Acid Deposition and Atmospheric Chemistry at Allegheny Mountain

Chapter 3

Acid Deposition and Atmospheric Chemistry at Allegheny Mountain 1

1

1

1

1

W. R. Pierson , W. W. Brachaczek , R. A. Gorse, Jr. , S. M. Japar , J. M. Norbeck , and G. J. Keeler 2

Downloaded by UNIV OF CINCINNATI on May 25, 2016 | http://pubs.acs.org Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

1

Research Staff, Ford Motor Company, P.O. Box 2053, Dearborn, MI 48121 Department of Atmospheric and Oceanic Sciences, University of Michigan, Ann Arbor, MI 48109

2

In August, 1983, members of the Research Staff of Ford Motor Company c a r r i e d out a field experiment at two r u r a l s i t e s i n south western Pennsylvania involving various aspects of the a c i d deposition phenomenon. This presentation will focus on the wet (rain) deposi t i o n during the experiment, as w e l l as the r e l a t i v e importance of wet and dry deposition processes for n i t r a t e and sulfate at the s i t e s . Other aspects of the experiment have been discussed elsewhere: the chemistry of dew and its role in acid deposition (1), the dry deposition of HNO3 and SO2 to surrogate surfaces (2), and the role of elemental carbon in light absorption and of the latter in visibility degradation (3). EXPERIMENTAL

The experiment was conducted August 5-28, 1983 on abandoned radio towers atop Allegheny Mountain (elevation 838 meters) and Laurel Hill (elevation 850 meters, 35 km NW of Allegheny Mountain) i n southwestern Pennsylvania ( F i g . 1 ) . Both s i t e s are heavily forested and experience little l o c a l v e h i c l e traffic. A t t h e A l l e g h e n y M o u n t a i n s i t e a t m o s p h e r i c a e r o s o l and gas measurements, and l i g h t - s c a t t e r i n g and c o n d e n s a t i o n - n u c l e i - c o u n t m e a s u r e m e n t s , w e r e made a t o p t h e t o w e r 14 t o 17 m e t e r s a b o v e t h e ground. Wind speed and d i r e c t i o n , and atmospheric temperature, p r e s s u r e and h u m i d i t y , were c o n t i n u o u s l y r e c o r d e d . R a i n ( a n d dew) was c o l l e c t e d i n a 5 0 0 m^ mowed c l e a r i n g 60 m e t e r s n o r t h o f t h e tower. R a i n was c o l l e c t e d o n a n e v e n t b a s i s 1.8 m e t e r s above t h e ground i n t o t a r e d p o l y e t h y l e n e b o t t l e s , u s i n g a w e t - o n l y c o l l e c t o r (Wong L a b o r a t o r i e s M a r k V ) , e q u i p p e d w i t h a r e t r a c t i n g l i d a c t u a t e d by a r a i n s e n s o r . The s t a n d a r d c o l l e c t o r b u c k e t was s u p p l a n t e d b y a 30.5-cm diameter polyethylene funnel f i t t e d into the tared c o l l e c t i o n bottle. T h e r a i n f a l l a m o u n t ( i n mm o r i n 1 / m ) w a s d e t e r m i n e d f r o m the sample w e i g h t and the c o l l e c t o r geometry. T h e s a m p l i n g s e t u p was similar at Laurel H i l l . As s o o n as e a c h r a i n s t o p p e d , t h e s a m p l e was r e m o v e d , c a p p e d , and r e f r i g e r a t e d a t t h e s i t e . I t was t h e n t r a n s p o r t e d t o t h e f i e l d l a b o r a t o r y i n S o m e r s e t (midway b e t w e e n t h e s i t e s ) where i t was weighed and kept r e f r i g e r a t e d (never f r o z e n ) . The a n a l y t i c a l 2

0097-6156/87/0349-0028$06.00/0 © 1987 American Chemical Society

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

3.

Acid Deposition and Atmospheric Chemistry

PIERSON ET AL.

29

p r o c e d u r e s w e r e s i m i l a r t o t h o s e p r e v i o u s l y d e s c r i b e d ( 1 ) f o r dew samples. Q u a n t i t i e s m e a s u r e d i n c l u d e d pH, c o n d u c t i v i t y , t o t a l t i t r a t a b l e a c i d , a n d ( b y i o n c h r o m a t o g r a p h y ) SO^", NO3", NO2" , PO^", F", C I " , a n d B r " . The u n u s e d p o r t i o n s o f t h e r a i n s a m p l e s w e r e t r a n s p o r t e d t o Dearborn, s t i l l r e f r i g e r a t e d . Some 7 m o n t h s l a t e r t h e y w e r e r e a n a l y z e d ; t o s e l e c t e d s a m p l e s H 2 O 2 was a d d e d b e f o r e a n a l y s i s ( f i n a l [ H 2 O 2 ] = 1.5%) t o make c e r t a i n t h a t a l l S ( I V ) h a d b e e n o x i d i z e d t o sulfate. A t t h i s t i m e NH^ , Na a n d Κ w e r e d e t e r m i n e d b y i o n c h r o m a tography . A t m o s p h e r i c N O 2 , S O 2 , a n d O3 w e r e m e a s u r e d b y v a r i o u s m e t h o d s ( 1 , 4, 5 ) . l i g h t s c a t t e r i n g was m e a s u r e d b y i n t e g r a t i n g n e p h e l o meters. H N U 3 ( g ) a n d a e r o s o l N O 3 " w e r e m e a s u r e d b y t h e dénuder d i f f e r e n c e m e t h o d ( 6 - 8 ) u s i n g M g O - c o a t e d dénuder t u b e s a n d n y l o n membrane f i l t e r s , w i t h i o n c h r o m a t o g r a p h i c n i t r a t e d e t e r m i n a t i o n on a l k a l i n e f i l t e r e x t r a c t s . V a l i d ammonia d a t a w e r e n o t o b t a i n e d d u r i n g any o f t h e r a i n p e r i o d s . A e r o s o l s a m p l e s were c o l l e c t e d on f i l t e r s o f v a r i o u s t y p e s ( i n c l u d i n g i m p a c t o r s and v i r t u a l i m p a c t o r s ) and a n a l y z e d f o r H , ΝΗ^ , S 0 4 , and o t h e r components. The f i l t e r , dénuder, a n d impinger s a m p l e s w e r e c o l l e c t e d i n 1/2to 24-hour p e r i o d s s y n c h r o n i z e d w i t h each other but not g e n e r a l l y w i t h the onset or stop of r a i n . A c c o r d i n g l y i t s h o u l d be u n d e r s t o o d t h a t , i n t h e t r e a t m e n t that f o l l o w s , the atmospheric c o n c e n t r a t i o n s of a e r o s o l components, HNO3, a n d i m p i n g e r S O 2 t h a t we w i l l a s s o c i a t e w i t h t h e r a i n s a m p l e s a r e t h e average c o n c e n t r a t i o n s over the s e v e r a l - h o u r p e r i o d d u r i n g which the g i v e n r a i n o c c u r r e d , and n o t t h e c o n c e n t r a t i o n s j u s t d u r i n g the r a i n itself. I n s p e c t i o n o f t h e c o n t i n u o u s S O 2 , Ν 0 , O 3 , CNC a n d b t r a c e s i n d i c a t e s t h a t use o f the l o n g e r p e r i o d does not m a t e r i a l l y i n f l u e n c e the r e s u l t s .


+

+

+

=

χ

R E S U L T S AND

DISCUSSION

Rain Chemistry. The c h a r a c t e r i s t i c s o f t h e 17 r a i n e v e n t s a t t h e two s i t e s a r e s u m m a r i z e d a n d c o m p a r e d i n T a b l e 1 t o t h e dew s a m p l e s a n d t h e one s e t t l e d f o g w a t e r s a m p l e c o l l e c t e d a t A l l e g h e n y Mountain (1). (The dew was s a m p l e d i n a m a n n e r t h a t e x c l u d e d p r i o r dry d e p o s i t i o n . The r e p r e s e n t a t i v e n e s s o f t h e f o g w a t e r s a m p l e i s u n k n o w n - o t h e r f o g s o c c u r r e d b u t no s a m p l e s w e r e c o l l e c t e d . ) A number o f c o n c l u s i o n s c o n c e r n i n g r a i n a r e e v i d e n t f r o m T a b l e 1: •The r a i n was a c i d i c , w i t h t h e v o l u m e - a v e r a g e d pH o f 3.5 being p e r h a p s s o m e w h a t l o w e r t h a n t h a t o f t h e a v e r a g e summer r a i n i n the n o r t h e a s t (9-14). •H " a c c o u n t e d f o r a b o u t 9 0 % o f t h e t o t a l r a i n a c i d i t y . •The r a i n H c o u l d be a c c o u n t e d f o r i n t e r m s o f H 2 S O 4 and H N O 3 . •The S 0 4 / N 0 3 ~ e q u i v a l e n t s r a t i o o f a b o u t 3.7 i n t h e r a i n was c o m p a r a b l e t o t h a t c h a r a c t e r i s t i c o f summer r a i n s i n t h e n o r t h e a s t , i . e . , a b o u t 2.3 t o 4 ( 9 - 1 7 ) . •The L a u r e l H i l l r a i n s w e r e a b o u t 1 0 % m o r e c o n c e n t r a t e d i n a l l s p e c i e s than those c o l l e c t e d a t A l l e g h e n y M o u n t a i n ( i n agreement w i t h atmospheric a e r o s o l and t r a c e gas c o n c e n t r a t i o n s a t t h e sites). 4

+

=


30

dew

T H E CHEMISTRY OF ACID RAIN

When t h e c o m p o s i t i o n o f t h e r a i n i s c o m p a r e d w i t h t h a t o f t h e and t h e f o g , a number o f p o i n t s emerge: •While the ranges i n i o n c o n c e n t r a t i o n s , i n c l u d i n g H , are wider i n dew s a m p l e s , t h e r a n g e s o v e r l a p s o t h a t t h e dew was qualita t i v e l y s i m i l a r to d i l u t e r a i n . •The S 0 ^ / N 0 3 " c o n c e n t r a t i o n r a t i o i n t h e r a i n was a b o u t 3.7 e q u i v a l e n t s p e r e q u i v a l e n t v s . a r a t i o o f a b o u t 2.5 i n t h e dew. T h i s i s n o t s u r p r i s i n g s i n c e s i g n i f i c a n t amounts o f s u l f a t e are i n t r o d u c e d i n t o r a i n by n u c l e a t i o n s c a v e n g i n g (18) w h i l e a e r o s o l s u l f a t e d e p o s i t i o n t o dew i s m i n i m a l ( 1 ) . (In fact, at A l l e g h e n y M o u n t a i n ( 1 ) S O 2 was r e s p o n s i b l e f o r a b o u t 8 0 % o f t h e dew S0 ".) •There i s l i t t l e evidence of the presence of S(IV) i n the r a i n a n d f o g w a t e r s a m p l e s ( t h a t i s , no s i g n i f i c a n t i n c r e a s e i n s u l f a t e was s e e n b e t w e e n t h e p r o m p t a n d d e l a y e d a n a l y s e s ) . By c o n t r a s t , t h e r e i s e v i d e n c e o f c o n s i d e r a b l e S ( I V ) (up t o 40%) r e m a i n i n g u n o x i d i z e d i n t h e dew a t t h e e n d o f t h e n i g h t ( 1 ) . •The c h e m i s t r y o f t h e one s e t t l e d f o g w a t e r s a m p l e i s s i m i l a r t o t h a t o f t h e more c o n c e n t r a t e d rains. +

=


4

A c i d Deposition Fluxes i n Rain. Table 2 l i s t s cumulative a m o u n t s o f v a r i o u s s p e c i e s d e p o s i t e d p e r u n i t a r e a i n r a i n , dew and fog d u r i n g the experiment. T a b l e 2 a l s o shows t h e f l u x e s o b t a i n e d by d i v i d i n g t h e a c c u m u l a t i o n b y t h e sum o f c o l l e c t i o n t i m e s . The

CITIES

H •

INOUSTRIALOR POPULATIONO17000)CENTERS

Δ

COAL- FIRED POWER PLANTS > 1000

MW

χ (L E.LIVERPOOL o| 8 CHESTER . J Λ ALIQUIPPA

ί ! \ » \ I WEIRTON

F i g u r e 1. The Pennsylvania.

site

PITTSBURGH METROAREA "

of

the

field

experiment i n

southwestern



4

+

+

2+

2

2 +

"

"

delayed

"

"

η

prompt

"

"

"

„

106%

115 (67-271)

1.15 122

111%

(109-220)

1.16

(6-21)

262 (138-700) 8.5

(251-575)

299

256 (125-700)

8 (3-25)

(249-575)

86 (63-202) 294

68 (41-252)

373

81 (14-251)

0.99 159 107%

1.27 42 (10-137) 94%

26

387

73 (10-254)

5 (0.3-16)

230

32 (3-138)

-

0.6-1.3

0. 6-1.0

0. 7 (0.1-2.0)

155

41 (14-99)

70 (48-159)

53 (15-116) 39 (8-99)

340 144

91 (5.5-347)

350

3.47

Fog (n - l )

8 (0-55)

311 (257-550)

(3.5-5.3)

108 (16-382)

4.0

Dew (n - 15)

70 (61-119)

290 (178-741)

(3.3-3.6)

349 (317-615)

3.5

Rain - L a u r e l (n - 5) a

Volume-weighted averages are the amount o f a given species deposited per u n i t area throughout the experiment d i v i d e d by the amount o f water deposited per u n i t area throughout the experiment. The prompt and delayed s u l f a t e data are, r e s p e c t i v e l y , the f i e l d - l a b o r a t o r y r e s u l t s and the re-analyses 7 months l a t e r .

Does not include a l l fog events.

Λ accounted f o r

Λ, jumho cm*^

ϊ on balance Σ+/Σ-

α

SO4 "

3

N0 "

2

N0 "

Na , K , M g , C a

+

NH

H+

324 (227-763)

T i t r a t a b l e acid,

/ieq/liter

3.5 (3.1-3.75)

Rain - Allegheny (n - 12)

s e t t l e d fogwater (volume-weighted averages) *

Comparison of r a i n p r o p e r t i e s a t Allegheny and L a u r e l , August 1983, with Allegheny dew and

PH

Table 1.



32


g r e a t e r f r e q u e n c y o f r a i n a t A l l e g h e n y M o u n t a i n p r o d u c e d a b o u t a 4f o l d greater accumulation o f a l l i o n i c species there than a t L a u r e l Hill. T h i s r e f l e c t s t h e r a n d o m n e s s o f summer c o n v e c t i v e p r e c i p i t a t i o n ( a p p r o x i m a t e l y 7 0 % o f t h e r a i n a t A l l e g h e n y M o u n t a i n was convective i n nature). C o m p a r i s o n o f t h e d e p o s i t i o n e f f i c i e n c i e s o f r a i n , dew a n d f o g a t A l l e g h e n y M o u n t a i n shows t h a t d u r i n g t h e 2 1 - d a y e x p e r i m e n t , r a i n was r e s p o n s i b l e f o r t h e d e p o s i t i o n o f 60 t i m e s m o r e a c i d i t y ( t o g e t h e r w i t h r e l a t e d s p e c i e s ) t h a n w a s d e p o s i t e d d u r i n g dew p e r i o d s o r w i t h settled fogwater. P r e c i p i t a t i o n i n t h e v i c i n i t y o f A l l e g h e n y M o u n t a i n i s a b o u t 107 cm p e r y e a r ( 1 9 ) , o r c l o s e t o t h e r a t e r e c o r d e d i n T a b l e 2. I f t h e r a t i o b e t w e e n d e p o s i t i o n b y r a i n a n d d e p o s i t i o n t o dew d u r i n g t h e sampling p e r i o d i s a l s o r e p r e s e n t a t i v e o f t h eyear, then i t f o l l o w s t h a t t h e a n n u a l t o t a l a c i d d e p o s i t e d i n r a i n i s v e r y r o u g h l y 60 t i m e s a s g r e a t a s t h a t d e p o s i t e d t o dew o r i n s e t t l e d fogwater. S c a v e n g i n g R a t i o s f o r S0/, a n d N O 3 " b y R a i n . I f i t i s a s s u m e d t h a t t h e c o n c e n t r a t i o n o f a p o l l u t a n t i n p r e c i p i t a t i o n i s dependent on i t s c o n c e n t r a t i o n i n t h e a i r i n which t h ep r e c i p i t a t i o n forms, then t h e scavenging r a t i o , , c a nbe d e f i n e d as i - Ci /Ci =

W

r

a

Table 2. Deposition t o t a l s and deposition

fluxes associated

with r a i n a t

Allegheny and Laurel, August 1983; Allegheny dew and s e t t l e d fogwater shown f o r comparison Rain-Allegheny (n - 12)

Rain-Laurel (η - 5)

Dew (n - 15)

Fog (η - 1)

August 7-27 Accumulations: 2

Water g/m

T i t r a t a b l e a c i d peq/m H+

2

+

NH

S 0 " prompt 4

delayed

4513

295

(~210)

a

14800

4017

247

(~200)

a

a

(~590)

898

22

(~185)

88

(~140)

a

"

13100

3799

197

(~230)

a

"

13400

3860

220

(~230)

a

2

Water mg/m /sec

+

times) 1700

700

5

2

550

244

0.53

1.2

"

490

217

0.44

1.1

T i t r a t a b l e a c i d neq/m /sec

3.3

+

n

85

49

0.04

0.5

N0 _

w

115

60

0.16

0.8

NH

4

3

2

S 0 " prompt 4

delayed

a

1113

Fluxes (accumulations/collection

H

16500

2722

3440

3

2

12940

2570

4

_

N0

51000

"

440

206

0.35

1.28

"

450

209

0.39

1.24

Order-of-magnitude estimate, based on the estimate that 5 times as much was deposited during the experiment as i n the one 10-hour sample that was analyzed.

The représenta

tiveness o f the sample composition i s not known.


3.

a

33


PIERSON ET AL.

r

where C and Cj_ a r e t h e volume c o n c e n t r a t i o n s o f s p e c i e s i i n a i r ( e q u i v a l e n t s p e r cubic meter o f a i r ) and i n the r a i n w a t e r (equiva l e n t s p e r cubic meter o f l i q u i d water, i . e . , m i l l i - e q u i v a l e n t s p e r liter). The c a l c u l a t i o n o f s c a v e n g i n g r a t i o s u s i n g g r o u n d - l e v e l a t m o s p h e r i c d a t a f u r t h e r assumes t h a t t h e g r o u n d - l e v e l p o l l u t a n t d a t a are r e p r e s e n t a t i v e o f the a i r scavenged by a p r e c i p i t a t i n g cloud. This assumption appears a t l e a s t p a r t i a l l y j u s t i f i e d a t l o c a t i o n s remote enough from sources f o r v e r t i c a l m i x i n g t o have o c c u r r e d ( 1 8 ) . Washout r a t i o s f o r a e r o s o l S 0 4 a n d f o r t o t a l N O 3 " (HNO3 + a e r o s o l N O 3 " ) a r e p r e s e n t e d i n T a b l e 3. These washout r a t i o s p r e s u p p o s e , i n a c c o r d a n c e w i t h B a r r i e ' s t r e a t m e n t ( 1 8 ) , t h a t SO2 does not c o n t r i b u t e t o the r a i n S 0 a n d t h a t b o t h HNO3 a n d a e r o s o l N O 3 " contribute to the rain NO3'. Accordingly, the sulfate ratios are upper l i m i t s on W ; and t h e N O 3 " r a t i o s r e p o r t e d a r e c l o s e t o , and only s l i g h t l y less ^than, f o r HNO3 a l o n e s i n c e HNO3 i s h i g h l y s o l u b l e and dominates the ^total NO3". T h u s f r o m T a b l e 3, =


4

W

. - < a e r o s o l SO^

W... u

HNO3

=>

=

9 χ 10

5

19 χ 1 0

5

These r e s u l t s a r e s i m i l a r t o d a i l y - a v e r a g e d v a l u e s r e p o r t e d by B a r r i e (18) f o r s i t e s i n e a s t e r n Canada ( 1 9 7 8 - 1 9 8 1 ) . H i s mass scavenging r a t i o s , m u l t i p l i e d b y 890 ( t h e r a t i o b e t w e e n t h e d e n s i t y o f w a t e r a n d t h a t o f a i r a t t h e 838-m a l t i t u d e o f A l l e g h e n y M o u n t a i n i n o r d e r t o match u n i t s ) , g i v e t h e f o l l o w i n g averages f o r 4 remote l o c a t i o n s : W - 9 χ 1 0 t o 14 χ 1 0 f o r a e r o s o l S 0 ; W = 19 χ 1 0 t o 26 χ 4-10 f o r t o t a l N O 3 " ( H N O 3 + a e r o s o l N O 3 " ) . Forgone suburban/rural s i t e B a r r i e o b t a i n s \J = 10 χ 1 0 , W ^ = 11 χ 1 0 . S0 t-JM03 5

5

5

=

4

SQ

5

5

5

4

E s t i m a t i o n o f Wet a n d D r y A c i d . N O 3 " . a n d S0/^ Deposition Budgets a t Allegheny Mountain. To g a u g e t h e r e l a t i v e i m p o r t a n c e o f wet and d r y d e p o s i t i o n , t h e w e t - d e p o s i t i o n measurements need t o be accompanied by d r y - d e p o s i t i o n estimates. Nighttime dry deposition to dew was m e a s u r e d i n t h e p r e s e n t e x p e r i m e n t ( 1 ) , b u t we l a c k g o o d e s t i m a t e s o f d r y d e p o s i t i o n a t n i g h t w h e n dew was a b s e n t a n d , m o r e i m p o r t a n t , we l a c k a g o o d e s t i m a t e o f d r y d e p o s i t i o n d u r i n g t h e d a y when d e p o s i t i o n v e l o c i t i e s a r e e x p e c t e d t o be l a r g e s t . To d e a l w i t h t h i s d e f i c i e n c y two a l t e r n a t i v e a p p r o a c h e s a r e a d o p t e d a s f o l l o w s . F i r s t , n y l o n a n d T e f l o n 1 4 2 - m m - d i a m e t e r membrane f i l t e r s w e r e s e t o u t as s u r r o g a t e c o l l e c t i o n s u r f a c e s above t h e canopy a t A l l e g h e n y d u r i n g d a y l i g h t on f i v e days d u r i n g t h e 1983 e x p e r i m e n t , t o gauge t h e r e l a t i v e i m p o r t a n c e o f a e r o s o l N O 3 " and S 0 4 d e p o s i t i o n ( o n T e f l o n ) a n d t h e d e p o s i t i o n o f HNO3 a n d S 0 ( n y l o n - T e f l o n d i f f e r e n c e ) (2). The a p p l i c a b i l i t y o f s u r r o g a t e s u r f a c e s t o r e a l o n e s , h o w e v e r , i s q u e s t i o n a b l e on s e v e r a l grounds. F o r HNO3 t h e s t i c k i n g e f f i c i e n c y to n y l o n i s p r o b a b l y (20) 100%; f o r SO2 t h e s t i c k i n g e f f i c i e n c y i s l e s s t h a n 100% b u t g r e a t e r than z e r o ( 2 1 ) ; and s t i c k i n g e f f i c i e n c i e s a r e b y n o means t h e o n l y i s s u e . The s e c o n d a p p r o a c h i s t o u s e t h e m e a s u r e d a m b i e n t c o n c e n t r a tions i n combination with deposition v e l o c i t i e s reported i nthe literature (21-23). The t w o a p p r o a c h e s g i v e e f f e c t i v e l y t h e same r e s u l t s . For e x a m p l e , t h e a v e r a g e HNO3 d e p o s i t i o n v e l o c i t y m e a s u r e d b y m i c r o m e t e o r o l o g i c a l m e t h o d s a b o v e a f o r e s t i n e a s t T e n n e s s e e o r o n summer =

=

2



(Meq/1)

4

S07

Rain*

653

704 1181

44o

213

176

811

276

138

230

3

4

5

755

755

773

650

537

542

13

14

15

252

273

573

2

3

4

average

377

158

830

2.0 χ 10

17.3 x 10

(9.5

± 5.6)

χ

10

15.2 χ 10

864 1044

3.0 χ 10

17.3 x 10

7.0 χ 10

660

1066

754

7.1 χ 10

8.6 χ 10

849

3.8 χ 10

849

18.0 χ 10

849

980

13.1 χ 10

6.5 χ 10

41

5

5

5

5

5

5

5

5

194

72

63

135

161

252

212

79

139

5

5

150

63

63

70

58

(Meq/1)

Rain N0~

5

5

5

5

5

5

12.9 χ 10

4.7 χ 10

5.9 x 10

so=

w

^Results from the delayed analyses where available

392

1

226

755

284

12

Laurel H i l l

388

163

700

6

10

681

681

653

44o

260

207

213

2

3 3

103

117

83.8

78.5

77.8

41.6

81.7

74.6

74.6

74.6

154

87.5

43.4

21.3

21.3

55.8

55.8

3

8.6 χ 10 16.6 χ 10

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

8.0 χ 10

32.5 x 10

19.7 x 10

33.8 χ 10

28.4 χ 10

10.6 χ 10

9.0 χ 10

4.7 x 10

34.6 χ 10

29.6 χ 10

29.6 χ 10

12.5 x 10

10.4 χ 10

VNO

w

(19 + 11) χ 10

(neq/m )

t o t a l N0~

36.6

75.9

70.0

70.0

70.0

153

73.7

27.9

19.5

19.5

46.9

46.9

(neq/m )

M 0

Rain Scavenging Ratios f o r SO^ and N0~

(neq/m"

so

1

3

(neq/m )

Aerosol

2

Allegheny Mountain

Rain #

Table 3


3.

Sources of NO3"


August 5-28,

and SC>4~ deposition at Allegheny Mountain,

1983

a

N0

_

804

3

2

Rain (12 events) Fog

(1 event)

Dew

(15 events)

(neo/m *)

3440

Dry - without dew

Based on deposition to nylon surrogate substances not depositing to nylon

4

13400

140

230

88

220

2400

1 ^equivalent — 1 μπιοίε; f o r S 0

b

5000

e

2 μequivalents — 1 /zmole.

surfaces; does not

(e.g.,

E

2

(ueq/m )

For NO3"

35


PIERSON ET AL.

include

NO2).

Based on the measurement of dry deposition to nylon surrogate

surfaces

we

estimate that SO2 contributed about 5000 /xeq/m of dry deposition to the 2

S04

=

total.

Aerosol S04

=

adds another 300 μeq/m

2

or l e s s .




36

d a y s o v e r a n I l l i n o i s p a s t u r e ( 2 2 ) i s a b o u t t h e same a s t h e 2.5 + 1.5 cm/sec m e a s u r e d b y t h e s u r r o g a t e c o l l e c t o r s ( t o g e t h e r w i t h atmosp h e r i c c o n c e n t r a t i o n s ) i n the present experiment. T h e 0.5 c m / s e c S O 2 d e p o s i t i o n v e l o c i t y t o the surrogate c o l l e c t o r s i s i n the range r e p o r t e d t o v e g e t a t i o n (23) ( a v e r a g e - 0 . 7 c m / s e c ) . T h e 0.05 c m / s e c d e p o s i t i o n v e l o c i t y o f a e r o s o l S O ^ t o the surrogate c o l l e c t o r s i s i n the range g i v e n i n the l i t e r a t u r e (23). The r e s u l t s e m p l o y i n g d a y t i m e d r y d e p o s i t i o n e s t i m a t e s f r o m t h e s u r r o g a t e c o l l e c t o r s a r e g i v e n i n T a b l e 4; t h e s e e s t i m a t e s p r e s u p p o s e t h a t t h e f i v e d a y s a r e r e p r e s e n t a t i v e . W h i l e r a i n a c c o u n t e d f o r some 60% o f t h e N O 3 ' d e p o s i t i o n , d r y d e p o s i t i o n o f HNO3 i n t h e a b s e n c e o f dew a p p e a r s a l s o t o b e i m p o r t a n t . T h i s s i m i l a r t o t h e e s t i m a t e made by H u e b e r t (22) i n t h e I l l i n o i s e x p e r i m e n t t h a t HNO3 d r y d e p o s i t i o n accounted f o r 48% o f the NO3" wet/dry d e p o s i t i o n . For S 0 ^ deposit i o n , r a i n i s a g a i n t h e d o m i n a n t medium; h o w e v e r , t h e d r y d e p o s i t i o n o f S O 2 may a l s o b e i m p o r t a n t . The c o n t r i b u t i o n s o f d r y - d e p o s i t e d a e r o s o l n i t r a t e a n d s u l f a t e , n o t l i s t e d i n T a b l e 4, w e r e s m a l l ( a b o u t 5%) a t t h e s i t e . I f we now s u p p o s e t h a t S O 2 i s t a n t a m o u n t t o H 2 S O 4 i n a c i d i f y i n g p o t e n t i a l , o n g r o u n d s t h a t S O 2 r e a d i l y o x i d i z e s t o H 2 S O 4 , a n d i f we r e c a l l t h a t the NO3" and S 0 ^ i n the rain/dew/fog samples can be r e g a r d e d a s m o s t l y HNO3 a n d H 2 S O 4 , t h e n t h e t o t a l s t r o n g a c i d d e p o s i t e d i n the experiment can be a p p o r t i o n e d from T a b l e IV r o u g h l y as f o l l o w s : 47% = H2SO4 i n r a i n (34% S O 2 s c a v e n g i n g , 1 3 % a e r o s o l S O ^ scavenging) 2 3 % = S O 2 d r y d e p o s i t i o n w i t h o u t dew 16% = HNO3 i n r a i n 1 1 % = H N O 3 d r y d e p o s i t i o n w i t h o u t dew =

=

3%

= HNO3

and H2SO4

i n f o g a n d dew +

At the r a t e s i m p l i e d b y Table IV, t o t a l wet and dry H d e p o s i t i o n w o u l d b e a b o u t 300 moles H / h e c t a r e / m o n t h - i n A u g u s t . +

ACKNOWLEDGMENTS We a r e p l e a s e d t o a c k n o w l e d g e t h e a s s i s t a n c e o f t h e P e n n s y l v a n i a T u r n p i k e C o m m i s s i o n i n p r o v i d i n g a c c e s s a n d e l e c t r i c power t o t h e two s i t e s a n d h e l p i n g u s s e t u p t h e e x p e r i m e n t ; we a r e e s p e c i a l l y i n d e b t e d t o W a r r e n E. K i p p , R o b e r t E. D a v i s , N e v i n A. M i l l e r , C a r l Baker a n d the crew a t the A l l e g h e n y Mountain Tunnel, and the C h i e f Engineer and Deputy E x e c u t i v e D i r e c t o r o f the P e n n s y l v a n i a Turnpike C o m m i s s i o n , R o b e r t H. K l u c h e r . A t F o r d , we a r e i n d e b t e d t o R i c h a r d F l o y d , L e e C. W e s t w o o d , Y. T. L i u , a n d G. E. F i s h e r f o r t h e i r p a r t i c i p a t i o n i n the chemical a n a l y s i s . Ford p a r t i c i p a n t s i n the f i e l d e x p e r i m e n t i t s e l f i n c l u d e d K a r e n M. A d a m s , J a m e s W. B u t l e r , A n n C. C l e a r y , J a m e s C. D z i a d o s z , L a r r y P. H a a c k , Thomas J . K o r n i s k i , W i l l i a m K. O k a m o t o , a n d M i c h a e l J . R o k o s z . J e f f r e y M. M a s t e r s , f o r m e r l y o f the U n i v e r s i t y o f Michigan, p a r t i c i p a t e d i n the f i e l d and handled the o n - s i t e meteorology. P r o f . P e r r y J . Samson o f t h e U n i v e r s i t y o f M i c h i g a n a s s i s t e d i n the t r a j e c t o r y a n a l y s i s and meteorology. We t h a n k W i l l i a m J . C o u r t n e y o f N o r t h r o p S e r v i c e s a n d Thomas G. D z u b a y , C h a r l e s W. L e w i s , a n d R o b e r t K. S t e v e n s o f E P A / E S R L for t h e i r c o l l a b o r a t i o n i n c l u d i n g f i e l d i n t e r c a l i b r a t i o n and the use


3.

PIERSON ET AL.


37

of their instruments. We a r e g r a t e f u l t o E . E u g e n e W e a v e r , who r e t u r n e d from F o r d r e t i r e m e n t to h e l p , w i t h A d e l e Weaver, on the f i e l d experiment. We t h a n k P r o f . J a m e s A . L y n c h o f t h e P e n n s y l v a n i a S t a t e U n i v e r s i t y f o r s h a r i n g d e t a i l e d r a i n d a t a w i t h us from h i s Laurel H i l l site. O u r w o r k was s u p p o r t e d i n p a r t b y t h e N a t i o n a l Science Foundation under I n d u s t r y / U n i v e r s i t y Cooperative Research G r a n t NO. A T M - 8 5 0 7 2 8 2 t o t h e U n i v e r s i t y o f M i c h i g a n .

LITERATURE CITED


(1)

(2)

(3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)

Pierson, W.R., Brachaczek, W.W., Gorse, R.A., Jr., Japar, S.M. and Norbeck, J.M., Paper No. 85-7.4, Air Pollution Control Association 78th Annual Meeting, Detroit, June (1985); J. Geophys. Res. 91, 4083 (1986). Japar, S.M., Brachaczek, W.W., Gorse, R.A., Jr., Norbeck, J.M. and Pierson, W.R., presented at Muskoka '85: International Symposium on Acidic Precipitation, Minett, Ontario, September (1985). Japar, S.M., Brachaczek, W.W., Gorse, R.A., Jr., Norbeck, J.M., and Pierson, W.R., Atmos. Environ. 20, 1281 (1986). Holdren, M.W. and Spicer, C.W., Environ, Sci. Tech., 18, 113 (1984). Pierson, W.R., Brachaczek, W.W., Truex, T.J., Butler, J.W., and Korniski, T.J., Annals N.Y. Acad. Sci. 338, 145 (1980). Appel, B.R., Tokiwa, Υ., and Haik, Μ., Atmos. Environ. 15, 283 (1981). Shaw, R.W., Jr., Stevens, R.K., Bowermaster, J . , Tesch, J.W., and Tew, E., Atmos. Environ. 16, 845 (1982). Spicer, D.W., Howes, J.E., Jr., Bishop, T.A., Arnold, L.H., and Stevens, R.K., Atmos. Environ. 16, 1487 (1982). Bowersox, V.C. and de Pena, R.G., J. Geophys. Res. 85, 5614 (1980). Bowersox, V.C. and Stensland, R.G., Paper No. 81-6.1, Air Pollution Control Association 74th Annual Meeting, Philadelphia, June (1981). Altwicker, E.R. and Johannes, A.H., Paper No. 81-6.2, Air Pollution Control Association 74th Annual Meeting, Philadelphia, June (1981) Pack, D.H., Atmos. Environ. 16, 1145 (1982). Hales, J.M., et al, Atmos. Environ. 16, 1603 (1982). Pratt, G.C. and Krupa, S.V., Atmos. Environ. 17, 1845 (1983). Galloway, J.N. and Likens, G.E., Atmos. Environ. 15, 1081 (1981). Henderson, R.G. and Weingartner, Κ., Atmos. Environ. 16, 1657 (1982) Wilson, W.E. and Husar, R.B., Society of Automotive Engineers Technical Paper Series, Paper No. 830647 (1983). Barrie, L.A., J. Geophys. Res. 90, 5789 (1985). National Oceanographie and Atmospheric Administration, Climates of the States. Vol. 2 (Gale Research Co., Detroit (1978)), P. 852. Durham, J.L. and Stockburger, L., Atmos. Environ. 20, 559 (1986). Fowler, D., Atmos. Environ. 12, 369 (1978).


38


22) Huebert, B.J. and Robert, C H . , J. Geophys. Res. 90, 2085 (1985) . (23) Schmel, G.A., Atmos. Environ. 14, 983 (1980).


RECEIVED May 15, 1987


Acid Deposition and Atmospheric Chemistry at Allegheny Mountain

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