UBC Theses and Dissertations

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UBC Theses and Dissertations

Minimizing the environmental impact of urea de-icer from airport runways Ferguson, Keith Donald 1977

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MINIMIZING THE ENVIRONMENTAL IMPACT OF UREA DE-ICER FROM AIRPORT RUNWAYS by KEITH DONALD FERGUSON B.A.Sc., U n i v e r s i t y of B r i t i s h Columbia, 1975 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES (Dept. o f C i v i l Engineer ing) We accept t h i s t h e s i s as conforming to the r equ i r ed standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1977 (e) Keith Donald Ferguson, 1977 In presenting th i s thes is in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary shal l make it f ree ly ava i lab le for reference and study. I fur ther agree that permission for extensive copying of th i s thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th is thes i s fo r f inanc ia l gain sha l l not be allowed without my wr i t ten permission. Department of C i v i l , E n g i n e e r i n g The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 6 i i A b s t r a c t U r e a f i n d s common use a t mos t a i r p o r t s i n Canada whe re i t i s u s e d as an a n t i - i c e r o r d e - i c e r . U r e a c o n t a i n s up t o 46% n i t r o g e n w h i c h f i n d s i t s way t o t h e e n v i r o n m e n t a r o u n d t h e a i r p o r t . Of t h e p o t e n t i a l e n v i r o n m e n t a l p r o b l e m s , e u t r o -p h i c a t i o n o f l a k e s i s o f t h e mos t c o n c e r n i n B r i t i s h C o l u m b i a . S e v e r a l me thod s f o r m i n i m i z i n g t h e i m p a c t o f u r e a d e -i c e r we re c o n s i d e r e d . U r e a can be h y d r o l y z e d t o ammonia by t h e common s o i l enzyme u r e a s e on an a i r p o r t runway and t h i s am-m o n i a can v o l a t i l i z e t o t h e a t m o s p h e r e . The n a t u r a l e n z y m a t i c a c t i v i t y on r unway t e s t s e c t i o n s was f o u n d t o c a u s e l e s s t h a n 0 . 5 % o f t h e a p p l i e d u r e a t o h y d r o l y z e w i t h no v o l a t i l i z a t i o n a f t e r 90 m i n u t e s , a t room t e m p e r a t u r e . S u p p l e m e n t a l u r e a s e was added t o p y r e x m o d e l s t o t e s t t h e e f f e c t o f v a r i o u s c o n -d i t i o n s on h y d r o l y s i s and v o l a t i l i z a t i o n . T h i r t y - t w o t e s t s we re p e r f o r m e d a t v a r i o u s t e m p e r a t u r e s ( - 4 , 0 , 4 , 1 2 0 C ) , u r e a s e a d d i t i o n s (1 00 , 200 , 500 , 750 mg/mode l ) , i c e t h i c k n e s s e s ( 3 , 5 , 8 mm), u r e a a p p l i c a t i o n s ( 0 . 4 5 , 0 . 9 , 1.8 k g / 7 0 m 2 ) , u r e a t y p e s ( C o m i n c o I n d u s t r i a l and F o r e s t r y G r a d e , S h e r r i t t G o r d o n M i n e s I n d u s t r i a l G r a d e ) and s o l a r r a d i a t i o n s (50 and 100 B T U / h - f t 2 ) . An a d d i t i o n o f 500 mg u r e a s e t o t h e mode l c u a s e d h y d r o l y s i s o f 65% o f t h e a p p l i e d u r e a and v o l a t i l i z a t i o n o f 1% a t 1 2 ° C . L o w e r t e m p e r a t u r e s p r o d u c e d p o o r e r r e s u l t s . R e l a t i v e t o t h e h i g h c o s t s and l ow e f f i c i e n c y , c o n t r o l o f u r e a t h r o u g h h y d r o -l y s i s and v o l a t i l i z a t i o n on an a i r p o r t runway i s i m p r a c t i c a l . i i i B i o l o g i c a l n i t r i f i c a t i o n - d e n t r i f i c a t i o n , b r e a k p o i n t c h i o r i n a t i o n , s e l e c t i v e i o n e x c h a n g e , and a i r s t r i p p i n g have h i g h n i t r o g e n r e m o v a l e f f i c i e n c i e s u n d e r n o r m a l c o n d i t i o n s , b u t a r e n o t s u i t a b l e f o r w i n t e r a i r p o r t o p e r a t i o n . P a s s a g e o f u r e a t h r o u g h s o i l c an be an e f f e c t i v e method f o r r e m o v a l o f t h i s d e - i c i n g a g e n t i f t h e q u a n t i t y o f n i t r a t e and u r e a l e a c h e d t o s u r f a c e w a t e r s i s l o w . P u b l i s h e d d a t a i n -d i c a t e s t h a t s o i l c o u l d be 7 5 - 9 0 % e f f i c i e n t i n c o n t r o l l i n g n i -t r o g e n l o s s t o s u r f a c e and g r o u n d w a t e r s . A r e d u c t i o n i n t h e q u a n t i t y o f u r e a u s ed on a r unway w o u l d d e c r e a s e t h e e n v i r o n m e n t a l i m p a c t . The y e l l o w a u r a p r o -d u c e d by t h e u r e a - E h r l i c h r e a g e n t r e a c t i o n , was u s ed t o m o n i -t o r t h e movement o f u r e a i n 5 mm t h i c k i c e a t - 4 ° C . A f t e r 90 m i n u t e s f r o m p l a c e m e n t on t h e i c e , t h e C o m i n c o F o r e s t r y G r a d e a u r a c o v e r e d t h e l a r g e s t a r e a . On a w e i g h t b a s i s , h o w e v e r , t h e S h e r r i t t G o r d o n M i n e s c o v e r e d t h e l a r g e s t a r e a . T h i s g r e a t e r a u r a c o v e r a g e i s due t o t h e s m a l l e r p a r t i c l e s i z e o f t h e S h e r r i t t G o r d o n M i n e s p e l l e t s . I f t h e s i z e o f t h e a u r a can be c o r r e l a t e d w i t h t h e e a s e o f r e m o v a l o f i c e f r o m an a i r p o r t r u n w a y , t h e n t h e S h e r r i t t G o r d o n M i n e s - I n d u s t r i a l G r a d e u r e a i s more e f f e c -t i v e as a d e - i c e r t h a n e i t h e r o f t h e two C o m i n c o g r a d e s u n d e r t h e c o n d i t i o n s t e s t e d . F u r t h e r r e s e a r c h i s " recommended i n o p t i m i z i n g t h e use o f u r e a and s o i l t r e a t m e n t . i v t a b l e o f C o n t e n t s Page L i s t o f T a b l e s v L i s t o f F i g u r e s v i A c k n o w l e d g e m e n t v i i i 1. I n t r o d u c t i o n 1 1.1 U r e a P e l l e t A c t i o n 7 1.2 The E n v i r o n m e n t a l I m p a c t o f U r e a 11, 1.2.1 The P r o b l e m 11 1 .2 .2 U r e a N i t r o g e n P a t h w a y s 12 2. M i n i m i z i n g t h e E n v i r o n m e n t a l I m p a c t 31 E x p e r i m e n t a l R e s e a r c h 32 2.1 V o l a t i l i z a t i o n o f Ammonia by U r e a s e on A i r p o r t Runways 32 2 .1 .1 N a t u r a l E n z y m a t i c A c t i v i t y o f A i r p o r t Runway 36 2 . 1 . 2 A d d i t i o n o f Enzyme t o I n c r e a s e A c t i v i t y : 38 2 .2 R e d u c t i o n o f U r e a Use 57 L i t e r a t u r e R e v i e w o f N i t r o g e n Remova l 76 T r e a t m e n t S y s t e m s 2 . 3 B i o l o g i c a l N i t r i f i c a t i o n -Den i t r i f i c a t i on 76 2 .4 B r e a k p o i n t C h l o r i n a t i o n 78 2 .5 S e l e c t i v e Ion E x c h a n g e 81 2 .6 A i r S t r i p p i n g 83 2 . 7 C o l l e c t i o n - D i s p o s a l 84 3. C o n c l u s i o n s 87 4. F u r t h e r R e s e a r c h 96 L i t e r a t u r e C i t e d 1 0 3 V L i s t o f T a b l e s Page 1. C h e m i c a l F o r m u l a t i o n s C o n s i d e r e d f o r I c e C o n t r o l 3 2. C o m i n c o U r e a P r o d u c t Da t a 6 3. Q u a n t i t i e s o f U r e a Used a t A i r p o r t s i n B .C . D u r i n g 1 9 7 5 - 7 6 8 4. N i t r o g e n R e c o v e r e d f r o m C l a y S o i l s 16 5. V o l a t i l i z a t i o n o f Ammonia i n S o i l s 20 6. V o l a t i l i z a t i o n o f Ammonia i n Loams 2V 7. P l a n t U p t a k e o f N i t r o g e n 24 8. S o i l N i t r o g e n L e a c h i n g L o s s e s 30 9. N a t u r a l E n z y m a t i c A c t i v i t y o f A i r p o r t Runway 37 10 . H y d r o l y s i s R e s u l t i n g f r o m U r e a s e A d d i t i o n 44 1 1 . S c r e e n A n a l y s i s f o r U r e a T ype s 60 2 12 . A u r a A r e a a t 90 m i n . f o r m 0 .9 kg/70m Urea 77 V I L i s t o f F i g u r e s Page 1. U r e a - I c e - W a t e r E u t e c t i c D i a g r a m 9 2. P o s s i b l e U r e a D e - i c e r N i t r o g e n P a t h w a y s 13 3. V o l a t i 1 i z a t i o n - o f Ammonia S t u d y F l o w Diagram 33 4 . M o n t h l y V a r i a t i o n o f I n s o l a t i o n a t 5 6 ° N.L. • u - 40 5. M o n t h l y V a r i a t i o n o f I n s o l a t i o n a t 4 8 ° N.L. V 41 6. Key t o " P i e D i a g r a m s " 45 7. E f f e c t o f T e m p e r a t u r e a t 5mm I c e and 0 . 90 kg/70 2 U r e a 47 3 m 8. P e r c e n t a g e U r e a H y d r o l y z e d v s . T e m p e r a t u r e 48 9 . E f f e c t o f U r e a s e a t 0°C and 0 . 90 k g / 7 0 m 2 u r e a , 49 10 . P e r c e n t U rea H y d r o l y z e d v s . U r e a s e C o n c e n t r a t i o n 50 1 1 . E f f e c t o f I c e T h i c k n e s s a t 0°C and 200 mg U r e a s e A d d i t i o n 52 12 . E f f e c t o f U r e a A p p l i c a t i o n R a t e a t 0°C , 200 mg U r e a s e , and 5mm I c e T h i c k n e s s 53 13 . E f f e c t o f U r e a Type a t 200 mg U r e a s e and 1.8 k g / 7 0 m 2 U r e a 54 14 . E f f e c t o f U r e a Type a t 200 mg. U r e a s e and 5 mm. I c e T h i c k n e s s 55 15 . E f f e c t o f S o l a r R a d i a t i o n a t - 4 ° C , 5mm I c e , a n d 0 . 90 k g / 7 0 m 2 U r e a 56 1 6 . E h r l i c h R e a g e n t C a l i b r a t i o n C u r v e 59 17 . 1 Gram o f t h e T h r e e T y p e s o f U r e a 61 1 8 . A u r a ( a t 90 m i n . ) f o r "Domed G r i d E x p e r i m e n t " 63 v i i Page 19 . SGM-IG A u r a G r o w t h 64 2 0 . C - IG A u r a G r o w t h 65 2 1 . C-FG A u r a G r o w t h 66 22 . C -FG P e l l e t and A u r a a t 15 m i n . 67 2 3 . C -FG A u r a a t 90 m i n . 68 2 4 . A u r a C o v e r a g e A r e a v s . T ime 69 2 5 . A v e r a g e R a t e o f A u r a G r o w t h 70 26 A u r a G r o w t h p e r W e i g h t o f U r e a 72 2 7 . SGM-IG A u r a f o r U r e a a t 0 . 90 k g / 7 0 m 2 73 28 C - IG A u r a f o r U r e a . a t 0 . 9 kg/70 2 74 3 m 2 9 . C-FG A u r a f o r U r e a a t 0 .9 kg/70 2 75 J m 30 . N i t r i f i c a t i o n - D e n i t r i f i c a t i o n F l o w D i a g r a m 79 3 1 . S e l e c t i v e Ion E x c h a n g e F l o w D i a g r a m 82 32 . I c e S c r a p e r M e c h a n i s m 100 v if i A c k n o w l e d g e m e n t The a u t h o r w i s h e s t o a c k n o w l e d g e t h e f o l l o w i n g f o r t h e i r a s s i s t a n c e i n t h i s r e s e a r c h : D r . R. D. Cameron - A s s i s t a n t P r o f e s s o r o f C i v i l E n g i n e e r i n g , U . B . C , T h e s i s S u p e r v i s o r M r s . E. M a c D o n a l d - Head Lab T e c h n i c i a n , E n v i r o n m e n t a l E n g i n e e r i n g L a b o r a t o r y , U . B . C . Members o f t h e N a t i o n a l U r e a S t u d y C o m m i t t e e : Mr. M. H a w k i n s , T r a n s p o r t C a n a d a - O t t a w a , C o m m i t t e e C h a i r m a n Mr. G. P e t t i g r e w , T r a n s p o r t Canada - P a c i f i c R e g i o n Mr . W. S o p e r , E n v i r o n m e n t Canada - P a c i f i c R e g i o n D r . J . B e a t o n , C h i e f A g r o n o m i s t , Cominco L t d . Mr. A. R o s s , E n v i r o n m e n t Canada - O t t a w a and , Mr. R. D. L e w i s , R.D. L e w i s and A s s o c i a t e s L t d . 1 1. I n t r o d u c t i o n I c e can be e x t r e m e l y d a n g e r o u s on an a i r p o r t r u n w a y . A i r -p l a n e s mus t have good t r a c t i o n when l a n d i n g and t a k i n g o f f . S i n c e many o f C a n a d a ' s a i r p o r t s are subjected: to c o l d a n d i c y w i n t e r s , d e v e l o p m e n t o f a f a s t - a c t i n g , e c o n o m i c a l , e f f i c i e n t , and s a f e means o f r e m o v i n g i c e was i m p e r a t i v e . I c e u s u a l l y f o r m s u n d e r t h e f o l l o w i n g c o n d i t i o n s ^ : a ) S u p e r - c o o l e d r a i n c o n t a c t i n g a c o l d s o l i d . b) M o i s t u r e i n a i r , c o n d e n s i n g on a c o l d s u r f a c e . c ) W h e e l e d t r a f f i c on we t snow o r s l u s h c o m p a c t i n g i t i n t o i c e . d) A w a r m i n g c o n d i t i o n f o l l o w e d by a r e t u r n t o b e l o w f r e e z i n g , p e r m i t t i n g snow m e l t t o r e f r e e z e . e) I n s u f f i c i e n t o r c l o g g e d d r a i n s p e r m i t t i n g w a t e r t o o v e r f l o w o n t o t h e p a v e m e n t , and w i t h d e c r e a s -i n g t e m p e r a t u r e c a u s i n g i c e . f ) J e t e n g i n e h e a t m e l t i n g snow d u r i n g l ow t e r m p e r a -t u r e s . The a d h e s i v e s t r e n g t h o f i c e t o p a v e m e n t s can be as h i g h c 2 2 as 8 . 3 x 1 0 N/m (120 l b / i n ) , w h i c h i s a p p r o a c h i n g t h e t e n s i l e 2 s t r e n g t h o f i c e . T h i s bond c a n n o t u s u a l l y be b r o k e n w i t h o u t a f a i l u r e i n t h e i c e . S c r a p i n g by m e c h a n i c a l means o f t e n l e a v e s a t h i n c o a t o f i c e o r damages t h e p a v e m e n t . A c c o r d i n g t o t h e M i n i s t r y o f T r a n s p o r t (MOT) g u i d e l i n e s , 3 snow and i c e c o n t r o l m a t e r i a l s must meet two b a s i c c r i t e r i a : a) They must p r o v i d e t h e r e q u i r e d e f f e c t i n p r e v e n t i o n o f o r r e m o v i n g snow and i c e t o p r o d u c e pa vemen t s u r f a c e s s a f e f o r a i r c r a f t o p e r a t i o n s . b) They must be c o m p a t i b l e w i t h p e r s o n n e l , p a v e m e n t , e q u i p m e n t , and a i r c r a f t d e p e n d i n g on t h e i r l o c a t i o n o f u se ( g r o u n d s i d e o r a i r s i d e ) . I c e c o n t r o l c h e m i c a l s can be v e r y e f f i c i e n t i n m e l t i n g 2 i c e . C h e m i c a l s , h o w e v e r , must p a s s a s e r i e s o f a i r c r a f t com-p a t i b i l i t y t e s t s , b e f o r e t h e y a r e c o n s i d e r e d f o r r unway e x p e r i m e n t s . From 1 962-1 972 , many c h e m i c a l s were t e s t e d , . a s ; shown, i n T a b l e 1. Of t h e s e 42 c h e m i c a l s , o n l y f o u r have met t h e c o m p a t -i b i l i t y r e q u i r e m e n t s o f MOT f o r c o r r o s i o n c o n t r o l . T h e s e a r e , t h e l i q u i d c h e m i c a l s , M o n s a n t o S a n t o m e l t 9 9 0 C R ( 4 1 ) , K a i s e r I s o l v ( 3 9 ) , U n i o n C a r b i d e U c a r ( 3 8 ) , and t h e s o l i d , U r e a ( 4 2 ) . B e c a u s e t e s t s p e r f o r m e d by t h e MOT u s i n g t h e f o u r a p p r o v e d c h e m i c a l s i n d i c a t e d t h a t none o f t h e l i q u i d c h e m i c a l s s u r p a s s e d u r e a i n t e r m s o f r e a c t i o n t i m e and r a t e o f a p p l i c a t i o n , u r e a i s t h e c h e m i c a l u sed a l m o s t e x c l u s i v e l y a t a l l C a n a d i a n a i r -4 p o r t s . C h e m i c a l s can be a p p l i e d t o a r unway s u r f a c e i n two w a y s , " d e - i c i n g and a n t i - i c i n g ^ - . D e - i c i n g i n v o l v e s a p p l y i n g t h e c h e m i c a l a f t e r i c e has f o r m e d . A f t e r t h e c h e m i c a l has r e d u c e d t h e i c e - p a v e m e n t bond s t r e n g t h , t h e i c e i s r e m o v e d by m e c h a n i c a l means . The p r a c t i c e o f p l a c i n g t h e c h e m i c a l on a r unway t o p r e v e n t i c e f o r m a t i o n i s c a l l e d a n t i - i c i n g . A n t i - i c i n g i s a c k n o w l e d g e d t o be more e f f e c t i v e t h a n d e - i c i n g f o r i c e c o n t r o l . MOT have s e t t h e f o l l o w i n g p e r f o r m a n c e c r i t e r i a f o r a n t i - i c i n g and d e - i c i n g ^ . " F o r a n t i - i c i n g -The i c e c o n t r o l c h e m i c a l , when a p p l i e d p r i o r t o o r d u r i n g a f r e e z i n g r a i n , o r a l o w e r i n g o f t e m p e r a t u r e , s h a l l p r e v e n t t h e c o - e f f i c i e n t o f f r i c t i o n f r o m f a l l i n g b e l o w h a l f t h e v a l u e o f t h e c l e a n d r y p a v e m e n t ; and w i l l r e n d e r p o s s i b l e t h e r e m o v a l o f i c e / s l u s h c o n -t a m i n a n t by p h y s i c a l mean s . T a b l e 1 3 C h e m i c a l F o r m u l a t i o n s C o n s i d e r e d f o r I c e C o n t r o l A c e t a m i de Ammonium A c e t a t e Formami de S od i um S u l f a t e Ammonium N i t r a t e Ammonium F o r m a t e T r i p o t a s s i u m P h o s p h a t e A c e t a m i de/Amnion i urn A c e t a t e ( 9 0 / 1 0 ) U r e a / A c e t a m i d e ( 7 5 / 2 5 ) S o d i u m S u l f a t e / F o r m a m i d e ( 7 5 / 2 5 ) T r i p o t a s s i u m P h o s p h a t e / U r e a ( 7 5 / 2 5 ) A c e t a m i d e / U r e a ( 5 0 / 5 0 ) Ace tam ide/Ammon iu rn A c e t a t e ( 7 5 / 2 5 ) Ammonium A c e t a t e / A c e t a m i d e ( 7 5 / 2 5 ) M o n s a n t o " A " M o n s a n t o 1D1 352B Urea/Amnion i urn F o r m a t e ( 5 0 / 5 0 ) Urea/Ammonium F o r m a t e ( 7 5 / 2 5 ) Ammonium A c e t a t e / U r e a ( 5 0 / 5 0 ) Ammonium A c e t a t e / F o r m a m i d e ( 7 5 / 2 5 ) Urea/Ammonium N i t r a t e ( 7 5 / 2 5 ) U r e a / F o r m a m i d e / W a t e r ( 2 0 / 7 5 / 5 ) U r e a / F o r m a m i d e / W a t e r ( 1 0 / 8 5 / 5 ) F o r m a m i d e / W a t e r ( 8 5 / 1 5 ) F o r m a m i d e / I s o p r o p y l A l c o h o l / W a t e r ( 6 2 / 2 7 / 1 1 ) C a l c i u m F o r m a t e S a n f a x IM-149 (Ca<Cl 9 ) I s o p r o p y l A l c o h o l H a r t l i n e P r o d u c t s Company " I n s t a m e l t NC" ( U r e a ) Momar C h e m i c a l s Company " I c e - g o " ( C a C l ? ) W a l t o n - M a r c h I n c o r p o r a t e d " I c e - F o e " R e v e r e C h e m i c a l I n c o r p o r a t e d " I c e - M e l t e r " (Ca.Cl 2) Monroe Company D e - i c i n g " F l u i d X - 5 4 " 4 T a b l e I - C o n t i n u e d : 34) M o n s a n t o TKPP ( s o l i d p e l l e t s ) 35) A l l i e d C h e m i c a l s ARD-45 36) Dow C h e m i c a l A i r c r a f t D e - i c i n g F l u i d 146/Sand M i x t u r e 37) G l y c o l / S a n d M i x t u r e 38) U n i o n C a r b i d e U c a r Runway D e - i c e r 39) K a i s e r I s o l v 40) L y n d h u r s t Runway D e - i c e r 41) M o n s a n t o S a n t o m e l t 990CR 42) U r e a 5 F o r d e - i c i n g -The i c e c o n t r o l c h e m i c a l a p p l i c a t i o n s h a l l r a i s e t h e s u r f a c e c o - e f f i c i e n t o f f r i c t i o n o f i c e t o a t l e a s t h a l f t h e v a l u e o f t h e c l e a n d r y pavemen t w i t h i n one hou r o f a p p l i c a t i o n and w i l l r e n d e r p o s s i b l e t h e r e m o v a l o f i c e / s l u s h c o n t a m i n a n t by p h y s i c a l m e a n s . " O n l y f o u r m a t e r i a l s a r e r e g u l a r l y us'ed i n t h e c o n t r o l o f i c e and snow a t C a n a d i a n a i r p o r t s . S od i um c h l o r i d e i s u sed o n l y on t h e g r o u n d s i d e ( a r e a s n o t t r a v e l l e d by a i r c r a f t ) s i n c e i t c a u s e s u n a c c e p t a b l e c o r r o s i o n t o a i r c r a f t . C a l c i u m c h l o r i d e i s a l s o u s e d o n l y on t h e g r o u n d s i d e . Sand o f s p e c i f i c s i z e and q u a l i t y i s u s e d on t h e g r o u n d s i d e and a i r s i d e . L a r g e a g g r e g a t e s can damage e n g i n e s and a i r c r a f t s u r f a c e s . S m a l l s and s i z e s a r e l e s s e f f e c t i v e i n i m p r o v i n g the. c o e f f i c i e n t o f f r i c t i o n . U r e a i s t h e o n l y c h e m i c a l u sed on s u r f a c e s whe re a i r c r a f t m a n o e u v r e . U r e a i s a c o m m e r c i a l s y n t h e t i c a c i d a m i d e o f c a r b o n i c a c i d w i t h a c h e m i c a l f o r m u l a - C O f N H g ^ * N i t r o g e n a c c o u n t s f o r a b o u t 46% o f t h e t o t a l w e i g h t ( T a b l e 2 ) . I t i s n o r m a l l y u sed as an a g r i c u l t u r a l f e r t i l i z e r . A i r p o r t d e - i c e r u r e a i s g r a n u l a r o r p e l l e t i n f o r m . C l a y , m i n e r a l o i l , o r f o r m a l d e h y d e may be a d d e d t o p r e v e n t t h e p e l l e t s f r o m c a k i n g . C o n v e n t i o n a l s a n d i n g e q u i p m e n t i s u s e d t o a p p l y t h e u r e a p e l l e t s . When u s e d as an a n t i - i c e r , an a p p l i c a t i o n r a t e o f 0 . 4 5 kg (1 l b , ) o f u r e a p e r 70 s q u a r e m e t e r s (750 f t ) o f r unway i s r e c o m m e n d e d . T h i s i s e q u i v a l e n t t o 45kg (100 l b ) p e r e a c h 305 m e t e r s (1000 f t , ) o f r u n w a y . O n l y t h e c e n t r e 23m. (75 f t ) o f t h e r u n w a y i s t r e a t e d d u r i n g t i m e s o f l o w c r o s s -6 T a b l e 2 Com inco U r e a P r o d u c t Da t a UREA - A N T I - I C I N G GRADE - ( 4 6 - 0 - 0 ) DESCR IPT ION: A p u r e g r a d e o f u r e a , NH^CONH^, i n g r a n u l a r f o r m t o w h i c h a c o n d i t i o n i n g a g e n t has been added t o m a i n t a i n a f r e e - f l o w i n g c h a r a c t e r i s t i c . I t i s w h i t e i n c o l o r . I t i s m a n u f a c t u r e d by r e a c t i n g ammonia w i t h c a r b o n d i o x i d e a t s u i t a b l y h i g h p r e s s u r e and e l e v a t e d t e m p e r a t u r e . GUARANTEED A N A L Y S I S : TYP ICAL ANALYS I S T o t a l n i t r o g e n , N ( n o t T o t a l n i t r o g e n , N . . . B i u r e t , NH o C0NHC0NH 9 g u a r a n t e e d ) 2 2 A d d i t i v e Comb i ned M o i s t u r e , 46% 46 . 5% 1 . 3% . 31% 0 . 0 5 % SCREEN ANALYSES : ( T y l e r S t a n d a r d ) Mesh +8 +10 +14 +20 % 70 9 9 . 5 9 9 . 8 9 9 . 9 $H OF AQUEOUS SOLUTION: 8 7 w i n d s . In t h e p r e s e n c e o f s t r o n g c r o s s w i n d s , t h e s p r e a d e r v e h i c l e i s d r i v e n on t h e w i n d w a r d s i d e o f c e n t r e . When u r e a i s u sed f o r d e - i c i n g , as much snow and i c e i s r e m o v e d as p o s s i b l e by m e c h a n i c a l means b e f o r e t h e u r e a i s a p p l i e d . The a p p l i c a t i o n r a t e f o r d e - i c i n g i s u s u a l l y 90 k g . / 305 l i n e a l m e t e r s ( 200 l b . /1000 l i n e a l f e e t ) . U rea i s e f f e c t i v e i n a n t i - i c i n g and d e - i c i n g down t o - 1 1 ° C . U r e a need n o t be a p p l i e d t o pavement a b o v e 0 ° C . A hooded t h e r m o m e t e r p l a c e d on t h e p a v e m e n t s u r f a c e f o r s e v e r a l m i n u t e s i s commonly u sed t o m e a s u r e r unway t e m p e r a t u r e s . B e t w e e n - 7 and - 1 1 ° C , t h e u r e a i m p r e g n a t e d i c e may become s l u s h y . Unde r t h e s e c o n d i t i o n s , i m m e d i a t e r e m o v a l by s w e e p i n g i s n e c e s s a r y . T a b l e 3 l i s t s t h e q u a n t i t y o f u r e a u s ed d u r i n g t h e w i n t e r o f 1 9 7 5 - 1 9 7 6 on t h e a i r p o r t s o f B .C. 1.1 U r e a P e l l e t A c t i o n U r e a w o r k s by l o w e r i n g t h e f r e e z i n g p o i n t o f w a t e r ( o r t h e m e l t i n g p o i n t o f i c e ) . The r e l a t i o n s h i p b e t w e e n u r e a , i c e , and w a t e r i s shown i n an e u t e c t i c d i a g r a m , ( F i g u r e 1) w h i c h may be u s ed t o e x p l a i n t h e a c t i o n o f u r e a as an a n t i - i c e r . . " ' C o n s i d e r w a t e r t o w h i c h 10% o f u r e a by w e i g h t has been a d d e d . Such a s o l u t i o n a t 1°C i s r e p r e s e n t e d by A i n t h e d i a g r a m . The b e h a v i o u r o f t h e s o l u t i o n on c o o l i n g can be d e d u c e d by f o l l o w i n g t h e v e r t i c a l l i n e AB. So l o n g as t h e t e m p e r a t u r e does n o t f a l l b e l o w t h a t c o r r e s p o n d i n g t o C ( a b o u t - 3 ° C ) on t h e f r e e z i n g p o i n t c u r v e (WE) no f r e e z i n g can o c c u r a t a l l . As t h e t e m p e r a t u r e f a l l s t o t h a t c o r r e s p o n d i n g t o C, o r t o l o w e r t e m p e r a t u r e s , i c e can b e g i n t o f o r m ; b u t i n c o n t r a s t t o w a t e r a l o n e a u r e a s o l u t i o n does n o t f r e e z e c o m p l e t e l y . I n i t i a l l y some w a t e r f r e e z e s o u t T a b l e 3 Q u a n t i t i e s o f U r e a Used a t A i r p o r t s i n B .C . D u r i n g 1 9 7 5 - 7 6 A i r p o r t L o c a t i o n MOT a i r p o r t s : Q u a n t i t y o f U rea ( t o n n e s ) A b b o t s f o r d 10 Kami oop s 1 5 P e n t i c t o n 6 P i t t Meadows 5 P o r t H a r d y 41 P r i n c e G e o r g e 102 P r i n c e R u p e r t 61 Q u e s n e l 20 Sands p i t 41 S m i t h e r 5 10 T e r r a c e * 61 R i c h m o n d ( V I A ) 82 S i dn ey 26 Wi 11 i ams La-ke . 16 p a l a i r p o r t s : C a m p b e l l R i v e r 31 C a s t l e g a r 10 C r a n b r o o k 20 G r a n d F o r k s 1 P o w e l l R i v e r 1 Ke1owna 1 5 * Annual use of Urea a t Ter race A i r p o r t year Tonnes o f Urea 72/73 73/74 74/75 75/76 76/77 72 65 70 70 40 4 o o .0) s-+-> n3 <v c cu 0" w -2 • Urea S o l u t i o n -4 ( l i q u i d ) -6 1 F -8 J I c e + / Urea + -10 I Urea S o l u t i o n / Urea S o l u t i o n -12 ( s l u s h ) / ( s l u s h ) I c e * E u t e c t i c Urea + E u t e c t i c ( s o l i d ) ( s o l i d ) -14 'B -16 _ .. i 0 10 20 30 40 50 60 7 Urea % by we i g h t o f water Figure 1 Urea -Ice-Water Eutectic Di agram 7 10 l e a v i n g a r e s i d u a l s o l u t i o n r i c h e r i n u r e a and hence h a v i n g a s t i l l l o w e r f r e e z i n g p o i n t . I f t h e t e m p e r a t u r e i s f u r t h e r l o w e r e d more i c e w i l l f o r m , l e a v i n g a s m a l l e r q u a n t i t y o f a y e t r i c h e r s o l u t i o n o f l o w e r f r e e z i n g p o i n t a g a i n . In g e n e r a l , t h e r e -f o r e , : t h e u r e a s o l u t i o n o r i g i n a l l y r e p r e s e n t e d by A , when c o o l e d t o a t e m p e r a t u r e i n t h e ICE + UREA s o l u t i o n f i e l d , becomes a m i x t u r e o f i c e and a u r e a s o l u t i o n - w i t h more i c e a t i n c r e a s i n g l y l o w e r t e m p e r -a t u r e s . M o r e o v e r , t h e p r o p o r t i o n o f l i q u i d p r e s e n t i n t h e m i x t u r e i s g i v e n n e a r l y q u a n t i t a t i v e l y ( s i c . ) by t h e r a t i o FD x 100% w h i c h g i v e s a b o u t 38% a t - 7 ° C . FG T h i s p r i n c i p l e r e m a i n s v a l i d down t o t h e t e m p e r a t u r e o f - 1 1 . 5 ° C , t h e min imum f r e e z i n g p o i n t i n t h e u r e a -w a t e r s y s t e m ( p o i n t E ) . B e l o w t h e e u t e c t i c t e m p e r -a t u r e o f - 1 1 . 5 ° C u r e a - w a t e r s o l u t i o n s w i l l f r e e z e c o m p l e t e l y t o g i v e a m i x t u r e o f i c e and t h e s o l i d e u t e c t i c . " I c e and s o l i d u r e a c a n n o t e x i s t t o g e t h e r f o r l o n g a t t e m p e r a t u r e s a b o v e - 1 1 . 5 ° C . The d e - i c i n g a c t i o n o f u r e a depend s upon t h e l o c a l i n t e r a c t i o n o f i c e and u r e a a t t h e p o i n t o f 8 c o n t a c t and i s i l l u s t r a t e d by t h e e u t e c t i c d i a g r a m . " I f f o r e x a m p l e , s t a r t i n g w i t h i c e a t - 7 ° C ( p o i n t F on t h e d i a g r a m ) 10% o f u r e a ( b y w e i g h t o f i c e ) w e r e a d d e d , an i c e - u r e a m i x t u r e w i t h t h e a v e r a g e c o m p o s i t i o n r e p r e s e n t e d by D w o u l d be f o r m e d and t h e i c e w o u l d g e n e r a l l y l o o s e n and b r e a k up. To s e c u r e c o m p l e t e m e l t i n g , u r e a i n e x c e s s o f t h e q u a n t i t y r e p r e s e n t e d by G ( s a y 30%) w o u l d have t o be a d d e d . I f , l o c a l l y p e r h a p s , t h e c o n c e n t r a t i o n o f u r e a we re g r e a t e r t h a n t h a t r e p r e s e n t e d by t h e p o i n t H t h e n s o l i d u r e a w o u l d r e m a i n w i t h u r e a s o l u t i o n b u t a l l i c e w o u l d d i s a p p e a r . F r e q u e n t l y , c o m p l e t e m e l t -i n g i s n o t r e q u i r e d b u t o n l y s u f f i c i e n t l o o s e n i n g a c t i o n t o e n a b l e m e c h a n i c a l r e m o v a l t o be p r a c t i c -a b l e . " L e s s u r e a i s r e q u i r e d t o p r e v e n t t h e f o r m a t i o n o f i c e t h a n t o l o o s e n and b r e a k up- p r e v i o u s l y f o r m e d i c e . In d e -i c i n g , h e a t must be p r o v i d e d t o o v e r c o m e t h e l a t e n t h e a t o f i c e f u s i o n . A n t i - i c i n g i s , t h e r e f o r e , more e f f i c i e n t a t c o n t r o l l i n g i c e t h a n d e - i c i n g . 11 1.2 The E n v i r o n m e n t a l I m p a c t o f U rea 1.2.1 The P r o b l e m U r e a i s u s e d , among o t h e r t h i n g s , a s a f e r t i l i z e r . When a p p l i e d on s o i l i t s u p p l i e s n i t r o g e n n e e d e d by p l a n t s . When a p p l i e d on an a i r p o r t r unway f o r d e - i c i n g , t h i s u r e a -n i t r o g e n r e a c h e s t h e s o i l - w a t e r e n v i r o n m e n t a r o u n d t h e a i r p o r t . A t V a n c o u v e r I n t e r n a t i o n a l A i r p o r t ( V I A ) i n 1 9 7 5 , f o r e x a m p l e , o f t h e 81 t o n n e s o f u r e a u s e d , 38 t o n n e s o f n i t r o g e n were r e l e a s e d f r o m t h e d e - i c e r t o t h e e n v i r o n m e n t a d j a c e n t t o t h e r u n w a y . The i m p a c t t h a t t h i s n i t r o g e n has on t h e e n v i r o n m e n t , depend s upon t h e q u a n t i t y o f u r e a a p p l i e d and t h e c o n d i t i o n s o f t h e r e c e i v i n g s y s t e m . Each a i r p o r t has i t s own p o l l u t i o n p o t e n t i a l . G r o u n d and s u r f a c e w a t e r s c o n t a i n i n g e x c e s s i v e n i t r o g e n can l e a d t o s e v e r a l p r o b l e m s . In 1 9 4 0 , i t was f o u n d t h a t d r i n k i n g 9 w a t e r s w i t h h i g h n i t r a t e c a u s e d . m e t h e m o g l o b i n e m i a i n i n f a n t s . The maximum p e r m i s s i b l e d r i n k i n g w a t e r s t a n d a r d i n Canada i s 10.0 mg ,| 1 N i t r a t e + N i t r i t e as N 1 0 . The d i s c h a r g e o f ammonia n i t r o g e n and i t s s u b s e q u e n t o x i d a t i o n can s e r i o u s l y r e d u c e t h e d i s s o l v e d o x y g e n l e v e l s i n s u r f a c e and g r o u n d w a t e r . T h i s i s p a r t i c u l a r l y t r u e i n w a t e r s w h i c h do n o t have s i g n i f i c a n t a t m o s p h e r i c r e - o x y g e n a t i o n r a t e s . E u t r o p h i c a t i o n i s a s e r i o u s p r o b l e m p o s e d by e x c e s s i v e n i t r o g e n r e l e a s e t o l a k e s . I t i s o f p a r t i c u l a r c o n c e r n i n 12 some l a k e s i n t h e Okanagan r e g i o n o f B r i t i s h C o l u m b i a . Some l a k e s i n t h i s a r e a a r e r e c e i v i n g d r a i n a g e w a t e r s f r o m some a i r p o r t s whe re u r e a i s u s e d . E u t r o p h i c a t i o n i s t h e c o m p l e x s e q u e n c e o f c h a n g e s i n a q u a t i c e c o s y s t e m s c a u s e d by an i n c r e a s e d r a t e o f s u p p l y o f p l a n t n u t r i e n t s t o w a t e r . An e u t r o p h i c l a k e r e p r e s e n t s t h e end p r o d u c t o f t h i s s e q u e n c e . I t i s c h a r a c t e r -i z e d by a h i g h n u t r i e n t s u p p l y i n r e l a t i o n t o t h e vo l ume o f w a t e r . The l a k e may c o n t a i n d e n s e g r o w t h s o f p l a n k t o n i c g r e e n and b l u e -g r e e n a l g a e , mat s o f r o o t e d p l a n t s and f i l a m e n t o u s a l g a e on t h e b o t t o m o f s h a l l o w a r e a s , v e r y l ow o r no d i s s o l v e d o x y g e n i n t h e l o w e r d e p t h s i n summer, and d o m i n a n t w a r m w a t e r f i s h s p e c i e s (minnow and b a s s f a m i l i e s ) ^ . The p r o c e s s o f e u t r o p h i c a -t i o n o c c u r s n a t u r a l l y , b u t , m a n ' s a c t i v i t i e s can g r e a t l y a c c e l e r a t e i t . 1.22 U r e a N i t r o g e n P a t h w a y s G e n e r a l l y , a l l o f t h e u r e a - n i t r o g e n w h i c h i s a p p l i e d on an a i r p o r t r unway w i l l n o t c o n t a m i n a t e g r o u n d and s u r f a c e w a t e r s . N i t r o g e n can a s sume many f o r m s and f o l l o w many r e -a c t i o n p a t h w a y s , p a r t i c u l a r l y i n s o i l s ( F i g u r e 2 ) . T h e s e s o i l p a t h w a y s i n c l u d e u r e a h y d r o l y s i s , n i t r i f i c a t i o n , ammonia v o l a t i l i z a t i o n , d e n i t r i f i c a t i o n , p l a n t u p - t a k e and l e a c h i n g . S i n c e most o f t h e u r e a a p p l i e d t o a i r p o r t : runways e ven tua l l y con-t a c t s s o i l , i t i s i m p o r t a n t t o e x a m i n e t h e s o i 1 - n i t r o g e n r e -a c t i o n s . The mos t common way d e - i c e r u r e a can e n t e r i n t o t h e s o i l s y s t e m i s by p e r c o l a t i o n . C u r r e n t l y , u r e a i m p r e g n a t e d snow i s N I T R O G E N FORMS + w Urea Q NH -NH. 3 4 © N0'3~ N 2 gas 0 NH 3 gas Figure 2 Possible Urea De-ice Nitrogen Pathways PATHWAYS 1 Urec. runoff 2 Urea seepage 3 Urea Hydrolysis (Urea—*NH3-*NH4 ) 4NH3 v o l a t i l i z a t i o n 5 NH 4 + clay f i x a t i o n ° N H 4 plant uptake 7 N i t r i f i c a t i o n ( N H 3 - — N 0 2 — N O 3 ) 8N0 3 plant uptake 9 D e n i t r i f i c a t i o n ( N f 3 - ^ 2 (g) ) 10N03 leaching ltUrea leaching '^Urea overland flow 14 b l o w n i n t o w i n d r o w s p a r a l l e l t o a i r p o r t r u n w a y s up t o 100 f t f r o m t h e pa vemen t s u r f a c e . Once t h e u r e a goes i n t o t h e s o i l , i t e n t e r s i n t o a c h a i n o f c o m p l e x r e a c t i o n s w h i c h may e v e n t u a l l y l e a d t o n i t r o g e n f o r m s b e i n g l e a c h e d t o s u r f a c e w a t e r s . The q u a n t i t y o f n i t r o g e n l e a c h e d i s d e t e r m i n e d by t h e p h y s i c a l , c h e m i c a l , and b i o l o g i c a l p r o p e r t i e s o f t h e s o i l and p l a n t s w h i c h c o n t r o l t h e n i t r o g e n r e a c t i o n s . a) U r e a H y d r o l y s i s U r e a can be h y d r o l y z e d t o ammonia by t h e s o i l enzyme u r e a s e . F o r m a t i o n o f u n s t a b l e ammonium c a r b o n a t e i s an i n t e r m e d i a t e s t e p i n t h e r e a c t i o n . C 0 ( N H 2 ) 2 + 2 H 2 0 — • ( N H 4 ) 2 C 0 3 — • 2 N H 3 + H 2 C 0 3 ( 2 - 1 ) U r e a U r e a s e T h i s h y d r o l y s i s r e s u l t s i n a t e m p o r a r y i n c r e a s e i n p H , o f w h i c h m a g n i t u d e and d u r a t i o n i s d e p e n d e n t upon s o i l b u f f e r i n g c a p a c i t y . U r e a s e i s a common s o i l enzyme and o f t e n e x i s t s as " f r e e u r e a s e " a b s o r b e d on c l a y m i n e r a l s . P a u l s o n and 1 p K u r t z showed t h a t f r e e u r e a s e c o m p l e x e d by s o i l c o l l o i d s was p r i m a r i l y r e s p o n s i b l e f o r t h e h y d r o l y t i c b r e a k d o w n o f u r e a . A l e x a n d e r ^ 3 f o u n d t h a t u r e a s e was s i g n i f i c a n t l y a c t i v e f r o m 2°C t o 3 7 ° C . B r e m n e r ^ showed t h a t u r e a s e i n d u c e d u r e a h y d r o l y s i s can o c c u r a t b e l o w f r e e z i n g t e m -1 C p e r a t u r e s as l ow as - 1 0 ° C t o - 2 0 ° C . B e a t o n 1 3 c o n c l u d e d : " T h i s e v i d e n c e o f u r e a s e a c t i v i t y a t l o w t e m p e r a t u r e s a l o n g w i t h 15 t h e k n o w l e d g e o f u r e a ' s a b i l i t y t o m e l t i c e a t t e m p e r a -t u r e s down t o 1 1 ° F ( - 1 2 ° C ) s u g g e s t e s t h a t u r e a a p p l i e d l a t e i n t h e f a l l o r e ven u n d e r w i n t e r c o n d i t i o n s w i11 be c o n -v e r t e d t o ammon ium. " S i m p s o n and M e l s t e d ^ f o u n d u r e a h y d r o l y s i s r a t e s t o be 2 t o 6 t i m e s g r e a t e r a t 25°C t h a n a t 1°C . G a s s e r 1 7 f o u n d t h a t , a t 5 ° C , h y d r o l y s i s was s l o w and was c o m p l e t e a f t e r 16 day s i n s o i l w h i c h had been p r e v i o u s l y m a n u r e d ; and o n l y a b o u t 40% was h y d r o l y z e d a f t e r 1.8 days i n u n -manured s o i l . C o m p l e t e h y d r o l y s i s r e q u i r e d 6 -7 weeks a t 5°C and a b o u t 3 weeks a t 25°C f o r unmanured s o i l s . He c o n c l u d e d t h a t u r e a may r e m a i n u n c h a n g e d f o r c o n s i d e r a b l e p e r i o d s when a p p l i e d t o o l d a r a b l e s o i l s c o n t a i n i n g s m a l l amoun t s o f o r g a n i c m a t t e r , e s p e c i a l l y i n t h e s p r i n g when t h e s o i l i s c o o l . S i m p s o n and M e l s t e d f o u n d t e m p e r a t u r e t o be t h e mos t i m p o r t a n t s o i l f a c t o r a f f e c t i n g u r e a h y d r o l y s i s r a t e s , f o l l o w e d by pH and s o i l t y p e . S o i l m o i s t u r e and u r e a c o n c e n t r a t i o n were f o u n d t o be o f much l e s s i m p o r -t a n c e . A f t e r an 8 week p e r i o d a t 1 ° C , up t o 100% o f t h e n i t r o g e n added as u r e a was r e c o v e r e d as e x c h a n g e -a b l e ammonium. The min imum h y d r o l y s i s r a t e i n h i g h e r pH s o i l ; ( 6 . 2 p H ) a t 1°C was f o u n d t o be 30 pounds o f u r e a - N p e r a c r e per. day h y d r o l y z e d , and i n l o w e r pH s o i l s ( 5 . 1 p H ) 10 pounds of* u r e a - N p e r a c r e h y d r o l y z d d p e r d a y . G a s s e r ^ f o u n d t h a t a t 5 ° C , h y d r o l y s i s o f u r e a was s l o w and was c o m p l e t e a f t e r 18 day s i n t h e manu red s o i l ; o n l y a b o u t 40 p e r c e n t was h y d r o l y z e d a f t e r 18 d a y s t h e unman u r e d s o i l , as shown i n Table 4. T a b l e 4 N i ' t r o g e n R e c o v e r e d f r o m C l a y So i I s + * Days N H 4 -N * N 0 3 -N U r e a - N * T o t a l * - Unmanured -0 1 0 91 92 (P 5°C 4 . 6 0 86 92 8 14 1 84 99 12 23 1 67 91 18 35 1 62 98 @ 25°C 3 15 1 78 94 6 33 3 52 88 10 52 10 26 88 14 58 24 10 92 - F a r m y a r d manure -0 3 0 89 92 @ 5°C 4 22 1 70 93 8 50 3 40 93 12 64 4 21 89 18 82 7 0 89 3 57 7 26 90 6 69 21 0 90 10 52 39 0 91 14 43 48 3 94 * ( N i t r o g e n r e c o v e r e d , as p e r c e n t o f N a p p l i e d d u r i n g d e c o m p o s i t i o n o f u r e a s u p p l y i n g 100 l b . o f N / a c r e t o two c l a y s o i l s ) . S o i l u r e a s e a c t i v i t y i s g e n e r a l l y r e l a t e d t o 1 7, 1 g t h e number o f u r e o l i t i c m i c r o - o r g a n i s m s p r e s e n t b) N i t r i f i c a t i o n Ammonia p r o d u c e d by t h e h y d r o l y s i s o f u r e a i s c o n v e r t e d t o n i t r a t e (NO^ " ) by a g r o u p o f s o i l o r g a n i s m s c a l l e d n i t r i f i e r s . The N i t r o s o m o n a s g r o u p o f b a c t e r i a c o n v e r t t h e ammonia u n d e r a e r o b i c c o n d i t i o n s t o n i t r i t e ( N O ^ - ) as shown i n e q u a t i o n 2 - 2 . 2 N H 3 + 3 0 2 —>- 2 N 0 2 " + 2 H + + 2 H 2 0 ( 2 - 2 ) The N i t r o b a c t e r g r o u p c o n v e r t t h e n i t r i t e t o n i t r a t e shown i n e q u a t i o n 2 - 3 . 2 N 0 2 " + 0 2 — - 2 N 0 3 _ ( 2 " 3 ) In mos t s o i l s , t h e s e c o n d s t e p o f t h e r e a c t i o n i n v o l v i n g t h e N i t r o b a c t e r g r o u p i s more r a p i d t h e n t h e f i r s t s t e p , t h e r e f o r e N 0 2 ~ i s u s u a l l y f o u n d i n l i m i t e d q u a n t i t i e s . G e n e r a l l y s p e a k i n g e n v i r o n m e n t a l f a c t o r s f a v o u r i n g c r o p g r o w t h f a v o u r n i t r i f i c a t i o n . The se s o i l e n v i r o n m e n t a l f a c t o r s i n c l u d e : n i t r i f y i n g o r g a n i s m p o p u l a t i o n , r e a c t i o n , 1 5 a e r a t i o n , m o i s t u r e c o n t e n t , and t e m p e r a t u r e . The o p t i m u m s o i l pH f a v o u r i n g n i t r i f i c a t i o n i s b e t w e e n 6.5 and 7 .8 . N e g l i g i b l e n i t r i f i c a t i o n o c c u r s i n s o i l s w i t h a pH b e l o w 5 . 0 . N i t r i f i c a t i o n p r o c e e d s a t a m e a s u r e a b l e r a t e a t any t e m p e r a t u r e above f r e e z i n g , a l t h o u g h t h e r a t e v a r i e s c o n s i d e r a b l y . N i t r i f i c a t i o n p r o c e e d s o n l y o n e - h a l f as 18 r a p i d l y a t 10°C as a t 15°C and o n l y o n e - t e n t h as r a p i d l y 1 p a t 5 ° C . The o p t i m u m r a n g e i s 32 t o 35°C . 1 p S i m p s o n and Me I s t e d " w o r k i n g w i t h t h e i r I l l i n o i s s o i l s a t 1 ° C , f o u n d no m e a s u r e a b l e q u a n t i t i e s o f n i t r a t e s i n any o f t h e s o i l s a f t e r an 8 ,week p e r i o d . A t 2 5 ° C , t h e y f o u n d t h a t c o m p l e t e n i t r i f i c a t i o n had o c c u r r e d i n 3 o u t o f 4 . h i g h pH ( 6 . 1 ) s o i l s . N i t r i f i c a t i o n a f t e r 8 weeks r a n g e d f r o m 25 t o 50% o f t h e a p p l i e d u r e a - N a t 25°C f o r t h e 4 l o w pH s o i l s . W e l l a e r a t e d s o i l s a r e r e q u i r e d t o s u p p o r t n i t r i f i c a t i o n s i n c e o x y g e n i s n e e d e d i n t h e p r o c e s s . C o a r s e t e x t u r e d s o i l s w i t h good s t r u c t u r e a r e c o n d u c i v e t o n i t r i f i c a t i o n , w h e r e a s , p o o r l y d r a i n e d s o i l s a r e n o t . U r e a a p p l i e d n i t r o g e n c an be l o s t i n two ways t o t h e a t m o s p h e r e , t h r o u g h ammonia v o l a t i l i z a t i o n and den i t r i f i c a t i o n . c ) Ammonia V o l a t i l i z a t i o n F o r ammonia v o l a t i l i z a t i o n t o o c c u r , t h e u r e a must f i r s t be h y d r o l y z e d ( E q ' n 2 - 1 ) , and t h e r a t e o f v o l a t i l i z a t i o n , t h e r e f o r e , i s g o v e r n e d by t h e r a t e o f u r e a h y d r o l y s i s . V o l a t i l i z a t i o n i s r e p r e s e n t e d by E q u a t i o n 2 - 4 . N H 3 ( 1 ) — N H 3 ( g ) ( 2 - 4 ) Ammonia v o l a t i l i z a t i o n o c c u r s when t h e a b s o r p -t i o n c a p a c i t y o f t h e s o i l i s i n s u f f i c i e n t t o h o l d t h e ammon i a . Ammomia v o l a t i 1 i z a t i o n i n c r e a s e s w i t h : h i g h 19 s o i l pH , c a l c i u m c a r b o n a t e i n s o i l , l ow o r g a n i c m a t t e r and c l a y c o n t e n t , h i g h u r e a s e a c t i v i t y , l o w n i t r i f i c a t i o n c a p a c i t y , a i r movement o v e r s o i l s u r f a c e , h i g h u r e a a p p l i c a t i o n r a t e s , h i g h s o i l t e m p e r a t u r e s , and r a p i d d r y -i n g o f t h e s o i l s due t o e v a p o r a t i o n . V o l a t i l i z a t i o n l o s s e s f r o m s u r f a c e a p p l i e d u r e a have been r e p o r t e d t o o c c u r e ven on a c i d s o i l s . T h i s o c c u r s b e c a u s e o f l o c a l i z e d a r e a s o f a l k a l i n i t y 1 '5 a r o u n d t h e u r e a p e l l e t s c a u s e d by t h e h y d r o l y s i s o f u r e a Ammonia l o s s e s f r o m f o r e s t s o i l s have r a n g e d f r o m l e s s t h a n 5 p e r c e n t t o 2 0 - 4 0 p e r c e n t o f t h e a p p l i e d 19 u r e a 20 M a h e n d r a p p a w o r k i n g w i t h some f o r e s t f l o o r m a t e r i a l s f o l l o w i n g u r e a f e r t i l i z a t i o n f o u n d t h a t , d e p e n d i n g upon t h e s o u r c e o f o r g a n i c m a t t e r , t h e maximum r a t e o f ammonia v o l a t i l i z a t i o n o c c u r r e d on t h e s e c o n d o r t h i r d d a y . The q u a n t i t y o f ammonia v o l a t i l i z e d w i t h i n a week o f u r e a a p p l i c a t i o n c o n s t i t u t e d t h e . m a j o r p r o p o r t i o n o f t h e t o t a l q u a n t i t y o f ammonia g i v e n o f f i n 42 t o 56 d a y s . The r a t e o f ammonia v o l a t i l i z a t i o n f r o m f e r t i 1 i z e d f o r e s t f l o o r s was f o u n d t o be d e p e n d e n t on t h e c o n c e n t r a t i o n g r a d i e n t o f t h e u r e a i n s o l u t i o n a r o u n d t h e s i t e s whe re t h e enzyme u r e a s e h y d r o l y z e s u r e a t o ammon i a . L a r g e u r e a p a r t i c l e s w o u l d c a u s e g r e a t e r g a s e o u s l o s s , o f ammonia s i n c e l a r g e r c o n c e n t r a t i o n g r a d i e n t s w o u l d d e v e l o p . How-e v e r , t h e l a r g e r p a r t i c l e , w i t h l o w e r s u r f a c e a r e a ( b y 20' w e i g h t ) , may c o n t a c t l e s s u r e a s e . P r e v i o u s u r e a a p p l i c a t i o n s have been f o u n d t o i n c r e a s e ammonia v o l a t i l i z a t i o n o f s u b s e q u e n t u r e a a d d i -21 t i o n s . T h i s may have o c c u r r e d b e c a u s e p r e v i o u s n u t r i e n t a p p l i c a t i o n i n c r e a s e d t h e number and a c t i v i t y o f u r e o l y t i c and o t h e r s o i l m i c r o - o r g a n i s m s , which in turn;.caused an/increased h y d r o l y s i s o f u r e a t o ammon i a . A s h i f t i n t h e N H ^ / N H ^ e q u i l i b r i u m i n t h e d i r e c t i o n o f i n c r e a s e d NH^ c o n c e n t r a -t i o n and s u b s e q u e n t v o l a t i l i z a t i o n c o u l d a l s o have o c c u r r e d . P r i o r f e r t i l i z a t i o n (4 y e a r s b e f o r e ) was f o u n d t o n e a r l y d o u b l e ammonia v o l a t i 1 i z a t i o n . 1 o s s e s . G l a c i a l o u t w a s h s o i l had t h e l o w e s t ammonia v o l a t i l i z a t i o n o f a l l s o i l s t e s t e d ( 9 . 8 % ) p o s s i b l y b e c a u s e o f i t s l ow pH ( 4 . 6 ) and l ow m i c r o b i a l a c t i v i t y . As shown i n - T a b l e v o l a t i l i z a t i o n l o s s o f 22 ammonia has been shown t o be m i n i m a l a t l ow t e m p e r a t u r e s T a b l e 5 V o l a t i 1 i z a t i o n o f Ammonia i n S o i l s S o i l Type S o i l pH T e m p e r a t u r e 7°C 16°C 2 2 ° C L a k e l and f . s. 1 5.6 1 . 1 * 7-1 41 . 1 L a k e l a n d f . s. 111 5.4 1.1 9 .2 1 5 . 7 L a k e l a n d f . s. V 6 .3 5.1 32 . 9 36 . 9 Leon : f . s . •I 4 . 4 0 . 4 1 6 . 3 26 . 7 Leon f . s. I I 5. 9 8;:3 2 7 . 2 36. 0 ( 100 pounds o f u r e a - n i t r o g e n t o b a r e m o i s t s o i l s ) . * % l o s s i n 7 d a y s . 21 In t h e s e e x p e r i m e n t s , V o l k ^ " 1 n o t e d t h a t s l o w i n g t h e r a t e o f c o n v e r s i o n o f u r e a t o ammonia w o u l d i n c r e a s e t h e p e r i o d d u r i n g w h i c h p r e c i p i t a t i o n c o u l d r e d u c e v o l a t i l e l o s s o f ammonia by w a s h i n g any r e s i d u a l u r e a i n t o t h e s o i l . G a s s e r e x p e r i m e n t e d w i t h 4 s o i l s a t 5°C and 25°C as shown i n T a b l e 6. T a b l e 6 V o l a t i l i z a t i o n o f Ammonia i n Loams Temp S o " 1* 1 2 3 4 @ 5°C ( a f t e r 18 d a y s ) 0 . 4 * * 2 .2 19 . 6 7 .3 @ 25°C ( a f t e r 14 d a y s ) 2 .2 2 .2 1 0 . 3 5.4 * ( s o i l s 1 and 2 we re c l a y l o a m s , 3 and 4 we re s a n d y 1 o a m s ) . * * N H 3 l o s t as % N a p p l i e d (100 l b o f U r e a - N / A c r e ) Sandy l o a m s e x h i b i t e d h i g h e r v o l a t i l i z a t i o n r a t e s t h a n c l a y l o a m s . d) D e n i t r i f i c a t i o n The s e c o n d way i n w h i c h u r e a n i t r o g e n may be l o s t t o t h e a t m o s p h e r e i s t h r o u g h d e n i t r i f i c a t i o n . T h i s i s a m i c r o b i a l p r o c e s s w h i c h c o n v e r t s n i t r a t e o r n i t r i t e t o n i t r o g e n gas as shown i n Equation 2-5. 22 N 0 3 + H + « r l / 2 N 2 + 5/4 0 2 + 1/2 H 2 0 ( 2 - 5 ) F o r d e n i t r i f i c a t i o n t o t a k e p l a c e , t h e r e must be no o x y g e n i n t h e m i c r o e n v i r o n m e n t o f t h e b a c t e r i a , and a v a i l a b l e o r g a n i c m a t t e r f o r e n e r g y . F o r t h i s r e a s o n , d e n i t r i f i c a t i o n i s most l i k e l y t o o c c u r i n w a t e r l o g g e d s o i l s w i t h l a r g e q u a n t i t i e s o f f r e s h o r r e a d i l y d e c o m p o s a b l e c r o p r e s i d u e s . H i g h t e m p e r a t u r e s and n e u t r a l t o a l k a l i n e s o i l c o n d i t i o n s a l s o f a v o u r d e n i t r i f i c a t i o n . A l l o f t h e s e c o n d i t i o n s e x i s t i n many s o i l s o f w e s t e r n C a n a d a , and as a r e s u l t , t h e r e c o u l d be s u b s t a n t i a l l o s s e s o f s o i l and f e r t i l i z e r 15 n i t r o g e n , e s p e c i a l l y d u r i n g warm s p e l l s i n May and J une The D e p a r t m e n t o f S o i l S c i e n c e a t t h e U n i v e r -s i t y o f S a s k a t c h e w a n e s t i m a t e d t h a t d e n i t r i f i c a t i o n a c c o u n t s f o r T o s s e s o f 1 0 - 30 p e r c e n t o f t h e a v a i l a b l e s o i l n i t r o g e n . O t h e r " s t u d i e s have shown t h a t 10 t o 20 p e r c e n t o f t h e a p p l i e d f e r t i 1 i z e r n i t r o g e n c o u l d be l o s t t h r o u g h d e n i t r i -24' 2 5 f i c a t i o n . D e B e l l (e_t a j . ) f o u n d g a s e o u s l o s s e s o f n i t r o -gen o x i d e s f r o m t h r e e f o r e s t s o i l s t o be o f l o w m a g n i t u d e ( l e s s t h a n 1%). e ) P l a n t U p t a k e P l a n t s can u t i l i z e n i t r o g e n i n v a r i o u s f o r m s , h o w e v e r , n i t r a t e and ammonium a r e t h e f o r m s most commonly u s e d . Mos t a g r i c u l t u r a l c r o p s p r e f e r n i t r a t e . N i t r a t e i s more l i k e l y t o be f r e e i n t h e r o o t z one as i t i s h i g h l y m o b i l e . O p t i m a l p l a n t y i e l d r e q u i r e s an e x c e s s o f n i t r a t e n i t r o g e n i n t h e s o i l . C a r e must be t a k e n s i n c e e x c e s s i v e 23 q u a n t i t i e s o f n i t r o g e n can e x t e n d g r o w i n g p e r i o d s and d e l a y c r o p m a t u r i t y . N i t r a t e i s n o t a c c u m u l a t e d u n i f o r m l y by t he . v a r i o u s t i s s u e s and o r g a n s o f p l a n t s . T h e r e a r e many e n v i r o n m e n t a l f a c t o r s w h i c h i n f l u e n c e n i t r a t e a c c u m u l a t i o n a n d , t h e r e f o r e , e x t r e m e v a r i a t i o n s a r e f o u n d i n n i t r a t e 2 6 c o n t e n t i n t h e same t i s s u e f r o m p l a n t t o p l a n t On t h e a v e r a g e , a b o u t 50% o f t h e a p p l i e d 24 f e r t i l i z e r n i t r o g e n i s r e c o v e r e d by u p l a n d c r o p s . The p l a n t f a m i l i e s : Amaran t h a c e a e , C h e m o p o d i a c e a e , C r u c i f e r a e , C o m p o s i t a e , G r a m i n e a e , and S o l a n a c e a e have been shown t o a c c u m u l a t e h i g h l e v e l s o f n i t r a t e . N i t r a t e doe s n o t a c c u m u l a t e u n i f o r m i l y t h r o u g h 2 7 t h e g r o w i n g p e r i o d o f a p l a n t . " I n summary , e x p e r i m e n t s w i t h s e v e r a l c e r e a l p l a n t s p e c i e s u n d e r ' n o r m a l c o n d i t i o n s ' i n d i c a t e t h a t i n t h e e a r l y v e g e t a t i v e s t a g e s , t h e l e a f t i s s u e can a c c u m u l a t e n i t r a t e i n r e l a t i v e l y h i g h c o n c e n t r a t i o n s ( 400 t o 1500 N 0 3 ~ - N g . f r e s h w e i g h t " 1 ) . T h i s i n i t i a l a c c u m u l a t i o n , u n d e r n o r m a l c o n d i t i o n s , i s a t -t r i b u t a b l e t o a v a i l a b l e w a t e r and n i t r a t e i n t h e s o i l t h a t f a v o u r s h i g h r a t e s o f a b s o r p t i o n . T h u s , i n t h e e a r l y s t a g e s o f d e v e l o p m e n t , a b s o r p t i o n and t r a n s -l o c a t i o n e x c e e d s t h e c a p a c i t y f o r n i t r a t e r e d u c t i o n and. a s s i m i l a t i o n . As t h e p l a n t d e v e l o p s t h e c o n -c e n t r a t i o n o f n i t r a t e d e c r e a s e s i n b o t h l e a f y and n o n -l e a f y t i s s u e , w i t h t h e more r a p i d d e c r e a s e o c c u r r i n g i n t h e l e a f t i s s u e . The d e c r e a s e i n n i t r a t e c o n t e n t i s a t t r i b u t a b l e t o t h e f o l l o w i n g s e v e r a l f a c t o r s : a) R a p i d g r o w t h t e n d s t o d i l u t e t h e n i t r a t e c o n -c e n t r a t i o n ; b) t h e c a p a c i t y o f t h e l e a f t i s s u e t o r e d u c e and a s s i m i l a t e n i t r a t e i s i n c r e a s e d n o t o n l y f r o m h a v i n g a g r e a t e r amount o f t h e p r o p e r enzymes b u t h a v i n g an a d e q u a t e s u p p l y o f e n e r g y f o r t h e r e d u c t i v e s t e p s ; and c) a r e d u c t i o n i n a v a i l a b l e w a t e r and n i t r a t e i n t h e s o i l . In m a t u r e p l a n t s n i t r a t e a c c u m u l a t e s p r i m a r i l y i n t i s s u e t h a t e x h i b i t s a l ow c a p a c i t y f o r r e d u c t i o n and a s s i m i l a t i o n v 24 ( m o n c h i o r o p h y l 1 us s t em and s t a l k s t r u c t u r e s ) . From s t u d i e s w i t h weeds and s o y b e a n s ( W e l l s u n -p u b l i s h e d w o r k ) , i t a p p e a r s t h a t o t h e r p l a n t s e x h i b i t a s i m i l a r p a t t e r n o f n i t r a t e a c c u m u l a -t i o n . " The n i t r o g e n c o n t e n t o f mos t c r o p p l a n t s i s 1 f r o m 1 t o 3% o f t h e d r y w e i g h t ' . V i g o r o u s g r o w t h and a deep g r e e n c o l o u r a r e n o r m a l l y r e l a t e d t o an a d e q u a t e s u p p l y o f n i t r o g e n . Data on -p lant uptake of n i t rogef l has been p u b l i s h -ed by v a r i o u s a u t h o r s , as shown i n T a b l e 7. T a b l e 7 P l a n t U p t a k e o f N i t r o g e n 1 b N / A c r e * S o u r c e 1 b N / A c r e i n H a r v e s t e d C r o p C r op 480 U r e a 223 P e n s a c o l a B a h i a g r o s s 480 U r e a 261 Pan go 1 a g r a s s 480 U r e a 1 37 C a r p e t g r a s s 480 U r e a 280 C o a s t a 1 B e r m u d a g r a s s * ( U r e a a p p l i e d m o n t h l y 2 8 immedi a t e l y . ) s i x p o r t i o n s and w a t e r e d - j n 25 Table 7 - Cont inued: Crop Y i e l d (BU/A) Nitrogen Grain or Seed Removed by Cropping- lb/Acre A l l of the above ground growth ( g ra in or seed plus s t raw, s t o ve r , e t c . ) Wheat 40 58 76 Ba r l ey 60 57 90 Oats 80 49 81 Rapeseed 35 70 115 Grass (Hay) , 3 120 Corn (Gra in) 100 90 157 Corn(S i lage) 15 136 A l f a l f a (Hay)* 4 240* *Most o f the n i t rogen removed by e f f e c t i v e l y nodulated a l f a l f a i s 1*5 f i x e d from the atmosphere . r 26 Crop Y i e l d Pounds N i t rogen i n Tota l cwt/Acre P l an t Wheat 24 85 Ba r l ey 28.8 90 Oats 27.2 100 F lax 11.2 54 Rapeseed 15 119 Grass 60 86 A l f a l f a 80 248 Peas 18 118 Corn 120 139 Potatoes 300 225 Sugar Beets 300 160 26 An i n c r e a s e i n t e m p e r a t u r e f r o m 5 ° C " t o 35°C has been n o t e d t o c a u s e an i n c r e a s e i n t h e r a t e o f n i t r a t e a b s o r p t i o n o f p e r e n n i a l r y e g r a s s r o o t s , w i t h t h e g r e a t e s t 2 6 i n c r e a s e o c c u r r i n g b e t w e e n 15°C and 25°C 2 9 B r o a d b e n t " c o n c l u d e d t h a t u p t a k e o f n i t r o g e n by p l a n t s i s r e t a r d e d a t l ow t e m p e r a t u r e s and w i n t e r l o s s e s o f n i t r o g e n a r e h i g h e r t h a n i n summer, e ven on p e r m a n e n t p a s t u r e s . In O n t a r i o , 40 l b . o f n i t r o g e n t o p d r e s s e d on f a l l w h e a t i n e a r l y s p r i n g gave a y i e l d i n c r e a s e o v e r n o n - f e r t i l i z e d w h e a t e q u i v a l e n t t o 80 l b o f n i t r o g e n t o p 30 d r e s s e d i n t h e l a t e f a l l A p r a c t i c a l f a c t o r w h i c h w i l l i n f l u e n c e u r e a n i t r o g e n - s o i l i n t e r a c t i o n i s t h e MOT r e g u l a t i o n s r e -g a r d i n g c r o p s n e a r a i r p o r t s . MOT r e g u l a t i o n s r e s t r i c t c r o p s w h i c h may be grown a d j a c e n t t o a i r p o r t r u n w a y s . T h i s i s done t o m i n i m i z e t h e p o s s i b i l i t y o f b i r d s a c t i n g as a h a z a r d t o a i r c r a f t . I n f i e l d g r a s s a r e a s a r e r e q u i r e d t o be f r e e o f weeds and have a he igh t b e t w e e n 5 and 8 i n c h e s to r e s t r i c t a c c e s s i b i 1 i t y of b i r d s to worms T b e e t l e s i n s e c t s , e t c . i n the cover crop • C e r e a l g r a i n s and m a r k e t g a r d e n c r o p s a r e n o t p e r m i t t e d w i t h i n 1200 f e e t o f r u n w a y s . Where p r e s e n t , t h e s e c r o p s s h o u l d be r e p l a c e d w i t h h a y , a l f a l f a , o r f l a x w h i c h r e q u i r e l i t t l e o r no p l o w i n g o r c u l t i v a t i n g and a t t r a c t f ew b i r d s . C o r n , o a t s , and s u n f l o w e r s a r e p r o h i b i t e d v o n . a i r p o r t p r o p e r t y . A r e a s f u r t h e r t h a n 1200 f e e t f r o m t h e r unway s may be l e a s e d f o r a g r i c u l t u r a l 27 u se s i n t h e f o l l o w i n g o r d e r o f p r e f e r e n c e : a) Hay b) A l f a l f a c} F l a x d) S o y b e a n s e) P a s t u r e , G o l f C o u r s e s ) D r i v i n g R a n g e s , ) O n l y i f f u l l y s e c u r e A r c h e r y Ranges ) f e n c i n g i s p r o v i d e d . O t h e r human r e c r e a t i o n ) f ) F a l l r y e g) F a l l w h e a t h) S p r i n g Wheat i ) B a r l e y j ) O t h e r c e r e a l . g r a i n s and c r o p s e x c e p t c o r n and o a t s . f ) L e a c h i n g The m o b i l i t y o f ammonium and n i t r a t e i o n s i n s o i l d i f f e r s m a r k e d l y . Ammonium i o n may be r e t a i n e d : i n an e x c h a n g e a b l e f o r m on o r n e a r t h e s o i l , s u r f a ce . Expanding l a t t i c e c l a y m i n e r a l s s u c h as . m o n t m o r i 1 1 o n i t e , i l l i t e , and v e r m i c u l i t e p e r m i t N H ^ + t o e n t e r t h e c l a y s t r u c t u r e and become f i x e d . A l a r g e p r o p o r t i o n o f f i x e d ammonium can be h e l d w i t h i n t h e l a t t i c e o f t h e s e c l a y s and w i l l be u n a v a i l a b l e t o c r o p s and f o r t r a n s f o r m a t i o n by n i t r i f i e r s . In t h i s c a s e , ammonium i s o n l y f r e e l y m o b i l e when a s o i l s y s t e m i s t e m p o r a r i l y o v e r l o a d e d o r i n a s o i l w i t h l ow c a t i o n - e x c h a n g e c a p a c i t y . V a r i o u s w o r k e r s have shown t h a t a t n e u t r a l o r s i i g h t l y a c i d s o i l c o n d i t i o n s , o r g a n i c m a t t e r f i x e s l i t t l e o r no a m m o n i a , b u t , , a t pH l e v e l s 9 o r 1 0 , f i x a t i o n i n c r e a s e s r a p i d l y . " The a v a i l a b l e e v i d e n c e i n d i c a t e s t h a t i n t h e zone o f h i g h c o n c e n t r a t i o n , t h e amount o f ;i ammonium f i x e d by c l a y s and o r g a n i c m a t t e r i s g e n -e r a l l y l o w i n r e l a t i o n t o t h e amount a p p l i e d . I n -c r e a s e d m i n e r a l i z a t i o n o f s o i l n i t r o g e n r e s u l t i n g 28 f r o m t h e i n c r e a s e i n pH a p p a r e n t l y c o m p e n s a t e s f o r r e d u c e d c r o p u p t a k e o f NH - n i t r o g e n c a u s e d by f i x a t i o n " - 3 1 _ 6 N i t r a t e , on t h e o t h e r h a n d , i s h i g h l y m o b i l e i n s o i l . N i t r a t e d i f f u s e s v e r y s l o w l y w i t h o u t a p p r e c i a b l e w a t e r movement . W a t e r i n s o i l i s a s t o r a g e medium f o r n i t r a t e . N i t r a t e may move f a s t e r , s l o w e r , o r a t t h e same r a t e as t h e a v e r a g e t o t a l w a t e r i n t h e s o i l . I f t h e w a t e r moves upward b e c a u s e o f l a c k o f r a i n and h i g h e v a p o r a t i o n , n i t r a t e can a c c u m u l a t e a t t h e s o i l s u r f a c e as an e v a p o r i t e c r u s t . N i t r a t e i n t h e u p p e r p a r t o f t h e s o i l i s u t i l i z e d more by p l a n t s t h a n d e e p e r n i t r a t e b e c a u s e o f g r e a t e r p l a n t r o o t a c t i v i t y - N i t r a t e c o n c e n t r a t i o n s i n t h e r o o t z o n e a r e e x t r e m e l y v a r i a b l e d e p e n d i n g on t h e t i m i n g o f s a m p l i n g i n r e l a t i o n t o t h e 1 a s t f e r t i 1 i z a t i o n , c r o p g r o w t h , and r a i n f a l l o r i r r i g a t i o n . L i t t l e n i t r a t e a p p e a r s t o be l e a c h e d i n t h e p r e s e n c e o f a g r o w i n g c r o p . T h i s o c c u r s b e c a u s e o f r a p i d u p t a k e o f n i t r a t e i o n s by p l a n t s and r e d u c e d movement o f f r e e w a t e r due t o t h e r e m o v a l o f w a t e r by p l a n t s . F o r n i t r a t e t o move b e l o w t h e r o o t z o n e , t h e r e must be n i t r a t e p r e s e n t and downward w a t e r movement . N i t r a t e may r e a c h t h e w a t e r t a b l e i n a f ew h o u r s and be l o s t f r o m t h e p l a n t r o o t i n g z o n e . N i t r a t e b e l o w t h e r o o t zone and above an a q u i f e r i s g e n e r a l l y c h e m i c a l l y s t a b l e b e c a u s e o f an i n s u f f i c i e n t s u p p l y o f o x i d i z a b l e c a r b o n f o r t h e d e n i t r i f i e r s and no s i g n i f i c a n t s o u r c e o f ammonium f o r t h e n i t r i f i e r s . 29 Thomas 0 * 1 r e p o r t s t h a t i n v e r y d r y s o i l s , t o w h i c h w a t e r has been a d d e d , n i t r a t e may l a g b e h i n d t h e w a t e r f r o n t . In m o i s t s o i l s , h e a v y r a i n s c a u s e t h e n i t r a t e and w a t e r f r o n t t o move a t t h e same r a t e . L e a c h i n g l o s s e s o f up to 10 p e r c e n t o f t h e 1 g a v a i l a b l e n i t r o g e n P r a i r i e s o i l s i s commonly a s sumed P e r c o l a t i o n w a t e r can a c c o u n t f o r 5 - 25% o f t h e n i t r o g e n r e m o v a l f r o m humid r e g i o n s o i l s s u b j e c t t o r o t a t i o n c r o p -24 p i n g . Mo s t l e a c h i n g o c c u r s i n l a t e f a l l and w i n t e r i f t h e s o i l i s n o t f r o z e n , and i n t h e e a r l y s p r i n g . L e a c h i n g i n w i n t e r may be s i g n i f i c a n t i f 33 h e a v y r a i n s o c c u r . Thomas c o n c l u d e s : " N o t o n l y does d r a i n a g e p r o c e e d more s l o w l y f r o m c o l d s o i l s (Penman and S c h o f i e l d , 1941) b u t f r o z e n s o i l s do n o t d r a i n a t a l l . When t h e f r o z e n s o i l i s t h a w e d , some downward movement o f n i t r a t e w i l l o c c u r , b u t i t w i l l n o t be deep u n l e s s t h i s i s f o l l o w e d by s p r i n g r a i n s . T h i s s u g g e s t s t h a t i n a r e a s w i t h c o l d w i n t e r c l i m a t e s , l a t e . f a l l a p p l i c a t i o n o f n i t r o g e n may be j u s t as e f f e c t i v e as s p r i n g a p p l i c a t i o n , b u t t h a t n e i t h e r w i l l be v e r y good i f f o l l o w e d by h e a v y s p r i n g r a i n s . " 34 V o l k and. o t h e r s have p u b l i s h e d d a t a o f n i t r o g e n l o s s e s t h r o u g h l e a c h i n g as shown i n T a b l e 8 . 35 T h o m l i n s o n f o u n d t h a t u r e a moves a b o u t as r e a d i l y as n i t r a t e and more e a s i l y t h a n ammonium i n s o i l s . S o i l s h i g h i n o r g a n i c m a t t e r seem t o r e s t r i c t t h e move-ment o f u r e a 3 ^ . L i t t l e i s known o f t h e f a t e o f n i t r a t e o n c e i t r e a c h e s an a q u i f e r . The s a f e s t a s s u m p t i o n i s t h a t n i t r a t e w i l l r e m a i n i n t h e w a t e r t a b l e u n t i l f l u s h e d t h r o u g h o r pumped o u t . The r e s i d e n c e t i m e o f w a t e r i n an a q u i f e r 30 may be a few day s o r more t h a n a h u n d r e d y e a r s . W h i l e t h e c o n c e n t r a t i o n o f n i t r a t e i s s u b j e c t t o f 1 u c t u a t i o n s c a u s e d by d i l u t i o n , s t r a t i f i c a t i o n , and m i x i n g , t h e p o t e n t i a l f o r i t t o e n t e r w a t e r w e l l s and s u r f a c e w a t e r s e x i s t s . •' T a b l e 8 S o i l N i t r o g e n L e a c h i n g L o s s e s l b N/A S o u r c e l b N/A d r a i n a g e C r o p 480 480 480 480 U r e a 0 .5 7.2 81 .1 5.8 P e n s a c o l a B e h i a g r a s s P e n g o l a g r a s s C a r p e t g r a s s C o a s t a l B e r m u d a g r a s s C r o p p i n g 24 N a p p l i e d N l o s s U n f e r t i l i z e d --<- k g / h a / y r - -F e r t i 1 i z ed C o r n . O a t s , A l f a l f a A l f a l f a A l f a l f a C o n t . Co rn Con t .B luegrass 129 1 7 0 0 129 1 7 5.6 4 . 3 4 . 8 4 . 7 6.6 0 . 3 15.1 5.7 3.9 8.6 1 4 . 0 0 .7 31 2. M i n i m i z i n g t h e E n v i r o n m e n t a l I m p a c t The F e d e r a l G o v e r n m e n t o f Canada t h r o u g h t h e M i n i s t r y o f T r a n s p o r t (MOT) d e v e l o p e d t h e p r o c e d u r e o f u s i n g u r e a as a d e - i c e r . R e c o g n i z i n g t h e p o t e n t i a l f o r a d v e r s e e f f e c t s , MOT w i t h E n v i r o n m e n t Canada has been s p o n s o r i n g a p r o g r a m t o e v a l u a t e u r e a ' s e n v i r o n m e n t a l i m p a c t . T h i s s t u d y f o r m s a p a r t o f t h e p r o g r a m . The o b j e c t i v e s w e r e : a) To c a r r y o u t a l i t e r a t u r e r e v i e w on u r e a i n - i e l u d i n g an u p - d a t e on f i n d i n g s a v a i l a b l e f r o m t h e j o i n t A i r Canada ( C o m i n c o ) MOT s t u d i e s . b) To d e t e r m i n e t h e r a t e o f h y d r o l y s - i s and v o l a t i l i z a t i o n o f u r e a d u r i n g w i n t e r c o n d i t i o n s . c ) To d i s c u s s a d d i t i o n a l means o f m i n i m i z i n g n i t r o g e n r e l e a s e t o g r o u n d and s u r f a c e w a t e r s . d) To s u g g e s t p o s s i b l e u r e a a d d i t i v e s and o t h e r i n -f l u e n c i n g f a c t o r s , g i v i n g c o n s i d e r a t i o n t o b) and c) a b o v e . M e t h o d s f o r m i n i m i z i n g t h e e n v i r o n m e n t a l i m p a c t o f u r e a i n c l u d e : n i t r i f i c a t i o n - d e n i t r i f i c a t i o n , b r e a k p o i n t c h l o r i n a -t i o n , s e l e c t i v e i o n e x c h a n g e , a i r s t r i p p i n g , s o i l and p l a n t s , v o l a t i l i z a t i o n o f ammonia on a i r p o r t r u n w a y s , and r e d u c t i o n o f u r e a u s a g e . S i n c e t h e r e i s no p u b l i s h e d l i t e r a t u r e c o n c e r n i n g v o l a t i l i z a t i o n o f ammonia on a i r p o r t r unway s and r e d u c t i o n o.f:, u r e a u s a g e , a l a b o r a t o r y r e s e a r c h p r o g r a m was d e v i s e d t o t e s t t h e s e u r e a c o n t r o l m e t h o d s f o r a i r p o r t a p p l i c a t i o n . The r e -m a i n i n g m e t h o d s f o r m i n i m i z i n g t h e e n v i r o n m e n t a l i m p a c t o f u r e a we re e x a m i n e d i n a l i t e r a t u r e r e v i e w . S e c t i o n 1.2.2 " U r e a N i t r o g e n P a t h w a y s " , c o n s t i t u t e s an i m p o r t a n t p a r t o f t h i s r e v i e w . 32 E x p e r i m e n t a l R e s e a r c h 2.1 V o l a t i l i z a t i o n o f Ammonia by U r e a s e on A i r p o r t Runways . The c o n t r o l o f u r e a d e - i c e r may be a c c o m p l i s h e d on t h e a i r p o r t r unway i t s e l f . U r e a can be h y d r o l y z e d t o ammonia by t h e s o i l enzyme u r e a s e , and t h i s ammonia can v o l a t i 1 i z e t o t h e a t m o s p h e r e . S i n c e u r e a s e i s an a b u n d a n t s o i l e n z y m e , i t may be f o u n d on t h e s u r f a c e o f t h e a i r p o r t r u n w a y . I t i s a s s o c i a t e d w i t h c l a y and o t h e r s o i 1 p a r t i c l e s w h i c h c o u l d f i n d t h e i r way o n t o t h e r unway by w i n d . U r e a s e f r o m t h e s o i l e x h i b i t s wha t c o u l d be c a l l e d , " a n a t u r a l e n z y m a t i c a c t i v i t y " . A t w i n t e r t e m p e r a t u r e s , u r e a s e i s t h e o n l y a g e n t W h i c h can i n d u c e u r e a h y d r o l y s i s . I f t h i s n a t u r a l e n z y m a t i c a c t i v i t y does n o t c a u s e a s i g n i f i c a n t q u a n t i t y o f u r e a t o be h y d r o l y z e d , t h e n i t i s p o s -s i b l e t o i n c r e a s e t h e a c t i v i t y by t h e a d d i t i o n o f a supplemental u r e a s e t o t h e r unway s u r f a c e . T h i s supppmefttail u r e a s e may be a J a c k b e a n meal . A l a b o r a t o r y r e s e a r c h p r o g r a m was p r o p o s e d t o d e t e r -m ine t h e n a t u r a l e n z y m a t i c a c t i v i t y on an a i r p o r t r unway and t o i n v e s t i g a t e t h e p o s s i b i 1 i t y o f enzyme a d d i t i o n t o i n c r e a s e t h e a c t i v i t y . The p r o g r a m was d i v i d e d i n t o 3 eHe'ments as shown i n F i g u r e 3. To d e t e r m i n e t h e n a t u r a l e n z y m a t i c a c t i v i t y , t e s t s we re t o be done on r unway s a m p l e s a t room t e m p e r a t u r e ( in o r d e r t o a s s e s s t h e maximum 1 i k e l y K y d r o l y s i s r a t e ( E l e m e n t 1 ) ) . I f Element 2 natural enzymatic a c t i v i t y of pyrex models under sim-ulated winter con-diti o n s Element 1 natural enzymatic a c t i v i t y of asphalt at room temperature (Hydrolysis ^ 5% ?) (NQ) Element 3 addition of s u p p l e m e n t a l enzyme to increase a c t i v i t y under simulated winter conditions Figure 3 Volatilization of Ammonia Study Flow Diagram 34 l e s s t h a n 5% o f t h e a p p l i e d u r e a we re f o u n d t o be h y d r o l y z e d , a f t e r 90 m i n u t e s f r o m u r e a a p p l i c a t i o n ( t h e maximum l e n g t h o f t i m e MOT o f f i c i a l s f e l t t h e u r e a p e l l e t s w o u l d be a l l o w e d t o s i t on t h e runway b e f o r e s w e e p i n g ) , t h e n t h e r e s e a r c h w o u l d p r o c e e d t o E l e m e n t 3. I f t h e h y d r o l y s i s r a t e was f o u n d t o be g r e a t e r t h a n 5%, t h e n E l e m e n t 2 w o u l d be i n i t i a t e d . T e s t s , u n d e r v a r y i n g c o n d i t i o n s o f t e m p e r a t u r e , i c e t h i c k n e s s , u r e a a p p l i c a t i o n r a t e , u r e a t y p e , and s o l a r r a d i a t i o n w o u l d be p e r f o r m e d . The n a t u r a l e n z y m a t i c a c t i v i t y f o u n d i n E l e m e n t 1 o f t h e r e s e a r c h w o u l d be d u p l i c a t e d u s i n g l a b o r a t o r y g r a d e u r e a s e and P y r e x m o d e l s . P y r e x s u r f a c e s w o u l d be u s e d , r a t h e r t h a n p a v e m e n t , t o a f f o r d g r e a t e r e x p e r i m e n t a l c o n t r o l , as i t i s e x t r e m e l y i m p o r t a n t t o know t h e c o n c e n t r a t i o n o f u r e a s e and u r e a on t h e mode l s u r f a c e . N e i t h e r o f t h e s e c o n c e n t r a t i o n s c o u l d be m e a s u r e d i f a pavemen t s u r f a c e was u s ed b e c a u s e i t i s i m p o s s i b l e t o t h o r o u g h l y c l e a n t h e s u r f a c e be tween t e s t s . A l s o , p e r m e a b i l i t y o f a s p h a l t m a k e s , t o t a l r e t r i e v a l o f 1 i q u i d i m p o s s i b l e . E l e m e n t 3 o f t h e r e s e a r c h w o u l d i n v o l v e u s i n g t h e p y r e x m o d e l s , and l a b o r a t o r y g r a d e u r e a s e t o i n v e s t i g a t e t h e p o s s i b i 1 i t y ' o f i n c r e a s i n g ammonia v o l a t i l i z a t i o n t h r o u g h t h e a d d i t i o n o f u r e a s e t o an a i r p o r t r unway u n d e r w i n t e r c o n d i t i o n s . In E l e m e n t 3, t h e e x p e r i m e n t a l c o n d i t i o n s u s ed i n E l e m e n t 2 , as w e l l as d i f f e r e n t enzyme c o n cen t r a t i o n s ' w o u 1 d 1-be u s e d . -35 A n a l y t i c a l M e t h o d s A f t e r a r e v i e w o f t h e p u b l i s h e d l i t e r a t u r e , t h e method c h o s e n f o r t h e d e t e r m i n a t i o n o f ammonia was t h e " P h e n a t e M e t h o d " as o u t l i n e d i n S t a n d a r d M e t h o d s 3 7 . A d v a n t a g e s o f t h i s me thod o v e r o t h e r ammonia a n a l y s i s me thod s f o r t h i s a p p l i c a t i o n a r e : a) I t i s a " s t a n d a r d m e t h o d " and t h e r e f o r e g e n e r a l l y a c c e p t e d . b) I t does n o t r e q u i r e t h e s a m p l e t e m p e r a t u r e t o be r a i s e d ( i m p o r t a n t b e c a u s e t e m p e r a t u r e a f f e c t s b o t h c h e m i c a l and b i o l o g i c a l h y d r o l y s i s r a t e s ) . c ) T h e r e i s l i t t l e d e l a y b e t w e e n a d d i n g t h e r e a g e n t s a n d a n a l y s i s . d) I t i s a s i m p l e method i n v o l v i n g n e i t h e r c o m p l i c a t e d e q u i p m e n t n o r e x p e n s i v e r e a g e n t s . The method c h o s e n f o r t h e d e t e r m i n a t i o n o f u r e a u t i l i z e s t h e P h e n a t e M e t h o d f o r ammonia and an " u r e a s e i n c u b a t i o n " 3 ^ . The i n c u b a t i o n i n v o l v e s t h e a d d i t i o n o f a c o n c e n t r a t e d , b u f f e r e d , u r e a s e s o l u t i o n t o t h e u r e a s a m p l e . T h i s c o n v e r t s a l l t h e u r e a t o ammon i a . The p r o c e s s f o l l o w s t h e u r e a h y d r o l y s i s r e a c t i o n as shown i n e q u a t i o n 2 - 1 . The ammonia f o r m e d f r o m t h e h y d r o l y s i s o f u r e a i s t h e n m e a s u r e d u s i n g t h e P h e n a t e M e t h o d . The i n t e n s i t y o f t h e b l u e c o l o u r f o r m e d i n t h e P h e n a t e M e t h o d i s , w i t h i n c e r t a i n l i m i t s , p r o p o r t i o n a l t o t h e ammonia c o n c e n t r a t i o n . U n h y d r o l y z e d u r e a does n o t r e a c t w i t h t h e P h e n a t e M e t h o d c h e m i c a l s . and u r e a s e i s i n a c t i v e o n c e t h e c h e m i c a l s a r e a d d e d . In a s a m p l e c o n t a i n i n g ammonia and u r e a ( w i t h o r w i t h o u t u r e a s e ) t h e P h e n a t e Me thod a p p l i e d t o a f r e s h l y c o l l e c t e d s a m p l e y i e l d s t h e ammonia c o n c e n t r a t i o n , and a p p l i e d a f t e r a u r e a s e i n c u b a t i o n , y i e l d s t h e sum o f t h e ammonia p l u s u r e a 36 c o n c e n t r a t i o n . Ammonia and urea s t anda rd s were used to establ i sh a c a l i b r a t i o n c u r v e . The abso rbance o f the s o l u t i o n was measured w i t h a Bausch and Lombe S p e c t r o n i c 88 s p e c t r o p h o t o m e t e r . 2.1.1 N a t u r a l Enzymat i c A c t i v i t y of A i r p o r t Runway Four p i e c e s of a i r p o r t runway were t e s t e d in o r d e r to measure t h e i r n a t u r a l e n z yma t i c a c t i v i t y . Two p i e c e s were o b t a i n e d from A b b o t s f o r d A i r p o r t , one a s p h a l t (Model 1) and one c o n c r e t e (Model 2) , Two aspha 1 1 i c s u r f a c e s were from Vanr: couver I n t e r n a t i o n a l A i r p o r t (V IA) (Model 4 and 5 ) . A reas o f runway were i s o l a t e d by p l a c i n g t i n f o i l c o n t a i n e r s , f rom which the bottom was c u t , on the s u r f a c e s and s e a l i n g them w i t h s i l i c o n e . The two A b b o t s f o r d p i e c e s had i s o l a t e d model a rea s of 450 square c e n t i m e t r e s (25 cm, x 18 cm ). Model 4 had a t e s t 2 2 a rea of 314 cm, (20 cm d i a m e t e r ) and Model 5 had 160 cm (10 cm. x 16 cm ). Both of the VIA models were rougher and more weathered than the A b b o t s f o r d mode l s . Model 4 had some c l a y , g ra s s c l i p p i n g s , and s o i l on i t s s u r f a c e . A l l mode l s , e x c e p t Model 2, r e c e i v e d Cominco p I n d u s t r i a l Grade (C- IG) urea e q u i v a l e n t to 0.90 kg urea/70m-2 (2 l b /750 f t ) a n d ' . s u f f i c i e n t d i s t i l l e d water to produce an i n i t i a l depth o f 5 mm . Due to the p e r m e a b i 1 i t y of the a s p h a l t s u r f a c e s , some of t h e urea s o l u t i o n was l o s t f rom the s u r f a c e . T h i s was p a r t i c u l a r l y e v i d e n t i n Model 4 wh ich had a v i s i b l e c r a c k . Tab l e 9 summarizes the r e s u l t s . 37 T a b l e 9 N a t u r a l E n z y m a t i c A c t i v i t y o f A i r p o r t Runway Mode l No. P e r c e n t U r e a H y d r o l y z e d a f t e r 90 m i n u t e s Comments 1 0. 5 A b b o t s f o r d a s p h a l t 3 0 .4 A b b o t s f o r d c o n c r e t e 4 0 .2 VIA a s p h a l t 5 0 . 4 V IA a s p h a l t A l l t h e a i r p o r t s u r f a c e s had e x p e r i e n c e d p r e v i o u s u r e a a p p l i c a t i o n s i n d i c a t i n g t h a t some r e s i d u a l u r e a and ammonia were e x p e c t e d t o be on t h e s u r f a c e . To t e s t t h i s t h e o r y , o n l y d i s t i l l e d w a t e r was a d d e d t o t h e s u r f a c e o f Mode l 2. A f t e r 90 m i n u t e s , a s a m p l e o f l i q u i d was r e m o v e d and a n a l y z e d . A r e s i d u a l u r e a c o n c e n t r a t i o n was f o u n d , e q u i v a l e n t t o 0 .79 j i g 2 2 /cm ( 1 3 J j g / i n ) , and a r e s i d u a l ammonia c o n c e n t r a t i o n o f 2 2 0 . 3 0 Jig/cm (5 j i g / i n ). The u r e a c o n c e n t r a t i o n i s o n l y 0 . 0 2 3 % 2 o f a 0 . 90 kg /70m. a p p l i c a t i o n . S i n c e t h i s p i e c e p r o b a b l y e x p e r i e n c e d many u r e a a p p l i c a t i o n s , i t i s c l e a r t h a t v i r t u a l l y none o f t h e a p p l i e d u r e a r e m a i n e d on t h e r unway s u r f a c e . A t an a i r p o r t , most u r e a i s r e m o v e d by s w e e p e r s and p l o w s d u r i n g w i n t e r o p e r a t i o n s . Any u r e a r e m a i n i n g on t h e r unway a f t e r w i n t e r , i s r e m o v e d by s p r i n g r a i n s . 38 B a s e d on t h e r e s i d u a l f o u n d on Mode l 2 , r e s i d u a l u r e a c o u l d a c c o u n t f o r up t o 28% o f t h e ammonia c o n c e n t r a t i o n , a f t e r 90 m i n u t e s , f o r Mode l 1. T h e r e f o r e , t h e a c t u a l p e r c e n t o f u r e a h y d r o l y z e d w o u l d be l e s s t h a n 0 . 5 % - s h o w n i n T a b l e 9 . S i n c e t h e n a t u r a l h y d r o l y s i s r a t e a t room t e m p e r a - : t u r e was l e s s t h a n 0 . 5 % , t h e r a t e u n d e r w i n t e r c o n d i t i o n s must be i n s i g n i f i c a n t . The s e c o n d e x p e r i m e n t o f t h e l a b o r a t o r y p r o g r a m ( " l o w t e m p e r a t u r e a c t i v i t y o f e n z y m e " ) was t h e r e f o r e d e l e t e d . 2 . I . 2 . A d d i t i o n o f Enzyme t o I n c r e a s e A c t i v i t y In o r d e r t o s t u d y t h e p o s s i b i l i t y o f i n c r e a s i n g h y d r o l y s i s and v o l a t i l i z a t i o n o f u r e a by t h e a d d i t i o n o f t h e enzyme u r e a s e , a s e r i e s o f 32 t e s t s were p e r f o r m e d u n d e r v a r i o u s e n v i r o n m e n t a l c o n d i t i o n s . T h e s e c o n d i t i o n s i n c l u d e d : a) i c e t h i c k n e s s - 3mm , 5mm , 8mm b) t e m p e r a t u r e - - 4 ° C , 0°C , + 4 ° C , +12°C c ) u r e a a p p l i c a t i o n r a t e t - 0'. 45 k g ' / 70m 2 , 0.90 kg770m'2, 1 . 8'0 k g / 7 0 m 2 d) u r e a t y p e - C o m i n c o - I n d u s t r i a l g r a d e ( C - I G ) , C o m i n c o - F o r e s t r y G r a d e ( C - F G ) , S h e r r i t t Go rdon M i n e s - I n d u s t r i a l G r a d e ( SGM- IG ) e) u r e a s e a d d i t i o n s - 100 mg, 200mg, 500mg, 750mg ( p e r mo de1) f ) s o l a r r a d i a t i o n - 50 B T U / h - f t 2 , 100 B T U / h - f t 2 g) s o l a r r a d i a t i o n - b u f f e r a d d i t i o n . S o l a r r a d i a t i o n was m o d e l l e d by a QF 500 A , 500 w a t t , q u a r t z , G e n e r a l E l e c t r i c l a m p . T h i s l amp p r o d u c e d more i n f r a -39 r e d and l e s s u l t r a - v i o l e t t h a n t h e s u n . A b o u t 20% o f t h e l a m p ' s o u t p u t was l i g h t and 80% was h e a t . The i n p u t e l e c t r i c a l e n e r g y was a s sumed t o be c o m p l e t e l y c o n v e r t e d t o l i g h t o r h e a t e n e r g y . The o u t p u t e n e r g y was a s sumed t o be e v e n l y d i s t r i b u t e d o v e r t h e l i g h t c o v e r a g e a r e a . N e i t h e r o f t h e s e a s s u m p t i o n s a r e t r u e . The a c t u a l s o l a r i n s o l a t i o n i s l o w e r t h a n t h a t c a l c u l a t e d b e c a u s e o f t h e e n e r g y c o n v e r s i o n a s s u m p t i o n , and g r e a t e r t h a n t h e c a l c u l a t e d v a l u e b e c a u s e o f t h e e n e r g y d i s t r i b u t i o n a s s u m p -t i o n . The n e t e r r o r s h o u l d n o t be t o o g r e a t . L i g h t m e t e r s and t h e r m o m e t e r s c o u l d have been u sed t o d e t e r m i n e t h e e x a c t a c c u r a c y o f t h i s m o d e l , b u t , t h i s was c o n s i d e r e d beyond t h e n e e d s o f t h i s e x p e r i m e n t . The h e i g h t o f t h e l amp was a d j u s t e d t o a c h i e v e two r e p r e s e n t a t i v e s o l a r i n s o l a t i o n r a t e s . S o l a r r a d i a t i o n #1 r e p r e s e n t e d an i n s o l a t i o n r a t e o f 50 B T U / h - f t w h i c h a p p r o x i -ma te s a noon sun i n l a t e December a t 5 6° N o r t h L a t i t u d e ( F i g . 4 ) . S o l a r r a d i a t i o n #2 r e p r e s e n t e d - an 2 i n s o l a t i o n r a t e o f 100 B T U / h - f t w h i c h a p p r o x i m a t e s a noon sun i n l a t e December a t 4 8 ° N o r t h L a t i t u d e ( F i g u r e 5) ( o r m i d -F e b r u a r y and November a t 5 6° N o r t h L a t i t u d e ) ) . To b e g i n a t e s t , MCB M a n u f a c t u r i n g C h e m i s t s ' [ D o u b l e S t r e n g t h ' (U x 80 L817)|) u r e a s e was m i x e d w i t h d i s t i l l e d 2 w a t e r and p o u r e d i n t o 33 .5 cm, x 2 1 . 5 cm. (720 cm. ) p y r e x con t a i n e r s . The m o d e l s were p l a c e d i n a c o n t r o l l e d e n v i r o n m e n t r o o m , a t t h e d e s i r e d t e m p e r a t u r e f o r a b o u t 12 h r s . A f t e r t h i s c o o l i n g p e r i o d , u r e a was a d d e d . 42 A f t e r 90 m i n u t e s , samples were taken f rom the m e l t -wa te r and i c e f r a c t i o n s . M e l t w a t e r i s the l i q u i d formed by the a c t i o n o f urea on i c e . Samples were o b t a i n e d by t i p p i n g the py rex model and c o l l e c t i n g the l i q u i d in a beake r . The i c e was me l ted to l i q u i d by p l a c i n g the py rex model i n a warm water bath and samples were taken from the r e s u l t i n g . l i q u i d . Ammonia c o n c e n t r a t i o n , urea c o n c e n t r a t i o n , and volume o f l i q u i d , were de te rm ined f o r the i c e and m e l t w a t e r f r a c t i o n s . . . " At any t i m e , the ;urea c o n t e n t i n the system obeys the e q u a t i o n s : U. + U (2-6) h u t o t a l we i gh t of a p p l i e d urea we i gh t of urea h y d r o l y z e d 11 U = we i gh t of urea u n a l t e r e d where U. U, b u t , where U, ' h i U h l + U v ( 2 " 7 ) we i gh t of urea h y d r o l y z e d which remains i n l i q u i d phase. we i gh t of urea h y d r o l y z e d wh ich goes to gas phase ( v o l a t i l i z a t i o n of ammonia). t h e r e f o r e and , 11 U, , + U + U hi . v u U = U\ h 1 u v t The p e r c e n t urea h y d r o l y z e d i s g i v en by: U h x 100% U 7 U., + U x 100% h I v U (2-8) (2-9) (2 -10) t t The p e r c e n t urea v o l a t i l i z e d i s g i ven by: U v x 100% = U t U 7 U, U... - U x 100% (2-11) hi u 43 The p a r a m e t e r i s k nown , and and U' u can be c a l c u l a t e d U = 3 x V + B. x V. ( 2 - 1 2 ) u w m m i i w h e r e : B M = u r e a c o n c e n t r a t i o n i n m e l t w a t e r V = v o l u m e o f m e l t w a t e r m B. = u r e a c o n c e n t r a t i o n i n i c e i V. = v o l ume o f l i q u i d f r o m i c e U,,= 1 (A x V + A. x V . ) 60 ( 2 - 1 3 ) h l T j r m m 1 1 T 7 w h e r e : A = ammonia c o n c e n t r a t i o n i n m e l t w a t e r m A . = ammonia c o n c e n t r a t i o n i n i c e i a n d , 60 i s t h e m o l e c u l a r w e i g h t o f u r e a 17 i s t h e m o l e c u l a r w e i g h t o f ammonia 1/2 i s t h e number o f m o l e s o f u r e a w h i c h p r o d u c e s one mo l e o f ammonia ( f r o m e q u a t i o n . 2 - 1 ) T a b l e 10 s u m m a r i z e s t h e t e s t s and r e s u l t s . The e f f e c t s o f d i f f e r e n t e n v i r o n m e n t a l c o n d i t i o n s may be d e d u c e d f r o m t h e r e s u l t s . The c o m p a r i s o n i s made w i t h t h e a i d o f l i n e g r a p h s and " p i e d i a g r a m s " . In t h e s e p i e d i a g r a m s t h e e n t i r e c i r c l e r e -p r e s e n t s t h e a p p l i e d u r e a , U^., as d e p i c t e d i n F i g u r e 6. T e m p e r a t u r e ( F i g u r e 7 and 8) When t h e t e m p e r a t u r e was i n c r e a s e d t h e q u a n t i t y o f u r e a h y d r o l - y z e d i n c r e a s e d d r a m a t i c a l l y , f r o m 7% a t - 4 ° C t o 49% a t 12°C ( o f t h e a p p l i e d u r e a ) f o r an a d d i t i o n o f 200 mg. u r e a s e t o t h e m o d e l , and f r o m 17% a t - 4 ° C t o 65% a t 12°C f o r 500 mg. u r e a s e . A t - 4 ° C . , t h e m e l t w a t e r c o n t a i n e d no ammonia and o n l y 9% o f t h e a p p l i e d u r e a f o r t h e 200 mg. u r e a s e t e s t and o n l y Table 10 Hydrolysis Resulting from Urease Addition T E S T NO. T E M P E R A -T U R E ° C - 4 0 4 1 2 U R E A S E X I 0 0 m g 1 2 5 lh I c e T h . m m 3 5 8 J r . A p p . < g / 7 0 m 2 4 5 .9 L8 U r . T y . Ci]Cf4SGM O t h e r S 1 J S 2 [ B % U r . H y d . A - l 0 # # 0 2 0 % A - 2 w 0 3 8 B - l n 0 # HP 0 /A. 3 8 B - 2 0 0 0 9 C - l 0 0 0 0 1 1 C - 2 0 # 0 2 2 D - l 0 0 0 0 7 D - 2 0 0 0 1 7 E - l w 0 0 0 3 0 E - 2 0 0 0 6 3 F - l 0 - # @ 4 9 F - 2 619 0 0 0 6 5 G - l 0 0 0 0 1 2 G - 2 0 0 0 0 0 1 8 H - l 0 # 0 1 8 K - 2 0 0 0 0 5 8 1 - 1 0 0 0 0 0 7 1 - 2 0 0 S3 # 0 2 6 J-l 0 0 0 0 9 J - 2 0 0 # 0 0 ' 6 K - l 0 0 0 1 1 K - 2 0 0 0 4 L - I 0 0 # 0 1 3 L-2 0 0 0 0 0 4 M - l 0 0 # 1 0 M - 2 0 0 0 # 0 4 N-1 0 0 m 0 0 x 0 2 6 N-2 0 # 0 0 0 3 0 0 - 1 0 0 0 0 0 5 1 0-2 0 # 0 0 6 7 P - l IP 0 0 0 0 # 2 2 P - 2 0 0 0 0 0 2 8 Figure 6 Key to "Pie Diagrams" weight of applied urea weight of urea hydrolyzed to ammonia weight of urea unaltered (chemically) weight of hydrolyzed urea i n l i q u i d weight of v o l a t i l i z e d urea meltwater gas ic e f r a c t i o n 46 4% u r e a f o r t h e 500 mg. t e s t . A t 0°C , ammonia was f o u n d i n t h e m e l t w a t e r . F i g u r e 8 shows t h a t t h e p e r c e n t a g e o f t h e a p p l i e d u r e a h y d r o l y z e d a f t e r 90 m i n u t e s i n c r e a s e s l i n e a r l y when p l o t t e d a g a i n s t t e m p e r a t u r e f o r a 200 mg. u r e a s e a d d i t i o n . O t h e r t h a n t h e p o i n t a t 4°C , t h e 500 mg u r e a s e c u r v e i s a p p r o x i m a t e l y p a r a l l e l t o t h e 200 mg c u r v e . Ammonia v o l a t i l i z a t i o n o c c u r r e d o n l y a t + 12°C w i t h a 500 mg u r e a s e a d d i t i o n (7% o f t h e a p p l i e d u r e a ) . U r e a s e ( F i g u r e 9 and 10) A t 0°C and 8 mm. i c e t h i c k n e s s , an a d d i t i o n o f 100 mg u r e a s e c a u s e d 7% o f t h e a p p l i e d u r e a t o be h y d r o l y z e d , w h e r e a s 500 mg. u r e a s e c a u s e d 26% t o be h y d r o l y z e d . No ammonia was v o l a t i l i z e d . The p e r c e n t a g e o f u r e a and h y d r o l y z e d u r e a ( ammon ia ) i n t h e m e l t w a t e r and i c e f r a c t i o n s , does n o t f o l l o w any p a t t e r n f o r t h i s e x p e r i m e n t . In some c a s e s , t h e a t t e m p t e d r e t r i e v a l o f m e l t w a t e r . by t i p p i n g t h e mode l d i d n o t y i e l d a l l t h e l i q u i d . Some was t r a p p e d u n d e r t h e i c e s u r f a c e . F o r t h i s r e a s o n , d a t a c o m p a r i n g u r e a and h y d r o l y z e d u r e a i n t h e m e l t w a t e r o r i c e f r a c t i o n i s n o t v e r y a c c u r a t e . The c a l c u l a t i o n s o f o v e r a l l p e r c e n t u r e a h y d r o l y z e d and r e m a i n i n g u r e a i n t h e s y s t e m a r e o f g r e a t e r a c c u r a c y ( p e r h a p s + 2 0 % ) . The p e r c e n t u r e a h y d r o l y z e d i s p r o p o r t i o n a l t o t h e c o n -c e n t r a t i o n o f u r e a s e as shown i n F i g u r e 10. (D-l) (A-l) (E-l) (F-l) -4°C 0°C + 4°C *12°C 79 (D-2) 500 mg Urease (A-2) (E-2) Figure 7 (F-2) Effect of Temperature at 5 mm Ice and 0.9 kg/70 m Urea (1-1) 100 mg (C-2) 200 mg (1-1) 500 mg 71 (H-l) 10 0 mg (A-l) c . n (A-2) Figure 9 2 00 mg 500 mg Effect of Urease at 0°C and 0.90 kg/70 m Urea 5 mm Ice to 50 70. r Urease Concentration (mg/ml) Figure 10 Percent Urea Hydrolyzed vs. Urease Concentration 51 I c e T h i c k n e s s W h i l e t h e a c t u a l q u a n t i t y o f m e l t w a t e r w o u l d be t h e same f o r d i f f e r e n t i c e t h i c k n e s s e s , t h e amount r e t r i e v e d was n o t , i n t h e s e e x p e r i m e n t s . The 5 mm t h i c k i c e t e s t y i e l d e d t h e l e a s t m e l t w a t e r (12 ml f r o m 5 mm i c e v e r s u s 20 ml and 88 ml f o r t h e 3 mm and 8 mm t e s t s r e s p e c t i v e l y ) . D i f f e r e n t q u a n t i t i e s o f m e l t w a t e r were r e t r i e v e d b e c a u s e o f i n c o m p l e t e i c e f o r m a t i o n p r i o r t o t h e t e s t , t r a p p e d a i r b u b b l e s u n d e r t h e i c e , and d i f f e r e n t m e l t w a t e r l e n s c o n f i g u r a t i o n s a r o u n d t h e d r o p h o l e . T h i s i n c o m p l e t e m e l t w a t e r r e t r i e v a l a f f e c t e d t h e r e s u l t s . The t h i n n e r i c e m o d e l s w i t h a g r e a t e r u r e a s e c o n c e n t r a t i o n , w o u l d have been e x p e c t e d t o p r o d u c e a g r e a t e r p e r c e n t a g e o f h y d r o l y z e d u r e a t h a n t h e t h i c k e r i c e . H o w e v e r , t h i s d i d n o t o c c u r as shown i n F i g u r e 1 1 . U r e a a p p l i c a t i o n W h i l e , as shown i n F i g u r e 1 2 , an i n c r e a s e i n u r e a a p p l i c a -t i o n d e c r e a s e s t h e p e r c e n t a g e o f u r e a h y d r o l y z e d , t h e a c t u a l 2 q u a n t i t y i s r o u g h l y e q u a l ( 1 28 mg, - 0 . 4 5 kg/70m ; 185 mg - 0 . 9 0 k g / 7 0 m 2 ; 165 mg - 1 .80 k g / 7 0 m 2 ) . U r e a t y p e ( F i g u r e 13 and 1 4 ) . The t h r e e t y p e s o f u r e a t e s t e d e x h i b i t e d s i m i l a r p e r c e n t u r e a h y d r o l y z e d u n d e r s i m i l a r c o n d i t i o n s . S o l a r r a d i a t i o n ( F i g u r e 15) S o l a r r a d i a t i o n i n f l u e n c e d g r e a t l y t h e q u a n t i t y o f u r e a h y d r o l y z e d a f t e r 90 m i n u t e s . In one c a s e , 500 mg u r e a s e , and ( C - l ) 3 mm ( A - l ) 5 mm (C-2) 8 mm Figure 11 Effect of Ice Thickness at 0°C and 200 mg Urease Addition ( B - l ) ( A - l ) ( B-2) 0.45 kg/70 m2 0.90 kg/70 m2 1.8 kg/70 m2 Figure 1 2 Effect of Urea Application Rate at 0°C, 200 mg Urease, and 5 mm Ice Thickness en CO (M-2J C-IG (K-2) C-FG (L-2) SGM-IG Figure 13 Effect of Urea Type 8 nun ice 0°C at 200 mg urease and 1.8 kg/70 m urea ( A - l ) C-IG (G-l) C-FG Urea Type (M-l) ( K - l ) ( L - l ) Figure 14 Effect of Urea Type at 200 mg Urease and 5mm I c e Thickness (N -1) ( 0 -1 ) ( P - l ) S o l a r Rad. #1 S o l a r Rad. #2 S o l a r Rad. #2 + B u f f e r (N-2) (0-2) (P-2) Figure 15 Effect of Solar Radiation 2 a+ - 4 ° C , 5mm I c e , and- 0 , 9 0 kg/70m U r e a 57 s o l a r r a d i a t i o n #2 c a u s e d 15% o f t h e a p p l i e d u r e a t o be v o l a t i l i z e d . W i t h no s o l a r r a d i a t i o n , v e r y l i t t l e m e l t w a t e r f o r m e d , w h e r e a s , w i t h o n l y s o l a r r a d i a t i o n #2 a d d e d , a l l t h e i c e was c o n v e r t e d t o m e l t w a t e r . As no t h e r m o m e t e r was p l a c e d i n t h e m o d e l , i t i s n o t known how much t h e t e m p e r a t u r e was r a i s e d by s o l a r r a d i a t i o n . 2 .2 R e d u c t i o n o f U rea Use The e n v i r o n m e n t a l i m p a c t o f u r e a may be r e d u c e d by d e c r e a s i n g t h e q u a n t i t y o f u r e a u sed on an a i r p o r t r u n w a y . T h i s can be done by o p t i m i z i n g t h e a p p l i c a t i o n n a t e and t h e u r e a t y p e , f o r b e s t d e - i c i n g . In o r d e r t o g a i n a b e t t e r u n d e r s t a n d i n g o f t h e d e -i c i n g a c t i o n o f u r e a p e l l e t s , e x p e r i m e n t s u s i n g an u r e a i n d i c a -t o r , and p h o t o g r a p h y e q u i p m e n t were d o n e . S e v e r a l i n d i c a t o r s we re t e s t e d i n c l u d i n g : E h r l i c h ' s r e a g e n t , T o l l e n ' s r e a g e n t , p h e n o l p h t h a l e i n , and l i t m u s p a p e r . E h r l i c h ' s r e a g e n t p r o d u c e d t h e b e s t r e s u l t s . E h r l i c h ' s r e a g e n t was d e v e l o p e d as a method f o r t h e d e t e r m i n a t i o n o f u r e a i n b l o o d and u r i n e , b a s e d on t h e u r e a - p -d i - m e t h y l a m i n o b e n z a l d e h y d e r e a c t i o n . An i m m e d i a t e , c l e a r , s t a b l e y e l l o w c o m p l e x f o r m s f r o m t h e r e a c t i o n . The a b s o r b -a n c e o f t h e c o l o u r e d s o l u t i o n may be d e t e r m i n e d w i t h a s p e c t r o p h o m e t e r s e t a t 425 win w a v e l e n g t h . L e v i n e ( e t a l . ) ^ n o t e d t h a t t h e c a l i b r a t i o n c u r v e i s l i n e a r up t o 100 mg u r e a / 100 m l . Ammonia was n o t f o u n d t o i n t e r f e r e w i t h t h e r e a c t i o n . A c a l i b r a t i o n c u r v e was p l o t t e d f r o m d a t a u s i n g 58 urea standards and Ehrlich reagent at 0°C (Figure 16). The cali b r a t i o n curve levels off abruptly above 50 mg., urea/10 ml. As a quantitative method for urea , Ehrlich reagent is unsuitable above this concentration (at 425 -nw wavelength). Three types of urea were photographed - S h e r r i t t Gordon Mines - Industrial Grade (SGM-IG), Cominco-Industrial Grade (C-IG), and Cominco-Forestry Grade (C-FG). The two Cominco grades of urea contain Formaldehyde as an anti-caking additive, while the Sherritt Gordon Mines' pellets contain white mineral o i l . The three types of urea pellets vary in size as shown in Table 11 and Figure 17. On a weight basis, the Sherritt Gordon Mines pellets cover a larger surface area than the two Cominco grades. Close-up photographs were taken of single urea 2 p e l l e t s , and urea applied at 0.90 kg/70m for each urea type. Photographs at 0 (no p e l l e t ) , 0 (pellet) 2,5,10,15,30,60, and 90 minutes after p e l l e t placement on the ice surface were taken. The ice was 5 mm thick and contained 3% Ehrlich reagent. Tests were conducted at -4°C. The reaction between Ehrlich's reagent and urea, produces a yellow "aura" which indicates the movement of urea through ice. The f i r s t attempt to photograph a single C-FG p e l l e t involved a small 12.5 cm x 12.5 cm p l a s t i c grid taped onto the pyrex model. The 3% Ehrlich reagent was added, frozen, and photographs of the urea p e l l e t taken. The aura, after 90 minutes, is characterized by a 1' *p-m% wide channel which fans out Urea Content (mg/10 ml) 60-O i l c o n d i t i o n i n g a g e n t ) S i eve (mm) +8 ( U . S . s t n d . ) ( 2 . 3 8 ) + 10 ( 2 . 0 0 ) + 12 ( 1 . 6 8 ) + 14 ( 1 . 4 4 ) + 16 ( 1 . 1 9 ) + 20 ( 0 . 9 5 ) P a s s i n g +20 (<0 .95 ) T a b l e 11 S c r e e n A n a l y s i s f o r U r e a Type s S h e r r i t t G o r d o n M i n e s - I n d u s t r i a l G r ade ( w h i t e M i n e r a l C u m u l a t i v e Wt. % 3.4 1 4 . 5 51 . 7 79 .0 88.1 ' 95.1 1 00 . 0 C o m i n c o - I n d u s t r i a l G r ade ( F o r m a l d e h y d e c o n d i t i o n i n g a g e n t ) S i eve C u m u l a t i v e Wt. % + 8 ( T y l e r Mesh) ( 2 . 0 6 ) 7 0 . 0 +10 ( 1 . 6 5 ) 9 9 . 5 +14 ( 1 . 1 8 ) 9 9 . 9 +20 ( 0 . 8 0 ) 9 9 . 9 C o m i n c o - F o r e s t r y G r ade ( F o r m a l d e h y d e c o n d i t i o n i n g a g e n t ) S i e v e C u m u l a t i v e Wt. % +4 ( T y l e r Mesh) ( 4 . 1 2 ) 40 +6 ( 2 . 7 5 ) 9 9 . 5 61 Figure 17 1 G r a m of the Three Tvnes of Urea 62 a t t h e edge o f t h e g r i d ( F i g u r e 1 8 ) . A t t h e c o n c l u s i o n o f t h e e x p e r i m e n t , t h e i c e was r emoved f r o m t h e m o d e l , and a dome s h a p e d i c e l e n s was f o u n d u n d e r t h e g r i d . The p l a s t i c g r i d p r e v e n t e d t h e u r e a p e l l e t f r o m p e n e t r a t i n g t h i s i c e l e n s . The y e l l o w a u r a i n d i c a t e d w h e r e t h e u r e a - r i c h l i q u i d f r o n t had t r a v e l l e d down t h e s i d e o f t h e dome and f a n n e d o u t a t t h e edge o f t h e g r i d . T h i s b e h a v i o u r r e s e m b l e s t h e a c t i o n o f a l i q u i d , r a t h e r t h a n m o l e c u l a r d i f f u s i o n o f u r e a t h r o u g h s o l i d i c e , as m o l e c u l a r d i f f u s i o n w o u l d have been e x p e c t e d t o p r o d u c e a c o n c e n t r i c a u r a a b o u t t h e p e l l e t d r o p h o l e . The a u r a seems t o i n d i c a t e t h e move -ment o f u r e a a t t h e i c e - s o l i d i n t e r f a c e . In s u b s e q u e n t e x p e r i m e n t s , i c e c o u l d n o t f o r m u n d e r t h e g r i d , w h i c h was g l u e d t o t h e m o d e l ' s g l a s s s u r f a c e . P h o t o g r a p h s o f t h e t h r e e t y p e s o f , s i n g l e , u r e a p e l l e t s showed t h a t t h e u r e a - E h r l i c h r e a g e n t a u r a g rew w i t h t i m e ( F i g u r e s 1 9 , 2 0 , and 2 1 ) . The u r e a p e l l e t s do n o t r e m a i n s t a t i o n a r y , e v e n when t h e y s i t on smooth s u r f a c e s a t t h e b o t t o m o f t h e d r o p h o l e . D i f f e r -e n t i a l s o l u t i o n o f t h e s i d e s o f t h e p e l l e t , a n d , o r , i c e c r y s -t a l o r i e n t a t i o n c a u s e d t h e p e l l e t t o wande r up t o 2 cm. Due t o t h e i r " l o n g e r l i f e " , t h e l a r g e r C-FG p e l l e t s t r a v e l l e d t h e f u r t h e s t ( F i g u r e s 22 and 2 3 ) . The C-FG p e l l e t c o m p l e t e l y d i s -s o l v e d i n 30 m i n u t e s , t h e C - IG i n 10 m i n u t e s , and t h e SGM-IG i n 5 m i n u t e s . The r a t e o f y e l l o w a u r a g r o w t h i s n o t e q u a l f o r t h e t h r e e u r e a t y p e s ( F i g u r e 2 4 ) . A f t e r 90 m i n u t e s , t h e C-FG a u r a c o v e r e d 3.6 t i m e s as much a r e a as t h e C - IG a u r a , and 6 .0 t i m e s as much as t h e SGM- IG . The a v e r a g e r a t e o f a u r a g r o w t h i s g r e a t e s t a l m o s t i m m e d i a t e l y a f t e r p e l l e t a p p l i c a t i o n ( F i g u r e 2 5 ) . 6 4 ( a c t u a l s i z e ) i n i t i a l p e l l e t p o s i t i o n 90 min, 65 2 min. 5 min. 3.0 min. 15 min. Composite 30 min. Figure 2 0 C-IG Aura Growth (actual size) 60 min. / 30 m i n . 69 14CT Time after pellet application (min.) Figure 25 Average Rate of Aura Growth 7 1 A f t e r 90 m i n u t e s , b o t h t h e C - IG and SGM-IG u r e a p e l l e t s had v e r y l o w a u r a g r o w t h r a t e s . The C o m i n c o - F o r e s t r y G rade a u r a was 2 g r o w i n g a t an a v e r a g e r a t e o f 22 mm /min a f t e r 90 m i n u t e s . A t t h a t t i m e t h e SGM-IG and C - IG a u r a s had a p p r o a c h e d t h e i r l a r g e s t s i z e , w h i l e t h e C-FG a u r a w o u l d be e x p e c t e d t o grow s i g n i f i c a n t l y f o r some t i m e . The y e l l o w a u r a g r o w t h f o l l o w s two p r o c e s s e s - t h e d i s i n t e g r a t i o n o f t h e s o l i d u r e a p e l l e t t o p r o d u c e a u r e a r i c h l i q u i d , and t h e movement o f t h e l i q u i d f r o n t away f r o m t h e p e l l e t p r o d u c e d d r o p h o l e . As t h i s f r o n t m o v e s , t h e u r e a c o n c e n t r a t i o n o f t h e l i q u i d d e c r e a s e s and i t s a b i l i t y t o m e l t i c e a l s o d e -c r e a s e s - e x p l a i n i n g t h e d e c r e a s i n g r a t e o f a u r a g r o w t h . In s p i t e o f a l a r g e r a u r a g r o w t h r a t e , t h e C-FG p e l l e t d i d n o t p r o d u c e t h e l a r g e s t a u r a on a w e i g h t b a s i s . F o r t h e t h r e e t y p e s o f u r e a , F i g u r e 26 i l l u s t r a t e s t h e a u r a a r e a by u r e a w e i g h t v e r s u s t i m e . A f t e r 90 m i n u t e s , t h e SGM-IG p e l l e t a u r a c o v e r e d 1.9 t i m e s t h e a r e a , p e r mg. o f u r e a , o f t h e C - IG p e l l e t ; and 3.0 t i m e s o f C-FG u r e a . F o r a g i v e n w e i g h t o f u r e a , t h e r e f o r e , t h e SGM-IG p r o d u c e s a l a r g e r a u r a . T r a c i n g s o f p h o t o g r a p h s i n F i g u r e 2 7 , 2 8 , and 2 9 , 2 a t t h e 0 . 90 kg/70m u r e a a p p l i c a t i o n r a t e , show t h a t , by w e i g h t , t'he SGM-IG u r e a p r o d u c e d t he . l a r g e s t a u r a . A f t e r 90 m i n u t e s , the. C-FG a u r a was about .;. h a l f t h e s i z e o f SGM-IG a u r a . The a u r a s a s s o c i a t e d w i t h e a c h o f t h e 205 SGM-IG p e l l e t s o v e r l a p p e d s u ch t h a t , a f t e r 90 m i n u t e s , t h e t o t a l a u r a a r e a wja-s-onl y 34% o f t h e t h e o r e t i c a l a r e a . The o v e r l a p o f a u r a s 72 140> 0 10 20 30 40 50 60 70 80 90 Time from Pellet Application (min) Figure 26 Aura Growth per Weight of Urea 76 f o r t h e two Com inco g r a d e s was t h e same ( Tab l e 1 2 ) . P e l l e t s we re r a n d o m l y p l a c e d on t h e i c e s u r f a c e . Had t h e s e p e l l e t s been e v e n l y d i s t r i b u t e d , t h e a u r a s i z e w o u l d have been g r e a t e r i n e a c h . L i t e r a t u r e R e v i e w o f N i t r o g e n  Remova l T r e a t m e n t S y s t e m s 2 . 3 B i o 1 o g i c a l N i t r i f i c a t i on -.• Den i t r i f i c a t i on T h i s t r e a t m e n t method u t i 1 i z e s N i t r o s o m o n a s and N i t r o b a c t e r b a c t e r i a f o r n i t r i . f i c a t i on ; PseuHomonas , M i c r o - : : c o c c u s , A c h r o m o b a c t e r , a n d B a c i 1 1 us f o r d e n i t r i f i c a t i o n . Ni t r o - somonas o x i d i z e ammonium t o n i t r i t e , as shown i n e q u a t i o n 2 - 2 . N i t r o b a c t e r o x i d i z e n i t r i t e t o n i t r a t e , as shown i n e q u a t i o n 2 - 3 . The n e t r e a c t i o n i s : N H 4 + + 2 0 2 — * - N 0 3 " + 2 H + •+ HgO ( 2 - 1 4 ) The e n e r g y r e l e a s e d by t h e s e r e a c t i o n s i s r e q u i r e d by t h e o r g a n i s m s f o r g r o w t h . M a j o r e n v i r o n m e n t a l f a c t o r s w h i c h c o n t r o l t h e r a t e o f n i t r i f i c a t i o n i n c l u d e : t e m p e r a t u r e , p H , ammonia c o n c e n t r a t i o n , and d i s s o l v e d o x y g e n c o n c e n t r a t i o n . D e n i t r i f i c a t i o n i s t h e c o n v e r s i o n o f n i t r a t e n i t r o g e n t o g a s e s s u c h as n i t r o g e n , n i t r o u s o x i d e , o r n i t r i c o x i d e . T h i s p r o c e s s o c c u r s i n t h e a b s e n c e o f o x y g e n . D e n t r i f i c a t i o n i s a two s t e p p r o c e s s i n v o l v i n g c o n v e r s i o n o f n i t r a t e t o n i t r i t e , f o l l o w e d by c o n v e r s i o n o f n i t r i t e t o n i t r o g e n g a s . When m e t h a n o l i s u s e d as t h e e l e c t r o n d o n o r , d e n i t r i f i c a t i o n i s r e p r e s e n t e d b y : T a b l e 12 2 A u r a A r e a a t 90 m i n . f o r 0 . 9 kg/70m U r e a U r e a Type N umber o f P e l l e t s A p p l i e d A r e a o f A u r a (mm 2) % A r e a o f A u r a o f T o t a l Mode l A r e a T h e o r e t i c a l A r e a o f A u r a ( b a s e d on s i n g l e ^ p e l 1 e t ) (mm ' A c t u a l A r e a T h e o r e t i c a l A r e a % C-FG 12 22700 36 43200 53 C - IG 67 35500 56 66700 53 SGM-IG 205 41 800 67 122200 34 78 Energy r e a c t i o n : 6N0 3"+ 5CH30H — » - 5 C 0 2 + 3N 2+7H 20 + 60H" ( 2 - 1 5 ) Synthes i s r e a c t i o n : 3M0 3"+ 14CH30H + C0 2+ 3 H + — - 3 C 5 H 7 0 2 N + 19H 20 ( 2 - 1 6 ) In g e n e r a l , an M/N r a t i o (mg. o f m e t h a n o l p e r mg o f i n i t i a l n i t r a t e n i t r o g e n ) o f 3.0 w i l l e n a b l e 95% d e n i t r i f i c a t i o n . B r e w e r y w a s t e s , v o l a t i l e a c i d s , and m o l a s s e s may a l s o be u sed as e l e c t r o n d o n o r s . M a j o r e n v i r o n m e n t a l f a c t o r s w h i c h c o n t r o l t h e r a t e o f d e n i t r i f i c a t i o n i n c l u d e : t e m p e r a t u r e , p H , c a r b o n c o n c e n t r a t i o n , and n i t r a t e c o n c e n t r a t i o n . F i g u r e 30 i s t h e f l o w d i a g r a m o f t h e n i t r i f i c a t i o n -den i t r i f i c a t i o n p r o c e s s . 2 . 4 B r e a k p o i n t C h l o r i n a t i o n B r e a k p o i n t c h l o r i n a t i o n i s a p r o c e s s i n w h i c h d i l u t e aqueou s s o l u t i o n s c o n t a i n i n g ammonia a r e o x i d i z e d t o n i t r o g e n gas by t h e a d d i t i o n o f c h l o r i n e . When c h l o r i n e gas i s d i s s o l v e d i n w a t e r , h y d r o l y s i s o f t h e c h l o r i n e m o l e c u l e o c c u r s : C l 2 + H 2 0 — » - H 0 C l + H + + C I " ( 2 - 1 7 ) A f t e r s u f f i c i e n t c h l o r i n e has been a d d e d , H y p o c h l o r o u s a c i d (HOC1) c a u s e s t h e o x i d a t i o n o f ammonium i o n b y : NH 4 + + 1.5H0C1 *0.5U2 + 1 .Stifl + 2 .5H + + 1.5C1 : (2-18) In p r a c t i c e , t h e a c t u a l w e i g h t r a t i o o f c h l o r i n e t o ammonia 4 3 n i t r o g e n a t b r e a k p o i n t r a n g e s f r o m 8:1 t o 10:1 The o p t i m u m r a n g e o f pH f o r b r e a k p o i n t c h l o r i n a t i o n i s pH 6 t o 7. T e s t s c o n d u c t e d o u t s i d e t h i s r a n g e show an a p p r e c i a b l y h i g h e r c h l o r i n e r e q u i r e m e n t f o r b r e a k p o i n t and s l o w e r r e a c t i o n r a t e s . I n f l u e n t NITRIFICATION ( c o n v e n t i o n a l A c t i v a t e d S l u d g e P l a n t ) DENITRIFICATION A e r a t e d N i t r o g e n S t r i p p i n g Channel A n o x i c M i x e d D e n i t r i f i c a t i o n R e a c t o r R e t u r n Sludge E f f l u e n t Figure 30 E x c e s s S l u d g e methano Nitrification - Denitrif ication Flow Diagram 80 N i t r a t e and o d o r o u s n i t r o g e n t r i c h l o r i d e (NC I ^ ) a r e o c c a s i o n a l l y f o u n d i n t h e e f f l u e n t , d e p e n d i n g upon t h e d e g r e e o f p r e t r e a t m e n t and pH i n t h e r e a c t i o n z o n e . The t o t a l c o n -c e n t r a t i o n o f t h e s e r e s i d u a l s r a r e l y e x c e e d s 10% o f t h e i n f l u e n t 44 ammonia c o n c e n t r a t i o n F o r b r e a k p o i n t c h l o r i n a t i o n t o w o r k , t h e u r e a d e -i c e r must f i r s t have been h y d r o l y z e d t o ammon i a . H y d r o l y s i s can o c c u r c h e m i c a l l y o r b i o l o g i c a l l y . C h e m i c a l h y d r o l y s i s p r o -c e e d s v e r y s l o w l y a t t e m p e r a t u r e s a r o u n d 25°C and w o u l d be i n -45 s i g n i f i c a n t a t t e m p e r a t u r e s b e l o w f r e e z i n g . . 46 A t k i n s o n f o u n d t h a t t h e b a c t e r i a P r o t e u s v u l g a r i s e x h i b i t e d u r e a s e a c t i v i t y i n w a t e r as l o w as 0°C. S o i l b a c t e r i a s u c h as B a c i l l u s p a s t e u r i i , K l e b s i e l l a , E s c h e r i cha , and C i t r o b a c t e r a l s o e x h i b i t u r e a s e a c t i v i t y , b u t n o t a t v e r y l o w t e m p e r a t u r e s . I t may be p o s s i b l e t o n u r t u r e a b a c t e r i a c u l t u r e t o s u p p l y t h e u r e a s e a c t i v i t y f o r h y d r o l y s i s . In a b i o l o g i c a l r e a c t o r , t h e u r e a s e b a c t e r i a s l u d g e w o u l d be r e c y c l e d , s i m i l a r t o a c o n v e n t i o n a l a c t i v a t e d s l u d g e s y s t e m . T h e r e a r e t h r e e m a j o r p r o b l e m s w i t h t h i s s y s t e m . Due to i c i n g p r o b l e m s , t h e r e a c t o r may n o t o p e r a t e a t f r e e z i n g t e m p e r a t u r e s . M o r e o v e r , a t l o w t e m p e r a t u r e s above f r e e z i n g , t h e h y d r o l y s i s e f f i c i e n c y w o u l d be l o w . In t i m e s o f l ow d e -i c e r w a s t e f l o w , t o p r e v e n t b a c t e r i a s t a r v a t i o n ( p a r t i c u l a r l y i n s u m m e r - m o n t h s ) , u r e a w o u l d have t o be added d i r e c t l y t o t h e r e a c t o r . 81 2 . 5 S e l e c t i v e Ion E x c h a n g e S e l e c t i v e i o n e x c h a n g e a l s o r e q u i r e s p r i o r h y d r o l y s i s o f t h e u r e a w a s t e s t r e a m . C o n v e n t i o n a l i o n e x c h a n g e r e s i n s have n o t w o r k e d w e l l i n p r a c t i c e f o r r e m o v a l o f ammonium o r n i t r a t e i o n s f r o m w a s t e w a t e r s b e c a u s e o f r e s i n p r e f e r e n c e f o r o t h e r i o n s . An e x c h a n g e r w h i c h i s s e l e c t i v e f o r ammonium i s more e f f e c t i v e t h a n c o n v e n t i o n a l r e s i n s . C l i n o p t i 1 o l i t e z e o l i t e , i s t h e c u r r e n t l y f a v o u r e d e x c h a n g e r . S e l e c t i v e i o n e x c h a n g e i s a s i m p l e p r o c e s s . W h i l e t h e w a s t e w a t e r p a s s e s downward t h r o u g h t h e c l i n o p t i 1 o l i t e b e d , t h e ammonia i s r e m o v e d . When t h e ammonia c o n c e n t r a t i o n i n t h e e f f l u e n t e x c e e d s a s p e c i f i e d c r i t i c a l l e v e l , t h e bed i s r e -g e n e r a t e d by p a s s i n g a c o n c e n t r a t e d s a l t s o l u t i o n t h r o u g h i t . Ammonia may be r e m o v e d f r o m t h e r e g e n e r a n t by r e l e a s e o f n i t r o g e n gas o r r e c o v e r y o f an ammonia s o l u t i o n , t h u s a v o i d i n g t h e p r o -b l e m o f d i s p o s a l o f a c o n c e n t r a t e d b r i n e s o l u t i o n ( F i g u r e 3 1 ) . The f a c t o r s w h i c h s i g n i f i c a n t l y a f f e c t t h e i o n e x -change p r o c e s s a r e : pH , h y d r a u l i c l o a d i n g r a t e , c l i n o p t i 1 o l i t e s i z e , p r e t r e a t m e n t , w a s t e w a t e r c o m p o s i t i o n and bed d e p t h . The o p t i m u m pH f o r ammonia e x c h a n g e i s b e t w e e n pH 4 and 8. T y p i c a l h y d r a u l i c l o a d i n g r a t e s f o r 20 x 50 mesh c l . i n o p t i 1 o l - i t e a r e 7.5 t o 20 Bed V o l u m e s / h o u r ( B V / h r ) o r 0 . 9 5 - 2 . 6 g p m / f t 3 . D a t a i n -d i c a t e s t h a t 20 x 50 mesh c l i n o p t i l o l i t e e f f i c i e n c y d e c r e a s e s above 20 - 30 B V / h r , w h e r e a s 50 x 80 mesh l o s e s e f f i c i e n c y a b o v e 40 B V / h r . E x c e s s i v e head l o s s e s c an o c c u r i f t h e s u s p e n d e d s o l i d s c o n c e n t r a t i o n o f t h e i n f l u e n t i s g r e a t e r t h a n 35 mg/1-I n f l u e n t r~ C l i n o p t i l o l i t * Bed R egenerant Recovery I Ammonia, N i t r o g e n Gas, or Ammonia S o l -u t i o n E f f l u e n t Figure 31 Selective Ion Exchange Flow Diagram 4 83 S u s p e n d e d s o l i d s a r e r e m o v e d by p r e t r e a t m e n t . When a h i g h d e g r e e o f p r e t r e a t m e n t i s u s e d , t h e bed d e p t h i s u s u a l l y a b o u t 4 f e e t 4 8 . 2 .6 A i r S t r i p p i n g In a i r s t r i p p i n g , ammonium i o n i s c o n v e r t e d by pH a d j u s t m e n t , t o a m m o n i a , w h i c h i s r e l e a s e d t o t h e a t m o s p h e r e by s t r i p p i n g ( E q u a t i o n 2 - 1 9 ) . N H 4 + NH g + H + ( 2 - 1 9 ) A t pH 10 . 5 t o 1 1 . 5 v i r t u a l l y a l l o f t h e ammonium can be c o n -v e r t e d t o NH^ g a s . L ime i s u s ed t o i n c r e a s e t h e pH. T e m p e r a t u r e i s a c r i t i c a l f a c t o r i n s t r i p p i n g t o w e r d e s i g n . A t 20°C a 90 - 95% ammonia r e m o v a l i s p o s s i b l e , w h e r e a s , a t 10°C t h e p r a c t i c a l e f f i c i e n c y i s o n l y 75% . Da t a o v e r a w i d e r a n g e o f a i r t o w a t e r f l o w s , i n d i c a t e s a 30% d r o p i n e f f i c i e n c y 49 a t 5 C c o m p a r e d t o 2 2 . 2 ° C Due t o i c e f o r m a t i o n , a s t r i p p i n g t o w e r must be s h u t down i n f r e e z i n g w e a t h e r . H e a t i n g t h e s t r i p p i n g a i r i s u s u a l l y i m p r a c t i c a l . Ammonia can be r e l e a s e d f r o m s t r i p p i n g ponds o p e r a t e d a t h i g h pH w i t h s u r f a c e a g i t a t i o n . A t L a k e T a h o e , t h e pond c o n -t e n t s a r e r e c y c l e d 4 - 1 3 t i m e s by pump ing t h r o u g h v e r t i c a l s p r a y n o z z l e s i n t o t h e a i r above t h e p o n d s . A min imum o f 37% o f t h e ammonia was f o u n d t o be r emoved i n c o l d w e a t h e r . B r e a k p o i n t c h l o r i n a t i o n c o u l d be added t o i n c r e a s e ammonia r e m o v a l e f f i c i e n c y . P r i o r h y d r o l y s i s o f u r e a i s r e q u i r e d f o r a i r s t r i p p i n g . An h y d r o l y s i s pond may be more e f f e c t i v e t h a n a b i o l o g i c a l r e -a c t o r s y s t e m . The u r e a w a s t e w o u l d be added t o t h e d i r t pond and m i x e d s u c h t h a t s o i l w o u l d c o n t a c t t h e u r e a . V e r y l a r g e 84 amoun t s o f power w o u l d be r e q u i r e d t o keep t h e s o i l i n s u s -p e n s i o n . U r e a s e : i n t h e s o i l w o u l d i n d u c e h y d r o l y s i s . T h i s pond w o u l d a l s o a c t as an a i r s t r i p p i n g p o n d , r e l e a s i n g ammonia t o t h e a t m o s p h e r e . T h r e e e n v i r o n m e n t a l p r o b l e m s mus t be c o n s i d e r e d i n an ammonia s t r i p p i n g p r o c e s s . T h e s e a r e : a i r p o l l u t i o n , w a s h o u t o f ammonia f r o m t h e a t m o s p h e r e , and n o i s e . The o d o r 3 t h r e s h o l d o f ammonia i s 35mg/m , w h i l e e y e , n o s e , and t h r o a t 3 i r r i t a t i o n o c c u r s a t 2 8 0 - 4 9 0 mg/m . P l a n t s can be a f f e c t e d a t 3 c o n c e n t r a t i o n s o f 700 mg/m and human o r a n i m a l t o x i c i t y may 3 o c c u r a t 1 7 0 0 - 4 5 0 0 mg/m.. T y p i c a l c o n c e n t r a t i o n s o f a i r d i s -3 50 c h a r g e d f r o m an ammonia s t r i p p i n g t o w e r i s a r o u n d 6 mg/m Data f r o m O range C o u n t y C a l i f o r n i a i n d i c a t e s t h a t t h e c o n c e n t r a t i o n o f ammonia i n r a i n f a l l w o u l d . a p p r o a c h t h e 51 n a t u r a l b a c k g r o u n d l e v e l s w i t h i n 1 6 , 0 0 0 f t o f t h e t o w e r G e n e r a l l y , o n l y a s t r i p p i n g t o w e r i n p r o x i m i t y t o a l a k e o r r e s e r v o i r c o u l d - s i g n i f i c a n t l y a f f e c t t h e a q u a t i c e n v i r o n m e n t . N o i s e can o c c u r f r o m t h r e e s o u r c e s : m o t o r s , f a n s , and w a t e r . N o i s e l e v e l s can be r e d u c e d by a d e q u a t e c o n t r o l m e a s u r e s . 2 .7 C o l l e c t i o n - D i s p o s a l U r e a a p p l i e d t o a i r p o r t r u n w a y s can f o l l o w many p a t h s . I t may, r un o f f t h e r unway and be c a u g h t i n s u b s u r f a c e d r a i n s ; p e r c o l a t e t h r o u g h t h e r unway a s p h a l t and s eep i n t o t h e s o i l ; t r a v e l t o s u r f a c e w a t e r by o v e r l a n d f l o w ; o r , s eep i n t o t h e s o i l d i r e c t l y , a s a l i q u i d , o r , i n d i r e c t l y f r o m snow. U r e a 85 f o u n d i n s u b s u r f a c e d r a i n s , d i t c h e s a d j a c e n t t o t h e r u n w a y , and snow, may be c o l l e c t e d and d i s p o s e d o f . I t i s p o s s i b l e t o c o l l e c t u r e a r i c h w a s t e s t r e a m s i n ponds o r t a n k s . Snow, i m p r e g n a t e d w i t h u r e a , c o u l d be p l a c e d i n t a n k s o r i n an a r e a s u c h t h a t t h e l i q u i d snow m e l t w o u l d c o l -l e c t i n t h e m . Tank s o r ponds w o u l d be pumped o u t and t h e i r c o n -t e n t s d i s p o s e d o f o r t r e a t e d . E s t i m a t i o n o f t h e v o l u m e o f l i q u i d and i t s ' u r e a c o n c e n t r a t i o n i s d i f f i c u l t , as t h e s e p a r a m e t e r s a r e r e l a t e d t o p r e c i p i t a t i o n , q u a n t i t y o f u r e a d e - i c e r u s e d , and u r e a l o s t t o t h e s o i l , among o t h e r s . T h r e e t h i n g s can be done w i t h a c o l l e c t e d u r e a -r i c h l i q u i d , i t can b e : u s ed as a f e r t i l i z e r ( p o s s i b l y i n a g r e e n h o u s e ) ; d i s c h a r g e d t o a s e c o n d a r y t r e a t m e n t p l a n t ; o r , c o m b i n e d w i t h o t h e r f o o d s f o r c o n s u m p t i o n by r u m i n a n t s . The p o s s i b i l i t y o f f e e d i n g u r e a t o a n i m a l s has been a s u b j e c t o f much i n t e r e s t . The N a t i o n a l Academy o f S c i e n c e s 52 has c o n s i d e r e d t h i s as a u r e a w a s t e s t r e a m d i s p o s a l method Ammonia i s t h e common d e n o m i n a t o r i n t h e u t i l i z a t i o n o f n o n - p r o t e i n n i t r o g e n ( N P N ) , o f w h i c h u r e a i s a t y p e , by r u m i n a n t s . Mos t rumen b a c t e r i a p r e f e r ammonia n i t r o g e n o v e r t h a t s u p p l i e d by p e p t i d e s and am ino a c i d s . Da ta have been g a t h e r e d f o r NPN f e d t o v a r i o u s t y p e s o f a n i m a l s . F o r b e e f c a t t l e , p a s t e v i d e n c e i n d i c a t e s t h a t a u n i t o f u r e a n i t r o g e n mos t o f t e n has n o t been e q u i v a l e n t i n 86 f e e d i n g v a l u e t o a u n i t o f s u p p l e m e n t a l p r o t e i n n i t r o g e n . In d a i r y c a t t l e s t u d i e s , whe re u r e a p r o v i d e d a l l t h e d i e t a r y n i t r o g e n , r a t e s o f g r o w t h and m i l k p r o d u c t i o n were o n l y 65% o f o p t i m u m . Two m a j o r f a c t o r s a r e r e l a t e d t o u r e a u s a ge by r u m i -n a n t s : 1) a c c e p t a n c e o f u r e a - c o n t a i n i n g d i e t s 2) e f f e c t i v e u t i l i z a t i o n o f t h e consumed d i e t s . U rea can s e r v e as a u s e f u l s o u r c e o f n i t r o g e n i n p r a c t i c a l s heep d i e t s . The b e n e f i c i a l use o f NPN f o r d h i c k s and l a y i n g hens has n o t been d e m o n s t r a t e d . NPN c a n n o t be g i v e n t o s w i n e t o any a p p r e c i a b l e e x t e n t . H o r s e s have a g r e a t e r c a p a c i t y t o u t i l i z e NPN t h a n c h i c k e n s o r s w i n e , b u t , t h e e f f i c i e n c y o f n i t r o g e n u t i l i z a t i o n f r o m NPN i s c o n s i d e r a b l y l e s s t h a n t h a t o f n i t r o g e n f r o m i n t a c t p r o t e i n . " To a n s w e r t h e q u e s t i o n 'How much NPN can be added t o t h e d i e t o f a r u m i n a n t ? ' , i t w i l l be n e c e s s a r y t o a s k : a) What i s t h e l e v e l o f p r o t e i n i n t h e b a s a l d i e t r e l a t i v e t o t h e a n i m a l ' s r e q u i r e m e n t ? b) What i s t h e e n e r g y l e v e l ( s o l u b l e o r a v a i l a b l e c a r b o h y d r a t e ) i n t h e b a s a l d i e t ? c ) What l e v e l o f s o l u b l e n i t r o g e n i s i n t h e b a s a l d i e t ? d) I s t h e l e v e l o f o t h e r d i e t a r y . compo.nents ( e s p e c i a l l y r e q u i r e d m i n e r a l e l e m e n t s ) h i g h enough t o s u s t a i n maximum rumen m i c r o b i a l g r o w t h ? e ) What f e e d i n g s y s t e m w i l l be u s ed ? f ) What i s t h e e x p e c t e d l e v e l o f i n t a k e ? g) Does t h e g r o w t h o r p r o d u c t i o n r e q u i r e m e n t f o r a m i n o , a c i d s e x c e e d t h e c a p a c i t y o f rumen m i c r o b i a l s y n t h e s i s so t h a t some rumen b y p a s s o f n a t u r a l p r o t e i n i s n e e d e d ? " 5 3 8 7 3. C o n c l u s i o n s The e f f e c t i v e n e s s o f u r e a f o r i c e r e m o v a l f r o m a i r p o r t r u n w a y s has been w e l l d o c u m e n t e d , b u t , - i t s e n v i r o n -m e n t a l i m p a c t has n o t . Of t h e p o t e n t i a l e n v i r o n m e n t a l p r o b -l e m s , e u t r o p h i c a t i o n o f l a k e s i s o f t h e mos t c o n c e r n i n B r i t i s h C o l u m b i a . U r e a N i t r o g e n S o i l P a t h w a y s Mo s t o f t h e a p p l i e d u r e a d e - i c e r c o n t a c t s s o i l a t some t i m e . U r e a w h i c h p e r c o l a t e s i n t o s o i l w o u l d be c h e m i c a l l y a l t e r e d . 1. S o i l u r e a s e w o u l d be a c t i v e a t a i r p o r t w i n t e r t e m p e r a -t u r e s , b u t c o m p l e t e h y d r o l y s i s o f t h e a p p l i e d u r e a c o u l d t a k e s e v e r a l months a t t h e s e l ow t e m p e r a t u r e s . U r e a w h i c h p e r c o -l a t e s i n t o s o i l w o u l d n o t be e x p e c t e d t o r e a c h g r o u n d o r s u r f a c e w a t e r s i n an u n a l t e r e d f o r m . 2. Ammonia v o l a t i l i z a t i o n and ammonium p l a n t u p t a k e r a t e s w o u l d n o t be e x p e c t e d t o be s i g n i f i c a n t a t l ow t e m p e r a t u r e s . H o w e v e r , u r e a a p p l i e d i n t h e w i n t e r on a r unway may v o l a t i 1 i z e as ammonia o r be a v a i l a b l e f o r c r o p s as ammonium i o n (or n i t r a t e ) i n s p r i n g . 3. H y d r o l y s i s o f u r e a c a u s e s a l o c a l i z e d i n c r e a s e i n s o i l p H , w h i c h f a v o u r s ammonium f i x a t i o n on c l a y s . H o w e v e r , t h e r a t i o o f ammonia t o ammonium i s g o v e r n e d by p H , w i t h h i g h pH f a v o u r i n g ammon ia . The h y d r o l y s i s o f u r e a w o u l d r e s u l t i n a l a r g e p r o p o r t i o n o f ammonia, (a s m a l l amount o f w h i c h w o u l d v o l a t i l i z e ) , and a s m a l l p r o p o r t i o n o f ammonium i o n w h i c h , 88 i n s o i l s w i t h a l a r g e c l a y c o n t e n t , w o u l d be h e l d , p e r m a n e n t l y o r t e m p o r a r i l y , by t h e c l a y p a r t i c l e s ( ( a n d o r g a n i c m a t t e r ) . Ammonia m o v i n g away f r o m t h e a r e a o f h y d r o l y s i s w o u l d e n c o u n t e r l o w e r pH s o i l a n d , t h e r e f o r e some ammonia w o u l d be c o n v e r t e d t o ammonium i o n , w h i c h c o u l d be r e t a i n e d i n a v a i l a b l e e x c h a n g e -a b l e f o r m o r f i x e d i n l e s s a v a i l a b l e p o s i t i o n s . 4. N i t r i f i c a t i o n w o u l d n o t o c c u r a t f r e e z i n g t e m p e r a t u r e s , b u t s i n c e h y d r o l y s i s may t a k e s e v e r a l m o n t h s , t h e ammonia may be a v a i l a b l e f o r t h e n i t r i f i e r o r g a n i s m s i n s p r i n g . N i t r i -f i c a t i o n o f t h i s ammonia c o u l d o c c u r . ^ 5. R a t e s o f d e n i t r i f i c a t i o n w o u l d n o t be e x p e c t e d t o be s i g n i f i c a n t a t l ow t e m p e r a t u r e s . L o s s o f n i t r o g e n f r o m s o i l by t h i s p a t h w a y , w o u l d n o t be e x p e c t e d . 6. U r e a i n s u b s u r f a c e d r a i n s and d r a i n a g e d i t c h e s may f l o w u n a l t e r e d t o s u r f a c e w a t e r s , i f t h e r e i s l i t t l e s o i l c o n t a c t . On f r o z e n s o i l s , u r e a i n t h e o v e r l a n d f l o w c o u l d r e a c h s u r f a c e w a t e r s u n a l t e r e d . An i n c r e a s e i n u r e a c o n c e n t r a t i o n o f s u r f a c e w a t e r s c o u l d o c c u r s oon a f t e r u r e a a p p l i c a t i o n . An i n c r e a s e i n n i t r a t e o f g r o u n d w a t e r c o u l d t a k e s e v e r a l m o n t h s , d e p e n d i n g upon c l i m a t i c and s o i l c o n d i t i o n s . N i t r a t e i s t h e n i t r o g e n f o r m , f r o m u r e a d e - i c e r , o f most c o n c e r n as a p o l l u t a n t o f g r o u n d w a t e r s . I t c an a l s o r e a c h s u r f a c e w a t e r s . As s u c h n i t r a t e c o n c e n t r a t i o n s o f e n v i r o n -m e n t a l l y s e n s i t i v e w a t e r s a r o u n d a i r p o r t s s h o u l d be m o n i t o r e d . The u r e a c o n c e n t r a t i o n o f s u r f a c e w a t e r s s h o u l d a l s o be m o n i -t o r e d . 89 M i n i m i z i n g t h e E n v i r o n m e n t a l I m p a c t A) S o i l and P l a n t T r e a t m e n t F o r s o i l and p l a n t s t o a c t as a u r e a c o n t r o l p r o c e s s , t h e q u a n t i t y o f n i t r a t e l e a c h e d t o s u r f a c e w a t e r s must be l o w . T h i s can be a c h i e v e d , by i n c r e a s i n g : a ) NH^ v o l a t i 1 i z a t i on b) NH + c l a y f i x a t i o n c ) N H d p l a n t u p t a k e d) N O J p l a n t u p t a k e e) d e n i t r i f i c a t i o n O r , by d e c r e a s i n g : f ) n i t r i f i c a t i o n 1. P r a c t i c a l l y , l i t t l e can be done t o i n c r e a s e d e n i t r i f i c a t i o n and v o l a t i l i z a t i o n , o r d e c r e a s e n i t r i f i c a t i o n a t an a i r p o r t * 2. Ammonium c l a y f i x a t i o n can be i n c r e a s e d by t h e a d d i t i o n o f c l a y t o s o i l s a d j a c e n t t o t h e r u n w a y s . As t h e h y d r o l y s i s o f u r e a makes more ammonium a v a i l a b l e , l e s s w o u l d be f i x e d , as t h e s o i l has a l i m i t e d c a p a c i t y f o r f i x a t i o n . A l s o , n o t a l l t h e ammonium i s h e l d p e r m a n e n t l y , and some may be r e l e a s e d a t a l a t e r d a t e . E x c a v a t i o n o f n a t u r a l s o i l and r e p l a c e m e n t w i t h h i g h c l a y c o n t e n t s o i l s w o u l d be e x p e n s i v e . E x c a v a t i o n w o u l d be n e c e s s a r y t o a t l e a s t t h e 30 m e t e r d i s t a n c e f r o m t h e runway i % w h i c h u r e a i m p r e g n a t e d snow i s t h r o w n by t h e a i r p o r t snow r e m o v a l e q u i p m e n t . * [ Appa ren t l y , n i t r i f i c a t i o n i n h i b i t o r s are commercia l ly a v a i l a b l e . Before use, the environmental impact of these must be cons idered. 90 The a d d i t i o n o f c l a y t o s o i l s c a u s e s some s e r i o u s p r o b l e m s . S o i l s w i t h a h i g h c l a y c o n t e n t have g r e a t e r o v e r l a n d f l o w , a n d , t h e r e f o r e , u r e a w o u l d r e a c h s u r -f a c e w a t e r s . A l s o , c l a y e y s o i l s r e s t r i c t t h e g r o w t h o f c r o p s , h a m p e r i n g t h i s p a t h w a y f o r r e m o v a l o f n i t r o g e n f r o m s o i l . The d i s a d v a n t a g e s f o r n i t r o g e n c o n t r o l by t h e a d d i t i o n o f c l a y t o s o i l s , e x c e e d t h e a d v a n t a g e s . 3. R e p l a c e m e n t o f n a t u r a l c r o p s a d j a c e n t t o t h e r u n w a y , w i t h h i g h n i t r o g e n u p t a k e c r o p s , i s t h e b e s t means o f u t i l i z i n g s o i l and p l a n t s t o p r e v e n t n i t r o g e n r e l e a s e t o w a t e r s . G r a s s i s p o s s i b l y t h e mos t s u i t a b l e c r o p w h i c h i s p e r m i t t e d . b y MOT g u i d e l i n e s a d j a c e n t t o t h e r u n w a y . I t s c a p a c i t y t o a b s o r b n i t r o g e n f r o m s o i l 1 g i s m o d e r a t e l y h i g h ( t o 120 l b . N / a c r e ). T h e r e i s no n e t r e m o v a l o f n i t r o g e n f r o m t h e s y s t e m i f t h e c r o p i s c u t and a l l o w e d t o decompose on t h e s o i l s u r f a c e . The c r o p mus t t h e r e f o r e be r emoved f r o m t h e a i r p o r t . The y i e l d o f g r a s s , r e l a t i v e t o o t h e r c r o p s p e r m i t t e d by MOT, i s l ow ( a b o u t 3 B U / A ) , and h a r v e s t e d as h a y , , i t i s r e a d i l y m a r k e t a b l e . P e n s a c o l a B a h i a g r a s s seem to be o f / s p e c i a l me r i t s i n c e f i e l d s o f t h i s g r a s s a f f o r d l o w e r q u a n t i t i e s o f l e a c h e d . n i t r o g e n t h a n some o t h e r g r a s s t y p e s . ( 0 . 5 l b N/A i n d r a i n a g e ) . However, t h i s grass type w i l l not su r v i ve i n northern temperate c l i m a t e s . 91 A p p r o x i m a t e l y 1 0 - 2 5 % o f t h e a p p l i e d n i t r o g e n can be a s sumed t o be l e a c h e d f r o m g r o w i n g c r o p f i e l d s ; s o i l and p l a n t s c o u l d be 7 5 - 90% e f f i c i e n t i n r e d u c i n g n i t r o g e n l o s s t o g r o u n d and s u r f a c e w a t e r s . Management o f t h e p l a n t s a d j a c e n t t o t h e r unway i s a v e r y i m -p o r t a n t c o m p o n e n t i n t h e t r e a t m e n t p r o c e s s . To e n s u r e maximum c r o p u p t a k e o f n i t r o g e n : a) T h e r e must be an a c t i v e l y g r o w i n g c r o p . b) The u r e a i m p r e g n a t e d snow and s l u s h s h o u l d be d i s t r i b u t e d o v e r a l a r g e s o i l s u r f a c e a r e a . c ) The c r o p s must be c l i p p e d and t h e c u t t i n g s r emoved f r o m t h e a i r p o r t p r o p e r t y i n t h e summer. B) V o l a t i l i z a t i o n o f Ammonia by U r e a s e on A i r p o r t Runways 1. The n a t u r a l e n z y m a t i c a c t i v i t y o f an a i r p o r t r unway a t room t e m p e r a t u r e cau sed l e s s t h a n 1% o f t h e a p p l i e d u r e a t o be h y d r o l y z e d a f t e r 90 m i n u t e s , as m e a s u r e d i n t h e l a b . B e c a u s e t h e r e was r e s i d u a l ammonia on t h e r unway s a m p l e s , t h e a c t u a l p e r c e n t a g e o f u r e a h y d r o l y z e d i s l o w e r t h a n 0 . 5 % . The . - . na tu ra l h y d r o l y s i s r a t e on a r unway s u r f a c e , t h e r e f o r e , must be i n s i g n i f i c a n t u n d e r w i n t e r a i r p o r t c o n d i t i o n s . 92 2. H y d r o l y s i s was f o u n d t o be l i n e a r l y p r o p o r t i o n a l t o t e m p e r a t u r e and u r e a s e c o n c e n t r a t i o n . T e s t s w i t h d i f f e r e n t r a t e s o f u r e a a p p l i c a t i o n c o n f i r m e d t h i s . 3. U s i n g 3 t y p e s o f u r e a , i t was f o u n d t h a t , c h a n g i n g t h e t y p e o f u r e a o r p e l l e t s i z e , doe s n o t a f f e c t t h e q u a n t i t y o f u r e a h y d r o l y z e d . 4. J u s t i n c r e a s i n g s o l a r r a d i a t i o n i n c r e a s e d t h e r a t e o f h y d r o l y s i s . S o l a r r a d i a t i o n p r o v i d e s t h e a c t i v a t i o n e n e r g y and m e l t s t h e i c e t o w a t e r - b o t h a r e n e e d e d f o r h y d r o l y s i s . 5. A t t e m p t e d r e c o v e r y o f t h e m e l t w a t e r by t i p p i n g t h e p y r e x mode l i s n o t s a t i s f a c t o r y . P i p e t t e s p l a c e d i n t h e p e l l e t d r o p h o l e , and h o l e s b o r e d t h r o u g h t h e i c e , c o u l d g i v e b e t t e r r e s u l t s . 6. From a p r a c t i c a l and e c o n o m i c v i e w p o i n t , t h e a d d i t i o n o f u r e a s e t o an a i r p o r t r unway i n o r d e r t o i n d u c e ammonia v o l a t i l i z a t i o n i s i m p r a c t i c a l . L a b o r a t o r y g r a d e u r e a s e c o s t s a b o u t $1 p e r g r a m . A 500 mg, u r e a s e 2 p e r 720cm a p p l i c a t i o n c o r r e s p o n d s t o a c o s t o f $ 1 7 0 , 0 0 0 . f o r t h e a v e r a g e a i r p o r t r u n w a y . Even w i t h h i g h s o l a r r a d i a t i o n , l e s s t h a n 20% o f t h e a p p l i e d u r e a w o u l d be e x p e c t e d t o v o l a t i l i z e t o ammonia g a s . A d d i t i o n a l u r e a s e c o a t i n g s w o u l d a l s o be n e c e s s a r y t h r o u g h o u t t h e w i n t e r , as t h e enzyme w o u l d be r emoved by r a i n , w i n d , v e h i c l e w h e e l s , and i c e r e m o v a l . 93 The o d o r c a u s e d by a h i g h ammonia c o n c e n t r a -t i o n i n a i r may be u n a c c e p t a b l e a t an a i r p o r t . C) R e d u c t i o n o f U r e a Use R e d u c i n g t h e q u a n t i t y o f u r e a u sed a t an a i r p o r t w o u l d n o t o n l y r e d u c e t h e e n v i r o n m e n t a l i m p a c t , b u t , a l s o r e d u c e t h e c o s t o f i c e c o n t r o l . 1. I f t h e u r e a - E r l i c h r e a g e n t a u r a s i z e can be p o s i t i v e l y c o r r e l a t e d w i t h t h e e a s e o f i c e r e m o v a l , t h e n t h e S h e r r i t t G o r d o n M i n e s - I n d u s t r i a l G r ade p e l l e t s a r e more e f f e c t i v e as a d e - i c e r , by w e i g h t , t h a n e i t h e r o f t h e two Com inco g r a d e s u n d e r t h e t e s t c o n d i t i o n s . The g r e a t e r a u r a s i z e o f t h e S h e r r i t t Go rdon M i n e s u r e a i s f e l t t o be due t o i t s p e l l e t s i z e and n o t i t s a n t i - c a k i n g a d d i t i v e . C o m p a r i n g t h e a u r a s i z e , on a w e i g h t b a s i s , f o r t h e two Cominco G r a d e s , shows t h a t l a r g e r p e l l e t s a r e l e s s e f f e c t i v e t h a n s m a l l e r p e l l e t s , f o r d e - i c i n g . 2. A h o l l o w on an a i r p o r t r unway w o u l d a c c u m u l a t e u r e a , w h e r e a s , a dome w o u l d t r a n s f e r t h e s o l u t i o n t o l o w e r a r e a s . The i c e pa vemen t bond w o u l d be b r o k e n i n t h e l o w a r e a s , b u t , may n o t be i n t h e domed a r e a s . A smooth r u n w a y s u r f a c e w o u l d be more d e s i r a b l e t h a n a r o u g h s u r f a c e f r o m a i c e c o n t r o l p o i n t o f v i e w . 3. N e i t h e r t h e SGM-IG n o r t h e C- IG p e l l e t s have s i g n i f i c a n t d e - i c i n g c a p a b i l i t y a f t e r 20 m i n u t e s f r o m a p p l i c a t i o n . From an a i r p o r t o p e r a t i o n a l s t a n d p o i n t , 94 i f a f t e r 20 m i n u t e s an a p p l i c a t i o n o f SGM-IG o r C - IG p e l l e t s h a s . n o t a c h i e v e d s u f f i c i e n t d e - i c i n g , a s e c o n d a p p l i c a t i o n o f u r e a w o u l d be r e q u i r e d . The C-FG p e l l e t s have s i g n i f i c a n t d e - i c i n g c a p a b i l i t y a f t e r 90 m i n u t e s . In s p i t e o f t h i s , t h e C-FG p e l l e t s a r e n o t more s u i t a b l e f o r d e - i c i n g , s i n c e t h e a r e a o f m e l t a f t e r 90 m i n u t e s ( a s shown by t h e a u r a ) , i s s m a l l c o m p a r e d t o t h a t o f t h e o t h e r two t y p e s o f u r e a . The SGM-IG p e l l e t s a r e t h e most s u i t a b l e . D) B i o l o g i c a l N i t r i f i c a t i o n - D e n i t r i f i c a t i o n B i o l o g i c a l n i t r i f i c a t i o n .can t r e a t l i m i t e d q u a n t i t i e s o f u r e a d i r e c t l y , w i t h o u t t h e h y d r o l y s i s p r e t r e a t m e n t . In o r d e r t o t r e a t t h e r e s u l t i n g N O ^ - , d e - n i t r i f i c a t i o n must f o l l o w . The o v e r a l l p r o c e s s i s i m p r a c t i c a l b e c a u s e o f c o s t and t h e n e c e s s i t y f o r u r e a f e e d i n summer, a n d , a t t i m e s , i n t h e w i n t e r . A t l o w l i q u i d t e m p e r a t u r e s , t h e t a n k a g e r e q u i r e m e n t s f o r b i o l o g i c a l p r o c e s s e s a r e l a r g e . The l i q u i d c o u l d be h e a t e d , b u t , t h i s w o u l d be an a d d i t i o n a l c o s t . E) B r e a k p o i n t C h l o r i n a t i o n B r e a k p o i n t c h l o r i n a t i o n i s a p p l i c a b l e t o t h e N H ^ - N H ^ f o r m s o n l y . H y d r o l y s i s o f u r e a by c h e m i c a l means i s i n s i g n i f i c a n t b e l o w 2 5 ° C , and t h e r e -f o r e , i s n o t s u i t a b l e f o r w i n t e r a i r p o r t c o n d i t i o n s . B i o l o g i c a l h y d r o l y s i s i n a r e a c t o r i s an u n p r o v e n p r o c e s s - d e v e l o p m e n t and i m p l e m e n t a t i o n w o u l d be e x -95 p e n s i v e . S p o r a d i c f e e d i s a l s o a m a j o r p r o b l e m w i t h an h y d r o l y s i s b i o l o g i c a l r e a c t o r . F) S e l e c t i v e Ion E x c h a n g e S e l e c t i v e i o n e x c h a n g e s y s t e m s can be o p e r a t e d s p o r a d i c a l l y and t e m p e r a t u r e does n o t have a m a j o r e f f e c t on p r o c e s s e f f i c i e n c y . D i s p o s a l o r t r e a t m e n t o f t h e c o n t a m i n a t e d b r i n e s o l u t i o n s may be c o s t l y . The e f f i c i e n c y o f s e l e c t i v e i o n e x c h a n g e r e m o v a l o f u r e a n i t r o g e n i s l o w , and t h e r e f o r e , t h e u r e a must be c o n v e r t e d t o ammonia p r i o r t o t r e a t m e n t . A h y d r o l y s i s r e a c t o r w o u l d a l s o be u sed i n t h i s s y s t e m . G) A i r S t r i p p i n g A i r s t r i p p i n g w o u l d p r o b a b l y be c o s t p r o h i b i t i v e i f n o t f o r t h e p o s s i b i l i t y o f u s i n g p o n d s . T h e s e w o u l d p e r f o r m b o t h u r e a h y d r o l y s i s and ammonia v o l a t i l i z a t i o n . The e f f i c i e n c y o f n i t r o g e n r e m o v a l w o u l d be l ow a t n e a r f r e e z i n g t e m p e r a t u r e s . Any n i t r o g e n f o r m s l o s t t h r o u g h s e e p a g e may be p r e v e n t e d f r o m l e a c h i n g t o g r o u n d w a t e r by s o i l r e a c t i o n s . The o d o r c a u s e d by ammonia i n t h e a i r c o u l d be a s e r i o u s p r o b l e m . H) C o l l e c t i o n - D i s p o s a l C o l l e c t i o n o f u r e a - r i c h l i q u i d and d i s p o s a l as f e r t i l i z e r , o r as f o o d f o r r u m i n a n t s , i s a p p l i c a b l e t o o n l y s m a l l w a s t e v o l u m e s b e c a u s e o f t h e c o s t o f c o l l e c t i o n t a n k s and t r a n s p o r t a t i o n o f l i q u i d . S i n c e 96 l a r g e v o l u m e s o f d i l u t e s o l u t i o n s w o u l d have t o be d i s p o s e d o f , t h e s e d i s p o s a l me thod s a r e n o t s a t i s -f a c t o r y . T r e a t m e n t o f u r e a s o l u t i o n s by s e c o n d a r y t r e a t -ment p l a n t s may be p o s s i b l e u n d e r s p e c i a l c i r c u m s t a n c e s Mo s t a i r p o r t s do have s ewe r c o n n e c t i o n s , b u t , n o t a l l c i t i e s have s e c o n d a r y sewage t r e a t m e n t p l a n t s . L a r g e v o l u m e s o f d i l u t e s o l u t i o n s can a l s o a d v e r s e l y a f f e c t s e c o n d a r y t r e a t m e n t p l a n t ' s p e r f o r m a n c e . I ) R a t i n g B e f o r e any o t h e r me thod f o r m i n i m i z i n g t h e e n v i r o n m e n t a l i m p a c t o f u r e a , t h e p o s s i b i l i t y o f r e d u c i n g t h e q u a n t i t y o f u r e a u s e d , s h o u l d be c o n -s i d e r e d . The o t h e r me thod s may be r a t e d , f r o m a c o s t , e f f i c i e n t , and p r a c t i c a l p o i n t o f v i e w , f r o m mos t e f f e c t i v e t o l e a s t , as f o l l o w s : 1. S o i l and P l a n t T r e a t m e n t 2. A i r S t r i p p i n g 3. C o l l e c t i o n - D i s p o s a l 4. S e l e c t i v e Ion E x c h a n g e 5. B r e a k p o i n t C h l o r i n a t i o n 6. B i o l o g i c a l N i t r i f i c a t i o n - D e n i t r i f i c a t i o n 7. V o l a t i l i z a t i o n o f Ammonia by U r e a s e on an A i r p o r t Runway. • i 4. F u r t h e r R e s e a r c h On t h e b a s i s o f t h i s s t u d y , f u r t h e r r e s e a r c h i s i n d i c a t e d . S i n c e c o n t r o l o f u r e a d e - i c e r t h r o u g h v o l a t i l -i z a t i o n o f ammonia on an a i r p o r t r unway i s b o t h i n e f f i c i e n t and c o s t l y , f u r t h e r s t u d y i n t h i s a r e a i s n o t r e c o m m e n d e d . 97 U r e a w a s t e s t r e a m t r e a t m e n t m e t h o d s s u c h a s , n i t r i f i c a t i o n -d e n i t r i f i c a t i o n , b r e a k p o i n t c h i o r i n a t i o n , s e l e c t i v e i o n e x c h a n g e , a i r s t r i p p i n g , c o l l e c t i o n a n d d i s p o s a l , a r e p r o b a b l y t o o e x p e n s i v e a n d s u b j e c t t o t o o many o p e r a t i o n a l p r o b l e m s t o be e f f e c t i v e . O f t h e s e t r e a t m e n t m e t h o d s , p r o b a b l y o n l y a i r s t r i p p i n g a n d c o l 1 e c t i o n - d i s p o s a 1 w a r r a n t f u r t h e r r e s e a r c h . B e f o r e a d e t a i l e d c o s t a n d e f f i c i e n c y s t u d y c a n be d o n e , d a t a c o n c e r n i n g l i q u i d v o l u m e s a n d u r e a c o n c e n t r a t i o n s o f t h e w a s t e s t r e a m m u s t f i r s t be g a i n e d . S o i l s e e m s t o be t h e l e a s t c o s t l y a n d o n e o f t h e m o s t e f f i c i e n t t r e a t m e n t m e d i u m s f o r a u r e a w a s t e s t r e a m . F u t u r e s t u d y i s r e q u i r e d t o d e l i n e a t e t h e q u a n t i t y o f u r e a t h a t c a n go i n t o t h e v a r i o u s s o i l r e a c t i o n p a t h w a y s . T e s t p l o t s , 1 5 u s i n g N i s o t o p e c o u l d be an e x c e l l e n t way o f f o l l o w i n g u r e a d e - i c e r . The q u a n t i t y o f u r e a a n d n i t r a t e w h i c h r e a c h e s s u r f a c e w a t e r s a r e t h e m o s t i m p o r t a n t p a r a m e t e r s t o i d e n t i f y . T h e p o s s i b i l i t y o f s e l e c t i n g a c r o p t o c o n t r o l u r e a d e - i c e r , t h a t i s , t o m a x i m i z e n i t r o g e n u p t a k e , s e e m s q u i t e f e a s i b l e . T e s t p l o t s u s i n g d i f f e r e n t c r o p s c o u l d be p l a n t e d a d j a c e n t t o a i r p o r t r u n w a y s . S i n c e s o i l t y p e s , p r e c i p i t a t i o n l e v e l s , l e n g t h o f g r o w i n g s e a s o n , a n d t e m p e r a t u r e d e t e r m i n e p l a n t t y p e s , o n e c r o p may n o t be s u i t a b l e f o r u r e a c o n t r o l a t a l l C a n a d i a n a i r p o r t s . I t may be n e . c e s s a r y t o g&mend s o i l s w i t h l i m e , p o t a s s i u m , p h o s p h o r u s , and pe rhap s o t h e r p l a n t n u t r i e n t s t o improve and encou rage g rowth o f c r o p s f o r f a l l u t i l i z a t i o n o f n i t r o g e n f r om u rea used f o r d e - i c i n g p u r p o s e s . 98 R e d u c t i o n o f U r e a Use L a b o r a t o r y R e s e a r c h I d e a l l y , c h a r t s c o u l d be d e v e l o p e d s u c h t h a t a i r p o r t m a n a g e r s c o u l d s e l e c t t h e u r e a a p p l i c a t i o n r a t e k n o w i n g : t h e p a v e m e n t t e m p e r a t u r e , a m b i e n t a i r t e m p e r a t u r e , r a t e o f s o l a r i n s o l a t i o n , and i c e t h i c k n e s s . S t u d y o f t h e f o l l o w i n g t o p i c s w o u l d a i d i n t h e p r e p a r a t i o n o f t h e s e c h a r t s An u r e a i n d i c a t o r w o u l d be used t o i n v e s t i g a t e e a c h t o p i c . E h r l i c h r e a g e n t was f o u n d t o be s a t i s f a c t o r y , h o w e v e r , a d i f f e r e n t i n d i c a t o r may p r o d u c e a more v i s i b l e a u r a . 1. D e t e r m i n a t i o n o f t h e u r e a c o n c e n t r a t i o n g r a d i e n t a round^ t h e p e l l e t d r o p h o l e w o u l d p r o v i d e i n f o r m a t i o n a b o u t t h e u r e a - r i c h l i q u i d . S a m p l e s o f s o l u t i o n c o u l d be o b t a i n e d f r o m t h e u r e a p e l l e t . d r o p h o l e . S a m p l e s away f r o m t h e h o l e w o u l d be o b t a i n e d by b o r i n g t h r o u g h a t h i n i c e l a y e r . The i n d i c a t o r s o l u t i o n may be u sed t o d e t e r m i n e t h e u r e a c o n c e n t r a t i o n s i n some c a s e s . 2. The s i z e o f t h e u r e a s o l u t i o n l e n s u n d e r t h e i c e may be d e t e r m i n e d w i t h t h e a i d o f a c a s t . A t t e m p t s t o make c a s t s o f t h e u n d e r - s u r f a c e o f t h e i c e u s i n g wax and p l a s t e r o f p a r i s f a i l e d b e c a u s e t h e h e a t g i v e n o f f by t h e h a r d e n i n g wax and p l a s t e r , m e l t e d t h e i c e . A c o o l c l a y o r P l a s t i c i n e may w o r k . Of p a r t i c u l a r i n t e r e s t , w o u l d be s l o w r e l e a s e p e l l e t s . T h e s e c o a t e d p e l l e t s w o u l d be e x p e c t e d t o produce l a r g e r auras s i nce they would probably d e l i v e r more urea ( i n d i c a t e d by the aura) 99 t o t h e b o t t o m o f t h e d r o p h o l e t h a n c o n v e n t i o n a l p e l l e t s . In t h i s c a s e , t h e a r e a o f b r o k e n i c e - p a v e m e n t bond w o u l d be l a r g e r . C a s t s c o u l d be made o f i c e s u b j e c t e d t o t h i s u r e a . 3. The g r e a t e r a u r a g r o w t h p e r pound o f u r e a f o r t h e S h e r r i t t Go rdon M i n e s - I n d u s t r i a 1 G rade p e l l e t i s b e l i e v e d t o be due t o i t s p a r t i c l e s i z e and n o t t o t h e w h i t e m i n e r a l o i l c o n d i t i o n i n g a g e n t u s e d . A t e s t o f t h i s h y p o t h e s i s u s i n g an i n d i c a t o r r e a g e n t and two p e l l e t s o f t h e same d i a m e t e r -one w i t h m i n e r a l o i l , and one w i t h o u t , c o u l d be d o n e . 4. T h i s o p t i m i z a t i o n o f u r e a s t u d y u s ed o n l y one s e t o f 2 e n v i r o n m e n t a l c o n d i t i o n s - - 4 ° C , 0 . 9 0 kg/70 m u r e a , 5mm i c e and no s o l a r r a d i a t i o n . Work s h o u l d be done u n d e r d i f f e r e n t c o n d i t i o n s , s u c h as., t h e one s u s ed i n t h e v o l a t i l i z a t i o n o f u r e a on an a i r p o r t r unway r e s e a r c h . 5. Runway s u r f a c e s c o u l d be u sed - p a i n t e d w h i t e and a g r i d added f o r p h o t o g r a p h i c p u r p o s e s . The e f f e c t o f a i r p o r t r unway i r r e g u l a r i t i e s on a u r a g r o w t h and u r e a e f f e c t i v e n e s s s h o u l d be i n v e s t i g a t e d . 6. The c o r r e l a t i o n , i f a n y , b e t w e e n a u r a s i z e and e a s e o f i c e r e m o v a l i s v e r y i m p o r t a n t t o d e t e r m i n e . I f a p o s i t i v e c o r r e l a t i o n e x i s t s v a l i d c o n c l u s i o n s ba sed on t h e E h r l i c h a u r a may be d r a w n . A s p r i n g m o u n t e d s c r a p i n g b a r may be u sed ( F i g u r e 3 2 ) . The u n i t s h o u l d be b o l t e d t o a p i e c e o f r unway a s p h a l t r a t h e r t h a n a g l a s s o r m e t a l s u r f a c e , so t h a t t h e i c e - a s p h a l t bond w o u l d be d u p l i c a t e d e x a c t l y . Figure 32 ke Scraper Mechanism 101 To b e g i n t h e t e s t , t h e s c r a p i n g b a r s p r i n g s w o u l d be c o m p r e s s e d and t h e ba r h e l d i n p l a c e . The w a t e r r e t a i n i n g b a r w o u l d a l s o be i n s t a l l e d and t h e t e s t a r e a s h o u l d be c h e c k e d t o see t h a t i t i s w a t e r t i g h t . The w a t e r - i n d i c a t o r s o l u t i o n w o u l d be p o u r e d o n t o t h e f r o z e n s u r f a c e . A f t e r i c e f o r m a t i o n , t h e w a t e r r e t a i n i n g b a r w o u l d be r e m o v e d , t h e u r e a a p p l i e d , and t h e s c r a p i n g b a r r e l e a s e d . P h o t o g r a p h s o f t h e a u r a w o u l d be t a k e n u n t i l t h e scrap/in.g b a r r e m o v e d t h e i c e . Remova l o f t h e i c e w o u l d i n d i c a t e t h a t t h e i c e - a s p h a l t bond s t r e n g t h was l e s s t h a n t h e s c r a p i n g b a r f o r c e . The r e l a t i o n -s h i p be tween a u r a s i z e and e a s e o f i c e r e m o v a l w o u l d t h e n be d e t e r m i n e d . 7. P r e v i o u s r e s e a r c h c o n d u c t e d by MOT i n d i c a t e s t h a t dye c o a t e d u r e a p e l l e t s a r e more e f f e c t i v e d e - i c e r s t h a n w h i t e p e l l e t s . The e n e r g y a b s o r b i n g a b i l i t y o f b l a c k s u r f a c e s i s b e l i e v e d t o be r e s p o n s i b l e f o r t h i s . To t e s t t h e t h e o r y a s o l a r l amp and dye c o a t e d p e l l e t s c o u l d be u s e d . H o w e v e r , c a r e s h o u l d be t a k e n s i n c e t h e dye may i n t e r f e r e w i t h t h e u r e a i n d i c a t o r . The m e c h a n i c a l s c r a p i n g m e c h a n i s m c o u l d be u s ed t o t e s t t h e dye c o a t e d p e l l e t s ' e f f e c t i v e n e s s . A i r p o r t Runway R e s e a r c h T. ' A n t i - i c i n g i s d i f f i c u l t t o mode l i n t h e l a b o r a t o r y , w h e r e a s , d e - i c i n g i s r e l a t i v e l y s i m p l e . The i m p o r t a n t d e -i c i n g c o n d i t i o n s t o c o n s i d e r a r e : u r e a a p p l i c a t i o n r a t e , i c e t h i c k n e s s , and t e m p e r a t u r e . In a d d i t i o n t o t h e s e c o n -1 02 d i t i o n s , a mode l o f a n t i - i c i n g r e q u i r e s t h a t o t h e r f a c t o r s be c o n s i d e r e d : t h e c o n d i t i o n o f t h e a s p h a l t i c s u r f a c e p r i o r t o p e l l e t a d d i t i o n (a t h i n l a y e r o f w a t e r w i l l d i s s o l v e t h e p e l l e t ) ; t h e r a t e , t y p e , and t e m p e r a t u r e o f p r e c i p i t a t i o n ; t h e movement o f t h e p e l l e t s b e t w e e n t h e t i m e i t i s a p p l i e d and d i s s o l v e s (movement may be c a u s e d by w i n d ) ; and t h e e l a p s e d t i m e be tween u r e a a p p l i c a t i o n and a c t i o n . S i n c e a n t i - i c i n g i s t h e method o f u r e a a p p l i c a t i o n recommended by MOT, t h e p o s s i b i l i t y o f o p t i m i z i n g t h e u r e a t y p e and r a t e o f a p p l i c a t i o n - s h o u l d be i n v e s t i g a t e d . The r e s i d u a l e f f e c t o f u r e a i s t h e most i m p o r t a n t p a r a m e t e r t o q u a n t i f y . A t e s t p l o t on a s e c t i o n o f pavemen t may be t h e b e s t way t o model a n t i - i c i n g . The t h r e e t y p e s o f u r e a c o u l d be a p p l i e d i n s t r i p s and t h e r e l a t i v e a b i l i t y t o p r e v e n t i c e f o r m a t i o n be t e s t e d . 2. I t may be p o s s i b l e t o o p t i m i z e t h e u r e a d i s t r i b u t i o n . P e l l e t s may be p l a c e d more e v e n l y w i t h f e r t i l i z e r s p r e a d e r s t h a n s a n d s p r e a d e r s . T e s t s c o u l d be c o n d u c t e d a t a i r p o r t s u s i n g e a c h s p r e a d i n g m e t h o d . 103 L i t e r a t u r e C i t e d 1. B o n n a x , C l i f f o r d M. , C h e m i c a l E l i m i n a t i o n and  P r e v e n t i o n o f I c e on Runway s , A m e r i c a n A s s o c i a t i o n o f A i r p o r t E x e c u t i v e s , 1967 , p .4. 2. I b i d . , - p . 1 . 3. Snow Remova l and I c e C o n t r o l M a n u a l , A i r p o r t and C o n s t r u c t i o n S e r v i c e s , A i r p o r t F a c i l i t i e s B r a n c h , T r a n s p o r t C a n a d a , A k - 7 2 - 4 0 - 0 0 0 , 1 976 , p . l . 4 . C h e m i c a l I c e C o n t r o l E v a l u a t i o n P r o g r a m , A i r p o r t s and C o n s t r u c t i o n S e r v i c e s , M o b i l e S u p p o r t S e r v i c e s D i v i s i o n , 0-+tawa , 1972 , p . 1 8 . 5. I b i d . , p. 6. 6. U r e a f o r I c e P r e v e n t i o n and R e m o v a l , I m p e r i a l C h e m i c a l I n d u s t r i e s L i m i t e d - A g r i c u l t u r a l D i v i s o n , R e f . No. PAG/MU985, L o n d o n , E n g l a n d , 1 9 7 2 , p . 3 . 7. I b i d . , p . 4 . 8. I b i d . , p . 3 . 9. C h a n l e t t , E m i l T . , E n v i r o n m e n t a l P r o t e c t i o n , McGraw-H i l l Book Co.,.. New Y o r k , 1 973 , p. 81 . 10 . C a n a d i a n D r i n k i n g W a t e r S t a n d a r d s and O b j e c t i v e s  1 968 , The Department 'of Nat iona l Health and Wei f a re ,Ot tawa, 1969, p .14/ 1 1 . V a l l e n t y n e , J ohn R., The A l g a l B o w l - l a k e s and man, E n v i r o n m e n t C a n a d a , M i s c . S p e c . P u b ! . 2 2 , O t t a w a , 1 9 7 4 , p . 1 1 . 12 . P a u l s o n , K . N . , and K u r t z , L . T . , " L o c u s o f U r e a s e A c t i v i t y i n S o i l " , S o i 1 S c i . S o c . Am. P r o c . , ,1969 , V o l . .33, p.897. 1 3 . A l e x a n d e r , M. I n t r o d u c t i o n t o S o i l M i c r o b i o l o g y , J o h n W i l e y and S o n s , I n c . , New Y o r k and L o n d o n , 1 9 6 1 , p . 3 0 . 14 . B r e m n e r , J . 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