The Chemistry of Acid Rain - American Chemical Society

Chapter 4

The Western Atlantic Ocean Experiment 1

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James N. Galloway , Thomas M. Church , Anthony H. Knap , Douglas M. Whelpdale , and John M. Miller 5

Downloaded by CORNELL UNIV on May 29, 2017 | http://pubs.acs.org Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

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Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22903 College of Marine Studies, University of Delaware, Newark, DE 19711 Bermuda Biological Station, St. Georges West 1-15, Bermuda Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario M3H 5T4, Canada National Oceanic and Atmospheric Administration, 8060 13th Street, Silver Spring, MD 20910

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The Western Atlantic Ocean Experiment (WATOX) investi gates the flux and fate of sulfur, nitrogen, and tracemetal and trace-organic compounds eastward from North America. Using a variety of sampling platforms (ships, aircraft, islands), samples of gases, aerosols, and precipitation have been used to determine the impact of North America on atmospheric chemical cycles of the western A t l a n t i c Ocean. This paper provides an overview of the results obtained since WATOX began i n 1980. The Western A t l a n t i c Ocean E x p e r i m e n t (WATOX) i s d e s i g n e d t o d e t e r mine the amount and the f a t e o f s e l e c t e d s u l f u r , n i t r o g e n , m e t a l and o r g a n i c compounds advected e a s t w a r d from N o r t h A m e r i c a . The s p e c i f i c a t m o s p h e r i c f l u x e s b e i n g i n v e s t i g a t e d are d e p i c t e d i n F i g u r e 1 and e x p l a i n e d i n T a b l e I ; the p a r t i c i p a t i n g u n i v e r s i t i e s and agencies are l i s t e d i n T a b l e I I . T h i s paper p r e s e n t s a b r i e f o v e r v i e w o f the approach we are u s i n g t o a c h i e v e the a b o v e - s t a t e d o b j e c t i v e s and summarizes our a c c o m p l i s h m e n t s . The measurement program has two components, l o n g - t e r m and i n t e n s i v e . F o r the l o n g - t e r m component, data c o l l e c t i o n t o d e t e r mine the c o m p o s i t i o n o f wet d e p o s i t i o n a t Lewes, D e l a w a r e , and on Bermuda began i n 1980. I n 1984, another s i t e was added a t A d r i g o l e , I r e l a n d . From 1981 t o 1985 d u r i n g M a y - O c t o b e r , p r e c i p i t a t i o n sam p l e s were a l s o c o l l e c t e d on two s h i p s c r u i s i n g w e e k l y between New York C i t y , Bermuda, and Nassau. P r e c i p i t a t i o n - c h e m i s t r y data from the t h r e e l a n d - b a s e d s i t e s and from the s h i p s were used t o c a l c u l a t e

0097-6156/87/0349-0039$06.00/0 © 1987 American Chemical Society

Johnson et al.; The Chemistry of Acid Rain ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

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T a b l e I . WATOX F l u x e s and Methods (see F i g . 1) D e t e r m i n a t i o n Methods

F l u x e s from F i g . 1 A.

B.

Emission to North atmosphere

American

A d v e c t i o n eastward

C. Wet d e p o s i t i o n


Dry d e p o s i t i o n D.

Atmospheric t r a n s f o r m a t i o n s

E.

E m i s s i o n from sea s u r f a c e

F.

Advection eastward

L i t e r a t u r e search C a l c u l a t i o n s ; land-based and a i r c r a f t sampling F i e l d measurements on s h i p s , on Bermuda, and a t Lewes, DE C o n c e n t r a t i o n measurements on s h i p s , on Bermuda, and a t Lewes, DE C a l c u l a t i o n s ; atmospheric measurements C a l c u l a t i o n s ; e s t i m a t e s from literature C a l c u l a t i o n s ; land-based, s h i p based, and a i r c r a f t sampling

Table I I . Members o f t h e WATOX Consortium Investigator and Agency J . N. Galloway University of Virginia C h a r l o t t e s v i l l e , VA

WATOX d i r e c t o r Atmospheric d e p o s i t i o n o f S and Ν compounds and o r g a n i c a c i d s

T. M. Church U n i v e r s i t y o f Delaware Newark, DE

Atmospheric d e p o s i t i o n o f t r a c e m e t a l elements

A. H. Knap Bermuda B i o l o g i c a l S t a t i o n S t . Georges, Bermuda

Atmospheric d e p o s i t i o n o f t r a c e o r g a n i c compounds

J . M. M i l l e r NOAA S i l v e r S p r i n g , MD

T r a n s p o r t and air-mass

D. M. Whelpdale T r a n s p o r t and air-mass Atmospheric Environment S e r v i c e T o r o n t o , Canada J . Boatman NOAA B o u l d e r , CO

Aircraft

trajectories

trajectories

coordination

r a t e s o f wet d e p o s i t i o n and t o t r a c k a i r masses e a s t w a r d from N o r t h America. The i n t e n s i v e component o f the WATOX measurement program (Intensives) involves p e r i o d i c sampling t o a s c e r t a i n the processes c o n t r o l l i n g t h e t r a n s p o r t , t r a n s f o r m a t i o n , and d e p o s i t i o n o f



4.

GALLOWAY ET AL.

The Western Atlantic Ocean Experiment

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m a t e r i a l s t o t h e w e s t e r n A t l a n t i c Ocean. D u r i n g t h e seven I n t e n s i v e s t h a t have a l r e a d y t a k e n p l a c e (Table I I I ) , each o f w h i c h l a s t e d from one t o f o u r weeks, i n s t r u m e n t s s p e c i f i c a l l y d e s i g n e d t o d e t e r m i n e a t m o s p h e r i c c o n c e n t r a t i o n s o f gas and a e r o s o l s p e c i e s were p l a c e d a t land-based s i t e s and on s h i p s and a i r c r a f t . F o r each I n t e n s i v e , s c i e n t i s t s from i n s t i t u t i o n s t h a t were n o t p a r t o f t h e WATOX c o n s o r t i u m were i n v i t e d t o p a r t i c i p a t e i n such a way as t o complement t h e s k i l l s and r e s e a r c h a b i l i t i e s o f the permanent WATOX personnel. The f i r s t two I n t e n s i v e s (WATOX-82 and WATOX-83, see Table I I I ) i n v e s t i g a t e d changes i n t h e c o m p o s i t i o n o f a i r p a r c e l s t h a t t r a v e l from N o r t h A m e r i c a t o Bermuda. D u r i n g WATOX-82 and WATOX-83, s c i e n t i s t s from G e n e r a l Motors and the U n i v e r s i t y o f M i a m i measured c o n c e n t r a t i o n s o f t r a c e gases and a e r o s o l s a t Lewes, Delaware, and H i g h P o i n t , Bermuda. WATOX-84, t h e t h i r d I n t e n s i v e , used d a t a from samples c o l l e c t e d onboard t h e RV K n o r r as i t t r a v e l e d between N o r t h A m e r i c a and A f r i c a . These d a t a were used t o support t h e gas and a e r o s o l d a t a from WATOX82 and WATOX-83 and t o t e s t new s h i p b o a r d p r e c i p i t a t i o n - c o l l e c t i o n instruments. WATOX-82, -83, and -84 sampled a i r i n the marine boundary l a y e r . These s e a - l e v e l measurements gave no i n f o r m a t i o n about uppera i r t r a n s p o r t . To overcome t h i s d e f i c i e n c y , t h e f o u r t h t h r o u g h t h e seventh I n t e n s i v e s i n c o r p o r a t e d d a t a c o l l e c t e d onboard two NOAA r e s e a r c h a i r c r a f t , t h e NOAA WP-3D and the NOAA K i n g A i r . (See Table I I I f o r t h e s p e c i f i c s p e c i e s measured.) B o t h a i r c r a f t c a r r i e d s a m p l i n g and a n a l y t i c a l equipment d e s i g n e d t o d e t e r m i n e the v e r t i c a l and h o r i z o n t a l c h e m i c a l s t r u c t u r e o f t h e atmosphere. F o r WATOX-85 the K i n g A i r f l e w m i s s i o n s e a s t o f Newport News, V i r g i n i a , and a d j a c e n t t o Bermuda d u r i n g passages o f w i n t e r c o l d f r o n t s between N o r t h A m e r i c a and Bermuda. D u r i n g these f l i g h t s a t m o s p h e r i c gases and a e r o s o l s were sampled and the data were r e c o r d e d as a f u n c t i o n o f a l t i t u d e and l a t i t u d e . We used b o t h a i r c r a f t f o r WATOX-86A. The WP-3D (based a t McGuire A i r F o r c e Base, New J e r s e y ) f l e w p a r a l l e l t o the c o a s t between Newfoundland and F l o r i d a and t h e K i n g A i r (based a t Eanscom F i e l d near Boston, M a s s a c h u s e t t s ) f l e w a course o f f Cape Cod. WATOX 86-B used o n l y t h e K i n g A i r d u r i n g t h r e e weeks i n F e b r u a r y o f 1986. Data from b o t h 86-A and -B were used t o a n a l y z e f u r t h e r the v e r t i c a l and the h o r i z o n t a l c h e m i c a l s t r u c t u r e o f t h e atmosphere. WATOX-86C used t h e K i n g A i r out o f Bermuda t o d e t e r m i n e t h e a d v e c t i o n f l u x e s o f s u l f u r and n i t r o g e n s p e c i e s when a i r f l o w was c o n t r o l l e d by t h e Bermuda High and thus unimpacted by e m i s s i o n s from N o r t h America. Summary o f F i n d i n g s E a s t w a r d A d v e c t i o n o f S and Ν from N o r t h America. To make an i n i t i a l e s t i m a t e o f t r a n s p o r t and a d v e c t i o n e a s t w a r d from N o r t h A m e r i c a , M i l l e r and H a r r i s (1) have c a l c u l a t e d back t r a j e c t o r i e s from Bermuda and have developed a f l o w c l i m a t o l o g y c o v e r i n g seven y e a r s — f r o m January 1975 t o December 1981. U s i n g the GAMBIT-1 model from the NOAA A i r Resources L a b o r a t o r y , t h i s group has produced 10day back t r a j e c t o r i e s f o r t h e 850-mb l e v e l , on a d a i l y b a s i s , c o v e r ing t h i s seven-year p e r i o d . M i l l e r and H a r r i s (1,) have adopted a


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T a b l e I I I . WATOX I n t e n s i v e s


Name/Date

Location

Platform

WATOX-82 August

Lewes Bermuda

Ground (G, A, P) Ground (G, A, P)

WATOX-83 February

Lewes Bermuda


WATOX-84 May

Atlantic R. V. K n o r r (Dakar t o (G, A, P) Boston)

WATOX-85 Mar/Apr

Lewes Bermuda


S p e c i e s Measured Gas: NO, NO . S 0 CO A e r o s o l : NO? SO^, t r a c e metals P r e c i p i t a t i o n : Major i o n s , trace metals, organic acids, trace organics CO Gas: NO, Ν 0 , S 0 , A e r o s o l : N O 3 , SO^, t r a c e metals P r e c i p i t a t i o n : Major i o n s , trace metals, organic acids, trace organics Gas: H N 0 , S 0 DMS A e r o s o l : NO3 "SO^, t r a c e metals, organic acids P r e c i p i t a t i o n : Major ions, trace metals, organic acids, trace organics Gas: NO, Ν 0 , t o t a l S, CO, CO3, t r a c e o r g a n i c s Aerosol: trace metals, NO3, 0

χ

2

3

0

χ

so

4

P r e c i p i t a t i o n : Major i o n s , trace metals, organic acids, trace organics WATOX-86A January

WATOX-86B February

Lewes Bermuda McGuire AFB Hanscom Field

Lewes Bermuda Hanscom Field

Ground (P) Ground (P) WP-3D (G, A) K i n g A i r (G, A)

Ground (P) Ground (P) K i n g A i r (G, A)

Gas: H N 0 , 3

Lewes Bermuda Bermuda

Ground (P) Ground (P) K i n g A i r (G, A)

N 0 , ΝΟ 2

χ

2

Gas: H N 0 , 3

PAN, NO,

N 0 , Ν0 2

χ

S 0 , DMS, CO, O 3 , t r a c e organics, organic acids A e r o s o l : Trace metals, N O 3 , 2

so WATOX-86C June

PAN, NO,

S 0 , DMS, CO, O 3 , t r a c e organics, o r g a n i c a c i d s A e r o s o l : NO^"", S 0 ^ ~ , t r a c e metals, organic acids, trace organics P r e c i p i t a t i o n : Major i o n s , o r ganic a c i d s , trace organics

4

P r e c i p i t a t i o n : Major ions, o r ganic a c i d s , t r a c e o r g a n i c s Gas: HNO,, PAN, NO, N 0 , Ν 0 S 0 , DMS, CO, O 3 , t r a c e organics, organic acids Aerosol: Trace metals, NO3, 2

χ

2

so

4

P r e c i p i t a t i o n : Major i o n s , o r ganic a c i d s , t r a c e o r g a n i c s NOTE: (G) means t h a t gas was c o l l e c t e d , precipitation.

(A), a e r o s o l , ( P ) ,



4.

GALLOWAY ET

AL.


43

c l a s s i f i c a t i o n scheme t h a t s t r a t i f i e s a i r f l o w as a f u n c t i o n of compass s e c t o r . T h i s c l a s s i f i c a t i o n shows t h a t , f o r a l m o s t 60% o f the seven y e a r s , t h e r e was a d i r e c t f l o w o f a i r o f f the N o r t h American continent. To d e t e r m i n e the a d v e c t i o n r a t e of S and Ν eastward from N o r t h A m e r i c a , Whelpdale and h i s c o l l e a g u e s (2) c a l c u l a t e d a i r - m a s s advec t i o n as a f u n c t i o n of l a t i t u d e and a l t i t u d e ( F i g u r e 2). Then, u s i n g r e p r e s e n t a t i v e g r o u n d - l e v e l and above-ground c o n c e n t r a t i o n s o f t r a c e s u l f u r and n i t r o g e n s p e c i e s , G a l l o w a y and h i s c o l l e a g u e s (3) c a l c u l a t e d a d v e c t i o n f l u x e s o f S and Ν by c o m b i n i n g the l o n g i t u d i n a l and a l t i t u d i n a l v a r i a t i o n s of a i r - m a s s f l u x w i t h the l o n g i t u d i n a l and a l t i t u d i n a l v a r i a t i o n s of the a t m o s p h e r i c c o n c e n t r a t i o n s o f S and Ν compounds ( F i g u r e s 3 and 4). They r e p o r t a b r o a d maximum i n S and Ν t r a n s p o r t between 38° Ν and 52° N. Of the S and Ν e m i t t e d t o the atmosphere of e a s t e r n N o r t h A m e r i c a , about 34% and 22-69%, r e s p e c t i v e l y , are advected eastward. T r a n s p o r t a t a l l a l t i t u d e s up t o a t l e a s t 5.5 km i s i m p o r t a n t . Impact of N o r t h A m e r i c a n E m i s s i o n s on Wet D e p o s i t i o n t o the W e s t e r n A t l a n t i c Ocean. Wet d e p o s i t i o n has been c o l l e c t e d by event d u r i n g WATOX at two s i t e s on Bermuda, one s i t e near Lewes, Delaware, and on b o a r d s h i p s . These w e t - d e p o s i t i o n samples have been a n a l y z e d f o r a c i d i c s p e c i e s , m e t a l s , and o r g a n i c compounds. T h i s s e c t i o n d i s cusses our i n t e r p r e t a t i o n of the marine p r e c i p i t a t i o n - c h e m i s t r y d a t a and the r e s u l t s o f our a n a l y s e s as w e l l as the i n f l u e n c e o f N o r t h A m e r i c a n e m i s s i o n s on p r e c i p i t a t i o n c o m p o s i t i o n . I n i n t e r p r e t i n g m a r i n e p r e c i p i t a t i o n - c h e m i s t r y data, the d i f f e r e n t i a t i o n of s e a - s a l t and n o n - s e a - s a l t (or excess s e a - s a l t ) com ponents i s e s s e n t i a l . U n c e r t a i n t i e s i n such c a l c u l a t i o n s a r i s e from the u n c e r t a i n t i e s r e g a r d i n g (1) the c o m p o s i t i o n of seawater, (2) the a n a l y s e s , (3) the amount of d r y - d e p o s i t e d sea s a l t i n the samples, (4) the v a l i d i t y of assuming a p u r e l y marine source f o r the s e a - s a l t r e f e r e n c e s p e c i e s , and (5) the v a l i d i t y of assuming no f r a c t i o n a t i o n d u r i n g o r a f t e r the p r o d u c t i o n o f s e a - s a l t a e r o s o l s . Xeene and h i s c o l l e a g u e s at the U n i v e r s i t y of V i r g i n i a (4) assessed these u n c e r t a i n t i e s and e v a l u a t e d the assumptions by a n a l y z i n g the c o m p o s i t i o n o f p r e c i p i t a t i o n c o l l e c t e d on Bermuda. They r e p o r t s i g n i f i c a n t c o n c e n t r a t i o n s of l o c a l l y d e r i v e d a l k a l i and a l k a l i n e e a r t h m e t a l s as w e l l as evidence of the i n f l u e n c e of c o n t i n e n t a l and n o n - s e a - s a l t marine sources of excess S O ^ " c o n c e n t r a t i o n s . These o b s e r v a t i o n s suggest t h a t the p a s t assumptions i n v o l v e d i n s e a - s a l t c o r r e c t i o n s are not always v a l i d . T h e r e f o r e , t o s e l e c t the a p p r o p r i a t e r e f e r ence s p e c i e s , i n d i v i d u a l d a t a s e t s s h o u l d be e v a l u a t e d u s i n g o b j e c tive c r i t e r i a . The c o n c e n t r a t i o n of excess components i n p r e c i p i t a t i o n i s the d i f f e r e n c e between the t o t a l c o n c e n t r a t i o n and the s e a - s a l t compo nent of the t o t a l c o n c e n t r a t i o n . There are o f t e n l a r g e u n c e r t a i n t i e s a s s o c i a t e d w i t h excess c o n c e n t r a t i o n s r e s u l t i n g from s m a l l d i f f e r e n c e s between l a r g e numbers. Hawley, G a l l o w a y , and Keene ( U n i v e r s i t y of V i r g i n i a , C h a r l o t t e s v i l l e , u n p u b l i s h e d data) have d e r i v e d a nomogram t e c h n i q u e t o d e t e r m i n e the u n c e r t a i n t y i n v o l v e d knowing o n l y the t o t a l c o n c e n t r a t i o n of the element i n q u e s t i o n (e.g., SO^-), the t o t a l N a c o n c e n t r a t i o n , and the r e s p e c t i v e a n a l y +



44

Γ

(0 / - — \

Β !

e

I North America

u

J

Western Atlantic Ocean


F i g u r e 1. A c o n c e p t u a l overview o f the f l u x e s b e i n g i n v e s t i g a t e d i n WATOX and t h e i r method o f measurement (see a l s o T a b l e I ) .

F i g u r e 2. Net a i r f l u x as a f u n c t i o n o f l a t i t u d e and a l t i t u d e . ( R e p r i n t e d w i t h p e r m i s s i o n from r e f . 2. 1984 Pergamon J o u r n a l s . )



GALLOWAY ET AL.


Sulfur (Tg.y ) 1

F i g u r e 3. Net s u l f u r f l u x as a f u n c t i o n o f l a t i t u d e and a l t i t u d e ( R e p r i n t e d w i t h p e r m i s s i o n from r e f . 3. 1984 Pergamon J o u r n a l s . )



F i g u r e 4. altitude. Journals.)

Net n i t r o g e n f l u x as a f u n c t i o n of l a t i t u d e and ( R e p r i n t e d w i t h p e r m i s s i o n from r e f . 3. 1984 Pergamon



4.

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excess c o n c e n t r a t i o n s as a f u n c t i o n o f excess and t o t a l c o n c e n t r a t i o n s . A t p o i n t A, where the t o t a l and excess S0^~ c o n c e n t r a t i o n s are 60 μeq/l and 18 μο^/1, r e s p e c t i v e l y , the r e l a t i v e s t a n d a r d e r r o r o f the c a l c u l a t e d excess c o n c e n t r a t i o n i s 20%. However, a t p o i n t B, the e r r o r i s 4 0 % due t o the g r e a t e r c o n t r i b u t i o n o f s e a - s a l t SO^". T h i s i l l u s t r a t e s t h a t the e r r o r s o f the c a l c u l a t e d excess c o n c e n t r a t i o n are not o n l y a f u n c t i o n o f the a n a l y t i c a l u n c e r t a i n t i e s b u t a l s o o f the r e l a t i v e abundance o f the excess and s e a - s a l t components (see a l s o 4). The use o f the s i t e on Bermuda t o c o l l e c t p r e c i p i t a t i o n t h a t i s c h e m i c a l l y r e p r e s e n t a t i v e o f the marine environment assumes t h a t Bermuda i t s e l f does n o t i n f l u e n c e the amount o r c o m p o s i t i o n o f the p r e c i p i t a t i o n . Because the i s l a n d i s l o w and narrow, i t s c o n f i g u r a t i o n d i d not i n f l u e n c e the amount (5.) a l t h o u g h i t c o u l d a f f e c t t h e composition. I n a n a l y s e s o f p r e c i p i t a t i o n from two s i t e s on B e r muda, the s e a - s a l t and excess C a ^ components o f p r e c i p i t a t i o n were found t o i n c r e a s e as a r e s u l t o f t u r b u l e n c e a t the s e a / l a n d and a i r / l a n d i n t e r f a c e s , r e s p e c t i v e l y (Galloway, J . N.; Tokos, J . J . ; Whelpdale, D. M; Knap, A. H., U n i v e r s i t y o f V i r g i n i a , C h a r l o t t e s v i l l e , u n p u b l i s h e d data). A l s o f o r samples taken from p r e c i p i t a t i o n c o l l e c t i o n s i t e s downwind o f the i s l a n d , c o n c e n t r a t i o n s o f excess SO^ and H were s l i g h t l y i n c r e a s e d by l o c a l sources. However, t h e impact o f the i s l a n d on the t o t a l excess SO^ and H c o n c e n t r a t i o n s was s m a l l r e l a t i v e t o the o f f - i s l a n d sources. WATOX a l s o used s h i p s as p l a t f o r m s t o c o l l e c t p r e c i p i t a t i o n f o r c h e m i c a l a n a l y s e s . To t e s t the impact on the p r e c i p i t a t i o n c o m p o s i t i o n o f the f o s s i l f u e l s used by the s h i p s f o r p r o p u l s i o n , G a l l o w a y , Knap, and Church (6) had p r e c i p i t a t i o n samples c o l l e c t e d on the windward and l e e w a r d b r i d g e wings o f two s h i p s s a i l i n g between New York and Bermuda. They r e p o r t t h a t the samples from the windward b r i d g e wings are u n a f f e c t e d by the s h i p and are thus r e p r e s e n t a t i v e o f marine p r e c i p i t a t i o n and a p p r o p r i a t e f o r use i n a n a l y s e s o f the major c h e m i c a l c o n s t i t u e n t s sought. As p a r t o f the WATOX r e s e a r c h on the major i n o r g a n i c s p e c i e s i n wet d e p o s i t i o n i n the w e s t e r n A t l a n t i c Ocean, J i c k e l l s and h i s c o l l e a g u e s (2) sampled r a i n c o l l e c t e d on Bermuda between May 1980 and May 1981. They s t a t e t h a t t h e r e i s a s t r o n g c o r r e l a t i o n between the presence o f s u l f u r i c and n i t r i c a c i d s and the m e t e o r o l o g i c a l back t r a j e c t o r i e s o f Bermuda storm systems t o the N o r t h A m e r i c a n c o n t i n e n t . T h i s suggests the long-range t r a n s p o r t o f a c i d - r a i n p r e c u r s o r s t o Bermuda from the N o r t h A m e r i c a n c o n t i n e n t . The r e s u l t s o f the work by J i c k e l l s and h i s c o l l e a g u e s i s supported by the a n a l y s e s r e p o r t e d by G a l l o w a y , Knap, and Church (6) o f p r e c i p i t a t i o n data c o l l e c t e d on b o a r d s h i p s i n the w e s t e r n A t l a n t i c Ocean. I n a d d i t i o n , the a n a l y s e s o f f o u r y e a r s o f w e t - d e p o s i t i o n data c o l l e c t e d on Bermuda by event a l s o supported these c o n c l u s i o n s ( G a l l o w a y , J . N.J A r t z , R. S.*, Keene, W. C ; C h u r c h , T. M.; Knap, A. H., U n i v e r s i t y o f V i r g i n i a , C h a r l o t t e s v i l l e , u n p u b l i s h e d data). U s i n g the NOAA ARL a i r - m a s s t r a j e c t o r y model, the WATOX r e s e a r c h e r s s t r a t i f i e d v o l u m e - w e i g h t e d averages o f p r e c i p i t a t i o n c o m p o s i t i o n by compass s e c t o r . The r e s u l t s o f these s t r a t i f i c a t i o n s f o r excess SO^~ ( F i g u r e 6) showed t h a t Bermuda was an i d e a l s a m p l i n g p l a t f o r m f o r a i r t h a t , a t t i m e s , was d i r e c t l y i m p a c t e d by anthropogenic t i c a l u n c e r t a i n t i e s . JFiguçe 5 shows «the, r e l a t i v e s t a n d a r d e r r o r o f +

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F i g u r e 5. R e l a t i v e s t a n d a r d e r r o r o f excess s u l f a t e as a f u n c t i o n o f t o t a l and excess s u l f a t e c o n c e n t r a t i o n s (Hawley, M. E.j G a l l o w a y , J . N.; Keene, W. C, U n i v e r s i t y o f V i r g i n i a , C h a r l o t t e s v i l l e , unpublished data).

VolumeWeighted Composition of Precipitation

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F i g u r e 6. Volume-weighted excess SO^ c o n c e n t r a t i o n i n Bermuda p r e c i p i t a t i o n as a f u n c t i o n o f a i r - m a s s t r a j e c t o r y .



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sources i n N o r t h A m e r i c a and, a t o t h e r t i m e s , was impacted by a i r the c o m p o s i t i o n of w h i c h was more c o n t r o l l e d by marine p r o c e s s e s . Church et a l . (8.), i n p r e s e n t i n g a d d i t i o n a l i n f o r m a t i o n d e r i v e d from WATOX r e s e a r c h , r e p o r t on the ocean's i n f l u e n c e on p r e c i p i t a t i o n from storms t h a t l e a v e the N o r t h American c o n t i n e n t and t r a n s i t over the w e s t e r n A t l a n t i c . They pay p a r t i c u l a r a t t e n t i o n t o t h i s o c e a n i c i n f l u e n c e on the s u l f u r and n i t r o g e n p r e c u r s o r s o f a c i d r a i n s . They f u r t h e r r e p o r t t h a t , a l t h o u g h sea s a l t c o n t r i b u t e s over h a l f (by w e i g h t ) o f the s a l t i n p r e c i p i t a t i o n a t the c o a s t and o v e r t h r e e q u a r t e r s of the s a l t i n p r e c i p i t a t i o n a t Bermuda, most s u l f a t e (90% at the c o a s t and 50% a t Bermuda) i s i n excess o f sea s a l t . S i n c e G a l l o w a y , L i k e n s and Hawley (9) have found t h a t p r e c i p i t a t i o n on Bermuda has s i g n i f i c a n t l y more excess SO^"", NO^"", and H than more remote marine a r e a s , Church and h i s c o l l e a g u e s (8) have a t t r i buted these components to the long-range t r a n s p o r t o f s u l f u r and n i t r o g e n p r e c u r s o r s i n the marine t r o p o s p h e r e w i t h the s u l f u r i c - a c i d component d o m i n a t i n g . B e s i d e s u s i n g s h i p s t o c o l l e c t p r e c i p i t a t i o n t o be a n a l y z e d f o r major i o n s as r e p o r t e d by G a l l o w a y , Knap, and Church (6), WATOX-84 a l s o used s h i p s t o sample p r e c i p i t a t i o n , gases, and a e r o s o l s t o d e t e r m i n e the m e t a l , o r g a n i c , and major S and Ν 0 s p e c i e s . Church and h i s c o l l e a g u e s (10) have r e p o r t e d on a c r u i s e a c r o s s the N o r t h A t l a n t i c from Dakar, Senegal, t o Woods Hole, M a s s a c h u s e t t s , t h a t t r a n s i t e d the area o f 18°-48° N, 18°-70° W d u r i n g the s p r i n g . Dif f e r e n t a i r masses t h a t i n f l u e n c e the N o r t h A t l a n t i c are a n a l y z e d from s h i p b o a r d samples o f a i r c o l l e c t e d d u r i n g t h i s c r u i s e . These samples have been a n a l y z e d f o r a e r o s o l s (N, S, sea s a l t ) , gases (S02* DMS, MSA, HNO^, s y n t h e t i c o r g a n i c s ) , and p r e c i p i t a t i o n (major i n o r g a n i c i o n s , o r g a n i c a c i d s , and t r a c e elements). The r e s u l t s of these a n a l y s e s showed t h a t the c o m p o s i t i o n o f the l o w e r atmosphere over the N o r t h A t l a n t i c i s s t r o n g l y i n f l u e n c e d by c o n t i n e n t a l a i r masses. When a i r masses have o r i g i n s t h a t have passed over areas o f high emission i n North A f r i c a ( e a s t e r l i e s ) or North America (wester l i e s ) w i t h i n 1-2 days, the c o n c e n t r a t i o n s o f a c i d p r e c u r s o r s and s y n t h e t i c hydrocarbons i n the a i r and o f s t r o n g a c i d s , t r a c e m e t a l s , and, t o a l e s s e r e x t e n t , o r g a n i c a c i d s i n p r e c i p i t a t i o n approach those found i n e a s t e r n N o r t h America. Even o f f the n o r t h w e s t c o a s t of A f r i c a , t r a j e c t o r y a n a l y s e s l i n k the M e d i t e r r a n e a n r e g i o n w i t h a e r o s o l and p r e c i p i t a t i o n c h e m i s t r y s u g g e s t i v e o f biomass o r p e t r o leum b u r n i n g . The burden o f a t m o s p h e r i c d e p o s i t i o n t o the g r e a t e r N o r t h A t l a n t i c may i n f l u e n c e the o c e a n i c s u r f a c e c h e m i s t r y of t h i s region. U s i n g t e c h n i q u e s developed f o r the s a m p l i n g and a n a l y s e s o f t r a c e m e t a l s i n marine p r e c i p i t a t i o n by Tramantano, S c u d l a r k , and C h u r c h ( E n v i r o n . S c i . T e c h n o l . . i n p r e s s ) , C h u r c h e t a l . ( i l ) and J i c k e l l s e t a l . (12) have a l s o r e p o r t e d on c o n c e n t r a t i o n measure m e n t s o f t h e t r a c e m e t a l s Cd, Cu, Fe, Mn, N i , Pb, V, and Zn i n wet d e p o s i t i o n a t Lewes, Delaware, and on Bermuda. The purpose o f t h i s f a c e t o f the WATOX r e s e a r c h was t o a s s e s s the sources o f , the t r a n s p o r t t o , and the wet d e p o s i t i o n o f t r a c e m e t a l s t o the w e s t e r n A t l a n t i c Ocean d u r i n g nonsummer months. At t h i s t i m e o f the y e a r , t r a c e m e t a l s are l i k e l y t o be t r a n s p o r t e d by a w e s t e r l y a i r - m a s s f l o w from N o r t h A m e r i c a t o the open A t l a n t i c . Church and h i s c o l leagues r e p o r t t h a t the c o n c e n t r a t i o n s and wet d e p o s i t i o n of t r a c e χ




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m e t a l s are g r e a t e r i n samples from the Delaware c o a s t than from those on Bermuda, the o r d e r a t b o t h s i t e s i s s i m i l a r (Fe > Zn > Pb > Cu, Mn, N i > V > Cd). The t r a c e - m e t a l e n r i c h m e n t f a c t o r s f o r a l l m e t a l s b u t Mn (based on c r u s t a l Fe) a r e s i g n i f i c a n t l y g r e a t e r than u n i t y ; a g a i n the o r d e r i s t h e same i n samples from the Delaware c o a s t as f r o m t h o s e f r o m B e r m u d a (Cd > Pb > Z n > Cu > N i > V). T h i s evidence suggests common N o r t h A m e r i c a n sources f o r the t r a c e m e t a l s found i n w e s t e r n A t l a n t i c p r e c i p i t a t i o n as w e l l as t h e i m p o r t a n t a t m o s p h e r i c t r a n s p o r t o f t r a c e m e t a l s t o the A t l a n t i c Ocean. The c a l c u l a t i o n s u s i n g enrichment f a c t o r s from Na-based s e a - s a l t a e r o s o l i n d i c a t e t h a t the r e c y c l i n g o f t r a c e m e t a l s from the sea s u r f a c e , a l t h o u g h g e n e r a l l y not c o n s i d e r e d t o be i m p o r t a n t , c o u l d be a p o t e n t i a l l y s i g n i f i c a n t p r o c e s s c o n t r i b u t i n g t o the Mn and V e n r i c h m e n t s found i n p r e c i p i t a t i o n samples from t h e open w e s t e r n A t l a n t i c . C u t t e r and Church (13) have d e t e r m i n e d s e l e n i u m s p e c i e s i n w e s t e r n A t l a n t i c p r e c i p i t a t i o n so t h a t t h e e m i s s i o n sources u s i n g t h i s s u l f u r analogue, w h i c h i s e n r i c h e d i n f o s s i l f u e l s ( p r i m a r i l y c o a l ) , can be more e x a c t l y i d e n t i f i e d . The r e s u l t s show a c o r r e l a t i o n o f b o t h t o t a l Se and the Se IV:Se V I r a t i o w i t h i n c r e a s i n g p r o t o n s and excess s u l f u r i n p r e c i p i t a t i o n from Lewes, Delaware, and on Bermuda. T h e i r h y p o t h e s i s i s t h a t , a l t h o u g h some reduced forms (1 nM/kg) may come from background o c e a n i c e m i s s i o n s , most o x i d i z e d Se i s a r e f l e c t i o n o f f o s s i l - f u e l e m i s s i o n s from N o r t h America. As p a r t o f the WATOX program t o i n v e s t i g a t e the long-range t r a n s p o r t o f components from N o r t h A m e r i c a t o the w e s t e r n A t l a n t i c , Knap (14) has r e p o r t e d on t r a c e - o r g a n i c c o n t a m i n a n t s i n 51 samples of p r e c i p i t a t i o n c o l l e c t e d on Bermuda from 1 October 1982 t o 1 A p r i l 1983. He p r e s e n t s data on a l p h a and gamma isomers o f h e x a c h l o r o cyclohexane (HCH), c h l o r d a n e , and d i e l d r i n and n o t e s t h e presence o f PCBs and p h t h a l a t e e s t e r s i n some samples a l t h o u g h they are n o t quantified. The r a i n w a t e r c o n c e n t r a t i o n s o f t h e compounds t h a t he does q u a n t i f y v a r y and the s i z e o f events are n o t a p p a r e n t l y r e l a t e d to t h e c o n c e n t r a t i o n s , i n d i c a t i n g p o s s i b l e gas-phase scavenging. A l l t h e compounds on w h i c h Knap r e p o r t s i n d i c a t e a s e a s o n a l i t y w i t h g e n e r a l l y h i g h e r c o n c e n t r a t i o n s i n the w i n t e r months. The HCH and d i e l d r i n c o n c e n t r a t i o n s show a c o r r e l a t i o n w i t h a i r - m a s s t r a j e c t o r y — s t o r m s o r i g i n a t i n g i n the s o u t h e a s t e r n N o r t h A t l a n t i c have c o n c e n t r a t i o n s a f a c t o r o f f o u r l o w e r t h a n storms o r i g i n a t i n g west of Bermuda. Knap concludes t h a t p r e c i p i t a t i o n i s d e p o s i t i n g some p e s t i c i d e s and s y n t h e t i c o r g a n i c c h e m i c a l s t o the N o r t h A t l a n t i c Ocean. A l t h o u g h HCOOH and CH^COOH are i m p o r t a n t c h e m i c a l c o n s t i t u e n t s of c l o u d w a t e r and p r e c i p i t a t i o n , we do not y e t know t h e s o u r c e s f o r these compounds i n the atmosphere. I n a paper d i s c u s s i n g t h e i r r e s e a r c h on o r g a n i c a c i d s i n wet d e p o s i t i o n , Keene and G a l l o w a y (15) r e p o r t on 465 p r e c i p i t a t i o n samples from 14 c o n t i n e n t a l and marine s i t e s around the w o r l d t h a t were a n a l y z e d i n an a t t e m p t t o i d e n t i f y the source o f HCOOH and CH^COOH. Of these samples, 133 were c o l l e c t e d as p a r t o f the WATOX program. They a l s o r e p o r t t h a t c o n t i n e n t a l p r e c i p i t a t i o n d u r i n g growing seasons c o n t a i n s h i g h e r a b s o l u t e c o n c e n t r a t i o n s o f o r g a n i c a c i d s and h i g h e r r a t i o s o f HCOOj (HCOOH ^ + HCOO"") t o CH^OOj. (CH COOH + CHjCOO") than do marine p r e c i p i t a t i o n and c o n t i n e n t a l p r e c i p i t a t i o n d u r i n g nongrowing seasons. The c o n c e n t r a t i o n s o f BCOOrj. and CH^COO^. i n p r e c i p i t a t i o n a t most ft

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l o c a t i o n s are a l s o h i g h l y c o r r e l a t e d . These r e s u l t s support the h y p o t h e s i s t h a t o r g a n i c a c i d i t y i n p r e c i p i t a t i o n may o r i g i n a t e from two major s o u r c e s : v o l a t i l e v e g e t a t i v e c o n s t i t u e n t s over c o n t i n e n t s and an unknown, weaker source i n b o t h c o n t i n e n t a l and marine regions. R e l a t i v e t o s i m i l a r r a t i o s of ECOOj. t o CH^COOrj. i n the aqueous phase, d i f f e r e n c e s i n p r e c i p i t a t i o n pH r e s u l t i n l a r g e r e g i o n a l d i f f e r e n c e s i n c a l c u l a t e d e q u i l i b r i u m vapor-phase c o n c e n t r a t i o n s . The mechanism by w h i c h p r o p o r t i o n a t e c o n c e n t r a t i o n s of HCOO-j. and CHgCOOj are m a i n t a i n e d i n the aqueous phase has not y e t been d e t e r mined. Comparisons between p r e c i p i t a t i o n f r o m impacted and t h a t from remote r e g i o n s i n d i c a t e t h a t a n t h r o p o g e n i c e m i s s i o n s , a l t h o u g h pos s i b l y i m p o r t a n t near l a r g e p o p u l a t i o n and i n d u s t r i a l c e n t e r s , are p r o b a b l y not major s o u r c e s o f o r g a n i c a c i d s i n p r e c i p i t a t i o n over b r o a d g e o g r a p h i c r e g i o n s (£). G a l l o w a y and h i s c o l l e a g u e s ( U n i v e r s i t y o f V i r g i n i a , C h a r l o t t e s v i l l e , u n p u b l i s h e d data) a l s o found t h a t the r e g i o n where a storm o r i g i n a t e d d i d not have a s i g n i f i c a n t i n f l u e n c e on the amount of o r g a n i c a c i d s d e p o s i t e d on Bermuda by precipitation. T h i s evidence s u p p o r t e d the h y p o t h e s i s t h a t o r g a n i c a c i d s found i n the remote marine t r o p o s p h e r e might have a l o c a l , p o s s i b l y b i o g e n i c , source. The Impact of N o r t h A m e r i c a n E m i s s i o n s on the C o m p o s i t i o n o f the Atmosphere over the W e s t e r n A t l a n t i c Ocean. As p a r t o f WATOX-82 (August 1982) and WATOX-83 (January and F e b r u a r y 1983), G e n e r a l Motors Research L a b o r a t o r i e s o p e r a t e d a i r - m o n i t o r i n g s i t e s on the A t l a n t i c c o a s t near Lewes, Delaware, and on the southwest c o a s t of Bermuda, 1250 km t o the s o u t h e a s t o f the Delaware s i t e . T h e i r o v e r a l l purpose was t o s t u d y the t r a n s f o r m a t i o n s of the p r i n c i p a l a c i d - p r e c i p i t a t i o n p r e c u r s o r s , Ν 0 and SO s p e c i e s , as t h e y were t r a n s p o r t e d under c o n d i t i o n s not c o m p l i c a t e d by e m i s s i o n s from l o c a l sources. Three papers have r e s u l t e d from t h i s s t u d y (16. 17. 18). I n the f i r s t paper, W o l f f and h i s c o l l e a g u e s (16) d e s c r i b e the measurements o f gas and p a r t i c u l a t e s p e c i e s found i n the Lewes samples and the c o m p o s i t i o n and sources o f s u l f a t e a e r o s o l . On the average, the t o t a l - s u s p e n d e d - p a r t i c u l a t e (TSP) c o n c e n t r a t i o n a t Lewes i s 27.9 μg/m w h i l e the PM10 (mass o f p a r t i c l e s w i t h d i a m e t e r s £ 10 |im) c o n c e n t r a t i o n i s 22.0 pg/m , o r 79% o f the TSP. The PM10 c o n s i s t s of 6.1 pg/m of c o a r s e p a r t i c l e s (CPM, d i a m e t e r s = 2.5 μιη to 10 um) and 15.9 μg/m o f f i n e p a r t i c l e s (FOM, d i a m e t e r s < 2.5 um). On a mass b a s i s , the most i m p o r t a n t c o n s t i t u e n t s of the f i n e - p a r t i c u l a t e f r a c t i o n are s u l f a t e compounds a t 50% and o r g a n i c compounds at 30%. The mean l i g h t - e x t i n c t i o n c o e f f i c i e n t c o r r e s p o n d s to a v i s u a l range o f from 18 km t o 20 km. Most o f the e x t i n c t i o n can be a t t r i b u t e d t o s u l f a t e (60%) and o r g a n i c carbon (13%). P a r t i c l e - s i z e measurements show t h a t the mass median aerodynamic d i a m e t e r f o r b o t h s p e c i e s i s 0.43 um. This i s a larger p a r t i c l e s i z e f o r carbons than has p r e v i o u s l y been r e p o r t e d and r e s u l t s i n a more e f f i c i e n t l i g h t - s c a t t e r i n g a e r o s o l . W o l f f and h i s c o l l e a g u e s (16) conclude t h a t t h e i r p r i n c i p a l - c o m p o n e n t a n a l y s e s i n d i c a t e t h a t c o a l - c o m b u s t i o n e m i s s i o n s from the m i d w e s t e r n U n i t e d S t a t e s are the most s i g n i f i c a n t source o f the s u l f a t e found i n Lewes d u r i n g the summer and w i n t e r . χ

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The second paper by W o l f f and h i s c o l l e a g u e s (17) r e p o r t s on the t r a n s f o r m a t i o n s o f a e r o s o l and gaseous s p e c i e s over the w e s t e r n A t l a n t i c Ocean d u r i n g t r a n s p o r t from N o r t h A m e r i c a . They w r i t e t h a t the c o n c e n t r a t i o n s and c o m p o s i t i o n o f f i n e - a e r o s o l and t r a c e - g a s s p e c i e s on Bermuda are governed by the type o f a i r mass i n f l u e n c i n g the i s l a n d . During i n c u r s i o n s of a i r from the n o r t h e a s t e r n U n i t e d S t a t e s , w h i c h are most f r e q u e n t d u r i n g the w i n t e r , they have found h i g h e r c o n c e n t r a t i o n s o f a n t h r o p o g e n i c a l l y d e r i v e d s p e c i e s , such as S0 "~, HN0 , S 0 , 0 , Pb, Se, and e l e m e n t a l carbon. H i g h e r S 0 ~ c o n c e n t r a t i o n s are a s s o c i a t e d w i t h h i g h e r c o n c e n t r a t i o n s o f the c o a l - b u r n i n g t r a c e r Se and of HNO^ and 0 · The l a t t e r two r e l a t i o n s h i p s suggest a p h o t o c h e m i c a l r o l e and an a s s o c i a t i o n of HN0 w i t h c o a l b u r n i n g . S 0 i s s t r o n g l y a s s o c i a t e d w i t h the o i l - b u r n i n g t r a c e r , V. W o l f f and h i s c o l l e a g u e s r e p o r t i n t r u s i o n s o f a i r from the n o r t h e a s t e r n U n i t e d S t a t e s d u r i n g the F e b r u a r y 1983 I n t e n s i v e (WATOX-83). However, t h e r e were a l s o some i n t r u s i o n s d u r i n g the August 1982 I n t e n s i v e (WATOX-82) a l t h o u g h the summer was dominated by a s o u t h e a s t e r l y f l o w c o n t a i n i n g h i g h c o n c e n t r a t i o n s o f f i n e c r u s t a l m a t e r i a l , p r o b a b l y from the Sahara Desert. A l t h o u g h W o l f f e t a l . (17) f i n d t h a t t h e r e are more i n t r u s i o n s from N o r t h A m e r i c a d u r i n g the summer, they a l s o f i n d t h a t t h e r e are some d u r i n g the w i n t e r . T h e i r r e s e a r c h shows t h a t days w i t h a s o u t h e a s t e r l y a i r f l o w are a s s o c i a t e d w i t h h i g h l e v e l s of S i , T i , K, Fe, Ca, and Mn as w e l l as the l o w e s t e n r i c h m e n t f a c t o r s f o r a l l anthropogenic s p e c i e s . The e n r i c h m e n t f a c t o r s f o r the c r u s t a l spe c i e s are g e n e r a l l y independent of w i n d d i r e c t i o n f o r K. They go on t o suggest t h a t woodburning i n the n o r t h e a s t e r n U n i t e d S t a t e s may be the source of the h i g h e r Κ e n r i c h m e n t f a c t o r s found d u r i n g the w i n t e r . They used t h e i r Bermuda Ν 0 and S 0 data t o make a rough e s t i m a t e of the f l u x e s of these s p e c i e s i n the l a s t 1500 km from N o r t h A m e r i c a t o a n o r t h / s o u t h l i n e 1250 km e a s t of the U n i t e d S t a t e s , w h i c h passes through Bermuda. S i g n i f i c a n t amounts o f b o t h Ν Ο and S 0 advected o f f the E a s t Coast reached Bermuda and the f l u x e s appear t o be c o n s i s t e n t w i t h the f l u x e s c a l c u l a t e d by G a l l o way e t a l . (3.). I n the t h i r d paper t h a t r e s u l t e d from the WATOX r e s e a r c h i n w h i c h the G e n e r a l Motors R e s e a r c h L a b o r a t o r i e s took p a r t , G i b s o n , Korsog, and W o l f f (18) compare the a t m o s p h e r i c c o n c e n t r a t i o n s o f t r a c e - o r g a n i c s p e c i e s from samples a t Lewes, Delaware, t o those from Bermuda. T h e i r purpose was t o a s c e r t a i n the t r a n s f o r m a t i o n r e a c t i o n s of n i t r o a r o m a t i c , p o l y c y c l i c o r g a n i c m a t t e r (POM), and benso(a)pyrene (BaP) d u r i n g t r a n s p o r t from N o r t h America. They r e p o r t t h a t the r a t i o s of 1 - n i t r o p y r e n e and h y d r o x y n i t r o p y r e n e s t o i n e r t marker s p e c i e s ( f i n e - p a r t i c u l e l e a d , s e l e n i u m , and e l e m e n t a l carbon) are c o n s i d e r a b l y h i g h e r at a remote s i t e on Bermuda than i n D e l a ware. G i b s o n and h i s c o l l e a g u e s suggest t h a t these n i t r o a r o m a t i c POM are formed i n a t m o s p h e r i c r e a c t i o n s . The r a t i o of BaP t o the marker s p e c i e s i s s i m i l a r at the two s i t e s , w h i c h does not r e f l e c t the expected l o s s o f BaP i n a t m o s p h e r i c p h o t o c h e m i c a l r e a c t i o n s . 4

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The I n f l u e n c e of N o r t h A m e r i c a n E m i s s i o n s on the S u r f a c e Ocean. The i n c r e a s e d d e p o s i t i o n of f i x e d n i t r o g e n t o an ocean has the p o t e n t i a l t o a f f e c t the p r i m a r y p r o d u c t i v i t y i n the s u r f a c e of t h a t ocean. Knap and h i s c o l l e a g u e s (19), i n t h e i r WATOX-related r e s e a r c h on the



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i n f l u e n c e of i n o r g a n i c f i x e d n i t r o g e n ( n i t r a t e and ammonium) on the s u r f a c e ocean, a n a l y z e d two y e a r s of p r e c i p i t a t i o n data f o r n i t r a t e and ammonium c o n c e n t r a t i o n s . They conclude t h a t , on the average, p r e c i p i t a t i o n plays only a minor part i n p r o v i d i n g inorganic f i x e d n i t r o g e n f o r p r i m a r y p r o d u c t i v i t y i n o l i g o t r o p h i c ocean areas. They b e l i e v e t h i s t o be t r u e i n s p i t e of the c o n s i d e r a b l e i n c r e a s e of n i t r a t e from anthropogenic sources found i n r a i n w a t e r over the p a s t 100 y e a r s . However, p r e c i p i t a t i o n i s an e p i s o d i c p r o c e s s and the d e p o s i t i o n r a t e of f i x e d n i t r o g e n i s not the same f o r a l l events. Of the t o t a l i n o r g a n i c f i x e d n i t r o g e n , 40% i s wet d e p o s i t e d by o n l y 11% of the 126 events e v a l u a t e d by Knap and h i s c o l l e a g u e s . Based on t h i s , they s p e c u l a t e d t h a t o c c a s i o n a l " h o t " events may be i m p o r t a n t on s h o r t t i m e (about one day) and space (a few hundred kilometers) scales. The WATOX data on a t m o s p h e r i c i n p u t s of t r a c e m e t a l s i n t o and out of the Sargasso Sea i n the N o r t h A t l a n t i c have been used, i n a s s o c i a t i o n w i t h sediment r e c y c l i n g r a t e s , t o generate a p p r o x i m a t e l y s e l f - c o n s i s t e n t budgets f o r a range of t r a c e elements i n the S a r gasso Sea. Only f o r A l , Fe, Mn, and V are a d d i t i o n a l l a t e r a l o c e a n i c i n p u t s n e c e s s a r y t o c l o s e such budgets f o r the w e s t e r n A t l a n t i c . Thus f o r Cu, N i , Zn, Pb, and C d — a l l of w h i c h are en r i c h e d on a t m o s p h e r i c p a r t i c u l a t e s — a t m o s p h e r i c d e p o s i t i o n r e p r e sents the l a r g e s t i n p u t to the w e s t e r n A t l a n t i c . Much of the Cd, N, and Zn i s r e c y c l e d along w i t h n u t r i e n t s and these are then l a r g e l y e x p o r t e d from the w e s t e r n A t l a n t i c . Sedimentary r e c y c l i n g of the Cu may account f o r much of the t o t a l Cu f l u x t o the sediments as measured w i t h sediment t r a p s . J i c k e l l s and h i s c o l l e a g u e s (20) conclude t h a t , i f the a t m o s p h e r i c c o n c e n t r a t i o n s of Cd, Cu, N i , Pb, and Zn are c u r r e n t l y e n r i c h e d i n w e s t e r n A t l a n t i c p r e c i p i t a t i o n by anthropogenic p r o c e s s e s , then the a t m o s p h e r i c i n p u t t o the Sargasso Sea must have i n c r e a s e d by as much as two o r d e r s o f magnitude s i n c e p r e h i s t o r i c times. Knap, B i n k l e y , and Dueser (21) used the WATOX d a t a on atmos p h e r i c i n p u t s of t r a c e o r g a n i c s t o the s u r f a c e of the Sargasso Sea i n c o n j u n c t i o n w i t h data f r o m sediment t r a p s t o i n v e s t i g a t e the f l u x of contaminant substances t o the deep Sargasso Sea. They had a sediment t r a p moored 3200 m below the ocean s u r f a c e f o r two y e a r s t o study the c o n c e n t r a t i o n s o f p o l y c h l o r i n a t e d byphenyls (PCBs), c h l o r danes, and d i e l d r i n . These r e s e a r c h e r s r e p o r t a deep-sea f l u x of PCBs of 1.6 μg/m^ y r , w h i c h i s s u r p r i s i n g l y s i m i l a r t o the atmos p h e r i c f l u x of these compounds of 1.6-3.1 μg/m^ y r c a l c u l a t e d from the measured c o n c e n t r a t i o n s of the WATOX-82. They conclude t h a t , because t h e i r data c o r r e l a t e w e l l w i t h the data on o r g a n i c carbon, the d e p o s i t i o n mechanism t o the sediment i s p r o b a b l y a s s o c i a t e d w i t h biogenic particles. Beyond the Western A t l a n t i c Ocean. Whelpdale and h i s c o l l e a g u e s ( W h e l p d a l e , D.M.; E l i a s s e n , Α.; G a l l o w a y , J . N.; D o v l a n d , H.; M i l l e r , J. M. T e l l u s , i n p r e s s ) have examined the t r a n s p o r t of N o r t h A m e r i c a n s u l f u r e m i s s i o n s a c r o s s the n o r t h A t l a n t i c Ocean t o Europe. I n a r e v i e w of a v a i l a b l e p r e c i p i t a t i o n - s u l f a t e data from the n o r t h A t l a n t i c and a d j a c e n t c o a s t a l r e g i o n s , they r e p o r t a c o n c e n t r a t i o n f i e l d c o n s i s t e n t w i t h known source d i s t r i b u t i o n s and m e t e o r o l o g i c a l f a c t o r s . The excess s u l f a t e c o n c e n t r a t i o n o f marine background


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p r e c i p i t a t i o n i s 6-8 μβς/1 and excess [SO^ ] decreases from >50 μeq/l w i t h o f f s h o r e f l o w s a t the N o r t h A m e r i c a n e a s t c o a s t and t o 8-15 μβς/1 w i t h onshore f l o w s a t the European west coast. T h i s decay i s c o n s i s t e n t w i t h a d i s t a n c e c o n s t a n t o f 2400 km and a r e s i dence t i m e o f a p p r o x i m a t e l y 80 hours and, i n t u r n , c o r r e s p o n d s t o a t r a n s - A t l a n t i c f l u x o f a n t h r o p o g e n i c s u l f u r o f 0.3-0.4 Tg/yr. Whelpdale e t a l . r e p o r t f u r t h e r on a second independent e s t i m a t e based on the a p p l i c a t i o n o f a c l i m a t o l o g i c a l d i s p e r s i o n model t h a t accounts f o r l o n g - t e r m average d i f f u s i o n , wet and d r y d e p o s i t i o n , and t o S 0 ~ t r a n s f o r m a t i o n . U s i n g t h i s model, they c a l c u l a t e a f l u x o f N o r t h A m e r i c a n a n t h r o p o g e n i c s u l f u r a t t h e European west c o a s t o f 0.2 Tg/yr, w h i c h agrees w i t h t h e f i r s t e s t i m a t e . At t h e d i s t a n c e o f t h e European west c o a s t , N o r t h A m e r i c a n a n t h r o p o g e n i c e m i s s i o n s account f o r a p p r o x i m a t e l y 4 μeq/l i n p r e c i pitation. T h i s i s l e s s t h a n t h e m a r i n e background o f 6-8 μβς/1 and much l e s s t h a n t h e annual average excess [SO^] v a l u e o f a p p r o x i m a t e l y 30 μeq S / l a p p r o p r i a t e f o r much o f the c o a s t a l r e g i o n . Whelp d a l e e t a l . c o n c l u d e , t h e r e f o r e , t h a t , on the average, the amount o f N o r t h A m e r i c a n a n t h r o p o g e n i c s u l f u r r e a c h i n g Europe i s s m a l l com p a r e d t o t h a t from o t h e r s o u r c e s .


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Summary Over t h e p a s t few y e a r s , p a r t i c i p a n t s i n the WATOX program have been a b l e t o e s t i m a t e the e a s t w a r d a d v e c t i o n o f s u l f u r , n i t r o g e n , and t r a c e - m e t a l and t r a c e - o r g a n i c s p e c i e s from N o r t h A m e r i c a as w e l l as t h e i r impact on t h e p r e c i p i t a t i o n and s u r f a c e w a t e r s o f the w e s t e r n A t l a n t i c Ocean. The data base c o m p i l e d by the WATOX c o n s o r t i u m , a l t h o u g h e x t e n s i v e , i s s m a l l r e l a t i v e t o t h e s i z e o f the r e g i o n and the degree o f s p a t i a l and t e m p o r a l v a r i a b i l i t y o f t h e measured components. Thus, r e s e a r c h on the impact o f N o r t h A m e r i c a n e m i s s i o n s on the atmosphere and on t h e s u r f a c e w a t e r s o f the w e s t e r n A t l a n t i c Ocean c o n t i n u e s . We a r e s t i l l u s i n g a i r c r a f t , i s l a n d s , and s h i p s t o i n v e s t i g a t e the changes i n t h e N o r t h A m e r i c a n plume as i t t r a n s i t s the A t l a n t i c Ocean, the a t m o s p h e r i c t r a n s p o r t o f m a t e r i a l s a c r o s s t h e A t l a n t i c , and the impact o f a t m o s p h e r i c d e p o s i t i o n i n t h e surface ocean. Acknowledgments T h i s paper i s a c o n t r i b u t i o n from t h e Western A t l a n t i c Ocean E x p e r i m e n t (WATOX) and the Bermuda B i o l o g i c a l S t a t i o n . We g r a t e f u l l y acknowledge t h e support o f the N a t i o n a l Oceanic and Atmos p h e r i c A d m i n i s t r a t i o n o f t h e U n i t e d S t a t e s , the Canadian A t m o s p h e r i c Environment S e r v i c e , and the Bermuda government. We a l s o thank W i l l i a m Keene and A l e x Pszenny f o r t h e i r c o n s t r u c t i v e comments. We acknowledge and a p p r e c i a t e t h e t y p i n g s e r v i c e s o f Brenda M o r r i s and the e d i t o r i a l t a l e n t s o f M a r y - S c o t t M a r s t o n .

Literature Cited 1. Miller, J . M.; Harris, J . M. Atmos. Environ. 1985, 19, 409-414. 2. Whelpdale, D. M.; Low, T. B.; Kolomeychuk, R. J. Atmos. Environ. 1984, 18, 1311-1327.



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March 14,

1987


The Chemistry of Acid Rain - American Chemical Society

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