Chapter 18
Sulfur, Halogens, and Heavy Metals in Urban Summer Rainfall 1,3
2
2
S. Landsberger , S. J. Vermette , and J. J. Drake 1
Nuclear Reactor, McMaster University, Hamilton, Ontario L8S 4K1, Canada Department of Geography, McMaster University, Hamilton, Ontario L8S 4K1, Canada
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We have employed two multi-elemental techniques (INAA and ICP-AES) to determine sulphur, halogens and 14 other trace elements in urban summer rain fall. Quality control was assured using NBS reference materials. The overall accuracy and precision of these two methods makes possible the routine analysis of many environmentally important trace elements in acid rain related investigations. Enrichment factor calculations showed that several elements including S, Cu, Zn and Cr were abnormally enriched in the urban atmosphere. A comparison of three separate sites showed a strong gradient of metal deposition from the industrial to the out laying areas.
The s t u d y of p o l l u t a n t d e p o s i t i o n i n an u r b a n environment i s o f t e n r e p o r t e d from b u l k r a i n samples (1) w i t h o u t due c o n s i d e r a t i o n b e i n g g i v e n to the i n d i v i d u a l c o n t r i b u t i o n s o f wet and d r y d e p o s i t i o n . The i n t e r p r e t a t i o n and u t i l i t y o f e l e m e n t a l c o n c e n t r a t i o n s d e r i v e d from b u l k samples i s r e s t r i c t i v e and o f l i m i t e d use due to t h e i r dependence on time o f exposure to d r y d e p o s i t i o n , v a r y i n g volumes of c o l l e c t e d r a i n w a t e r and wind d i r e c t i o n , a l l o f which a r e o f t e n not r e p o r t e d . The i n t e n t o f t h i s paper i s to r e p o r t w e t - p e r i o d e l e m e n t a l c o n c e n t r a t i o n s f o r 18 t a r g e t e d t r a c e elements i n the summer r a i n s o f the v e r y heavy i n d u s t r i a l i z e d c i t y o f H a m i l t o n , O n t a r i o . Samples were c o l l e c t e d from t h r e e r a i n e v e n t s i n the summer o f 1985 and a l t h o u g h the s a m p l i n g p e r i o d r e p r e s e n t s a s m a l l f r a c t i o n of t o t a l summer r a i n s , u s e f u l e n v i r o n m e n t a l i n t e r p r e t a t i o n s can be made.
^Current address: Department of Nuclear Engineering, University of Illinois, 214 Nuclear Engineering Laboratory, 103 South Goodwin Ave., Urbana, IL 61801
0097-6156/87/0349-0213$06.00/0 © 1987 A m e r i c a n C h e m i c a l Society
Johnson et al.; The Chemistry of Acid Rain ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
THE CHEMISTRY OF ACID RAIN
214
I n p a r t i c u l a r , we demonstrate the u s e f u l n e s s and c o m p a t i b i l i t y of two m u l t i - e l e m e n t methods o f a n a l y s i s : instrumental neutron a c t i v a t i o n a n a l y s i s (INNA) and i n d u c t i v e l y c o u p l e d plasma-atomic emission spectroscopy (ICP). The r e s u l t s and i n t e r p r e t a t i o n s r e p o r t e d h e r e a r e p r e l i m i n a r y and p a r t o f an on-going s t u d y o f p o l l u t a n t s i n u r b a n p r e c i p i t a t i o n .
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Rain
Sampling
W e t - p e r i o d r a i n w a t e r samples (washout and r a i n o u t ) were c o l l e c t e d from t h r e e s i t e s i n the H a m i l t o n a r e a : near the i n d u s t r i a l a r e a (beach s t r i p ) , i n the c i t y c e n t r e and a t the r u r a l H a m i l t o n A i r p o r t (Figure 1). The w e t - p e r i o d c o l l e c t o r s employed were m o d i f i e d Canadian Atmospheric Environment S e r v i c e s t a n d a r d r a i n g a u g e s . A l l components o f t h e gauge a r e made o f p l a s t i c and c o n s i s t of a f u n n e l w i t h an o r i f i c e o f 100 cm , a g r a d u a t e d c o l l e c t i o n tube and the h o u s i n g u n i t . The e n t i r e gauge s t a n d s about 36 cm i n h e i g h t . The m o d i f i c a t i o n i n c l u d e s a s p r i n g l o a d e d p l a s t i c l i d w h i c h keeps the o r i f i c e o f the gauge c o v e r e d d u r i n g d r y p e r i o d s . The o n s e t o f r a i n wets and thus weakens a d e g r a d a b l e t i s s u e w h i c h n o r m a l l y h o l d s t h e l i d c l o s e d . The f o r c e o f the s p r i n g t e a r s the t i s s u e and opens the l i d thus e x p o s i n g the c o l l e c t o r o r i f i c e to t h e r a i n . The amount o f r a i n r e q u i r e d t o wet the t i s s u e enough t o open the c o l l e c t o r i s 0.1 mm. A more d e t a i l e d d e s c r i p t i o n o f the gauge and i t s o p e r a t i o n has been r e p o r t e d e l s e w h e r e (2^). Samples were c o l l e c t e d i m m e d i a t e l y a f t e r each r a i n e v e n t . 2
The f u n n e l and c o l l e c t o r tubes were t h o r o u g h l y washed w i t h d e i o n i z e d d i s t i l l e d water and u l t r a pure n i t r i c a c i d p r i o r t o each installation. One mL o f n i c t r i c a c i d was then added to t h e c o l l e c t o r tubes t o p r e v e n t a b s o r p t i o n . A f t e r c o l l e c t i o n the samples were r e f r i g e r a t e d p r i o r to a n a l y s i s . P r e c a u t i o n s were t a k e n t o m a i n t a i n clean laboratory conditions. Chemical
Analysis
Instrumental Neutron A c t i v a t i o n A n a l y s i s
(INAA)
The c o l l e c t e d r a i n samples were a n a l y s e d by INAA at t h e McMaster Nuclear Reactor. Ten elements (AL, B r , Ca, C l , Cu, I , Mg, Mn, Na and V) were d e t e r m i n e d . An a l i q u o t o f 5 mL o f r a i n w a t e r was p l a c e d i n t o an a c i d washed p o l y e t h y l e n e v i a l and t r a n s p o r t e d v i a a r a b b i t ' c a r r i e r t o t h e r e a c t o r c o r e w h i c h has a n o m i n a l n e u t r o n f l u x o f 5 χ 1 0 n c m sec \ The samples were i r r a d i a t e d f o r f i v e m i n u t e s . The i r r a d i a t e d v i a l s were then t r a n s f e r r e d t o i n e r t v i a l s w h i c h were p l a c e d a t t h e snout o f a 22% e f f i c i e n t APTEC d e t e c t o r c o u p l e d t o a C a n e b e r r a S e r i e s 90 m u l t i c h a n n e l a n a l y s e r and a p i l e up r e j e c t o r u n i t . The r e s o l u t i o n o f the system was 2.1 KeV a t t h e 1332 KeV c o b a l t peak. Typical dead t i m e s were 10% o r l e s s . The samples had an average d e l a y time o f 100 seconds and were counted f o r a p e r i o d o f 10 m i n u t e s . S y n t h e t i c s t a n d a r d s were used to c a l i b r a t e t h e system, and NBS s t a n d a r d s were a n a l y s e d t o g e t h e r w i t h t h e samples t o ensure q u a l i t y control: r e s u l t s a r e shown i n T a b l e I . 1
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Johnson et al.; The Chemistry of Acid Rain ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
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18.
Sulfur, Halogens,
LANDSBERGER ET AL.
TABLE I.
R e s u l t s f o r NBS
and Heavy Metals in
1643b C e r t i f i e d Water
1
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Element
INAA (ppb)
18
Al Β Ba Br Ca CI Co Cr Cu Fe I Mg Mn Na Ni S V Zn
+- 5
