavy metals present in the S u l l i v a n ox i d i z ed i ron t a i l i n g s may be cons idered at l eas t p a r t i a l l y - 27 -r e s pon s i b l e , e i t h e r d i r e c t l y or i n d i r e c t l y , f o r the f a i l u r e , to date , of success fu l p lant estab l i shment on the t a i l i n g s . Other unique c h a r a c t e r i s t i c s develop in the S u l l i v a n i ron t a i l i n g s upon the exposure of the reduced t a i l i n g s to atmospheric c ond i t i o n s . For example, the ox i da t i on of the i ron s u l f i d e s at the sur face of the pond and the s imultaneous movement of d i l u t e s a l t s o l u t i o n s from the i n t e r i o r of the pond, r e s u l t s in the format ion of a fe r rug inous cap on the su r f a ce . This hard impermeable cap is developed as i ron s a l t s are ox i d i zed to i ron ox ides (Gard iner and S t a t he r s , 1975). The ox ides f unc t i on as cementing agents b ind ing the t a i l i n g s p a r t i c l e s i n t o an impervious mass. With ma tu r i t y and l a t e r a l expansion the i ron p l a t e - l i k e format ions buckel up in to domes as i s i nd i ca ted i n P l a t e 2 .6 . S a l t s o f ten accumulate on the unders ide of these domes. The cap is approx imate ly 7.5 cm t h i c k and covers over 85% of the i ron t a i l i n g s pond at S u l l i v a n (Gard iner and S t a t he r s , 1975) . The v a r i a t i o n in p a r t i c l e s i z e d i s t r i b u t i o n a f f e c t s i t s format ion across the pond. Where the t ex tu re i s dominant ly sand, water and oxygen can pe rco la te down r e a d i l y , l each ing the f e r rous s a l t s to below the su r f a ce . P r e c i p i t a t i o n then occurs where t h i s process i s impeded ( i . e . at a f i n e tex tu red l a y e r ) , and a hardpan forms at depth . The format ion of the cap i s r e l a t ed to the high concent ra t i on of i r on s u l f i d e s (90%) i n the t a i l i n g s . A cap does not form on the S u l l i v a n s i l i c e o u s t a i l i n g s which cons i s t o f 22% i ron s u l f i d e m i ne r a l s . D i f f e r e n t i a l and d i scont inuous p a r t i c l e s i z e l aye rs e x i s t i n g in the pond can in some cases r e s u l t in a sandwiching e f f e c t as ox i d i z ed l aye r s i s o l a t e a reduced l a ye r . The lower ox i d i zed l a y e r , may be sandy in nature , and i s being enr iched by l a t e r a l movement of oxygenated water or gaseous - 28 -P l a t e 2.6 Ferruginous Caps Forming Dome-Like S t ruc tu res on the Surface o f the Ox i d i z ed Iron T a i l i n g s Pond. - 29 -f l ow . This i s permi t ted by the layer becoming even tua l l y exposed to the sur face in another part of the pond or i t may, in some areas of the pond, under lay ma t e r i a l s i m i l a r in t ex tu re a l l ow ing v e r t i c a l movement of water and oxygen. The ' sandw ich ing ' e f f e c t i s seen in P l a t e 2 .7 . The black layers in the p i t p r o f i l e are the reduced t a i l i n g s . The orange co l o r s of high chroma s i g n i f y the ox i da t i on of i ron ox i des . The r a t e and depth of the ox i da t i on of the t a i l i n g s depend on the ease of movement of oxygenated water and gaseous f l ow . Though the fe r rug inous cap i s approx imate ly 7.5 cm t h i c k in the S u l l i v a n i ron t a i l i n g s pond the depth of the weather ing f r on t i s much deeper. Lavku l i ch et a l , (1975) found in the S u l l i v a n t a i l i n g s pond, reduced t a i l i n g s and a water t ab l e at 46 cm and in other p i t s t h i s occurred 28 cm. (The v a r i a t i o n in depth of the o x i d i z ed f r on t i s v i s u a l l y port rayed in three d ra f ted p i t p r o f i l e s with t h e i r d e s c r i p t i o n s in Appendix 2.) The redd ish brown co lo r of hydrated i ron ox ides can extend much deeper than 46 cm in other s i t u a t i o n s . M i c h e l u t t i (1974) noted depths of the weathered zone in s i m i l a r t a i l i n g s , high in i ron s u l f i d e m ine r a l s , rang ing from 2.5 cm to 1.5 m. James and Morst (1965) took cores of s l ime dams composed of s u l f i d i c minera l s and found ox i da t i on of s u l f i d e s was gene ra l l y conf ined to about 2 m wi th maximum a c i d i t y occu r r i ng at rough ly 30 cm below the su r f a ce . Von Demfange and Warner (1975) were i n t e r e s t ed in how deep to bury p y r i t i c wastes to i n h i b i t ac id p roduc t i on . They c a r r i e d out s u l f u r ana l y s i s in order to ob ta in the depth of movement. They found tha t s u l f i d e concent ra t i ons increased d r ama t i c a l l y with depth below 70 cm, even a f t e r 16 years of o x i da t i on and s u l f a t e decreased p r opo r t i o na t e l y with depth. This i nd i ca ted the depth of o x i d a t i o n . They a lso est imated that over 90% of the s u l f i d e s to 70 cm were o x i d i z e d . - 30 -P l a t e 2.7 P r o f i l e o f Ox id i zed Iron T a i l i n g s Showing Discont inuous Hor izons w i th Va r i a t i on i n S t r u c t u r e , Texture and Degree of Weather ing w i th Depth. - 31 -These t rends are s i m i l a r to these occu r r i ng in ac id s u l f a t e s o i l s where accord ing to Pons (1972) r i pen i ng remains sha l low and s o i l development tends to proceed spasmod ica l l y towards a f r o n t . The uppermost part of the p r o f i l e becomes s t r ong l y weathered and a c i d i f i e d wh i le the subso i l remains reduced. The most important aspect of t h i s "depth" d i s cus s i on i s that ox i da t i on is dominant ly a sur face phenomenon. There fore , the eng ineer ing p rope r t i e s of the pond become important . With the i n t e r i o r of the pond saturated and in a reduced c ond i t i o n , the bear ing capac i t y of the pond is low desp i te sur face c rus t f o rmat i on . Thus, the use of heavy equipment on the pond may be p r oh i b i t ed due to t h i s f a c t o r . In add i t i on to the chemical and phys i ca l p rope r t i e s d i s cussed , the S u l l i v a n Mine ox i d i z ed i ron t a i l i n g s are a lso capable of spontaneous combust ion. M i c h e l u t t i (1974) d i scussed the r eac t i on s in p y r r h o t i t e -con ta i n i ng wastes which r e s u l t s . in s u l f i d e f i r e s . The combustion occurs from the ox i da t i on of p y r r h o t i t e which produces s u l f u r d i o x i d e . 3 FeX + 5 0 2 —> F e 3 0 4 + 3 S0 2 + 9 x 10 2 K. c a l . K g " 1 (1.9 x 10-3 K. c a l . I 0 " 1 ) Accord ing to M i c h e l u t t i the heat produced by the ox i da t i on of p y r r h o t i t e would be s u f f i c i e n t to prevent the growth of any vege t a t i on . - 32 -3.0 L i t e r a t u r e Review of Var ious Approaches to the Reclamat ion of A c i d - and Metal-Contaminated Mine Wastes 3.1 I n t r oduc t i on As p r e v i o u s l y noted, the S u l l i v a n Mine i ron t a i l i n g s pose se r ious problems to r e h a b i l i t a t i o n . Standard rec lamat ion techniques are i n a p p l i c a -b l e to the t a i l i n g s due to t h e i r unique p rope r t i e s which adverse ly a f f ec t the estab l i shment and sustainment of vege ta t i on seeded on them. Many approaches have been taken in the rec lamat ion of mine waste ma te r i a l s which are s i m i l a r in some aspect to the S u l l i v a n Mine i ron t a i l i n g s . These approaches may be usefu l in dec id ing on a rec lamat ion plan f o r the S u l l i v a n t a i l i n g s . A rev iew of these research s tud ies and techniques is presented in t h i s chap te r . This in fo rmat ion u l t i m a t e l y i s analyzed and eva luated on ly i n terms of i t s a pp l i c a t i o n to the S u l l i v a n s i t u a t i o n and i s use fu l in bu i l d i n g the argument f o r the rec lamat ion approach adopted in t h i s exper iment. 3.2 Approaches t o Reclamat ion The p rope r t i e s most de l e t e r i ou s to vegeta t ion seeded on the S u l l i v a n Mine i r on t a i l i n g s are r e l a t ed to the presence of s u l f i d e s and heavy meta l s . As p r e v i ou s l y noted, the s u l f i d e s once exposed to moisture and the atmosphere produce s u l f u r i c a c i d . The heavy metals present in the mine waste gene ra l l y become more so lub l e in the r e s u l t i n g ac id environment and i f present in high concen t r a t i on s , may be t o x i c to v ege t a t i o n . The metals a l so p r e c i p i t a t e as s a l t s c r ea t i ng a s a l i n e environment. - 33 -Although the S u l l i v a n Mine ox i d i zed i ron t a i l i n g s are cha rac t e r i z ed by extreme a c i d i t y and s a l i n i t y , these t a i l i n g s are a lso cha ra c t e r i z ed by a d d i t i o n a l , r a the r unique p rope r t i e s such as hardpan format ion and the po t en t i a l f o r spontaneous combust ion. Informat ion on techniques employed in the rec lamat ion of ma te r i a l s cha rac t e r i z ed by these l a t t e r p rope r t i e s has rece ived on l y modest a t t en t i on to da te . However, the de l e t e r i o u s e f f e c t s of a c i d i t y and s a l i n i t y assoc ia ted wi th the presence of s u l f i d e s are more preva lent in mine wastes and consequent ly have rece i ved more thorough i n v e s t i g a t i o n . Therefore the techniques and approaches d i scussed in t h i s chapter are r e l a t ed to ' a c i d ' mine s p o i l being o r i en ted towards ac id and s a l t product ion and heavy metal contaminat ion . Treatments f o r ac id mine s p o i l have c onven t i ona l l y d e l t wi th the problems occu r r i ng as a r e s u l t of o x i d a t i o n . ' They have ranged from the use of a c i d - t o l e r a n t spec ies to l im i ng , l e a ch i ng , f l o od i ng and cover ing the s p o i l . Most of the rec lamat ion work has invo lved a combinat ion of d i f f e r e n t t e chn iques . However, r a the r than l im i n g , l e a ch i ng , f l o od i ng e t c . some rec lamat ion programs have been ori.ented towards prevent ing the i n i t i a l o x i da t i on of s u l f i d e s . By t h i s , ac id product ion and the accompanying t o x i c e f f e c t s would be e l im i n a t e d . This approach inc ludes the use of b a c t e r i a to prevent o x i da t i on (as d i scussed in sec t i on 3.2.5) and bury ing reduced s u l f i d e s (as d i scussed in s e c t i on 3.2 .6 ) . The rec lamat ion of ac id mine s p o i l i s the re fo re d i scussed both from the s tandpo int of r e c l a im ing mate r i a l in which the s u l f i d e s have been ox i d i z ed and in r e c l a im i ng mine waste ma te r i a l s wi th techniques o r i en ted at p revent ing the ox i da t i on of the reduced s u l f u r compounds. - 34 -3.2.1 Ac id and Heavy Metal To l e ran t P l an t Spec ies Ac id t o l e r a n t spec ies may be one s o l u t i o n to vegeta t ing ac id mine spo i l d i r e c t l y w i thout the use of f u r t h e r amendments except f o r f e r t i l i z e r s . S tud ies have been c a r r i e d out in attempts to f i n d methods to p r ed i c t t o l e rances in p lan ts and spec ies that are t o l e r a n t . Ac id t o l e rance may be the c en t r a l f a c t o r of the research but more of ten these s tud ies are t i e d to r e s i s t an ce to heavy meta l s , which are gene r a l l y more so l ub l e at the low pH l e v e l s common in a c i d i c mine wastes. The ca rd i na l po int in t h i s area of research has been that some spec ies of p lan ts are equipped wi th an inherent t o l e r ance to p a r t i c u l a r adverse c ond i t i o n s . With t h i s in mind, Vogel and Berg (1968) attempted to set up a grass -legume t o l e r ance l i s t based on the r e s u l t s of greenhouse and f i e l d s t u d i e s . The i r p ro j e c t t e s ted growth aga inst pH using agronomic spec ies seeded on va r i ous mine s p o i l m a t e r i a l s . They found that some spec ies appeared to be more t o l e r a n t to the adverse cond i t i ons than others but none of the grasses su rv i ved below pH4 and nodu la t ion by legumes gene ra l l y d id not occur below pH4.5. The i r study was success fu l in d e l i n e a t i n g the more and less t o l e r a n t spec ies of grasses and legumes but on ly above pH4 w i th no success at pH2, the l e ve l c h a r a c t e r i s t i c of the S u l l i v a n Mine ox id i zed i ron t a i l i n g s . Gadg i l (1968) approached the problem more from a l abo ra to ry study. She designed a d r i p c u l t u r e apparatus which subjects seed l ing roots to va r i ous meta l -contaminated s o l u t i o n s . By es t imat ing the d i f f e r en ce in root e l onga t i on and by i n co rpo ra t i ng t h i s in fo rmat ion in to an index to t o l e r ance equa t ion , she set up a t ab l e of tes ted spec i e s , grouped accord ing to t h e i r t o l e r an ce index. This technique may be usefu l in more c l o s e l y s e l e c t i n g 35 -p lan t s which are s p e c i f i c a l l y adjusted to p a r t i c u l a r types and l e v e l s of metal contaminat ion in mine wastes. Cox 's s tud i e s (1978, 1979), which approached the t o l e r an t spec ies problem from a d i f f e r e n t pe r spec t i v e , suggest a r ea l p o t en t i a l f o r the i d e n t i f i c a t i o n and use of t o l e r a n t spec ies in r e c l ama t i on . His study invo lved t r a n s l o c a t i n g seeds from uncontaminated s o i l s and me ta l -contaminated ac id s p o i l . He p lanted the seeds on both contaminated and uncontaminated s o i l s . He tes ted seed l ing germina t ion , seed l ing s u r v i v a l and f i n a l l y he used a to l e rance index to p inpo in t the metals to which the p lants had adapted. His s tud ies p r i m a r i l y i nd i c a t e tha t t o l e rance to a c i d i t y and heavy metals i s as much a product of the p lan t s environment as to na tu ra l r e s i s t a n c e in se l ec ted spe c i e s . He found that seeds of a p lants spec ies b u i l d up to l e rances and become best adapted to the s po i l on which they are s u r v i v i n g . A l so very important , h i s data i nd i c a t e s that t o l e r ance in p l an t s evo lves on ly to the l eve l requ i red f o r s u r v i v a l of the p l a n t . This suggests that evolvement of t o l e r ance i s s i t e s p e c i f i c and not spec ies s p e c i f i c . In h i s germinat ion versus su r v i v a l ' t e s t t h i s i s conf i rmed. For example, 80% o f the seed o r i g i n a t i n g from noncontaminated s po i l germinated on a l l s p o i l s , contaminated or not . However, on ly 20% of t h i s seed surv ived on the contaminated wastes . He found that on l y 50% of the seed o r i g i n a t i n g from the contaminated s p o i l was v i a b l e , but 80% o f t h i s seed surv ived on i t s r e spec t i v e contaminated s p o i l . However on l y 56% of these seeds surv ived on noncontaminated s p o i l and 2% surv i ved on a more seve re l y contaminated mine waste. Therefore not on l y was the seed best adapted to i t s o r i g i n a l - 36 -environment, i t was adapted on ly to the l eve l r equ i r ed . What Cox termed "the f i x a t i o n of t o l e r an t gene complexes" had occur red . The index to to l e rance equat ion i nd i ca ted the seeds of the grass tes ted (Deschampsia e sp i t o s ) by Cox had developed a t o l e r ance f o r copper and n i c k e l . For i n s tance , the seed had a to l e rance index of 90% f o r copper and 110% f o r n i c k e l . These va lues are high compared to the average seed which had a t o l e r ance index of 10% f o r both copper and n i c k e l . (To lerance to aluminum, lead and z inc were l ess obv ious . ) Cox's study, t h e r e f o r e , i s a l so important in i l l u s t r a t i n g the v a l i d i t y of u t i l i z i n g the to l e rance index in these types of s t ud i e s . Smith and Bradshaw (1972) a l so examined evolvement of to l e rances to .metals and ac ids based on the adaptat ion of a p lant to i t s environment. The i r r e s u l t s v i r t u a l l y agree with Cox's except that in t h e i r study the adapted seeds of a spec ies d i d not n e c e s s a r i l y produce the h ighest y i e l d s on i t s host s o i l . Kuja and Hutchinson (1978) were a lso search ing f o r adapted p lan ts f o r rec lamat ion purposes. They c o l l e c t e d p lants from the Smoking H i l l s area of Cape Ba thurs t , N.W.T. The s o i l environment in the Smoking H i l l s reg ion i s ac id r e s u l t i n g from i n t en s i v e s u l f u r d i ox i de fumigat ions produced by spontaneous combustion (of bituminous s h a l e ) . Th is study i s r e l a t e d to the S u l l i v a n s i t u a t i o n in tha t Ku ja and Hutchinson c o l l e c t e d p l an t s from the Smoking H i l l s which were adapted to ac id pH va lues ranging from 2.0 to 3.0 - pH l e v e l s s i m i l a r to those of the S u l l i v a n ox i d i z ed i ron t a i l i n g s . When the seeds, o r i g i n a t i n g . from the Smoking H i l l s , were p lanted on ac id s po i l high in heavy meta l s , they d id not s u r v i v e . This is a t t r i b u t ed to the f a c t heavy metals are not c h a r a c t e r i s t i c - 37 -of the Smoking H i l l s ' s o i l environment and the re fo re the p lan ts were not t o l e r a n t to high concent ra t ions of heavy meta l s . This suggests that pH i s not n e c e s s a r i l y the parameter to use in judg ing the po t en t i a l fo r s u r v i v a l of spec ies of p l an t s on a c i d i c t a i l i n g s . It i s the concent ra t ions and types of metals which a lso a f f e c t the s u r v i v a l of a p lant and the re fo re must be cons ide red . From these s tud ies i t is ev ident that natura l t o l e rance in p lants to ac ids and metals i s not s ub s t an t i a l to a l low the repu tab ly t o l e r a n t spec ies to w i ths tand the cond i t i ons of mine t a i l i n g s such as those at S u l l i v a n Mine. I t i s a l so ev ident that p lan t spec ies growing on a contaminated ma te r i a l are more r e l i a b l y t o l e r a n t . They o f f e r more encouragement in an e f f o r t to f i n d spec ies which can be used s u c c e s s f u l l y in the rec lamat ion of metal mine t a i l i n g s . 3.2.2 L iming L iming i s perhaps the most common method used in the ame l i o ra t i on of ac id mine wastes . Liming has two mutua l l y b e n e f i c i a l a t t r i b u t e s . It r a i s e s the pH of the mate r i a l to a l e ve l which can support v ege t a t i on . I t a lso reduces the s o l u b i l i t y of most meta l s , which may be present in the mine wastes, to a concent ra t i on which is not t o x i c to the p lants growing on the contaminated m a t e r i a l s . Most l im ing treatments i nc lude the use of f e r t i l i z e r . The success of the l im ing treatment in rec lamat ion of ac id mine wastes has been a t t r i b u t e d to many f a c t o r s . For instance So r r e l 1 (1974) who limed s p e c i f i c a l l y to r a i s e the pH of ac id mine wastes, a t t r i b u t ed the success of h i s rec lamat ion program to maximum inco rpo ra t i on of the l imes tone , proper grad ing and dra inage c o n t r o l , and the use of drought- and a c i d - t o l e r a n t - 38 -spec i e s . This study suggests that proper management and techniques must accompany the l im ing t rea tment . M i c h e l u t t i (1974) a l so recognized the importance of proper i n co rpo ra -t i o n of the l im ing ma te r i a l s f o r success fu l r e c l ama t i on . He tes ted t h i s by app ly ing l imestone with v a r i a b l e degrees of coarseness to determine the most e f f e c t i v e p a r t i c l e s i z e f o r optimum s o l u b i l i z a t i o n of l imes tone . He used 112 tonnes/hec ta re (50 tons /ac re ) of coarse l imestone (80% + 10 mesh) compared to a f i n e r grade (60% - 100 mesh) normal ly used. A f t e r 30 days the p l o t t r ea ted wi th the f i n e r s i z e l imestone had good growth of p l a n t s . Even a f t e r 6 months no growth of p l an t s occurred on the p l o t wi th the coarse s i z e 1imestone. M i c h e l l u t t i a l so found that the length of s u r v i v a l of p l an t s was d i r e c t l y r e l a t e d to the amount of l imestone app l ied to the ac id waste. Watkin (1975) a lso found that the more l imestone added to the ac id t a i l i n g s in h i s s tudy, the greater were the y i e l d s ob ta ined . He l imed at 11 ( 5 ) , 22 (10 ) , 34 (15 ) , 67 (30) and 134 tonnes/hectare (60 t o n s / a c r e ) . The best growth occurred at the ra te of 134 tonnes /hec ta re . However, Watkin was not encouraged by these r e s u l t s . A f t e r 3 yea r s , the on ly success fu l es tab-l ishment of vegeta t ion occurred on p l o t s on which ra tes of 67 and 134 tonnes of l imestone had been app l i e d . This conf irmed that high amounts of l imes -tone were e s s en t i a l f o r the rec lamat ion of ac id -genera t ing mine wastes. Ac i d -gene ra t i ng wastes are those which conta in high concent ra t ions of s u l f i d e s . As the sur face i s n eu t r a l i z e d by l im i n g , more ac ids are con t inuous l y being produced as oxygen moves down in to the i n t e r i o r of the pond to o x i d i z e these reduced compounds. - 39 -Techniques for p r ed i c t i n g ac id generat ion po t en t i a l have been developed by Duncan and Walden (1975) and Berg et a l . (1968). These t e s t s have been found to be usefu l in ac id s po i l l im ing recommendations. The method developed by Duncan and Walden i s based on the dete rminat ion of t o t a l s u l f u r content of the sample and the t i t r a t i o n of ac id consuming p o t e n t i a l . By comparing the ac id producing c a p a b i l i t y and the ac id consump-t i o n , an est imate of the po t en t i a l f o r excess ac id product ion i s ob ta ined . Duncan's and Walden's procedure was developed fo r the spo i l sample as we l l as s p o i l water. Berg et a l . (1973) on ly used a t i t r a t i o n method on s p o i l water to est imate extreme ac id p o t e n t i a l . They found that the t i t r a t i o n method underest imated the amount of l ime requ i red on a p a r t i c u l a r ac id t a i l i n g s p o i l . They added zero , two, four and s i x t imes the equ iva len t of base requ i r ed to n e u t r a l i z e the t a i l i n g s by the t i t r a t i o n procedure. A f t e r 900 days of incubat ion the pH was s t i l l decreas ing on most of the l imed t a i l i n g s . The long per iod of 900 days of the Berg et a l . study i nd i c a t e s the extremeness of the ac id producing po t en t i a l of some s p o i l s . Not on ly has the method and amount of l im ing mate r i a l been a f a c t o r in the success of the treatment but the cho ice of l im ing mate r i a l has a lso been a f a c t o r to cons i de r . For i n s tance , M i c h e l l u t t i found that l ime in the hydrox ide form was c o r r o s i v e and had the p o t e n t i a l to produce a t o x i c a l k a l i n e cond i t i on in the ac id s po i l he was t r e a t i n g , i f the s po i l was ove r l imed . The co r ros i veness and a l k a l i n e problems d id not occur when l ime in the carbonate form (Ca CO3) was used in an ove r l im ing s i t u a t i o n . Berg et a l . (1975) a lso recognized the importance of the composi t ion of the l im ing agent in rec lamat ion of ac id wastes. They found that l im ing mate r i a l con ta in ing a 4:1 equ iva len t r a t i o of Ca:Mg caused a depress ion in - 40 -p lant y i e l d s compared to a r a t i o of 19 :1 . They a t t r i bu t ed the depress ion of y i e l d s to the accumulat ion of. so lub l e magnesium s a l t s which occurred in the high magnesium r a t i o l im ing m a t e r i a l . As p r e v i o u s l y mentioned, the success of l im ing has a lso been a t t r i b u t e d to the reduc t ion of heavy metal t o x i c i t i e s in mine s p o i l by a reduc t ion in the s o l u b i l i t i e s of the incumbent me ta l s . Such were the f i nd i ng s of Car te r et a l . (1977). They t i e d an inc rease in seed l i ng s u r v i v a l r a te to a decrease in s o l u b i l i t y of z i n c , manganese and lead brought about by l ime-e leva ted pH va l ue s . Table 3.1 i l l u s t r a t e s the e f f e c t of pH on the s u r v i v a l of two r e l a t i v e l y ac id t o l e r a n t spec ies Black Locust and Scotch P ine . Su r v i v a l f o r both spec ies increased from zero to 100% with an e l e va t i on in pH of 1.6 u n i t s , from 4.4 to 6. Table 3.2 c l e a r l y i l l u s t r a t e s the decreases in z i n c , manganese and lead concent ra t ion as a func t i on of pH f o r the same p l o t s analyzed in Table 3 . 1 . Car te r et a l . a l so found that l im ing was important , not on ly in reduc ing heavy metal s o l u b i l i t y by i nc reas ing the pH of the s o i l , but a l so in adding ca lc ium to the s o i l system. This promotes a mass ac t ion e f f e c t in which the outcome is b a s i c a l l y the d i l u t i o n of heavy metals in the s o i l by the presence of l a rge amounts of ca l c i um. They i l l u s t r a t e d t h i s by de s c r i b i ng ca l c i um ' s r o l e in the p lan t system. Calcium plays a dominant par t in ap i ca l bud development and c e l l wa l l c o n s t r u c t i o n . With t h i s in mind, they analyzed f o r ca lc ium in the p lan t t i s s u e s grown on the contaminated s p o i l . They found that the degree of c o r r e l a t i o n var ied wi th the spec ies of p lant but the t i s s u e ana l y s i s showed that percent ca l c ium was nega t i v e l y c o r r e l a t ed wi th percent z i nc in the s eed l i ng s . Such r e s u l t s e xp l a i n not on ly s u r v i v a l but growth of s eed l i ng s . - 41 -Table 3.1 The e f f e c t s of pH ( l ime l e v e l ) upon the s u r v i v a l of t r ee seed l ings grown on smel ter-contaminated s o i l s (Car ter et a l . , 1977). S o i l pH % Su rv i va l Black Locust by Species Scotch P ine 4.4 0 0 5.0 20 80 5.5 60 40 6.0 100 100 6.5 80 100 Table 3.2 Resu l t s of mean separa t ion procedures r e l a t i n g the e f f e c t s of increases s o i l pH ( l ime l e v e l ) upon e x t r a c t a b i 1 i t y o f heavy metals in a smel ter-contaminated s o i l (Car ter et a l . , 1977). S o i l pH Ex t r a c t ab l e Zn Metals Mn Means (meg/lOOg) Pb 4.4 .457 .102 .043 5.0 .403 .081 .036 5.5 .319 .080 .030 6.0 .200 .057 .028 6.5 .138 .050 .023 - 42 -From these s tud ies l im ing of ten appears to be a success fu l means of approaching the rec lamat ion of ac id mine wastes. 3 .2 .3 Leaching Leaching has been used in con junc t ion with l im ing and as a technique in the rec lamat ion of ac id mine wastes . Berg et a l . (1975) found that h igher y i e l d s were obta ined on p lo t s which has been l imed and leached as opposed to p l o t s which has on ly been l imed or had been leached f i r s t and then l imed. They a t t r i b u t e d the p o s i t i v e e f f e c t s of l each ing and l im ing toge the r , to the downward movement of s a l t s which may accumulate as a consequence of the l im i ng p rocess . James and Morst (1965) and James (1966) found that leach ing i s use fu l in the rec lamat ion of ac id mine wastes by moving ac ids down below the su r f a ce . This would make l im ing unnecessary. The success of leach ing i s based on us ing a f i n e spray. By c o n t r o l l i n g the amount of water added to the sur face in r e l a t i o n to the hyd rau l i c c ondu c t i v i t y of the spo i l m a t e r i a l , ac ids can be removed from the sur face by downward movement without the occurrence of ponding. Evaporat ion ra tes must be taken in to cons i de r a t i on as the f i n a l goal i s to move the a c i d i t y from the sur face layers to depths at which evaporat ion would not re tu rn i t to the su r f a ce . James and Mors t , and James s t i p u l a t e that t h i s technique cannot be app l ied u n t i l a l l or most of the s u l f i d e s are o x i d i z ed and thus ac id generat ion i s completed. Leaching has a lso been a technique s tud ied to remove s a l t s from the sur face of s a l t - a f f e c t e d ac id s p o i l . S t ru the r s (1964) set up a study, us ing l y s ime t e r s , to t r a ce the pat te rn of s a l t movement and s a l t product ion in severa l types of mine waste m a t e r i a l s . He inc luded s po i l con ta in ing high - 43 -concen t ra t i ons of i ron s u l f i d e s s i m i l a r to the S u l l i v a n i ron t a i l i n g s . He noted tha t p l an t es tab l i shment was more success fu l in the sp r i ng and h i s data i nd i ca t ed that the success was a t t r i b u t a b l e to lower s a l t contents at that t ime in the r oo t i ng zone. The s a l t s were leached by w in ter and e a r l y s p r i n g p r e c i p i t a t i o n . From h i s study he concluded that proper g rad ing , to encourage r a i n i n f i l t r a t i o n , and leach ing through the year are p a r t i c u l a r l y important in the rec lamat ion of s a l t a f fec ted s p o i l s . 3.2.4 F lood ing Another approach to the rec lamat ion of ac id s po i l has been f l o o d i n g . Th is would so l ve the problems of l im i ng , l e a ch i ng , heavy metal t o x i c i t i e s , e t c . However, M i c h e l l u t t i (1974) s ta tes that t h i s method could only be employed under s pe c i a l c o n d i t i o n s . Dams would have to be p rope r l y cons t ruc ted to avoid seepage and f a i l u r e . Constant mon i to r ing would a lso be r equ i r ed to ensure the pond was con t i nuous l y under water. Very l i t t l e l i t e r a t u r e e x i s t s on the f l o od i ng techn ique . King et a l . (1974), however, have c a r r i e d out s tud ies on the f a c t o r s which a f f e c t the recovery of ac id s t r i p mine l a ke s . B a s i c a l l y t h e i r s tud ies i nd i c a t e tha t the recovery of a l ake , which s imulates the f l o od i ng of a t a i l i n g s pond, may be acce le ra ted by adding la rge amounts of organ ic matter to the system. Th is would promote a reduc ing environment fo r s u l f a t e reduc ing organisms, which are necessary in the recovery of the lake to convert s u l f a t e s to s u l f i d e s . The reduc t ion of s u l f a t e s to s u l f i d e s would have a net e f f e c t of i n c reas i ng the pH of the l ake , thus p rov id ing a more hosp i t ab l e environment f o r p ioneer ing vege ta t i on . I t i s obvious that rec lamat ion of ac id t a i l i n g s by f l o o d i n g would requ i r e management and maintenance and the re fo re is not g ene r a l l y reso r ted to as a rec lamat ion procedure. - 44 -3.2.5 B a c t e r i c i d e s A b a c t e r i a l approach i s a method that has been cons idered in the rec lamat ion of ac id -genera t ing mine s p o i l . In t h i s approach, rec lamat ion i s o r i en ted at p revent ing the i n i t i a l o x i da t i on of s u l f i d e s . As noted in Chapter 2.3 m i c r ob i a l mediat ion acce le ra tes the ox i da t i on of i ron s u l f i d e s by a f a c t o r of 10^ (S inger and Stumm, 1970). S inger and Stumm be l i e ve that i f the c a t a l y t i c agent r e spons i b l e f o r ox i da t i on could be surpressed, the chemical o x i da t i on of i ron in the F e 2 + form to the Fe3 + form would be too slow to be of any consequence. They suggest the use of b a c t e r i c i d e s at a l o c a t i o n near the i n f l u en t water source, to prevent o x i d a t i o n . 3 .2 .6 Bury ing Another approach to the rec lamat ion of ac id generat ing mine spo i l has been to bury the s u l f i d e m a t e r i a l . Environmental problems from ac id mine dra inage in the U.S. have led to s t r i c t government r egu l a t i on s r e q u i r i n g tha t t h i s ma te r i a l be bu r i ed . For example, Montana's S t r i p and Underground Mine Reclamat ion Rules and Regu la t i ons : In te r im Regu la tory Program (Adm in i s t r a t i v e Rules of Montana, 1978) s t a t e s the f o l l ow i ng from sec t i on 26-2 . 10(10) - S10310(g): " . . . a c i d fo rming , t o x i c fo rm ing , combust ib le m a t e r i a l s , or any other waste ma te r i a l s i d e n t i f i e d by the Department that are exposed, used, or produced dur ing mining s h a l l be covered wi th a minimum of 2.5 m (8 f t ) of nontox ic and noncombust ible m a t e r i a l , o r , i f necessary , t r ea ted to n e u t r a l i z e t o x i c i t y in order to prevent water p o l l u t i o n and su s t a i n i ng combustion and to minimize adverse e f f e c t s on p lan t growth and land uses ac id - fo rming or t o x i c - f o rm ing mate r i a l s h a l l not be bur ied or s tored in p rox im i t y to a dra inage course so as to cause or pose a th rea t of water p o l l u t i o n . " Pennsy lvan ia has s i m i l a r laws. For Pennsy lvan ia , the ac id or t o x i c -forming s p o i l must be placed e i t h e r below the water t ab l e i f the water t ab l e does not f l u c t u a t e s u b s t a n t i a l l y or on a c l a y layer above the zone of water t a b l e f l u c t u a t i o n . In the l a t t e r case, the s po i l must be covered wi th a s o i l or s o i l - l i k e ma te r i a l (Pennsy lvan ia Department of Environmental Resources, 1976). U.S. Federa l Su r f a c i ng Min ing Reclamat ion Law (1979) r equ i r e s that a c i d - and - t o x i c forming ma te r i a l s be covered dur ing the back-f i l l i n g process wi th a minimum of 1.22 m (4 f t . ) of the best a va i l a b l e nontox ic and noncombustible m a t e r i a l . However, deep b u r i a l may not be complete ly e f f e c t i v e in i s o l a t i n g an ac id waste m a t e r i a l . P e r c o l a t i n g a i r and water and a high wa te r - t ab l e may promote ac id product ion below the su r f a ce . Th is would u l t i m a t e l y r e s u l t in ac id mine d ra inage . Pionke and Rogowski (1979) and Rogowski and Jacoby (1979) were concerned wi th t h i s p o s s i b i l i t y . In the l abo ra to r y , they attempted to model the e f f e c t s of bury ing ac id producing wastes such as those at S u l l i v a n Mine, with a non- tox i c waste, under severa l c o n d i t i o n s . - 46 -One of t h e i r s tud ies invo lved the use of t o p s o i l . They found that t o p s o i l w i th a high mois ture ho ld ing capac i t y can prevent incrementa l dewater ing of ac id s p o i l . For i n s tance , t o p s o i l p laced on coarser tex tured cover m a t e r i a l , which in turn o v e r l i e s gene ra l l y f i n e tex tu red ac id s p o i l , reduces water f low in to the cover mate r i a l due to the high moisture ho ld ing capac i t y of the t o p s o i l . The t o p s o i l would a lso tend to dens i f y , through se t t l emen t , at the topso i1 - cove r i n t e r f a ce f u r t he r reduc ing the ra te and amount of water f l ow ing through the cover m a t e r i a l . Without t o p s o i l and under sa tura ted cond i t i ons la rge amounts of water would f l ow r a p i d l y through the cover ma te r i a l as a f unc t i on of the high hyd rau l i c c o ndu c t i v i t y of the cover ing m a t e r i a l . F i ne s , in the cover ing m a t e r i a l , would be t ranspor ted through the p r o f i l e and be u l t i m a t e l y redepos i ted at the cove r -ac i d s po i l i n t e r f a c e . This would r e s u l t in a dense layer immediately above the ac id wastes. I n i t i a l l y the water content would inc rease with depth to a po int j u s t above the ac id wastes and then decrease s u b s t a n t i a l l y . This could lead to incremental dewater ing of the ac id wastes and thus ac id d ra inage . With t ime, a perched water t ab l e could bu i l d up above the ac id wastes and cause rap id d ischarge of the water t ab l e or f l u s h i n g . This would lead to ex tens ive ac id d ra inage . In the same v e i n , Pionke and Rogowski (1979) and Rogowski and Jacoby (1979) found that not on ly d id the higher water r e t e n t i v e p rope r t i e s of the t o p s o i l l i m i t the ra te and amount of water f low u l t i m a t e l y in to the ac id wastes, but a lso the ra te and amount of a i r f l ow ing to the ac id wastes. Therefore t o p s o i l , under p a r t i c u l a r c i r cumstances , may a lso reduce the o x i da t i on ra te of ac id mine wastes. - 47 -Although Rogowski and Jacoby recognized the p o s i t i v e e f f e c t s of top-s o i l i n g they a lso noted increased amounts of sediment in the leachate of the t o p so i l e d treatment in comparison to the non- topso i l ed t reatment . The imp l i c a t i on s of t h i s are impor tant . The ca rd ina l po int of bury ing the s p o i l i s an attempt to i s o l a t e i t from a i r and water f l ow . An increase in sediment i nd i c a t e s an increase in i n t e r na l p i p i n g . The movement of sediment from the sur face to depth has the po t en t i a l of t r an spo r t i ng o x i d i z i n g b a c t e r i a in to the reduced s p o i l . Pionke and Rogowski s t a te that t h i s can be avoided by using the p ip ing r a t i o accord ing to Cedergren (1967): Pr = D i 5 / D 8 5 < 5. D15 i s the 15 percentage p a r t i c l e - s i z e of the cover ma te r i a l ( f i l t e r ma t e r i a l ) and D35 is the 85 percentage p a r t i c l e s i z e of the t o p s o i l . They es t imate that the sediment increase in t h e i r experiment was due to the high s u s c e p t i b i l i t y to p ip ing (P r>5) of the t o p s o i l used. Therefore t h i s c a l c u l a t i o n may be of va lue in choosing the optimum t o p s o i l . Pionke and Rogowski a lso d i scuss the bene f i t s of submerging acid s po i l and suggest t h i s techn ique on ly when water movement in the v i c i n i t y of the ac id s po i l i s m in ima l . Under these cond i t i ons submergence more e f f e c t i v e l y sea l s o f f ac id s po i l from oxygen. The d i f f u s i o n c o e f f i c i e n t of oxygen in water i s extremely low, D = 1.8 x 10~3mm2/sec compared to 20.6 mm^/sec in atmospheric cond i t i ons (25°C) a d i f f e r en ce of about 4 orders of magnitude. However, P ionke and Rogowski note the dangers of t h i s r ou te . I f the s po i l was p a r t i a l l y o x i d i z e d , ac ids and s a l t s would move in to the ground - 48 -water system. The i n i t a l e f f e c t would be rap id u n t i l the supply of ac ids and s a l t s were exhausted. In the long term, the t o x i c drainage water would be more d i l u t e d . Therefore submergence should on ly be resor ted to i f the s u l f i d e s are v i r t u a l l y unox i d i z ed . It should be noted that reduced s p o i l would con ta in a r e s e r v o i r of oxygen, which would r e s u l t in some ac id d r a i n -age even i f the s po i l were e f f e c t i v e l y sea led o f f . However the ac id dra inage would be min ima l . I f o x i d a t i o n has proceeded beyond a reasonable l e v e l Pionke and Rogowski suggest placement of ac id s p o i l above the water t a b l e . Though t h i s would expose the ac id s po i l to more rap id oxygen d i f f u s i o n rates i t would reduce d i r e c t hyd ro log i c con tac t . The exposure to oxygen could be d imin ished somewhat by promoting set t lement in the cover ing m a t e r i a l . Sett lement r e s u l t s in a decrease in p o r o s i t y . Accord ing t o Pionke and Rogowski, the 10% decrease in volume of the non- topso i l ed treatment t r a n s l a t e d in to a 25% decrease in f l ow volume. Changing the oxygen f low path length could have a s i m i l a r e f f e c t . They s t a t e tha t cover ing ac id s po i l wi th 9 m ra the r than 3 m of mate r i a l would decrease the oxygen resupp ly ra te to approx imate ly one t h i r d of the o r i g i n a l r a t e . They use the f o l l ow i ng d i f f u s i o n equat ion to est imate t h i s : F = D 3 c/9 x where F i s the t r a n s f e r ra te of the d i f f u s i n g substance per un i t a rea , and 9c/3X i s the concen t ra t i on grad ient normal to the su r f a ce . Changing from 3 to 9 m decreases 3 c/a x by i n c reas ing 3 x . Reducing the quan t i t y of water moving through the ac id s po i l e i t h e r by making the sur face more dense or by - 49 -some other method would a lso con t ro l ac id product ion and movement in to the groundwater. F i n a l l y P ionke and Rogowski looked at the e f f e c t i v e s i z e of ac id s po i l p a r t i c l e s in r e l a t i o n to t h e i r ac id p o t e n t i a l . They were concerned on how the s i z e of the po t en t i a l ac id producing p a r t i c l e r e l a t ed to the s u l f a t e resupp ly r a t e (and s i m i l a r l y the oxygen d i f f u s i o n r a te ) i e . volume versus sur face area on a weather ing r i n d . This is best i l l u s t r a t e d by look ing at F igure 3.1 taken from t h e i r s tudy. In t h i s f i g u r e i t can be seen that the increase in p a r t i c l e s i z e g r e a t l y decreases the volume of s u l f a t e , i e . a c i d , produced. This has important imp l i c a t i o n s of p a r t i c l e s i z e cho ice i f p o s s i b l e . Pionke and Rogowski c a r r i e d out t h i s experiment on submerged ac id s p o i l . I t i s not known what p a r t i c l e s i z e range would be more b e n e f i c i a l in reduc ing ac id product ion in an unsaturated zone. It i s a lso not known whether the g r e a t l y decreased s u l f a t e d i f f u s i o n ra te would counterbalance the greater exposure of coarse p a r t i c l e s to oxygen through l a rge r channels and vo ids and increased f requency of wet t ing and d ry ing c y c l e s . I t i s obvious that some or a l l of these cons i de ra t i ons may be important in dec id i ng in the approach to deep bury ing of ac id s o i l or s p o i l . 3.2.7 Cover ing Cover ing i s a l so a method used in the rec lamat ion of ox i d i z ed ac id s p o i l . The estab l i shment of a vege ta t i ve community on overburden, t o p s o i l , or m ineso i l would serve to reduce or e l im ina t e sur face eros ion and r uno f f . P l an t s would in tervene wi th mois ture (and oxygen) movement in to the ac id - 50 -FIGURE 3.1 S u l f a t e c o n t r i b u t i n g s p o i l volume c o n t r o l l e d by d i f f u s i o n accord ing to p a r t i c l e s i z e * . * Ca l cu l a t ed f o r a c y l i n d r i c a l p a r t i c l e f o r which the top and bottom o f the c y l i n d e r i s cons idered impermeable and a d i f f u s i o n c o e f f i c i e n t o f 6 x 10~ 5 mm2/ Sec. From: H.B. Pionke and A .S . Rogowski. 1979. - 51 -s p o i l by uptake through t h e i r r oo t i ng system. The success fu l estab l i shment of a vege ta t i ve cover then would serve to i s o l a t e the acid ma te r i a l from atmospheric c ond i t i o n s . In M i s s o u r i , the s ta te laws r equ i r e that a c i d i c waste be covered w i th at l eas t 1.2 m (4 f t . ) of m ineso i l or t o p s o i l . The depth of cover ing to achieve success fu l rec lamat ion is c r u c i a l in terms of economics. Brundage (1974) s t a t e s that d i f f e r en ce in cost between 30.5 cm of cover ing (1 f t . ) and 122 cm (4 f t . ) ranges between $5,500.00 and $8,800.00 per hectare ($2,500.00 and $4,000.00 per acre) depending on the a v a i l a b i l i t y of the mate r i a l (1974 d o l l a r s ) . He was the re fo re i n te res ted in e s t a b l i s h i n g the minimum depth of s o i l r e qu i r ed . Brundage was of the op in ion tha t 122 cm (4 f t . ) of cover was extreme. He surveyed over 69 hectares (170 acres) of mine waste mate r i a l which had been depos i ted from 3 to 11 years p r e v i o u s l y . The mine waste mate r i a l was covered wi th overburden and t o p s o i l ranging in depth from less than 20.3 cm to over 91 cm. Vigorous stands of grasses and legumes were e s t ab l i shed on the cover ma te r i a l and most areas a lso had been invaded by cottonwood and black l o c u s t . These t rees ranged from 2 to 11 years and were hea l t h i e s t on 66 cm of cover . Brundage found tha t when the s o i l depth was 20.3 cm or less the vege ta t i v e cover d imin ished wi th the depth of cover . The number of p lants decreased and t h e i r s i z e and v i go r were reduced. He could not f i n d a d i f f e r e n c e in v igor and dens i t y of growth at depths between 23 cm and 91 cm. In t h i s study cover ing a lso increased the pH and reduced t o t a l a c i d i t y and i ron in the dra inage d ischarge of these mine wastes. Brundage concluded tha t 31 t o 46 cm of overburden or t o p s o i l are s u f f i c i e n t to support vegeta t ion and to reduce or e l im ina te ac id drainage e f f e c t s . - 52 -Hodgson et a l . (1963) cons idered that a 30 cm depth of cover was necessary to achieve optimum r e s u l t s . They found, however, tha t 80% of the y i e l d obta ined wi th a 30 cm cover could be obta ined wi th a cover of 22, 15, and 7.5 cm i f the f e r t i l i z e r r a te was increased wi th decreas ing depth of cover . Thus the 7.5 cm depth of cover rece ived double the f e r t i l i z e r requ i red by the 22 cm depth to ob ta in 80% of the y i e l d of a 30 cm depth of cover . M i c h e l l u t t i (1974) a lso s tud ied depth of t o p s o i l requirements f o r the rec l amat ion of ac id and metal contaminated mine t a i l i n g s . S o i l s were spread in 2.54 cm, 5 cm, 10 cm and 15 cm layers on the t a i l i n g s . The s o i l s ranged in t ex tu re from medium (loam) t o coarse (sand) . Limestone and f e r t i l i z e r s were app l i ed wi th the t o p s o i l . A f t e r 2 months, y i e l d s i nd i ca ted that the 6 cm treatment of medium tex tu red s o i l proved to be super io r to a l l other t rea tments . The loam had a higher mois ture and nu t r i en t ho ld ing capac i t y than the sandy s o i l s and thus provided a more hosp i t ab l e medium fo r p lant growth. M i c h e l l u t t i concluded tha t the t a i l i n g s should be covered with a 10 - 15 cm layer of s o i l . Other types of ma te r i a l s have been used as cove r s . M i c h e l u t t i (1974) examined the e f f e c t s of mulches versus s o i l as a cover . A f i e l d study using s t raw-aspha l t and curaso l (a polymer d i s pe r s i on ma t e r i a l ) was set up. With t ime , the mulches proved to be un s a t i s f a c t o r y in promoting p lant growth. For i n s t ance , on the 5 cm mulch treatments p lan t m o r t a l i t y was high and the remain ing vegeta t ion was s tun ted . In comparison, p lants growing on the 5 cm s o i l l ayer were hea l t hy . Berg and Vogel (1973) found mulches b e n e f i c i a l in rec lamat ion as they increased the leach ing e f f i c i e n c y of ac id wastes. The i r data i nd i c a t e tha t the so l ub l e s a l t content near the sur face of mine s p o i l s which ranged in pH from 2.6 t o 5.0 was s u b t a n t i a l l y reduced by as much as 80% wi th a mulch t reatment . Th is was a t t r i b u t ed to an increase in leach ing of s a l t s brought about by the mulch which cons i s ted of a 7.5 cm layer of wood c h i p s . Berg and Vogel a l so found that the mulch treatment was e f f e c t i v e in r a i s i n g the sur face pH l e ve l s of the s p o i l , g ene ra l l y by an increment of 0.3 pH u n i t s . The e f f e c t of the mulch was greates t in the upper 15 cm of the p r o f i l e and decreased with depth. Berg and Vogel suspected that mulches would a l so reduce aluminum s o l u b i l i t y . Therefore they tes ted the s po i l samples f o r water s o l ub l e aluminum and found tha t the mulch g r e a t l y reduced i t s c oncen t r a t i on . For example, in one sample, water s o l ub l e aluminum was reduced by 97%, from 111 ppm to 4 ppm. They a t t r i b u t ed t h i s reduc t ion to the complexing of aluminum by the mulch. A reduc t i on in water s o l ub l e aluminum could mean the d i f f e r e n c e between p lant s u r v i v a l and death on s i t e s that are of marginal t o x i c i t y . 3 .2 .8 Amendments Watkin (1979) was i n t e r e s t ed in the e f f e c t s , i f any, of severa l d i f f e r e n t amendments on a c i d i c t a i l i n g which ranged in pH from 1.5 to 3. He eva luated the use of the amendments as po t en t i a l rec lamat ion ma te r i a l s by mon i to r ing shoot growth y i e l d s of a crop ( b i r d s - f o o t t r e f o i l ) p lanted on the t a i l i n g s which had been t r ea ted wi th the var ious amendments. The amendments t e s t ed were rock phosphate, dusts from cement and phosphate f e r t i l i z e r manufacture, anhydrous ammonia, f l y ash and a g r i c u l t u r a l 1imestone. - 54 -Y i e l d s on the t a i l i n g s t r ea t ed wi th a g r i c u l t u r a l l imestone were c o n s i s t e n t l y g rea te r than on a l l other p l o t s and the l imestone - rock phosphate mix was p a r t i a l l y success fu l in ame l i o ra t i ng the t a i l i n g s to produce r e l a t i v e l y high shoot y i e l d s . Cement and phosphate dust p l o t s produced very l i t t l e or no growth and other amendments were equa l l y i n e f f e c -t i v e in ame l i o ra t i ng the t a i l i n g s . 3.2.9 M ix ing ' Smith et a l . (1975) have approached the rec lamat ion of ac id t a i l i n g s d i f f e r e n t l y . They propose mix ing the ac id s po i l wi th cover ma te r i a l ra the r than bury ing i t . They be l i eved i t may be s u i t a b l e to blend the ac id s po i l w i th a n e u t r a l i z i n g m ineso i l and in a sense d i l u t e the ac id e f f e c t or n e u t r a l i z e i t . They found that the optimum b lend ing mate r i a l is sedimentary rock con ta i n i ng l a rge amounts of ca l c i um, magnesium, and potassium n e u t r a l i z e r s . The n e u t r a l i z e r s can react with s i l i c a t e and carbonate ac id oxides r e l e a s i ng carbon d i ox i de and leav ing ca lc ium and magnesium n e u t r a l i z e r s behind in the s o i l - s p o i l m ix tu re . Craze (1977) a lso cons idered mix ing as a rec lamat ion techn ique . The s p o i l r e q u i r i n g rec lamat ion was extremely t o x i c con ta in ing high concent ra-t i o n s of z i nc (26,000 ppm), lead (8,000 ppm), copper (1,000 ppm), and 395,000 ppm of i ron as p y r i t e (FeSg). Sa l t content was extremely high with e l e c t r i c a l c o n d u c t i v i t i e s of 31' mmhos/cm and pH was extreme, ranging from 2.9 to 3 .3 . The s o i l - s l i m e mixtures conta ined 0, 20, 40, 60 and 80 per cent s l ime s . Limestone was a l so app l i ed at high rates to these m i x tu re s . Germinat ion f a i l e d on a l l mixtures con ta in ing s l imes with no l ime and poor germinat ion occurred on mixtures con ta i n i ng 60 to 80% s l imes . Large - 55 -depress ions in y i e l d s r e su l t ed from contaminat ion of the s o i l wi th s l imes . Craze est imated a 20% s l ime contaminat ion would depress the y i e l d by 50% even i f l ime were added. 3.3 Summary and Conc lus ions Reclamat ion by the estab l i shment of ac id t o l e r a n t spec ies i s not p r a c t i c a l in terms of the S u l l i v a n s i t u a t i o n . As noted in sec t i on 3 . 2 . 1 , the study by Berg and Vogel (1968) i nd i c a t e s that agronomic ac id t o l e r a n t spec ies cannot become e s t ab l i s hed in the low pH l e v e l range c h a r a c t e r i s t i c of the S u l l i v a n Mine ox i d i z ed i ron t a i l i n g s . This i s confirmed by Cominco's attempts in 1974 and 1975 (Gard iner and S t a t he r s , 1974, 1975). The on ly p o s s i b i l i t y f o r rec lamat ion by vegeta t ion of the S u l l i v a n Mine o x i d i z ed i r on t a i l i n g s may be the few spec ies c o l l e c t e d d i r e c t l y from contaminated s p o i l which have been found to be g e n e t i c a l l y adjusted to extreme metal contaminat ion and ac id cond i t i ons (Cox, 1978, 1979; Smith and Bradshaw, 1972; Kuja and Hu t ch i n son , . 1979 ) . However, a seed source f o r these spec ies in q uan t i t i e s s ub s t an t i a l enough to p lant 240 hectares of the S u l l i v a n Mine i r on t a i l i n g s pond is not a v a i l a b l e . I f the source was a v a i l a b l e the ac id t o l e r a n t spec ies could not get e s t ab l i s hed as t h e i r roots cou ld not penet ra te the hardpan which covers 85% of the S u l l i v a n Mine i r on t a i l i n g s pond. Liming i s a lso imp ra c t i c a l f o r ame l i o ra t i ng the S u l l i v a n t a i l i n g s . The S u l l i v a n s i t u a t i o n w i th respect to l im ing c l o s e l y p a r a l l e l s the problems tha t Watkin (1975) faced wi th ac id t a i l i n g s , that i s , l im ing i s on ly t empo ra r i l y e f f e c t i v e on ac id generat ing s p o i l s . Techniques fo r p r e d i c t i n g ac id genera t ing p o t e n t i a l have been found use fu l f o r ac id s p o i l l im ing recommendations (Duncan and Walden, 1975; Berg et a l , 1968) . - 56 -Duncan and Walden tes ted the ac id generat ing po t en t i a l technique on the S u l l i v a n s p o i l . They found that the t h e o r e t i c a l ac id product ion f o r the S u l l i v a n t a i l i n g s is 764 kg/tonne (1,685 l b s / t on ) w i th an ac id consumption of 107 kg/tonne (235 l b s / t o n ) . This i s cons idered h i gh . The i m p r a c t i c a l i t y of l im ing has been proven by the rec lamat ion team at S u l l i v a n in a greenhouse s tudy . They found a l ime requirement in excess of 556 tonnes/hec ta re (248 tons /ac re ) CaC03 per 2,240 tonnes/hectare (1,000 t ons /ac re ) of t a i l i n g s (Gard iner and S t a t he r s , 1975). E x t r apo l a t i on of the growth study to an ope ra t i ona l s ca l e i nd i ca ted that an excess of 896 tonnes/hec ta re (400 tons /ac re ) of do l om i t i c l imestone would be requ i red to ma in ta in a pH environment s u i t a b l e f o r p lant growth w i t h i n one-foot depth. T rans la ted i n to c o s t s , the a pp l i c a t i o n and i n c o r po r a t i o n , i f p o s s i b l e , would in excess of $9,680 per hectare ($4,400 per acre) i n 1975 d o l l a r s . As i t was, the growth experiments were run f o r 20 weeks. It i s l i k e l y tha t maintenance l im ing would be endless as Berg and Voge l ' s study i n d i c a t e . I f l im ing were p r a c t i c a l the hardpan, as noted, would present i n co rpo ra t i on d i f f i c u l t i e s . Leaching to remove ac ids such as was done by James and Morst (1965) and James (1966), and to remove s a l t s ( S t r u t h e r s , 1964; Berg et a l„ 1975) i s not p r a c t i c a l at S u l l i v a n Mine. The t a i l i n g s are sa tura ted below the su r face c r u s t . Therefore leach ing would on ly occur in the sha l low l aye r of ox i d i z ed t a i l i n g s , where the hardpan was broken or absent, and water would accumulate and bu i l d up at the ox i d i z ed -unox i d i z ed t a i l i n g s i n t e r f a c e . Leaching of the S u l l i v a n Mine ox i d i zed i ron t a i l i n g s was attempted in a greenhouse study (Gard iner and S t a t h e r s , 1975). The t a i l i n g s were leached three or more t imes w i th 1 cm of water per cm depth of t a i l i n g s before a 48% - 57 -cumulat ive y i e l d , r e l a t i v e to an a g r i c u l t u r a l s o i l , was produced. T a l l f e s cue , a s a l t t o l e r a n t spec ies was the p lan t used in the s tudy. Th is l each ing treatment a lso inc luded a l imestone app l i c a t i o n of 556 tonnes/ hectare (248 tons /ac re ) of do l om i t i c l imestone per 2,240 tonnes/hectare (1,000 t ons / acre) of t a i l i n g s and 336 kg/hectare (300 l b s / a c r e ) of n i t r o g e n , 224 kg/ hec tare (200 l b s / a c r e ) o f P 2O5 and 168 kg/hectare (150 l b s / a c r e ) o f K 2 O . Leaching of s o l ub l e s a l t s from the r oo t i ng zone would r equ i r e an i r r i g a t i o n and an i n t e r v a l dra inage system. The est imated cost of t h i s i r r i g a t i o n system was $200 t o $585 per acre or $440 t o $1,285 per hectare i n 1975 d o l l a r s (Gard iner and S t a t he r s , 1975). The cost of the dra inage system was not e s t ima ted . Even i f the i r r i g a t i o n system were i n s t a l l e d the hardpan would probably prevent the downward pe r co l a t i on of water. (The 48% y i e l d in the greenhouse study was performed under a r t i f i c i a l c o n d i t i o n s . The pots conta ined on ly f i n e s which passed through an 8 mesh s ieve (2.38 mm) and d id not conta in a hardpan.) F lood ing the pond is imp rac t i c a l due to the e levated po s i t i o n of the pond and the d i f f i c u l t y of c o n t r o l l i n g seepage. The high evaporat ion versus p r e c i p i t a t i o n c h a r a c t e r i s t i c s of the dry K imber ley c l imate would probably r equ i r e supplemental add i t i ons of water , ou ts ide of water supp l i ed by p r e c i p i t a t i o n , to keep the pond f l ooded . Burying the S u l l i v a n Mine i ron s po i l as s tud ied by Rogowski and Jacoby (1979) and P ionke and Rogowski (1979) t o prevent the ox i da t i on of the s u l f i d e s i s imposs ib le due to the method of depos i t i on of the s u l f i d i c m a t e r i a l . The t a i l i n g s are depos i ted as a s l u r r y . To prevent ox i da t i on of the s u l f i d e s , the t a i l i n g s would have to be bur ied wh i l e s a tu r a t ed . This i s - 58 -imposs ib le as the t a i l i n g s are t h i x o t r o p i c and cannot support heavy equipment. Even i f they cou ld , the seepage waters from the base of the pond would have to be con ta ined . Other t reatments have been tes ted on the S u l l i v a n t a i l i n g s such as adding sewage s ludge and mix ing wi th other t a i l i n g s . Sewage sludge was found to be i n e f f e c t i v e as a n e u t r a l i z i n g agent or as a cond i t i one r aga ins t the e f f e c t s of s o l ub l e s a l t s (Gard iner and S t a t he r s , 1974) . However, a pp l i c a t i o n o f HB Mine t a i l i n g s at a ra te of 50% by weight , reduced the s a l t concen t ra t i ons to a greater extent than that which occurred by l each i ng . Mix ing the t a i l i n g s with a non t o x i c ma te r i a l to produce a d i l u t i o n e f f e c t as was suggested by Smith et a l . ( 1975) and Craze (1977) i s a l so imposs ib le due to the impermeable fe r rug inous cap. I t appears that cover ing the t a i l i n g s with s o i l or overburden may be the on ly approach to rec lamat ion f o r these t a i l i n g s . However, the success of a rec lamat ion program should be measured in long term economics, long term p r a c t i c a b i l i t y , the obtainment of s e l f - s u s t a i n i n g c ond i t i o n s , as we l l as f u l f i l l i n g the r e s p o n s i b i l i t y of p ro t e c t i on of the environment. The cover ing of the t a i l i n g s , in short term economics, i s l i k e l y to be expens ive . Watkin (1975) d i s cussed the economics of cover ing versus l i m i n g . Accord ing to h is c a l c u l a t i o n s , with l im ing at 112 tonnes/hectare (50 tons /ac re ) of l imestone with 1,340 kg/hectare (1,200 l b s / a c r e ) of f e r -t i l i z e r , the cost of a pp l i c a t i o n and seeding would approach rough ly $4,400 per hectare ($2,000.00 per acre) i n 1973 d o l l a r s . The cos t of us ing overburden would approach $8,800 - $13,200 per hectare ($4,000 - $6,000 per a c r e . ) - 59 -The S u l l i v a n s i t u a t i o n requ i res an excess of 896 tonnes/hectare (400 t ons /ac re ) of do l om i t i c l imestone and t h i s would serve to lessen the gap in cost between l im ing and cove r i ng . But i f cover ing requ i red on ly i n i t i a l l im ing and f e r t i l i z i n g dur ing stand es tab l i shment wi thout f u r t h e r maintenance c o s t s , then, over the long term the economics of cover ing may be j u s t i f i e d . The f e a s i b i l i t y of t h i s approach i s strengthened somewhat by the a v a i l a b i l i t y of t h i c k depos i t s of t i l l ma te r i a l proximate to the d i sposa l a rea . This would reduce t r a n spo r t a t i o n c o s t s . However there is some evidence in the l i t e r a t u r e that d i r e c t placement of cover on such t a i l i n g s may not be long term though the short term r e s u l t s have been extremely p o s i t i v e . M i c h e l u t t i (1974) observed that a 5 cm cover ing of s o i l over s u l f i d i c t a i l i n g s became contaminated by the s p o i l below. The pH of the s o i l dropped to 3 . 5 . Smith and Bradshaw (1972) desc r i be a s i m i l a r s i t u a t i o n on an ac id s po i l in the G len r i dd ing and lower Swansea V a l l e y . Sp i r e s (1975) covered s u l f i d i c t a i l i n g s with organ ic s o i l . He found tha t p lant s u r v i v a l was good i n i t i a l l y but H + , SO4 2 " ions with copper, n i c k e l and i r on e ven t ua l l y moved up in to the organ ic s o i l and accumulated. A f t e r 15 months, the pH of the layer in contact with the t a i l i n g s had dropped below pH 3.0 from pH 4 . 6 . The upward m ig ra t i on of ac ids and t o x i c concent ra t ions of heavy metals i s a d i s t i n c t p o s s i b i l i t y at S u l l i v a n Mine. The dominant process would l i k e l y be upward due to high evaporat ion ra tes c h a r a c t e r i s t i c of the area . However cover ing may s t i l l be a s u i t a b l e approach i f the overburden i s separated from the t a i l i n g s by a b a r r i e r of p l a s t i c or gravel depending on what i s f e a s i b l e . A grave l b a r r i e r appears to be an economica l l y v i a b l e - 60 -route as the grave l source may be the rock dump mate r i a l adjacent to the t a i l i n g s pond. The approach of cover ing the t a i l i n g s d i r e c t l y versus with a gravel l aye r i s i n ve s t i ga t ed in t h i s t h e s i s . - 61 -4.0 Exper imental Design 4.1 In t roduc t i on The o v e r a l l aim of t h i s experiment was to t e s t whether the rec lamat ion of the S u l l i v a n Mine ox i d i z ed i ron t a i l i n g s could be achieved by cover ing them d i r e c t l y w i th overburden and a lso to t e s t whether a grave l b a r r i e r p laced between the t a i l i n g s and overburden was necessary to prevent upward m ig ra t i on of a c i d s , s a l t s or t o x i c chemica l s . The under ly ing premise of the experiment was that the overburden would become contaminated by the t a i l i n g s due to the d i r e c t contact with them. However, the chemical processes invo lved in upward m ig ra t i on of a c i d s , and metals made so l ub l e by the a c i d s , as we l l as s a l t s are not w ide l y known. There was some quest ion that a pan could form n a t u r a l l y in the overburden and c reate a b a r r i e r at some po i n t , p r o t e c t i ng the uncontaminated ma te r i a l above. Th is would make d i r e c t cover ing without gravel a f e a s i b l e , economical and p r a c t i c a l rec lamat ion procedure. The other part of the experiment i n vo l v i ng the grave l l a y e r , was set up t o answer the quest ion of the e f f e c t i v ene s s of grave l as a b a r r i e r , u l t i m a t e l y prevent ing upward movement. The p o s s i b i l i t y of downward " s i l t i n g i n " of the grave l could make the necessary connect ion between t a i l i n g s and overburden to cause overburden contaminat ion . The most r ap i d way to t e s t t h i s was to set up a l abo ra to ry experiment where the environmental cond i t i ons could be a c ce l e r a t ed . The experiment cou ld not s imu la te a r ea l f i e l d s i t u a t i o n but could at l eas t t e s t t h i s quest ion of upward movement and g ive some idea of the processes that may occur . - 62 -The experiment was set up to study a long term rec lamat ion procedure through a short term time f rame. The most e f f i c i e n t way to i n ve s t i g a t e t h i s idea in the l abo ra to r y was through a column study. The columns were f i l l e d with the requ i red ma te r i a l s such as overburden, t a i l i n g s , and g r a v e l . Every e f f o r t was made to dup l i c a t e cond i t i ons in both t reatments and to con t r o l ex te rna l i n f l uences not invo lved in the exper iment, thus changes could be a t t r i b u t ed to known s p e c i f i c f a c t o r s and not l e f t t o 'hazard a gues s ' . To t e s t changes, three d i f f e r e n t sets of analyses were necessary. F i r s t each column conta ined sampling po r t a l s at s p e c i f i c l e ve l s so tha t s o l u t i o n s could be c o l l e c t e d from the columns on a monthly bas is and chem i ca l l y ana lyzed . These were to i n d i c a t e the ra te of change and a lso to con f i rm tha t changes were o c cu r r i n g . I f the rates of m ig ra t i on were s lower , i t would have been necessary to a l t e r the sampling schedule of the columns. The experiment was designed to inc lude subsets of columns in operat ion f o r 3 , 6, and 9 months, and to s p l i t and sample them .at s p e c i f i c height i n t e r v a l s . There were on ly two sampling po r t a l s in the columns in the overburden f o r s o l u t i o n e x t r a c t i o n but there were 9 d e s t r u c t i v e sampling l e v e l s in the overburden, the greater number being needed to detect the height of maximum mig ra t i on and the degree of contaminat ion at the va r i ous he i gh t s . As i t was, changes occurred at a ra te that made the sampling of 3, 6, and 9 month per iods u s e f u l . Tota l ana l y s i s was c a r r i e d out on the s o i l samples c o l l e c t e d . This t e s t was necessary to conf i rm tha t increases in contaminants in the s o l u t i o n s ex t rac ted were a product of add i t i ons to the overburden from the t a i l i n g s and not due to changes in s o l u b i l i t y of the compounds in the overburden as a r e s u l t of i n c reas ing a c i d i t y . - 63 -An ex t r a c t ab l e metal ana l y s i s was a lso c a r r i e d out as a supplement to the t o t a l ana l y s i s and as a method of de tec t i ng changes in concen t ra t i on masked in the t o t a l ana l y s i s by the tremendous d i l u t i o n f a c t o r of the t o t a l ana l y s i s procedure. In a d d i t i o n , o x i d a t i o n - r educ t i o n (redox) p o t e n t i a l s ' were read on the s o l u t i o n s ex t rac ted from the sampling po r t a l s in the overburden and t a i -l i n g s . This t e s t was inc luded as a complement to the chemical ana l y s i s of the s o l u t i o n s ex t rac ted from the sampling p o r t a l s , as the r e s u l t s would a l so i n d i c a t e any changes in the chemist ry of the overburden or t a i l i n g s . To inc rease the v a l i d i t y of the exper iment, i t was necessary to u t i l i z e ma t e r i a l s in the experiment from the mine s i t e . Therefore the overburden was taken from a s i t e adjacent to the i ron t a i l i n g s pond. The depos i t of overburden, adjacent to the pond, i s deep and i t is t h i s ma te r i a l that would l i k e l y be used to cover the t a i l i n g s i f t h i s rec lamat ion procedure was adopted. I t i s important that the overburden used in t h i s experiment can support v ege t a t i o n . However, vege ta t i on was not a v a r i a b l e inc luded in the e xpe r i -ment. The f o l l ow i ng is a standard sec t i on on ma te r i a l s and methods as we l l as a d i s cu s s i on of the bas i s and reasoning fo l l owed in deve lop ing the e x p e r i -mental des ign . 4.2 Ma t e r i a l s The overburden was c o l l e c t e d from a d i t c h ( P l a t e 4 . 1 ) , north of the i r on t a i l i n g s pond, which runs p a r a l l e l to the r a i lway t r a c k s . The .d i t ch is l oca ted on the a e r i a l photograph of the t a i l i n g s pond in P l a t e 1.1, Chapter 1. - 64 -- &5 -The overburden is a gravel ly s i l t loam g lac ia l t i l l (Plate 4.2) of Pleiostocene or ig in and the so i l is c l a s s i f i ed as an Orthic Humo-Ferric Podzol (Morton, 1976) from the Hyak so i l series (Ke l ly and Sprout, 1956). A descr ipt ion of the so i l p ro f i l e (Appendix 3.1), pa r t i c l e s ize analysis (Appendix 3.2) and water retention data (Appendix 3.3) is given in Appendix 3. The t a i l i ng s were col lected from the surface of the ' o l d ' iron t a i l i ngs pond and were well oxidized and cemented. The s i te from which they were col lected is also located on Plate 1.1. The chemical and physical properties of the t a i l i ng s are discussed in Chapter 2. A local supply of gravel was used. 4.3 Methods 4.3.1 Sample Preparation The t a i l i ngs were brought to the Department of So i l Science, U.B.C. and were air dr ied. They were then ground to pass through a 2 mm sieve to promote uniform packing. If the t a i l i ngs had been placed in the columns without grinding but- as cemented p late lets i t would have been d i f f i c u l t to obtain the same quantity of t a i l i ngs in each column and therefore d i f f i c u l t to supply the same acid producing potential to each column. The overburden was brought into the So i l Science Department,. U.B.C. and was a i r -d r i ed . The coarse fragments greater than 2.54 cm were removed to promote more uniform packing but th is material was not ground. It was placed in the columns as dr ied, i r regu la r l y shaped clods because i t was found in a p i l o t project, to cement, due to the high s i l t and calcium carbonate - 66 -content , i n to a hard layer once i t was ground to pass through a 2 mm s i e ve . Under non-saturated c ond i t i o n s , such as were p red i c ted to occur in the Treatment 1 columns, the f i n e pores created by the s laked s i l t mate r i a l would reduce the evaporat ion ra te ( i n the vapor phase) in comparison to a system c o n s i s t i n g of l a rge vo ids and channe ls . For t h i s reason, i t was not ground. A l s o , the coarse form more c l o s e l y p a r a l l e l e d the natura l c o n d i t i o n . During most of the experiment the columns were al lowed to dry out to promote upward movement. However, they were p e r i o d i c a l l y watered at the sur face to s imu la te a r a i n f a l l event and to supply water f o r s o l u t i o n e x t r a c t i o n . I t was hoped that the overburden in the columns would not s l ake as a r e s u l t of the water a pp l i c a t i o n i f the water was app l ied at a r a te equal to or less than the hyd rau l i c c o ndu c t i v i t y of the overburden. I t was a l so hoped tha t t h i s r a t e could be obta ined n a t u r a l l y by a r t i f i c i a l l y s l a k i n g the su r face few cent imeters when the " r a i n f a l l " event f i r s t o c cu r r ed . Surface s l a k i n g would prevent rap id f low through natura l channels in the overburden. This was important as r ap i d f low would r e s u l t in non-uni form wet t ing of the s o i l as we l l as c r ea t i ng the po t en t i a l f o r the es tab l i shment of a temporary water t a b l e in the grave l l aye r of the Treatment 1 columns. Surface s l a k i n g would r e s u l t in a t ab l e of water s i t t i n g d i r e c t l y on the top of the overburden with the s laked sur face ac t ing as a r e l a t i v e l y impermeable l ayer a l l ow ing only slow downward movement of. water . Gene ra l l y , t h i s occurred and the overburden d id not s l ake w i t h i n the columns. In p repara t i on f o r the de s i c c a t i on pe r i od , the sur face of the columns was "plowed" to re juvenate good s o i l s t r u c t u r e . Sur face plowing i s - 67 -j u s t i f i e d , for in a f i e l d s i tuat ion maintenance of structure would be supplied by plant roots and/or by plowing. 4.3.2 Column Design Nine plex ig lass columns, 85 cm in height with an inside diameter of 15 cm were constructed for each treatment. (Figure 4.1.) The plex ig lass was roughly 0.6 cm thick and each column was supported by a 20 cm square plex ig lass base. The 15 cm column diameter was required to reduce edge e f fec ts . In a p i l o t study with columns 91 cm in height and 5 cm in diameter edge ef fects , which cause more rapid migration than that which occurs between so i l pa r t i c l e s , v i s i b l y appeared to dominate the upward processes (Plate 4.3) . Thus, edge effects would mask and d is tor t the effect of movement between the t a i l i ngs and overburden so i l pa r t i c l e s . In the same l i gh t , tensiometers and solut ion sampling apparatus, inserted hor izonta l ly into the columns were roughly 9 cm in length and thus would exceed the diameter of the narrow columns. In the last stage of the experiment, the columns were sp l i t and sampled. With a 5 cm diameter column, material located at or near the plexiglass - overburden interface, affected by edge ef fects , would have had to have been included in order to obtain enough sample for the required chemical analyses. Larger columns were therefore necessary to reduce the influence of edge e f fec ts . Each column had four sampling portals which were roughly 2.9 cm in diameter. The portals were located to include sample areas below and above the water table in the t a i l i ng s mater ia l , and a sampling area in the overburden f a i r l y proximate to the overburden-tai1ings boundary - a probable - 68 -TREATMENT I |L9 FIGURE 4.1 Column Design TREATMENT ^OVERBURDEN. SAMPLING LEVELS .GRAVEL BARRIER -TAILINGS-- WATER RESERVOIR •B A SOLUTION SAMPLING APPARATUS COLUMN WALL PLEXIGLASS TUBING (NOT TO SCALE) •MERCURY POOL Narrow Columns in P i l o t P r o j e c t , I l l u s t r a t i n g Edge E f f e c t s . - 7.0 -s i te for the most intensive react ions. The uppermost portal was situated near the top of the columns to provide a base l ine for comparison of changes in the overburden between the two levels located in the overburden. The portals and the i r location in the column are i l l u s t r a ted in Figure 4 .1 . 4.3.3 Water Table Apparatus In order for upward migration to occur water must move up through the columns by cap i l l a r y movement. Thus, each column was equipped with a water table located at a height halfway in the t a i l i ng s mater ia l . The water table was maintained at th is level throughout the experiment. It was connected to the columns by f l e x i b l e tubing attached to a plexig lass tube inserted at the base of the columns. Inside the column the plexig lass tubing was perferated with 2 mm s ize holes to encourage uniform flow in the base of the columns and to el iminate potent ia l clogging of the water table connection. D i s t i l l e d water was used in the water table apparatus so as not to introduce contaminants into the system. 4.3.4 Method of Packing Each column consisted of 30 cm of t a i l i ngs and 45 cm of overburden. As the Treatment 1 columns contained a gravel layer, the packing of the columns for the two treatments is discussed separately. Treatment 1 A c i r cu la r piece of nylon screening, less than 15 cm in diameter, was placed ins ide, at the base of each of the columns to provide even d i s t r i bu t i on of incoming water from the water table and to reduce a i r - 71 -entrapment. The water t ab l e was then connected but the f low was c on t r o l l e d at a low ra te and at s p e c i f i c l e v e l s , by clamping the tub ing which connected the water t ab l e to the columns, du r ing the f i l l i n g p rocess . I n i t i a l l y the water l e ve l was set at 5 cm and 2.5 cm of very coarse sand ( rough ly 2 mm in diameter) were added to the columns and v i b ra ted to prevent a i r entrapment and l a t e r s e t t l i n g . The same procedure was next fo l l owed w i th 2.5 cm of coarse quartz sand (0.5 to 1.0 mm in s i z e ) . These base ma t e r i a l s were t h r i c e ac id washed w i th 6NHC1 and t h r i c e d i s t i l l e d water r i n s ed to remove contaminants inherent in the ma te r i a l s before pack ing . The base ma te r i a l was inc luded as a means of prevent ing c logg ing of the water t a b l e connect ion by f i n e t a i l i n g s p a r t i c l e s . I t a lso even ly d i s t r i b u t e d i n f l ow ing water from the water t a b l e , to the t a i l i n g s above to ensure uni form we t t i ng of the t a i l i n g s . The water t ab l e l e ve l was increased in steps as the t a i l i n g s were added dry and in increments . The columns were v i b ra ted wi th each increment to promote set t lement in order to reduce l a t e r c r a c k i ng , s w e l l i n g , and slumping of the t a i l i n g s . Th is aided in c o n t r o l l i n g the l eve l of the t a i l i n g s in the column "which was an important cons i de ra t i on due to the presence of the sampl ing po r t a l s as these were designed to monitor the t a i l i n g s at p a r t i c u l a r l e v e l s . Sett lement was a lso important as an a id to ob ta i n i ng uni form bulk dens i t y of the t a i l i n g s in a l l of the columns. The bulk den s i t y of the t a i l i n g s f o r a l l 18 columns was c a l c u l a t ed as rough ly 1720 kg/m 3 . Once the requ i red l e ve l of t a i l i n g s was reached (30 cm) the columns were al lowed to stand fo r one day u n t i l swe l l i n g and sett lement had ceased. At t h i s t ime the water t a b l e was lowered to i t ' s exper imenta l l e ve l -- 72 -approximately half way up in the t a i l i ng s i .e . at the 15.0 cm ta i l i ngs l eve l . The in te r io r surface of the columns were cleaned to prevent contamination of the overburden by t a i l i ngs dust, added during the f i l l i n g process. A 5 cm layer of gravel (approximately 2.5 cm in diameter) was care fu l l y placed and compacted above the t a i l i n g s . The same washing and r ins ing procedure was applied to the gravel as was carr ied out on the base mater ia l . The overburden was then added dry and in increments. Each increment was moderately compacted by a small f o r k - l i k e instrument in order to obtain as much uniformity as poss ib le. The overburden was added level with the upper edge of the columns to provide maximum exposure to the atmosphere and packed to a bulk density of 1,580 kg/m 3. By th is stage a l l sampling portals had been temporari ly sealed with neoprene stoppers. The columns were subsequently watered with d i s t i l l e d water to the amount of 1,000 mis to f a c i l i t a t e insert ion of the tensiometers and the solut ion sampling apparat i , ' and to provide solut ion for the i n i t i a l l i qu id sample extract ion at time zero in the experiment. Treatment 2 The columns of Treatment 2 were set up in an analogous manner except the gravel barr ier was not included and 10 cm of base material (5 cm of very coarse sand, 5 cm of coarse sand) were added. The addit ional amount of sand was necessary to compensate for the absence of gravel as a l l 18 columns were the same height and consisted of the same quantity of t a i l i ng s and overburden. - 73 -The base ma te r i a l was cons idered to have no e f f e c t on the processes occu r r i ng in the columns. The columns i n Treatment 2 rece i ved 500 mis of d i s t i l l e d water . 4 .3 .5 Tensiometer Apparatus Fo l l ow ing the packing of the columns, ceramic tens iometers were h o r i z o n t a l l y i n se r t ed i n to the rear of one column fo r each t reatment , oppos i te the sampling p o r t a l s , to monitor mois ture s ta tus of the columns dur ing the d ry ing pe r i od s . As i t was not p r a c t i c a l to set up 18 sets of tens iometers i t was be l i eved tha t on ly one column from each treatment equipped wi th tens iometers would be accep tab le . This was not an idea l s i t u a t i o n but by t r e a t i n g the columns in a s i m i l a r manner, the tens iometer apparatus would i n d i c a t e , the water t ens ion of the other columns of the r e spec t i v e t reatment . In order to i n s e r t the tens iomete r s , cores were taken by brass corers of the same diameter as the ceramic cup. The tens iometers were then i n se r t ed wi thout d i s t u r b i n g the mate r i a l in the column. The apparatus was cons t ruc ted accord ing to the M u l t i p l e Manometer  Tensiometer de s i gn , S o i l Mo is ture Equipment Corp. and adapted to t h i s exper iment. This cons i s ted of nylon manometer tub ing [0 .24 cm (3/32 i n . ) O.D. x 0.04 cm (1/64 i n . ) wa l l t h i c kne s s ] i n se r t ed in to the s ide of a piece of p l e x i g l a s s tub ing [1 .0 cm ( (3 /8 i n . ) O.D. x 0 .3 cm (1/8 i n . ) wa l l t h i c k n e s s ] by means of a hole [0.24 cm ((3/32 i n . ) d iameter] d r i l l e d in to the p l e x i g l a s s . The nylon tub ing - p l e x i g l a s s connect ion was t i g h t l y sea led w i th rubber in which a hole less than 0.24 cm (3/32 i n . ) i n diameter had been d r i l l e d f o r the t u b i n g . The connect ion was t i g h t l y sea led wi th a hose - 74 -clamp. The nylon tub ing was forced down the p l e x i g l a s s tube towards a ceramic cup cemented to the p l e x i g l a s s (F igure 4 .1 , Page569). This po r t i on was i n se r ted in to the column. The nylon tub ing extending from each apparatus was passed through smal l ho les d r i l l e d through one s ide of the wooden chamber, housing the columns, exposing the nylon tub ing to room c o n d i t i o n s . The tub ing was then passed through holes d r i l l e d i n to the top of two 1 m s t i c k s (one fo r each t reatment) which were fastened to the e x t e r i o r of the wooden chamber (P l a t e 4 .4) . The nylon tub ing was brought down the meter s t i c k and attached to i t and f i n a l l y was i n se r ted through the metal caps of g lass b o t t l e s con ta i n i ng the mercury pool ( P l a t e 4 .4) . Each mercury con ta in ing b o t t l e had four nylon tub ing sets en te r ing i t . The tens iometers were set in operat ion by fo rce f i l l i n g the nylon tub ing w i th d i s t i l l e d , de-aerated water to expe l l a i r from the manometer system. This was done by i n s e r t i n g d i s t i l l e d water i n to the p l e x i g l a s s tub ing en te r i ng the column by means of a sy r inge which p ie rced a rubber stopper s ea l i n g the open end of the p l e x i g l a s s tube. I t was found that mois ture s t r e s s surpassed the capac i t y of the mercury manometer (1 bar) i n the overburden in Treatment 1 dur ing the dry ing p e r i o d . These manometer sets were the re fo re rep laced by psychrometers which are capable of record ing lower mois ture con ten ts . A view of the rear of the Treatment 1 column con ta in ing both types of moisture measuring apparat i i s g iven in P l a t e 4.5. - 75 -P l a t e 4.4 Wooden Chamber Constructed i n the S o i l Sc ience Department, U.B.C. The Manometer Appartus i s Attached to the Outs ide o f the Chamber. - 76 -P l a t e 4.5 Front View of Treatment 2 Column ( L e f t ) w i t h Sampling Apparatus a t Levels A, B, C, and D. Rear View o f Treatment 1 Column w i th Psychrometers Located a t Leve ls C and D and Manometer Apparatus a t Leve ls A and B. - 77 -4 .3 .6 So l u t i on Sampling Apparatus With the sets of tens iometers in p lace the s o l u t i o n sampling apparatus was inse r ted in to the f r on t po r t a l s of the columns. S im i l a r to the t e n s i o -meters, a core of equal volume as the ceramic cup of the s o l u t i o n sampling apparatus was removed to f a c i l i t a t e i t s i n s e r t i o n . The apparatus was adapted from a design by de Jong (1976) and cons i s ted of a ceramic " tens iometer" cup cemented to a p iece of p l e x i g l a s s tub ing 5 cm in l eng th . The apparatus was held in the columns by neoprene rubber s toppers through which the p l e x i g l a s s tub ing was passed. A sy r inge ( fo r sampl ing) extended from the oppos i te end of the apparatus and was cemented to a second p iece of p l e x i g l a s s tub ing which in tu rn was connected to the f i r s t p iece by a smal l length of f l e x i b l e tub ing (F igure 4 . 1 , Page6;9 ) . The i n c l u s i o n of f l e x i b l e tub ing was important as t h i s tub ing was clamped o f f dur ing nonsampling per iods to prevent a i r movement in to the columns through the s y r i nge . The sy r inge was a lso sealed o f f from the a i r at a l l t imes by rubber s toppers . This was c r u c i a l , as s o l u t i o n s were ex t r ac ted fo r o x i da t i on reduc t ion (redox) p o t e n t i a l measurements. Exposure of the s o l u t i o n s to a i r d i s r up t s the redox po t en t i a l and negates the read ing The samples were ex t rac ted by means of 20 ml prevacuumed, ac id washed vacu-t a i n e r s which were revacuumed and recyc l ed throughout the exper iment. The importance of the sampling apparatus was that sampling was always done at e x a c t l y the same phys i ca l l o c a t i on each t ime, that the sampling cou ld be done unattended, and changes in the columns could be monitored non-d e s t r u c t i v e l y , that i s without d i s t u r b i n g the column m a t e r i a l s . The a b i l i t y of ceramic cups to remove so l u t i on s cons idered in e q u i l i -br ium wi th the s o i l s , was based on in fo rmat ion that the porous wa l l s of the - 7 8 -ceramic cups are permeable to both water and s o l u t e s . The water i n s i de the tens iometer i s assumed to have the same so lu te composi t ion and concen t ra t i on as the s o i l water (Hi 1 l e i , 1971). However there seems to be some disagreement with t h i s . England (1974) s t a t e s that most ceramic cups have some ion exchange capac i t y and may remove ions as water passes through the cup w a l l s . Long (1978) has approached t h i s problem by deve lop ing s o l u t i o n - e x t r a c t i o n apparatus cons t ruc ted wi th f r i t t e d - g l a s s cups which have no ion exchange p r o p e r t i e s . F r i t t e d g lass cups were the re fo re i n i t i a l l y cons ide red . However, they were unava i l ab l e commerc ia l l y . F r i t t e d g lass cups had been const ructed in the S o i l Sc ience Department, U.B.C. accord ing to Chow (1973) but the t e ch -nique has not been per fec ted and the re fo re success fu l cons t ru c t i on was u n r e l i a b l e and extremely t ime consuming ( i . e . severa l months would be requ i red to cons t ruc t the number of cups requ i red f o r t h i s exper iment ) . Woods (1974) rep l yed to Eng land ' s (1974) comments. Woods tes ted the ceramic cups and found tha t the exchange capac i t y was very smal l and tha t the ion f i l t r a t i o n was not s i g n i f i c a n t in the ceramic cups. Therefore commerc ia l ly a v a i l a b l e 1 bar ceramic cups were u t i l i z e d f o r the sampling apparatus. Once the sampl ing apparatus was in p lace the columns were f u l l y prepared fo r the exper iment. 4 .3 .7 Rep l i c a t i o n s Due to the l a rge s i z e of the columns and t h e i r cos t , the amount of ma t e r i a l requ i red to pack the columns and i t s p repara t ion and packing t imes , as we l l as the number of s o l u t i o n e x t r a c t i o n apparatus cons t ruc ted - 79 -(76) e t c . i t was f e a s i b l e on ly to b u i l d 18 columns. As these columns are s p l i t i n to two treatments of three t ime pe r i ods , on ly three r e p l i c a t e s were p o s s i b l e . I t would have been des i r eab l e to increase the r e p l i c a t i o n number f o r s t a t i s t i c a l purposes but i t was p h y s i c a l l y not p r a c t i c a l . 4 .3 .8 Promotion of Acce l e ra ted Cond i t ions In order f o r upward mig ra t ion to occur water must move up through the columns by movement necessary f o r the d i f f u s i o n and convect ion of a c i d s , meta ls and s a l t s . This i s promoted by evaporat ion at the su r f a ce . This could have been imposed by severa l methods. For i ns tance , sub jec t i on of the upper sur face of the columns to l i g h t s could have promoted evapora t i on . Th is approach was d i sca rded as l i g h t s would des i c ca t e the sur face few cent imeters r a p i d l y reduc ing the hyd rau l i c c ondu c t i v i t y at that l eve l and thus reduce the evaporat ion r a t e . . Fans were found, in a p i l o t p r o j e c t , a l so to r a p i d l y des i c ca te the sur face as the evaporat ion ra te exceeded the c a p i l l a r y c o n d u c t i v i t y . U l t ima t e l y t h i s r e su l t ed in a reduc t ion of the evaporat ion r a t e . L igh t s would prov ide a temperature grad ient in the columns and i t would be d i f f i c u l t to a l l o c a t e equal amounts of l i g h t to each column without over lapp ing occur ing between the columns. High temperatures in the greenhouse would acce le ra te evaporat ion but the greenhouse was not cons idered f e a s i b l e as the high r e l a t i v e humid i ty in the greenhouse would counteract evapo ra t i on . A l so the temperatures in the greenhouse are subject to f l u c t u a t i o n s and thus the requ i red constant temperatures could not be ob ta ined . A growth chamber would be idea l p rov i d i ng constant regu la ted tempera-tu res which would have heated the columns evenly and un i f o rm l y . However f a c i l i t i e s f o r the 18 columns fo r the 9 month per iod were not a v a i l a b l e . - 80 -There fo re , a wooden chamber 1.8 m x 2.1 m and rough ly 3 m in height was cons t ruc ted ( P l a t e 4 .4) in the S o i l Sc ience Laboratory as a temporary growth chamber. I t was we l l i n su l a ted and equipped with a thermostat ( d i f f e r e n t i a l 1.5°C) to insure temperatures of 32°C, a fan (to draw o f f a i r of high r e l a -t i v e hum id i t y ) , a base heater , and a thermohydrograph to measure temperature and r e l a t i v e humid i ty . The roof was peaked to a l low upward movement of humid i ty and heat in the chamber. A f l a t roofed chamber would have re ta ined the humidi ty c l o se to the top of the columns reduc ing the evaporat ion r a t e . 4 .3 .9 Column Layout P lan The wooden chamber was const ruc ted to a minimum s i z e to accommodate the c o n d i t i o n s . The columns were s p e c i f i c a l l y placed in the chamber in a ran -domized pa t te rn so that no treatment rece ived more or less heat than the o the r . P l a t e 4.6 i s a view of the i n t e r i o r of the chamber with the columns in p lace and the thermohydrograph in the fo reground. The heater is located below the counter . 4 .3 .10 So l u t i on Sampling Once the columns were placed in the wooden chamber and the tens iometers were connected, the experiment was i n i t i a t e d . A f i r s t set of so l u t i on s was e x t r a c t ed , from each of the po r t a l s o f the columns, rep resen t ing time zero in the exper iment. The thermostat was then set to 32°C and incubat ion was begun under "no l i g h t " cond i t i ons f o r a three week per iod dur ing which water was evaporat ing from the columns. - 81 -P l a t e 4.6 View o f the I n t e r i o r o f the "Growth" Chamber w i th Columns, Thermo-Hydrograph, Thermosat, e t c . i n P l a ce . - 82 -A f t e r 3 weeks the thermostat was turned o f f and 1000 mis of d i s t i l l e d water were added to the columns of Treatment 1 and 500 mis to the columns of Treatment 2, to ob ta in s a t u r a t i o n cond i t i ons necessary f o r s o l u t i o n e x t r a c t i o n . Less water was requ i red by the Treatment 2 columns as water con t i nu -ous l y moved up through the columns from the water t ab l e ma in ta in ing a nea r - sa tu ra ted s t a t e . The grave l b a r r i e r in Treatment 1 prevented the upward movement of water . The overburden, t h e r e f o r e , d r i ed out and thus requ i r ed more water f o l l ow i ng the de s i c c a t i on pe r i od . Th is was i nd i ca ted by the monometer and psychrometer da t a . The tensiometer-manometer systems i nd i ca ted that the t a i l i n g s at both L e ve l s , A and B in both t reatments and the overburden at Level C in Treatment 2 remained sa tura ted or nea r - sa tu ra t i on throughout the exper iment . The tens iometer at Leve l D in Treatment 2 recorded tens ions of g ene r a l l y l ess than 0.2 bars a f te r 3 weeks under evaporat ion c ond i t i o n s . Such low suc t ions were a l so found by Gardner and Fireman (1957) in t h e i r s tud i e s of s o i l evaporat ion in the presence of a sha l low (90 cm) water t a b l e . The psychrometer data conf irmed that the overburden in Treatment 1 was more h i gh l y des i c ca ted than i n Treatment 2. In the Treatment 1 columns the overburden at depth re ta i ned more moisture than at the su r f a ce . Tensions d i d not . genera l l y exceed 4 bars at Level C in Treatment 1, the po r t a l proximate to the grave l b a r r i e r . However in Treatment 1, Level D, the uppermost p o r t a l , tens ions gene ra l l y reached 8 ba r s . Fo l l ow ing complet ion of the water ing of the columns, the columns were a l lowed to stand f o r 24 hours before the f i r s t set of s o l u t i o n s were - 83 -ex t r a c t e d . (Two sets of s o l u t i on s were ex t rac ted monthly, one f o r e l e c -t r i c a l c o n d u c t i v i t y , pH and o x i d a t i on - r educ t i on po t en t i a l measurements, and one fo r chemical ana l y s i s by the atomic absorpt ion spectrophometry method.) The columns were then al lowed to stand f o r another 24 hour per iod before the second set of s o l u t i on s were e x t r a c t ed . During these per iods rubber stoppers sea led o f f the s y r i nge s . The per iod of 24 hours was chosen as an acceptab le length of t ime fo r the added d i s t i l l e d water to reach chemical e q u i l i b r a t i o n wi th the s o i l and s p o i l m a t e r i a l s , c l o s e l y r e f l e c t i n g the i on i c s i t u a t i o n in the columns. Other authors are in agreement wi th the 24 hour i n t e r v a l to insure chemical e q u i l i b r a t i o n (Cava l l a r o and McBr ide , 1978) . As soon as po s s i b l e a f t e r c o l l e c t i o n , the s o l u t i o n s were ana lyzed . With sampling completed, the sur face of the columns were plowed to a depth of 3 cm, the temperature was increased and the columns were al lowed to incubate f o r the next 3 weeks.. This procedure was c a r r i e d out once a month f o r 9 months f o r both t rea tments . A f t e r 3 months, three r e p l i c a t e s f o r each treatment ( s i x columns in t o t a l ) were removed from the exper iment. This was repeated a f t e r 6 months and f i n a l l y the l a s t s i x columns were d ismant led a f t e r 9 months. The columns were s p l i t and sampled as they were removed from the exper iment. 4 .3 .11 Column " S o i l " Sampling The columns ( i n a ho r i z on t a l p o s i t i o n ) were s p l i t by c u t t i n g the p e r i -meter of the columns along t h e i r length and across the base r e s u l t i n g in two ha l v e s . Ha l f of the p l e x i g l a s s column could be removed l eav ing the en t i r e length of the column ma te r i a l s exposed f o r sampling as can be seen i n P l a t e s 4.7 and 4 . 8 . - 84 -P l a t e 4 . 7 Treatment 1 Column, S p l i t and Ready f o r Sampl ing. The e x t e r i o r few cent imeters of the ou ts ide sur face of the column ma te r i a l s were removed to d i s ca rd areas a f fec ted by edge e f f e c t s . Most samples were taken from the core of the column at 5 cm i n t e r v a l s r e s u l t i n g in nine being removed from the overburden and a t o t a l o f 162 samples. The sample s i z e was gene ra l l y 10 grams r e qu i r i n g adaptat ion of analyses procedures to accommodate the smal l sample s i z e . Many Treatment 2 columns conta ined an indurated hor i zon in the contaminated area of the overburden which made sampling d i f f i c u l t . Once c o l l e c t e d , the samples were placed in separate brown paper bags and were a i r d r i e d . They were then ground to pass through a 100 mesh s i eve (0.149 mm s i z e ) . The f ineness of g r i nd i ng was requ i red f o r the t o t a l ana l y s i s (by the t e l f o n bomb method) of the samples. A l l of the other analyses were c a r r i e d out on the ground sample. 4.4 Evaporat ion and R e l a t i v e Humid i ty Evidence that evaporat ion was occu r r i ng in the experiment was recorded through the psychrometer and manometer data ( sec t i on 4 . 3 . 9 ) . I t was cons ide red , t h e r e f o r e , important to est imate the ra te of evaporat ion o c cu r r i ng in the columns. To measure evaporat ion a buret was j o i ned to the water t ab l e connect ion of a Treatment 2 column. Changes with water l eve l in the buret versus time were recorded . This procedure has been u t i l i z e d by other workers (Gardner and F i reman, 1957). The evaporat ion ra te was c a l c u l a t ed from t h i s data and was d i v i ded by 100 accord ing to a 100:1 r a t i o between the s o i l column sur face area and the buret sur face area . Gardner and Fireman (1957) s i t e an evaporat ion ra te of rough ly 1 cm/day f o r a sandy loam s o i l wi th a water - 86 -table at 90 cm. The evaporation rate for the Treatment 2 columns was calculated at roughly 0.4 cm/day. Gardner and Fireman have discussed evaporation rates and state that they are a function of the depth to the water tab le, the d i f f u s i v i t y charac-t e r i s t i c s of the so i l mater ia l , and external condit ions. The depth of the water table was not a factor in the lower evaporation as Gardner and Fireman found that i f the water table is shallower than 90 cm, i t is not a l im i t ing factor to evaporation. The lower evaporation rate in th i s study may be due to, therefore, a higher re la t i ve humidity in the chamber than in the i r study, the presence of sa l t s (Gardner, 1957), the mulched surface (which reduces the evaporation rate under saturated conditions [Gardner and Fireman, 1957]) and the f iner texture of the overburden compared to the sandy loam so i l in the i r experiment. This la t ter factor is important as cap i l l a r y conductiv ity is greater for coarser so i l s than f iner textured materials under saturated conditions (Gardner, 1957). The high rate of 1 cm/day was achieved by Gardner and in Fireman in a column with fans regulated to draw off excess humidity. This provided a moisture gradient which is important in promoting evaporation. The problem of high re la t i ve humidity build-up confirms the need of high temperatures. Air at high temperatures can retain more moisture than at .lower temperatures and thus resul t in producing lower re la t i ve humidity. The re la t i ve humidity of the chamber f luctuated at 25% ±3% throughout the drying periods of the experiment. The buret method was not suitable for the Treatment 1 columns as c ap i l -lary movement was broken by the gravel bar r ie r . The resul ts would therefore indicate evaporation from the t a i l i ngs as affected by the overburden and not d i r e c t l y of the overburden. 5.0 Chemical Analysis of Solutions Collected from Overburden and Ta i l ings 5.1 Introduction tf The monthly extract ions were col lected to monitor chemical changes in the columns, as a guide to the progress of the experiment. If the upward migration into the overburden in the Treatment 2 columns had been neg l i -g ib le , as would have been indicated by the solut ions, the experiment would have been prolonged. If migration had occurred in the Treatment 1 columns, that part of the experiment would have been el iminated. The extract ions were also useful in indicat ing the presence of small concentrations of contaminants in the overburden or ig inat ing from the t a i l -ings, which were predicted to be masked by the d i lu t i on effects of the chemical ana-lyses carr ied out on the " s o i l " samples removed from the sp l i t columns. In addit ion, these l iqu id samples were analyzed d i r e c t l y without interferences or influences of extraction solut ions, so lub i l i z i ng agents or the effects of destruct ive sampling. Solutions were also col lected from the t a i l i n g s . They were considered a necessary complement to the overburden extractions as changes in the t a i l -ings would affect the processes occurring in the overburden. The data col lected includes information on the differences over time, height, and treatment which can be combined in various ways to i l l u s t r a t e time-height-treatment re la t ionsh ips . Fifteen variables were considered for the two treatments, from the 18 columns, for 9 months, and at four height l eve l s . Therefore i t is not l o g i s t i c a l l y feas ib le to present a l l of the data co l lec ted. Consequently, only selected portions of the data, which i l l u s t r a t e the trends occurring in the experiment, have been included. - 88 -5.2 Methods and Ma t e r i a l s The s o l u t i o n s were c o l l e c t e d by means of p r e - a c i d washed, d i s t i l l e d wa t e r - r i n s ed , pre-vacuumed 20 ml vacu ta ine rs accord ing to the method descr ibed in Chapter 4 . 3 . 6 . They were analyzed as qu i c k l y as pos s i b l e to avoid e r ro r due to p r e c i p i t a t i o n in the s o l u t i o n s , e s p e c i a l l y with respect to i r o n . Ana l y s i s f o r i r o n , aluminum, copper, z i n c , manganese, n i c k e l , l e ad , cadmium, c oba l t , ca l c i um, sodium and magnesium was c a r r i e d out on the s o l u t i o n s by atomic absorpt ion spectrophotometry. Standards were made from commerc ia l ly a v a i l a b l e l i q u i d standards and were made to volume wi th d i s t i l -l ed water , as the base s o l u t i o n f o r the ex t r a c t i on s from the columns was d i s t i l l e d water . As the s o l u t i o n s va r i ed chem i ca l l y over a wide range of c on s t i t u t e n t s and concen t r a t i on s , s p i k i n g the standards to match the s o l u t i o n s was not f e a s i b l e . The pH and e l e c t r i c a l c o n d u c t i v i t y measurements were c a r r i e d out d i r e c t l y on the s o l u t i on s by standard methods f o r l i q u i d samples. A method fo r measuring o x i da t i on - r educ t i on p o t e n t i a l s d i r e c t l y on the s o l u t i o n s was developed f o r t h i s exper iment. A d e t a i l e d d e s c r i p t i o n of the method and the t h e o r e t i c a l background on which the method was based is given in Appendix 6. 5.3 Resu l t s and D i s cuss i on The chemical analyses of the s o l u t i on s ex t rac ted from Leve ls C and D in the overburden i n d i c a t e that the grave l b a r r i e r i n Treatment 1 was e f f e c t i v e as an i n s u l a t i n g l aye r prevent ing upward movement of a c i d s , meta ls and s a l t s from the t a i l i n g s . The r e s u l t s a l so i n d i c a t e that overburden p laced - 89 -d i r e c t l y onto the t a i l i n g s as in Treatment 2, would e ven tua l l y become contaminated to some height and ex ten t , as a c i d s , metal ions and s a l t s migrated in to the overburden. M ig ra t i on of the ac ids and s a l t s is p red i c ted to occur as a r e s u l t of convect ion due to mass f low of the s o i l s o l u t i o n . The movement of metals i s more complex as the metals p r e c i p i t a t e and s o l u b i l i z e con t inuous l y as a f unc t i on of m ig ra t i ng ac ids and are c o n t i n u a l l y absorbed and re leased from the sur face of c l a y p a r t i c l e s . The s o l u b i l i t y of metals can be a f fec ted by i n t e r a c t i o n between the meta l s . However, a po r t i on of the movement of metals can be a t t r i b u t e d to molecu lar or i o n i c d i f f u s i o n due to concen t ra t i on g rad ien ts in the s o i l so lu t ion , , and to convec t i on . Under non-saturated cond i t i ons d i f f u s i o n can be exp la ined by F i c k ' s law: where is the f l u x of the d i f f u s i n g substance per un i t area of s o i l , D the e f f e c t i v e d i f f u s i o n c o e f f i c i e n t , e the volume f r a c t i o n of water (wetness) , C the concen t ra t i on of the d i f f u s i n g substances and x i s the space v a r i a b l e . The ra te of d i f f u s i o n in to the overburden is p red i c ted to decrease with increased d i s t ance from the water t a b l e ( l oca ted in the t a i l i n g s ) as the d i f f u s i o n c o e f f i c i e n t decreases with decreas ing wetness ( e ) . The f o l l ow i ng is a d i s cu s s i on of the r e s u l t s of each of the parameters s t u d i e d . 5 .3 .1 pH ana l y s i s The r o l e of an ac id environment in enhancing the s o l u b i l i t y of most meta ls and in r e t a r d i ng or prevent ing success fu l vegeta t ion estab l i shment is - . 90 -wel l documented. Because of these a f f e c t s the p o s s i b i l i t y fo r ac id contaminat ion of the overburden r e s u l t i n g from the extremely ac id nature and ac id producing po t en t i a l of the t a i l i n g s , made pH ana l y s i s of the overburden a requi rement. The pH data from the columns which were in operat ion fo r the en t i r e 9 months of the experiment i s presented f o r Level C in F igu re 5.1(a) and f o r Level D in F igure 5 . 1 ( b ) . The pH data from the columns which were in opera t i on f o r 3 and 6 months c l o s e l y resembled the data as presented in F igures 5.1(a) and 5 . 1 (b ) . In F igure 5.1(a) the pH of the overburden in Treatment 1 Level C remained r e l a t i v e l y constant f o r the 9 month pe r i od , f l u c t u a t i n g at pH 8.3 ± 0 . 5 . This i nd i c a t e s that the grave l b a r r i e r had prevented the movement of ac ids upward from the t a i l i n g s . The pH of the overburden in Treatment 2 at Level C decreased r a p i d l y w i t h i n one month from pH 8.4, at t ime zero of the exper iment, to pH 4.0 a f t e r one month. The pH in the Treatment 2 columns at t h i s l e ve l cont inued to decrease a f te r the f i r s t month g r adua l l y approaching 2 ( s i m i l a r to the pH of the t a i l i n g s below) i n d i c a t i n g severe ac id contaminat ion . In F igu re 5.1(b) the pH data at Leve l D in Treatment 2 d i d not decrease but f l u c t u a t e d in the same range as the pH data of Treatment 1, at 8.0 t 0 . 5 , i n d i c a t i n g that ac id had not migrated through the 35 cm of over-burden t o Level D. (The r eac t i on i s extreme at Level C, as movement to the sampl ing po r t a l at Level C took place over a d i s tance of 7 cm from the t a i l i n g s - o ve r bu r den boundary). The nature of the ac id moving in to the overburden from the t a i l i n g s in Treatment 2 is cons idered to be s i m i l a r to the ac id generated in the t a i l -T-2 — I 4 TIME 1 6 (MONTH) 8 FIGURE 5 . 1 ( a ) . pH p l o t t e d aga ins t time f o r overburden a t Leve l C, t reatment 1(TR1) versus Treatment 2 (from monthly e x t r a c t i o n s ) , FIGURE 5.1(b) T r 4 6 TIME (MONTH) pff. p l o t t e d aga i n s t t ime f o r overburden a t Level D, Treatment 1 versus T rea t -ment 2 (from monthly e x t r a c t i o n s ) . - 92 -ings (Chapter 2.1) i d e n t i f i e d as s u l f u r i c a c i d . The opt imal pH range for vege ta t i on success i s rough ly 6 . 5 - 7 . 0 . There fore , the l e ve l s of a c i d i t y which pe r s i s t ed at Po r t a l C in the Treatment 2 columns would cause ser ious problems to the growth and maintenance of a vege ta t i ve cover . Ana l y s i s of the pH data from so l u t i on s ex t rac ted from Level A and B, f o r both Treatments 1 and 2, and f o r the 9 month per iod i nd i c a t e that the pH of the t a i l i n g s was not a f fec ted by l e v e l s , t reatments , t ime, or the water t ab l e and remained at 2 ± 0.5 f o r the exper imental p e r i od . The maintenance of the low pH l e v e l s in the t a i l i n g s are a d i r e c t consequence of the ac id producing po t en t i a l of the t a i l i n g s and the n e g l i -g i b l e e f f e c t of s u l f a t e reduc ing b a c t e r i a , in the columns. King et a l . (1974) in t h e i r study of the recovery of ac id s t r i p mine lakes noted that the reduc t i on of s u l f a t e s , r e s u l t i n g in an increase in pH, by s u l f a t e reduc-ing b a c t e r i a , demanded p a r t i c u l a r c ond i t i o n s . F i r s t , the dep l e t i on of oxygen in the r e spec t i v e environment and secondly accumulat ions of organic ma te r i a l to supply reduced products were necessary f o r the format ion of an anaerobic zone requ i red by s u l f a t e reduc ing b a c t e r i a . The constant exposure of the columns to oxygen through pores in the overburden and to oxygenated water through the water t ab l e and monthly a p p l i c a t i o n s , coupled wi th the low organic matter content of the t a i l i n g s was not conducive to s u l f a t e reduc ing b a c t e r i a . There fore , an increase in pH due to b a c t e r i a l ac t ion d id not occur . 5.3.2 I ron Ana l y s i s Iron i s the most important metal in the experiment as the high concen-t r a t i o n of i ron in the t a i l i n g s and the m o b i l i t y of i ron under ac id cond i -t i o n s made i ron contaminat ion of the overburden by the t a i l i n g s a d i s t i n c t p o s s i b i 1 i t y . The i ron data analyzed from so l u t i on s c o l l e c t e d at Level C from both treatments f o r the columns which were in opera t ion f o r 9 months i s presented in F igure 5 .2 . The dotted l i n e p a r a l l e l to the x - a x i s of F igure 5.2 represents the Treatment 1 r e s u l t s . From t h i s f i g u r e i t can be concluded that the b a r r i e r in Treatment 1 was f un c t i o na l in prevent ing i ron m ig ra t i on from the t a i l i n g s in to the over-burden fo r the 9 month per iod of the experiment at Leve l s C and D. P l a t e 5.1 is a photograph of Treatment 1 column which i l l u s t r a t e s the e f f e c t i v e -ness of the b a r r i e r . Though some s u l f u r and other ma te r i a l s have p r e c i p -i t a t ed on the unders ide of the grave l fragments which were in d i r e c t contact w i th the t a i l i n g s , the f i n e s from the overburden d id not f i l l the vo ids and prov ide the necessary connect ion between the t a i l i n g s and overburden. Thus, no overburden contaminat ion occur red . As was p red i c ted and in con junc t ion wi th the changes in a c i d i t y , i ron migrated in the overburden in Treatment 2 at Level C. I t was v i s i b l y recognized by the ye l low ish-brown co lour c h a r a c t e r i s t i c of ox i d i z ed i ron as seen in P l a t e 5 .2 . The most d i s t i n c t i v e aspect of the data presented in F igu re 5.2 is the extreme v a r i a t i o n between the amount of i ron ex t rac ted from the three Treatment 2 columns, columns 10, 12, and 16. Concentrat ions of i ron in column 10 remained below 2,000 ppm fo r the en t i r e 9 months, whi le maxima of i ron of 16,600 ppm and 19,600 ppm occurred in columns 12 and 16 r e s p e c t i v e l y du r ing the f i r s t 2 months of the exper iment. - 94 -FIGURE 5.2 Monthly e x t r a c t ed i r on from overburden at Leve l C, Treatment 1 versus Treatment 2 (columns 10, 12, and 16) . TR = TREATMENT P l a t e 5.1 Treatment 1 Column wi th S u l f u r and Other Compounds P r e c i p i t a t e d on the Underside o f Gravel Fragments as a Consequence o f Excess Water ing . P l a t e 5.2 Iron Contaminat ion o f the Overburden by the T a i l i n g s i n the Treatment 2 Column, Ind ica ted by the Orange-Brown Co l o r . - 96 -These"burs t s " of i ron in columns 12 and 16 and t h e i r absence in column 10 are cons idered to be responses to the pat terns of water movement in the i n i t i a l p repara t ion of the columns fo r the exper iment. As noted in Chapter 4 . 3 . 4 , the overburden was packed in to the columns in an a i r d r i ed form w i th a c loddy s t r u c t u r e . In the i n i t i a l a pp l i c a t i o n of water to the sur face of the overburden, the water chose p re fe r red pathways in some columns, r a p i d l y f l ow ing through the overburden. This r e su l t ed in the estab l i shment of a temporary water t ab l e on the sur face of the t a i l i n g s which saturated the overburden at that l e v e l . Contaminants from the t a i l i n g s e a s i l y d i s so l ved in the temporary water t ab l e and a c i d i f i e d that water , g r e a t l y a c ce l e r a t i ng i n i t i a l contaminat ion and the contaminat ion ra te of columns 12 and 16. The columns in which the water moved s l ow l y down in to the overburden i n i t i a l l y , such as in Column 10, d i d not become saturated at the overburden t a i l i n g s boundary by sur face a pp l i c a t i o n of water . (The overburden l a t e r became sa tura ted s l ow ly by the water moving up from the water t a b l e . ) In these l a t t e r columns, t h e r e f o r e , the m ig ra t i on ra te was much lower and these l e s s contaminated columns lagged behind the more contaminated columns, at l e a s t i n i t i a l l y . Other Treatment 2 columns became contaminated at ra tes somewhere in between these extremes. The second most d i s t i n c t i v e aspect of F igu re 5.2 i s the general decrease in the amount of i ron in the s o l u t i on s ex t rac ted from columns 12 and 16 towards the l a t t e r part of the exper iment. This decrease can be i n t e r p r e t ed in three ways. One exp lanat ion may be that the excesses of i ron removed from columns 12 and 16 were not r ep l a ced , to the same ex ten t , by i r on moving up from the t a i l i n g s . Secondly, the high concent ra t ion of i ron r e f l e c t e d in the s o l u t i o n s in the e a r l y part of the exper iment, may have - 97 -migrated into the overburden above and beyond the sampling por ta l . A th i rd explanation may be that the decreasing amount of iron removed in solut ions occurred because iron was no longer in a form that could be removed from so lut ion, tliat i s , iron prec ip i ta t ion was occurring in the overburden. Evidence and deduction suggests that a l l three po s s i b i l i t i e s are responsible for the reduction of iron removed from these columns with time. F i r s t , the excesses of iron in columns 12 and 16 in the i n i t i a l bursts were probably not replaced. Following the i n i t i a l watering of the columns, the overburden remained near saturation during the experimental period, as discussed in Chapter 4, due to water, from the water tab le , cont inual ly being fed to the overburden through cap i l l a r y movement. In a near saturated condit ion, water applied on a monthly bas is , moved slowly down through the overburden at the rate of the saturated hydraulic conduct iv i ty of the overburden. Therefore, the formation of a temporary water table which occurred i n i t i a l l y due to rapid flow through the a i r -dr ied overburden and which became ac id i f i ed and contaminated with soluble iron as a result of the contact with the t a i l i n g s , was not repeated. Following the removal of the excess water at the overburden t a i l i ngs boundary by evaporation, contamination became control led by- cap i l l a r y movement of water from the t a i l i ngs into the overburden which was promoted by evaporation. The second po s s i b i l i t y that the iron continued to migrate into the overburden beyond Level C is confirmed by the acid extracted iron analysis from the so i l samples (Chapter 6.3) in which high concentrations of iron were also removed from heights above the Level C portal as well at the Level C portal (Figure 6.4(b), Chapter 6) . - 98 -P r e c i p i t a t i o n of i ron i s suggested in a number of ways. For i n s tance , i t became i n c r e a s i n g l y d i f f i c u l t wi th t ime, to ex t r a c t s o l u t i o n s from some of the sampl ing apparat i at the Level C po r t a l s in the Treatment 2 columns. When the columns were d i sman t l ed , v i s ua l examinat ion of the ceramic cup of the sampl ing apparat i i nd i ca ted they were t h i c k l y coated wi th a red-brown p r e c i p i t a t e which i s cons idered to cons i s t dominant ly of i ron compounds. P r e c i p i t a t i o n i s a l so suggested by the presence of indurated over-burden d i r e c t l y above the t a i l i n g s , which made " s o i l " sampling of the s p l i t columns, in that reg ion of the overburden, d i f f i c u l t . The same indura t i on d id not occur in the t a i l i n g s mate r i a l suggest ing that the i ndura t i on was due to the cementat ion of overburden s o i l p a r t i c l e s by i ron compounds s i m i l a r to the process of i ron pan format ion in natura l s o i l s . P r e c i p i t a t i o n was conf irmed by a quick comparison between the amount of ac id e x t r a c t ab l e i ron from the s o i l samples and the amount of t o t a l i ron added to the overburden. These samples were c o l l e c t e d at the contaminated l e v e l s in the overburden above the t a i l i n g s in the Treatment 2 columns. This qu ick t e s t compared the r a t i o , in percent , of the amount ex t rac ted from the amount added by contaminat ion at a l o c a t i on proximate t o Level C. (The va lue of the amount added by contaminat ion was obta ined by sub t r a c t i ng from the t o t a l amount of i ron in the sample, the amount of i ron na t i ve in the overburden. Inherent i ron was taken as the amount of i ron in the overburden at the l e ve l s near the top of the overburden i n Treatment 2 and the amount of i ron in the overburden in Treatment 1.) From these comparisons i t was found that an average o f 14.9% of the i r on added, was ex t rac ted in the 3 month columns, 13.0% in the 6 month columns, and 7.1% in the 9 month columns at Leve l C. - 99 -A quick comparison was then made for zinc using the same method. Of the zinc added, 37.5 to 100% of i t was removed by acid extract ion with no trends indicated. This occurred in the 3, 6, and 9 month columns suggesting that zinc was not i r revers ib l y p rec ip i t a t ing . The difference in trends between zinc and iron and the decrease in the amount of iron that could be extracted from the amount of iron added through contamination in the 9 month columns compared to the 3 and 6 month columns, suggests that iron precip i tated in the overburden over time. (The iron and zinc data used in th is quick test ar given in Appendix 4.1 and Appendix 4.2 for iron and zinc respect ive ly . These trends are.c lear ly i l l u s t r a ted in the graph of the iron and zinc tota l and extractable data (Figures 6.4(a) and (b) and Figures 6.3 (a) and (b) for iron and zinc respect ive ly, Chapter 6.) A th i rd d i s t i n c t i ve aspect of Figure 5.2 is. the tendency of the iron from a l l three columns, despite the i r i n i t i a l d i f ferences, to converge towards one concentration at roughly 2,000 ppm. This convergence is considered to represent the establishment of a steady state between the upward movement of iron from the t a i l i n g s , the continued upward movement into the overburden, and the prec ip i ta t ion of iron in the overburden. Some support for th is theory, that an equi l ibr ium could occur, may be drawn from the behaviour of iron in the t a i l i ng s in the Treatment 2 columns as presented in Figure 5.3. In Figure 5.3 high concentrations of iron were i n i t i a l l y extracted from the columns from both treatments (11,000 ppm from Treatment 1 at Level A, and 19,000 ppm from Treatment 2 at Level A. (No difference occurred between Levels A and B in the respective treatments.) 100 -, ! , , , , 0 2 4 6 8 9 TIME (MONTH) FIGURE 5.3 Monthly ex t r ac ted i r on from t a i l i n g s a t Level A, Treatment 1 versus Treatment 2. - 101 -As soon as the experiment was i n i t i a t e d , i ron in the treatments began t o behave d i f f e r e n t l y . The concent ra t ions of i ron ex t rac ted from the t a i l i n g s in the Treatment 1 columns increased with each month of the experiment i n d i c a t i n g that c ond i t i o n s , in t h i s t reatment , were promoting cont inuous chemical changes. In Treatment 2 however, the concent ra t ions of i r on removed, decreased d r a s t i c a l l y from 19,000 ppm to rough ly 6,000 ppm w i t h i n 2 months. Once t h i s i n i t i a l decrease occurred no other decreases ensued and the amounts of i ron removed from the Treatment 2 columns on a monthly bas i s remained the same. Because there was a notab le d i f f e r e n c e in behaviour between the two t reatments but not between the two l e v e l s in the t a i l i n g s , the pat terns in F igure 5.3 are cons idered to be a response to the d i f f e r en ce s in t r e a t -ments. S ince the on ly phys i ca l d i f f e r en ce between the treatments is the absence of the grave l b a r r i e r i n Treatment 2, which brought the overburden in d i r e c t contact with the t a i l i n g s , i t is assumed that the steady l eve l of i ron removed from the columns in Treatment 2 represents the estab l i shment of a steady s t a t e in the t a i l i n g s . I t is t he re fo re assumed that the t a i l i n g s have reached a steady s t a t e wi th t h e i r environment i n Treatment 2 and that a steady s t a t e i s e ven tua l l y being e s t ab l i s hed between the t a i l i n g s and overburden, at l eas t t o Leve l C in the overburden, by the 9th month. The increased concent ra t ions of i ron removed from the t a i l i n g s in the Treatment 1 columns i s assumed to be r e l a t ed to the more d i r e c t exposure of the t a i l i n g s to atmospheric c ond i t i o n s . The dry ing out of the overburden, as d i scussed in Chapter 4 . 3 , f reed a po r t i on of the pores (of water) in the overburden fo r the movement of gases. This exposure to atmospheric cond i -t i o n s i s assumed to have promoted f u r t he r ox i da t i on of the t a i l i n g s . Th is r e s u l t e d in the increased s o l u b i l i t y of i ron b r i ng ing i t i n to s o l u t i o n . - 102 -F i n a l l y in F igure 5.2 the " sp i ked" nature of the i ron data from the overburden in columns 12 and 16 should a lso be d i s cu s sed . An examinat ion of the i ron data from the overburden and from the t a i l i n g s ' in both treatments suggests that the peak-depress ion pa t te rn i s .not a response to excess water bu i l d -up at the t a i l i n g s overburden boundary as a r e s u l t of monthly water ing or to f a c t o r s such as changes in the ra te of evaporat ion or r e l a t i v e humid i t y . I f the pa t te rn had been due to excess water bu i l d -up r e s u l t i n g in more r ap i d contaminat ion of overburden through the contact of the water with the t a i l i n g s , i t i s l i k e l y that the accumulat ion of water at the boundary would have occurred randomly in the columns, depending on the v a r i a t i o n in behaviour of the columns. However the sp ikes d id not occur randomly. In a d d i t i o n , the i r r e g u l a r water movements in the overburden in the Treatment 2 columns would not have a f fec ted the movement of i ron in the t a i l i n g s in Treatment 1 which a l so was cha ra c t e r i z ed by the same peak-depress ion p a t t e r n . I f i r r e g u l a r water ing had been re spons i b l e f o r the peak-depress ion pat te rn of the i ron in the t a i l i n g s from the Treatment 1 columns, then some i n d i c a t i o n of the water ing e f f e c t would have l i k e l y been ev ident in the i ron pat te rn in s o l u t i on s ex t rac ted from the t a i l i n g in the Treatment 2 columns. As t h i s d id not occur on the Treatment 2 t a i l i n g s , the theory that the spiked pat te rn i s a response to water ing i s u n l i k e l y . As the experiment was temperature c o n t r o l l e d , temperature can be ru l ed ou t . Changes in the evaporat ion ra te due to r e l a t i v e humid i ty d i f f e r ences may be cons ide red . It i s po s s i b l e that the e f f e c t of removing s i x columns a f t e r 3 and 6 months cou ld , t h e o r e t i c a l l y cause an average reduc t ion of r e l a t i v e humid i ty as fewer columns would be supp ly ing mois ture to the - 103 -chamber atmosphere through evapora t i on . A reduc t i on in r e l a t i v e humid i ty under c o n s i s t e n t l y high temperatures could increase the evaporat ion ra te of the columns remaining in the wooden chamber. I f the end e f f e c t of removing columns from the experiment had been to promote upward movement through increased evaporat ion then increases in columns 12 and 16 would have occurred in the 4th and 7th months with the h ighest in the 7 t h . A lso the concen t ra t i ons would not have decreased dur ing the 3 month pe r i od . As is i nd i ca ted in F igure 5 .2 , the peaks occurred in the 4 t h , 6 th , and 8th months. Therefore changes in the evaporat ion r a t e , as an exp lanat ion to the peaks occu r r i ng in the i ron data in F igure 5.2 is not l i k e l y . Because the peak depress ion pat tern cannot be exp la ined by v a r i a b i l i t y due to the exper imental method, the pa t te rn i s cons idered to be r e l a t ed to the format ion and d i s s o l v i n g of metastable compounds due to changes in pH, in i ron concen t r a t i on , in the concent ra t ions of other meta l s , in o x i da t i on reduc t i on p o t e n t i a l s , and p o s s i b l y due to the a c t i v i t y of o x i d i z i n g b a c t e r i a. The format ion and breakdown of metastable compounds is a d i s t i n c t p o s s i b i l i t y as i ron can e x i s t in many forms in a m i n e r a l - s o l u t i o n system. According- to the i ron s t a b i l i t y diagram of Ga r r e l s and C h r i s t (1965) i r on should be in the i on i c form at the ac id pH l e ve l s of the overburden at Level C in the Treatment 2 columns. Accord ing to t h e i r research and under the assumption that the o x i d a t i on r educ t i on po t en t i a l (Eh) of the i ron contaminat ing the overburden is above ze ro , the i r on in the s o l u t i o n s ex t rac ted from Level C should be in the f e r rous form ( F e 2 + ) i f the pH i s less than 4 and the Eh range i s 0 to +0.75, and in the f e r r i c form (Fe3 + ) i f the Eh i s above +0.75. - 104 -Gar re l s and C h r i s t s t a t e that the dominant form of i ron in a system is based on the i o n i c a c t i v i t i e s in e qu i l i b r i um wi th the s o l i d s in the system. They s ta te tha t because these i on i c a c t i v i t i e s change so r a p i d l y with Eh and pH, i t i s r e l a t i v e l y ra re that any reg ion on an Eh-pH diagram can be asc r ibed s a t i s f a c t o r i l y to a s i n g l e ion that makes up 99% or more of t o t a l i o n i c s pe c i e s . This statement a l lows f o r the ex i s tence of severa l forms of i ron in the one set of c ond i t i o n s . Novozansky et a l . (1976) cons idered that the f e r r i c ion ( F e + 3 ) i s the dominant form found in most s o l u t i o n s below pH 3. Between pH 3 and pH 7.5 they s ta te that i ron i s most ly l i k e in the dehydroxcomplex form Fe(0H)2 + . The var ious i on i c forms may be c o e x i s t i n g and invo lved in the format ion of such compounds as the i ron ox ides , Fe203 and Fe304 under the appropr ia te Eh-pH cond i t i on s (Ga r re l s and C h r i s t , 1965) and as f e r r i c s a l t s such as Fe(0H)3 and HFe3(S04)2(0H)5 which are produced in the t a i l i n g s as a product of the ox i da t i on of p y r i t e s [Duncan and Walden, 1975 (d i scussed in Chapter 2 ) ] . Accord ing t o Gar re l s and Ch r i s t (1965) the f e r r i c s a l t s p r e c i p i t a t i n g are l i k e l y hydrous oxides of indeterminate water content of ten r e f e r r ed to as f e r r i c hydrox ides . With s u f f i c i e n t t ime, f r e s h l y p r e c i p i t a t e d f e r r i c hydrox ide w i l l convert to the much more s t ab l e hematite (or g e o t h i t e ) . However, the low pH of the overburden at Level C would most ly d i s c ou r -age the format ion of s tab le compounds. What is important is that the f e r r i c hydrox ides are cons idered t r a n s i t o r y metastab le compounds. The s o l u b i l i t y constant of f e r r i c hydroxide i s 1.1 x 1 0 " 3 6 (18°C) (CRC Handbook of Chemistry and Phy s i c s , 1978). Ferrous hydroxides are much more s o l ub l e accord ing to the s o l u b i l i t y constant given as 1.64 x 1 0 " ^ (18°C) . There-f o r e t h i s may be the dominant spec ies m ig ra t i ng in to the overburden from the = 105 -t a i l i n g s . Due to the high concent ra t i on of s u l f u r in the t a i l i n g s i t is l i k e l y tha t some i ron may be m ig ra t i ng in to the overburden as f e r rous s u l f i d e s which have a s o l u b i l i t y constant of 3.7 x 10~19 (18°C) . In r e l a t i o n to b a c t e r i a l a c t i v i t y Lundgren and Dean (1979) o v e r l a i d the na tu ra l domains of the main groups of b a c t e r i a on G a r r e l s 1 and C h r i s t ' s Eh-pH d iagram. Accord ing t o Lundgren and Dean, T h i o b a c i l l u s f e r rox i dans i s the bacter ium that is present at pH va lues below 4 and the re fo re is the spec ies tha t would have been present in the overburden. The presence of Th i obac i l 1 us f e r r ox i dans in the S u l l i v a n Mine i ron t a i l i n g s has been conf i rmed by Robbins (1979). I t i s po s s i b l e tha t the format ion and d i s s o l v i n g of metastable compounds was the re fo re in f luenced by the presence of t h i s bac te r ium. " Iron was not detected in the s o l u t i on s ex t rac ted from Level D in any of the Treatment 2 columns i n d i c a t i n g that m ig ra t i on of i ron through the 35 cm to Level D d id not occur dur ing the 9 months of ope ra t i on . 5 .3 .3 Aluminum and Copper Ana l y s i s Aluminum (F igure 5.4) and copper (F igure 5.5) behaved s i m i l a r i l y dur ing the exper iment. Because these metals appeared to be assoc ia ted chemica l l y , they are d i scussed concu r ren t l y in t h i s s e c t i o n . Aluminum and copper were not detected at Leve l s C and D in the T r ea t -ment 1 columns, as i nd i ca ted by the dotted l i n e p a r a l l e l and c l o se to the x - a x i s in both F igure 5.4 f o r aluminum and 5.5 f o r copper, nor at Leve l D in the Treatment 2 columns. This i nd i c a t e s that the b a r r i e r was e f f e c t i v e in the Treatment 1 columns and that m ig ra t ion of aluminum and copper had not progressed t o Level D dur ing the 9 months of the experiment in the Treatment 2 columns. - 106 -3 n TIME (MONTH) FIGURE 5.4 Monthly e x t r a c t ed aluminum from overburden a t Level C, Treatment 1 versus Treatment 2 (columns 10, 12, and 16) . 20n 0 2 4 6 8 9 TIME (MONTH) FIGURE 5.5 Monthly ex t r ac ted copper from overburden a t Level C, Treatment 1 versus Treatment 2 (columns 10, 12, and 16) . - 10-7 -However, con tamina t ion , by aluminum and copper, of the overburden in the treatment in which the overburden was in d i r e c t contact w i th the t a i l i n g s , d i d occur at Leve l C by the 2nd month of the exper iment. The three l i n e graphs p l o t t ed in F igure 5.4 represent the aluminum ana l y s i s of the s o l u t i o n s ex t rac ted at Level C from the 9 month Treatment 2 columns, numbered 10, 12, and 16. F igure 5.5 co r respond ing ly represents the copper da t a . The c l o se c o r r e l a t i o n of copper and aluminum is a t t r i b u t ed to the p re fe r r ed chemical a t t r a c t i o n of copper fo r aluminum as d iscussed by McBride (1978). Accord ing to h i s research r e s u l t s , McBride (1978) found that copper, as C u 2 + , had a s p e c i f i c preference f o r a lumina, po s s i b l y through bond format ion in the hydroxyl groups at low pH l e v e l s . F i gu re 5.6 is a graph of the pH data fo r the 9 month Treatment 2 columns, 10, 12, and 16, which i nd i ca te s that by the 2nd month of the experiment the pH of a l l th ree columns had decreased s u f f i c i e n t l y to a l low t h i s chemical a s s o c i a t i o n , that i s at these pH l e v e l s , copper would be in the i on i c form ( C u 2 + ) necessary to make the hydroxy l bond fo rmat i on . However, the pH was a lso appropr ia te f o r t h i s a s soc i a t i on a f t e r 1 month and was, as w e l l , appropr ia te f o r the m o b i l i t y and m ig ra t i on of these meta l s . Un l i ke i r on (F igure 5.2 page 95 ) , which migrated in high concent ra -t i o n s dur ing the 1st month of the experiment due to the maintenance of i ron s o l u b i l i t y and m o b i l i t y by the m ig ra t i ng a c i d s , aluminum and copper were not removed in s u b s t a n t i a l , de tec tab l e concent ra t ions u n t i l the 2nd and' 3rd months of the s tudy, as a l ready noted, although the degree of a c i d i t y was s u i t a b l e fo r m i g r a t i on . These r e s u l t s i nd i c a t e that aluminum (and copper) m ig ra t i on were not t i e d d i r e c t l y to pH, as was i r o n , but was a response to i t i n d i r e c t l y . - 108 -The resul ts of the tota l elemental analysis discussed in conjunction with the acid extractable data of the so i l samples in Chapter 6.3, indicate that aluminum, removed in solut ion at Level C in the Treatment 2 columns, was a product of the destruct ion, of the overburden, by migrating acids from the t a i l i ng s and was consequently released into a soluble form and in th is form, could be removed from the columns. The apparent lag in contamination may therefore, be attr ibuted to the gradual destruction of the overburden minerals which did not occur rapid ly but which took roughly 2 to 3 months. As copper mobi l i ty is low in so i l s general ly (de Haan and Liverman, 1976), the low mobi l i ty of copper was responsible for i ts absence in the otherwise contaminated overburden during the ear ly months of the experi-ment. Copper was c lose ly correlated with aluminum later in the experiment, as already noted, as i t required aluminum to enhance i ts mobi l i ty . Other aspects of the aluminum and copper data in comparison to iron are more d i f f i c u l t to expla in. As noted in section 5.2 iron migration in column 10 (Figure 5.2, page 95) was substant ia l ly retarded compared to columns 12 and 16 and these differences were attr ibuted to patterns of the migrating acids from the t a i l i n g s . Column 10 was less severely contaminated by acids in the ear ly months of the experiment compared to columns 12 and 16, probably u l t imately due to d i f f e ren t i a l watering patterns. A comparison between Figures 5.4 (aluminum) and 5.2 ( iron) indicate that the highest concentration of aluminum extracted in solut ion was 2800 ppm and i t was extracted from column 10. The column in which aluminum was removed in the lowest concentrations was column 16. By the 4th month when the aluminum peak was largest in column 10, the pH of a l l three columns - 109 -was acid enough to promote mineral destruct ion. However aluminum concen-trat ions in solut ion were much higher in column 10 than in columns 12 and 16. As the acids (Figure 5.6) did migrate more rapid ly in column 12 and 16 i t is suspected that perhaps mineral destruction should have been s l i g h t l y more severe in columns 12 and 16, instead of less, as the overburden was " s i t t i ng " in more extreme acid conditions for a longer period of time than in column 10. Therefore suppression of aluminum (and ind i rec t l y copper) by iron is suspected. Concentrations of iron greater than 10,000 ppm, which were removed in the so lut ions, are at the concentrations which can possibly affect the s o l ub i l i t i e s of other metals. (Pr ice , 1974). The tendency of aluminum, removed in so lut ion, to be almost equal in concentration in each of the Treatment 2 columns during the la t ter months of the experiment indicates a steady mineral destruction rate [of such compounds as gibbsi te (A l2O3 • 3H2O) and i t s dimorphs boehmite and disapore (Garrels and Chr i s t , 1965) or a luminio-s i1 icate minerals] in steady state with the upward migration rate of aluminum, as A l 3+ in the overburden. This upward migration was t i ed , through mineral breakdown, to the migrating acids in the overburden and is indicated by the results of the to ta l elemental and acid extractable analyses of the so i l samples (Table 6.5, Chapter 6). The large spikes in aluminum concentrations in Figure 5.4 may be attr ibuted to destruction of the overburden resul t ing in the release of high concentrations of aluminum into so lut ion, as already discussed, and/or due to the formation and destruction of metastable compounds once the aluminum was released into an ionic form. Aluminum has the tendency at low pH leve ls , to form complexes with many anions (Garrels and Chr i s t , 1965). The - 110 -i r TIME (MONTH) 9 FIGURE 5.6 pH p l o t t e d aga ins t time from overburden, column 10 (TR2) vs . column 12 (TR2) versus column 16 (TR2) (monthly e x t r a c t i o n s ) 1 4 6 8 9 TIME (MONTH) FIGURE 5.7 Monthly e x t r a c t ed aluminum from t a i l i n g s a t Leve l A, Treatment 1 versus Treatment 2, - Ill -forms of aluminum, after release and at the pH levels character i s t i c of the contaminated overburden at Level C, were A l 3 + (Garrels and Chr i s t , 1965) and hydrated aluminum, Al(H2O)3+ (Novozamsky and Beek, 1976). The concentrations of aluminum and copper, removed in the solutions at Level C were much lower than i ron. The differences in concentrations of these metals is considered to be a function of the concentration of the metals in the i r respective source materials (aluminum from the overburden and copper and iron from the t a i l i n g s ) , the chemical interact ions among the metals and the factors cont ro l l ing the i r s o l ub i l i t y and mobi l i ty . Aluminum concentrations were affected by mineral breakdown rates and chemical in teract ions . The concentrations of copper were inherently low in the t a i l i ngs and once removed from the t a i l i ngs through solutions extracted, or through upward migration, were not replenished as iron was. The steady amount of iron removed from the t a i l i ng s (Figure 5.3, page lO l ) indicated that a steady amount of soluble iron was generated and th is generated i ron, which was avai lable for upward migration, was. released as a consequence of continuing oxidation of reduced t a i l i ng s pa r t i c l e s . On the other hand, copper (and aluminum), were not greatly affected by ox idat ion. Concentrations of these metals removed in solut ion from the t a i l i ngs were i n i t i a l l y high, 960 ppm for aluminum (Treatment 1) and 39 ppm for copper (Treatment 1) but decreased rap id ly within 1 month to 200 ppm for aluminum and to 0.6 ppm for copper. The concentrations of aluminum extracted for the last 4 months of the experiment from the t a i l i ng s averaged 15 ppm (Figure 5.7) and 0.6 ppm for copper. There were no differences between Levels A and B in each of the treatments for either metals. This indicated that sumbergence of the - 112 -t a i l i n g s d id not a f f e c t the t a i l i n g s chemis t ry wi th respect to these meta l s . A smal l d i f f e r en ce d id occur between treatments as c o n s i s t e n t l y more aluminum and copper were removed from the Treatment 1 columns than the Treatment 2 columns. However, the d i f f e r ence s in treatments were smal l and were a t t r i b u t e d to greater ox i da t i on of i ron s u l f i d e s in the Treatment 1 columns which a f fec ted minera l i n t e r a c t i o n s . In summary, the rap id decrease of aluminum and copper removed from the s o l u t i o n s ex t rac ted from the t a i l i n g s i nd i c a t e s that aluminum and copper were not being c o n t i n u a l l y generated. Therefore they were not a va i l a b l e fo r extreme contaminat ion of the overburden and a l s o , once removed in s o l u t i o n , they were not r ep l en i shed . Aluminum concent ra t ions in the order of those removed from Level C in the Treatment 2 columns (F igure 5.4) are cons idered to be at l e v e l s t o x i c to vege ta t i on i f cons idered to be a v a i l a b l e f o r uptake by p l a n t s . Accord ing to Berg and Vogel (1968) aluminum ( in the s o i l ) i n the range of 53-300 ppm is t o x i c to legumes. Accord ing to de Haan and Liverman (1976) copper concent ra t i on in s o l u t i o n exceeding 0.1 ppm gene ra l l y has been reported to have an adverse e f f e c t on crop p roduc t i on . They a lso note that copper concent ra t i on in d r i n k i n g water f o r human consumption i s cons idered to be safe at l e ve l s not exceeding 1 ppm. Therefore the concent ra t ions removed in s o l u t i o n s ex t rac ted from Leve l C, Treatment 2 (F igure 5.5) are at t o x i c l e v e l s . 5.3.4 Zinc and Manganese Ana l y s i s The s o l u t i on s ex t rac ted from Level C in the Treatment 2 columns were contaminated wi th z i n c and manganese w i t h i n 1 month of ope r a t i o n . The z i n c data i s presented in F igure 5.8 and the manganese r e s u l t s are given in - 113 -3 U U «= 1 1 T 1 1 0 2 4 6 8 9 TIME (MONTH) FIGURE 5/8 Monthly e x t r a c t ed z i n c from overburden a t Level C, Treatment 1 versus Treatment 2 (columns 10, 12, and 16) . 250n ,r •- j 7 f t 0 2 4 6 8 9 TIME (MONTH) FIGURE 5.9 Monthly e x t r a c t ed manganese from overburden a t Level C, Treatment 1 versus Treatment 2 (columns 10, 12, and 16) . - 1 1 4 -Figure 5.9. The s im i l a r i t y between the f igures suggests that the factors contro l l ing the i r presence in the solutions extracted from the columns on a monthly bas is , were strongly related and yet d i f fered from those factors affect ing i ron, copper and aluminum contamination of the overburden in the Treatment 2 columns. It is suspected that pH was the main contro l l ing factor affect ing zinc and manganese behaviour. In a review by de Haan and Liverman (1976) they noted that pH is the main contro l l ing factor in zinc s o l u b i l i t y . Craze (1979) noted that zinc is avai lable in both acid and a lka l ine environments suggesting that under both types of conditions zinc is mobile. According to Marshal's (1979) revised Eh-pH s t a b i l i t y diagram for manganese, manganese ex is ts dominantly as Mn 2 + , a soluble form, at pH' below 8 . Thus any s l i gh t depression of the pH would resul t in the increased s o l ub i l i t y of zinc and manganese and thus explains i ts rapid migration in the 1st month of the experiment as well as at time zero for manganese. It should be noted that the tota l and extractable data from the so i l analysis (Chapter 6.3) indicated that the source of zinc contaminating the overburden in Treatment 2 was t he . t a i l i ng s . At the pH character i s t i c of the mine waste, zinc was in the Z n 2 + form and i t is suggested that zinc migrated with the acids from the spoil mater ia l . The analyses of the so i l samples indicate that the manganese contaminating the overburden originated in the overburden and not the t a i l i n g s and was made soluble by the acids conditions which developed in the overburden at Level C. Since manganese is dominantly in the Mn2+ form in the contaminated overburden the lag in contamination by aluminum, due to - 115 -mineral breakdown such as of gibbsite (A l2O3 • 3H2O) or boehrnite (or diaspore) (A l2O3 • H 2 O ) , was overstepped by manganese. Manganese was inherently in a form which allowed mobi l i ty and s o l ub i l i t y with any depression of the pH. Both manganese and zinc were detected, in the solutions col lected from the Treatment 2 columns at Level C, in substantial quantit ies during the 1st month of operation. Although the rates of contamination of the three columns d i f f e r s , the differences were not as substantial as what occurred in the i ron, aluminum and copper data. Since the rate of contamination of the solut ions extracted from Level C in the Treatment 2 columns was the least for column 16, the column from which high concentrations of iron were removed, some chemical depression of zinc and manganese by iron may have been responsible for the s l ight lag in contamination of column 16 by zinc and manganese. .Similar to i ron, bursts in zinc and manganese concentrations occurred early in the experiment tending towards a convergence and s t a b i l i t y for the three columns during the la t ter part of the experiment. This spiky nature of the data in the early part of the experiment is also considered to be a response to the formation and destruction of metastable compounds as well as to chemical interferences affect ing the s o l ub i l i t y of zinc and manganese. In the la t te r months of the experiment, soluble zinc and manganese1 appeared to reach an equi l ibr ium status. It is suspected that the amount of zinc migrating from the t a i l i ng s in the last part of the experiment was in steady state with the amount of zinc migrating up into the overburden and out of range of the Level C sampling por ta l . This tendency for zinc to approach a steady state may be seen in the data col lected from the t a i l i ng s (Figure 5.10). - 116 -In the t a i l i n g s , no v a r i a t i o n occurred between Leve l s A and B but d i f f e r en ce s between the treatments d i d occur . S im i l a r to i r o n , the eas i e r access of oxygen to the Treatment 1 t a i l i n g s a f fec ted the s o l u b i l i t y of z inc perhaps through the re l ease of z inc by the ox i da t i on of z i nc s u l f i d e s . S i m i l a r to i r o n , the e f f e c t of o x i da t i on of the t a i l i n g s in the Treatment 2 columns was more subdued and c on t r o l l e d as peaks in concent ra t ion d id not occur i n d i c a t i n g a steady s ta te s i t u a t i o n . Thus, z inc was cons t an t l y re leased at a steady ra te in the t a i l i n g s in the Treatment 2 columns and t he r e f o r e a constant supp ly was a v a i l a b l e f o r contaminat ion of the over-burden . The steady s ta te reached in the manganese data in the overburden at Leve l C represents the ra te of manganese brought in to s o l u t i o n , in steady s t a t e with manganese m ig ra t i ng up in to the overburden, as ac id cond i t i ons progressed up towards the sur face of the overburden. - 117 -The decreased amounts of z inc and manganese concent ra t ions with t ime, in the s o l u t i o n s c o l l e c t e d from Level C in the Treatment 2 columns, compared to the e a r l y months of the experiments are not cons idered to be r e l a t ed to p r e c i p i t a t i o n of these metals in the hard pan layer above the t a i l i n g s in the overburden. Z inc and manganese t o t a l ana l y s i s i nd i ca te s that the h ighest concent ra t i on of these metals was detected at l e ve l s above the hard pan l a y e r . A l though the overburden at Leve l C became contaminated by z i n c and manganese, these metals were not detected at Level D in the overburden. There i s some quest ion about the actua l concent ra t i on of manganese analyzed at Leve l C in the Treatment 2 columns. Accord ing to recent research on the determinat ion of t r a ce metals by atomic absorpt ion spec t ro -photometry by Mubarak et a l . (1978), high concent ra t i ons of magnesium s u l f a t e (MgS04) were found to g r e a t l y depress the manganese s i g n a l . Concent ra t ions of 500 ppm magnesium, as a s u l f a t e , reduced manganese absorb-ance by 36% and 1000 ppm magnesium reduced manganese absorbance by 45%. Th is depress ion occurred when the a i r - a c e t y l e ne f lame was used. As the concent ra t ions of magnesium at Level D in the Treatment 2 columns (d i scussed in sec t i on 5.3.7 and in F igure 5.16 page 131 ) reached 68,000 ppm and s ince magnesium at t h i s l e v e l , and the re fo re at Level C, i s cons idered to be assoc ia ted with s u l f a t e s , depress ion of the manganese s i gna l at Level C had l i k e l y occurred as manganese in t h i s study was a lso analyzed in the a i r - a c e t y l e ne f l ame. (The Level C magnesium data i s cons idered u n r e l i a b l e due to chemical i n t e r f e rences by other metals which - 118 -existed at high concentrations and in variable amounts at Level C, Treat-ment 2. As the inter fer ing metals for magnesium were not present in detect-able concentrations at Level D in the Treatment 2 columns, the magnesium data at Level D is considered r e l i a b l e ) . Mubarak et al (1978) found that u t i l i z a t i o n of the hotter nitrous-oxide (N20 - acetylene) flame corrected the interferences. F i na l l y , zinc did not migrate from the t a i l i ngs into the overburden in the Treatment 1 columns and manganese was not removed in solut ion from the Treatment 1 columns. These results are v i sua l l y portrayed in Figure 5.8 for zinc and in Figure 5.9 for manganese, by the dotted l ine which runs para l l e l to the x-axis and adjacent to i t . 5.3.5 Nickel Analysis Nickel contamination of the overburden in Treatment 1 did not occur. However nickel did contaminate the overburden at Levels C and D in Treatment 2 with maximum contamination occurring at Level C. At Level C, the migration of nickel was s imi lar to i ron, manganese and z inc , characterized by i n i t i a l bursts (with a maximum of 11 ppm from column 10) followed by a decrease (Figure 5.11). Typ ica l l y , concentrations for the three columns, though varying in the ear ly months, tended to converge towards one concentration of 4 ppm near the termination of the experiment. The bursts in the early part of the experiment suggest that nickel migrated with the acids from the t a i l i ng s into the overburden, as nickel is soluble in acid condit ions. The l eve l l i ng off of the l ine graphs toward the end of the experiment, again is considered to represent a steady state. - 119 -151 E o. - J TIME (MONTH) FIGURE 5.11 Monthly extracted nickel from overburden at Level C, Treatment 1 versus Treatment 2 (columns 10, 12, and 16 ) . The data from Levels C and D for al l nine columns in Treatment 2 are plotted individually in Figure 5.12. Figure 5.12(a), (b), and (c) represent Levels C and D for columns 14, 17 and 18 respectively which were in operation for 3 months. Figure 5.12(d), (e) and (f) represents Levels C and D for columns 11, 13 and 15 respectively, the columns which were in operation for 6 months. Figure 5.12(g), (h) and (i) represents the columns which were in operation for 9 months, numbered 10, 12, and 16. - 120 -TIME (MONTH) FIGURE 5.12 Monthly e x t r a c t ed n i c k e l from overburden a t Leve l s C and D, Treatment 1 versus Treatment 2 f o r : 3 month columns (a) 14 (b) 17 (c) 18 ; 6 month columns (d) 11 (e) 13 ( f ) 15 ; and 9 month columns (g) 10 (h) 12 ( i ) 16 - 121 -The data is presented to i l l u s t r a t e the trends and comparisons for a l l 9 months which has not been previously presented. It also i l l u s t r a t e s that nickel contamination of the overburden at Level D c lose ly para l le l s the pattern at Level C with peaks of concentration occurring at 2, 4, and 6 months. The maximum concentration of nickel detected for a l l nine Treatment 2 columns was 13 ppm at Level C and the maximum at Level D was 1.6 ppm. At Level D, the concentrations of nickel are highest in the 9th month ind icat -ing the tendency towards increasing contamination of the overburden. Concentrations at Level D are not expected to surpass the steady state level of 4 ppm as seen in Figure 5.11. Nickel in the t a i l i ngs behaved in a s imi lar manner to i ron, manganese and copper. In Treatment 1, the highest concentration of nickel recorded was 15.5 ppm in the 4th month of the experiment ( i n i t i a l l y the concentration of nickel was 8 ppm). Nickel content increased with time indicat ing that the t a i l i ngs in Treatment 1 were not in steady state and were affected by oxidation processes. Nickel in the Treatment 2 t a i l i ngs approached a plateau after 5 months. However, the behaviour of nickel deviated somewhat from iron as two small bursts of nickel occurred in the 2nd and 4th months. This indicates that establishment of steady state of nickel with the overburden occurred at a slower rate than for other metals previously discussed. De Haan and Liverman (1976) noted that normal nickel levels in so i l are equivalent to 0.05 to 0.50 ppm Ni in so lu t ion . As the nickel removed from solut ions at Level C far exceeded th is value, i t is l i k e l y that nickel may be in the tox ic range at Level C in the Treatment 2 columns. - 122 -5.3.6 Other Meta ls The s o l u t i o n s were analyzed f o r other metals such as cadmium, c oba l t , and l ead . Lead i s cons idered p a r t i c u l a r l y important as S u l l i v a n Mine is a l e ad - z i n c opera t i on and t he r e f o r e , t r aces of lead were expected in the t a i 1 i n g s . Small concent ra t ions of l e ad , cadmium and coba l t were detected at Level C in the Treatment 2 columns but not at e i t h e r l eve l in the Treatment 1 columns. In the Treatment 2 columns, the maximum concent ra t ion reached was 1.2 ppm cadmium, 2.1 ppm lead and 6.8 ppm coba l t . These metals were a lso c o n s i s t e n t l y detected at Leve-1 D wi th a maximum of 0.9 ppm cadmium, 1.0 ppm lead and 0.4 ppm c oba l t . The concent ra t i on of lead at Leve l D is s i m i l a r t o Level C suggest ing tha t the lead detected was an a r t i f a c t of the atomic absorpt ion spectropho-tometry a n a l y s i s . Therefore the data f o r Leve ls C and D, f o r 1 column from each of the three t ime per iods in Treatment 2 was p l o t t ed in F igure 5.13. In F igure 5.13 lead at both l e ve l s is very s i m i l a r in concent ra t i on and f o l l ows the peak-depress ion pa t te rn c h a r a c t e r i s t i c of data of the other metals analysed in the s o l u t i o n s ex t rac ted from the Treatment 2 columns. S ince the concent ra t i ons are low at both l e ve l s and because they are s i m i l a r i t i s l i k e l y tha t the lead data represents a n a l y t i c a l " a r t i f a c t s " r a the r than t rue va lues . The peak-depress ion pa t te rn may be the r e s u l t of the i n f l uences of the changes occu r r i ng in the columns to other meta l s , thus the lead r e s u l t s may be f a l s e . Accord ing to Ranta la and Lor ing (1973) i n te r f e rences in atomic absorpt ion spect rometry .a re common, e s p e c i a l l y with l ead . They c i t e d an example of a sample wi th a lead reading of 19 ppm, which, when read w i th - 123 -T R I T R I T R I 3 6 9 T I M E ( M O N T H ) FIGURE 5.13 Monthly ex t r ac ted lead from overburden a t Leve ls C and D, Treatment 1 versus Treatment 2 f o r : 3 month columns (TR2) (a) 14 (b) 17 (c) 18 ; 6 month columns (TR2) •(d) 11 (e) "13 ( f ) 15 ; and 9 month columns (g) 10 (h) 12 ( i ) 16. - 12 4 -a deuter ium background co r r e c t o r was <10 ppm. The deuter ium background co r r e c t o r was a l so used by Ranta la and Lor ing to co r r ec t background absorpt ion in coba l t and n i c ke l de te rm ina t i ons . The background co r r e c to r was not a v a i l a b l e f o r ana l y s i s in t h i s experiment and the re fo re the lead data i s suspect . Concent ra t ions of cadmium, coba l t , and lead were low in the t a i l i n g s s o l u t i o n s . The h ighest concent ra t ion of cadmium analyzed in the so l u t i on s ex t r a c t ed from the t a i l i n g s was 2.5 ppm, the h ighest concen t ra t i on f o r coba l t was 14 ppm and fo r l ead , 10 ppm. 5.3.7 So lub le S a l t s Due to the e x c e s s i v e l y high e l e c t r i c a l c ondu c t i v i t y measurements ( r ep resen t i ng so l ub l e s a l t content) of the t a i l i n g s , the contaminat ion of the overburden by s a l t s from the t a i l i n g s was a d i s t i n c t p o s s i b i l i t y . E l e c t r i c a l c o n d u c t i v i t y measurements of s o l u t i on s ex t rac ted from Level D, f o r Treatments 1 and 2, is presented in F igure 5.14(a) and from Level C in F igure 5 .14(b) . Some v a r i a t i o n in e l e c t r i c a l c o ndu c t i v i t y measurements occurs between Leve l s C and D in Treatment 1. The c ondu c t i v i t y at Level D, i n i t i a l l y , was rough ly 1.3 mmhos/cm at t ime zero and decreases to 0.5 mmhos/cm a f t e r 2 months, remain ing low for the re s t of the exper iment. Conduc t i v i t y measurements f o r Level C, Treatment 1, were s l i g h t l y h igher wi th a read ing of 5 mmhos/cm at t ime zero . This r e l a t i v e l y high c o n d u c t i v i t y may be the r e s u l t of contaminat ion which occurred dur ing the pack ing of the columns. However, i t was not pe r s i s t an t as the c ondu c t i v i t y decreased to 3.5 mmhos/cm a f t e r 2 months and g radua l l y decreased to FIGURE 5.14(a) TIME (MONTH) E l e c t r i c a l c ondu c t i v i t y (E .C . ) p l o t t e d aga i n s t t ime f o r overburden a t Level D. Treatment 1 versus Treatment 2 (from monthly e x t r a c t i o n s ) . TR 2 TIME (MONTH) FIGURE 5.14(b) E l e c t r i c a l c o ndu c t i v i t y (E .C . ) p l o t t e d aga ins t time f o r overburden at Level C, Treatment 1 versus Treatment 2 (from monthly e x t r a c t i o n s ) . - 1 2 6 . -2 mmhos/cm a f t e r 5 months u n t i l the te rm ina t i on of the exper iment. Conduc-t i v i t i e s of the t a i l i n g s in the order o f 18.5 mmhos/cm i n d i c a t e , in a comparison between the t a i l i n g s and the Treatment 1 overburden c ondu c t i v i t y , that the b a r r i e r prevented the upward mig ra t ion of s a l t s from the t a i l i n g s i n to the overburden. In Treatment 2, the d i r e c t contact between the overburden and the t a i l i n g s al lowed excess i ve amounts of s a l t s to migrate from the t a i l i n g s i n to the overburden. At Level C, e l e c t r i c a l c o ndu c t i v i t y measurements of 8.5 mmhos/cm at t ime zero r a p i d l y increased to 22 mmhos/cm w i t h i n 1 month. Condu c t i v i t i e s remained high f o r the f i r s t 4 months but g radua l l y decreased to 16.6 mmhos/cm a f t e r 6 months and remained at that va lue . The r e l a t i v e l y h i gh , c o ndu c t i v i t y at t ime zero i s a t t r i b u t ed to the movement of s a l t s o c cu r r i ng as soon as contact between the t a i l i n g s and overburden was made. The e l e c t r i c a l c o ndu c t i v i t y measurements at Level D [F igu re 5 .14(a) ] in the Treatment 2 columns increased at a slower ra te than at Level C as the s a l t s had to migrate through a greater depth of overburden. The conduc t i v -i t y increased throughout the exper iment, at Level D, to reach 26 mmhos/cm a f t e r 9 months. These e l e c t r i c a l c o n d u c t i v i t i e s in the Treatment 2 overburden were ex ce s s i v e , f a r exceeding the c r i t i c a l l e ve l o f 4 mmhos/cm above which c o n d u c t i v i t i e s are cons idered de l e t e r i ou s to most p l a n t s . The s a l t s migrated r a p i d l y and independent ly of the acids and metals which contam-inated the overburden at Level C. S ince the metals such as i ron and a lumi -num were not detected at Level D in the Treatment 2 columns i t is obvious tha t other m e t a l l i c ca t i ons were r e spons i b l e fo r the s a l t s . Ana l y s i s of the s o l u t i o n s ex t rac ted from Level D i nd i c a t e that ca l c i um, sodium and perhaps magnesium 'are i n vo l ved . - 127 -Calcium concentrations (Figure 5.15) did increase substant ia l l y at Level D in the Treatment 2 columns from 40 ppm at time zero to roughly 800 ppm in the la t te r part of the experiment. In Treatment 1, calcium decreased from 40 ppm to an average of 10 ppm after 2 months, as the calcium moved up in the overburden beyond Level D. A comparison between Figures 5.15 and 5.14(a) indicates a strong resemblance between the e l e c t r i c a l conduct iv i ty curves at Level D and calcium behaviour at Level D for both treatments. Sodium also increased over time from an average of 20 ppm at time zero to 250 ppm after 9 months in Treatment 2 at Level D. In Treatment 1 sodium averaged 20 ppm at time zero but decreased to 10 ppm after 1 month and remained at that level for the rest of the experiment. Magnesium behaviour d i f fered in Treatment 2 at Level D. Magnesium did not increase much above the i n i t i a l value of 200 ppm at time zero unt i l the 6th month. In the 6th month, magnesium values rose to 5,000 ppm and in the 7th month to 11,000 ppm and f i n a l l y i t rose to 62,000 pm and 69,000 ppm in the 8th and 9th months respect ive ly (Figure 5.16). It is assumed that calcium content is not responsible for these changes with respect to depres-sion or enhancement as the calcium and magnesium curves do not appear to be re l ated in any way. Magnesium at Level D, Treatment 1 (Figure 5.17) decreased over time from 50 ppm to 7 ppm in 2 months and averaged 9 ppm for the remainder of the experiment. Therefore i t appears that calcium sal ts are the dominant ions migrating from- the t a i l i ng s into the overburden with a minor component of sodium and perhaps magnesium sa l t s . The anions are considered to be dominantly - 128 -I O O C H TIME (MONTH) FIGURE 5.15 Monthly ex t r a c t ed ca lc ium from the over -burden at Level D, Treatment 1 versus Treatment 2. - 129 -0 2 4 6 8 9 TIME (MONTH) FIGURE 5.16 Monthly e x t r a c t ed magnesium from the overburden a t Level D, Treatment 2 (columns 10, 12, and 16) . -130 -) 0« j 4 g § ^ TIME (MONTH) FIGURE 5.17 Monthly e x t r a c t ed magnesium from the overburden a t Level D, Treatment 1 (columns 6, 7, and 8 ) . - 131, -s u l f a t e s . S t ru the r s (1965) i n h is s tud ies of the spec ies of s a l t s produced from the ox i da t i on of ac id mine spo i l found that s u l f a t e s were the dominant t ypes . I t i s assumed tha t the s a l t s r e spons i b l e f o r the high e l e c t r i c a l c o n d u c t i v i t y measurements at Level D are s i m i l a r to those at Level C. The data f o r ca lc ium and magnesium is not cons idered r e l i a b l e in atomic absorp-t i o n specrophotometry, at Leve l C due to heavy chemical i n t e r f e rences by contaminants e s p e c i a l l y by aluminum. This i s p a r t i c u l a r l y c r i t i c a l f o r c a l c i um . The ana l y s i s i nd i ca ted that the ca lc ium readings were depressed, i f the a i r - a c e t y l e n e f lame was used, by 0 to 70% depending on the chemical composi-t i o n of the s o l u t i o n . Magnesium was found to be depressed by rough ly 10%. The da ta , however, from Po r t a l D i s cons idered r e l i a b l e as the heavy metal contaminants had not migrated to that l e v e l . 5 .3.8 Ox ida t i on Reduct ion P o t e n t i a l s As ox i da t i on reduc t ion (redox) p o t e n t i a l s have been used to p red i c t and i n t e r p r e t minera l t rans fo rmat ions which occur in s o i l s , t h i s measurement was cons idered to be an add i t i ona l means of i d e n t i f y i n g the k inds of processes and minera l t rans fo rmat ions occu r r i ng in the overburden as a r e s u l t of the two t rea tments . B a s i c a l l y , the r e s u l t s i n d i c a t e that the overburden at Level D in both t reatments and at Level C in the Treatment 1 columns was h i gh l y ox id i zed throughout the exper iment. The contaminated overburden at Level C in the Treatment 2 columns became reduced w i t h i n 1 month of the experiment i n d i c a t -- 132 -ing that the metals contaminating the overburden were present in a reduced form ex is t ing as ions in so lu t ion . As th is is prel iminary data and the technique is s t i l l at the development stages a discussion of the resul ts is presented in Appendix 6. 5.4 Summary and Conclusions The gravel in Treatment 1 was ef fect ive as a hydrologic barr ier in preventing overburden mineral destruction and the contamination of the over-burden from acids, metals and sa l ts due to the contact with the t a i l i n g s . The overburden in Treatment 2 was severely contaminated near the overburden - t a i l i n g s interface by extreme ac id i ty , i ron, copper, z inc, manganese, aluminum, cadmium, cobalt, and n i c ke l , generally in tox ic amounts, and sa l ts which caused severe s a l i n i t y problems. The sal ts migrated rap id ly to the surface of the overburden and were ident i f i ed as of calcium, sodium and magnesium o r i g i n . Small concentrations of n i cke l , cadmium and cobalt were also detected near the upper por ta l . The data presented suggests that iron pan formation was occurring in the contaminated regions of the overburden in the columns. It was predicted that pan formation w i l l eventually migrate up to the surface with time. The analyt ica l resul ts indicate that steady state conditions were occurring between the t a i l i ng s and the overburden, and in the overburden with i ron, z inc , manganese, aluminum and n i cke l . Therefore, there would be a constant supply of these metals for upward migration. It is predicted that the metals would migrate to the surface of the overburden and the "steady state quant i t ies" noted in the data would be soluble in solutions extracted from i t . - 133 -As the source of aluminum and copper from the t a i l i n g s seemed l im i t ed i t i s p red i c ted that these metals would migrate as f a r as the ac id cond i -t i o n s would a l l ow . Contaminat ion would not be as severe due to a d i l u t i o n e f f e c t as the metals migrated up through the cover ing m a t e r i a l . The pH data i nd i c a t e s that ac ids w i l l e ven tua l l y migrate to the su r f a ce . The data a lso i nd i ca ted that extreme v a r i a b i l i t y in upward mig ra t ion of meta ls i n to overburden placed d i r e c t l y on the t a i l i n g s is a f fec ted by such f a c t o r s as packing and wa te r i ng . These d i f f e r ence s between columns, which occurred e a r l y in the exper iment, are important as i nd i c a t o r s of the kinds of v a r i a b i l i t y which can occur n a t u r a l l y in a f i e l d s i t u a t i o n . They are a l so important in the cons i de ra t i on of the treatment of the overburden in the f i e l d . For ins tance i f i r r i g a t i o n was necessary f o r vegeta t ion es tab-l ishment on the cover ing m a t e r i a l , i t may be important to con t ro l the ra te and the amount of i r r i g a t i o n water to prevent i n t e rna l p ip ing of the s o i l and the bu i l d up of excess water at the overburden- ta i1 ings boundary. The s o l u t i o n s , as such, have been important in a l l ow ing the de tec t i on of small concent ra t i ons of metals contaminat ing the overburden in the T r ea t -ment 2 columns such as n i c k e l , cadmium and coba l t which were not detected in the s o i l analyses (Chapter 6 ) . The monthly s o l u t i o n s were a lso important in i n d i c a t i n g that the meta ls were moving up in burs ts a l l ow ing the r ecogn i za t i on of movements of metals occu r r i ng at d i f f e r e n t r a t e s . This is a r e s u l t of the e f f e c t s of wa te r i ng , the format ion and breakdown of metastable compounds, the ra te of re l ease from a c i d i f i e d overburden and i n t e r a c t i v e e f f e c t s . These f a c t s would not have been recognized from the s o i l analyses da ta . - 134: -The s o l u t i o n s were a lso important in i n d i c a t i n g that copper migra t ion was s t r ong l y in f luenced by aluminum m i g r a t i o n . A l so the data i nd i ca ted that in the column environment, z i nc and manganese migrated up in to the over-burden dominant ly c on t r o l l e d by pH. The lag in aluminum mig ra t i on compared to manganese (both elements der ived from the overburden) i nd i c a t e s that the forms these metals were o r i g i n a l l y in w i t h i n the overburden were d i f f e r e n t . Manganese was re leased much more r a p i d l y than aluminum. The s o l u t i o n s were a lso important in i l l u s t r a t i n g the tendency f o r the meta ls to reach an equ i l i b r i um w i t h : m ig ra t ion from the t a i l i n g s , over-burden minera l d e s t r u c t i o n , upward m ig ra t i on to l e ve l s h igher in the overburden beyond the zone of maximum concent ra t i on and i r r e v e r s i b l e or temporary p r e c i p i t a t i o n . F i n a l l y because steady s ta te was not achieved at Level C u n t i l the l a s t 3 months of the exper iment, i t i s ev ident that the 9 months of the experiment were r equ i r ed . - 135 -6.0 Chemical Analysis of Overburden "Soi l Samples" 6.1 Introduction Overburden analyses were required to ascertain whether the overburden, in d i rect contact with the t a i l i ng s would become increasingly contaminated over distance and time. This confirmation could not be obtained from the solut ions extracted from the column sampling por ta l s . Because the overburden samples were taken from nine levels in the columns, they could provide th is information. It is understood that the degree and rate of contamination which occurred in the overburden could not be d i r e c t l y applied to the f i e l d s i tuat ion as the experiment was operated under accelerated and a r t i f i c i a l condit ions. This information was considered to be usefu l , however, as a means of f a c i l i t a t i n g an understanding of the kinds of processes that would occur i f the overburden were placed in direct contact with the mine spoi l or separated from i t by a gravel bar r ie r . The solutions col lected at Level C in the Treatment 2 columns indicated that the overburden was extremely ac id i f i ed by acids migrating from the t a i l i ng s (Chapter 5.3.1). The tota l analysis of the samples was therefore required to indicate whether increases in the concentration of the metals in the overburden, as noted in the solutions (Chapter 5) were due to upward movement of these metals from the t a i l i ngs or were a result of release through overburden destruct ion. The technique to determine the tota l analysis requires that a small sample (0.1 gram) be dissolved and di luted by a factor of 1,000. This extreme d i l u t i on of the sample masked the detection of small concentrations of contaminants at the higher less contaminated levels in the overburden. - 136 -E f f o r t s at i n c reas ing the sample s i z e , to counteract t h i s e f f e c t , in the t o t a l ana l y s i s technique were unsucces s fu l . The technique o r i g i n a l l y c a l l e d fo r sample weights of one gram. In a p i l o t s tudy, samples weighing 0.2 gm, 0.5 gm, 1.0 gm, 1.5 gms and 2 gms, d id not complete ly d i s s o l v e . The data was the re fo re not r e l i a b l e . E f f o r t s at reduc ing the d i l u t i o n f a c t o r o f 1,000 to 500 by reduc ing the f i n a l volume of the sample to 50 mis were a lso unsuccess fu l . D i l u t i o n f a c t o r reduc t i on requ i red that the sample be thorough ly washed, from the con ta ine r s in which they were d i s s o l v e d , in to b o t t l e s , con ta i n i ng bo r i c ac id p r e v i o u s l y d i s s o l v ed in water , and then washed i n to 50 ml vo lumet r i c f l a s k s . The number of washings necessary to insure that a l l of the sample was t r a n s f e r r e d . i n t o the vo lumet r i c f l a s k s requ i red water' in quan t i t i e s g rea te r than 50 m i s . Therefore i t was necessary to ca r r y out the t o t a l ana l y s i s using a 0.1 gm sample s i z e . Other means were then requ i red fo r the de tec t i on of smal l concent ra t ions of metals which had migrated in to the overburden from the t a i l i n g s . The hyd roch l o r i c ac id e x t r a c t i on technique fo r the removal of metals was used f o r t h i s purpose. In t h i s techn ique, the o r i g i n a l sample i s d i l u t e d on ly by a f a c t o r of 10. The f o l l ow i ng chapter is a d i s cu s s i on of the r e s u l t s of the chemical analyses of the overburden samples. The analyses inc luded t o t a l , ac id e x t r a c t ab l e meta l s , pH and e l e c t r i c a l c o n d u c t i v i t y . These t e s t s were cons idered to be va luab le in p rov id i ng a means of de tec t i ng any changes which occurred dur ing the column study and in i d e n t i f y i n g the kinds of processes r e spons i b l e fo r the changes. - 137 -6.2 Methods and Ma t e r i a l s 6 .2 .1 Tota l Elemental Ana l y s i s Tota l ana l y s i s was c a r r i e d out by the t e f l o n bomb method. This method was proposed by Ranta la and Lor ing (1973) but has been modi f ied at the s o i l s l a bo r a t o r y , S o i l Sc ience Department, UBC. The mod i f ied procedure was fo l l owed (Methods Manual, Pedology Labora tory , 1977). Samples were t e s t ed f o r t o t a l aluminum, z i n c , copper, i ron and manganese. Meta ls such as n i c k e l , cadmium, coba l t and lead were not present in s u f f i c i e n t concent ra t ions to be detected by t h i s method. Q u a n t i f i c a t i o n and i d e n t i f i c a t i o n of the metals was c a r r i e d out using atomic absorpt ion spectrophometry.Standards were made to volume wi th water . I t is recommended that standards match, chem i ca l l y , the sample s o l u t i on s to negate i n t e r f e rences common in the flame method. In te r fe rences are caused by f a c t o r s such as the presence of i n t e r f e r i n g ions and/or d i f f e r ences in v i s c o s i t y between l i q u i d standards and s o l u t i o n s . Test standards were t he re f o r e i n i t i a l l y made with the d i s s o l v i n g s o l u t i on s used in the t o t a l a n a l y s i s . These d i s s o l v i n g s o l u t i o n s inc luded n i t r i c , hyd roch l o r i c and b o r i c a c i d s . Hyd ro f l uo r i c ac id which is a lso requ i red in t o t a l ana l y s i s was not inc luded in the s tandards . Hyd ro f l u o r i c ac id i s an extremely dangerous chemica l . S ince i t has l i t t l e e f f e c t on the v i s c o s i t y of a s o l u t i o n because i t i s h i gh l y s o l ub l e and i s used in smal l q u an t i t i e s in the t e s t , i t s exc lus i on from the standards was not cons idered to cause any sub s t an t i a l i r r e g u l a r i t i e s in the f lame method. - 13 8 -Comparison of water based standards to these t e s t standards i nd i ca ted that in t h i s case no de tec tab le d i f f e r ence s in absorpt ion occurred f o r the metals in ques t i on . With t ime, however the bo r i c ac id p r e c i p i t a t e d in the burner . Because of t h i s , standards were made to volume wi th water and the ac ids used in d i s s o l v i n g the samples were not inc luded in the s tandards . 6 .2 .2 Hydroch lo r i c Ac i d E x t r a c t i o n The s o i l samples were ex t rac ted wi th hyd roch l o r i c ac id in order to remove any metals present in the overburden which had not i r r e v e r s i b l y p r e c i p i t a t e d . As noted, the data from t h i s ana l y s i s was cons idered important in t r a c i n g the upward mig ra t ion of small concent ra t ions of metals not detected in the t o t a l a n a l y s i s . The samples were analyzed fo r aluminum, z i n c , copper, i r o n , and manganese us ing the 0.1 N HC1 method accord ing to Black et a l . (1965). A 10:1 r a t i o of sample to ac id was used fo r l e ve l s f i v e to nine and a 20:1 r a t i o was used f o r the more contaminated samples ( l e v e l s one to f o u r , i n c l u s i v e ) t o avoid s a t u r a t i ng the e x t r a c t i o n s o l u t i o n . I t should be noted that c he l a t i ng agents, which are commonly used to e x t r a c t metals from s o i l samples, were not s u i t a b l e fo r t h i s s i t u a t i o n . Stud ies by L indsay and Norve l l (1978), Sommers and L indsay (1979), Barrau and Berg (1977) suggest that c he l a t i n g agents w i l l not produce r e l i a b l e r e s u l t s at the extremely ac id pH l e ve l s c h a r a c t e r i s t i c of the contaminated overburden in the Treatment 2 columns. Bar rau ' s and Berg 's s tudy (1977), L i ndsay ' s and N o r v e l l ' s (1978), and Sommers' and L i nd say ' s (1979) s tudy a lso suggest that the che l a t i ng agents, - 139 -i f they were used to extract metals from the contaminated sample's, had the potential of becoming saturated and therefore not capable of extract ing the metals in excess of the chelating molecules. Chelating agents have also been found to respond with time rather than "immediately", in some instances requir ing months for equ i l ib rat ion (Lindsay and Norve l l , 1978). Therefore they are not suitable as metal extract ing agents in th is experiment. The hydrochloric method has been found to be a re l i ab l e metal extractant (Salcedo and Warncke, 1979). The pH of the f i na l sample solution using 0.1 N HC1 has also been found to be consistent ly near to 2 (Salcedo and Warncke, 1979) which c lose ly resembles the pH of the contaminated overburden samples (and the t a i l i n g s ) . Therefore the hydrochloric method was considered to be suitable for extract ing metals from the overburden samples. The metals extracted in solut ion were ident i f i ed and quantif ied by atomic absorption spectrophotometry. Standards were made to volume with hydrochloric acid to a f i na l normality of 0.1. 6.2.3 Soi l Reaction The measurement of the so i l reaction (pH) was carr ied out by the standard calcium chlor ide method (Black et a l , 1965). Because of the small quantity of sample ava i lab le, the pH test with water was not included in the chemical analyses performed on the samples. The calcium chlor ide method was chosen as i t is considered to represent, more c lose ly , the in s i tu pH of the so i l solut ion (Black et a l , 1965). Also the calcium chloride method is not affected by sa l ts which are present in high concentrations in the Treatment 2 columns. - 140 -6.2.4 E l ec t r i ca l Conductivity Due to the l imited quantity of sample avai lab le, e l e c t r i ca l conductiv-i t y measurements of the overburden samples were carr ied out by the 5:1 water:soi l ra t io method (U.S. Sa l i n i t y Laboratory Sta f f , 1954) rather than by the standard saturated paste method. The 5:1 ra t io method is not ideal as the r e l i a b i l i t y of the estimate of so i l s a l i n i t y depends on the kinds of salts present. The dominate kind of sa l t predicted to be contaminating the overburden in the Treatment 2 columns is su l fa te . This sa l t has a r e l a t i v e l y low so l ub i l i t y and the apparent amount of soluble sa l t w i l l depend on the soi l :water r a t i o . Ideal ly the conduct iv i ty ra t io should be inversely proportional to the moisture content of the so i l at ext ract ion, i f the tota l dissolved salts are independent of the moisture content at which extraction is made. However the more di luted method is considered general ly acceptable in s i tuat ions of l imited sample s ize (U.S. Sa l i n i t y Laboratory Staf f , 1954). The USDA s a l i n i t y handbook on sal ine and a l ka l i s o i l s (U.S. Sa l i n i t y Laboratory Staf f , 1969) provides a graph for 1:1 and 1:5 extracts for estimating sa l t content from e l e c t r i c a l conduct iv i ty measurements. A comparison of the measurements of the samples (Chapter 6.3) to the data provided from the solut ions extracted from the portals (Chapter 5.3.6) indicates the difference between a saturated solution and the 1:5 extract for the sal ts contaminating the overburden. 6.2.5 S t a t i s t i c a l Analysis S t a t i s t i c a l tests were used as an aid to interpret ing the results from the to ta l elemental analys is, acid extract ions, pH and e l e c t r i c a l conduct iv i ty measurements from the overburden samples in both treatments. - 141 -The t o t a l and ac id e x t r a c t ab l e data were subjected to the ana l y s i s of va r i ance t e s t in order to answer severa l ques t i ons . F i r s t the data from the two t rea tments , the three t ime pe r i ods , the nine he i gh t s , and the three r e p l i c a t i o n s y i e l d ed 162 obse r va t i on s . The main quest ion to be answered i s why are not a l l of these observat ions the same? In answer, the amount of v a r i a b i l i t y which occurs between the observat ions may be a t t r i b u t ed to e r r o r , to d i f f e r en ce s in the t rea tments , to t ime, and to height according to the f o l l ow i ng f i x ed e f f e c t s model: y u m = ! i + * i + 3 j + Y k + ^ e i j + ry ) i k + ) j k + a ^ i j k + E i j k i where y represents the actua l va lue of the ob s e r v a t i o n ,y represents the mean fo r a l l observat ions and xi = t reatments B j = he ights Yk = t imes § i j k l = e r ™ r and i = 1,A A = number of t reatments = 2 j = 1,B B = number of he ights = 9 k = 1,C C = number of t ime per iods = 3 1 = 1,N N = number -of dup l i c a t e s = 3 and the remaining terms represent combinat ions of the above terms in two-and three-way i n t e r a c t i o n s . Accord ing to t h i s model, «j=i + <*i=2 = z e ro , e t c . as these terms represent dev i a t i ons from the mean. - 142 -In the ana l y s i s of va r i ance , the key point is that i f there are no d i f f e r en ce s among the groups, then the between-groups va r i ance and the w i th in -g roup var iance w i l l be approx imate ly equa l . The more the value of between-groups var iance exceeds the w i th in -g roup va r i ance , the greater i s the p r o b a b i l i t y that the groups represent d i f f e r e n t popu l a t i ons . This is summed up by the F f a c t o r : F = va r i ance between groups va r i ance w i t h i n groups The nu l l hypotheses of the experiment are the re fo re as f o l l ows : Ho i ; " l = c2 = 0 H02; S i = 82 = B3» = Sg = 0 H03; ' . ^ 1 3]_ = B2---c2 = 0 H 0 4 ; YX = y 2 = y 3 = 0 H 0 5 ; -1 Yi = < x 1 y 2 . . . . - 2 y 3 = 0 Ho 6 ; 81 Yi = 3i Y 2 89 Y 3 = 0 H 0 7 ; «i 8l Ti = °=i 81 Y2 2^ 39 Y 3 = 0 The terms in the model represent the source of var iance in the ana l y s i s o f var iance s t a t i s t i c a l a n a l y s i s . The UBC Anovar Analyses of Var iance and Covar iance s t a t i s t i c a l package was used. In the a n a l y s i s , the var iance a t t r i b u t ed to each term in the model was tes ted f o r s i g n i f i c a n c e by comparison to the e r ro r term. Because the e r ro r term represents a dev i a t i on around a mean and is c a l c u l a t ed from a l l r e p l i c a t i o n s in the ana l y s i s of va r i ance , the e r ro r term was extremely l a rge in c e r t a i n i n s t ances . For example, i t was s i g n i f i c a n t l y amp l i f i ed by the extreme amount of v a r i a t i o n which occurred at the contaminated l e v e l s , between i n d i v i d u a l Treatment 2 columns, compared to the uncontaminated l e ve l s f o r the same columns. S p e c i f i c a l l y , the concent ra t ions of t o t a l i ron at Level 1 in the Treatment 2 columns fo r 9 months were 80,000 ppm, 51,000 ppm and 51,000 ppm and f o r Level 9 were co r respond ing l y 31,000 ppm, 27,000 ppm and 27,000 ppm. Since t h i s amount of v a r i a t i o n between r e p l i c a t e s was incorporated in to the e r ro r term and a l l other sources of v a r i a t i o n were compared to i t as a t e s t f o r s i g n i f i c a n c e , the t rue s i g n i f i c a n c e of some sources of v a r i a t i o n was d imin ished by the l a rge r e r ro r te rm. There fo re , the data was transformed by t ak i ng the natura l log of each obse r va t i on . This reduced the h e t e r o s c e d a s t i c i t y . The Newman-Keuls mu l t i p l e range t e s t was a lso used in the a n a l y s i s . For example, in ins tances where s i g n i f i c a n t var iance was a t t r i b u t ed to t ime , t h i s t e s t was use fu l in i n d i c a t i n g i f the 3 month per iod was s i g n i f i c a n t l y d i f f e r e n t from the 6 month per iod and/or 9 month per iod or the 6 from the 3 and 9 month pe r i ods . This t e s t is a f o l l ow up t e s t from the s i g n i f i c a n c e t e s t , and i t t e s t s the s i g n i f i c a n c e between i n d i v i d ua l means and subsequent ly groups and ranks them acco rd i ng l y . The ana l y s i s of va r i ance i nd i c a t e s whether the f a c t o r , he igh t , i s s i g n i f i c a n t or not but does not i nd i c a t e the l eve l to which the i n d i v i d ua l contaminants m ig ra ted . The Mann-Whitney U-Test was used fo r t h i s purpose. This t e s t ranks the values to be tes ted from lowest to h ighest wh i le r e t a i n i n g a l abe l to i n d i c a t e what group each score came f rom. The value of U r e f l e c t s the number of t imes scores for one group precede scores fo r the other group in t h i s d i s t r i b u t i o n . A p r o b a b i l i t y va lue i s then determined by - 14 4 -the appropr ia te t a b l e . Th is t e s t has 95% o f the power of a t - t e s t where the assumptions of a t - t e s t are met. It uses ranks, and makes no assumptions about no rma l i t y or homogeneity of va r i ance . 6.3 Resu l t s and D i scuss ion The ana l y s i s of the samples i nd i ca ted that l i t t l e change occurred in the overburden in the Treatment 1 columns, and as p r ed i c t ed , the overburden in the Treatment 2 columns became contaminated by the d i r e c t contact w i th the mine waste m a t e r i a l . The r e s u l t s , in terms of s i g n i f i c a n c e , of the ana l y s i s of var iance t e s t (ANOVA) f o r the t o t a l e lemental d i g e s t i o n s , f o r pH and fo r e l e c t r i c a l c o n d u c t i v i t y measurements are presented in Table 6 . 1 . The " s i g n i f i c a n c e " r e s u l t s f o r the ' a v a i l a b l e ' a c id e x t r a c t ab l e metals are given in Table 6 . 2 . The ANOVA t e s t i nd i ca ted tha t s i g n i f i c a n t d i f f e r en ce occurred in the 162 observat ions due to t rea tment , he igh t , and t rea tment -he ight i n t e r a c t i o n s f o r most of the v a r i a b l e s presented in the t a b l e s . However, the high s i g n i f i c a n c e va lues , fo r example due to he igh t , suggest that height is a s i g n i f i c a n t f a c t o r in both t rea tments . This occurs as a r e s u l t of the man ipu la t ion of the data by the ANOVA t e s t . In t h i s t e s t , f o r example, the three r e p l i c a t e s at Level 1 from each treatment are t r ea ted as one group and are compared to the s i x r e p l i c a t e s at Level 6 ( three from each t reatment) which have been s i m i l a r l y grouped. When the o v e r a l l comparisons of the means between the two groups are made, the groups are found to be s i g n i f i c a n t l y d i f f e r e n t . The high concent ra t ions of - 1 4 5 -Table 6.1 S i g n i f i c a n c e r e s u l t s from the Ana l y s i s of Var iance t e s t f o r the t o t a l e lemental a na l y s i s , pH, and e l e c t r i c a l c o ndu c t i v i t y of the overburden. SOURCE OF VARIANCE A l Zn Cu Fe Mn PH EC TREATMENT ** ** ** ** ** ** HEIGHT ** ** * ** ** ** ** TREATMENT X HEIGHT ** ** ** ** ** ** ** TIME ** ** * * TREATMENT X TIME * HEIGHT X TIME * ** TREATMENT X HEIGHT X TIME ** ** Note: ** S i g n i f i c a n c e l eve l 99% * S i g n i f i c a n c e l e ve l 95% Table 6.2 S i g n i f i c a n c e r e s u l t s from the Ana l y s i s o f Var iance t e s t fo r the ac id e x t r a c t ab l e ana l y s i s of the overburden. SOURCE OF VARIANCE A l Zn Cu Fe Mn TREATMENT ** ** ** ** ** HEIGHT ** ** * ** ** TREATMENT X HEIGHT ** ** ** ** ** TIME TREATMENT X TIME ** ** ** HEIGHT X TIME * * TREATMENT X HEIGHT X TIME Note: ** S i g n i f i c a n c e l eve l 99% * S i g n i f i c a n c e l e v e l 95% - 146 -a contaminant at Level 1, Treatment 2, t he re fo re i n t e r f e r e s wi th the s i g n i f i c a n c e measurement of the height f a c t o r in the Treatment 1 columns due to the averaging of a l l Level 1 da t a . Because of t h i s , the ANOVA t e s t was run on the t o t a l elemental data f o r each treatment s epa r a t e l y . The s i g n i f i c a n c e r e s u l t s from t h i s exe r c i se fo r Treatment 1 are given i n Table 6.3 and i n Table 6.4 f o r Treatment 2. In Table 6.3 i t can be seen tha t he ight was not s i g n i f i c a n t fo r aluminum, z i n c , i r o n , and manganese in the Treatment 1 columns. However, the s i g n i f i c a n c e in r e l a t i o n to copper, pH, and e l e c t r i c a l c o n d u c t i v i t y cannot be e a s i l y exp la ined fo r t h i s t rea tment . The Newman-Keul's t e s t d id not i nd i c a t e any trends in the grouping or rank ing of he ights f o r copper in the Treatment 1 columns i e . copper concent ra t i ons were not s i g n i f i c a n t l y d i f f e r e n t between Leve l s 1 and 9 or between 2 and 8 at the 95% conf idence l e v e l . The mean pH va lue was s l i g h t l y lower at Level 1 compared t o Level 9, changing from 7.49 at Level 1 to 7.69 at Level 9 . The e l e c t r i c a l c o ndu c t i v i t y measurements decreased from a mean of 282 micomohos/cm at Level -1 to 141 micromohos at Level 9. D i r e c t contact with the minera l s in the gravel may be re spons ib l e for the pH and e l e c t r i c a l c o ndu c t i v i t y changes or , the overburden, in contact wi th the g r a v e l , may have been contaminated dur ing the o r i g i n a l packing ope r a t i on . As the mean change in pH was smal l (0 .2 pH un i t s ) and the mean change in e l e c t r i c a l c o n d u c t i v i t y was a lso smal l ( l e s s than 200 micromohos/cm or 0.2 mmhos/cm), contaminat ion by d i r e c t contact wi th the t a i l i n g s i s not cons idered to be r e spons i b l e fo r the these r e s u l t s . Time was s i g n i f i c a n t i n Treatment 1 f o r severa l of the v a r i a b l e s (Table 6 . 3 ) . Aluminum, manganese, and z i n c increased s l i g h t l y with time and copper decreased. However, the d i f f e r en ce s are m in ima l . For example, manganese 147 -Table 6.3 S i g n i f i c a n c e r e s u l t s from the Ana l y s i s of Var iance t e s t f o r the t o t a l e lemental a na l y s i s , pH, and e l e c t r i c a l c o ndu c t i v i t y of the overburden in Treatment 1. SOURCE Al Zn Cu Fe Mn PH EC HEIGHT ** * ** TIME ** 1,2,3 ** 1,2;3 ** 3 ,2 ;2 ,1 ** 1,2;3 ** 3,2;1 HEIGHT X TIME ** Note: ** S i g n i f i c a n c e l eve l to 99% * S i g n i f i c a n c e l eve l t o 95% Table 6.4 S i g n i f i c a n c e r e s u l t s from the Ana l y s i s o f Var iance t e s t fo r the t o t a l e lemental a n a l y s i s , pH, and e l e c t r i c a l c ondu c t i v i t y of the overburden in Treatment 2. SOURCE Al Zn Cu Fe Mn pH EC HEIGHT ** ** ** ** ** ** ** TIME * 1;3,2 ** 1,2;3 HEIGHT X TIME * ** Note: ** S i g n i f i c a n c e l eve l to 99% * S i g n i f i c a n c e l eve l t o 95% - 148 -i nc reased from a mean of 0.46 ppm fo r the 3 month columns to 0.47 ppm for the 6 months columns and to 0.49 ppm f o r the 9 months columns (as read on the o r i g i n a l d i g e s t i on s o l u t i o n s i e . before they were m u l t i p l i e d by the d i l u t i o n f a c t o r ) . S i m i l a r l y , aluminum increased from a mean of 53 ppm to 54 ppm t o ' 56 ppm. Changes in copper and z inc concent ra t ions were as comparat i ve ly small and t h e r e f o r e , are a lso not a t t r i b u t ed to contaminat ion from the t a i l i n g s . The r e s u l t s presented in Table 6.1 and 6.2 i nd i c a t e that t reatment , he i gh t , and the t rea tment -he ight f a c t o r a f fec ted s i g n i f i c a n t d i f f e r ences in a l l v a r i a b l e s except manganese. Manganese was the on ly v a r i a b l e presented f o r which d i f f e r en ce s in the treatments were not s i g n i f i c a n t . A graph of the manganese data r e s u l t i n g from the elemental ana l y s i s (F igure 6 .1(a) ) suggests the reason fo r the anomaly. In F igure 6 . 1 ( a ) , Level 1 represents the sampling l o c a t i o n most proximate to the overburden- ta i1 ings boundary. The dotted l i n e represents the concent ra t ions of manganese in the Treatment 1 overburden. At Leve l s 1 and 2, the concent ra t i on of manganese fo r a l l Treatment 2 columns was less than in the noncontaminated overburden of the Treatment 1 columns. Th is suggests that the ac id cond i t i ons e x i s t i n g s at Leve ls 1 and 2 in the Treatment 2 columns e f f e c ted minera l breakdown of the overburden and the r e l ea se of manganese in to a so l ub l e form. Therefore the source of , or at l eas t a great p ropor t i on of the increased concent ra t ions of manganese at the h igher l e v e l s (Leve l s 4 to 6 ) , was the overburden at Leve l s 1 to 3 and not the mine t a i 1 i ngs . The same pat te rn i s ev ident in the manganese e x t r a c t i on data which is p l o t t ed in F igure 6 . 1 ( b ) . The s i m i l a r i t y of F igu res 6.1(a) and 6.1(b) i nd i c a t e s that a high p ropor t ion of the manganese, which migra ted , remained •- 149 -CM O x E a. a. u) cn ui z < o 2 < 9(TR 2) 3(TR 2) FIGURE 6.1(a) Tota l e lemental manganese from the over -burden, Treatment 1 versus Treatment 2 (TR2) f o r 3, 6, and 9 month t ime pe r i od s . CM g E D . O . Ld cn z < FIGURE 6.1(b) E x t r a c t ab l e manganese from overburden Treatment 1 versus Treatment 2 (TR2) f o r 3, 6, and 9 month time pe r i od s . 150 -so l ub l e as i t was removed by the e x t r a c t i on techn ique . As a r e s u l t of the re l ease of manganese by minera l de s t r u c t i on in the Treatment 2 overburden •and i t s consequent ia l e x t r a c t ab l e s t a t e , treatment became a s i g n i f i c a n t f a c t o r in the managanese e x t r a c t i o n data (Table 6.2) although i t was not in the t o t a l ana l y s i s s t a t i s t i c a l r e s u l t s . Time, as a f a c t o r , was of cons ide rab le i n t e r e s t in the exper iment, e s p e c i a l l y wi th respect to Treatment 2, as changes with t ime, though a c ce l e r a t ed , could be t ransposed to a f i e l d s i t u a t i o n and trends of cont inued upward mig ra t ion would s i g n i f y eventual complete contaminat ion of the overburden i f p laced d i r e c t l y on the t a i l i n g s . However, t ime was not a s i g n i f i c a n t source of va r i ance f o r most of the v a r i a b l e s s tud ied in Treatment 2. For example, the amount of manganese ex t rac ted and changes in pH and e l e c t r i c a l c o n d u c t i v i t y were not s i g n i f i c a n t l y a f fec ted by time dur ing the exper imenta l per iod (Tables 6 . 1 , 6 .2 , and 6.4) The migra t ion of ac ids and s a l t s from the t a i l i n g s in to the overburden and the de s t r u c t i on of overburden minera l s and the consequental r e l ease of manganese appears to have occurred r a p i d l y in the Treatment 2 columns. With in the 3 months the ra te of m ig ra t i on and minera l de s t r u c t i on was m in ima l . Because contaminat ion ra tes in the three sets of columns were a l so v a r i a b l e depending on the behaviour of the i n d i v i d ua l columns any d i f f e r ence s due to t ime were averaged out . V a r i a t i o n in the degree of contaminat ion t y p i c a l in the Treatment 2 columns is i l l u s t r a t e d by a comparison, of the pH l e v e l s from the i n d i v i d ua l columns, f o r the three time pe r i ods , to a summation graph. F igu re 6.2(a) represents the pH data fo r the three Treatment 2 columns which were in opera t ion f o r 3 months. F igure 6.2(b) s i m i l a r l y represents the 6 month columns and F igure 6 . 2 ( c ) , the 9 month columns. - 151 -2^  3 MONTHS 18-T — i 1~ 5 3 LEVEL FIGURE 6.2(a) pH versus . l e ve l i n overburden, Treatment 2, 3 month columns (columns 14, 17, 18) . FIGURE 6.2(b) phT versus l e v e l i n overburden, Treatment 2, 6 month columns (columns 11 , 13, 15) . - 152 -4H 2H 0-9 MONTHS T 1 i " LEVEL FIGURE 6 .2(c) pH versus l e ve l i n overburden; Treatment 2, 9 month columns (columns 10, 12, 16) . 4^ 2H 3 vs 6vs9 MONTHS T 1 5" LEVEL FIGURE 6.2(d) oH versus leve l , i n overburden, Treatment 2, 3 vs 6 vs 9 month columns. - 15 3 -Column 17 in F igure 6.2(a) was as contaminated as column 13, in F igure 6.2(b) and more contaminated by ac ids than columns 12 and 16 from the 9 month per iod (F igure 6 . 2 ( c ) . When averaged out [F igure 6 .2 (d ) ] the m ig ra t i on of a c i d s , as i nd i ca ted by pH, over lapped in the 6 and 9 month per iods with the 3 month columns being less contaminated. Thus the o v e r a l l f a c t o r of t ime was s t a t i s t i c a l l y i n s i g n i f i c a n t . Time i s s i g n i f i c a n t fo r aluminum in the Treatment 2 t o t a l elemental d i g e s t i o n s (Table 6.4) but an examinat ion of the mean aluminum concent ra -t i o n s i nd i c a t e s that the aluminum content in the Treatment 2 columns is less than in Treatment 1. The decrease in the t o t a l amount of aluminum in the overburden in the contaminated columns may be a r e s u l t of the removal of aluminum through the monthly e x t r a c t i o n s . I t should be noted that in F igure 5.7 (Chapter 5) the concent ra t ion of aluminum removed in s o l u t i o n was cons ide rab l y h igher in column 10 than in column 16 and the t o t a l amount of aluminum was less in column 10 (51,888 ppm) than in column 16 (53,666 ppm) (Refer to the t o t a l e lemental data in Appendix 5 .1 . ) Th is suggests that more aluminum was removed from column 10 as more so l ub l e aluminum was a v a i l a b l e through minera l breakdown. (Note in F igure 6 .2(c) the ac id cond i t i ons are more severe in column 10 than column 16 and thus there is a po t en t i a l f o r greater minera l breakdown in column 10) . There fore , the source of h igher concent ra t ions of aluminum (and manga-nese) i n the upper l e ve l s in the overburden in the Treatment 2 columns are l i k e l y to be from the overburden minera l s and not the S u l l i v a n i ron t a i 1 i ngs . - 154 -Zinc i s the on ly v a r i a b l e s tud ied in the experiment in which migra t ion from the t a i l i n g s i n to the overburden increased s i g n i f i c a n t l y wi th t ime (Table 6 . 4 ) . The t rend of z i nc to increase in height and concent ra t i on with t ime is i l l u s t r a t e d by the t o t a l elemental data p l o t t ed in F igu re 6 . 3 ( a ) . The dotted l i n e p a r a l l e l to the x - ax i s represents t o t a l z i nc • from the overburden i n Treatment 1. The ac id e x t r a c t ab l e z i nc is p l o t t ed in F igure 6 . 3 ( b ) . From F igures 6 .3(a) and (b) i t is ev ident than z i n c concent ra t ions were lower near the overburden t a i l i n g s boundary than at adjacent h igher l e v e l s . Th is suggests that the extreme ac id cond i t i ons of the h i gh l y contaminated overburden promoted cont inuous movement through that r eg i on , beyond i t and upward as z i nc migrated con t inuous l y in height u n t i l a l k a l i n e pH cond i t i ons reduced i t s s o l u b i l i t y . The high m o b i l i t y of z i nc under ac id cond i t i ons i s we l l documented. De Hann and Zwerman (1976), in t h e i r rev iew, note that the main c o n t r o l l i n g f a c t o r in z i n c s o l u b i l i t y i s pH and accord ing t o L indsay (1973) z i n c is in the so l ub l e Zn^ + form up to pH 7 .7 . This may exp la in the f a c t that z inc m ig ra t i on [F igu res 6.3(a) and (b ) ] exceeded (detected) ac id m ig ra t i on [F igu re 6 . 2 ( d ) ] . The tendency of z i nc to migrate and concentrate as i t d id in the higher l e v e l s in the overburden is c h a r a c t e r i s t i c as z i n c a c t i v i t y decreases 100- fo ld fo r each un i t increase in pH. I t should be recognized tha t the amount of z i n c removed (by the e x t r a c t i o n techn ique) [F igure 6 .3 (b ) ] was s i m i l a r to the amount of z i nc added to the overburden through contamina t ion . This suggests that the z i n c was not i r r e v e r s i b l y p r e c i p i t a t e d . I t could cont inue migra t ion i f ac id cond i t i ons deve loped. - 155 -LEVEL FIGURE 6.3(a) Tota l e lemental z i n c from overburden, Treatment 1 versus Treatment 2 (TR2) f o r 3, 6, and 9 month time pe r i ods . 6 i LEVEL FIGURE 6.3(b) E x t r a c t ab l e z i n c from overburden, Treatment 1 versus Treatment 2 (TR2) f o r 3, 6, and 9 month t ime pe r i ods . - 156 -The temporary type of p r e c i p i t a t i o n of z inc was not c h a r a c t e r i s t i c of m ig ra t i ng i r o n . F igure 6 .4(a) i s a p l o t of the i ron data from the t o t a l e lemental d i g e s t i on and i s averaged fo r each of the three t ime pe r i od s . The dotted l i n e , cons i s t en t wi th prev ious f i g u r e s presented, represents ' t o t a l ' i ron in the overburden in the Treatment 1 columns. F igure 6.4(b) represents the e x t r a c t ab l e i ron from the same columns and i s drawn at the same sca l e as F igure 6 . 4 ( a ) . A comparison between F igures 6 .4(a) and (b) i nd i ca te s that on ly a smal l p ropo r t i on of the i ron ( rough ly 15.5% a f t e r 3 months and 8.5% a f t e r 6 and 9 months) which had been added to the overburden, through upward m ig ra t i on from the t a i l i n g s , could be e x t r a c t ed . A l so va r i an t to z i nc [F igures 6.3(a) and ( b ) ] , the h ighest concent ra t i on of i r o n , both t o t a l and e x t r a c t a b l e , occurred at the sampling l o ca t i on s most proximate to the overburden- ta i1 fngs boundary. These two c h a r a c t e r i s t i c s , a t yp i c a l of a l l other metals s t ud i ed , (copper, aluminum, manganese, and z i n c ) suggest that i ron i r r e v e r s i b l y p r e c i p i t a t e d in the overburden desp i t e the presence of extreme concent ra -t i o n s of ac ids at those l o c a t i o n s . I t is p red i c ted that i ron ox ides , hydrox ides or amorphous i ron were c r y s t a l l i z i n g and consequent ly cementing the minera l p a r t i c l e s of the overburden. During m ig r a t i on , the i ron is gene ra l l y cons idered to be in the F e 2 + form (Gar re l s and C h r i s t , 1965). However, Duncan and Walden (1965) note tha t i ron hydrox ides (Fe(0H)3) and j a r o s i t e - t y p e s of m inera l s (AFe3(SC>4)2 (0H)5, A = H+,- K + , Na + e t c . ) are products along wi th s u l f u r i c a c i d , of the ox i da t i on of i ron s u l f i d e s . This suggests that these products are s t ab l e under ac id cond i t i ons s i m i l a r to those of the t a i l i n g s . Therefore i t is p red i c t ed tha t these products may a lso be forming or m ig ra t i ng in to the - 157 -LEVEL FIGURE 6.4(b) E x t r a c t ab l e i r on from overburden, Treatment 1 versus Treatment 2 (TR2) f o r 3, 6, and 9 month pe r i ods . - 158 -overburden and prec ip i ta t ing at the acid pH's values of the contaminated overburden. The yel lowish brown color, character i s t i c of j a ros i t e , was v i s i b l e in the contaminated overburden (Plate 6.1) suggesting that ja ros i te type of minerals may be present. The formation of an iron pan through prec ip i ta t ion of iron is supported by the endurated state of roughly 8 cm of overburden d i r e c t l y above the overburden ta i l i ngs boundary. In the s t a t i s t i c a l analys is, iron is the only element for which time was s ign i f i cant in Table 6.1 and not s ign i f i cant in Table 6.3 and Table 6.4, which represent the analysis of the data from the two treatments separately. It is of interest to note that time was s ign i f i cant to the 90% confidence level in the test run of the Treatment 2 data analyzed separately from the Treatment 1 column. The Treatment 1 data, in combination with the Treatment 2 data had the effect of ra is ing the confidence level to 95% in Table 6.1. In the Treatment 2 columns, the mean iron values (averaged for a l l levels) ranged from 36,666 ppm to 40,481 ppm to 37,370 ppm for the 3, 6 and 9 months, respect ive ly . Therefore migration of iron occurred rap id ly and probably within the f i r s t 3 month period of the experiment after which migration into the overburden was minimal. The concentrations of tota l iron are a l l very s imi lar for the 3, 6 and 9 month columns and yet more iron was extracted from the 3 month (as noted 15.5% after 3 months, 8.5% after 6 and 9 months). This suggests that more than half of the iron that was to prec ip i tate (which was roughly 90%) prec ip i tated in the f i r s t 3 months of the experiment, and v i r t u a l l y a l l of the iron that was to prec ip i ta te , was precip i tated by 6 months. The amount of iron which did migrate was substantial as the mean tota l iron concentration of the uncontaminated overburden was 27,555 ppm, thus ind icat ing a movement of roughly 12,000 ppm of iron into the overburden. - 159 -- 160 -From the data presented graphica l ly , i t is obvious that despite the 9 month period and the species of metals studied, migration occurred to Level 4 or - 5 which represents a distance of 20 to 25 cm. The l im i t on the distance t rave l led by the metals is considered to be dominantly a function of pH. The migration of acids was control led by several factors inherent in the experimental design such as the rate of accelerated evaporation, the amount of water added to the columns i n i t i a l l y and on a monthly basis, the pa r t i c l e s ize of the overburden materials (af fect ing porosity and cap i l l a r y movement), packing of the overburden, etc. Therefore, depending on such factors as c l imat ic conditions of the f i e l d s i tuat ion and the method of applying the overburden, etc. the level of.migration of the metals would be correspondingly affected in the f i e l d . A l l of- the metals are predicted to have migrated i n i t i a l l y in the i r ionic form (Garrels and Chr i s t , 1965) as a consideration of the pH of the t a i l i n g s (pH 2.2). As the acids became d i lu ted , with distance from the t a i l i n g s , the a lka l ine pH of the overburden neutral ized the acids and caused the i n so l ub i l i t y of the metals. I n so l ub i l i t y of zinc may occur through direct absorption of zinc on the carbonates in the overburden. Bar-Yoesf (1979) found that carbonate content affected zinc absorption and th is began at pH 5.5 and increased with pH and carbonate content. Copper is predicted to form Cu(0H)2 or Cu2(0H)2C03 in calcareous so i l s (Cavallaro and McBride, 1978) as well as oxides such as CuO and CU2O at higher pH levels (Garrels and Chr i s t , 1965). Copper at extremely acid pH values was l i k e l y associated with sulfur as CuS and iron as CuFeS2 (Garrels and Chr i s t , 1965) . - 161 -Accord ing to Ga r re l s and C h r i s t (1965) i ron can a lso e x i s t as a carbonate (FeCG^) in the neut ra l and ac id pH range. There fore , i ron may a l so be in the form of a carbonate at the higher pH l e v e l s in the over-burden. Aluminum probably ex i s t ed as A l 3 + in the ac id cond i t i ons of the contaminated overburden and formed a v a r i e t y of i ons . Aluminum tends to form complexes with many ions (Ga r re l s and C h r i s t , 1965) e s p e c i a l l y with copper (McBr ide, 1979). At a pH above 5.1 aluminum was l i k e l y reformed as A1203-3H20 and A ^ O s - ^ O as suggested by Ga r r e l s and Ch r i s t (1965). At the high pH l e v e l s in the overburden in the Treatment 2 columns, manganese probably sorbed to preformed MnC"2 as Mn (II)-Mn02 or to Fe203 (Ma r s ha l l , 1979). Marsha l l (1979) s t a t e s that the manganese oxides which form s low ly cons i s t of mixtures of d i f f e r n t forms of manganese ranging from Mn(II) t o Mn(IV) . Table 6 . 5 ( a ) - ( f ) are the Mann Whitney U-Test s i g n i f i c a n c e r e s u l t s f o r the t o t a l and e x t r a c t ab l e da ta , pH and e l e c t r i c a l c o ndu c t i v i t y t e s t s . The symbol x+ represents l e ve l s in the columns at which the Treatment 2 va lues of the i n d i v i d u a l v a r i ab l e s were s i g n i f i c a n t l y g rea te r , at the 95% l e v e l , from the correspond ing Treatment 1 v a l ue s . The symbol x - i nd i ca te s va lues in the Treatment 2 data which were s i g n i f i c a n t l y less than the Treatment 1 da ta , such as f o r manganese and aluminum. S im i l a r to the ANOVA da t a , there was l i t t l e d i f f e r en ce between the th ree t ime pe r i ods , again i n d i c a t i n g the general i n s i g n i f i c a n c e of the t ime f a c t o r . I t is ev ident from these t ab l e s that some metals migrated at - 162 -Table 6.5 S i g n i f i c a n c e r e s u l t s fromm the Mann Whitney U Test ; t o t a l e lemental a na l y s i s , pH, e l e c t r i c a l c o n d u c t i v i t y of overburden Leve l s 1-9 (a) 3 months (b) 6 months) (c) 9 months; ac id e x t r a c t ab l e ana l y s i s of overburden (d) 3 months (e) 6 months ( f ) 9 months. (a) Tota l elemental a n a l y s i s , pH, EC (d) Ac id e x t r a c t ab l e ana l y s i s - 3 months - 3 months Level A l Zn Cu Fe Mn PH EC Level A l Zn Cu Fe Mn 9 x+ 0 0 0 0 0 x+ 9 0 0 0 0 0 8 0 0 0 0 0 0 x+ 8 0 0 0 0 0 7 0 0 0 0 0 0 x+ 7 0 0 0 0 0 6 0 0 0 0 x+ 0 x+ 6 0 0 0 0 0 5 0 0 0 0 x+ 0 x+ 5 0 0 0 0 0 4 0 x+ 0 0 x+ 0 x+ 4 x+ x+ x+ x+ x+ 3 0 x+ 0 0 x+ 0 x+ 3 x+ x+ x+ x+ x+ 2 X- x+ x+ x+ X- X- x+ 2 x+ x+ x+ x+ X-1 X- x+ x+ x+ X- X- x+ 1 x+ x+ x+ x+ X-(b) Tota l elemental - 6 months a n a l y s i s , pH, EC (e) Ac id e x t r a c t ab l e ana l y s i s - 6 months Level A l Zn Cu Fe Mn PH EC Level A l Zn Cu Fe Mn 9 x+ 0 0 0 0 0 x+ 9 0 0 0 0 0 8 x+ 0 0 0 0 0 x+ 8 0 0 0 0 0 7 0 0 0 0 0 0 x+ 7 0 0 0 0 0 6 0 0 0 0 0 0 x+ 6 0 0 0 0 0 5 0 x+ 0 0 0 0 x+ 5 0 x+ x+ 0 x+ 4 0 x+ 0 0 0 X- x+ 4 x+ x+ x+ x+ 0 3 X- x+ 0 x+ 0 ' X- x+ 3 x+ x+ x+ x+ 0 2 X- x+ x+ x+ X- X- x+ 2 x+ x+ x+ x+ X-1 X- 0 0 x+ X- X- x+ 1 x+ x+ x+ x+ X-- 16 3 -(c) Tota l e lemental a n a l y s i s , pH, EC ( f ) Ac id e x t r a c t ab l e ana l y s i s - 9 months - 9 months Level A l Zn Cu Fe Mn pH EC Level A l Zn Cu Fe Mn 9 0 0 0 0 0 0 x+ 9 0 0 0 0 0 8 0 x+ 0 0 0 0 x+ 8 0 0 0 0 0 7 0 x+ 0 0 0 0 x+ 7 0 0 0 0 x+ 6 0 x+ 0 0 x+ 0 x+ 6 0 0 0 0 x+ 5 x+ 0 0 0 x+ 0 x+ 5 0 0 0 0 x+ 4 X- x+ x+ x+ 0 X- x+ 4 x+ x+ x+ x+ 0 3 X- x+ x+ x+ 0 X- x+ 3 x+ x+ x+ x+ 0 2 X- x+ x+ x+ X- X- x+ 2 x+ x+ x+ x+ X-1 X- x+ x+ x+ X- X- x+ 1 x+ x+ x+ x+ X-Note: x+ Treatment 2 i s s i g n i f i c a n t l y greater than Treatment 1 (95% con f i dence ) . x - Treatment 2 is s i g n i f i c a n t l y less than Treatment 1 (95% con f i d ence ) . - 1 6 4 -f a s t e r ra tes than o the r s . Elements such as copper, which migrated in small c oncen t r a t i ons , could be detected at high l e ve l s in the e x t r a c t i o n da ta . The h ighest recorded concen t ra t i on of e x t r a c t ab l e copper in the Treatment 2 overburden was 25 ppm (Table A5.2, Appendix 5) compared to an average o f 1 ppm in the Treatment 1 columns. Accord ing to de Haan and Zwerman (1976) t h i s i s not unusual as the m o b i l i t y and displacement of copper i s s o i l s i s low ( i n s o i l s , i t is s t r ong l y bound by c l a y minera l s and organ ic ma t t e r ) . Accord ing t o Table A5.2 z i n c and manganese are the most mobi le me ta l s . The m o b i l i t y of zinc- i s a t t r i b u t ed to i t s i on i c form, as a l ready noted, which i s the predominant z i n c spec ies below pH 7.7 (de Haan and Zwerman, 1976). The e l e c t r i c a l c o ndu c t i v i t y da ta i n d i c a t e tha t s a l t s had migrated t o the sur face of the overburden fo r a l l Treatment 2 columns dur ing the f i r s t 3 month p e r i o d . The rap id m ig ra t i on of s a l t s to the sur face of the overburden was a l so i nd i ca t ed by high e l e c t r i c a l c o ndu c t i v i t y measurements of the Treatment 2, Level D s o l u t i o n s (Chapter 5 . 3 . 7 ) . A graph of the e l e c t r i c a l c o ndu c t i v i t y measurements of the s o i l samples suggests that d i f f e r e n t types of s a l t s are present in the columns. The data f o r the 3, 6, and 9 month per iods is p l o t t ed on F igure 6 . 5 . The measure-ments at Level 9 (near the top of the column) were approx imate ly 1.5 mmhos/cm and correspond to values of roughly 25 mmhos/cm as measured d i r e c t -l y on the s o l u t i on s ex t rac ted from the columns [F i gu re 5.14(a) Chapter 5 ] . (The extreme d i f f e r en ce i l l u s t r a t e s the e f f e c t of d i l u t i o n by the "5:1 method" adopted f o r the s o i l samples.) In F igure 6.5 the e l e c t r i c a l c o ndu c t i v i t y measurements were much higher at Leve l s 1-4 than at Leve l s 5-9. As noted in Chapter 5.3.7 chemical ana l y s i s suggested tha t the s a l t s r e spons i b l e f o r the e l e c t r i c a l - 1.6 5 -- 166 -conduct iv i ty measurements at Level D were calcium, magnesium and sodium. Therefore the f l a t part of the graph in Figure 6.5 (from Levels 5 to 9) is considered to represent the presence of calcium sul fate sa l t s . The higher conduct iv i t ies from Levels 1 to 4 suggest the presence of sa l ts of a d i f ferent composition. Struthers (1964) studied the composition of sa l ts generated from acid sulfate so i l s with character i s t i cs s imi lar to the Su l l i van iron t a i l i n g s . He ident i f i ed high concentrations of i ron, aluminum and manganese acid sul fate sa l t s . It is predicted, therefore, keeping the trend of pH in mind [Figure 6.2(d)] , that these same types of sa l t s as well as sa l ts of zinc and copper are responsible for the high e l e c t r i c a l conduct iv i ty measurements of Levels 1 to 4 in Figure 6.5. 6.4 Summary and Conclusions The analysis of the samples col lected at set intervals in the overburden for 3, 6 and 9 months indicated that l i t t l e change occurred in the overburden in Treatment 1 but that the overburden in Treatment 2 became severely contaminated up to 25 cm (from the overburden-tai1ings boundary). Migration of metals and acids appeared to occur rap id ly , within the f i r s t 3 months of the experiment, after which the rate of movement was negl ig ib le or zero. Zinc was the exception as i t cont inual ly increased in concentration in the overburden with time and cont inual ly migrated upwards into the overburden. A l l of the metals migrated beyond the region of overburden d i r e c t l y adjacent to the t a i l i ngs and were concentrated (except for iron) at the higher l eve l s . Also these metals did not appear to be i r r eve r s ib l y - 167 -prec ip i tated, as they were eas i l y removed in the extract ions. This suggests that as acid conditions develop at the higher levels in the overburden these metals, z inc, copper, aluminum and manganese would be mobile again and migrate with the acids. The concentration of iron was the greatest in the region near the t a i l i ng s boundary and only a small proport ion, roughly 10%, of the iron which migrated into the overburden could be extracted. This suggests the formation of an iron pan with iron i r revers ib l y p rec ip i t a t ing . Pan formation was phys ica l ly indicated by the presence of the endurated overburden at the zone of maximum concentration. Since rougly 15% of the iron added to the overburden through contamination could be extracted from the 3 month columns and roughly 9% from the 6 and 9 month columns i t appears that more than half of the iron to be precip i tated (which was 90%) was prec ip i tated in the f i r s t 3 months and the rest by 6 months. Aluminum and manganese represent d i f ferent s i tuat ions from z inc, copper, and i ron. The data suggests that the main source of contamination of the upper levels of overburden by aluminum and manganese was the overburden, through the destruct ion, by migrating acids from the t a i l i n g s , of the minerals inherent in the overburden. The difference in the pattern between the e l e c t r i c a l conduct iv i ty measurements in the solutions extracted from the columns (Chapter 5.3.7) and from the so i l samples, suggests that two d i s t i n c t l y d i f ferent sets of sa l ts were contaminating the overburden. I n i t i a l l y , calcium, magnesium and sodium sa l ts migrated to the surface. At the lower levels the meta l l i c ac id ic su l fate sa l ts of aluminum, copper, zinc and iron are considered to have secondari ly contaminated the overburden. - 168 -These r e s u l t s i nd i c a t e that the cover ing of the t a i l i n g s d i r e c t l y with overburden may r e s u l t in the u l t ima te contaminat ion of the overburden w i th high concent ra t ions of s a l t s , extreme ac id c ond i t i o n s , heavy metals in t o x i c concent ra t i ons u l t i m a t e l y fo l l owed by the format ion of a b a r r i e r impermeable to seed l ings r o o t s . T o x i c i t y due to metals is compl icated by many f a c t o r s such as ca t i on exchange c apac i t y , o rgan ic matter content , metal i n t e r a c t i o n s , changes in a c i d i t y and s o l u b i l i t y as we l l as severa l other f a c t o r s . However, the concen t ra t i on of these metals was gene ra l l y greater in the contaminated overburden, than normal ly assoc ia ted wi th s o i l s . The average amount of t o t a l z i n c in the Treatment 1 overburden was 90 ppm wh i l e concent ra t ions in the Treatment 2 were as high as 1,060 ppm. De Haan and Zwerman (1976) s t a t e tha t t o x i c l e v e l s are at about 400 ppm and up, and t o t a l z inc at normal cond i t i ons are in the 10-300 ppm range. In t h e i r rev iew, de Haan and Zwerman (1976) a l so d i s cuss copper t o x i c i t i e s . They s t a t e that i t i s the copper-molybdenum r a t i o which causes the most problems. (They note that copper is gene ra l l y about tw ice as t o x i c to p lan t s as z i n c . ) The maximum amount of copper in the Treatment 2 columns was 90 ppm compared to an average of 50 ppm in the Treatment 1 columns. Leeper (1972) records 20 ppm in a t y p i c a l s o i l ranging from 2-100 ppm. There fore , copper concent ra t i on in the contaminated overburden appeared to be in the range copper i s found in an "average" s o i l . Manganese concent ra t i on averaged 450 ppm in the Treatment 2 overburden and the maximum amount of manganese which migrated in any one Treatment 2 column was 1,120 ppm. Accord ing to Leeper (1972) t h i s amount f a l l s w i t h i n the range found in a t y p i c a l s o i l . - 169 -In summary, the grave l l ayer in the Treatment 1 columns was e f f e c t i v e as a hyd ro log i c b a r r i e r , located above a water t a b l e , prevent ing the upward m ig ra t i on of a c i d s , s a l t s , and meta l s . P l a c i ng the overburden d i r e c t l y onto the t a i l i n g s r i s k s complete contaminat ion of the overburden by metals and ac ids but more r a p i d l y by s a l t s in t o x i c concen t r a t i ons . - 170 -7.0 Summary and Conclusions A basic but c r i t i c a l conclusion that can be drawn from th is study is that the column method carr ied out in the laboratory is a feas ib le approach to invest igat ing the kinds of processes which would occur i f covering d i r e c t l y with overburden or separating the overburden from the t a i l i ng s with a gravel layer was adopted as a means of reclaiming the Sul l ivan Mine oxidized iron t a i l i n g s . The chemical analyses of the solutions extracted from the overburden, at spec i f i c in te rva l s , and of the overburden samples col lected fol lowing the dismantling of the columns, indicates that the gravel in the Treatment 1 columns, was e f fec t i ve , as a hydrologic bar r ie r , in preventing the upward migration of contaminants from the t a i l i ngs below. Also the overburden was not chemically affected by the experiment, as no substantial changes occurred in the Treatment 1 overburden during the experimental period. The chemical analyses do indicate that the overburden, in the Treatment 2 columns, became contaminated as a consequence of the direct contact with the t a i l i n g s . The solut ions extracted from the Treatment 2 overburden indicated that sa l t s , from the t a i l i n g s , believed to be of calcium, magnesium and sodium or ig in migrated through the overburden, causing sal ine conditions near the overburden surface. This occurred within one month of the i n i t i a t i o n of the experiment. The solut ions also indicated that contamination of the overburden by metals from the t a i l i ngs and from the destruction of minerals in the overburden by acids from the t a i l i ngs occurred rap id ly . The contamination by the metals is considered to be d i r e c t l y related to the migration of acids presumably, su l fu r i c acid, from the t a i l i n g s . Iron, z inc , copper, n i cke l , and cadmium were probably in the ionic form in the - 171 -t a i l i ng s and were present in the acid solutions brought up by cap i l l a r y movement from the t a i l i n g s . The pH of the overburden, near the tai l ings-overburden interface in the Treatment 2 columns, decreased to below 4 within one month of operation and therefore conditions were favorable for metal s o l ub i l i t y and mineral destruct ion. Aluminum and manganese, contaminating the overburden in Treatment 2 , are considered to be largely the resul t of mineral destruction in the overburden and not due to migration from the t a i l i n g s . As manganese was released more rap id ly than aluminum, the source of these metals is attr ibuted to the breakdown of d i f ferent compounds. I n i t i a l l y manganese was l i k e l y in the various oxide and hydroxide forms in the overburden. Aluminum was l i k e l y in the aluminum oxide or hydroxide forms or may have been present in s i l i c a t e clay minerals. As manganese hydroxide is more soluble than aluminum hydroxide an explanation for the more rapid release of manganese based on s o l ub i l i t y constants is acceptable. The analysis of the solut ions from the Treatment 2 columns also indicated that movement from the t a i l i ng s into the overburden at Level C and movement from the overburden at Level C to higher leve ls , reached steady state after 6 months. Var iat ion between the concentrations of the metals extracted in solut ion for the last 3 months of the experiment was minimal. The analysis of the t a i l i ng s solutions indicated that zinc and iron reached steady state conditions in the t a i l i ngs within 2 months of time zero, as concentrations of these metals did not vary with time. However, in the Treatment 1 columns the amount of zinc and iron removed form the t a i l i ng s solut ions increased substant ia l l y with time. This suggests continuous oxidation of the t a i l i n g s . The t a i l i ngs in the - 172 -Treatment 1 columns were more f r equen t l y and to a greater ex ten t , exposed to oxygen as the de s i c c a t i on of the overburden permit ted easy gas f low through open pores and vo i d s . Access of oxygen to the t a i l i n g s in Treatment 2 was g r e a t l y impeded and the constant amount of z i nc and i ron removed in s o l u t i o n i nd i c a t e s that ox i da t i on was occu r r i ng but at a comparat ive ly subdued and c on t r o l l e d r a t e . Aluminum, copper, manganese, n i c k e l , e t c . in the t a i l i n g s in both t reatments decreased in concent ra t i on with time suggest ing that ox i da t i on of the t a i l i n g s d id not a f f e c t the re l ease of these metals in to a so lub le fo rm. The imp l i c a t i o n s of the d i f f e r en ce s in z i nc and i ron pat terns in the experiment has no se r ious impact on the rec lamat ion of the t a i l i n g s . Though the ox i da t i on ra te of the t a i l i n g s was dampened by the d i r e c t contac t wi th the overburden, ox i da t i on was s t i l l o c cu r r i ng and thus the p o t e n t i a l f o r perpetua l r e l ea se of these metals i s s t i l l p resen t . In Treatment 1 these metals in the t a i l i n g s were re leased in high concent ra t ions but s ince m ig ra t i on was not o c cu r r i ng , these metals remained in t h e i r o r i g i n a l environment. However the imp l i c a t i on s of the decrease of aluminum, copper, manganese, n i c k e l , e t c . in the t a i l i n g s is that a l im i t e d supp ly of these metals is a v a i l a b l e from the t a i l i n g s . However they are i n i t i a l l y at concent ra t ions de l e t e r i ou s to most p l a n t s . Aluminum and manganese, re leased from the overburden s o i l , through minera l de s t r u c t i on migrated wi th the ac ids through the overburden and p r e c i p i t a t e d at h igher l e v e l s than where the o r i g i n a l de s t ru c t i on occur red . The h ighest concent ra t ions of z i n c and copper a lso d id not occur in the overburden adjacent to the t a i l i n g s but p r e c i p i t a t e d at the height at which the m ig ra t i ng ac ids became neu t r a l i z ed by the a l k a l i n e cond i t i ons of the uncontaminated overburden. These meta l s , namely copper and z i n c , were not i r r e v e r s i b l y p r e c i p i t a t e d , as they were e a s i l y removed in the ac id e x t r a c t i o n s . This suggests that i f ac id cond i t i ons developed at the high l e v e l s in the overburden, near the su r f a ce , these metals would once again become so l ub l e and mobi le and would migrate with the a c i d s . This would r e s u l t in eventual contaminat ion to the su r f a ce . In con junc t ion wi th the m ig ra t i on of a c i d , minera l breakdown would a l so occur supp ly ing greater concent ra t ions of aluminum and manganese with t ime. There i s p o s i t i v e evidence tha t these two metals are de l e t e r i ou s to vege ta t i on above c e r t a i n concen t r a t i on s . Iron concent ra t i ons were h ighest in the overburden adjacent to the t a i l i n g s and on ly a small p ropor t i on of the i ron added to the overburden, through t a i l i n g s contaminat ion , was e x t r a c t a b l e . This f a c t as we l l as the i ndu ra t i on of the overburden, adjacent to the t a i l i n g s , i nd i ca tes that i ron pan format ion was occu r r i ng in the overburden in the Treatment 2 columns. The format ion of the pan occurred r a p i d l y w i th i n 3 months, as most of the i r on that was p r e c i p i t a t e d , d id so w i t h i n the f i r s t '3 months. It i s p red i c t ed tha t wi th t ime the i ron pan would expand, e ven tua l l y to the s u r f a c e . In a f i e l d s i t u a t i o n , the pan would produce a b a r r i e r , impermeable to seed l i ng roots p lanted on the overburden. The e l e c t r i c a l c o n d u c t i v i t y measurements made on the s o i l samples, from the Treatment 2 columns, i n d i c a t e that two major groups of s a l t s contaminated the Treatment 2 overburden. I n i t i a l l y , c a l c i um, magnesium and sodium s a l t s contaminated the overburden to the sur face of the columns, r e s u l t i n g in extremely s a l i n e c ond i t i o n s . This would prevent vege ta t i on es tab l i shment even with s a l t t o l e r an t spec ies and a t h i c k cover of s o i l . The overburden was s e conda r i l y contaminated wi th i r o n , copper, and z i n c The migra t ion of ac ids and metals in to the overburden occurred r a p i d l y , w i t h i n the f i r s t 3 months of the exper iment, contaminat ing rough ly 20 cm of overburden. There was l i t t l e progress ion beyond that he ight a f t e r 6 months. The s t a t i s t i c a l ana l y s i s of the r e su l t s i nd i ca ted that t ime was not s i g n i f i c a n t in the exper iment, except fo r z i n c . The abrupt te rm ina t i on of m ig ra t i on of the metals i s c o r r e l a t ed to acid migra t ion but z i nc i s mobi le under ac id and a l k a l i n e c ond i t i o n s . The s t a t i s t i c a l i n s i g n i f i c a n c e of t ime suggests tha t the ra te of contaminat ion of overburden, i n . d i r e c t contact with mate r i a l such as the S u l l i v a n Mine ox i d i z ed i ron t a i l i n g s , i s i n i t i a l l y rap id but subsequent ly decreases to a ra te adapted to the environmental c o nd i t i o n s . The height to which m ig ra t i on d id occur (20 cm) i s cons idered to be a response to the exper imenta l des ign of the p r o j e c t . I f a greater volume of water had been app l i ed to the columns, i t i s suspected that contaminat ion would have extended to a greater he igh t . I f l ess water had been app l i ed , contaminat ion would not have extended to 20 cm. The v a r i a b i l i t y in the degree of contaminat ion between the i n d i v i d ua l columns i s cons idered to be a response to d i f f e r ence s in the packing of the overburden and in the pat terns of water movement in the columns. This v a r i a b i l i t y can be t r a n s l a t ed in to a f i e l d s i t u a t i o n as methods of app ly ing the cover ing mate r i a l by heavy equipment, and methods of i r r i g a t i n g can a f f e c t the degree of contaminat ion of the overburden or cover . The success of the g r a v e l , in the Treatment 1 columns, in p ro t e c t i ng the overburden from the e f f e c t s of the t a i l i n g s was insured by c a r e f u l l y c o n t r o l l e d wa te r i ng . I f excess water had been app l ied to the Treatment 1 columns, a temporary water t ab l e would have been b u i l t up in the gravel and - 175 -r e su l t e d in the contaminat ion of the overburden. There fo re , i t is important to recogn ize that the depth of grave l must be geared to the c l ima te and s o i l c ond i t i ons of the mine s i t e . F ive cent imeters of gravel in the column treatment was acceptab le as the experiment was c o n t r o l l e d . In the f i e l d , i t i s l i k e l y that heavy equipment could not d i s t r i b u t e much less than 30 cm of g r a v e l . Therefore the depth of grave l should be c a l c u l a t ed by cons ide r ing the maximum amount of water app l ied to the s o i l by a r a i n f a l l event or by snowmelt. I f sp r ing runof f r e s u l t s in 25 cm of water at any given t ime, the depth of grave l should be at l eas t t h i s , and fo r sa f e t y purposes, g r ea t e r . The amount of water reach ing the grave l is a l so a f fec ted by the mois ture ho ld ing capac i t y of the s o i l . In a sandy s o i l , more water would f l ow through the overburden in a given event compared to a s i l t y - c l a y tex tu red s o i l . This in format ion must the re fo re be incorporated in to the des ign of the t reatment . The grave l represents a continuum in pore s i z e . Inc reas ing the diameter of the coarse fragments would r e s u l t in co r respond ing ly l a rge r pores and vo ids which may a l low the " s i l t i n g i n " of the g r a v e l . This would prov ide a connect ion between the t a i l i n g s below the grave l and the overburden above i t . I t would t he re fo re r e s u l t in overburden contamina t ion . I f the b a r r i e r fragments are too smal l and pore s i z e s are consequent ly sma l l , c a p i l l a r y movement may occur and a lso r e s u l t in the contaminat ion of the cover ing m a t e r i a l . The d e f i n i t i o n of rec lamat ion i s not c l ea r but gene ra l l y rec lamat ion u l t i m a t e l y means the estab l i shment and maintenance of v ege t a t i on . It would - 176 -be de s i r a b l e to vegetate the overburden used as a cover fo r the t a i l i n g s . There may be some quest ion that in the s i t u a t i o n of the Treatment 1 approach that p lant roots would penetrate the g r a ve l , the t a i l i n g s , and would not su rv i ve desp i t e the b a r r i e r . In many s tud ies in which t o p s o i l has been used fo r rec lamat ion as a cover , d i f f i c u l t i e s have emerged in e s t a b l i s h i n g vegeta t ion on a t o p s o i l which may be unsu i t ab l e fo r p lant growth. Vegetat ion i s cons idered to have a p o s i t i v e e f f e c t in rec lamat ion as i t in tervenes wi th the downward movement of water by uptake through the roots and thus decreases the amount of water reach ing the t a i l i n g s . Therefore i t i s e f f e c t i v e in decreas ing ac id r uno f f . Fac tors which d iscourage vegeta t ion growth in t o p s o i l inc lude moisture s t r e s s , low f e r t i l i t y and compactness of the s o i l (high bulk d e n s i t y ) . In the column study, the overburden in Treatment 1 became seve re l y des i cca ted suggest ing that in the f i e l d at S u l l i v a n Mine, the overburden would r equ i r e i n i t i a l l y the use of moisture t o l e r a n t spec ies or supplemental i r r i g a t i o n . F i e l d t r i a l s should be c a r r i e d out to t e s t f o r the optimum bulk dens i t y which would a l low root pene t ra t i on and gas movement ( f o r roo ts ) but a lso which would be compact enough to deter some of the i n f i l t r a t e d water from reach ing the gravel l a ye r . I f the rec lamat ion of the S u l l i v a n Mine i ron t a i l i n g s were approached by cove r i ng , the i n c l u s i o n of a gravel b a r r i e r would be more economica l l y f e a s i b l e as less s o i l depth would be requ i red than i f d i r e c t cover ing was adopted. The ex t ra depth of overburden needed to stave o f f contaminat ion by upward m ig ra t i on of s a l t s would not be r equ i r e d . The depth of overburden recommended i f the grave l treatment were adopted would be roughly 30 cm to a l l ow f o r mois ture ho ld ing capac i t y and f o r root growth, wi th a minimal - 177 -depth of 15 cm (plow l a y e r ) . However the q u a l i t y of the p lant environment would improve wi th depth and t he re f o r e 45 cm to a meter of cover is not out of the ques t i on . In summary, the l abo ra to ry column study was usefu l as a method of understanding the processes which would occur i f the overburden was placed d i r e c t l y onto the ox i d i zed i ron t a i l i n g s or separated from i t by a grave l b a r r i e r . The r e s u l t s i n d i c a t e that d i r e c t placement of overburden onto the t a i l i n g s may be a short term rec lamat ion approach but the use of a b a r r i e r would prov ide e f f e c t i v e and long term rec lamat ion of the S u l l i v a n Mine ox i d i z ed i ron t a i l i n g s . I f p rope r l y planned t h i s approach would not requ i re cont inuous maintenance and rec lamat ion would be permanent. - 17.8 -LITERATURE CITED Adm in i s t r a t i v e Rules of Montana. 1978. Montana's s t r i p and underground mine rec lamat ion r u l e s and r egu l a t i o n s : i n t e r im regu l a to r y program. Montana, U.S.A. Bar rau , E.M. and W.A. Berg. 1977. 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M i l tmore , J . C . and J . L . Mason. 1971. Copper to molybdenum r a t i o and molyb-denum and copper concent ra t ions in ruminant feeds . Can. J . Anim. S c i . 51: 193-200. Morton, J.W. 1976. The phys i ca l l i m i t a t i o n s to vegeta t ion estab l i shment of some southern B r i t i s h Columbia mine waste m a t e r i a l s . M.Sc. Thesis U . B . C , Vancouver, B.C. Mubarak, A . , L. Hageman, R.A. Howald, and R. Wood f i f f . 1978. Ser ious i n t e r f e r ences in the determinat ion of t race metals in s o i l s by flame and f l ame less atomic absorpt ion spect rometry . S . S . S . A . J . 42(6) : 889-891. Novozamsky, I . and J . Beek. 1976. Common s o l u b i l i t y e q u i l i b r i a in s o i l s , p. 96-125. I_n 6.H. Bo l t and M.G.M. Bruggenwert (eds . ) So i l chemis t ry A. bas i c e lements. E l s e v i e r S c i e n t i f i c Pub l i s h i ng Company, New York. Pedology Labora to ry . 1977. Methods manual. Dept. of S o i l S c i ence . U.B.C. Vancouver, B.C. Pennsy lvan ia Department of Environment Resources. 1976. Standard cond i t i ons accompanying permits au tho r i z i ng the operat ion of coal mines. ER-MR 111 12/76 Pennsy lvan ia Department of Environmental Resources, Hanisburg, Pa . 17120. - 187 -P ionke , H.B. and A .S . Rogowski. 1979 . How e f f e c t i v e i s the deep placement of a c i d s po i l ma te r i a l s ? J_n the Fourth Annual Canadian Land Reclamat ion A s s o c i a t i o n . Reg ina , Saskatchewan. P l a s s , W.T. 1974 . Fac to r s a f f e c t i n g the es tab l i shment of d i r e c t seeded pine on sur face-mine s p o i l s . U.S. For . Serv. Res. Pap. NE - 2 9 0 . Pons, L . J . 1972 . Ou t l i ne of the genes i s , c h a r a c t e r i s t i c s , c l a s s i f i c a t i o n and improvement of a c i d s u l f a t e s o i l s . J_n P r o c . o f the I n t . Symposium on Ac id Su l f a t e S o i l s . Nether lands . Ranta la , R.T.T. and D.H. L o r i n g . 1973 . New low-cost t e f l o n decomposit ion v e s s e l . Techn ica l note. Absorp t ion News le t te r 1 2 ( 4 ) : 9 7 - 9 9 . R i c e , H.M.A. 1937 . Cranbrook map-area. Geo l . Surv . Canada Mem. 207 . Robb ins , J . M . 1978 . Weathering and m i c rob i a l a c t i v i t y i n s u l f i d e mine t a i l i n g s w i th imp l i c a t i o n s i n r ec l amat i on . M.Sc. Thes i s . U . B . C , Vancouver, B.C. Rogowski, A . S . and E.L. Jacoby, J r . 1979 . Mon i t o r i ng water movement v t h r ough s t r i p mine s o i l p r o f i l e s . J_n Transac t ions of the A . S . A . E . 2 2 ( 1 ) : 1 04 - 109 . - 188 -Sa l cedo , I . H . and D.D. Warncke. 1979. S tud ies i n s o i l manganese: I . f a c t o r s a f f e c t i n g manganese e x t r a c t a b i l i t y . S . S . S . A . J . 43 (1 ) : 135-138. S i nge r , P.C. and W. Stuum. 1970. A c i d i c mine dra inage: the r a t e -determin ing s t ep . Sc ience 167: 1121-1123. Smith, R.A.H. and A.D. Bradshaw. 1972. S t a b i l i z a t i o n of t o x i c mine wastes by the use of t o l e r a n t p l an t popu l a t i on s . T rans . I n s t n . M in . M e t a l l . 81: 230-237. Smith, R.M. e t a l . 1974. Mine s po i l p o t en t i a l s f o r s o i l and water q u a l i t y . U.S. Environmental P r o t e c t i o n Agency, C i n c i n n a t i , Oh io . Sm i th , R.M., W.E. Grube, J r . and J . R . Freeman. 1975. Be t t e r m i n e s o i l s . West V i r g i n i a A g r i c u l t u r a l Exper imental S t a t i o n . S c i e n t i f i c Paper No. 1359. S o i l Mo is ture Equipment Corp. M u l t i p l e Manometer Apparatus. Santa Barbara , C a l i f o r n i a 93105. U.S.A. Sommers, L .E. and W.L. L indsay . 1979. E f f e c t of pH and redox on p red i c t ed heavy me ta l - che l a t e e q u i l i b r i a i n s o i l s . J . S . S . S . A . J . 43 (1 ) : 39-47. S o r r e l l , S.T. 1974. E s t a b l i s h i n g vege ta t i on on a c i d i c coal re fuse ma te r i a l s w i thout the use of t op so i l cover . p. 228-236. I_n F i r s t - 189 -Symp. on Mine and P repara t ion P lant Refuse D isposa l Coal and the Environment Techn i ca l Conference. L o u i s v i l l e , Ky. Sp i r e s , A .C . 1 9 7 5 . Stud ies on the use of overburden s o i l s in f a c i l i t a t i n g vege ta t i ve growth on high s u l f i d e t a i l i n g s . M.Sc. Thes i s . Laurent ian U n i v e r s i t y . S t r u t h e r s , P.H. 1 9 6 4 . Chemical weather ing of s t r i p mine s p o i l s . Ohio J . S c i . 6 4 ( 2 ) : 1 2 5 - 1 3 1 . U.S. S a l i n i t y Labora to ry S t a f f . 1 9 6 9 . J J T _ L . A . R ichards (ed . ) D iagnos is and improvement of s a l i n e and a l k a l i s o i l s . A g r i c . Handb. No. 6 0 , U.S.D.A. U.S. Government P r i n t i n g O f f i c e , Washington, D.C. Voge l , W.G. and W.A. Berg. 1 9 6 8 . Grasses and legumes fo r cover on ac id s t r i p -m ine s p o i l s . J . of So i l and Water Conserva t ion . 2 3 ( 3 ) : 8 9 - 9 1 . Watk in, E.M. 1 9 7 5 . Vegeta t i ve s tud ies on s u l f i d e and s lag t a i l i n g s . p. 2 2 5 - 2 5 8 . The Canadian Minera l Processers Annual Meet ing . Ottawa, On ta r i o . Watk in, E.M. 1 9 7 9 . Aspects of mine waste rec lamat ion in Cent ra l Canada. Un iv . o f Guelph, Guelph, On ta r i o . - 1 9 0 -White , M.C., A.M. Decker, and R.L. Chaney. 1979. D i f f e r e n t i a l c u l t i v a r . to l e rance i n soybean to phy to tox i c l e v e l s of s o i l z i n c . I . Range of c u l t i v a r response. Agronomy Journa l 71(1) : 121-126. Wood, R.W. 1974. Rep ly . Water Resources Research 10(5) : 1050. - 191 -Appendix 1.1 C l ima t i c data fo r the K imber ley a r ea 0 P r e c i p i t a t i o n (mm) mean annual 377 .6 mean annual r a i n f a l l 228 .8 maximum r a i n f a l l 51 .8 (June) mean annual snowfa l l 154 .5 maximum snowfa l l 42 .4 (December) Temperatures (°C) maximum ' 32 (August) minimum -21 .1 (March) Growing Season (days) 181 Frost f r ee (days) Growing degree days 92 1530 c F rom: Canada Department of T ranspor t , Me teo ro l og i ca l Branch. 1968. C l ima t i c Normals, P r e c i p i t a t i o n . V o l . I I . Canada Department of T ranspor t , Me teo ro log i ca l Branch. 1968. C l ima t i c Normals, Temperature. V o l . I . - 192 -APPENDIX 2.1 Dra f t o f three undisturbed non-vegetated S u l l i v a n mine i r o n t a i l i n g s p i t p r o f i l e s i n d i c a t i n g the amount o f v a r i a b i l i t y across the pond. 74-SF-l 74-SF-2 74-SF-3 0 cm •25 cm O J -50 cm 75 cm Hard crust 'Silty clay' (interfingering or predominant) Iron cemented ortstein ] Unreduced iron tailings From: L a v ku l i c h , L .M. , e t . a l . 1975. Pedo log i ca l i n ven to r y o f three s u l f i d e mine areas i n S.W. B r i t i s h Columbia. Dept. o f S o i l S c i ence , U.B.C. Vancouver, B.C. Appendix 2.2 P r o f i l e d e s c r i p t i o n of und is turbed non-vegetated S u l l i v a n Mine i r on t a i l i n g s sample, 7 4 - S F - l * Depth Layer (cm) 0 - 1 5 A Strong brown (7.5 YR 5 /8 ) , loam - c l ay loam; very s t r ong l y cemented; f u l l of smal l round gas ho les ; pH 2.5 15- 38 B L i g h t o l i v e grey (5Y 6/2) wi th some st rong brown (7.5 YR 5/8); s i l t loam; s t i c k y when wet; pH 2.5 38-51 C Strong brown (7.5 YR 5/8) i n t e r f i n g e r e d wi th some l i g h t o l i v e grey (5Y 6/2) and some black (5Y 2/1) m a t e r i a l ; s i l t loam; deve lop ing i n to an i r on pan ( o r t s t e i n ) ; pH 2.5 51-69 D Black (7.5 YR 2/0) ; loam - s i l t loam, indura ted; pH 4.2 69-91 E B lack (7.5 YR 2/0) banded w i th o l i v e (5Y 4 /4) ; loam; below water t ab l e and complete ly sa tu ra ted ; pH 4.0 * Dep ic ted in Appendix 2.1 From: Lavku l i ch L.M. e t a l . 1975 Pedo log i ca l inventory of three s u l f i d e mine areas i n S.W. B r i t i s h Columbia. Dept. o f S o i l Sc i ence , U.R.C. , Vancouver, B.C. 172 p. - 194 -Appendix 2.3 P r o f i l e d e s c r i p t i o n of und is turbed non-vegetated S u l l i v a n Mine i r on t a i l i n g s sample 74-SF-2* Depth Layer (cm) 1 - 0 c r u s t White sur face c r u s t p r e c i p i t a t e d on sur face 0 - 1 8 A Strong brown (7.5 YR 5/8); loam; very s t r ong l y cemented; f u l l o f small round gas ho les ; pH 2.5 18-23 R L i gh t o l i v e grey (5Y 5/2) wi th some st rong brown (7.5 YR 5/8); s i l t loam; s t i c k y when wet; pH 2.3 23-28 C Strong brown (7.5 YR 5/8); s i l t loam; indura ted much l i k e an o r t s t e i n 28-61 D Black (7.5 YR 2 /0 ) ; loam; most ly below water t a b l e and sa tu ra ted ; pH 3.5 * Dep ic ted i n Appendix 2.1 From: Lavku l i ch L.M. e t a l . 1975 Pedo log i ca l inventory of three s u l f i d e mine areas i n S.W. B r i t i s h Columbia. Dept. o f S o i l Sc i ence , U . B . C , Vancouver, B.C. 172 p. - 195 -Appendix 2.4 P r o f i l e d e s c r i p t i o n o f und is turbed non-veqetated S u l l i v a n Mine i r on t a i l i n g s sample 74-SF-3* Depth Layer (cm) 0 - 8 A Brownish ye l l ow (10 YR 6/8); s i l t loam - loam; weak crumbly s t r u c t u r e ; many f i n e roots 8 -15 B Dusky red (2.5 YR 3 /2 ) ; loam; weak p l a t y s t r u c t u r e ; many f i n e roots 15-23 C Strong brown (7.5 YR 5/6); s i l t loam; s t r u c t u r e l e s s ; few f i n e roots 23-25 D Brown (7.5 YR 4 / 4 ) ; s i l t loam; s t i c k y when wet 25+ E Dark redd i sh brown (5 YR 2 /2 ) ; g r a v e l l y sandy loam; very s t r ong l y cemented; l a r g e l y o r i g i n a l s o i l mate r i a l p redat ing i r on s p i l l NOTE: Th is area i s sub jec t to pe r i od i c natura l f l o o d i n g . * Depic ted in Appendix 2.1 From: Lavku l i c h L.M. e t a l . 1975 Pedo log i ca l inventory of three s u l f i d e mine areas in S.W. B r i t i s h Columbia. Dept. of S o i l Sc ience , U . B . C , Vancouver, B.C. 172 p. - 196 -Appendix 3.1 P r o f i l e d e s c r i p t i o n of overburden* C l a s s i f i c a t i o n Loca t i on E l e v a t i o n Slope and aspect Parent mate r i a l Landform Drainage c l a s s Note O r t h i c Humo-Ferr ic Podzol Adjacent to S i l i c e o u s t a i l i n g s 1130 m 0 - 2% T i l l T i l l p l a i n Moderate ly wel 1 A f f ec ted by dust from s i l i c a t a i l i n g s Depth HORIZON (cm) LFH 3 - 0 Bf 0 - 2 0 Ye l l ow i sh brown (10 YR 5/6); s i l t loam, very weak s t r u c t u r a l b l o ck s , many f i n e d i s t i n c t roo t s BC 20 - 32 Ye l l ow i sh brown (10 YR 5/4) , s i l t loam, s t r u c -t u r e l e s s C 32+ Pa le brown (10 YR 6 /3 ) , s i l t loam, s t r u c t u r e -l e s s DOMINANT VEGETATION Ponderosa P ine T a l l mahonia Bearberry P inegrass Douglas F i r Western Larch *Morton, J .W. 1976. The phys i ca l l i m i t a t i o n s to vege ta t i on es tab l i shment o f some B r i t i s h Columbia mine waste m a t e r i a l s . M.Sc. Thes i s . Dept. o f S o i l S c i ence , U.B.C. Vancouver, B.C. - 197 -Appendix 2.3 P a r t i c l e S i ze a na l y s i s o f overburden* Tab le 4-2 Hor i zon % 2 mm % Sand % S i l t % c l a y Textured C lay Bf 62 25 65 10 s i l t loam BC 64 28 66 6 s i 11 loam C 49 35 54 11 s i l t loam *Morton, J.W. 1976. The phys i ca l o f some B r i t i s h Columbia mine So i l Sc ience , U.B.C. Vancouver l i m i t a t i o n s to vege ta t i on es tab l i shment waste ma t e r i a l s M.Sc. The s i s . Dept. o f , B.C. - 198 -Appendix 3.3 Water r e t en t i on data fo r overburden* Hor izon -1/3 bar kg/kg -15 bar kg/kg W.S.C. kg/kg W.S.C. kg/kg co r rec ted f o r fragments W.S.C m/m Bf .324 .079 .245 .152 .149 BC .206 .064 .142 .091 • .089 C .078 .064 .014 .007 .007 *Morton, J.W. 1976. The phys i ca l l i m i t a t i o n s to vegeta t ion estab l i shment of some B r i t i s h Columbia mine waste ma te r i a l s M.Sc. Thes i s . Dept. of S o i l Sc ience , U.B.C. Vancouver, B.C. - 199 -Appendix 4.1 Ra t i o (%) of ex t r a c t ed i r on and i r on added through contaminat ion a t Leve l 1 in s o i l samples from overburden i n Treatment 2 columns f o r 3, 6 and 9 months Column Per iod Ex t rac ted* Added** Rat io (months) I ron I ron (%) 14 3 5,600 47,000 11.9 17 3 4,090 36,000 11.4 18 3 7,900 37,000 21.4 11 6 4,360 42,000 10.4 13 6 9,000 42,000 21.4 15 6 3,480 49,000 7.1 10 9 3,180 50,000 6.4 12 9 1,680 21,000 8.0 16 9 1,440 21,000 6.9 i r o n : data from 0. INHC1 ex t r a c t ab l e ana l y s i s (Chapter **Added i r o n : c a l c u l a t e d by sub s t r a c t i ng t o t a l i ron inherent i n over-burden (taken as 30,000 ppm from Treatment 1 overburden) from t o t a l i r on a t Leve l 1 (Chapter 6 ) . - 200 -Appendix 4 .2 Ra t i o (%) of ex t r a c t ed z i nc and z inc added through contaminat ion a t Leve l 1 in s o i l samples from overburden in Treatment 2 columns f o r 3 , 6 and 9 months Column Per iod Ex t rac ted* Added** Rat io (months) Z inc Z inc (%) 14 3 60 160 37.5 17 3 59 130 45.4 18 3 97 60 >100 11 6 78 70 >100 13 6 76 50 >100 15 6 43.1 110 43 10 9 55.2 60 92 12 9 78 180 43 16 9 94 110 49.5 *Ex t rac ted z i n c : data from 0.INHC1 ex t r a c t ab l e ana l y s i s (Chapter 6 ) . Added z i n c : c a l c u l a t e d by sub s t r a c t i ng t o t a l z i nc inherent i n over-burden (taken as 100 ppm from Treatment 1 overburden) from t o t a l z i n c a t Leve l 1 (Chapter 6 ) . - 201 -APPENDIX 5.1 T o t a l A n a l y s i s , pH -and E l e c t r i c a l C o n d u c t i v i t y '(E'.:C.). o f Overburden TRL T A l (ppm) 1 1 1 58000 1 2 1 55000 1 3 1 53000 1 4 1 52000 1 51 .1 52000 1 6 1 57000 1 7 1 53000 1 8 1 49000 1 9 1 55000 1 1 1 52000 1 2 1 55000 1 3 1 54000 1 4 1 56000 1: . 5. 11 53000 1 6 1 51000 1 7 1 57000 1. 8 1 50000 1 9 1 . 51000 1 1 1 50000 1 2 1 51000 1 3 1 49000 1 4 1 52000 1 5 1 54000 1 6 1 52000 1 7 1 52000 1 8 1 52000 1 9 1 51000 1 1 2 47000 1 2 2 56000 1 3 2 55000 1 4 2 55000 1 5 2 55000 1 6 2 57000 1 7 2 59000 1 8 2 57000 1 9 2 50000 1 1 2 49000 1 2 2 55000 1 3 2 54000 1 4 2 59000 1 5 2 58000 1 6 •2 55000 1 7 2 49000 1 8 2 56000 1 9 2 50000 1 1 2 60000 1 2 2 55000 TR = TREATMENT „Zn Cu -Fe (ppm) (ppm) (ppm) 200 40 28000 60 50 27000 120 50 29000 80 30 26000 80 50 25000 100 30 28000 90 40 26000 80 60 30000 80 50 29000 70 40 27000 80 50 26000 90 50 27000 70 30 2 60 00 70 50 30000 70 50 24000 60 40 26000 70 60 28000 90 50 28000 120 50 28000 90 30 26000 70 40 29000 70 50 31000 70 50 26000 70 30 28000 80 60 26000 90 50 29000 80 40 27000 130 50 29000 70 30 27000 70 30 27000 110 30 26000 100 30 27000 80 40 27000 70 40 27000 90 30 27000 80 50 30000 130 50 31000 60 .30 27000 70 30 27000 320 30 28000 100 30 28000 100 40 26000 130 50 28000 220 50 27000 90 70 28000 160 30 31000 70 30 27000 L - LEVEL T = Mn pH E.C. (ppm) (mmho 420 763 31 480 763 27 500 772 25 490 750 24 450 763 24 480 767 22 480 756 23 480 757 19 500 760 19 450 769 39 460 774 28 440 778 25 ' 450 7'72 26 450 780 22 410 765. 23 440 773 23 490 776 26 4 70 765 20 460 772 28 500 765 22 400 . 777 25 460 768 17 430 765 18 480 774 19 470 766 18 470 764 15 440 775 17 430 72 5 21 470 719 24 480 . 760 20 450 766 18 490 778 16 480 775 14 490 753 14 520 763 13 500 770 12 450 678 38 470 777 27 4 60 765 22 500 763 18 480 768 17 490 777 16-420 781 15 480 775 13 500 780 12 470 751 25 470 751 22 TIME - 202 -TRL T , Ad Zn Cu Fe ., Mn PH E.C. (ppm) (ppm) (ppm) ('ppm) (ppm) '(mmh 1 3 2 50000 120 60 29000 430 751 22 1 4 2 57000 120 40 , 29000 500 761 19 1 5 2 55000 70 30 26000 460 763 19 1 6 2 55000 70 30 27000 480 773 18 1 7 2 55000 90 90 28000 480 771 17 1 8 2 57000 60 40 26000 480 760 14 1 9 2 50000 110 60 29000 450 769 13 1 1 3 54000 150 40 28000 480 756 18 1 2 3 57000 180 30 29000 470 759 16 1 3 3 54000 100 30 27000 500 753 13 1 4 3 56000 140 30 27000 4.80 747 12 1 5 3 55000 90 30 27000 480 770 13 1 6 3 56000 100 30 26000 490 748 13 1 7 3 55000 100 40 27000 480 770 13 1 8 3 58000 80 40 27000 500 758 12 1 9 3 56000 130 50 27000 490 778 12 1 1 3 55000 120 50 27000 470 758 32 1 2 3 56000 150 30 27000 470 758 26 1 3 3 53000 160 30 2 8000 470 758 24 1 4 3 51000 370 30 31000 470 754 20 1 5 3 55000 130 50 27000 490 764 18 1 6 3 58000. 120 30 26000 500 762 16 1 7 3 57000 130 40 28000 5.0 0 760 13 1 8 3 57000 160 30 27000 500 758 12 1 9 3 56000 170 50 28000 510 767 11 1 1 3 54000 160 40 27000 510 767 22 1 2 3 57000 140 30 28000 490 777 18 1 3 3 60000 110 30 27000 470 773 18 1 4 3 51000 70 50 28000 540 764 18 1 5 3. 58000 210 30 31000 500 772 18 1 6 3 56000 100 40 27000 480 769 16 1 7 3 59000 90 30 27000 480 761 15 1 8 3 58000 100 3 0 27000 490 766 15 1 9 3 56000 80 40 26000 490 762 11 2 i : .1 35000 260 . 60 77000 230 213 575. 2 .2 1 39000 460 90 59000 370 270 477 2 3 1 5'1000 440 40 26000 840 752 227 2 4 1 52000 130 50 26000 630 756 141 2 5 1 45000 130 50 27000 420 765 121 2 6 1 47000 210 60 29000 440 756 106 2 7 1 54000 ' 90 50 26000 470 760 101 2 8 1 48000 110 50 28000 410 763 99 2 9 1 57000 90 40 27000 500 754 104 2 1 1 45000 230 70 66000 230 224 428 2 2 1 41000 320 80 53000 260 253 464 2 3 1 50000 640 50 41000 460 391 375 2 4 1 50000 140 50 29000 640 738 177 2 5 1 53000 260 60 29000 720 741 123 TR = TREATMENT L - LEVEL T = TIME - 203 TR L T A l Zn Cu Fe Mn pH E.C. (ppm) (ppm). (ppm) (ppm) (ppm)' (mmhos/cm) 2 6 i 48000 120 50 28000 5 30 760 107 2 7 1 59000 150 60 32000 510 811 102 2 8 1 46000 .120 50 28000 400 752 109 2 9 1. 58000 110 40 34000 510 754 139 2 1 1 39000 160 50 67000 210 207 464 2 2 1. 39000 220 70 64000 240 219 503 2 3 1 48000 190 50 -29000 770 781 163 2'\ 4 1 51000 100 50 26000 530 725 122 2 5 1 47000 70 40 . 29000 390 747 70 2 6 1 59000 80 40 27000 500 748 133 2 7 1 49000 80 50 28000 410 734 122 2 8 1 76000 80 40 27000 500 742 124 2 9 1 48000 80 50 29000 400 768 89 2 1 2 40000 170 60 72000 230 219 434 2 2 2 54000 570 50 80000 370 252 342 2 3 2 46000 300 50 63000 320 286 316 2 4 2 51000 260 70 49000 350 383 298 2 5 2 64000 450 50 31000 990 739 108 2 6 2 59000 70 40 27000 6.60 .769 96 2 7 2 62000 80 . 40 29000 520 756 119 2 8 2 61000 70 40 27000 500 776 116 2 9 2 56000 70 40 27000 440 759 143 2 1 2 41000 150 80 72000 210 222 503 2 2 2 47000 360 60 58000 320 250 362 2 3 2 53000 250 70 37000 330 385 291 2 4 2 51000 570 50 46000 480 650 288 2 5 2 51000 650. 40 26000 960 . 715 131 2 6 2 58000 100 40 27000 750 74.9 99 2 7 2. 56000 70 .60 27000 680 772 131 2 8 2 57000 240 40 27000 510 754 138 2 9 2 55000 80 30 27000 440 764 142 2 1 2 40000 210 60 79000 230 226 403 2 2 2 43000 240 50 52000 270 281 316 2 3 2 47000 920 70 38000 620 728 281 2 4 2 56000 590. 60 32000 1060 746 224 2 5 2 48000 130. 50 28000 600 782 101 2 6 2 57000 150 60 29000 580 763 106 2 7 2 58000 90 40 27000 490 772 133 2 8 2 59000 80 50 27000 500 781 113 2 9 2 49000 110 40 29000 420 770 111 2 1 3 42000 160 60; 80000 240 225 393 2 2 3 47000 240 60 56000 270 238 352 2 3 3 46000 550 80 ;63000 320 258 326 2 4 3 52000 260 70 38000 350 379 275 2 5 3 53000 1100 60 28000 860 708 119 2 6 3 59000 280 50 27000 740 726 117 2 7 3 52000 280 40 27000 530 746 122 2 8 3 56000 190 50 30000 510 753 160 2 9 3 60000 130 40 31000 460 755 167 TR = : TREATMENT L = LEVEL T = TIME - 204 -TRL T A l Zn Cu Fe Mn pH E.C. (ppm) (ppm) (ppm) (ppm) (ppm) (mmhb 2 1 3 47000 280 60 51000 290 2 85 296 2 2 3 50000 340 60 43000 350 741 240 2 3 3 50000 460 50 40000 500 547 260 2 4 3 50000 1060 60 33000 1120 739 268 2 5 3 54000 100 30 27000 1050 754 96 2 6 3 59000 310 50 28000 530 769 96 2 7 3 47000 120 60 29000 420 758 „ 111 2 8 3 56000 190 40 27000 510 751 167 2 9 3 47000 120 50 27000 420 767 167 2 1 3 50000 290 70 51000 330 333 265 2 2 3 47000 200 40 55000 300 316 275 2 3 3 47000 540 80 38000 380 479 265 2 4 3 51000 840 60 43000 530 741 281 2 5 3 52000 110 60 27000 490 752 117 2 6 3 59000 290 50 27000 ' 620 743 112 2 7 3 59000 270 50 28000 530 748 122 2 8 3 56000 310 40 28000 520 744 109 2 9 3 57000 180 40 27000 500 746 117 END OF FILE TR = TREATMENT L = LEVEL T - TIME - 205 -APPENDIX 5. 2 Ch e m i c a l A n a l y s i s o f the Overburden A c i d E x t r a c t i o n s TR L T A l Zn Cu Fe Mn - (ppm) (ppm) (ppm) (ppm) (ppm) 1 1 1 170 . 18 1 38 156 1 2 1 174 18 1 25 152 1 3 1 173 15 1 16 151 1 '4 1 194 18 2 56 155 1 5 1 134 15 1 15 151 1 6 1 170 : 19 1 17 149 1 7 1 190 16 1 53 151 1 8 1 163 18 1 40 142 1 9 1 203 15 1 26 150 1 1 1 111 7 1 14 154 1 2 1 103 13 1 16 151 1 3 1 130 6 1 16 156 1 4 1 185 .10 1 19 157 1 5 1 204 19 2 25 151 1 6 1 115 20 1 • 11 152 1 7 1 237 23 2 31 157 1 8 1 . 167 18 1 20 153 1 9 1 172 16 1 20 162 1 1 1 158 16 1 22 150 1 2 1 184 14 1 18 151 1 3 1 89 10 1 16 149 1 4 1 95 16 1 14 139 1 5 1 109 9 1 11 141 1 6 1 110 16 1 32 116 1 7 1 119 8 1 6 151 1 8 1 72 7 1 15 163 1 9 1 227 9 1 ; 18 161 2 1 1 256 60 4 5600 22 2 2 1 2180 48 20 5400 102 2 3 1 382 48 4 280 .314 2 4 1 384 26 4 320 308 2 5 1 30 5 0 30 111 2 6 1 30 3 0 20 126 2 7 1 10 3 0 20 105 2 8 1 53 9 0 4 161 2 9 1 150 7 0 10 144 2 1 1 343 59 8 4090 18 : 2 2 1 584 58 6 2500 34 2 3 1 1680 134 10" 330 25 2 4 1 410 38 4 420 350 2 5 1 169 10 1 7 299 2 6 1 178 10 1 6 275 2 7 1 220 8 2 38 150 2 8 1 216 11 2 39 153 2 9 1 191 21 1 25 199 2 1 1 431 97 6 7900 30 2.2 1 1260 232 25 10600 48 TfR = • TREATMENT L = LEVEL T = TIME - 206 -TR L T A l Zn Cu Fe Mn " • . (ppm) (ppm) (ppm) (ppm) (ppm) 2 3 1 374 118 4 360 582 2 4 1 358 12 4 320 190 2 5 1 179 9 2 26 162 2 6 1 189 9 1 30 155 2 7 1 169 6 1 20 137 2 8 1 216 7 2 33 153 2 9 1 233 6 2 39 135 1 1 2 117 14 1 14 151 1 2 2 103 12 1 39 125 1 3 2 105 6 1 16 139 1 4 2 139 15 1 19 152 1 5 2 78 14 1 11 126 1 6 2 194 15 1 21 145 1 7 2 69 8 1 11 150 1 8 2 175 15 1 18 154 1 9 2 196 9 1 21 155 1 1 2 189 15 1 39 153 1 2 2 186 17 1 21 146 1 3 2 187 15 1 35 135 1 4 2 215 12 1 24 158 1 5 2 60 6 0 59 154 1 6 2 125 14 1 15 156 1 7 2 178 15 1 23 151 1 8 2 181 16 1 21 151 1 9 2 151 8 • 1 15 154 1 1 2 46 7 0 26 142 1 2 2 50 5 0 18 146 1 3 2 98 11. 1 13 1420 1 4 2 50 7 0 27 140 1 5 2 110 9 1 24 140 1 6 2 50 9 0 14 145 1 7 2 62 9 0 11 148 1 8 2 140 12 0 20 148 1 9 2 151 14 1 15 151 2 1 2 236 78 5 4360 16 2 2 2 366 52 4 1200 28 2 3 2 406 38 3 1000 37 2 4 2 1300 81 6 1400 53 2 5 2 310 45 2 11 493 2 6 2 250 9 2 20 270 2 7 2 268 19 2 75 150 2 8 2 253 13 2 57 140 2 9 2 63 9 0 14 151 2 1 2 346 76 18 9000 14 2 2 2 3580 38 5 2120 21 2 3 2 1460 220 14 1140 29 2 4 2 2220 220 5 340 57 2 5 2 175 161 2 5 378 TR = TREATMENT L = LEVEL T ='_TIME - 207 -TR L T A l Zn Cu Fe Mn (ppm) (ppm) (ppm) (ppm) (ppm) 2 6 2 71 10 ~ 0 3 410] 2 7 2 189 8 1 13 205 2 8 2 165 8 1 30 141 2 9 2 204 8 1 41 151 2 1 .2 178 43 5 3480 13 2 2 2 382 36 5 1300 24 2 3 2 2450 657 12 2510 384 2 4 2 506 296 4 500 766 2 5 2 188 10 1 6 290 2 6 2 3 5 0 1 127 2 7 2 83 5 0 10 146 2 8 2 117 9 1 12 138 2 9 2 87 6 1 14 105 1 1 3 18 5 0 20 116 1 2 3 30 3 0 10 102 1 3 3 10 , 2 0 10 122 1 4 3 14 3 0 26 113 1.5 3 30 3 0 10 116 1 6 3 40 3 0 20 114 1 7 3 70 5 0 10 94 1 8 3 30 9 0 4 137 1 9 3 30 3 0 10 110 1 1 3 159 14 1 • 47 150 1 2 3 74 5 1 22 151 1 3 3 70 5 1 27 148 1 4 3 72 10 2 20 151 1 5 3 42 17 0 13 126 1 6 3 90 7 1 8 144 1 7 3 220 8 2 38 158 1 8 3 223 13 2 46 157 1 9 3 111 6 1 18 146 1 1 . 3: 68 5 0 13 138 1 2 3 67 5 0 45 141 1 3 3 101 7 1 17 152 1 4 3 177 8 1 27 153 1 5 3 138 6 1 22 149 1 6 3 146 6 1 23 124 1 7 3 198 5 1 32 108 1 8 3 180 8 1 27 151 1 9 3 102 5 1 11 149 2 1 3 190 552 4 3180 14 2 2 3 232 26 4 1220 17 2 3 3 320 36 4 1500 23 2 4 3 1900 142 11 1120 64 2 5 3 237 830 3 7 560 2 6 3 234 16 2 13 369 2 7 3 217 7 1 15 229 2 8 3 234 12 2 41 181 TR = = TREATMENT L = LEVEL T = TIME - 208 -TR L T A l Zn Cu Fe Mn (PPP) (ppm) (ppm) (ppm) (ppm) 2 9 3 142 13 1 20 165 2 1 3 700 78 11 1680 16 2 2 3 740 68 6 1120 118 2 3 3 880 . 288 7 6000 186 2 4 3 840 800 6 1460 910 2 5 3 106 19 1 1 257 2 6 3 200 8 1 32 152 2 7 3 144 7 1 30 166 2 8 3 143 6 1 34 154 2 9 3 128 7 1 20 160 2 1 3 1160 94 16 1440 15 2 2 3 480 84 4 1380 22 2 3 3 . 2200 304 11 3710 120 2 4 3 1220 292 4 540 184 2 5 3 191 164 2 4 440 2 6 3 103 8 1 2 259 2 7 3 114 10 1 18 200 2 8 3 154 10 1 28 138 2 9 3 148 7 1 77 138 END OF FILE TR = TREATMENT L = LEVEL T = TIME - 209 -DEVELOPMENT OF AN "INSITU" OXIDATION REDUCTION POTENTIAL MEASUREMENT TECHNIQUE Ab s t r a c t A method f o r measuring redox p o t e n t i a l s was developed. The samples were s o l u t i o n s c o l l e c t e d by pre-evacuated vacu ta ine rs from sampling po r t a l s l o ca t ed in p l e x i g l a s s columns which conta ined mine t a i l i n g s mate r i a l and overburden. The so l u t i on s were t r an s f e r r ed from the vacu ta ine r s i n to a c l o sed n i t rogen system cons t ruc ted of g l a s s , by means of a gas t i gh t s y r i n ge . A combinat ion p la t inum - re fe rence e l e c t r ode was permanently p laced i n the g l a s s apparatus which was a l so equipped w i th a s e l f - s e a l i n g stopper f o r sample i n j e c t i o n , a water b o t t l e , an i n l e t and o u t l e t f o r n i t rogen gas and f o r d ra inage . The r e s u l t s i nd i c a t ed tha t the overburden, separated from the t a i l i n g s by a grave l b a r r i e r , remained in an ox i d i z ed s t a t e . The overburden, i n d i r e c t con tac t w i th the t a i l i n g s became reduced w i t h i n the f i r s t month o f the exper iment. The t a i l i n g s were reduced f o r the e n t i r e exper iment. I r o n , manganese, copper and n i cke l were dominant ly in the reduced s t a t e , in the contaminated overburden and in the t a i l i n g s e x i s t i n g as i n d i v i d u a l ions i n s o l u t i o n . Measurements and trends i n d i c a t e t ha t the method developed i s an e f f e c -t i v e means o f measuring redox p o t e n t i a l , o f s o l u t i o n samples, wh i l e s imu l a t i ng " i n - s i t u " c o n d i t i o n s . - 210 -I n t r oduc t i on The o x i d a t i o n reduc t i on or redox po ten t i a l of a s o l u t i o n can be l o o s e l y desc r ibed as the a v i d i t y o f a substance to donate or accept e l e c t r ons ( e l e c t r o n e g a t i v i t y ) , from a r educ i b l e or o x i d i z a b l e substance, which i s a f un c t i on o f atomic s t r u c t u r e . Elements w i th a high e l e c t r o n e g a t i v i t y r e l ease more energy upon acceptance or re lease of an e l e c t r on compared wi th elements of low e l e c t r o n e g a t i v i t y . In the redox po ten t i a l measurement, e l e c t r on s are exchanged between the e l e c t rode and the elements i n s o l u t i o n , in an e l e c t r i c c e l l or ba t t e r y type o f s i t u a t i o n . In c i rcumstances of s o l u t i o n s con ta i n i ng ions dominant ly i n the ox i d i z ed s t a t e , the e l e c t r o d e ' s r o l e i s to donate e l e c t r ons to the o x i d i z e d spec ies thus caus ing an e l e c t r i c cu r r en t w i th p o s i t i v e vo l t age o r a high p o t e n t i a l . In s o l u t i on s con ta i n i ng i o n i c spec ies dominantly in the reduced form the cu r r en t i s reversed and the vo l t age i s negat ive and the po t en t i a l i s low. I t f o l l ows t h a t i n s o l u t i o n s of evenly concent ra ted o x i d i z e d and reduced spec ies the potenta l i s near ze ro . In a system con ta i n i ng severa l d i f f e r e n t i o n i c spec ies i n the ox i d i z ed s t a t e , those w i th the g rea te s t e l e c t r o n e g a t i v i t y , s p e c i f i c a l l y e l e c t r on a f f i n i t y , are reduced f i r s t , y i e l d i n g the h ighest p o t e n t i a l . With these r educ t i on s , new products are formed. Developing from t h i s , the redox po t en t i a l represents the degree of reduc t i veness of a system and i nd i c a t e s as we l l which spec ies have been reduced and which are y e t to be reduced. That i s , a s o l u t i o n which has r e l a t i v e l y low redox po t en t i a l i n d i c a t e s t ha t elements of h igh e l e c t r o n e g a t i v i t y , i f present in the s o l u t i o n , w i l l be in t h e i r reduced form at t h i s p o t e n t i a l . - 211 -There fo re , redox measurements can be used as a too l to p r e d i c t the r eac t i ons which have occurred and the re fo re minera l t r ans fo rma t i ons . Because of the po t en t i a l of the redox measurements f o r i d e n t i f y i n g mineral t r ans fo rmat i ons , i t was cons idered an ana l y s i s which would a i d i n i d e n t i f y -i ng the changes o c cu r r i ng i n the overburden in the column t rea tments , p a r t i c u l a r l y in the overburden in the Treatment 2 columns. I t was hoped t h a t the gradual changes i n redox measurements w i th t ime would a l so i n d i c a t e the mineral t rans fo rmat ions o c c u r r i n g . I n t e r e s t i n the redox ana l y s i s had a second ma.jor component and tha t was to design a p r a c t i c a l , e f f i c i e n t , economical and sound method fo r measuring redox p o t e n t i a l s . The column study prov ided the pe r f e c t s i t u a t i o n f o r supp ly ing samples which were p red i c t ed to vary i n t h e i r redox p o t e n t i a l . D i f f e r e n t from other ana lyses which have been tes ted and accepted u n i v e r s i a l l y , such as pH, no method f o r measuring redox p o t e n t i a l s has been accepted as s tandard , to date , due to a number of problems as soc i a t ed w i th the high s e n s i t i v i t y of t h i s a n a l y s i s . There fo re , the l i t e r a t u r e con ta ins as many d e s c r i p t i o n s o f techniques f o r determin ing the redox po ten t i a l of s o i l s as there are researchers at tempt ing to measure t h i s p rope r t y . The most c r i t i c a l f a c t o r i n redox po t en t i a l ana l y s i s i s the prevent ion o f oxygen con tamina t ion . Accord ing to J e f f e r y (1961) d i r e c t redox measure-ments on aerated s o i l s are sub jec t to too much e r r o r to have any s i g n i f i -i cance or p rov ide any use fu l i n f o rma t i on . The p o s s i b i l i t y o f pene t ra t i on by a i r i s d i f f i c u l t to avoid though many researchers fee l t h e i r method has d e l t w i t h t h i s problem s u f f i c i e n t l y . For example, Armstrong (1967) and Starky and Wight (1945) have developed methods f o r measuring the redox p o t e n t i a l s - 212 -of s o i l s d i r e c t l y i n the f i e l d . They attempted to c i rcumvent oxygen contaminat ion by imp lant ing the e l e c t rodes i n t o the s o i l and thus obta ined the redox po t en t i a l wh i l e the sample was under the i n f l u ence of i t s natura l environment. Others ( J e f f e r y , 1961; Yamane, 1969; Volkov e t a l . , 1975; B a i l e y and Beauchamp, 1971) have developed techniaues s u i t a b l e f o r samples brought i n t o the l a bo r a t o r y . They counteracted the e f f e c t of i n i t i a l oxygen contaminat ion caused by removing the sample from i t s environment, by i n cuba t i on . F i n a l l y , Lance and Wh is le r (1972), L inebarger e t a l . (1975), C o l l i n s and Buol (1970) and Whis le r et a l . (1974) designed methods adapted to column s t ud i e s , s i m i l a r to t h i s exper iment. They avoided oxygen contaminat ion dur ing the redox po t en t i a l measurements by imp lan t ing the e l ec t rodes permanently i n to the columns. I d e a l l y , the redox po t en t i a l measurement should be obta ined wh i l e the sample i s in i t s natura l environment i f the t rue po t en t i a l of the system i s to be ob ta i ned . In t h i s l i g h t , the permanent imp lan t ing of e l e c t r odes i n t o the columns s imu la tes an i n s i t u measurement. However, permanent imp lan t ing of e l e c t r odes was not a s u i t a b l e approach f o r t h i s experiment f o r two major reasons: i n s u f f i c i e n t e l ec t rode hard iness and subs t an t i a l c o s t s . The e l e c t r ode gene ra l l y adopted f o r redox po t en t i a l e v a l u a t i o n s , i s cons t ruc ted of p la t inum. P l a t i num ' s s u i t a b i l i t y a r i s e s from i t s chemical p r o p e r t i e s . I t i s a n on - s e l e c t i v e , i n e r t , e l e c t r i c a l conduct ing mate r i a l and to date has been found to be the most s u i t a b l e mate r i a l fo r y i e l d i n g c on s i s t e n t r e s u l t s i n redox po t en t i a l t e s t s . However, some researchers (Bohn, 1971; Ba i l e y and Beauchamp, 1971) have reported t h a t , f o l l ow i ng days of con t i nua l immersion, the p lat inum e l e c t r ode can become unrespons ive to the system's redox c o n d i t i o n s . Th is has been a t t r i b u t e d to the absorp t ion - 213 -o f substances onto the p lat inum or to p l a t i n um- su l f i d e r ea c t i on s ( Ba i l e y and Beauchamp, 1971). P la t inum e l e c t r ode s , t h e r e f o r e , r equ i r e c l ean ing pe r i od -i c a l l y . Po i son ing of the e l e c t r odes cou ld not be r i s k e d and as r e s u l t , permanent imp lan t ing was not a s u i t a b l e approach. Secondly, the expend i ture o f imp lan t ing at l e a s t two e l e c t rodes i n t o each of 18 the columns would be exho rb i t an t a t a cos t o f $168.00 each. There fore a new technique was r equ i r e d . The major goal was to design a procedure which i nc luded the b ene f i t s o f non -des t ruc t i ve sampling but r equ i r ed only one p la t inum e l e c t r o d e . Th i s paper g ives the method developed, i n d e t a i l , and d i scusses the r e s u l t s of the redox ana l y s i s i n terms of mineral t rans fo rmat ions o c cu r r i ng in the contaminated overburden. F i n a l l y an eva lua t i on of the method i s g i v en . Method The technique r eau i r ed two major achievements. F i r s t , a sample, r ep resen t ing chem i ca l l y the column ma t e r i a l s had to be c o l l e c t e d non-d e s t r u c t i v e l y w i th the assurance of non-contaminat ion by oxygen. Secondly , a procedure and apparatus had to be designed such tha t the sample cou ld be brought i n t o con tac t w i th the p lat inum e l e c t r ode , a l s o w i th a guarantee from oxygen con ta c t . The f i r s t step was so lved by permanently imp lan t ing ceramic sampling cups i n t o the columns. These have the capac i t y of ob ta i n i ng chemical e q u i l i b r i u m w i th the s o i l s i n con tac t w i th them (as d i scussed i n Chapter 4 . 3 . 6 ) . The sampling appara t i were p laced at two l e v e l s i n the overburden, - 214 -proximate to the o ve r bu rden - t a i l i n g s boundary, where the most i n t e n s i v e r eac t i ons were p red i c t ed to occur . The second overburden por ta l was s i t u a t ed below the sur face of the overburden near the top o f the columns. In the t a i l i n g s , one por ta l was p laced below the water t ab l e and one above. The sampling apparatus i s desc r ibed in d e t a i l in Chapter 4 . 3 . 6 and i s dep i c ted in F i gu re 4 . 1 , Chapter 4. The needle p ro t rud ing from the apparatus was sea led o f f dur ing the non-sampl ing pe r i od s . The j o i n t s were r e g u l a r l y l u b r i c a t e d wi th stop-cock grease in order to ma inta in a complete grease f i l m p revent ing d i r e c t movement of a i r through l e a k s , i f any, at the j o i n t s . The columns were watered on a r egu l a r bas i s as desc r ibed in Chapter 4 . 3 . 10 . . A pe r i od of 24 hours e lapsed before sampling was c a r r i e d out . By t h i s t ime the added water was cons idered to have a t t a i ned e qu i l i b r i um wi th the column ma t e r i a l s as d i scussed in Chapter 4 . 3 . 1 0 . The water app l i ed to the sur face was exposed to the atmosphere and thus in t roduced oxygen to the system to some ex ten t . Th i s was not c r i t i c a l to the overburden in the Treatment 1 columns which were h igh l y des i c ca ted dur ing the i ncuba t i on per iods (as d i scussed in Chapter 4 .3 .10) and thus the overburden was c o n t i n u a l l y exposed to oxygen. The overburden in the Treatment 2 columns remained near s a t u r a t i o n , even dur ing the i ncuba t i on per iods (d i scussed in Chapter 4 . 3 . 1 0 ) . However, the i n t r odu c t i o n of oxygen through sur face water ing was not cons idered c r i t i c a l as the per iod of t ime requ i red f o r e q u i l i b r i u m has been much l e s s than 24 hours i n many s tud i e s i n v o l v i n g redox po t en t i a l measurements. Armstrong (1967) found tha t e q u i l i b r i u m in a water logged s o i l was reached i n 1-2 minutes. Starky and Wight (1945) reported tha t e q u i l i b r i u m was reached w i t h i n 5 minutes on s o i l samples measured d i r e c t l y f o r redox p o t e n t i a l . I t should a l so be noted t ha t - 215 -oxygen d i f f u s i o n r a te s have been found to f a l l o f f r a p i d l y w i th sha l low depths of s o i l s (eg. 5 cm), e s p e c i a l l y under sa tura ted cond i t i on s (Leman and E r i c k s o n , 1952). Thus, the amount of oxygen p o t e n t i a l l y contaminat ing the overburden would decrease s u b s t a n t i a l l y w i th depth. There fo re , the pe r i od of 24 hours was cons idered adequate f o r the added water and overburden to reach e q u i l i b r i u m , w i th respec t to oxygen. The l i q u i d samples were removed from the columns under suc t i on by means of p i e r c i n g the s e l f - s e a l i n g stoppers of ac id washed, prevacuumed vacu-t a i n e r s by the sy r i nge component of the sampling apparatus . In t h i s way the samples were t r an s f e r r ed d i r e c t l y i n to a i r - t i g h t con ta ine r s w i thout exposure to the atmosphere. The second pa r t o f the procedure i nvo l ved b r i ng i ng the sample i n t o con tac t w i th the p lat inum e l e c t r ode wi thout oxygen exposure. One method, which has been accepted, i nvo l ves pass ing a p r o t e c t i v e gas eg. pure n i t r o -gen, through o r over the sample dur ing the redox ana l y s i s (Pe te r sen , 1966). A method i n v o l v i n g t h i s approach was e labora ted in the form of a g love box. The g love box, cons t ruc ted of p l e x i g l a s s , measured 1 m ( length) x 1 m (depth) x 0.75 m ( h e i g h t ) . An Orion p lat inum redox combinat ion e l e c t r ode (Model 96-78) measuring roughly 12 mm in diameter and a Radiometer meter (Model pHM 62) were used. As commerc ia l ly a v a i l a b l e n i t rogen conta ins an undef ined amount of oxygen a s p e c i a l t y gas was ordered f o r the a n a l y s i s . I t was guaranteed 99.99% pure n i t r ogen . Th is equipment requ i red fo r the redox p o t e n t i a l a n a l y s i s was p laced in the g love box which was then sea led o f f . The box conta ined two o u t l e t s . One was connected to an a s p i r a t o r , f o r removal of a i r from the box. The other was connected to the n i t rogen tank by t ub i ng . The a i r was pumped out of the box and the n i t rogen was pumped i n - 216 -f o r 1 hour . Before the rubber stoppers were removed from the vacu ta ine r s and, the e l e c t rodes i n s e r t e d , a match was l i t to t e s t f o r an oxygen f ree atmosphre. When i g n i t i o n cou ld not be obta ined the system was ready f o r the a n a l y s i s . A l though t h i s method appeared p romis ing , the g love box was too l a r g e to have con t ro l o f the atmosphere and was suspected of l e ak i ng as no s t a b i l i t y cou ld be obta ined in the redox po t en t i a l read ings even a f t e r 5 minutes of cont inuous immersion of the e l e c t rode in the sample. The long per iod of t ime, requ i red per sample to reach e qu i l i b r i um made t h i s method i m p r a c t i c a l . There fo re , the g love box was abandoned and a sma l le r system was des igned. The sma l le r system i s dep i c ted d i a g r ama t i c a l l y in Appendix 6.1 and pho tog r aph i c a l l y i n Appendices 6.2 and 6.3 (the pH e l e c t r ode i s not i nc luded in any of these append ices) . The bas i c theory invo l ved the i n j e c t i o n of the sample i n to the g l a s s apparatus con t a i n i ng a pure n i t rogen atmosphere and the p lat inum e l ec t rode and i n i t i a l l y the pH e l e c t r o de . The g l a s s chamber was 27 mm in diameter and 8 cm in depth, on ly l a r ge enough to con ta in the two e l e c t r ode s . One o u t l e t , extending from the apparatus , a t an ang le , was designed to t i g h t l y house a rubber stopper 15 mm i n d iameter . Each stopper was cons t ruc ted w i th a s e l f - s e a l i n g p o r t i o n . A second o u t l e t extended a t an ang le , oppos i te the s topper . Th i s was connected to the n i t r ogen gas tank by c l e a r t u b i ng . A t h i r d o u t l e t was sha l low and s l i g h t l y wider than the water d i spens ing cap from a standard d i s t i l l e d water b o t t l e . A d i s t i l l e d water cap was permanently connected i n t o the o u t l e t and the j o i n t was covered by a rubber sheath t i g h t l y secured w i th t h i n f l e x i b l e w i r e . The t i p of the cap extended i n to the apparatus , - 217 -APPENDIX 6.1 Ox i da t i on - r educ t i on p o t e n t i a l measurement o f a sample, c a r r i e d out i n an atmosphere o f pure n i t r ogen gas. - 218 -APPENDIX 6.2 D i s t an t View of Apparatus Used i n Ox i d a t i o n -Reduct ion Po t en t i a l Measurement. o r i en t ed towards the e l e c t r ode s . The j o i n t was designed to be f l e x i b l e such t ha t the e l e c t rodes cou ld be r i n s ed we l l a t va r i ous angles between samples. The e l e c t r odes were held in p lace by a p l a s t i c d i s c i n which holes were d r i l l e d to the exact d iameter of the e l e c t r o de s . (The pH e l e c t rode was 5 mm in diameter and the redox e l e c t r ode was 12 mm in d iameter . ) A ho l low p iece of p l e x i g l a s s tub ing was a l so a t tached to the d i s c and served as the d i s c -hand le , as we l l as an o u t l e t f o r gas l e av i ng the system. The e l e c t rodes were he ld in p lace by the d i s c and were pos i t i oned as deep as po s s i b l e i n t o the oval-bottomed g l a s s apparatus w i thout touch ing i t . Th i s had the e f f e c t o f reduc ing the volume of the sampling chamber as the ho ld ing d i s c was moved down as f a r as po s s i b l e i n to the apparatus . With the s e n s i t i v e po r t i on s of the e l e c t rodes pos i t i oned a t the base of the chamber the amount of sample r equ i r ed to make con tac t w i th the e l e c t rodes was kept a t a minimum (3 m i s ) . The e l ec t rodes and the i n t e r na l atmosphere were sealed from the outer atmosphere by a dense, compacted plug of c l a y (p las tescene) which was f i r s t heated to improve i t s p l i a b i l i t y . Th is p lug was roughly 3.8 cm in depth and was u l t i m a t e l y l u b r i c a t e d w i th s tock-cock grease to i nsu re tha t no micro-pores connected the i n t e r na l and externa l atmospheres. A f i n a l o u t l e t , a t the base of the apparatus, was pos i t i oned f o r easy dra inage of the samples. Amber tub ing was at tached to the o u t l e t and the t i p of the tub ing was kept under water on a permanent b a s i s . Dur ing a n a l y s i s , t h i s prevented backf low of a i r from the atmosphere up i n to the tub ing and thus i n t o the chamber. I t was clamped o f f except f o r dra inage purposes. With the apparatus complete ly assembled, c o n t r o l l e d gas f low was i n i t i a t e d . The water b o t t l e , f i l l e d to capac i t y w i th d i s t i l l e d water, was - 220 -' p laced under vacuum to remove a l l gases. Th i s was then exped ien t l y at tached to the cap. The apparatus was then f i l l e d w i th water , from the at tached water b o t t l e , f o r c i n g n i t rogen gas to bubble through the water and out of the o u t l e t tube which was at tached to a gas f low meter. At a l l t imes, the gas f low was mainta ined s u f f i c i e n t l y to fo r ce the metal bea r i ng , i n the f lowmeter, to a p o s i t i o n near the top of i t thus i n d i c a t i n g p o s i t i v e gas f l ow from the chamber to the ex te rna l atmosphere. Th i s insured tha t a i r never entered the chamber. S t i l l ho ld ing the b o t t l e i n a squeezed p o s i t i o n , the water was s l ow ly dra ined from the chamber by r e l e a s i n g the hose clamD, which tempora r i l y sea led the tub ing extend ing from the base of the chamber. I t was important to d ra i n the chamber s lowly to avo id excess ive suc t i on which would draw atmospher ic gases through the o u t l e t tube above, i n t o the chamber. D ra i n i ng a l lowed the chamber to f i l l w i th n i t rogen gas. A f t e r 15 s e c , the g r i p on the water b o t t l e was s low ly re leased and n i t rogen gas from the chamber was drawn i n t o the empty volume of space in the water b o t t l e c reated by the l o s s of water i n the chamber w a t e r - f i l l i n g s t ep . The f i l l i n g and d r a i n i ng procedure was repeated tw i ce . The apparatus was then f i l l e d one more t ime w i th d i s t i l l e d water . Gas was bubbled through the water f o r 15 min. and then was d ra ined . The apparatus was ready fo r the pH and redox measurements. I t was cons idered important to take both the redox and pH measurements a t the same time as each decrease in pH has been found to inc rease the redox po t en t i a l by 59 o r 60 mv (Starky and Wight, 1945; L indsay and Sad iq , 1978) . The inc rease i n a c i d i t y a f f e c t s the redox parameter as the e l e c t r o de , i n a - 221 -sense, confuses hydrogen ions ( H + ) , a s soc i a t ed w i th pH, to those assoc i a ted w i th the redox p o t e n t i a l . The l a s t major step i n t h i s technique was to s u c c e s s f u l l y remove the sample from the vacu ta ine r and depos i t i t i n t o the g l a s s apparatus. The sample was removed from the vacu ta ine r w i th a 5 cc g a s - t i g h t sy r inge which was designed to seal o f f the sample from a i r , a t both the plunger and needle ends (Pressure-Lok gas s y r i nge , Se r i e s D, P r e c i s i o n Sampling C o r p . ) . The vacu ta ine r s were gene ra l l y f i l l e d to the top. In s i t u a t i o n s in which a f u l l sample cou ld not be ex t r ac ted from the columns ( f o r reasons such as d i scussed in Chapter 5 . 3 . 2 ) , the u n f i l l e d space in the vacu ta ine r s was s t i l l under vacuum. Th i s presented d i f f i c u l t y i n removing a sample. There fo re , roughly 5 cc of n i t rogen gas was ex t rac ted from the g lass appara-tus by the sy r inge and i n j e c t ed i n t o the v a cu t a i ne r s . Th i s f a c i l i t a t e d sample removal . The sample was then i n j e c t ed i n t o the g lass apparatus such tha t the s e n s i t i v e po r t i ons of the e l ec t rodes were immersed in sample. As noted, 3 mis of sample was r e qu i r e d . The p o t e n t i a l s were then recorded . The e l e c t rodes were plugged i n t o separate Radiometer (pH) meters. However steady read ings cou ld not be obta ined f o r e i t h e r measurement. Therefore i t was suspected, and found to be c o r r e c t , tha t the e l ec t rodes were i n t e r f e r i n g w i th each o the r . There fore the pH e l e c t r ode was removed from the apparatus . The gap caused by the miss ing e l ec t rode was f i l l e d by c l a y . The read ing accepted as the redox po ten t i a l was the f i r s t number which remained s t ab l e f o r a minimum of 15 sec . Th i s was an a r b i t r a r y t ime l i m i t . Once the redox measurement was made, the sample was dra ined and the - 222 -e l e c t r ode was r i n sed w i th d i s t i l l e d water . The sy r inge was a l so r i n sed between samples. The e l e c t r ode was t e s t ed p e r i o d i c a l l y , w i t h spec i a l buf fered s o l u t i o n s , to check i t s respons iveness . I t was c leaned, as r equ i r ed , wi th warm n i t r i c a c i d accord ing to the method descr ibed by Rrown (1933). The rubber stoppers of the redox chamber were rep laced f r equen t l y , as r equ i r ed . The samples were mainta ined at 25°C f o r the redox po t en t i a l a n a l y s i s . Three samples from each t reatment , a t each l e ve l fo r each of the 9 months, were t e s t e d . The pH was l a t e r read on these samples. The p lat inum combinat ion redox e l ec t rode was f i l l e d w i th a s o l u t i o n which had c h a r a c t e r i s t i c s matching those o f a convent iona l calomel re fe rence e l e c t r ode (244 mv). A spec i a l s o l u t i o n (4 NKC1 sa tura ted wi th s i l v e r c h l o r i d e ) w i th a po t en t i a l of 199 mv was used in the e l e c t r ode f o r the h i gh l y contaminated samples as recommended by the Or ion company. A l l read ings were ad jus ted r e l a t i v e to the normal hydrogen e l e c t r ode (E n ) accord ing to the f o l l ow i ng equat ion : E h = E 0 +C where E n = ox i da t i on reduc t ion po t en t i a l of the sample r e l a t i v e to the normal hydrogen e l e c t r o de , f o l l ow i ng the i n t e r n a t i o na l s ign conven t i on . E 0 = po t en t i a l developed by the p lat inum redox e l e c t r o de . C = po t en t i a l developed by the re fe rence e l ec t rode po r t i on r e l a t i v e to the normal hydrogen e l e c t r ode . - 223 -As a l ready noted, redox p o t e n t i a l s i nc rease w i th i n c r ea s i ng a c i d i t y . To remove pH v a r i a b i l i t y between the s o l u t i o n s redox p o t e n t i a l s are o f ten ad jus ted to pH 7 by m u l t i p l y i n g the d i f f e r e n c e between pH 7 and the pH o f the sample by -60 mv (o r -59) per pH u n i t , i f the sample i s more ac id than pH 7, or by 60 mv (or 59) i f the sample i s more bas i c than pH 7, and adding t h i s product to the o r i g i n a l po t en t i a l o f the sample eg. adjustment of the po t en t i a l of a sample from pH 2 to pH 7 r equ i r e s 5 x -60 mv = -300 mv, which i s added to the o r i g i n a l sample po t en t i a l (Bohn, 1971; L indsay and Sad iq , 1978; S ta rky and Wight, 1945). A l l redox measurements were adjusted to pH 7. The so l u t i on s se l e c t ed a t Level D from both treatments averaged pH 8 and at Level C, Treatment 1, pH 8 . 5 . The pH o f the s o l u t i o n s c o l l e c t e d a t Level C from the Treatment 2 columns, decreased w i th time accord ing to F igu re 5 . 1 ( a ) , Chapter 5 and were adjusted a c co rd i ng l y . The pH of the t a i l i n g s s o l u t i o n s averaged 2 .0 . - 224 -RESULTS AMD DISCUSSION The redox p o t e n t i a l , Eh, of the s o l u t i o n s c o l l e c t e d at Level D, f o r both Treatments 1 and 2 d id not vary w i th time or between treatments and, ad jus ted to pH 7, averaged 485 mv ± 30. The average po t en t i a l of the s o l u t i o n s c o l l e c t e d from Level C, Treatment 1, was s l i g h t l y h igher , 525 mv±45, but this^ d i f f e r en ce i s not cons idered s i g n i f i c a n t . The average po t en t i a l o f the s o l u t i o n s c o l l e c t e d from Level C, Treatment 2, however, was much lower , and adjusted to pH 7, averaged 315 mv i n c r ea s i ng from 228 mv, a f t e r 1 month t o 346 mv w i t h i n 6 months, ma in ta in ing t h i s va lue fo r the l a s t 3 months. The redox po t en t i a l measurement o f the t a i l i n g s d id not vary between t rea tments , l e v e l s , or w i th t ime, averag ing 200 mv±35 throughout the exper iment. P a t r i c k and Mahapatra (1968) have dev ised a c l a s s i f i c a t i o n scheme i n which the s o l u t i o n s from the columns can be p laced i n t o four broad ly based ca tego r i e s accord ing to t h e i r redox p o t e n t i a l , adjusted to pH 7. In t h e i r system, o x i d i z ed s o i l s have p o t e n t i a l s (Eh) g rea te r than 400 mv, moderately reduced s o i l s have p o t e n t i a l s of about 100 to 400 mv, reduced 100 to -100 mv and h i gh l y reduced s o i l s -100 to -300 mv. Accord ing to t h i s system, the overburden, in the Treatment 1 columns and in the Treatment 2 columns, a t l e a s t a t Level D, was i n a h i gh l y o x i d i z ed s t a t e . The overburden in the Treatment 1 columns became des i c ca ted dur ing the i ncuba t i on per iods w i th mois ture tens ions of 8 bars recorded at Level D and 4 bars a t Level C (Chapter 4 . 3 . 1 0 ) . In s o i l s , w i th tens ions in t h i s range the l a r ge and medium pores are a i r f i l l e d w i th on ly the micro-pores con ta i n i ng water. Th is c ond i t i on permi t ted atmospheric oxygen-contact w i t h the overburden mate r i a l at the sur face of the columns and a t depth. - 225 -The overburden i n the Treatment 2 columns was s i t u a t ed in the " c a p i l l a r y f r i n g e " zone of the wate r tab le l o ca ted in the t a i l i n g s . In t h i s s i t u a t i o n the pores are dominant ly f i l l e d w i th water . However, evapora t ion near the sur face r e su l t e d in mois ture tens ions of roughly 0.2 ba rs . There-f o r e , near the sur face o f the Treatment 2 columns, the l a r ge and a po r t i on of the medium pores or vo ids are p red i c t ed to be in a dra ined c ond i t i o n a l l ow i ng the c i r c u l a t i o n of atmospheric oxygen. The oxygen i n f i l t r a t i n g the l a r ge and medium pores d i f f u s e d i n t o the surrounding w a t e r f i l l e d pores , e s s e n t i a l l y o x i d i z i n g the s o i l system at t ha t depth. Th i s i s cons idered to be dominant ly a " su r face " phenomenon as research i n d i c a t e s tha t the oxygen d i f f u s i o n ra te in s o i l s , g ene ra l l y f a l l s o f f r a p i d l y w i th depth, approaching a constant ra te of change a t roug ly 10 cm (Lemon and E r i c k son , 1952). In a study by Lemon and E r i c k son (1952) the oxygen d i f f u s i o n ra tes of a medium sandy s o i l which had 95% of the pores f i l l e d wi th water , decreased from 70 gram X 10~^/sq. cm/min. a t the sur face to 20 gram X 10"^ X sq.cm/ min. a t a 10 cm depth f u r t h e r decreas ing to 5 gram X 10 - ^/sq.cm/min. a t 20 cm. Th is pa t t e rn g r e a t l y reduces oxygen content w i th depth i n sa tu ra ted or nea r - sa tu ra ted s o i l s (Lemon and E r i c k son , 1952). These f a c t o r s are s u f f i c i e n t to exp l a i n the o x i d i z ed s ta tus o f the s o l u t i o n s c o l l e c t e d at Leve l D in the Treatment 2 columns. The po t en t i a l of the s o l u t i on s c o l l e c t e d at Level C i n the Treatment 2 columns and a t Leve l s A and B, i n d i c a t ed tha t the contaminated overburden and the t a i l i n g s were moderately reduced, accord ing to P a t r i c k ' s and Mahapatra 's c l a s s i f i c a t i o n system. The t a i l i n g s a t Level A were submerged throughout the exper iment. The manometer apparatus i n d i c a t ed tha t the t a i l i n g s a t Level B in both - 226 -t reatments and at Level C in the Treatment 2 columns were a t nea r - sa tu ra ted c ond i t i o n s . In o ther s tud i e s i n v o l v i n g water- logged s o i l s , lower redox p o t e n t i a l s have been recorded. Wh i s l e r e t a l . (1974) noted redox measurement (Eh) o f 44 mv ( E 0 = -200 mv) in f looded s o i l s . J e f f e r y (1961) recorded redox measurements as low as -151 mv in s o i l s p laced in s tand ing water . The r e l a t i v e l y high p o t e n t i a l s (between 200 and 346 mv) recorded fo r the s o l u t i o n s c o l l e c t e d from the t a i l i n g s and the Level C, Treatment 2 over-burden, are cons idered to be a response of the m a t e r i a l s , to cons tan t exposure of smal l concen t ra t i ons of oxygen from above and below. From above, oxygen s l ow l y , d i f f u s e d through the overburden and, from below, through the wa te r tab l e which was cons t an t l y exposed to oxygen and c on t i n -uous ly drawn upon as a response to evaporat ion occu r r i ng at the su r f a ce . The lower p o t e n t i a l s recorded in water logged s o i l s are a t t r i b u t e d to the i n f l u ence of o rgan i c matter and/or m i c rob i a l popu l a t i ons , and g rea te r s o i l depth (Starky and Wight, 1945; J e f f e r y , 1961; Wh i s l e r e t a l „ 1974; Bohn, 1971). As o rgan ic matter content and m i c rob i a l popu la t ions were cons idered to be zero to t r a ce in the columns and as the columns were sha l low i n depth, the h igh l y reduced p o t e n t i a l s of natura l water logged systems cou ld not be a t t a i n ed in t h i s exper iment. As noted in the i n t r o d u c t i o n , the redox po t en t i a l measurement can be important as an i n d i c a t o r o f the spec ies of m inera l s present or o f the i o n i c s t a t e of the elements o c cu r r i ng in the sample. The redox po t en t i a l of the overburden a t Level C i n the Treatment 2 columns was lower than the over-burden a t Level D in those columns, and in the Treatment 1 columns. Th is suggests t ha t a chemical d i f f e r e n c e e x i s t ed between the contaminated and non-contaminated overburden and a l s o , the contaminated overburden conta ined a h igher p ropo r t i on of reduced i o n i c forms. - 227 -P a t r i c k and Mahapatra (1968) have compi led a l i s t o f the i o n i c forms of some m e t a l l i c ions which might be expected a t va r i ous redox p o t e n t i a l s (ad jus ted to pH 7 ) . They suggest t ha t a t pH 7, n i t r a t e i s reduced at a redox po t en t i a l (Eh) o f 225 mv, manganese ( I I I - I V ) a t about 200 mv, i r on ( I I I ) a t 120 mv and s u l f a t e a t roughly -150 mv. However, Gotoh and Yamashita (1966) repor ted 280 mv fo r i r on ( I I I ) reduc t ion and 100 mv f o r s u l f a t e r e du c t i o n , a t pH 7. Accord ing to them, a po t en t i a l of 270 mv, approx imate ly denotes the onset o f reduc ing cond i t i on s f o r n i t r ogen , manganese, and i r on in s o i l s . Accord ing to P e a r s a l l and Mortimer (1939) the change-over from reduc ing to o x i d i z i n g cond i t i on s i n natura l systems takes p lace a t 230 mv (350 mv at pH 5) and fe r rous i r o n ( F e 2 + ) d isappears above t h i s p o t e n t i a l . The c o n f l i c t i n data i n d i c a t e s t ha t d i f f e r en ce s of op in ion occur among researchers suggest ing the e lus i veness of c on s i s t e n t redox p o t e n t i a l s as r e l a t e d to the components of the redox system. Accord ing to Bohn (1971) the i n s t a b i l i t y and i r r e p r o d u c i b i l i t y o f redox p o t e n t i a l s , con ta i n i ng a v a r i e t y o f redox coup les , i n d i c a t e s t ha t the measurement of redox p o t e n t i a l s , down to the m i l l i v o l t , i n natura l systems, has l i t t l e s i g n i f i c a n c e . A lso Bohn notes t ha t "the u t i l i t y o f redox p o t e n t i a l s , s i m i l a r to so many other measurements i n na tu re , i s in t h e i r i n t e r p r e t a t i o n by a knowledgeable obse rve r " . With the redox po t en t i a l o f the s o l u t i o n s c o l l e c t e d from the t a i l i n g s , averag ing 220 mv i t would appear, from the data prov ided by the above au tho r s , t ha t i t i s l i k e l y t ha t i r on and manganese occurred in the reduced form. With the redox po ten t i a l of the s o l u t i o n s ex t r ac ted from the contam-ina ted overburden, averag ing 313 mv and ranging from 228 to 346 mv, i t appears t ha t i r o n and manganese were present i n the o x i d i z ed form. - 228 -Accord ing to P ea r s a l l and Mort imer (1939) and Gotoh and Yamashita (1966) i r on (and probably manganese) occurred in the reduced form ea r l y i n the experiment i n the contaminated overburden, i n d i c a t ed by a po t en t i a l of 228 mv. I t i s po s s i b l e t ha t reduced, mobi le manganese and i r on migrated from the t a i l i n g s i n t o the overburden at Level C, i n the Treatment 2 columns e a r l y in the experiment and were thus re spons ib l e fo r the r e l a t i v e l y low redox p o t e n t i a l s i n the f i r s t few months o f the experiment which were s i m i l a r to those of the t a i l i n g s . As the f i n a l po t en t i a l o f the s o l u t i o n s e x t r a c t ed from the contaminated overburden was h igher a t the end of the exper iment, the overburden was po s s i b l y exposed to g rea te r o x i d i z i n g c ond i t i o n s be ing tha t much c l o s e r to the sur face and tha t much more d i s t a n t from the water t a b l e . T h e r e f o r e , ' f t i s conce ivab le t ha t once in the over-burden environment, the t ranspor ted manganese and i r o n were p r og r e s s i v e l y o x i d i z ed r e s u l t i n g in an inc rease in po t en t i a l w i th t ime. A f u r t h e r examinat ion o f redox l i t e r a t u r e , i n p a r t i c u l a r the Eh-pH diagrams compi led by Ga r r e l s and C h r i s t (1965), suggests tha t i r o n , manganese, copper and n i cke l in the contaminated overburden were in the reduced s ta te and in i o n i c form by the 2nd month of the experiment and perhaps by the end of the 1st month o f the experiment i n some Treatment 2 columns, u n t i l the t e rm ina t i on of the p r o j e c t . These diagrams suggest t ha t the p r a c t i c e o f ad j u s t i ng s o l u t i o n s or redox data to pH 7 can y i e l d f a l s e i n t e r p r e t a t i o n s . For example, the non-adjusted redox po ten t i a l o f the s o l u t i o n s c o l l e c t e d from the contaminated overburden in the 8th month averaged 646 mv at pH 2. Converted to pH 7, the po ten t i a l becomes 472 mv. At pH 2 w i t h a po t en t i a l of 646 mv i r on i s i n the reduced form ( F e 2 + ) on the Eh-pH diagrams, remaining as an i n d i v i d ua l ion in s o l u t i o n . Transformed to - 229 -pH 7, i r o n becomes l o ca ted in the o x i d i z ed po r t i on o f the diagram, i n the form of hematite (Fe203). S i m i l a r l y , manganese, f o r the same sample i s i n the reduced form (Mn 2 + ) at pH 2 and a t a redox po t en t i a l o f 646 mv but at pH 7, the diagram i n d i c a t e s the sample would conta in roughly 50% manganese in the reduced form as an i n d i v i d u a l i o n , and 50% as rhodochros i t e (MnC03). From G a r r e l ' s and C h r i s t ' s diagrams i t a l so becomes Obvious tha t i n a system c o n s i s t i n g of a number o f redox coup les , Eh and pH data are not s u f f i c i e n t parameters necessary to p r e d i c t the m ine ra l s p resen t , as the minera l s which do form at set pH and Eh c o n d i t i o n s , are a l so c o n t r o l l e d by the i n d i v i d u a l a c t i v i t y o f the e lements. Changes in a c t i v i t y a f f e c t changes in the m inera l s formed. There fo re , the data c o l l e c t e d on the redox p o t e n t i a l s and pH are i n s u f f i c i e n t f o r f i rm i d e n t i f i c a t i o n of the mineral t r ans fo rma t i ons , i f any, which occurred in the overburden as a r e s u l t of i t s c on t a c t with, the t a i l i n g s . Desp i te t h i s f a c t , t h i s redox po ten t i a l e xe r c i s e i s va luab le in tha t a p r a c t i c a l and economical technique f o r measuring redox p o t e n t i a l s , has been developed in which the measurements can be cons idered " i n s i t u " and thus c l o s e l y resemble the po ten t i a l of the s o i l system, unaf fec ted by d i s t u r b -ance. As w e l l , t h i s method appears to be e f f e c t i v e in e leminat ing oxygen contaminat ion o f the samples. The read ings on the meter d id not change r a p i d l y but reached a s t ab l e po in t gene ra l l y w i t h i n 5 seconds of the i n j e c t i o n . In the g love box, the read ings o f s o l u t i o n s c o l l e c t e d from the non-contaminated overburden changed r a p i d l y and con t inuous l y and they d i d not s t a b i l i z e ever a f t e r 3 min. Th i s i s na tura l f o r h i gh l y o x i d i z ed samples exposed to oxygen. In aerated s o i l s , o x i d i z ed ions are present only a t low - 230 -/ concen t ra t i ons and the re fo re oxygen exchange c u r r en t s , a t the e l e c t r ode are low (Bonn, 1971). Th is causes the s o l u t i o n to be poor ly poised and the cu r r en t to d r i f t . The s o l u t i o n s c o l l e c t e d from the t a i l i n g s d id not change even in the g love box but were s t ab l e almost immediate ly . Th i s i s a l so natura l f o r i n f looded s o i l s the g rea te r concen t ra t i ons or r edox -ac t i ve ions and the high exchange cu r ren t s o f hydrogen b r i ng about g rea te r po ise and cu r r en t s t a b i l -i t y (Bohn, 1971). Th i s technique can a l so be t ranspor ted to the f i e l d . For example, s tu rdy , f i x ed frames cons t ruc ted to hold p l e x i g l a s s tubes w i th the open end o f the tubes p lanted in a water logged s o i l and the "skyward" end sea led by a needle stoppered w i th neoprene. These cou ld represent the e x t r a c t i o n apparatus i n the columns. L e f t i n the s o i l f o r long per iods of t ime s o l u t i o n s in e q u i l i b r i u m w i th the s o i l , cou ld be ex t rac ted us ing the v a cu t a i n e r s . Some cau t i on on the use of vacu ta ine r s should be expressed here. A study by Freidman et a l . (1978) i nd i c a t ed tha t some leakage of vacu ta ine r s can occur . Although t h e i r methods leave room fo r e r r o r , they d id f i n d an i n f i l t r a t i o n , i n t o 30 ml vacu ta ine r s o f approx imate ly 0.4 ppm oxygen (O2) over a 6 week pe r i od . In a study by Pea r s a l l and Mort imer (1939) as l i t t l e as 0.5 ppb was thought to be capable of ma in ta in ing o x i d i z i n g cond i t i on s i n c e r t a i n environments. Therefore i t i s adv i sab le to measure the redox po t en t i a l o f the samples as exped i en t l y as p o s s i b l e . As a r e s u l t of the development and t e s t i n g o f t h i s and o ther methods w i th the s o l u t i o n s c o l l e c t e d from the columns 8 months e lapsed between c o l l e c t i o n and redox a n a l y s i s . - 231 -SUMMARY AND CONCLUSIONS The redox p o t e n t i a l , Eh, o f the s o l u t i o n s c o l l e c t e d at Level D, f o r both Treatment 1 and 2 and a t Level C, Treatment 1, adjusted to pH 7, averaged roughly 500 mv, i n d i c a t i n g tha t the s o l u t i o n s were h i gh l y o x i d i z e d . The po t en t i a l o f the s o l u t i o n s c o l l e c t e d from Level C, Treatment 2 was much lower and, ad jus ted to pH 7, averaged 315 mv. The po t en t i a l of the t a i l i n g s s o l u t i o n s d id not vary between t reatments , l e v e l s , or w i th t ime , averag ing 200 mv a t pH 7. The s o l u t i on s from the contaminated overburden (Level C, Treatment 2) and from the t a i l i n g s are c l a s s i f i e d as moderate ly reduced. In many i n s t ances , s o i l s which have been submerged are more s t r ong l y reduced. However, the r e l a t i v e l y sha l low depth of the ma t e r i a l s i n the columns, the v i r t u a l absence of o rgan ic matter and m i c rob i a l popu la t ions in the m a t e r i a l s , and the exposure o f the ma t e r i a l s to a i r from above and, from below through the wa te r t ab l e , s u f f i c i e n t l y exp l a i n s the r e l a t i v e l y h igh redox p o t e n t i a l s o f the ma t e r i a l s i n the columns, i n c l u d i n g the submerged t a i l i n g s , i n comparison w i th natura l systems. A rev iew o f the l i t e r a t u r e i n d i c a t e s d i f f e r en ce s i n op in ion on the chemical r eac t i on s occu r r i ng a t va r i ous redox p o t e n t i a l s . An examinat ion o f the Eh-pH diagrams suggests t ha t ad j u s t i ng redox p o t e n t i a l s o r s o l u t i o n s to pH 7 can r e s u l t i n erroneous i n t e r p r e t a t i o n s o f chemical r eac t i on s or minera l t r ans fo rma t i ons . Therefore the eva l ua t i on of the redox data should be the data generated a t i t s natura l pH. The redox and pH data i n d i c a t e s t h a t the meta ls present i n the uncon-taminated overburden are in the ox i d i z ed s t a t e . In the contaminated over-- 232 -burden and in the t a i l i n g s , i r o n , manganese, n i c ke l and copper occurred in t h e i r reduced forms, e x i s t i n g as i n d i v i d ua l ions in s o l u t i o n . The l i t e r a t u r e a l so i nd i c a t ed tha t the i d e n t i f i c a t i o n of chemical reac-t i on s and mineral t rans fo rmat ions cannot be made s o l e l y on Eh and pH da ta . In fo rmat ion on the a c t i v i t y o f the ions i n s o l u t i o n i s a l s o r e qu i r e d . The method developed f o r measuring the redox po ten t i a l i s cons idered p r a c t i c a l , e f f i c i e n t , economical and an e f f e c t i v e means of ob ta i n i ng accura te redox p o t e n t i a l s . As w e l l , the procedure y i e l d s samples which c l o s e l y resemble i n - s i t u c o n d i t i o n s . In the a n a l y s i s , the read ings s t a b i l -i z ed r a p i d l y , i n d i c a t i n g proper opera t i on of the apparatus. The method i nvo l ves the use of vacu ta ine r s and some cau t i on should be exe r c i sed w i th t h e i r use. One study pub l i s hed , found tha t very small concen t ra t i ons of oxygen accumulated in sealed vacu ta i ne r s over t ime. Therefore users are adv ised to measure the redox po t en t i a l of samples as exped i en t l y as po s s i b l e a f t e r c o l l e c t i o n . - 233 -LITERATURE CITED Armstrong, W. 1967. The r e l a t i o n s h i p between o x i d a t i o n - r edu c t i o n poten-t i a l s and oxygen -d i f f u s i on l e v e l s i n some water logged organ ic s o i l s . J . S o i l S c i . 18(1): 27-34. B a i l e y , L.D. and E.G. Beauchamp. 1971. N i t r a t e r educ t i on , and redox poten-t i a l s measured wi th permanently and tempora r i l y p laced p lat inum e l e c -t rodes i n sa tu ra ted s o i l s . Can. J . S o i l S c i . 51: 51-58. Bohn, H.L. 1971. Redox p o t e n t i a l s . S o i l S c i . 112(1): 39-45. Brown, L.A. 1933. Ox ida t i on reduc t i on p o t e n t i a l s i n s o i l s : I . P r i n c i p a l s and e l e c t r ome t r i c de te rm ina t i on . So i l S c i . 37(1) : 65-77. C o l l i n s , J . F . and S.W. Buo l . 1970. Pa t t e rns of i r on and manganese p r e c i p i t a t i o n under s p e c i f i e d Eh-pH c o n d i t i o n s . S o i l S c i . 110(3): 157-162. Freedman, R.W., B . I . Ferber and W.H. Duerr . 1978. Gas-sampl ing c a p a b i l i t y o f v a cu t a i n e r s . U.S. Dept. o f the I n t e r i o r , Bureau of Mines. Report I n v e s t i g a t i o n s 8281. G a r r e l s , R.M. and C.L . C h r i s t . 1965. S o l u t i o n s , m inera l s and e q u i l i b r i a . Harper and Row, New York. - 234 -Gotoh, S. and K. Yamashi ta. 1966. Ox i da t i on - r educ t i on po t en t i a l o f a paddy s o i l in s i t u wi th spec i a l re ference to the product ion of f e r rous i r o n , manganous manganese, and s u l f i d e . S o i l S c i . and P l a n t N u t r i t i o n 12: 230-238. J e f f e r y , J.W.O. 1961. Measuring the s t a t e of reduc t i on of a water logged s o i l . J . S o i l S c i . 12(2) : 317-325. Lance, J . C . and F.D. Wh i s l e r . 1972. N i t rogen ba lance in s o i l columns i n t e r m i t t e n t l y f looded wi th secondary sewage e f f l u e n t . J . Env i r on . Qua l i t y 1 (2 ) : 180-186. Lemon, E.R. and A .E . E r i c k s on . 1952. The measurement of oxygen d i f f u s i o n in the s o i l w i th a p lat inum m i c r o - e l e c t r ode . So i l S c i . Soc. Amer. P r o c . 16: 160-163. L i nd say , W.L. and M. Sad iq . 1978. M inera l t rans fo rmat ions i n s o i l s t ha t accompany changes i n redox. Dept. of Agronomy, Colorado S ta te Un i v . , F o r t C o l l i n s , Co lorado. L i neba rge r , R .S . , F.D. Wh i s l e r and J . C . Lance. 1975. A new technique f o r r a p i d and cont inuous measurement of redox p o t e n t i a l s . S o i l S c i . Soc. Amer. P roc . 39: 375-377. P a t r i c k , Wm. H. J r . and I . e . Mahapatra. 1968. Transformat ions and a v a i l a b i l i t y o f n i t rogen and phosphorous in water logged s o i l s . Advan. Agron. 20: 323-359. - 235 -Pearsal l , W.H. and C.H. Mortimer. 1939. Oxidation-reduction potentials 1n waterlogged so i l s , natural waters and muds. J . Ecol. 27: 483-501. Petersen, G.K. 1966. Redox measurements: their theory and techniques. ST 40. Radiometer. Copenhagen, Denmark. Volkov, I . I . , A.G. Rozanov and V.S. Sokolov. 1975. Redox processes in diagenesis in the northwest Pacif ic Ocean. Soil Sc i . 119(1): 28-35. Whisler, F .D . , J .C . Lance and R.S. Linebarger. 1974. Redox potentials in so i l columns intermittently flooded with sewage water. J . Environ. Quality 3(1): 68-74. Yamane, I. 1969. Reduction of nitrate and sulfate in submerged soi ls with special reference to redox potential and water-soluble sugar content of so i l s . So i l . Sc i . and Plant Nutrition 15(4): 139-148. - 236 -

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