Atmospheric Aerosol - ACS Publications - American Chemical Society

6

Air Particulate Control Strategy Development A New Approach Using Chemical Mass Balance Methods JOHN E. CORE—Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Downloaded by SUFFOLK UNIV on January 17, 2018 | http://pubs.acs.org Publication Date: October 13, 1981 | doi: 10.1021/bk-1981-0167.ch006

PATRICK L. HANRAHAN—Oregon Department of Environmental Quality, P.O. Box 1760, Portland, OR 97207 JOHN A. COOPER—Oregon Graduate Center, 1900 N.W. Walker Road, Beaverton, OR 97006

Recent advances in source apportionment receptor models have, for the f i r s t time, led to the development of regional particulate control strategies. Source impacts assigned using a Chemical Mass Balance (CMB) model, have been used with dispersion modeling to identify emission inventory deficiencies and improve modeling assumptions. The Chemical Mass Balance model is a method of assigning source impacts given detailed information on the chemical "fingerprint" of both the ambient particulate and source emissions within the airshed. Quantitative estimates of source contribution were identified with relative uncertainties ranging from ±5% to 30%. Dispersion model source impact estimates, following comparison to the CMB results, were significantly improved after emission inventory deficiencies were corrected. Final modeling results then provided r e a l i s t i c source impact estimates which could be confidently used for strategy development. Presented as an overview of the State of Oregon's unique approach to particulate control strategy development, this review was prepared to provide those responsible for airshed management with new information on source impact assessment methods. (This material is available in the form of an audio-visual program suitable for presentation before public, regulatory or private interest groups).

0097-6156/81/0167-0107$05.00/0 © 1981 American Chemical Society

Macias and Hopke; Atmospheric Aerosol ACS Symposium Series; American Chemical Society: Washington, DC, 1981.


108

ATMOSPHERIC

AEROSOL

P o r t l a n d , E u g e n e , and M e d f o r d , O r e g o n a r e t h r e e c i t i e s w h i c h s h a r e a n a i r p o l l u t i o n p r o b l e m common t o many o t h e r communities a c r o s s t h e c o u n t r y - suspended particulate air quality violations. Paced w i t h l i m i t e d a i r s h e d c a p a c i t y , e x p a n d i n g e m i s s i o n growth and C l e a n A i r A c t r e q u i r e m e n t s t o a t t a i n p a r t i c u l a t e a i r q u a l i t y s t a n d a r d s , t h e Oregon D e p a r t m e n t o f E n v i r o n m e n t a l Q u a l i t y , i n 1975, b e g a n a f i v e y e a r program o f d a t a c o l l e c t i o n d e s i g n e d t o understand each community's problem. The purpose o f t h e s e programs has been t o p r o v i d e t h e b e s t t e c h n i c a l i n f o r m a t i o n p o s s i b l e upon w h i c h c o n t r o l s t r a t e g i e s c a n be b u i l t . R e s u l t s f r o m t h i s work h a v e p l a y e d a key r o l e i n i d e n t i f y i n g c o n t r i b u t i n g s o u r c e s , improvi n g m o d e l i n g r e s u l t s and i n a d o p t i n g c o n t r o l p r o g r a m s t h a t t h e D e p a r t m e n t and t h e community c a n i m p l e m e n t w i t h c o n f i d e n c e . T h i s i s a b r i e f review o f t h e Department's approach t o c o n t r o l s t r a t e g y development. I t i s unique because i t combines t h e a d v a n t a g e s o f two d i f f e r e n t s o u r c e a p p o r t i o n m e n t m o d e l s to a r r i v e a t t h e source impact i n f o r m a t i o n used i n s t r a t e g y development: a C h e m i c a l M a s s B a l a n c e (CMB) M o d e l t o e s t i m a t e s o u r c e impacts u s i n g measured ambient p a r t i c u l a t e c o m p o s i t i o n d a t a , and t r a d i t i o n a l d i s p e r s i o n m o d e l e s t i m a t e s o f i m p a c t s . A l t h o u g h d i s p e r s i o n m o d e l i n g and C h e m i c a l Mass B a l a n c e m e t h o d s have been used i n s e v e r a l source apportionment s t u d i e s , t h e work r e p o r t e d h e r e r e p r e s e n t s t h e f i r s t attempt t o b r i n g t h e b e s t f e a t u r e s o f these t e c h n i q u e s t o g e t h e r w i t h i n t h e framework o f a s i n g l e s t u d y ( 1 , 2 ) . The p r i m a r y f o c u s h e r e i s on work c o m p l e t e d i n t h e P o r t l a n d A i r Q u a l i t y Maintenance a r e a i n Northwest Oregon, a l t h o u g h t h e improvements t o t h e m e t e o r o l o g i c a l d a t a , emiss i o n i n v e n t o r i e s and d i s p e r s i o n m o d e l h a v e b e e n c o m p l e t e d i n a l l three c i t i e s . D a t a B a s e Improvement P r o g r a m s I n 1970, new e f f o r t s were u n d e r w a y t o s o l v e P o r t l a n d ' s suspended p a r t i c u l a t e problem. E a r l y e f f o r t s r e l i e d on a v a i l a b l e e m i s s i o n f a c t o r s and i n d u s t r i a l s o u r c e t e s t i n g , as a b a s i s f o r t h e e m i s s i o n i n v e n t o r y . T h e i n v e n t o r y was t h e n u s e d , w i t h a p r o p o r t i o n a l r o l l b a c k m o d e l , a s a b a s i s f o r t h e new strategy. New i n d u s t r i a l c o n t r o l s were i n s t a l l e d w h i c h r e s u l t e d i n a 60,000 t o n s p e r y e a r r e g i o n - w i d e r e d u c t i o n i n i n d u s t r i a l emissions. A l t h o u g h p r o g r e s s toward c l e a n e r a i r was made, a i r q u a l i t y s t a n d a r d v i o l a t i o n s c a u s e d b y t h e n unknown s o u r c e s c o n t i n u e d and m o d e l i n g e f f o r t s f a i l e d t o a c c o u n t f o r o v e r o n e - h a l f o f t h e p a r t i c u l a t e mass. A new a p p r o a c h t o i d e n t i f y i n g c o n t r i b u t i n g s o u r c e s was b a d l y n e e d e d i f a new r o u n d o f e m i s s i o n c o n t r o l r e g u l a t i o n s were t o b e s u c c e s s f u l . Following t e c h n i c a l review of the a l t e r n a t i v e s , a comprehensive p l a n i n c o r p o r a t i n g a Chemical Mass B a l a n c e ( 3 , 4 ) r e c e p t o r m o d e l was a d o p t e d . This


6.

CORE E T A L .

technique by

Air

Particulate

distinguishes

statistically

Control

source

matching

Strategy

109

contributions

the r e s u l t s

from

from

one

extensive

another chemical

a n a l y s i s o f ambient p a r t i c u l a t e to t h o s e o b t a i n e d from s o u r c e s i n the a i r s h e d . I n P o r t l a n d , c e r t a i n s o u r c e s were e a s i l y i d e n t i f i e d u s i n g " t r a c e r " elements u n i q u e l y a s s o c i a t e d w i t h one s o u r c e . A u t o m o t i v e e x h a u s t , f o r example, i s by f a r t h e l a r g e s t source of lead. O t h e r e m i s s i o n s , such as r e - e n t r a i n e d r o a d d u s t , must be i d e n t i f i e d u s i n g a number o f e l e m e n t s , none o f w h i c h a r e u n i q u e t o any one s o u r c e . The o v e r a l l p r o g r a m d e s i g n c o n s i s t e d o f a f i v e - s t e p l e a d i n g to S t a t e Implementation P l a n r e v i s i o n s :


1.

Identification

of

source

contributions

i n the

process ambient

a i r u s i n g the C h e m i c a l Mass B a l a n c e . T h i s w o r k was c o m p l e t e d p a r t o f t h e P o r t l a n d A e r o s o l C h a r a c t e r i z a t i o n S t u d y , PACS. 2. D i s p e r s i o n model e s t i m a t e s o f s o u r c e u s i n g s o u r c e e m i s s i o n and m e t e o r o l o g i c a l d a t a p e r i o d o f PACS s a m p l i n g ;

as

contributions f o r t h e one y e a r

3. C o m p a r i s o n o f t h e PACS-CMB s o u r c e i m p a c t the d i s p e r s i o n model-predicted source impacts;

estimates

to

4. C o m p l e t i o n o f e m i s s i o n i n v e n t o r y and m o d e l i n g assumpimprovements t o match d i s p e r s i o n model s o u r c e impacts t o

tion CMB

results;

The

5. D i s p e r s i o n modeling of c o n t r o l s t r a t e g y a l t e r n a t i v e s . f i r s t s t e p i n t h e p l a n was one o f s o u r c e i d e n t i f i c a t i o n

and

based

on a i r s a m p l e s . A f t e r a y e a r o f s t a f f d e s i g n , f u n d r a i s i n g and r e v i e w o f t h e m e t e o r o l o g i c a l , e m i s s i o n i n v e n t o r y and m o d e l i n g a d e q u a c y , t h e P o r t l a n d A e r o s o l C h a r a c t e r i z a t i o n Study (PACS), Step 1 o f the p l a n , began. P a r t i c i p a t i o n by l o c a l g o v e r n m e n t , b u s i n e s s

i n t e r e s t s and i n d u s t r y was a c t i v e l y s o u g h t t h r o u g h o u t t h e PACS d e s i g n , s a m p l i n g and d a t a a n a l y s i s p h a s e s i n t h e hope t h a t a l l s e c t o r s o f t h e community c o u l d g a i n c o n f i d e n c e i n t h e s t u d y results. A p u b l i c a d v i s o r y c o m m i t t e e was f o r m e d t o h e l p g u i d e the p r o j e c t The

and

reveiw

early

PACS s t u d y was

drafts.

a three year

effort

designed

to iden-

t i f y major a e r o s o l source types w i t h i n the P o r t l a n d A i r Q u a l i t y M a i n t e n a n c e A r e a and q u a n t a t i v e l y d e t e r m i n e t h e i r c o n t r i b u t i o n to p a r t i c u l a t e l e v e l s . The PACS r e p r e s e n t s t h e f i r s t m a j o r s t u d y d e s i g n e d from the b e g i n n i n g to p r o v i d e a l l of the d a t a r e q u i r e d by t h e CMB method. F i n e and c o a r s e p a r t i c u l a t e s a m p l e s f r o m 37 s o u r c e s , r e p r e s e n t i n g 95% o f P o r t l a n d e m i s s i o n i n v e n t o r y w e r e c h e m i c a l l y c h a r a c t e r i z e d f o r 27 c h e m i c a l s p e c i e s . The same s p e c i e s were m e a s u r e d on

over

2000 i n d i v i d u a l

fine

and

coarse

ambient p a r t i c u l a t e samples o v e r a one-year p e r i o d . Six sampling l o c a t i o n s r e p r e s e n t i n g background a i r q u a l i t y ; r e s i d e n t i a l , c o m m e r c i a l and i n d u s t r i a l l a n d u s e a r e a w e r e i n c l u d e d i n t h e s t u d y , r e s u l t i n g i n o v e r 1700 CMB c a l c u l a t i o n s . The s o u r c e c o n t r i b u t i o n e s t i m a t e s d e r i v e d f r o m t h e CMB work were s t r a t i f i e d b y m e t e o r o l o g i c a l r e g i m e , s e a s o n o f t h e y e a r , sampl i n g s i t e and p a r t i c l e s i z e f r a c t i o n .



110

ATMOSPHERIC

AEROSOL

P o r t l a n d A e r o s o l C h a r a c t e r i z a t i o n Study Results Sources of P o r t l a n d ' s t o t a l suspended p a r t i c u l a t e mass (Figure 1) were s u c c e s s f u l l y i d e n t i f i e d by Chemical Mass Balance methods (5). The key r e s u l t s of the study were as follows: * S o i l and road dust was found to be the l a r g e s t s i n g l e source, accounting f o r 55% of the p a r t i c u l a t e . Although s e v e r a l minor sources of r u r a l dust were included i n the area's inventory, the study i d e n t i f i e d a 19,400 ton per year d e f i c i e n c y i n the paved road dust emission inventory. ^Vegetative burning was found to account f o r as much as 40% of the t o t a l p a r t i c u l a t e mass on c o l d winter days, or n e a r l y 9% annually. T h i s l e d to the i d e n t i f i c a t i o n of a source of 6500 tons/year of p r e v i o u s l y uninventoried emissions and prompted major e f f o r t s to reduce impacts from r e s i d e n t i a l wood burning. ^ I n d u s t r i a l emissions c o l l e c t i v e l y accounted f o r only 5% o f the p a r t i c u l a t e mass, a r e s u l t that was not s u r p r i s i n g given that these sources were w e l l cont r o l l e d before f i e l d sampling began. Some i n d u s t r i a l source impacts, however, may not have been i d e n t i f i a b l e because of emissions that chemic a l l y resembled g e o l o g i c sources. ^Secondary p a r t i c u l a t e s were found to account f o r about 8% and automotive exhaust about 10% of the annual average mass. In a l l , about 92% of the t o t a l suspended p a r t i c u l a t e mass was assigned to s p e c i f i c sources or chemical c l a s s e s with the remaining 8% l i k e l y made up of water, ammonium s a l t s and other u n i d e n t i f i e d s p e c i e s . Figure 2 shows the composition and source c o n t r i b u t i o n s to the f i n e p a r t i c u l a t e f r a c t i o n l e s s than 2.5um. F i g u r e r e f e r e n c e s to v o l a t i l i z a b l e and n o n - v o l a t i l i z a b l e carbon are o p e r a t i o n a l d e f i n i t i o n s (6) f o r organic carbon ( v o l a t i l e i n an oxygen-free atmosphere at temperature l e s s than 850°C) and elemental carbon. These c l a s s i f i c a t i o n d i f f e r from v e g e t a t i v e burning i n that they i n c l u d e only carbon whereas burning emissions are about 60-70% carbon. Fine p a r t i c l e sources were a l s o i d e n t i f i e d and used d u r i n g e v a l u a t i o n s of c o n t r o l s t r a t e g y a l t e r n a t i v e s . D i s p e r s i o n Model Estimates of Source Impacts Step 2 r e q u i r e d i d e n t i f i c a t i o n of source impacts by a i r s h e d modeling. Wind speed, d i r e c t i o n , mixing height, and emission data bases designed to represent c o n d i t i o n s on PACS sampling days were used to insure that the CMB impact estimates could be d i r e c t l y compared to model p r e d i c t i o n s f o r each sampline s i t e . The P o r t l a n d a i r s h e d d i s p e r s i o n model GRID (7) i s a cons e r v a t i o n of mass, a d v e c t i o n - d i f f u s i o n code designed to perform



CORE ET A L .

Figure 1.

Figure 2.

Air

Particulate

Control

Strategy

11

Sources of total particulate: annual average of the downtown Portland sampling site

Sources of fine particulate: annual average of the downtown Portland sampling site



112

ATMOSPHERIC

AEROSOL

w e l l i n the rough t e r r a i n that c h a r a c t e r i z e s the P o r t l a n d a r e a . R e q u i r e d i n p u t s f o r e a c h o f t h e 5000, 2km g r i d c e l l s i n c l u d e t o p o g r a p h y and w i n d f l o w f i e l d s by h o u r f o r e a c h o f e i g h t m e t e o r o l o g i c a l regimes i n t o which the annual weather p a t t e r n s were c l a s s i f i e d . S p a t i a l l y and s e a s o n a l l y r e s o l v e d p o i n t and a r e a s o u r c e e m i s s i o n s and s t a c k p a r a m e t e r s were a l s o d e v e l o p e d . T h r e e s o u r c e c l a s s e s w e r e s e l e c t e d f o r c o m p a r i s o n o f CMB and m o d e l r e s u l t s . Two were o f an a r e a s o u r c e n a t u r e ( r o a d d u s t and a u t o m o t i v e e x h a u s t ) and one p o i n t s o u r c e c a t e g o r y ( r e s i d u a l o i l combustion). T h e s e s o u r c e s were s e l e c t e d f o r comparison f o r the f o l l o w i n g reasons: * D u s t f r o m p a v e d and u n p a v e d r o a d s i s t h e most predominant source i n P o r t l a n d . Accurate emissions d a t a i s c r i t i c a l t o the model's a b i l i t y to account f o r a l l o f t h e m e a s u r e d mass, as w e l l as t o t h e development of a s u c c e s s f u l s t r a t e g y . Although the CMB m o d e l c a n n o t d i s t i n g u i s h b e t w e e n d u s t e m i s s i o n s f r o m p a v e d and u n p a v e d r o a d s , i t c a n t y p i c a l l y a s s i g n t o t a l d u s t i m p a c t s t o w i t h i n a 5-6% u n c e r t a i n t y . ^ L e a d e d a u t o m o t i v e t a i l p i p e e x h a u s t was selected b e c a u s e i t c a n be a c c u r a t e l y e s t i m a t e d by CMB and i s t h e t h i r d most a b u n d a n t c o n t r i b u t o r t o t h e a n n u a l p a r t i c u l a t e mass, a f t e r r o a d d u s t and v e g e t a t i v e burning. ^ R e s i d u a l o i l combustion impact s e r v e d as a t e s t of the model's a b i l i t y to p r e d i c t p o i n t source e m i s s i o n s . S i n c e v a n a d i u m and n i c k e l e m i s s i o n s i n P o r t l a n d a r e almost t o t a l l y a s s o c i a t e d w i t h r e s i d u a l o i l use, the CMB method was a b l e t o a s s i g n i m p a c t s w i t h a h i g h d e g r e e o f c o n f i d e n c e b y u s i n g t h e s e two e l e m e n t s a s chemical tracers. Model p r e d i c t i o n s f o r t h e s e s o u r c e s were p r e p a r e d f o r each of e i g h t m e t e o r o l o g i c a l regimes, a p p r o p r i a t e l y weighted and c o m b i n e d t o p r o v i d e a n n u a l i m p a c t e s t i m a t e s f o r e a c h g r i d and e a c h PACS m o n i t o r i n g s i t e . C o m p a r i s o n o f CMB a n d D i s p e r s i o n M o d e l I m p a c t E s t i m a t e s S t e p 3 was a c o m p a r i s o n o f t h e CMB a n d GRID m o d e l i m p a c t estimates. CMB-estimated source c o n t r i b u t i o n s t o the backg r o u n d a e r o s o l i m m e d i a t e l y u p w i n d o f t h e s t u d y a r e a were s u b t r a c t e d from those o b t a i n e d from the urban s i t e d a t a to p r o v i d e a " l o c a l CMB" v a l u e a g a i n s t w h i c h t h e GRID d i s p e r s i o n m o d e l c o u l d be compared. Data c o l l e c t e d d u r i n g the Northw i n d Regime was u s e d d u r i n g t h i s work s i n c e c o m p u t e r s i m u l a t i o n c o s t s were o n l y o n e - e i g h t h o f t h a t r e q u i r e d f o r an annual s i m u l a t i o n . I n i t i a l source apportionment estimates f r o m t h e s e two m o d e l s were a s f o l l o w s : ^Automotive exhaust comparisons (shown i n F i g u r e 3) a t t h r e e s i t e s w e r e w e l l w i t h i n t h e CMB e s t i m a t e d u n c e r t a i n t y . One o f t h e s i t e s , h o w e v e r , a p p e a r e d t o be u n d e r p r e d i c t e d . Although


6.

CORE E T A L .

a

Air

closer

near

Control

examination

Site

impact

Particulate

5 was

Strategy

of the

needed,

1

emission

the

initial

inventory CMB-model

c o m p a r i s o n s were e n c o u r a g i n g .

This

initial

comparison

indicated

t h a t t h e P o r t l a n d GRID

dispersion

model was

able to

exhaust

impacts

and

area

simulate

source

cell

automotive

emissions

reasonably

well. *Road d u s t

comparisons

shown i n F i g u r e 4 w e r e

poor

w i t h major u n d e r p r e d i c t i o n s a t a l l l o c a t i o n s by GRID m o d e l . it

could r e a l i s t i c a l l y

^Residual


a

More work was

severe

impact

o i l impact test

3

5)

further Overall, sources

improvements

and

Emission

TSP

Inventory

CMB-dispersion

mass

model

been compared

source Step the

emission

tions

predictions

then,

used

impacts t o CMB

source

t o be

d a t a b a s e were results

both

the

suggested.

for a l l

and

data. identified

o n l y t o measured to

exhaust

which and

tripled

improving

model's

tail

The

and

heavily

traveled

r e s u l t s w e r e as calculation

incorrectly helped

follows:

e r r o r s were near

Site

assigned

O i l impact

the

to a

grid

nearly

from

boundary

neighboring

found

5 a

was

grid.

This

the model u n d e r p r e d i c t i o n s .

o v e r p r e d i c t i o n s were t r a c e d t o

errors:

*The e m i s s i o n s stant

by

when e m i s s i o n s

near

t o e x p l a i n some o f

Residual three

caused

road

into

m e t e o r o l o g i c a l assump-

pipe emissions

e r r o r was

inade-

strategy's success.

i n c r e a s e d t h e model p r e d i c t e d impact

10%.

were i n c o r r e c t l y

throughout

modification accomodate each

The

emission

the

particulate model

the

data

had

i n v e n t o r y and

to the

inventory, modeling

i n the modeling.

pre-

CMB-derived

i n v o l v e d n e a r l y s i x months o f r e s e a r c h

Auto

over-

estimates,

have been apparent

emission

however, c r i t i c a l

impact

4,

inher-

point

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ATMOSPHERIC AEROSOL

114

1:1 S L O P E LINE


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Model Predictions (ng/m ) 3

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Figure 4. Road dust impacts—north wind regime (initial predictions)

15

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Model Predictions 3

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/


6.

CORE

E T A L .

Air Particulate

Control

115

Strategy

a c c e p t a s i n g l e v a l u e p e r c e l l as t h e ground e l e v a t i o n , e r r o r s caused by t o p o g r a p h i c a l v a r i a t i o n s w i t h i n a c e l l were i n t r o d u c e d . The model c o n s i s t s o f f i v e c e l l s i n t h e v e r t i c a l d i r e c t i o n t o accomodate v e r t i c a l d i f f e r e n c e s i n w i n d s p e e d and d i r e c t i o n . B e c a u s e t h e downwind plume i m p a c t i s a s s i g n e d t o one of t h e f i v e v e r t i c a l c e l l s , r e l a t i v e l y minor changes i n plume h e i g h t c a n r e s u l t i n m a j o r c h a n g e s i n p r e d i c t e d c o n c e n t r a t i o n s a t t h e r e c e p t o r i f t h e change moves t h e plume i n t o t h e g r o u n d l e v e l c e l l . To c o r r e c t t h e e r r o r s , s t a c k h e i g h t s i n each c e l l had t o be a d j u s t e d t o r e f l e c t d i f f e r e n c e s between t h e t r u e s t a c k and r e c e p t o r h e i g h t s . * L a r g e i m p a c t s f r o m one o f t h e a i r s h e d ' s m a j o r s o u r c e s was t r a c e d t o a n u n r e a l i s t i c o p e r a t i n g schedule. F o l l o w i n g c o r r e c t i o n s , r e s i d u a l o i l impacts agreed q u i t e w e l l w i t h CMB e s t i m a t e s . Road d u s t u n d e r p r e d i c t i o n s , b a s e d o n t h e i n i t i a l EPA g e n e r a l i z e d p a v e d r o a d d u s t f a c t o r , were t h e most s e r i o u s problem. S i n c e t h e r e a r e v e r y few unpaved r o a d s w i t h i n t h e AQMA, a t t e n t i o n t u r n e d t o upward adjustment o f t h e paved road dust e m i s s i o n f a c t o r . A m o d i f i e d e m i s s i o n f a c t o r ( E F ) was d e v e l o p e d based on a n assumed c o n s i s t e n t r e l a t i o n s h i p b e t w e e n p a r t i c u l a t e t a i l p i p e and r o a d d u s t i m p a c t : EF

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impact

CMB paved road

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road

dust

impact

F u r t h e r s e a s o n a l a d j u s t m e n t s i n t h e new f a c t o r were made t o a c c o u n t f o r r a i n f a l l . F i n a l l y , d a t a f r o m s t u d i e s i n S e a t t l e , W a s h i n g t o n (8) s u g g e s t e d a 10 t o 20 f o l d i n c r e a s e i n s t r e e t d u s t e m i s s i o n s i n heavy i n d u s t r i a l a r e a s a s compared t o c o m m e r c i a l , land use a r e a s . A d j u s t m e n t s w e r e made t o e a c h g r i d ' s e m i s s i o n s b a s e d o n i n f o r m a t i o n f r o m l a n d u s e maps a n d d e t a i l e d d a t a o n unpaved roads. The f i n a l r o a d d u s t i n v e n t o r y was i n c r e a s e d b y 19,400 t o n s p e r y e a r , a 600% i n c r e a s e i n r o a d d u s t e m i s s i o n s . Even s o , t h e o v e r a l l AQMA e m i s s i o n f a c t o r o f 3.2 grams p e r v e h i c l e m i l e i s l e s s t h a n t h e 5.6 grams p e r v e h i c l e m i l e c u r r e n t l y recommended by EPA. M o d e l e d s t r e e t d u s t i m p a c t s now a g r e e d w i t h CMB r e s u l t s shown i n F i g u r e 6. As a r e s u l t o f t h e s e adjustments, t h e u p d a t e d e m i s s i o n i n v e n t o r y was i n c r e a s e d s u b s t a n t i a l l y (see F i g u r e 7). Road d u s t i s now e s t i m a t e d t o b e o v e r o n e - h a l f of the t o t a l emissions. A s a r e s u l t o f t h e PACS p r o g r a m , e m i s s i o n s f r o m r e s i d e n t i a l wood s p a c e h e a t i n g w e r e a d d e d a s an i m p o r t a n t new s o u r c e c a t e g o r y . This l a t t e r category i s proj e c t e d t o be t h e f a s t e s t growing e m i s s i o n source i n t h e near future.


ATMOSPHERIC AEROSOL

116

0.5


0.4 Residual Oil 0-3 Local

cmb

02 3

(ng/m ) ® Site 2

0.1

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0.1 0.2 0.3

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Model Predictions (ng/m ) 3

Figure 5.

Residual oil impacts—north wind regime (initial predictions)

/

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(ng/m ) 10 5 0 Figure 6. Road dust impacts—north wind regime (corrected inventory)

5

10 15 20 25 30 Model Prediction (ng/m ) 3


6.

CORE

E T

Air Particulate Control

A L .

Strategy

111


F i n a l GRID d i s p e r s i o n m o d e l r e s u l t s w e r e s i g n i f i c a n t l y i m p r o v e d and s y s t e m a t i c u n d e r p r e d i c t i o n s e l i m i n a t e d . Meas u r e d and m o d e l - p r e d i c t e d b a c k g r o u n d v a l u e s a g r e e d more c l o s e l y t h a n b e f o r e and t h e community c o u l d h a v e g r e a t e r c o n f i d e n c e i n the d i s p e r s i o n model's a b i l i t y t o e v a l u a t e t h e e f f e c t i v e n e s s of a l t e r n a t i v e c o n t r o l strategy. Figure 8 i l l u s t r a t e s the improvements i n model v e r i f i c a t i o n f o l l o w i n g e m i s s i o n i n v e n t o r y and m o d e l i n g a s s u m p t i o n improvements. Control Strategy Effectiveness U s i n g t h e v a l i d a t e d d i s p e r s i o n model as t h e k e y t o o l i n t h e s t r a t e g y d e v e l o p m e n t , e f f o r t s t u r n e d t o S t e p 5, C o n t r o l S t r a t e g y Development. T a b l e I p r e s e n t s p r e d i c t i o n s o f 1987 p a r t i c u l a t e a i r q u a l i t y b a s e d on f u t u r e y e a r e m i s s i o n d a t a b a s e s , and i n c o r p o r a t e s a l l o f t h e i d e n t i f i e d i n v e n t o r y c o r r e c t i o n s , and e m i s s i o n g r o w t h p r o j e c t i o n s . f

The 1977 t o 8 7 g r o w t h i n c r e m e n t was c a l c u l a t e d f r o m t h e m o d e l i n g and a d d e d t o t h e m e a s u r e d p a r t i c u l a t e v a l u e s t o a r r i v e a t a 1987 d e s i g n v a l u e upon w h i c h a n n u a l s t a n d a r d a t t a i n m e n t c o u l d be judged. Twenty-four hour attainment s t a t u s was s i m i l a r i l y d e t e r m i n e d , b u t was b a s e d on a w o r s t c a s e m e t e o r o l o g i c a l r e g i m e and e m i s s i o n s t y p i c a l o f t h o s e o c c u r r i n g on v i o l a t i o n d a y s . R e s u l t s r e q u i r e d a 2 t o 24 yg/m annual a v e r a g e r e d u c t i o n a t v a r i o u s s i t e s t o a c h i e v e t h e 60 yg/m s e c o n d a r y TSP s t a n d a r d and a 19 t o 104 yg/m i m p r o v e m e n t i n 2 4 - h o u r p a r t i c u l a t e a i r q u a l i t y t o a c h i e v e t h e 150 yg/m secondary standard. 3

3

3

3

M o d e l p r e d i c t i o n s o f numerous p o i n t and a r e a s o u r c e s t r a t e g i e s were c o m p l e t e d , a n e c o n o m i c a n a l y s i s o f t h e a l t e r n a t i v e s was d e v e l o p e d , and t h e r e s u l t s p l a c e d b e f o r e a p u b l i c a d v i s o r y committee. The c o s t - e f f e c t i v e n e s s a n d f i n e p a r t i c l e b e n e f i t s i d e n t i f i e d f o r each s t r a t e g y have p r o v i d e d t h e p u b l i c w i t h a sound b a s i s f o r t h e i r recommendations. B a s e d on a n e a r l y s t a f f a n a l y s i s , t h e most c o s t e f f e c t i v e a l t e r n a t i v e s included: *Reductions i n v e h i c l e t r a f f i c i n v i o l a t i o n a r e a s a t a n e t annual c o s t s a v i n g s o f about $100,000 p e r yg/m . Associated benefits i n c l u d e energy s a v i n g s , fewer r o a d and auto m a i n t e n a n c e c o s t s and i m p o r t a n t c a r b o n monox i d e and h y d r o c a r b o n e m i s s i o n b e n e f i t s . ^Cleanup of winter road sanding dust a t a c o s t o f $1700 t o $8300 p e r yg/m . ^Construction site trackout control i n p a r t i c u l a t e standard v i o l a t i o n areas e s t i m a t e d t o c o s t a b o u t $52,000 p e r yg/m . Less cost e f f e c t i v e controls include: 3

3

3

^ F u r t h e r c o n t r o l s on l o c a l p o i n t s o u r c e s a t $2.6 m i l l i o n p e r yg/m . * A d o p t i o n o f a 0.5% s u l f u r c o n t e n t l i m i t f o r r e s i d u a l o i l a t $4.2 m i l l i o n p e r yg/m . 3

3


ATMOSPHERIC AEROSOL

118

OPEN BURNING \ 4 6 1 T/Yr.

OIL AND GAS SPACE \

_ OTHER AREA SOURCES 913 T/Yr.

OTHER AREA S O U R C E S 913 T/Yr.


OIL A N D G A S S P A C E HEATING 493 T/Yr.

Before CMB Adjustment 14,563 Tons/Yr. Figure 7 .

Af terCMB Adjustment 38,827 Tons/Yr.

Portland AQMA

emission inventory—7977

100

100 /

1:1 S L O P E

80

80

£ g- E 60 O

total particulate

«H w

6 0

® ®

/ /

w

40

40

20 0

R=73 Slope = .79 Intercept =35

1 20

40

60

Model Predicted (ng/m ) 3

Figure 8.

20

R = .52 Slope = .65 Intercept = 46

80 100

20

40

60

80 100

Model Predicted (ng/m ) 3

Portland AQMA annual model predictions before (left,) and after (right) emission inventory improvements



^ P r e d i c t e d p a r t i c u l a t e concentrations on 2nd highest day.

120

104

254

223

3.

5.2

37.0

6.9

4.2

82

19

169

8.2

1.0

106

161

69

2.

219

Wood Burning

Auto Exhaust

Road Dust Impact

197

Reduction Needed To Meet Secondary Standard i n 1987

1.

Site

Design Values* 1977 1987

3

Table I Particulate Control Alternatives Model P r e d i c t e d Source Impacts f o r 1987 (yg/m , 24 Hour Worst Case Meteorology)


7.4

6.2

7.1

A l l Point Sources


120

ATMOSPHERIC

AEROSOL

A l t h o u g h the c o n t r o l of f u g a t i v e e m i s s i o n s appears t o be t h e most c o s t e f f e c t i v e a p p r o a c h t o p a r t i c u l a t e s t a n d a r d a t t a i n m e n t , few b e n e f i t s i n r e g i o n a l v i s i b i l i t y improvement and p u b l i c h e a l t h w o u l d be e x p e c t e d f r o m s u c h a s t r a t e g y . A b a l a n c e b e t w e e n c o n t r o l o f f u g a t i v e d u s t e m i s s i o n s and s o u r c e s o f f i n e p a r t i c u l a t e s i s p e r h a p s t h e most a p p r o p r i a t e approach to standard attainment. S t r a t e g y Development i n Other A i r s h e d s S o u r c e i m p a c t s t u d i e s u s i n g t h e C h e m i c a l Mass B a l a n c e d i s p e r s i o n modeling approach have a l s o been completed i n Eugene and M e d f o r d , 0 r e g o n ( 9 , 1 0 ) . As i n P o r t l a n d , t h e work h a s i d e n t i f i e d e m i s s i o n i n v e n t o r y and m o d e l i n g i m p r o v e m e n t s w h i c h , when c o r r e c t e d , h a v e g r e a t l y i m p r o v e d m o d e l i n g r e s u l t s . F i g u r e 9 shows d i s p e r s i o n m o d e l r e s u l t s f o r t h e M e d f o r d a i r s h e d b e f o r e and a f t e r e m i s s i o n i n v e n t o r y and m o d e l i m p r o v e ments. S e v e r a l o f t h e most s i g n i f i c a n t r e s u l t s o f t h i s work are: *Road d u s t e m i s s i o n i n v e n t o r y e r r o r s were c o r r e c t e d a f t e r comparing d i s p e r s i o n model and CMB r e s u l t s . Road d u s t e m i s s i o n s were i n c r e a s e d by 2300 t o n s i n M e d f o r d a s a r e s u l t of emission f a c t o r adjustments and changes i n the unpaved road dust i n v e n t o r y . I n E u g e n e , new m e a s u r e m e n t s o f t r a f f i c v o l ume and v e h i c l e s p e e d s on u n p a v e d r o a d s l e d t o a 2600 t o n p e r y e a r r e d u c t i o n i n r o a d dust emissions. ^ R e s i d e n t i a l wood b u r n i n g e m i s s i o n s , i d e n t i f i e d by a t e l e p h o n e s u r v e y o f homeo w n e r s , were v e r i f i e d by c o m p a r i n g d i s p e r s i o n m o d e l and CMB v e g e t a t i v e b u r n ing estimates. * P o i n t s o u r c e plume t r a p p i n g a s s u m p t i o n s used i n t h e Eugene a i r s h e d m o d e l i n g were v e r i f i e d by c o m p a r i n g a l t e r n a t i v e m o d e l i n g assumptions of s u l f a t e e m i s s i o n impacts to measured s u l f a t e l e v e l s . *Major changes i n the Medford model's t r e a t m e n t o f a r e a s o u r c e i m p a c t s were completed after early results consistently u n d e r p r e d i c t e d road dust impacts measured by CMB. As a r e s u l t , m o d e l performance improved d r a m a t i c a l l y . C o n t r o l S t r a t e g y T r a c k i n g U s i n g CMB M e t h o d s F o l l o w i n g c o m p l e t i o n o f t h e d a t a b a s e improvement p r o grams, a b e t t e r , y e t s t i l l i n c o m p l e t e , k n o w l e d g e o f t h e s o u r c e s of the p a r t i c u l a t e i s b e i n g used t o d i r e c t c o n t r o l p r o g r a m s a i m e d a t a c h i e v i n g a i r s t a n d a r d s w i t h minimum c o s t t o t h e community. Had t h e m o d e l i n g work n o t b e e n compared t o t h e CMB r e s u l t s , f u t u r e c o n t r o l s w o u l d l i k e l y h a v e b e e n d i r e c t e d toward t r a d i t i o n a l , i n d u s t r i a l s o u r c e s .



CORE

Air Particulate

E T A L .

125

T

Control

Strategy

125

•

100

1:1 100

Hi-Vol (ng/m ) 75 3

75

• ©

•

Model Prediction (|ig/m ) 3

Model Prediction (^g/m ) 3

Figure 9. Medford annual model predictions—1978 (arithmetic mean). Hi-vol vs. model predicted TSP mass before ( l e f t ) and after ( r i g h t j model improvements


ATMOSPHERIC

122

AEROSOL


W i t h o u t t h e b e n e f i t o f t h e d a t a b a s e improvement p r o g r a m s , $27 m i l l i o n d o l l a r s i n i n d u s t r i a l c o n t r o l s would l i k e l y have been t h e k e y e l e m e n t i n a new c o n t r o l s t r a t e g y y e t w o u l d h a v e o n l y p r o v i d e d o n e - t h i r d o f t h e r e d u c t i o n r e q u i r e d t o meet s t a n d a r d s . I n s t e a d , a more e f f e c t i v e m i x o f p o i n t and a r e a s o u r c e c o n t r o l s w i l l l i k e l y be a d o p t e d and, a t c o n s i d e r a b l y l e s s c o s t t o (and w i t h c o n s i d e r a b l y more e f f e c t i v e n e s s f o r ) t h e community. Once t h e c a p a b i l i t y i s d e v e l o p e d , CMB e s t i m a t e s o f s o u r c e i m p a c t s c a n be u s e d t o t r a c k t h e p r o g r e s s o f t h e s t r a t e g y on a s o u r c e c l a s s b a s i s u s i n g a c t u a l a i r samples, ( i n a d d i t i o n t o e m i s s i o n e s t i m a t e s ) t o measure the e f f e c t i v e n e s s o f the c o n t r o l s . Oregon's Source Apportionment P r o g r a m and t h e F u t u r e S o u r c e a p p o r t i o n m e n t p r o g r a m s u s i n g C h e m i c a l Mass B a l a n c e d i s p e r s i o n m o d e l i n g , o p t i c a l m i c r o s c o p y , and o t h e r m e t h o d s h a s become, and w i l l c o n t i n u e t o be, an i m p o r t a n t p a r t o f t h e O r e g o n s p a r t i c u l a t e a i r q u a l i t y management p r o g r a m . During t h e p a s t two y e a r s , t h e D e p a r t m e n t s l a b o r a t o r y d i v i s i o n h a s a c q u i r e d a l l t h e n e c e s s a r y a n a l y t i c a l and a i r m o n i t o r i n g c a p a b i l i t i e s n e e d e d t o o b t a i n C h e m i c a l Mass B a l a n c e i n p u t d a t a a n d i n t e r a c t i v e CMB s o f t w a r e i s a v a i l a b l e t o A i r Q u a l i t y Division staff. Information i s also being gathered i n several O r e g o n c o m m u n i t i e s t o d e f i n e s o u r c e c o n t r i b u t i o n s f r o m wood combustion, t o r e s o l v e impacts c u r r e n t l y l i s t e d as " u n i d e n t i fied and i m p r o v e s o u r c e c h a r a c t e r i z a t i o n d a t a . These programs a r e p r o v i d i n g i n f o r m a t i o n on c u r r e n t s o u r c e i m p a c t s , a s w e l l a s an i n d e p e n d e n t means o f t r a c k i n g t h e s u c c e s s o f c o n t r o l programs. 1

f

1 1

A h i s t o r i c a l data base of s i z e - r e s o l v e d p a r t i c u l a t e data s u i t a b l e f o r source apportionment s t u d i e s p r o v i d e s a wealth of d a t a u s e f u l t o r e g u l a t o r y a u t h o r i t i e s . As new p r o g r a m s b e g i n t o f o c u s on i n h a l a b l e and r e s p i r a b l e p a r t i c u l a t e s t a n d a r d s , t h i s d a t a w i l l become i n c r e a s i n g l y v a l u a b l e . Conclusions The d e v e l o p m e n t o f new s o u r c e a p p o r t i o n m e n t m e t h o d s h a v e , f o r the f i r s t time, l e d to the development of r e g i o n a l p a r t i culate control strategies. Source impacts a s s i g n e d u s i n g a c h e m i c a l mass b a l a n c e (CMB) m o d e l h a v e b e e n u s e d i n a s s o c i a t i o n w i t h a i r s h e d d i s p e r s i o n models to i d e n t i f y e m i s s i o n i n v e n t o r y d e f i c i e n c i e s and i m p r o v e m o d e l i n g assumptions. E x p e r i e n c e g a i n e d d u r i n g t h e p a s t f o u r y e a r s h a s shown t h a t d a t a b a s e improvement p r o g r a m s s u c h a s t h o s e i m p l e m e n t e d i n O r e g o n h a v e p r o v i d e d new p e r s p e c t i v e s i n t o t h e n a t u r e o f each a i r s h e d ' s e m i s s i o n s . Subsequent major changes i n each community's e m i s s i o n i n v e n t o r i e s have improved dispersion m o d e l i n g r e s u l t s and p r o v i d e d a l e v e l o f d i s p e r s i o n m o d e l v e r i f i c a t i o n impossible to a t t a i n using t r a d i t i o n a l h i - v o l measurements a l o n e . A l t h o u g h the c u r r e n t t e c h n o l o g y of r e c e p t o r models i s s t i l l i n an e a r l y s t a g e o f d e v e l o p m e n t , t h e r a p i d g r o w t h o f t h e s e t e c h n i q u e s i s c e r t a i n t o p r o v i d e an i m p o r t a n t new tool to r e g u l a t o r y a g e n c i e s w i t h i n the immediate f u t u r e .


6.

CORE

E T A L .

Air

Particulate Control

Strategy

123


Literature Cited 1.

U.S. Environmental Protection Agency "Guidelines on A i r Quality Models", EPA-450/2-78-027, April 1978.

2.

Cooper, J.A.; Watson, J . G . "Receptor Oriented Methods of A i r Particulate Source Apportionment" J. Air Pollution Control Association, 1978, 30 (10).

3.

Friedlander, S.K. "Chemical Element Balance and Identification of Air Pollution Sources" Env. S c i . & Technol., 1973, 7 (3).

4.

Watson, J . G . "Chemical Element Balance Receptor Model Methodology For Sources of Fine and Total Suspended Particulate Matter in Portland, Oregon." Oregon Graduate Center, February 1979.

5.

Cooper, J . A . ; Watson, J . G . "Portland Aerosol Characterization Study", Final Report to the State of Oregon Department of Environmental Quality, July 1979.

6.

Johnson, R . L . ; Huntzicker, J.J. "Analysis of Volatilizable and Elemental Carbon in Ambient Aerosols", Conference on Carbonaceous Particules in the Atmosphere, Berkeley, CA, 1978.

7.

Fabrick, A.J.; Sklarew, R.C. "Oregon/Washington Diffusion Modeling Study" Xonics, Inc., 1975.

8.

Roberts, J.; Watters, H . ; Austin, F.; Crooks, M. "Particulate Emissions For Paved Roads in Seattle and Tacoma Non-Attainment Areas", Puget Sound Air Pollution Control Agency, July 1979.

9.

Core, J.E.; Greene, W.T.; Terraglio, F.P. "Slash Burning Particulate Impact Analysis in Oregon's Williamette Valley" State of Oregon Department of Environmental Quality, June 1979.

10. Cooper, J . A . "Medford Aerosol Characterization Study Application of Chemical Mass Balance Methods to the Identification of Major Aerosol Sources in the Medford Airshed", Interim Report to the State of Oregon Department of Environmental Quality, November 1979. RECEIVED March 25,

1981.


Atmospheric Aerosol - ACS Publications - American Chemical Society

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