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Distribution and characterization of organo-clay complexes in selected Lower Fraser Valley soils Parasher, Chander Dutt 1969

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THE DISTRIBUTION AND CHARACTERIZATION OF ORGANO-CLAY COMPLEXES IN SELECTED LOWER ERASER VALLEY SOILS fey C H A N D E R D U T T P A ' R A S H E R A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN A(TR1CULTUR_ IN THE DEPARTMENT OF S O I L SCIENCE We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September 12, 1969-In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y 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 r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t of S^>\£ $ c > g v c t . The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8 , C a n a d a D a t e , TABLE OE CONTENTS PAGE ACKNOWLEDGEMENT i ABSTRACT i i SECTION I. INTRODUCTION 1 II. LITERATURE REVIEW . . 5 III- METHODS AND MATERIALS 19 IV. RESULTS AND DISCUSSION 29 V- SUMMARY AND CONCLUSION . . . . . . 52 VI. BIBLIOGRAPHY . 55 ACKNOWLEDGEMENTS The author wishes to express h i s deep sense of apprecia-t i o n to the following persons, without whose timely help t h i s t h e s i s would not have been poss i b l e ; to Dr. L. E. Lowe f o r h i s f r i e n d l y help and guidance during the course of t h i s i n v e s t i g a t i o n , and Dr. 0. A. Howies, Chairman, Department of S o i l Science, to the members of the Research Committee, Dr. P. M. Townsley and p a r t i c u l a r l y Dr. L. M. Lavkulich who pro-vided valuable a i d i n connection with x-ray d i f f r a c t i o n analyses. to Mr. Herbert Luttmerding, Pedologist, B r i t i s h Colum-b i a Department of A g r i c u l t u r e f o r h i s help i n l o c a t i n g the sampling s i t e s , and l a s t l y , the f i n a n c i a l support by the National Research Council of Canada during the course of t h i s work i s acknowledged. i i ABSTRACT In the study of the d i s t r i b u t i o n of organo-clay complexes, t h i r t y - f o u r samples representing eight s o i l types were c o l l e c t e d from the Lower Eraser V a l l e y and the effectiveness of the three methods, v i z . simple dispersion, insonation and c h e l a t i n g r e s i n were examined. The use of a c h e l a t i n g r e s i n was found most ef -f e c t i v e f o r quantitative studies while- Insonation was preferred f o r q u a l i t a t i v e studies. For d e t a i l e d c h a r a c t e r i z a t i o n of the organo-clay complexes eight samples were chosen and u l t r a s o n i c a g i t a t i o n was used f o r i s o l a t i n g the organo-clay complexes. The organo-clay complexes v a r i e d widely i n c h a r a c t e r i s t i c s . The y i e l d of complexes by simple dispersion, u l t r a s o n i c v i b r a -t i o n and c h e l a t i n g r e s i n ranged from 0.15 to 10.42, 0.20 to 17.20 and 1.25 to 25.70 percent by weight, r e s p e c t i v e l y . The organo-clay complexes were analysed f o r t h e i r content of carbon, nitrogen, i r o n , s i l i c o n , aluminum along with carbo-hydrates, humic (HA) and f u l v i c (FA) a c i d s . The C/N r a t i o of the selected complexes v a r i e d between 5»5 and 17.0 and carbo-hydrate content accounted f o r 3*3 to 16.0 percent of the comp-lex carbon. The HA:FA r a t i o i n d i c a t e d that the major propor-t i o n of the organic component i n t h i s a s s o c i a t i o n was of f u l v i c nature, except i n the case of the Podzolic Bf horizon samples i n which about 2/3 of the extractable material was i n the humic f r a c t i o n . X-ray d i f f r a c t i o n , i n f r a r e d (IR) and d i f f e r e n t i a l thermal a n a l y s i s were also conducted. The mineralogy was not observed to d i f f e r to a great extent except i n the Ae horizon sample of the Orthic Podzol and the Btg of the Orthic Gleysol where mont-i i i m o r i l l o n i t e was p r e s e n t i n s i g n i f i c a n t amounts. In most of the samples examined i n t e r l a m e l l a r i n c l u s i o n o f the o r g a n i c matter was a l s o observed. The d i f f e r e n t i a l thermal a n a l y s i s e x h i b i t e d a band near 320°C p r o b a b l y due to the e l i m i n a t i o n of some form o f o r g a n i c f r a c t i o n . The IR s t u d i e s i n d i c a t e d the bonding of s i l i c o n t o o r g a n i c components through oxygen l i n k a g e s , however, t h e r e was no c o n c l u s i v e evidence of amide l i n k a g e f o r m a t i o n between organ-i c components and c l a y m i n e r a l s . 1. INTRODUCTION The r o l e of organic matter and clay occupies a place of considerable importance i n the realm of s o i l f e r t i l i t y , and the i n t e r a c t i o n of these materials to produce s o - c a l l e d organo-clay complexes i n s o i l s has an important influence on physico-chem-i c a l properties of s o i l s * In the study of s o i l properties i n r e l a t i o n to crop growth therefore, the process of organo-clay complex formation merits due a t t e n t i o n . In t h i s connection Jacks (46), stated, "the union of mineral and organic material to form the organo-clay complexes ( i s ) a synthesis as v i t a l to the continuance of l i f e as, and l e s s understood, than photosynthesis." Although t h i s appears perhaps to be an overstatement, nevertheless the pro-cess of organo-clay complex formation i s important i n s u s t a i n -i n g organic matter i n the solum which otherwise i s l i k e l y to be leached down quickly. Secondly, although a considerable amount of work has been done on a r t i f i c i a l l y prepared organo-clay complexes, very few studies have been reported on the nature of organo-clay complex-es as they occur i n s o i l s under natural conditions. In the past many workers have devoted a great deal of e f f o r t to working with pure minerals and organic compounds, which c e r t a i n l y has given some information about the i n t e r a c t i o n mechanisms of these com-ponents. However, the v a l i d i t y of these studies i n the f i e l d seems rather doubtful. Therefore, t h i s present i n v e s t i g a t i o n was undertaken under the heading, d i s t r i b u t i o n and c h a r a c t e r i z a t i o n of organo-clay complexes i n d i f f e r e n t s o i l types to investigate the nature of 2. the n a t u r a l l y o c c u r r i n g o r g a n o - c l a y complexes and to e l u c i d a t e the i n t e r - r e l a t i o n s h i p of the o r g a n i c and m i n e r a l f r a c t i o n s . In view o f the d e a r t h o f p r e v i o u s work i n t h i s f i e l d , and the e s s e n t i a l l y p r e l i m i n a r y n a t u r e of the study, the s p e c i f i c o b j e c t i v e s o f the i n v e s t i g a t i o n were to (1) compare the e f f e c t -i v e n e s s o f d i f f e r e n t methods o f i s o l a t i o n on d i f f e r e n t s o i l s , and ( 2 ) , c h a r a c t e r i z e these complexes w i t h r e s p e c t to o r g a n i c carbon a s s o c i a t e d w i t h these complexes and i t s e x t r a c t a b i l i t y w i t h d i f f e r e n t r e a g e n t s , and (3)» seek some i n f o r m a t i o n about t h i s a s s o c i a t i o n through the use of i n f r a r e d s p e c t r o s c o p y , X-r a y d i f f r a c t i o n and d i f f e r e n t i a l thermal a n a l y s e s . 3. •LITERATURE REVIEW The d i f f i c u l t i e s encountered i n the e x t r a c t i o n o f o r g a n i c m a t t e r from s o i l , serve t o remind one t h a t the s e p a r a t i o n o f s o i l c o l l o i d s i n t o o r g a n i c and i n o r g a n i c components i s e a s i e r i n t h e o r y than i n p r a c t i c e , due to the i n t i m a t e a s s o c i a t i o n o f o r g a n i c and i n o r g a n i c components. T h i s a s s o c i a t i o n i s o f t e n c a l l e d o r g a n o - c l a y complex f o r m a t i o n . T h e r e f o r e , when one a t -tempts e x t r a c t i o n o f o r g a n i c matter from the s o i l the phenom-enon of o r g a n o - c l a y complex f o r m a t i o n must he taken i n t o a c -count. A review o f p e r t i n e n t l i t e r a t u r e i s giv e n i n the f o l -l o w i n g pages. The e f f e c t i v e n e s s o f d i f f e r e n t e x t r a c t i o n methods and r e a g e n t s . A l t h o u g h the l a c k o f s a t i s f a c t o r y methods of s e p a r a t i n g the o r g a n i c component from the i n o r g a n i c m a t e r i a l of the s o i l has l o n g been r e c o g n i z e d , s u r p r i s i n g l y l i t t l e a t t e n t i o n has been g i v e n to t h i s problem. A l k a l i e x t r a c t i o n has been i n use s i n c e 1786, when Ach a r d ( 1 ) , f o r the f i r s t time employed i t to i s o l -a te humic a c i d . C o n s i d e r a t i o n o f the p o s s i b i l i t y t h a t c a u s t i c a l k a l i may s e r i o u s l y a f f e c t the p h y s i c o - c h e m i c a l p r o p e r t i e s o f s o i l o r g a n i c matter l e d Bremner and Less ( 1 2 ) , to seek m i l d e r methods o f e x t r a c t i o n . Keeping t h i s o b j e c t i v e i n mind they s u r -veyed the e x t r a c t i n g powers o f v a r i o u s n e u t r a l r e a g e n t s , espec-i a l l y the sodium s a l t s o f o r g a n i c and i n o r g a n i c a c i d s . A g r e a t v a r i e t y o f c h e m i c a l r e a g e n t s have been t e s t e d f o r the e x t r a c t i o n o f the o r g a n i c f r a c t i o n from s o i l s , (13,14,17, 83), and the advantages and dis a d v a n t a g e s o f these c r i t i c a l l y r e viewed and d i s c u s s e d . The rea g e n t s commonly employed are sodium h y d r o x i d e and two r e l a t i v e l y m i l d s a l t s , sodium p y r o -4. phosphate and sodium f l u o r i d e , hut optimum c o n c e n t r a t i o n and e x p e r i m e n t a l c o n d i t i o n s are seldom c l e a r l y d e f i n e d . However, r e c e n t l y these methods (95), have been employed w i t h r e a s o n a b l e s u c c e s s and p r o b a b l y without s i g n i f i c a n t p r o -d u c t i o n o f a r t e f a c t s , but the p o s s i b i l i t y o f b r e a k i n g c l a y -o r g a n i c a s s o c i a t i o n remains. In the p r e s e n t i n v e s t i g a t i o n t h r e e methods have been em-p l o y e d f o r i s o l a t i n g o r g a n o - c l a y complexes. R e l a t i v e l y l i t t l e work has been done i n t h i s d i r e c t i o n , hence, v e r y l i t t l e l i t e r -a t u r e i s a v a i l a b l e , and i n some i n s t a n c e s the work r e p o r t e d may not be t o t a l l y p e r t i n e n t t o the p r e s e n t work. The methods are b r i e f l y enumerated below: Simple d i s p e r s i o n and d e c a n t a t i o n : T h i s method (7)» has been a p p l i e d to a Bnt h o r i z o n o f a B l a c k S o l o n e t z s i l t y c l a y loam and found s a t i s f a c t o r y f o r i s o l -a t i n g o r g a n o - c l a y complexes i n good y i e l d . However, t h i s was attempted on o n l y one s o i l type and, t h e r e f o r e , l i t t l e can be s a i d about i t s u n i v e r s a l a p p l i c a b i l i t y to a l l s o i l s . T i n s l e y (83), a l s o a p p l i e d t h i s method but the i n t r o d u c t i o n o f an o r -ga n i c reagent i n h i s method may have produced a r t e f a c t s . C h e l a t i n g R e s i n s : I t i s g e n e r a l l y observed t h a t i f a s o i l i s t r e a t e d w i t h a c h e l a t i n g r e s i n p r i o r t o e x t r a c t i o n o f o r g a n i c matter, the amount of the l a t t e r e x t r a c t e d i s i n c r e a s e d s i g n i f i c a n t l y . Bremner and coworkers (14,16) r e p o r t e d t h a t the use of the s y n t h e t i c c a t i o n exchange r e s i n Dowex A - l , w i t h i m i n o d i a c e t i c a c i d groups, was v e r y e f f e c t i v e i n s o i l o r g a n i c matter e x t r a c -t i o n . They a l s o c l a i m e d t h a t t h i s reagent d i d not i n v o l v e the 5 . r i s k s o f a r t e f a c t i o n a s s o c i a t e d w i t h the c l a s s i c a l methods. Yuan ( 9 5 ) a l s o r e p o r t e d t h a t the amount o f o r g a n i c matter ex-t r a c t e d by the use o f Dowex A - l c h e l a t i n g r e s i n was i n some cases comparable to t h a t o b t a i n e d by a l k a l i e x t r a c t i o n . Bear ( 1 0 ) , observed t h a t the e x t r a c t i o n o f o r g a n i c matter by the use o f c h e l a t i n g r e s i n i s comparable i n q u a n t i t y t o 0.5N sodium hy-d r o x i d e , and an e x t r a c t d e v o i d o f contaminants i s o b t a i n e d . However, the ash con t e n t i s u s u a l l y h i g h ; an o b s e r v a t i o n t h a t suggests the p o t e n t i a l o f such r e s i n f o r d i s p e r s i n g o r g a n i c mat-e r i a l s w i t h i t s a s s o c i a t e d m i n e r a l c o l l o i d s . C a t i o n exchange r e s i n s have a l s o been employed f o r the removal o f c a t i o n s from i s o l a t e d humus f r a c t i o n s and i n the s e p a r a t i o n o f humic and f u l -v i c a c i d s , ( 6 0 ) . M a r t i n and Reeve ( 5 5 ) r e p o r t e d t h a t c h e l a t i n g agents (e.g., sodium pyrophosphate) were p a r t i c u l a r l y e f f e c t i v e i n e x t r a c t i o n o f o r g a n i c matter from a P o d z o l i c B h o r i z o n . Evans (31) r e p o r -t e d t h a t the ex t e n t o f o r g a n i c matter e x t r a c t i o n tended t o r i s e w i t h t t h e pH, and c h e l a t i n g r e a g e n t s e x t r a c t e d more than o t h e r s o f comparable pH v a l u e . Use o f u l t r a s o n i c s , : The use o f u l t r a s o n i c s i n the study o f o r g a n i c matter and humus complexes appears to have c o n s i d e r a b l e p o t e n t i a l , but the method has as y e t not been used e x t e n s i v e l y . I t was observed ( 3 4 ) , t h a t the amount o f o r g a n i c matter ex-t r a c t e d by treatment o f s o i l s w i t h 0.1M N a ^ O ? and 0.5N NaOH f o r t h r e e hours were i n c r e a s e d by 20 t o 48% p r o v i d e d the s o i l -r e a gent s u s p e n s i o n s were s u b j e c t e d t o i n s o n a t i o n . Edwards and Bremner ( 2 6 ) , c o n f i r m e d t h i s o b s e r v a t i o n but found t h a t the 6. amount o f o r g a n i c m a tter e x t r a c t e d by s h a k i n g s o i l s w i t h these r e a g e n t s f o r 24 hours were not markedly a f f e c t e d i f the suspen-s i o n s were s u b j e c t e d t o i n s o n a t i o n (18 to 2 0 kc) f o r one hour b e f o r e treatment w i t h a l k a l i o r sodium pyrophosphate. In 1 9 6 7 , the same a u t h o r s ( 2 7 ) , used i n s o n a t i o n f o r d i s p e r s i o n of s o i l p a r t i c l e s from s o i l s o f d i f f e r e n t t e x t u r e and o r g a n i c matter c o n t e n t , and they a l s o commented t h a t the probe-type v i b r a t o r was comparable to the s o n i c v i b r a t o r . S e v e r a l workers have c o n c l u d e d (26 , 2 7,34) t h a t i n s o n a t i o n p e r m i t s s e p a r a t i o n o f s o i l p a r t i c l e s w i thout the use o f o x i -d a n t s , a c i d s , o r p e p t i z i n g r e a g e n t s and w ithout d i s s o l u t i o n o f more than t r a c e s o f o r g a n i c o r i n o r g a n i c m a t e r i a l , and does not s i g n i f i c a n t l y a f f e c t the pH o r c o n d u c t i v i t y of s o i l s u s p ension, and s u s p e n s i o n s o b t a i n e d were r e p o r t e d l y q u i t e s t a b l e . However, Bourget ( 1 9 ) , u s i n g i n s o n a t i o n f o r d i f f e r e n t time p e r i o d s , r e -p o r t e d t h a t r e s u l t s were q u i t e v a r i a b l e w i t h the time o f shak-i n g and t h a t t h i s method d i d not give e f f e c t i v e d i s p e r s i o n un-der h i s l a b o r a t o r y c o n d i t i o n s . Other workers (40,60), have used u l t r a s o n i c d i s p e r s i o n f o r the s e p a r a t i o n o f p a r t i a l l y h u m i f i e d o r g a n i c m a t e r i a l s and c l a i m e d i n s o n a t i o n to be a r a p i d method f o r removing s o l u b l e o r g a n i c matter from sediments. Olmstead ( 6 6 ) s t u d i e d d i s p e r s i o n o f s o i l s by h i g h f r e -quency and h i g h i n t e n s i t y sound waves produced by a l a r g e p i e z o -e l e c t r i c q u a r t z c r y s t a l d r i v e n by a 1 5 0 0 W . vacuum-tube o s c i l -l a t o r , and r e p o r t e d r e a s o n a b l y e f f e c t i v e d i s p e r s i o n . B a r k o f f ( 9 ) r e p o r t e d t h a t the d i s p e r s i o n a c h i e v e d by a 1 5 or 60 min-u t e s p e r i o d of u l t r a s o n i c v i b r a t i o n o f s o i l s suspended i n sod-ium hexametaphosphate-sodium carbonate s o l u t i o n was more com-7. p l e t e than t h a t o b t a i n e d by s h a k i n g these suspensions f o r f i v e h o u r s . The use o f u l t r a s o n i c v i b r a t i o n f o r d i s p e r s i o n appears use-f u l i n not i n t r o d u c i n g any contaminant, b r i n g i n g about a f a i r l y s t a b l e s u s p e n s i o n and p r o b a b l y not b r e a k i n g c l a y - o r g a n i c a s s o -c i a t i o n s . Amount of carbon a s s o c i a t e d w i t h the complexes. I t i s not easy to determine p r e c i s e l y and a c c u r a t e l y the amount o f o r g a n i c matter i n v o l v e d i n complex f o r m a t i o n , due to the d o u b t f u l n a t u r e o f the complex i t s e l f , and the manner i n which carbon i s p r e s e n t i n the complex. A c c o r d i n g t o Greenland (39), to s e p a r a t e the " f r e e " and "combined" o r g a n i c m a t e r i a l some amount of work i n some form must be done, and the p r o p o r t i o n of m a t e r i a l found i n the com-p l e x , i . e . , the l e s s than 2 micron f r a c t i o n , w i l l depend on the amount o f t h i s work. Many workers i n t h i s f i e l d (4-0,46,47,50, 54,61), have t r i e d the s e p a r a t i o n of the f r e e o r g a n i c m a t e r i a l i n - a l i q u i d o f d e n s i t y i n t e r m e d i a t e between t h a t o f the f r e e m a t e r i a l and c l a y - o r g a n i c complex and r e p o r t e d i t to be s a t i s -f a c t o r y . G r e e n l a n d (39) has r e p o r t e d t h a t l i q u i d s of d e n s i t y between 1.8 to 2.0 \*/ere r e a s o n a b l e . S h o r t u l t r a s o n i c d i s p e r -s i o n ( 4 0 ) , i s p r o b a b l y the b e s t method o f r e l e a s i n g e n t a n g l e d m a t e r i a l , but the entanglement can a l s o be overcome by b o i l i n g an aqueous s u s p e n s i o n o f the s o i l and then washing and d r y i n g w i t h a l c o h o l t o p r e v e n t r e a g g r e g a t i o n ( 6 1 ) . The p e r c e n t o f carbon i n the complex expressed on the t o t a l s o i l carbon was found by Henin and Turc to be 66.5% ( 4 6 ) , by u s -i n g s e d i m e n t a t i o n i n a benzene-bromoform mixture o f s p e c i f i c 8. g r a v i t y 1.75 f o r Rendzina s o i l s . Khan ( 5 0 ) , working on Podzol and Chernozem s o i l s reported 89•6% and 85.2$ re s p e c t i v e l y by using sedimentation i n Toulet s o l u t i o n of s p e c i f i c gravity 1.8. Monnier and h i s associates (61), used ethanol-bromoform of s p e c i f i c gravity 2.0 f o r sedimentation and reported 77*5$ car-bon from s i l t under old pasture. Roulet et a l . ( 7 1 ) , reported 54.3% and 68.1$ organic carbon r e s p e c t i v e l y of the t o t a l s o i l carbon from Rendzina and Brown Earth s o i l s by using a " f l o t a -t i o n s i e v i n g " method. Greenland and Ford (40) used u l t r a s o n i c d i s persion and sedimentation i n bromoform-petroleum s p i r i t of s p e c i f i c gravity 2.0 and studied organo-mineral complexes i n a number of s o i l s and reported 7 1 . 5 , 68.4, 97.8, 76.4, and 5 1 . 6 percent of the t o t a l s o i l carbon from Red Brown Earth, Rend-zina, L a t e r i t i c Red Earthy Solo.dized Solonetz and Solonized Brown s o i l r e s p e c t i v e l y i n the complex. Several workers (40,46,50) have concluded that free organic material ( i . e . , not complexed) i s i n a much e a r l i e r stage of de-composition than the material complexed with cl a y . However, t h e i r methods of i s o l a t i n g complexes do not seem sound, and i t i s hard to t e l l whether they are producing new complexes by the use of organic l i q u i d s , or whether they are i s o l a t i n g them. Secondly, sometimes the d i s t i n c t i o n between organo-clay and or-gano-mineral complexes i s not c l e a r l y established. A great number of separation methods have been used i n the past without g i v i n g much attention to the a r t e f a c t s produced, Such methods ranged from simple dispersion i n water to d r a s t i c chemical treatments. However, even the mildest of these could cause some separation of organic material from the mineral com-9. ponent. In 1938, T y u l i n (85), proposed s h a k i n g the s o i l w i t h sodium c h l o r i d e , which p r o b a b l y r e l e a s e s C a + + bonded to o r g a n i c c o l l o i d s , and sub s e q u e n t l y t r e a t i n g w i t h d i l u t e a l k a l i which may r e l e a s e some i r o n and aluminum bonded m a t e r i a l and a l s o d i s s o l v e some p a r t o f the o r g a n i c f r a c t i o n . T h e r e f o r e , t h i s and a l l i e d methods do not g i v e s a t i s f a c t o r y i n f o r m a t i o n due to the use of Na + i o n s and a h i g h pH. Some workers ( 7 1 ) , used e l u t r i a t i o n and s i e v i n g f o r the s e p a r a t i o n o f f r e e o r g a n i c m a t e r i a l s , but t h i s t e c h n i q u e appeared t o g i v e s i g n i f i c a n t l y lower r e s u l t s (39). S e v e r a l o t h e r workers (3,4), and p a r t i c u l a r l y Trofimenko and h i s a s s o c i a t e (84), conducted experiments on G i e c a u c a s i a s o i l s . They r e p o r t e d s i m i l a r amounts o f o r g a n i c m a t e r i a l a s s o c i a t e d w i t h the c l a y f r a c t i o n and the f i n e s i l t f r a c t i o n i n / t o p 10 cm l a y e r . The c l a y f r a c t i o n c o n t a i n e d 33•5 to 55.2 p e r c e n t o f the t o t a l humus i n the top 10 cm and 50-77-4 p e r c e n t o f the t o t a l humus i n the 40-50 cm l a y e r . They a l s o r e p o r t e d t h a t the 0.1-0.25 mm f r a c t i o n c o n t a i n e d a semidecomposed mass, but i n the f i n e r f r a c t i o n s o r g a n i c carbon was a s s o c i a t e d w i t h the m i n e r a l s u r f a c e s o r mi c r o a g g r e g a t e s . They f u r t h e r mentioned t h a t the percentage o f humins i n the humus o f a p a r t i c u l a r f r a c t i o n was l e a s t i n the c l a y f r a c t i o n and i n c r e a s e d w i t h i n c r e a s i n g p a r -t i c l e s i z e . A s i m i l a r i n v e s t i g a t i o n was made by Arshad and Lowe ( 7 ) , who t r i e d t o est i m a t e the amount o f carbon i n d i f f e r e n t c l a y s i z e p a r t i c l e s and found more o r g a n i c carbon a s s o c i a t e d w i t h the c o a r s e r c l a y f r a c t i o n . I t i s e v i d e n t from the l i t e r a t u r e reviewed t h a t i t does not appear a p p r o p r i a t e t o make any c o n c l u s i v e statement about the magnitude o f carbon p r e s e n t i n the o r g a n o - c l a y complexes, 10. as i t v a r i e s and s h o u l d v a r y from source to source, depending a t l e a s t on c l i m a t e , v e g e t a t i o n and mineralogy, and not v e r y much i s known about the v a r i a b i l i t y o f t h i s parameter on s o i l s from d i f f e r e n t s o u r c e s . C h a r a c t e r i z a t i o n o f Organo-clay Complexes. I t does n o t appear f r u i t f u l t o review the numerous p u b l i c -a t i o n s i n which v a r i o u s t e c h n i q u e s are a p p l i e d to s o i l s . A t t e n -t i o n w i l l be drawn o n l y to those s t u d i e s d i r e c t l y r e l e v a n t to the study o f o r g a n o - c l a y complexes. Organo-clay complex r e -s e a r c h has made measurable p r o g r e s s d u r i n g r e c e n t y e a r s . How-ever, t h i s f i e l d i s s t i l l not w e l l understood, perhaps due to the l a c k o f knowledge of the s p e c i a l p r o p e r t i e s of o r g a n o - c l a y complexes. These complexes appear to have v e r y p e c u l i a r compo-s i t i o n and s t r u c t u r e . T y u l i n (85) conducted a study on organo-mineral g e l s i n r e l a t i o n to s o i l f e r t i l i t y . He r e p o r t e d t h a t humus i s q u i t e l o o s e l y h e l d a t the s u r f a c e s o f these g e l s and he c l a i m e d i t to be v e r y important i n s o i l f e r t i l i t y . . He a l s o r e p o r t e d t h a t the q u a n t i t y and the c o m p o s i t i o n o f the l o o s e l y h e l d humates i n s o i l c o l l o i d s may s e r v e a v a l u a b l e c r i t e r i o n o f s o i l f e r t i l i t y , o r the e x t e n t to which the s o i l can be c u l t i v a t e d . Ensminger (30) s t u d i e d the f a c t o r s a f f e c t i n g the i n t e r a c t i o n between o r g a n i c matter and the m i n e r a l f r a c t i o n s . He r e p o r t e d t h a t the combin-i n g c a p a c i t y o f m o n t m o r i l l o n i t e w i t h g e l a t i n , albumen, straw, a l f a l f a l e a f meal, and l i g n i n , i n c r e a s e d w i t h a c i d i t y r e a c h i n g a maximum a t pH 0.5. He a l s o c l a i m e d an i n c r e a s e i n s o r p t i o n of straw and a l f a l f a l e a f meal by m o n t m o r i l l o n i t e w i t h composting. T h i s phenomenon was more pronounced i n a l f a l f a , p r o b a b l y due to 11. h i g h n i t r o g e n c o n t e n t . Khan ( 5 0 ) s e p a r a t e d f r e e o r g a n i c m a t e r i a l by immersion o f the s o i l samples i n T o u l e t s o l u t i o n s by c e n t r i f u g i n g and decan-t a t i o n . He used s o l u t i o n s w i t h s p e c i f i c g r a v i t i e s of l e s s than 2 . 4 5 and l e s s than 1.80. I t i s u n l i k e l y t h a t the complete sep-a r a t i o n would have been o b t a i n e d by t h i s simple immersion t e c h -n i q u e . Brydon and h i s a s s o c i a t e ( 1 8), s t u d i e d the clay-humus complexes o f a Chemozemic and P o d z o l i c s o i l by u s i n g T y u l i n ' s method o f f r a c t i o n a t i o n . They r e p o r t e d t h a t the s m a l l e r s i z e and l e s s c r y s t a l l i n e c l a y s were c o n c e n t r a t e d i n the humate f r a c -t i o n s and c l a i m e d amino groups to be r e s p o n s i b l e f o r the bond-i n g o f o r g a n i c and i n o r g a n i c m i n e r a l components. A l e k s a n d r o v a and Nad ( 4 ) from R u s s i a , r e p o r t e d a study on the n a t u r e o f o r -gano-mineral c o l l o i d s and c o n s i d e r e d organo-mineral c o l l o i d s as complexes of v a r i a b l e compounds o f h i g h l y d i s p e r s e d m i n e r a l s . The phenomenon of combination o f the m i n e r a l w i t h the o r g a n i c component was r e p o r t e d through the alumino- and iron-humic d e r -i v a t i v e s i n the s t a t e o f a g g r e g a t i o n . S i m i l a r was the o b s e r v a -t i o n o f Chaudhry and Stevenson ( 2 1 ) , who r e p o r t e d t h a t c a l c i u m , aluminum, and i r o n may be the medium o f combination o f m i n e r a l and o r g a n i c f r a c t i o n s . T h e i r c o n c l u s i o n was l i n k e d t o the f a c t t h a t i n the absence o f these c a t i o n s the percentage o f o r g a n i c matter e x t r a c t e d by a l k a l i n e s o l v e n t s i n c r e a s e d c o n s i d e r a b l y . However, another group o f workers (28), put forward a s i m i l a r c r i t e r i o n f o r the f o r m a t i o n o f aggregates and subsequently s o i l s t r u c t u r e development. They r e p o r t e d t h a t microaggregates con-s i s t m a i n l y of c l a y and h u m i f i e d o r g a n i c m a t e r i a l l i n k e d through p o l y v a l e n t m e t a l s . T h e i r concept o f microaggregate ( < 2 5 Q £ ) f o r -12. mation through c a t i o n b r i d g e l i n k a g e s appears s i m i l a r t o o t h e r worker's (4,21) h y p o t h e s i s f o r o r g a n o - c l a y complex f o r m a t i o n . However, t h i s p r o c e s s o c c u p i e s a s i g n i f i c a n t p a r t i n the com-p l e x f o r m a t i o n , but s h o u l d not be o v e r - e s t i m a t e d . The p r o c e s s o f o r g a n o - c l a y complex f o r m a t i o n (96), has a l -so been a t t r i b u t e d to the a d s o r p t i o n o f microorganisms by c l a y m i n e r a l s . However, A l e k s a n d r o v a e t a l . ( 5 ) , d e s c r i b e d the p r o -c e s s o f o r g a n o - m i n e r a l complex f o r m a t i o n as j u s t a s u r f a c e phen-omenon. They r e p o r t e d t h a t humus substances form a t h i n f i l m on the s u r f a c e s o f a l l m i n e r a l c o l l o i d f r a c t i o n s . B e s i d e s , i n c o a r s e f r a c t i o n s humus substances a l s o form a separate coagulum and e n t e r i n t o the c o m p o s i t i o n o f c o n c r e t i o n s . Law e t a l . (53) , s t u d i e d the phenomenon o f complex forma-t i o n w i t h m o n t m o r i l l o n i t e and t h r e e d i f f e r e n t s u r f a c t a n t s ( a n -i o n i c , c a t i o n i c and n o n a n i o n i c ) and r e p o r t e d t h a t a n i o n i c s were no t adsorbed s t r o n g l y by s o i l s . In the dry s t a t e they were weakly h e l d and q u i c k l y r e l e a s e d to the l i q u i d phase upon r e -w e t t i n g . I n c o n t r a s t c a t i o n i c s were s t r o n g l y adsorbed by the s o i l and not r e a d i l y r e l e a s e d upon r e w e t t i n g . The n o n - i o n i c s were r e p o r t e d adsorbed by H-bonding to c l a y and o t h e r oxygen r i c h m i n e r a l s u r f a c e s . A study on m o n t m o r i l l o n i t e and a l l o p h a n e (86), r e v e a l e d t h a t s o i l s c o n t a i n i n g m o n t m o r i l l o n i t e showed s a t -u r a t i o n w i t h humic substances a t 0.65$ C, whereas s o i l s c o n t a i n -i n g a l l o p h a n e showed g r e a t e r a d s o r p t i o n but d i d not a t t a i n an a d s o r p t i o n maximum. H a r g i t a i (45) , s t u d i e d the e f f e c t o f changes i n organo-m i n e r a l complexes on the q u a l i t y of s o i l o r g a n i c matter and o r -g a n i c n i t r o g e n . However, t h i s study does not appear sound due 1 3 . to the lack of well defined objectives as he limed the s o i l and r a i s e d the pH from 5 - 5 to 6.0. He found that the e a s i l y a v a i l -able nitrogen increased and the aluminum content decreased sharply. I t appears hard to believe that these changes are tak-i n g place due e n t i r e l y to organo-mineral complexes. Scharpen-s e e l (72), conducted a t r a c e r study on organo-clay complexes and concluded that NH4+, A l + + + , C a + + , and F e + + + , ( i n increasing order), but not H +, Na +, K +, or Mg + +, acted as bridge cations i n montmorillonite-humic a c i d complexes. However, the bridging mechanism did not operate with kaolinite-humic a c i d or k a o l i n -i t e - f u l v i c a c i d complexes. Pe was found more e f f e c t i v e than F e + + and the complexes formed through cation bridges were les s stable than the complexes formed by hydrothermal synthesis. X-Ray d i f f r a c t i o n studies:-Probably the importance of clay-organic i n t e r a c t i o n s i n the ceramic industry to produce materials with completely modi-f i e d properties has l e d to the use of x-ray d i f f r a c t i o n methods. Int e r l a m e l l a r adsorption of organic compounds by montmor-i l l o n i t e could be observed by x-ray d i f f r a c t i o n methods quite e a s i l y ( 1 1,20 , 3 8,42,54 , 5 7 , 9 1,92). However, x-ray d i f f r a c t i o n a n a l y s i s does not y i e l d d i r e c t l y any information on the mechan-ism of t h i s adsorption. Several other workers ( 3 6 , 4 3 ) have em-ployed x-ray d i f f r a c t i o n f o r the ch a r a c t e r i z a t i o n of organo-clay complexes, and p a r t i c u l a r l y the former ( 3 6 ) , who prepared the complexes of clay minerals of the montmorillonite group with dimethylsulpho-oxide which had spacings varying from 18.21 to o i 9 . l l A and corresponded to 2 layers of the organic compound. Inte r l a m e l l a r adsorption (74) of f u l v i c a c i d by Na-montmorill-14. o n i t e was a l s o observed. However, Arshad and Lowe ( 7 ) , w h i l e s t u d y i n g n a t u r a l l y o c c u r r i n g o r g a n o - c l a y complexes o b t a i n e d from the Bnt h o r i z o n o f a S o l o n e t z s o i l , d i d not observe any evidenc e o f i n t e r l a m e l l a r a d s o r p t i o n o f o r g a n i c matter. Hov/ever, most o f these s t u d i e s were concerned w i t h organo-c l a y complexes i n v o l v i n g m a i n l y m o n t m o r i l l o n i t e m o n o i o n i c a l l y s a t u r a t e d and a s p e c i f i c o r g a n i c compound. These s t u d i e s on pure systems have g i v e n q u i t e v a l u a b l e i n f o r m a t i o n on bonding mechanisms but e x t r a p o l a t i o n i n r e l a t i o n to n a t u r a l l y o c c u r r i n g o r g a n o - c l a y complexes does not seem j u s t i f i e d . I n f r a r e d S p e c t r o s c o p y : -A l t h o u g h i n f r a r e d a n a l y s i s i s an e s t a b l i s h e d t o o l i n the study o f pure c l a y m i n e r a l s and pure o r g a n i c compounds, r e l a -t i v e l y l i t t l e work has been c a r r i e d out on org a n o - c l a y complex-es. When some s p e c i f i c groups o f an o r g a n i c molecule i n t e r a c t w i t h a c l a y m i n e r a l s u r f a c e on which the molecule i s adsorbed, the v i b r a t i o n s o f the atoms composing those groups w i l l be mod-i f i e d and t h i s w i l l r e s u l t i n a change i n wavelength a t which i n f r a r e d r a d i a t i o n i s absorbed. T h e r e f o r e , IR a n a l y s i s s h o u l d be u s e f u l i n the study o f a d s o r p t i o n mechanisms. The review papers o f a few workers ( 2 9 , 7 3 ) , are worth mentioning. A group o f workers ( 3 5 , 5 1 , 5 2 ) observed s h i f t s i n the c a r -b o n y l group s t r e t c h i n g f r e q u e n c y of adsorbed compounds and an i n c r e a s e i n i n t e n s i t y o f the bonded 0-H band a t ^ 4 due to the f o r m a t i o n o f hydrogen bonds w i t h Si-OH groups a t the edges o f the m o n t m o r i l l o n i t e l a t t i c e . However, Tensmeyer and h i s a s s o c -i a t e s ( 8 2), a t t r i b u t e d such s h i f t s t o i n t e r l a m e l l a r complexes 15-o f m o n t m o r i l l o n i t e w i t h ketones, and r e p o r t e d these e f f e c t s due t o the enhanced i n t e r a c t i o n s between the adsorbed m o l e c u l e s . S i m i l a r were the f i n d i n g s of Tahoun e t a l . ( 8 0 ) , who e s t a b l i s h e d t h a t t h i s e f f e c t was due to the a s s o c i a t i o n of the c a r b o n y l group w i t h the exchangeable c a t i o n s . Thus t h e r e i s no c o n f i r m -a t o r y evidence f o r hydrogen bonding between s u r f a c e and carbon-y l groups. I t i s w e l l understood, however, t h a t not o n l y m o n t m o r i l l -o n i t e but a l s o o t h e r c l a y m i n e r a l s p a r t i c i p a t e i n i n t e r a c t i o n w i t h o r g a n i c compounds. Weiss and h i s co-workers ( 9 0 , 9 1 , 9 3 , 9 4 ) have shown t h a t m o n t m o r i l l o n i t e , v e r m i c u l i t e , i l l i t e , and micas themselves r e a c t w i t h l o n g c h a i n a l k y l ammonium compounds, to form i n t e r l a m e l l a r complexes. However, the p r o c e s s was obser-ved to be slower i n o t h e r s i n comparison to m o n t m o r i l l o n i t e . T h i s d i f f e r e n c e seems to be due to the d i f f e r e n c e i n the s u r -f a c e charge d e n s i t y . T h i s concept i s a l s o supported by o t h e r workers (42 , 7 0 ) who observed v e r y s m a l l d i f f e r e n c e s i n the r e -a c t i o n s o f v e r m i c u l i t e and m o n t m o r i l l o n i t e w i t h o r g a n i c com-pounds. However, the s t r e n g t h of a d s o r p t i o n may be g r e a t e r on more d e n s e l y charged s u r f a c e s and the amount o f a d s o r p t i o n s h o u l d be c o n s i d e r a b l y lower due to lower s u r f a c e a r e a . The r o l e o f k a o l i n i t e - , s e s q u i o x i d e s j . and a l l o p h a n e i n the f o r m a t i o n of organo-mineral complexes s h o u l d be q u i t e s i g n i f i -c ant due to t h e i r s p e c i a l s t r u c t u r e , and •••••r .^c:v s u r f a c e a r e a . As k a o l i n i t e has one b a s a l f a c e of the c r y s t a l made o f s i l i c a t e sheet and the o t h e r o f g i b b s i t e sheet (89 , 9 1 ) and u n l i k e the s i l i c a t e sheet, the g i b b s i t e s u r f a c e may not c a r r y a charge. The edges, o f the k a o l i n i t e l a t t i c e become p o s i t i v e l y charged 16. ( 7 0 , 7 7 ) , a t low pH and t h i s charge may p e r s i s t to r e l a t i v e l y h i g h pH v a l u e s . The p o s i t i v e charge a t the edges enable i t to form p e r i p h e r a l complexes w i t h a n i o n i c compounds ( 4 4 , 5 8 , 5 9 , 6 2 ) . S e v e r a l o t h e r workers ( 2 , 6 2 ) , have shown t h a t the a d s o r p t i o n of a n i o n i c polymers i s g r e a t e r i n the presence o f c a t i o n s which p r o b a b l y d e c r e a s e s the z e t a p o t e n t i a l o f the polymer and the c l a y . G i l e s e t a l . ( 3 7 ) , conducted many i n v e s t i g a t i o n s on the a d s o r p t i o n o f o r g a n i c compounds from aqueous s o l u t i o n by s i l i c a and alumina. However, the s u r f a c e p r o p e r t i e s and s u r f a c e a r e a o f these m a t e r i a l s v a r y c o n s i d e r a b l y , depending upon the o r i -g i n , which may cause v e r y s i g n i f i c a n t d i f f e r e n c e s i n t h e i r ad-s o r p t i o n b e h a v i o r . A number o f workers ( 2 5 , 3 3 , 4 9 , 6 7 , 7 9 , 8 1 ) , have used IE. spec-t r o s c o p y f o r the c h a r a c t e r i z a t i o n o f o r g a n o - c l a y complexes and r e p o r t e d hydrogen bond f o r m a t i o n between OH groups o f m i n e r a l and the f u n c t i o n a l group o f the polymer. D i f f e r e n t i a l Thermal A n a l y s i s : -There has been a c o n s i d e r a b l e amount o f work done on s o i l m i n e r a l s i n r e l a t i o n t o d e h y d r a t i o n and the changes t a k i n g p l a c e on h e a t i n g . However, t h e r e has not been much work done on o r g a n o - c l a y complexes i n c o n j u n c t i o n w i t h DTA. S p i e l e t a l . ( 7 8 ) , a p p l i e d d i f f e r e n t i a l thermal a n a l y s i s to p a r t i c l e s i z e f r a c t i o n s o f the component m i n e r a l s , and Arnes ( 8 ) i n v e s t i g a t e d the e f f e c t on d i f f e r e n t i a l thermal c u r v e s o f the shape and s i z e of the sample h o l e and the p o s i t i o n o f the t h e r m a l - c o u p l e bead i n the h o l e . S e v e r a l o t h e r workers ( 6 5 , 7 8 ) , observed t h a t the slower the h e a t i n g r a t e , the broader the peak and the lower the temperature o f the peak. A l l w a y ( 6 ) , s t u d i e d 17-p i p e r i d i n e - m o n t m o r i l l o n i t e i n t e r a c t i o n s and observed t h a t the d e t a i l e d f e a t u r e s o f the exothermic r e a c t i o n s depended on the c o m p o s i t i o n o f the m i n e r a l m o n t m o r i l l o n i t e . He found t h a t the exothermic r e a c t i o n was always m u l t i p l e and a peak a t 700°C sug-g e s t e d a h i g h M g - m o n t m o r i l l o n i t e , and a t 4-50° and 500°Cy sugges-t e d an i r o n - r i c h m o n t m o r i l l o n i t e . However, a peak a t about 600°C suggested a member o f the m o n t m o r i l l o n i t e group c o n t a i n -i n g some aluminum i n t e t r a h e d r a l c o o r d i n a t i o n . The work o f Sch-n i t z e r and Hoffman on humic components (75)> though not q u i t e p e r t i n e n t to the p r e s e n t i n v e s t i g a t i o n , appears worth mention-i n g . They r e p o r t e d s m a l l c u r v e s near 100°C due to the e l i m i n a -t i o n o f H 20, 200 to 380°C due to the e l i m i n a t i o n o f C00H+0H. They a l s o r e p o r t e d (76) t h a t p h e n o l i c OH groups were more s t a b l e t h an COOH but b o t h were e l i m i n a t e d between 250 and 400°C. E x t r a c t i o n o f o r g a n i c matter from the complexes: The e x t r a c t i o n o f o r g a n i c carbon from organo-mineral com-p l e x e s has not been s t u d i e d i n d e t a i l and as such v e r y l i t t l e i n f o r m a t i o n i s a v a i l a b l e on e x t r a c t i o n , o r on e x t r a c t i n g r e a -g e n t s . However, the work o f Arshad and Lowe ( 7 ) , i s worth men-t i o n i n g i n t h i s c o n n e c t i o n . They c a r r i e d out s u c c e s s i v e e x t r a c -t i o n s o f o r g a n i c matter from o n l y one sample and found d i f f e r e n -ces i n the n a t u r e o f o r g a n i c components from d i f f e r e n t c l a y s i z e f r a c t i o n s . However, no comparable d a t a i s a v a i l a b l e . O rganic matter and p o l y v a l e n t c a t i o n s : Some of the o x i d e s o f metals have been r e p o r t e d t o complex o r g a n i c m atter o r otherwise h e l p i n complexing o r g a n i c matter. Sodium pyrophosphate i s c l a i m e d to e x t r a c t t h i s complexed organ-i c m atter. 18. Some workers (14,64), have r e p o r t e d t h a t pyrophosphate p r o -b a b l y s o l u b i l i z e s o rgano-mineral g e l s by c h e l a t i n g entrapped met-a l s and r e l e a s i n g f r e e complexed o r g a n i c carbon. N i g h t i n g a l e e t a l . (64), a l s o r e p o r t e d complexes o f c a l c i u m and o r g a n i c mat-t e r from s o d i c s o i l s which have not been l e a c h e d and c o n t a i n c o n s i d e r a b l e amounts o f d i s p e r s e d o r g a n i c m a t e r i a l . S e v e r a l o t h e r workers ( 2 2 , 2 3 ) s t u d i e d the i n t e r a c t i o n o f i r o n h y d r o x i d e s and Wyoming B e n t o n i t e and r e p o r t e d t h a t the complexes o f i r o n h y d r o x i d e s and c l a y were not s t a b l e . These workers d i d not r e -p o r t t h a t o r g a n o - c l a y complexes are formed through c a t i o n b r i d g e mechanism. 1 9 . METHODS AND MATERIALS In any s c i e n t i f i c i n v e s t i g a t i o n f i n d i n g a r e p r e s e n t a t i v e sample i s a v e r y important p a r t o f the whole e x p e r i m e n t a t i o n . The main o b j e c t i v e o f s e l e c t i n g samples f o r the p r e s e n t i n v e s -t i g a t i o n was to i n c l u d e a v a r i e t y o f samples i n r e l a t i o n t o s o i l m i n e r a l o g y and o r g a n i c matter c o n t e n t . T h e r e f o r e , f o r t h i s purpose e i g h t s o i l g r e a t groups were chosen w i t h the h e l p o f the s o i l s urvey p e r s o n n e l working c u r r e n t l y i n t h a t a r e a . In a l l , t h i r t y - f o u r h o r i z o n samples were brought i n and d r i e d a t room temperature. The samples were ground to pass t h r o u g h a 2 mm s i e v e and s t o r e d i n c a r d b o a r d boxes. The c l a s s -i f i c a t i o n o f the s o i l s i n v e s t i g a t e d a l o n g w i t h v e g e t a t i o n and t o p o g r a p h i c a l f e a t u r e s o f the sampling s i t e s , are g i v e n i n T a b l e I . These t h i r t y - f o u r samples were used f o r s t u d y i n g the d i s t r i b u t i o n o f o r g a n o - c l a y complexes. However, f o r d e t a i l e d c h a r a c t e r i z a t i o n of these complexes, o n l y e i g h t samples were s e l e c t e d based on the v a r i a b i l i t y i n c o n j u n c t i o n to d i s t r i b u -t i o n and carbon c o n t e n t . These e i g h t s e l e c t e d complexes were s u b j e c t e d to i n f r a r e d s p e c t r o s c o p y , x - r a y d i f f r a c t i o n , d i f f e r e n t i a l thermal a n a l y s i s and the e x t r a c t a b i l i t y of carbon w i t h d i f f e r e n t r e a g e n t s a l o n g w i t h t h e i r i r o n , aluminum and s i l i c o n c o n t e n t . The methods ad-opted f o r a n a l y s e s are enumerated below. P a r t i c l e s i z e a n a l y s i s : The c l a y c o n t e n t was e s t i m a t e d by a hydrometer method, as recommended by the committee on p h y s i c a l a n a l y s i s ( 2 4 ) . S o i l R e a c t i o n : The pH o f the s o i l water suspension ( R a t i o 1:2 . 5 ) was meas-20. TABLE I S o i l Subgroups Humic E l u v -i a t e d G l e y -s o l O r t h i c Con-c r e t i o n a r y Brown ( O r t h i c M i n i Humo-ferric P o d z o l ) O r t h i c Rego-s o l ( O r t h i c E u t r i c B r u n i s o l ) O r t h i c P o d z o l ( O r t h i c P e r r o -Humic P o d z o l ) Humic P o d z o l ( O r t h i c F e r r o -Humic P o d z o l ) A c i d Brown Wooded ( M i n i Humo-f e r r i c P o d z o l Humic G l e y s o l ( O r t h i c Humic G l e y s o l ) S e r i e s L a n g l e y Monroe Blaney Whatcom Hazelwood Topography L e v e l t o de-p r e s s i o n a l N i c h o l s o n L e v e l to un-d u l a t i n g U n d u l a t i n g C a r d i n a l R o l l i n g U n d u l a t i n g L e v e l t o de-p r e s s i o n a l Major V e g e t a t i o n Planteneum, Horse-t a i l , Sedges and B u t t e r c u p s . A l d e r , Maple and Braken f e r n . B u t t e r c u p s , Thorny Sunflower, and o t h e r graminaceous p l a n t s . Hemlock, Cedar and Douglas F i r . Hemlock, Maple and Cedar. Maple and A l d e r . P a s t u r e g r a s s e s o n l y . O r t h i c G l e y s o l H a t z i c L e v e l M a i n l y g r a s s e s . N.B. The names i n parentheses are r e v i s e d nomenclatures a c c o r d -i n g t o the 1968 r e p o r t o f the N a t i o n a l S o i l Survey Committee of Canada. ( T a b l e I to V ) . 2 1 . u r e d w i t h a Beckman Zeromatic pH meter. Orga n i c Carbon: Carbon o f the s o i l and complexes was determined w i t h a Leco i n d u c t i o n f u r n a c e and carbon a n a l y z e r . However, carbon o b t a i n e d w i t h d i f f e r e n t e x t r a c t i n g agents was e s t i m a t e d by the Walkley and B l a c k wet combustion method (68). N i t r o g e n : T o t a l n i t r o g e n c o n t e n t o f s o i l s and complexes was o b t a i n e d by a m i c r o - k j e l d a l method (68). Methods o f i s o l a t i n g o r g a n o - c l a y complexes: Simple d i s p e r s i o n : D i s p e r s i o n and d e c a n t a t i o n was used w i t h a view to a v o i d -i n g c h e m i c a l treatments a t any stage. A 1 0 gm sample was t r a n s -f e r r e d t o a two l i t r e g l a s s beaker and washed f r e e o f s o l u b l e s a l t s and o r g a n i c matter by d i s p e r s i o n i n d i s t i l l e d water, w i t h slow manual s t i r r i n g and d e c a n t a t i o n of the supernatant s o l u -t i o n . In many cases 3 - 4 washings were found optimum f o r t h i s purpose and the c l a y s i z e f r a c t i o n s were s e p a r a t e d by sedimen-t a t i o n t e c h n i q u e s ( 7 ) -The s u s p e n s i o n s thus o b t a i n e d were c o l l e c t e d i n 6 l i t r e b a t t e r y j a r s . The p r o c e s s was c o n t i n u e d t i l l t h e r e was no more su s p e n s i o n which u s u a l l y took about a week, depending upon the n a t u r e o f the sample. The suspension was s u b j e c t e d t o h i g h speed c e n t r i f u g a t i o n and the supernatant s o l u t i o n d i s c a r d e d . The c l a y s i z e f r a c t i o n s were t r a n s f e r r e d t o p l a s t i c c o n t a i n e r s f o r f r e e z e d r y i n g . The f r e e z e d r i e d samples were s t o r e d i n g l a s s c o n t a i n e r s f o r f u r t h e r study. 22. U l t r a s o n i c d i s p e r s i o n : U l t r a s o n i c d i s p e r s i o n has been r e p o r t e d a u s e f u l method (26,60), f o r e x t r a c t i n g o r g a n i c matter. However, i t i s not c o m p l e t e l y understood whether i t breaks the o r g a n o - c l a y complex-es o r j u s t the a g g regates. The method used i s d e s c r i b e d b r i e f -l y below. D i f f e r e n t models of u l t r a s o n i c equipment are a v a i l a b l e i n the market. However, i n the p r e s e n t study D i s O n t e g r a t o r U l t r a -s o n i c c l e a n e r s u p p l i e d by U l t r a s o n i c I n d u s t r i e s I n c . , N. Y., w i t h system No. F o r t y and Generator Model No. G.-40 CI-P w i t h power output 80 w atts. The tank had a h a l f g a l l o n c a p a c i t y . A 5 gm s o i l sample was t r a n s f e r r e d to a 100 ml c e n t r i f u g e tube a l o n g w i t h 50 ml d i s t i l l e d water. The suspension i n the tube was p l a c e d i n the u l t r a s o n i c b a t h i n such a way t h a t the sample i n the tube was c o m p l e t e l y below the l e v e l o f water i n the tank. The sample was i n s o n a t e d f o r 15 minutes. The samples were a l l o w e d t o stand f o r a s h o r t w h i l e , which appeared t o g i v e b e t t e r r e s u l t s , and then c e n t r i f u g e d u s i n g an I n t e r n a t i o n a l No. 2 c e n t r i f u g e to s e p a r a t e c l a y s i z e p a r t i c l e s . The p r o c e s s was r e p e a t e d as many times as n e c e s s a r y . The sus-p e n s i o n s thus o b t a i n e d were c o l l e c t e d i n two l i t r e g l a s s beak-e r s . The volume was reduced by c e n t r i f u g i n g and d i s c a r d i n g the c l e a r s u p e r n a t a n t s o l u t i o n . These s m a l l volumes were t r a n s -f e r r e d i n t o p l a s t i c c o n t a i n e r s and f r e e z e d r i e d . The f r e e z e d r i e d samples were used f o r f u r t h e r i n v e s t i g a t i o n s . C h e l a t i n g r e s i n ; C h e l a t i n g r e s i n s have been used under d i f f e r e n t assump-t i o n s f o r d i f f e r e n t purposes, but here the use of c h e l a t i n g 2 3 . agent was made to i s o l a t e the complexes f o r comparison w i t h o t h e r methods. The method i s d e s c r i b e d b r i e f l y below. A 5 gm s o i l sample was t r a n s f e r r e d to a 1 2 5 ml narrow neck po l y t h e n e b o t t l e a l o n g w i t h 0.88 gm c h e l a t i n g r e s i n , Chelex 100, 200-400 mesh Na form ( 0 . 5 gm on oven d r y b a s i s ) . To the sample b o t t l e 2 5 ml d i s t i l l e d water was added and samples were shaken i n an end-to-end shaker f o r 15 hours a f t e r s t o p p e r i n g the b o t t l e s . The samples were t r a n s f e r r e d t o 100 ml c e n t r i f u g e tubes and f r e e s o l u b l e o r g a n i c matter and s o l u b l e s a l t s were removed by h i g h speed c e n t r i f u g i n g . The p r o c e s s was c o n t i n u e d as l o n g as n e c e s s a r y . The c l a y s i z e p a r t i c l e s were s e p a r a t e d by cen-t r i f u g i n g the sample a t 7 5 0 rpm f o r 3 - 3 minutes u s i n g an I n t e r -n a t i o n a l No. 2 c e n t r i f u g e w i t h head No. 240. The p r o c e s s was c o n t i n u e d t i l l no more susp e n s i o n was o b t a i n e d . The d i f f e r e n t f r a c t i o n s o f sus p e n s i o n were c o l l e c t e d i n p l a s t i c c o n t a i n e r s and f r e e z e d r i e d f o r f u r t h e r use. X-ray d i f f r a c t i o n s t u d i e s : X-ray d i f f r a c t i o n a n a l y s e s were conducted as f o l l o w s : A 15-20 p e r c e n t s u s p e n s i o n o f o r g a n o - c l a y complexes was p r e -p a r e d i n d i s t i l l e d water and mounted on 27x46 mm micro s l i d e s . The s l i d e s were a l l o w e d t o d r y a t room temperature and a P h i l -i p s X-ray d i f f r a c t i o n u n i t employing N i - f i l t e r e d GuKtx: r a d i a t i o n was used f o r i n v e s t i g a t i o n s . However, due to poor r e s o l u t i o n i n some o f the c a s e s , the s l i d e s were heated t o 5 0 0°C f o r 5 hours to see i f the poor r e s o l u t i o n was e n t i r e l y due to o r g a n i c matter a l o n e . Secondly, the complexes were g l y c o l a t e d and x-ray p a t t e r n s were o b t a i n e d . 24. A f t e r h a v i n g o b t a i n e d some i n f o r m a t i o n from the f o r e g o i n g r e s u l t s , the o r g a n o - c l a y complexes were a t t a c k e d from two ang-l e s . F i r s t l y , the attempt was made to d e s t r o y o r g a n i c matter, and secondly i r o n o x i d e s . The complexes were s u b j e c t e d t o hy-drogen p e r o x i d e treatment to d e s t r o y o r g a n i c matter (88), and x-r a y d i f f r a c t i o n oa.terns were o b t a i n e d . Secondly, complexes were t r e a t e d w i t h c i t r a t e - d i t h i o n i t e t o remove i r o n o x i d e s ( 8 8 ) , and then s u b j e c t e d to x- r a y a n a l y s i s . In the i n t e r p r e t a t i o n o f x-ray r e s u l t s the main emphasis was p l a c e d on m i n e r a l o g y . The complexes were t r e a t e d f i r s t w i t h HgGV) to d e s t r o y o r g a n i c matter, f o l l o w e d by sodium c i t r a t e d i t h i o n i t e t o remove i r o n . The samples thus o b t a i n e d were d i v -i d e d i n t o two groups. The f i r s t batch was s a t u r a t e d w i t h po-ta s s i u m and the second w i t h magnesium. These m o n o i o n i c a l l y s a t -u r a t e d complexes were a g a i n d i v i d e d i n t o two groups. In both c a s e s one group o f samples was g l y c o l a t e d w h i l e the o t h e r was mounted on x-ray s l i d e s i n the u s u a l manner. The g l y c o l a t e d samples were a l l o w e d to stand f o r some time and then mounted on x-ray s l i d e s . A l l these samples v/ere s u b j e c t e d t o x-ray d i f -f r a c t i o n a n a l y s i s . I n f r a r e d Study: The i n f r a r e d s p e c t r o s c o p y has been used q u i t e f r e q u e n t l y i n the study o f atomic c o n f i g u r a t i o n s o f m i n e r a l m o l e c u l e s . The method adopted i s d e s c r i b e d b r i e f l y i n the f o l l o w i n g pages. A s m a l l amount of o r g a n o - c l a y complex (determined by t r i a l s ) was mixed w i t h anhydrous KBr t h o r o u g h l y and then compressed i n t o a p e l l e t 1 . 3 cm i n diameter and about 1 mm i n t h i c k n e s s . The i n f r a r e d s p e c t r a were r e c o r d e d on an Unican Instrument model 2 5 . SP. 200 G. i n f r a r e d spectrophotometer w i t h a p r i s m - g r a t i n g i n t e r c h a n g e . In the second p a r t o r g a n o - c l a y complexes were t r e a t e d w i t h hydrogen p e r o x i d e to d e s t r o y o r g a n i c matter and a g a i n i n f r a r e d s p e c t r a were r e c o r d e d f o r comparison. I n a d d i t i o n i n f r a r e d s p e c t r a o f pure m i n e r a l s c o m p r i s i n g m o n t m o r i l l o n i t e , v e r m i c u -l i t e , k a o l i n i t e , c h l o r i t e , i l l i t e and f e l d s p a r s o b t a i n e d from Ward's n a t u r a l s c i e n c e e s t a b l i s h m e n t were a l s o taken. These r e s u l t s were used i n c o n j u n c t i o n w i t h m i n e r a l i d e n t i f i c a t i o n and a s s o c i a t i o n o f m i n e r a l component and o r g a n i c f r a c t i o n . D i f f e r e n t i a l t hermal a n a l y s i s . In the p r e s e n t study on o r g a n o - c l a y complexes, "DUPONT" 900 d i f f e r e n t i a l t hermal u n i t was used. The change i n temper-a t u r e was m a i n t a i n e d a t 15°C per minute f o r b e t t e r r e s o l u t i o n . E x t r a c t a b i l i t y o f o r g a n i c matter from s e l e c t e d complexes: T h i s study was conducted w i t h a view to g e t t i n g some i d e a about the n a t u r e o f the combination of o r g a n i c f r a c t i o n w i t h m i n e r a l component. The o r g a n i c carbon was e x t r a c t e d by t h r e e s u c c e s s i v e treatments which are enumerated i n the f o l l o w i n g s e c t i o n . E x t r a c t i o n w i t h 0.1M Na^P^Q-: A 0 . 5 gm sample was t r a n s f e r r e d t o a p l a s t i c 100 ml tube a l o n g w i t h 10 ml e x t r a c t a n t (pH about 10). The tubes were st o p p e r e d and shaken g e n t l y by hand. Subsequently the samples were shaken o v e r n i g h t on a mechanical shaker. The o r g a n i c mat-t e r s o l u b i l i z e d by sodium pyrophosphate was s e p a r a t e d by h i g h speed c e n t r i f u g i n g f o r an hour. The p r o c e s s was c o n t i n u e d un-26. t i l no f u r t h e r e x t r a c t i o n was observed. The volume o f the ex-t r a c t was reduced by e v a p o r a t i n g a t low temperature and carbon was e s t i m a t e d by wet combustion ( 6 8 ) . The r e s i d u e was saved f o r the next o p e r a t i o n . E x t r a c t i o n w i t h 0.1N NaQH: The r e s i d u e was t r e a t e d w i t h 0.1N NaOH and shaken f o r 5 hours on a mechanical shaker. The o r g a n i c carbon s o l u b i l i z e d by sodium h y d r o x i d e was s e p a r a t e d by h i g h speed c e n t r i f u g i n g f o r one hour. The p r o c e s s was c o n t i n u e d u n t i l no f u r t h e r c o l -our was observed i n the e x t r a c t . On an average, 3-6 e x t r a c -t i o n s were found n e c e s s a r y . Organic carbon was e s t i m a t e d as s p e c i f i e d p r e v i o u s l y . E x t r a c t i o n w i t h 0.1M Na^PgOnafter HF-HC-£ treatment: The r e s i d u e was t r e a t e d w i t h HF-HC-& mixture p r e p a r e d by add i n g 1 ml HF (48%) t o 100 ml 0.1N HC-&. T h i s c o n c e n t r a t i o n i s c o n s i d e r e d to.be optimum ( 2 1 ) , t o d i s s o l v e s i l i c a t e m i n e r a l s . T h i s mixture was l e f t o v e r n i g h t and the sample was washed f r e e o f c h l o r i d e s . The carbon was e x t r a c t e d o v e r n i g h t w i t h sodium pyrophosphate. The s o l u b i l i z e d carbon was s e p a r a t e d by h i g h speed c e n t r i f u g i n g and e s t i m a t e d by wet combustion as b e f o r e . E x t r a c t a b l e I r o n , Aluminum and S i l i c o n : The method of Weaver et a l . (88), was used f o r e s t i m a t i n g the e x t r a c t a b l e i r o n , aluminum and s i l i c o n w i t h s l i g h t m o d i f i c a -t i o n s o u t l i n e d below. A 0 . 5 gm sample was t r a n s f e r r e d t o a p o l y e t h y l e n e c e n t r i -fuge tube a l o n g w i t h 5 ml c i t r a t e - b i c a r b o n a t e s o l u t i o n . The sample was heated t o 80°0 i n a water b a t h and h e a t i n g above 80°C was a v o i d e d , t o a v o i d FeS f o r m a t i o n . To the sample 0.1 gm 2 7 . Na.2&2®i). powder was added and s t i r r e d c o n t i n u o u s l y f o r one min-ute and then i n t e r m i t t e n t l y f o r 5 minutes. T h i s p r o c e s s was r e p e a t e d t h r e e t i m e s . A 5 ml s a t u r a t e d NaCX s o l u t i o n was added t o f l o c c u l a t e the sample. The suspension was mixed, warmed i n a water ba t h f o r 10 minutes and subsequently s u b j e c t e d to h i g h speed c e n t r i f u g i n g (1600-2200 rpm) f o r 5 - 1 0 minutes. The super-n a t a n t s o l u t i o n was c o l l e c t e d i n a 100 ml v o l u m e t r i c f l a s k and the r e s i d u e was washed w i t h IN NaCl£ and supernatant s o l u t i o n added to the v o l u m e t r i c f l a s k . The volume was made to 100 ml and mixed t h o r o u g h l y . The sample was t r a n s f e r r e d t o a 2 5 0 ml c o n i c a l f l a s k and a i r was bubbled through f o r 4 hours or more to o x i d i z e any r e m a i n i n g d i t h i o n i t e . S u i t a b l e a l i q u o t s were taken to determine i r o n , aluminum and s i l i c o n by atomic absorp-t i o n spectrophotometry, Humic: F u l v i c A c i d r a t i o : A 0 . 5 gm sample of complex was e x t r a c t e d w i t h a 5 ml mix-t u r e o f IN NaOH and 1M Na^P20- mixed i n equal p r o p o r t i o n . The humic a c i d was p r e c i p i t a t e d a t pH 2.0 and wet combustion method (68) was used f o r e s t i m a t i n g the carbon of humic and f u l v i c a c i d s . Carbohydrate c o n t e n t of complexes: A 0 . 3 gm sample of complex was t r a n s f e r r e d t o a 2 5 0 ml c o n i c a l f l a s k a l o n g w i t h 3 ml o f 7 2 $ HgSO^ and a l l o w e d to stand f o r one hour. The erlenmeyer f l a s k was covered w i t h a beaker a f t e r a d ding 100 ml d i s t i l l e d ELpO, and h y d r o l y s e d i n an a u t o -c l a v e a t 1 5 p s i and 124°C f o r one hour. The sample was a l l o w e d t o c o o l and then f i l t e r e d . The volume was made to 100 ml and s t o r e d i n a r e f r i g e r a t o r and c a r b o h y d r a t e s were determined by 28. using anthrone method"'". This method i s not a good measure of carbohydrates as i t measures only hexoses, however, i t i s a good index of carbohydrate measurement. Ivarson, K.C., and Sowden, F.J. 1962. S o i l S c i . 94, 245-250. 2 9 . RESULTS AND DISCUSSION  G e n e r a l c h a r a c t e r i s t i c s o f samples: T a b l e I I p r e s e n t s some p h y s i c o - c h e m i c a l p r o p e r t i e s o f the samples. The samples were a c i d i c i n n a t u r e and v a r i e d i n pH between 4 . 6 and 6 . 8 . The c l a y c o n t e n t , n i t r o g e n c o n t e n t , and carbon c o n t e n t ranged from 2 to 67, 0 .023 t o 0 .830 and 0.11 to 9 . 2 5 p e r c e n t r e s p e c t i v e l y . The o r g a n i c carbon d e c r e a s e d w i t h depth i n a l l p r o f i l e s except the O r t h i c P o d z o l and Humic P o d z o l , where a un i f o r m t r e n d was not o b v i o u s . N i t r o g e n showed the same r e l a t i o n s h i p t o depth whereas C/N r a t i o d i d not show any degree o f u n i f o r m i t y w i t h depth. Having o b t a i n e d t h i s p r e l i m i n a r y i n f o r m a t i o n , f u r t h e r a t -t e n t i o n was f o c u s s e d on the d i s t r i b u t i o n o f organo-clay com-p l e x e s and f i n d i n g s u i t a b l e methods f o r c h a r a c t e r i z i n g the com-p l e x e s . Comparison of t h r e e e x t r a c t i n g methods of o r g a n o - c l a y complexes. The e f f e c t i v e n e s s o f simple d i s p e r s i o n , u l t r a s o n i c a g i t a -t i o n and c h e l a t i n g r e s i n treatment was compared i n r e l a t i o n to y i e l d o f the complexes, t h e i r carbon c o n t e n t and the carbon o f the complexes r e p o r t e d as p e r c e n t o f t o t a l s o i l carbon. The r e s u l t s are summarized i n the f o l l o w i n g pages under d i f f e r e n t h e a dings. Y i e l d o f complexes: The y i e l d o f complexes o b t a i n e d by the t h r e e methods i s p r e -s e n t e d i n T a b l e I I I and summarized below. The average amount of complexes i n the case o f simple d i s p e r s i o n , i n s o n a t i o n and c h e l -a t i n g r e s i n was 2 . 5 8 , 3.41 and 12.30% r e s p e c t i v e l y . The y i e l d Some Characte Soil Subgroups Humic eluviated gleysol Orthic Concre-tionary Brown Orthic regosol Horizons Ah Ahe (Aeg) Bg (Btg) BC Cg Bfcc Bfcc Bf C Ap C, C L 2 1 (Bm) (II O Depth in inches 0.9 9-12.5 12.5-21 21-34 34+ 0-1.5 1.5-15 15-27 27+ 0-7 7-23 23+ _i_H_ 5.50 5.75 6.30 6.40 6.70 5.70 5.60 5.80 6.40 5.90 5.80 6.10 Orthic Podzol LF 3-2 — H 2-0 — Ae 0-2 4.70 Bf. (Bhf) 2-11 5.30 Bf' 11-20 5.30 Cg2 20+ 5.70 Humic Podzol LF 2.5-2 —— FH 2-0 — — Aeh 0-1 4.60 Bhf 1-2.5 5.20 Bf 2.5-14 5.50 Cg 14+ 5.80 Acid Brown Ap 0-2 5.30 Wooded Bf 2-10 6.00 BC 10-27 5.60 C 27+ 5.80 Humic gleysol Ah 0-7 5.60 Btg 7-18 6.00 C 18+ 6.80 Orthic gleysol Ap 0-5 5.30 Btg 5-17 5.80 Bg 17+ 6.60 TABLE II :istics of Soil Samples Clav % Ore?. C "/ . N % 17.0 9.25 0.83 40.0 3.64 0.33 67.0 0.65 0.09 53.5 0.30 0.07 27.0 0.23 0.034 14.0 5.63 0.314 13.5 1 .60 0.129 11.0 0.54 0.045 27.5 0.11 0.023 11 .0 2.80 0.297 17.5 0.93 0.118 4.0 0.19 0.023 6.0 2.15 0.053 5.1 2.62 0.083 2.0 3.34 0.139 6.2 0.68 0.076 11.0 2.47 0.113 12.5 7.90 0.308 6.1 3.08 0.165 10.0 1 .53 0.077 9.9 8.50 0.466 10.5 2.30 0.103 18.5 1.13 0.066 30.3 0.19 0.037 42.5 5.44 0.403 51 .5 2.34 0.148 33.5 0.60 0.027 45.3 5.21 0.500 47.0 1 .32 0.128 50.5 0.62 0.038 C/N ratio Textural class 11.1 Loam 11.2 Silty clay loam 7.2 Clay 4 .5 Clay C6C8 Clay loam 17.9 S i l t loam 12.4 S i l t loam 12.0 Loam 4.8 S i l t loam 9.4 Loam 7.9 Loam 8.3 Sandy loam 40.6 Sandy loam 30.1 Loamy sand 24.0 Loamy sand 9.0 Sand 21 .9 Loam 25.7 Loam 18.7 Sandy loam 19.9 Loam 18.2 S i l t loam 22.3 S i l t loam 17.1 S i l t loam 5.1 Silty clay loam 13.5 Silty clay 15.8 Silty clay 22.2 Silty clay loam 10.4 Silty clay 10.3 Clay 16.3 Silty clay 3 1 . TABLE I I I Y i e l d o f o r g a n o - c l a y complexes o b t a i n e d by th r e e methods expressed as percent of a i r dry s o i l  S o i l Subgroups H o r i z o n s Y i e l d (%) Simple U l t r a - C h e l a t i n g d i s p e r s i o n s o n i c s R e s i n Humic E l u v i a t e d Ah 0.64 4 . 0 0 13.97 G l e y s o l Ahe (Aeg) 0.56 2 .00 18.71 Bg (Btg) 3.20 4.40 25.50 BC 3.60 5.00 20.30 Og 10.40 11.80 12.68 O r t h i c Concre- Bfcc-. 1.12 1.20 11.03 t i o n a r y Brown Bfcc£ 1.65 2.50 11.57 Bf t L 2.00 2.40 10.99 C 2 . 0 0 2.60 14 . 3 3 O r t h i c R e g o s o l Ap 0.80 0.80 8.35 C, (Bm) 1.50 2.40 7.92 C^ ( I I C ) 1.20 2.00 2.96 O r t h i c Podzol- LF w — — — xl Ae 0.60 0 . 9 0 5 .94 Bf, (Bhf) 0 . 3 0 0 .50 5 .03 B f i 0 . 3 0 0 .30 1.25 e g 2 0.40 0 . 5 0 4 . 0 0 Humic P o d z o l ,LF mm — „ HF — — Aeh 0 . 3 5 0.40 3.47 Bhf 0 . 2 5 0 . 2 0 7.15 B f 0.15 0 . 2 0 6.01 Cg 0.26 0.40 3-10 A c i d Brown Ap 0.29 0.30 7.84 wooded Bf 0 . 2 0 0 . 2 0 10.14 BC 1.85 1.90 11.06 C 2.15 3.20 18 . 9 5 Humic G l e y s o l Ah 4.28 5.40 21.75 B t g 7.69 8.60 25.70 C 7.04 7-10 14 . 6 3 O r t h i c G l e y s o l Ap 2.81 3.90 19 . 9 6 B t g i . 9 . 4 8 10.10 24 . 7 0 Bg 10.42 17.20 19.96 Average 2.58 3.41 12.30 3 2 . o f complexes d i d not agree w i t h the c l a y c o n t e n t i n every case, but r o u g h l y on an average i t was comparable. On the whole c h e l -a t i n g r e s i n gave h i g h e r v a l u e s due p r o b a b l y to h i g h pH and z e t a p o t e n t i a l . From T a b l e I I I i t i s e v i d e n t t h a t the y i e l d of complexes o b t a i n e d by c h e l a t i n g r e s i n was s u b s t a n t i a l l y h i g h e r than simple d i s p e r s i o n and u l t r a s o n i c treatment. However, the y i e l d s by simple d i s p e r s i o n and i n s o n a t i o n were comparable, b e i n g a l i t t l e h i g h e r i n the case o f u l t r a s o n i c treatment. C h e l a t i n g r e s i n seems to be a good method of i s o l a t i n g the complexes as f a r as y i e l d i s concerned. No g e n e r a l t r e n d was observed as f a r as the d i s t r i b u t i o n o f complexes w i t h depth was concerned but u s u a l l y i n the case o f i n s o n a t i o n and simple d i s p e r s i o n the h i g h e r y i e l d o f complex-es was observed i n the lower h o r i z o n s i n comparison to the s u r -f a c e . However, t h i s o b s e r v a t i o n was not e q u a l l y t r u e i n the case o f c h e l a t i n g r e s i n . Data of T a b l e I I I suggest t h a t c h e l a -t i n g r e s i n i s f a r s u p e r i o r to i n s o n a t i o n and simple d i s p e r s i o n i n i s o l a t i n g the complexes. However, i n the p r e s e n t i n v e s t i g a -t i o n t h i s d i d not appear to be the case a f t e r a c r i t i c a l e v a l -u a t i o n of the t h r e e methods which w i l l be d i s c u s s e d a t the end o f t h i s c h a p t e r . P e r c e n t carbon i n complexes: Tab l e IV p r e s e n t s the p e r c e n t carbon i n the complexes ob-t a i n e d by the t h r e e methods. The average carbon c o n t e n t i n the complexes o b t a i n e d by simple d i s p e r s i o n , u l t r a s o n i c s and r e s i n t reatment, was 5 . 0 1 , 5 . 3 3 and 4 . 7 0 p e r c e n t r e s p e c t i v e l y . I t i s i n t e r e s t i n g t o note t h a t the complexes o b t a i n e d by u l t r a s o n i c 33. TABLE IV P e r c e n t carbon i n complexes o b t a i n e d by t h r e e methods S o i l Subgroups H o r i z o n s P e r c e n t Carbon Simple U l t r a -d i s p e r s i o n s o n i c s R e s i n Humic E l u v i a t e d Ah 11.16 1 1 . 1 2 1 0 . 5 0 G l e y s o l Ahe (Aeg) 6.39 5 . 0 3 4.60 Bg (Btg) 0.32 0 . 9 3 0 . 7 0 BG 0.61 0 . 6 6 2.00 Og 0.60 0 . 3 9 0 . 5 0 O r t h i c Concre- B f c c , 6 . 3 9 9 . 9 7 2.60 t i o n a r y Brown B f c c i 3 . 1 0 4 . 4 3 2 . 6 9 Bf d 1.28 3.08 0 . 3 5 G 0 . 4 7 0.43 0.38 O r t h i c Regosol Ap 4.64 5 . 2 0 5 . 2 3 C, (Bm) 2 . 1 9 2 . 6 6 2 . 1 9 c 2 (no) 1 . 4 3 1.38 0 . 9 5 O r t h i c P o d z o l LP u — — — n Ae 3 - 3 7 6.16 1 1 . 9 4 Bf, ( Bhf) 10.24 8 . 7 1 11.11 11 . 11 1 3 . 2 0 1 0 . 9 7 og 2 4.41 5 . 0 9 7 . 7 0 Humic P o d z o l LF -— — —_ HF — — — Aeh 4 . 1 9 6 . 7 5 9.26 Bhf 1 5 . 5 2 1 0 . 7 1 18 . 3 9 Bf 14 . 6 9 2 1 . 7 6 0.68 OS 18 . 6 6 9 . 0 3 7 . 6 3 A c i d Brown Ap 9-59 10.14 9.46 wooded Bf 4 . 3 3 6 . 0 3 4 . 3 7 BC 2 . 2 9 2 . 9 4 1.86 C 0 . 9 7 0 . 5 3 0 . 3 1 Humic G l e y s o l Ah 3 . 8 5 4.44 4 . 6 7 B t g 2 . 3 3 2 . 2 9 2 . 7 7 C 0.81 0 . 7 5 0.66 O r t h i c G l e y s o l Ap 3 . 2 3 4 . 1 2 4 . 0 2 B t g 1 . 0 7 1 . 0 5 1 . 2 7 Bg 0 . 6 9 1.00 0 . 8 3 Average 5.01 5 . 3 3 4 . 7 0 3 4 . treatment c o n t a i n e d the h i g h e s t mean carbon c o n t e n t . However, t h i s t r e n d was not c o n s i s t e n t when v a l u e s f o r i n d i v i d u a l samples were examined. P e r c e n t carbon i n the complexes of samples o f a l l p r o f i l e s except the O r t h i c and Humic P o d z o l , were s i m i l a r f o r a l l t h r e e d i s p e r s i o n methods, except i n the case o f the complex from the BC h o r i z o n o f the Humic E l u v i a t e d G l e y s o l o b t a i n e d by r e s i n t r e a t m e n t . In the case o f the Humic P o d z o l and the O r t h i c Pod-z o l the movement o f e a s i l y s o l u b l e o r g a n i c f r a c t i o n s c o u p l e d w i t h the movement o f complexes appears v e r y r a p i d i n comparison t o o t h e r s o i l Great Groups, except i n the Cg h o r i z o n complexes o f these s o i l s . The p e r c e n t carbon i n the Ae h o r i z o n of Humic P o d z o l i c s o i l was lower i n comparison to o t h e r h o r i z o n s except i n the case o f complexes o b t a i n e d by r e s i n treatment where p e r -c e n t carbon was observed to be lower i n B f h o r i z o n . However, i n the case of the O r t h i c P o d z o l the r e s u l t s were not q u i t e s i m i l a r . I t i s h y p o t h e s i z e d t h a t under c e r t a i n c i r c u m s t a n c e s r e s i n treatment s o l u b i l i z e s some f r a c t i o n o f o r g a n i c matter due to h i g h pH which may come i n c o n t a c t w i t h f r e e ' s u r f a c e s o f c l a y m i n e r a l s , and t h e r e b y c r e a t i n g new complexes. Such a p o s s i b i l -i t y r a i s e d the q u e s t i o n as to the s u i t a b i l i t y o f the method f o r q u a l i t a t i v e study. However, the s p l i t t i n g o f o r g a n i c matter from the complexes due to h i g h pH seems more pronounced. S i m i l a r l y , though simple d i s p e r s i o n does not seem so sev-ere as r e s i n treatment, i t appears to b r i n g about some hydro-l y t i c e f f e c t s due to p r o l o n g e d c o n t a c t of sample w i t h water. The e f f e c t o f r e s i n treatment and h y d r o l y s i s may v a r y depending upon the n a t u r e of the m i n e r a l s p e c i e s and o r g a n i c f r a c t i o n as 35. w e l l . Qarbon i n c l a y - o r g a n i c complexes as percent of t o t a l s o i l carbon T h i s parameter i s very important, being an index of complex fo r m a t i o n . I n the past t h i s has been used very f r e q u e n t l y i n t h i s f i e l d , but at some p l a c e s i t appears m i s l e a d i n g without • s p e c i f y i n g the o r i g i n , nature and m i n e r a l o g i c a l composition along w i t h the nature of organic matter. Therefore, keeping these p o i n t s i n mind, the r e s u l t s of Table V are summarised be-low. The average carbon of the complexes as percent of the t o t a l s o i l carbon by simple d i s p e r s i o n , i n s o n a t i o n and r e s i n t r e a t -ment, was found to be 4.64, 6.34 and 2 2 . 1 3 % r e s p e c t i v e l y . I n the case of simple d i s p e r s i o n and u l t r a s o n i c d i s p e r s i o n , t h i s v a l u e showed an i n c r e a s i n g t r e n d w i t h depth. This may be a t -t r i b u t e d to the most a c t i v e and s o l u b l e f r a c t i o n of the humus moving downward through the solum and which tends to a s s o c i a t e , i t s e l f w i t h the m i n e r a l f r a c t i o n of the s o i l . However, t h i s t r e n d seems to be d i s t u r b e d by the oxides of i r o n , aluminum and other m u l t i v a l e n t metals which i s obvious from the Humic and O r t h i c Podzol P r o f i l e s where the aforementioned sequence does not e x i s t . Some workers ( 2 7,28) however, c o n s i d e r t h a t the m u l t i v a l -ent metals are a p o t e n t i a l source of complex formation through what they c a l l b r idge mechanisms. T h i s aspect needs f u r t h e r examination because the r e s u l t s of Table V appear to c o n t r a d i c t t h i s assumption. The complexes obtained by r e s i n treatment d i d not show any s p e c i f i c t r e n d of d i s t r i b u t i o n w i t h depth. The complex carbon 36. TABLE V Organo-clay complex carbon as p e r c e n t of t o t a l s o i l carbon S o i l Subgroups H o r i z o n s P e r c e n t Carbon Simple U l t r a -d i s p e r s i o n s o n i c s R e s i n Humic E l u v i a t e d Ah 0.78 4.80 15-86 G l e y s o l Ahe (Aeg) 0 . 9 8 2.76 23.65 Bg (Btg) 4 . 0 5 6 .34 27.46 BC 7-33 11.00 45.10 Cg 27.13 2 0 . 0 0 27.57 O r t h i c Concre- B f c c , 1.27 2.12 7-87 t i o n a r y Brown B f c c i 3.20 6.93 19-45 Bf d- 4 . 7 4 13.69 2 0 . 4 4 C 8 . 5 4 10.27 49.55 O r t h i c R e g o s o l Ap 1.33 1.49 15.60 C, (Bm) 3.54 6 .86 18 . 6 5 C^ ( I I C) 9 . 0 5 14 . 5 3 14 . 79 O r t h i c P o d z o l LF •a — — — Jtl Ae 0 . 9 4 2.58 32.98 Bf, ( Bhf) 1.17 1.66 21.33 B f i 1.00 1.19 2 3 .81 e g 2 2.59 3.75 45.29 Humic P o d z o l LF —.— HF — Aeh 0.60 1.09 13.61 Bhf 0.49 0.27 16.64 Bf 0.71 1.41 1.33 Cg 3.17 2.36 15.46 A c i d Brown Ap 0.33 0 .36 8.73 wooded Bf 0.38 0.53 19.27 BC 3.75 4 . 9 5 18 . 2 0 C 11.00 8 .95 30.89 Humic G l e y s o l Ah 3.03 4.41 18 . 6 7 B t g 7.66 8.41 30.42 C 9.50 8 .88 16 . 1 0 O r t h i c G l e y s o l Ap 1.74 3.04 15.40 B t g 7.68 8 . 0 3 23.77 Bg 11.60 27.66 26 . 7 3 Average 4.64 6.34 22.13 3 7 . as p e r c e n t o f t o t a l s o i l carbon v a r i e d between 0 . 3 3 and 2 7 . 1 3 , 0 . 2 7 and 2 7.66 and 1 . 3 3 and 4 9 . 5 5 p e r c e n t by simple d i s p e r s i o n , u l t r a s o n i c d i s p e r s i o n and r e s i n treatment r e s p e c t i v e l y . Ifc seems worth n o t i n g t h a t i n no case d i d t h i s f i g u r e exceed 49.6$ which i s q u i t e c o n t r a d i c t o r y w i t h o t h e r workers ( 4 0 , 4 6 , 5 0 ) r e -s u l t s . However, many of these workers used heavy l i q u i d s of d i f f e r e n t d e n s i t i e s f o r f r a c t i o n a t i n g s o i l s i n t o d i f f e r e n t groups which, t h e r e f o r e , s h o u l d be termed organo-mineral com-p l e x e s r a t h e r than o r g a n o - c l a y complexes, s i n c e the m a t e r i a l s were not r e s t r i c t e d to the<"2/c f r a c t i o n . Secondly, the p o s s i b -i l i t y o f p r o d u c i n g a r t e f a c t s due to the i n t r o d u c t i o n o f o r g a n i c l i q u i d s a l s o e x i s t s . But the r e s u l t s of Trofimenko and h i s a s -s o c i a t e s (84) who worked on o r g a n o - c l a y complexes, are q u i t e comparable w i t h the r e s u l t s o f t h i s i n v e s t i g a t i o n . At t h i s stage i t seems a d v i s a b l e t o make a c o n c l u d i n g r e -mark s p e c i f i c a l l y about the s e l e c t i o n o f u l t r a s o n i c d i s p e r s i o n f o r c h a r a c t e r i z a t i o n , and about C u t t i n g down the number o f sam-p l e s to o n l y e i g h t . I t appeared l e g i t i m a t e to cut down the number o f samples to a s m a l l e r one when the f i r s t phase was over, to permit more d e t a i l e d s t u d i e s w i t h i n a r e a s o n a b l e p e r i o d of time. In . a l l , e i g h t samples were chosen f o r d e t a i l e d c h a r a c t e r i z a t i o n based on s i m i l a r i t y and d i s s i m i l a r i t y of the samples i n r e l a t i o n to carbon c o n t e n t , and r e p r e s e n t i n g a wide range i n p r o p e r t i e s . S econdly, a f t e r examining the complexes q u a l i t a t i v e l y and q u a n t i t a t i v e l y , i n s o n a t i o n was p r e f e r r e d f o r f u r t h e r d e t a i l e d c h a r a c t e r i z a t i o n o f these complexes. I t i s e v i d e n t from Table I I I and T a b l e IV t h a t simple d i s p e r s i o n . i s a poor method and a 3 8 . slow p r o c e s s o f i s o l a t i o n and i n some cases a l s o appeared to b r i n g about some h y d r o l y t i c e f f e c t s . R e s i n treatment i n the m a j o r i t y o f the cases i s o l a t e d f a r g r e a t e r amounts of complexes, p o s s i b l y due to h i g h pH thus s p l i t t i n g o f f the o r g a n i c f r a c t i o n from the complex. T h e r e f o r e , a f t e r c o n s i d e r i n g a l l o f these f a c t o r s , the use o f u l t r a s o n i c d i s p e r s i o n was c o n s i d e r e d p r e f -e r a b l e . I t s h o u l d a l s o be emphasized t h a t t h i s method was not found t o be the b e s t f o r i s o l a t i n g maximum y i e l d o f the complex-es, but i t was found s a t i s f a c t o r y i n b r i n g i n g about d i s p e r s i o n without changing the complexes much i n comparison t o the o t h e r methods examined. Speed o f i s o l a t i o n was a l s o an a d d i t i o n a l ad-vantage of t h i s method. C h a r a c t e r i z a t i o n o f o r g a n o - c l a y complexes. Organo-clay complexes o b t a i n e d by u l t r a s o n i c treatment were c h a r a c t e r i z e d by u s i n g x-ray d i f f r a c t i o n , i n f r a r e d a b s o r p t i o n , d i f f e r e n t i a l t hermal a n a l y s i s and d i f f e r e n t e x t r a c t i n g r e a g e n t s , which are summarized below. X - r a y d i f f r a c t i o n a n a l y s i s : The r e s u l t s o f x- r a y d i f f r a c t i o n a n a l y s i s are r e p o r t e d i n T a b l e VI and enumerated i n the f o l l o w i n g pages. In most o f the samples examined, c h l o r i t e was found i n ma-j o r q u a n t i t y except i n the Ae h o r i z o n sample of the O r t h i c Pod-z o l . V e r m i c u l i t e was of second order i n r e l a t i o n t o q u a n t i t y . I l l i t e was p r e s e n t up t o the extent o f 10-15 p e r c e n t , however, k a o l i n i t e was t o t a l l y absent. The amount of amphibole i n the Cg h o r i z o n sample o f the Humic P o d z o l was a l s o s i g n i f i c a n t . The complexes were a l s o s u b j e c t e d t o x- r a y d i f f r a c t i o n a n a l y s i s a f t e r g l y c o l a t i o n to observe any expansion. However, i n no case TABLE VI Soil Subgroups Humic Eluviated Gleysol Orthic Concre-tionary Brown Orthic Podzol Humic Podzol Orthic Gleysol ** 5 4 3 2 1 65 %+ 65-40$ 40-205$ 20-10$ 10- 1$ Clay minerals in selected complexes. Chlor- Montmor- Vermic-Horizons ite i l l o n i t e ulite I l l i t e Ah 3 — 2 1-2 Cg (Data based on x-ray diffraction a n a l y s e s ) . Bfcc. Ae Bhf Cg Btg 1-2 3-4 Mixed Layer Quartz 2 1-2 1-2 1-2 1-2 1-2 Amphi-bole Feld-spars 1 1-2 Treatments ^2Q2 a n d c i ' t r a " t 8 ~ d i ' t n i o n i ' t e (f° r details see methods) Comparison of X-ray data before and afte;r treatment. Lower peak heights probably due to Fe or some other interlamellar material in 148 region which was lost on ^2^2 ^•ceB'^ ment. Lower peak heights in untreated samples probably due to Fe interference Not as complete collapse of vermicu-l i t e as in treated sample when heated to 5001 C and slightly lower 14n spac-ing after h^ C1^ treatment. Untreated complex gave 13. peak which became 14.28 after ^^02 a n d citrate-dithionite treatment. 13. peak is probably due to binding of the micelles together by organic matter which became broader on H-D2 treatment. Low peak heights in both cases prob-ably due to Fe interference or amorph-ous material. Lower peak heights in untreated complex and 14.2°-peak shifted to 14.028 on h^ O,, treatment. The high Background probably due to Fe and H2O2 treatment did not change 14.488 peaR probably due to the un-accessibility of organic matter to H 2 ° 2 ' 108 peak in untreated possible com-plex and 188 peak lo s t on "^02 treat-ment. 40. was such expansion observed. Humic E l u v i a t e d G l e y s o l : The Ah h o r i z o n sample was observed to c o n t a i n c h l o r i t e , v e r m i c u l i t e , and i l l i t e as the major m i n e r a l s , f o l l o w e d by minor q u a n t i t i e s o f q u a r t z and f e l d s p a r s . I n t e r l a m e l l a r i n c l u s i o n s i n the 148 and 188 r e g i o n were observed. However, the 18.8 peak dropped t o 148 a f t e r t r e a t i n g w i t h H 20 2 s u g g e s t i n g i n t e r l a m e l l a r i n c l u s i o n o f o r g a n i c matter. The Cg sample c o n t a i n e d more v e r -m i c u l i t e than c h l o r i t e but v e r y s l i g h t i n t e r s t r a t i f i c a t i o n was observed o n l y i n the 148 regxon. O r t h i c C o n c r e t i o n a r y Brown: The B f c c 2 n o r i - z o n sample c o n t a i n e d more v e r m i c u l i t e than c h l o r i t e w i t h 10-15$ Q u a r t z . Amphibole and f e l d s p a r s were a l s o p r e s e n t i n minor amounts. An i n t e r l a m e l l a r i n c l u s i o n i n the 148 r e g i o n was observed but c o u l d not be a t t r i b u t e d t o any min-e r a l s p e c i e s . O r t h i c P o d z o l : The Ae h o r i z o n sample c o n t a i n e d a s i g n i f i c a n t amount of m o n t m o r i l l o n i t e f o l l o w e d by v e r m i c u l i t e which e x h i b i t e d peaks a t 13.608 and 14.9?8. I t was conc l u d e d t h a t the 13.608 peak was due to o r g a n i c components b i n d i n g the a d j a c e n t m i c e l l e s t o -g e t h e r and 14.97^ peak was a t t r i b u t e d t o Fe, Mg or A l . However, the B f 2 sample d i d not have any m o n t m o r i l l o n i t e , a l t h o u g h some i n d i c a t i o n s o f o r g a n o - c l a y i n t e r a c t i o n was observed. The p r e s -ence o f a h i g h amount of m o n t m o r i l l o n i t e i n the Ae h o r i z o n sample appears q u i t e unusual and f o r e s t f i r e f i g h t i n g may be the source o f c o n t a m i n a t i o n . 41. Humic P o d z o l : N e i t h e r the Bhf or the Cg sample o f t h i s s o i l c o n t a i n e d any m o n t m o r i l l o n i t e . However, i t c o n t a i n e d i l l i t e which was absent from the O r t h i c P o d z o l samples. I n t e r s t r a t i f i c a t i o n i n the more than 14A* r e g i o n was observed, p r o b a b l y due to o r g a n i c m a t t e r . The Cg sample c o n t a i n e d a c o n s i d e r a b l e amount of am-p h i b o l e . O r t h i c G l e y s o l : The B t g sample c o n t a i n e d some m o n t m o r i l l o n i t e and the 18$ peak was a t t r i b u t e d t o the i n t e r l a m e l l a r i n c l u s i o n of o r g a n i c m a t t e r . T h e r e f o r e , i t can be mentioned by way of summary t h a t x - r a y d i f f r a c t i o n a n a l y s e s r e v e a l e d some u s e f u l i n f o r m a t i o n and i t s h o u l d a l s o be remembered t h a t i n t e r l a m e l l a r i n c l u s i o n o f o r g a n i c m a t e r i a l does not always r e s u l t i n expanding the m i n e r a l c r y s t a l , but sometimes i t tends t o b i n d the m i c e l l e s t o g e t h e r , thus r e d u c i n g the normal s p a c i n g s . I n f r a r e d a b s o r p t i o n a n a l y s i s : An i n f r a r e d study was conducted to s u b s t a n t i a t e the x-ray d i f f r a c t i o n a n a l y s e s and t o observe the bonding mechanisms o f o r g a n i c and i n o r g a n i c components as w e l l . I t was found an use-f u l approach f o r m i n e r a l i d e n t i f i c a t i o n and c h a r a c t e r i z a t i o n of complexes, P i g . 1 and 2 r e p r e s e n t (a) the i n f r a r e d s p e c t r a o f complexes, and (b) the complexes a f t e r treatment w i t h -^2^2' The complexes were t r e a t e d w i t h H 202 and i n f r a r e d s p e c t r a were taken w i t h a view t o o b s e r v i n g changes i n the s p e c t r a . I n f r a -r e d s p e c t r a o f pure m i n e r a l s ( s p e c i f i e d p r e v i o u s l y ) were a l s o used as an a i d i n m i n e r a l i d e n t i f i c a t i o n . I t i s i n t e r e s t i n g to note t h a t the i n f r a r e d spectrum of 42. 25 3 WAVELENGTH p fe 7 10 12 14 ORTHIC CONCRETIONARY BROWN Bfcc, HUMIC PODZOL (Cg) 4000 3000 2000 1750 1500 1250 1000 750 650 • - . WAVENUMBER FIG. I Infrared spectra of complexes obtained by insonation. a. Complexes. b. Complexes a f t e r HgOg treatment. 4 3 . the complex o b t a i n e d from the B t g sample o f the O r t h i c G l e y s o l i s j u s t about a s t r a i g h t l i n e over a wide range. However, a f t e r t reatment w i t h H 2 0 2 i t gave a d i s t i n c t l o o p ( a term commonly used i n c h e m i c a l j o u r n a l s ) i n the 9 « 9 to l Q ^ r e g i o n . T h i s r e g i o n i s v e r y important as i t p r o b a b l y c o v e r s aluminum o c t a -h e d r a l sheet and s i l i c o n - o x y g e n l i n k a g e s . The r e g i o n 8 . 5 to 1 0 . i s t y p i c a l o f g l u c o s i d i c - l i n k a g e s and o t h e r p o l y m e r i c sub-s t a n c e s . A s i g n i f i c a n t amount o f c a r b o h y d r a t e s were a l s o ob-s e r v e d i n t h i s a s s o c i a t i o n . I n f r a r e d s p e c t r a o f the Ah h o r i z o n sample and Cg sample o f the Humic B l u v i a t e d G l e y s o l were not v e r y d i f f e r e n t except the Ah sample showed a d i s t i n c t a b s o r p -t i o n band i n the 10 t o l l ^ r e g i o n where s i l i c o n may have been bonded t o some o r g a n i c component through oxygen. The O r t h i c C o n c r e t i o n a r y Brown B f c c 2 sample e x h i b i t e d a s l i g h t a b s o r p t i o n band around 10.6°/^ which became more pronoun-c e d a f t e r t r e a t i n g the sample w i t h B^G^* I t i s suggested t h a t s i l i c o n may be bonded to some o t h e r components through oxygen. There was no i n d i c a t i o n o f N-H s t r e t c h i n g i n the 3 . 0 5 ^ r e g i o n . The i n f r a r e d spectrum o f the Ae sample was d i f f e r e n t from t h a t o f the B f 2 sample of the O r t h i c P o d z o l s o i l . I t was, how-ever, a t t r i b u t e d t o m i n e r a l o g y as the Ae sample c o n t a i n e d mont-m o r i l l o n i t e which was absent from the B f 2 sample. I t was noted however, t h a t the IB. spectrum o f the complex o b t a i n e d from the Cg sample o f the Humic P o d z o l a g a i n showed an almost s t r a i g h t l i n e , which became c o m p l e t e l y d i f f e r e n t upon H 2 0 2 t r e a t m e n t . I t i s c o n c l u d e d t h a t IR a n a l y s i s gave some i n t e r e s t i n g i n -f o r m a t i o n when c o u p l e d w i t h x - r a y d i f f r a c t i o n . I t i s suggested t h a t under c e r t a i n c o n d i t i o n s g l u c o s i d e s c o u l d be bonded t o 44. '8 I 2 FIG. I I V " I i s ^ r a r e d spectra of complexes obtained by insonation. a. Complexes. b« Complexes after B202 t r e a' f c m e n'k» •1000 3200 WAVELENGTH' p e HUMIC ELUVIATED GLEYSOL (Cg) ORTHIC GLEYSOL (Big) .2000 1750 1500 WM'ENUMBER 1250 ICOO • 750 650 > 4-4-. 45. c e r t a i n minerals and likewise some alkanes d i r e c t l y to s i l i c o n through oxygen linkages. The p o s s i b i l i t y of carbonyl groups bonding to surface cations of c e r t a i n minerals depending upon surface charge cannot be r u l e d out. There was no c l e a r cut i n -d i c a t i o n of bonding organic components to minerals through NH-linkages. However, the comparatively low percent of organic matter makes i t u n l i k e l y that f i n e d e t a i l s of spectra due to organic components could be revealed. D i f f e r e n t i a l thermal a n a l y s i s : The complexes obtained by u l t r a s o n i c dispersion were sub-jected to d i f f e r e n t i a l thermal analysis up to only about 600°C due to the t e c h n i c a l d i f f i c u l t i e s with the high temperature c e l l which probably would have given more information. However, i t supported the r e s u l t s of x-ray d i f f r a c t i o n and i n f r a r e d absorp-t i o n i n r e l a t i o n to mineralogy. Small peaks near 3 0 0 to 3 2 0 were observed i n each sample but the curve was more pronounced i n the case of the Cg sample of Humic Podzol. This was probably due to organic matter eli m i n a t i o n . A prominent curve observed by Schnitzer and h i s associate ( 7 5 , 7 6 ) at 400°C due to phenolics was not seen i n the present i n v e s t i g a t i o n . This may be due to the dominance of f u l v i c f r a c t i o n i n the complexes. E x t r a c t a b i l i t y of carbon from complexes: Table VHXpresents the carbon and nitrogen content of the complexes along with the carbon extracted with d i f f e r e n t reagents i n succession. The V a r i a t i o n i n the C/N r a t i o , which ranged from 5*5 "to 1 7 , suggested that the nature of the organic compo-nents i n d i f f e r e n t complexes also v a r i e d . In general the n i t r o -gen content of the complexes appeared to be high and high C/N TABLE VII C, N contents and C extracted with successive treatments from selected organo-clay complexes* Soil Subgroups Horizons % C % N Humic Eluviated Ah Gleysol j. C/N Ratio 11.12 1.39 8.00 0.39 0.06 6.50 0.1 M N a4 P2°7 50.0 37.5 Percent carbon recovered 0.1N NaOH 13.8 6.3 0.1 M Na.P_0 After HF-HC1 treatment 25.0 27.1 Not extracted 11.2 29.1 Orthic Concre-tionary Brown Bfcc. 4.43 0.26 17.04 54.5 6.8 19.9 18.8 Orthic Podzol Ae Bf. 6.16 0.56 11.00 45.3 11.3 13.20 0.83 15.90 53.9 1.9 32.0 26.2 11.4 18.0 Humic Podzol Bhf 10.71 1.20 8.93 62.8 Cg 9.03 0.55 16.42 46.0 4.9 8.3 13.0 23.1 19.3 22.6 Orthic Gleysol Btg 1.05 0.19 5.53 49.9 1.5 20.7 7.9 * Complexes were obtained by the use of Ultrasonic dispersion. 47. r a t i o s suggested t h a t o r g a n i c components i n t h i s a s s o c i a t i o n may perhaps i n c l u d e l o n g c h a i n a l i p h a t i c hydrocarbons. I t was observed t h a t on an average, ^0% o f the o r g a n i c f r a c t i o n o f the complexes was e x t r a c t e d by sodium pyrophosphate Pyrophosphate e x t r a c t e d the l a r g e s t p r o p o r t i o n s o f carbon from the BfcCg sample o f the O r t h i c C o n c r e t i o n a r y Brown, the B f 2 sample o f the O r t h i c P o d z o l and the Bhf sample o f the Humic Pod z o l , s u g g e s t i n g t h a t m u l t i v a l e n t c a t i o n s may be i n v o l v e d i n com p l e x i n g . The amount o f carbon e x t r a c t e d from the complexes w i t h NaOH and s i m i l a r l y the r e l e a s e o f o r g a n i c matter a f t e r HF-HG& treatment was not v e r y s i g n i f i c a n t . The m a t e r i a l s a f t e r HF-HG& treatment may w e l l be s i m i l a r i n n a t u r e t o t h a t r e m a i n i n i n r e s i d u e , s i n c e the s i n g l e HF-HG&- treatment was l i k e l y i n s u f -f i c i e n t t o l i b e r a t e maximum amounts of o r g a n i c m a t t e r . The h i g h e r amount o f carbon l e f t over i n the Cg samples suggested c o m p a r a t i v e l y more s t a b l e form o f the o r g a n i c f r a c t i o n . I t was co n c l u d e d t h a t the percentage o f o r g a n i c m a t t e r ex-t r a c t e d w i t h sodium pyrophosphate was c o m p a r a t i v e l y h i g h e r from the samples w i t h a f a i r l y h i g h content o f e x t r a c t a b l e i r o n , sug g e s t i n g the complex f o r m a t i o n through m u l t i v a l e n t c a t i o n l i n k -ages. T h i s f i n d i n g i s i n accordance with. Edwards and Bremner's (28) c o n c l u s i o n s . However, t h i s i s p r o b a b l y not the o n l y mech-anism and s e c o n d l y , the e x t e n t and importance of t h i s mechanism i s s t i l l not f u l l y u n d e r s t o o d . C h a r a c t e r i s t i c s o f the o r g a n i c f r a c t i o n e x t r a c t e d from s e l e c t e d complexes. T a b l e V I I I p r e s e n t s the Humic A c i d (HA): F u l v i c A c i d (FA) r a t i o , FA as p e r c e n t o f e x t r a c t e d o r g a n i c matter and carbohyd-48. TABLE V I I I C h a r a c t e r i s t i c s o f the o r g a n i c components e x t r a c t e d from s e l e c t e d complexes S o i l Subgroups H o r i z o n s Humic e l u v -i a t e d G l e y s o l O r t h i c Concre-t i o n a r y Brown O r t h i c P o d z o l Humic P o d z o l Ah Cg Bfcc, Ae B f 2 Bhf Cg Humic A c i d : F u l v i c A c i d R a t i o 0.20 0.08 0 . 6 7 2 .33 1.72 F u l v i c A c i d as % o f ex-t r a c t e d o r -gani c matter 83 93 100 60 30 *37 100 Carbohy-drate-C as % o f t o t a l complex carbon 7.7 109.0 6.4 12.6 6.8 8.4 3 . 3 O r t h i c G l e y s o l B t g 100 16.6 49-r a t e carbon as p e r c e n t of the t o t a l complex carbon. The HA: FA r a t i o ranged from 0.08 to 2.33 whereas the FA as p e r c e n t o f the e x t r a c t e d o r g a n i c matter v a r i e d from 30 to 100$. The p e r c e n t FA was lower i n the case o f the B f ^ h o r i z o n sample of the O r t h i c P o d z o l and Bhf sample of the Humic P o d z o l . T h i s may be due to the h i g h c o n c e n t r a t i o n o f s e s q u i o x i d e s i n these samples. The B f c c 2 s a m P l e o f ^ e O r t h i c C o n c r e t i o n a r y Brown, the Cg sample o f the Humic P o d z o l and the B t g h o r i z o n sample o f the O r t h i c G l e y s o l c o n t a i n e d 100$ o f the o r g a n i c m a t e r i a l i n the F u l v i c A c i d f r a c t i o n . The s i g n i f i c a n c e of t h i s o b s e r v a t i o n however, i s not f u l l y u n derstood. Carbohydrate carbon as p e r c e n t o f the t o t a l complex carbon ranged between 3«3 to 16.6$, but the Cg h o r i z o n sample o f the Humic E l u v i a t e d G l e y s o l showed an anomalous percentage o f 109 which seems more l i k e l y due to a n a l y t i c a l e r r o r s a s s o c i a t e d w i t h low l e v e l s o f c a r b o h y d r a t e and t o t a l carbon. D i t h i o n i t e - C i t r a t e e x t r a c t s o f complexes and s o i l s . The amount o f e x t r a c t a b l e i r o n , ' aluminum and s i l i c o n o f s o i l s and t h e i r r e s p e c t i v e complexes i s g i v e n i n T a b l e IX. There was a marked enrichment o f e x t r a c t a b l e F e , A l , and S i i n P o d z o l i c samples i n the f i n e r f r a c t i o n of the s o i l . There was no i n t e r - r e l a t i o n s h i p between the amount o f i r o n and carbon con-t e n t o f the complexes, which l e n d s no support to the c a t i o n ';> b r i d g e mechanism t h e o r y . However, the amount o f i r o n d i d appear t o be r e l a t e d t o the e x t r a c t a b i l i t y o f carbon w i t h sodium p y r o -phosphate from the complexes. The amount of carbon e x t r a c t e d from the complexes was h i g h e r i n samples h i g h i n i r o n . T h i s i s i n d i c a t e d by d a t a f o r the B f c c p , B f p , and the Bhf ( T a b l e V I I and 50. and V I I I ) samples o f the O r t h i c c o n c r e t i o n a r y Brown, the O r t h i c P o d z o l , and the Humic P o d z o l r e s p e c t i v e l y . TABLE IX D i t h i o n i t e , extractable Fe, A l and S i of S o i l s and Complexes Percent i n S o i l s Percent i n Complexes S o i l Subgroups Horizons Fe A l S i Fe A l S i Humic eluviated Gleysol Ah OS 2.20 1.20 1.28 0.16 0.42 0.54 2.33 1.83 1.60 2 .07 0.53 0.62 Orthic Concre-tionary Brown B f c c 2 1 .95 0 . 9 2 0.39 5 .50 2.60 0 .97 Orthic Podzol Ae 0.53 0.18 0 .25 2.08 0 . 9 0 0.68 B f 2 1 .50 2.10 0.62 6.33 6 .70 2.44 Humic Podzol Bhf 2 . 10 3.12 0.74 4 .83 6.60 1 .70 Cg 0,98 1.38 0.45 4.00 3-20 1 .37 Orthic Gleysol Btg 2.40 0 . 5 0 0.68 2.00 0 .37 0.64 52. SUMMARY AMD CONCLUSION T h i r t y - f o u r samples from e i g h t s o i l s which r e p r e s e n t e d e i g h t s o i l g r e a t groups, were c o l l e c t e d and s t u d i e d f o r the d i s -t r i b u t i o n of o r g a n o - c l a y complexes and o t h e r c h a r a c t e r i s t i c s . The complexes were a n a l y s e d f o r t h e i r carbon content which was a l s o expressed on the t o t a l s o i l carbon b a s i s . Three meth-ods, v i z : - simple d i s p e r s i o n , i n s o n a t i o n , and c h e l a t i n g r e s i n , were used f o r i s o l a t i n g o r g a n o - c l a y complexes and t h e i r e f f e c t -i v e n e s s was a s s e s s e d . The amount of complexes o b t a i n e d by sim-p l e d i s p e r s i o n v a r i e d between 0 .15 and 10.42 w i t h an average of 2 . 5 8 ; by i n s o n a t i o n , between 0 . 2 0 and 1 ? . 2 0 w i t h an average of 3.41; and by c h e l a t i n g r e s i n , between 1.25 and 25 .70 w i t h an average o f 1 2 . 3 0 . The percent carbon i n the complexes was observed between 0.47 and 18 . 6 6 p e r c e n t w i t h an average of 5*01 by simple d i s -p e r s i o n ; between 0 .39 and 21 .76 p e r c e n t w i t h an average o f 5*33 by u l t r a s o n i c d i s p e r s i o n , and between 0 .31 and 18 . 3 9 p e r c e n t w i t h an average o f 4 . 7 0 by c h e l a t i n g r e s i n . A v e r y important parameter, v i z carbon of o r g a n o - c l a y com-p l e x e s , e x p r e s s e d as p e r c e n t o f the t o t a l s o i l carbon by simple d i s p e r s i o n , u l t r a s o n i c d i s p e r s i o n and c h e l a t i n g r e s i n , was found between 0 .33 and 27.13 w i t h an average o f 4.64; 0 . 2 7 and 27.66 w i t h an average o f 6 . 3 4 , and 1.33 and 49 . 5 5 with an average of 22.13 r e s p e c t i v e l y . I t i s f e l t t h a t the c h e l a t i n g r e s i n i s a good agent f o r o b t a i n i n g h i g h e r y i e l d s o f complexes which i s pr o b a b l y due to a d i s p e r s i o n e f f e c t and h i g h pH. However, c o n s i d e r i n g the q u a l i t y o f complexes, i n s o n a t i o n was c o n s i d e r e d the p r e f e r a b l e method. 53. T h i s method a l s o had the advantage o f r e l a t i v e speed and con-v e n i e n c e . F o r c h a r a c t e r i z a t i o n o n l y e i g h t complexes were s e l e c t e d and were found to v a r y i n carbon, n i t r o g e n , e x t r a c t a b l e i r o n , aluminum and s i l i c o n c o n t e n t . The amount o f carbon e x t r a c t e d from d i f f e r e n t complexes w i t h d i f f e r e n t r e a g e n t s used i n suc-c e s s i o n , was a l s o d i f f e r e n t . The 0/N r a t i o o f the s e complexes v a r i e d between 5*5 and 17.0. The HA: FA r a t i o s i n d i c a t e d t h a t a major p r o p o r t i o n of the o r g a n i c component i n t h i s a s s o c i a t i o n was o f f u l v i c n a t u r e , except i n the case o f the P o d z o l i c B f sample, i n which about t w o - t h i r d s o f the e x t r a c t a b l e m a t e r i a l was i n the humic f r a c t i o n . T h i s o b s e r v a t i o n may be o f some s i g -n i f i c a n c e i n e x p l a i n i n g the p r o c e s s o f complex f o r m a t i o n . The ca r b o h y d r a t e c o n t e n t o f the complexes accounted f o r o n l y 3«3 and 16.6% o f the complex carbon. X-ray d i f f r a c t i o n and i n f r a r e d s t u d i e s were a l s o made. The mine r a l o g y was not observed t o d i f f e r t o any e x t e n t except i n the A e - h o r i z o n o f the O r t h i c P o d z o l and the BJfg-horizon o f the O r t h i c G l e y s o l where m o n t m o r i l l o n i t e was observed i n s i g -n i f i c a n t amounts. I n most o f the samples examined, i n t e r l a m e l -l a r entrapment o f the o r g a n i c carbon was a l s o observed. There was a l s o evidence s u g g e s t i n g t h a t m u l t i v a l e n t c a t i o n s are not always the means o f complex f o r m a t i o n as i s r e p o r t e d by some workers (27,28). I n f r a r e d study a l s o gave some important i n f o r m a t i o n about m i n e r a l o g y and suggested some p o s s i b l e bonding mechanisms. In some cases some evidence o f g l u c o s i d e l i n k a g e s i n the 8 . 5 - 1 0 . ^ r e g i o n was a l s o observed. There was a l s o some i n d i c a t i o n o f 5*-bonding o f s i l i c o n to o r g a n i c compounds through oxygen l i n k a g e s . However, t h e r e was no evidence o f amide l i n k a g e s between o r g a n i c m a tter and c l a y m i n e r a l s , which may have not been r e v e a l e d due t o low c o n c e n t r a t i o n of o r g a n i c components i n the complexes. 5 5 . 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