# Appendix L.9

New IMPROVE EquationTDEC-APC letter to EPA Region 4 requesting to use the new IMPROVE equation for BART

D eterminations for Alcoa, DuPont-Old Hickory, and Eastman Chemical...............

..... ................. ....... .. ......2

Justification for the use of the New Improve Equation.........................................................................

. .. ... . . 6

Instruction for the use of the New Improve Equation Algorithm

in CALPOST processing for BART Determinations.......................................................................

. ......... . . 10

Old and New Relative Humidity Factors f(RH) Values..............................................................................26

Salt Concentration values for Class I Areas of VISTAS and nearby states...............................................28DIVISION OF AIR POLLUTION CONTROL

9TH FLOOR, L & C ANNEX

401 CHURCH STREET

NASHVILLE, TN 37243-1531

September 13, 2007

Mr. J. I. Palmer, Regional Administrator

US Environmental Protection Agency

Atlanta Federal Center

61 Forsyth Street, SW

Atlanta, GA 30303-8909

Re: Request for Approval to use New IMPROVE Equation for BART Modeling

Dear Mr. Palmer,

The Tennessee Division of Air Pollution Contro l has been working with the Visibility

Improvement States and Tribal Association of the Southeast (VISTAS) and EPA Region 4 staff

to implement the Best Available Retrofit T echnology (BART) requirements of the Regional

Haze Rule. As part of this process, the need for a methodology to post-process

CALPUFF/CALPOST modeling data to implemen t the new IMPROVE equation was identified.

VISTAS asked Dr. Ivar Tombach to develop su ch a methodology. The resulting spreadsheet and

supporting information were submitted by the stat e of North Carolina to EPA and the Federal

Land Managers (FLM) for review. Upon review , EPA Region 4 staff commented that they

consider this post-processing methodology a non-regulatory modeling application requiring

compliance with Section 3.2 of Appendix W, Part 51: Guidance on Air Quality Models and that

each individual state must request approval for use of this alternative method. The following

information is provided and formal approval fo r use of this alternative method by Tennessee’s

affected sources for BART exemption and demonstration modeling is requested.

Rationale for use of the new IMPROVE Equation

The new IMPROVE equation, which is a much better representation of the effects of

particulate matter on light extinction than the old e quation, takes into account the latest scientific

understanding of several parameters.

1. The new algorithm overcomes biases of th e old algorithm on the haziest days and the

clearest days as demonstrated by compar ing the measured light extinction from

nephelometers at Class I areas to light extinction calculated using each of the equations.Mr. J. I. Palmer

September 13, 2007

Page 2

2. The new algorithm recognizes spatial and tempor al variation in light extinction as size

distribution of the aerosol changes by increasing extinction efficiency as sulfate, nitrate,

and organics concentrations increase.

3. The new algorithm reflects research finding th at the mass concentration of particulate

organic matter in rural areas is greater than represented by the old equation.

4. The new algorithm includes a NO 2 term to represent times when light absorption by NO 2 is a meaningful contributor to light extinction.

5. The new algorithm incorporates site-speci fic Rayleigh scattering values to better

represent sites close to sea level or with very hot or cold climates.

6. The new algorithm incorporates a term to refl ect the contribution of fine sea salt and its

hygroscopic growth with increasing relative humidity recognizing research findings

showing that fine sea salt can be an important contributor to light extinction in coastal

areas.

With this combination of revisions to the IMPROVE equation, the resulting apportionment of

extinction to various components is more accurate on the haziest and clearest days. This is

important for development of emission control st rategies since the benefits of control of

concentrations of each species will be represen ted more correctly with the new algorithm.

Further discussion of these reasons is included in Enclosure 1.

The spreadsheet developed by Dr. Tombach to implement the entire new IMPROVE

equation for use with CALPUFF contains a modi fication of CALPOST that calculates the light

extinction from the CALPUFF output. In thei r review of the spreadsheet and supporting

documentation, EPA Region 4 staff commented th at the VISTAS methodology contained in the

spreadsheet developed by Dr. Tombach appropria tely implements the features of the new

IMPROVE equation, with the exception of the n itrogen dioxide term. EPA Region 4 further

stated that with the addition of th eir recommendation for addressing the NO 2 term, the VISTAS

methodology to incorporate the new IMPROVE e quation is acceptable on a case-by-case basis

upon consultation with the EPA Regional Office. Two Tennessee sources, Eastman Chemical

and Alcoa, have requested to use the new IMPR OVE equation for their BART determinations.

One additional source, DuPont – Old Hickory, found that the new IMPROVE equation makes a

difference for their BART exemption modeling, and have also requested its use.

Equation Performance Versus Measured Values

A comparison of the old versus new IMPROVE equation and nephelometer data at several

Class I areas is included in Enclosure 1. The old IMPROVE equation tends to show a low bias

on high extinction days. The new equation shows a better match on high extinction days with a

slightly high bias. The correlation coefficients are often slightly lower for the new equation than

the old equation because there is slightly more scatter at the low end of the equation.Mr. J. I. Palmer

September 13, 2007

Page 3

Modified Post-Processing Methodology

Since the initial EPA review of the methodology, Dr. Tombach has modified the spreadsheet

to address the NO 2 contribution. A copy of the modified spreadsheet and instructions are

provided as Enclosure 2 for your review.

We look forward to your response to this re quest for approval of use of the VISTAS

methodology incorporating the new IMPROVE e quation by Eastman Chemical, Alcoa, and

DuPont – Old Hickory for BART purposes. If you have any questions regarding this

correspondence, please contact Julie Aslinger at (615) 532-0587. Thank you in advance for your

assistance.

Sincerely,

Barry R. Stephens, P.E.

Director

Tennessee Division of Air Pollution Control

BRS/JA

cc: Kay Prince, EPA Region 4

Brenda Johnson, EPA Region 4Enclosure 1



### Why Use the New IMPROVE Algorithm?

10/26/06

The new IMPROVE algorithm, which has been approved by the IMPROVE Steering

Committee, is a much better representation of the effects of particulate matter on light

extinction than the old IMPROVE algorithm. Excel lent justification of this conclusion is

provided in the November 2005 report of the IMPROVE Steering Committee, “Revised

IMPROVE Algorithm for Estimating Light Exti nction from Particle Speciation Data.” 1

The new algorithm incorporates changes that represent much of what has been learned

about the relationship between particulate matter component concentrations and light

extinction in the more than a decade sinc e the old algorithm wa s developed. The main

reasons that justify using the new algorith m instead of the old one are the following:

1. The new algorithm overcomes the biases of the old algorithm on the haziest days

(when the old algorithm underestimates light extinction) and on the clearest days

(when the old algorithm overestimates extin ction). This improvement can be seen

by comparing measured light scattering fr om nephelometers with light scattering

calculated using either the original IMPROVE equation or the new IMPROVE

equation. Figures 1- 3 at the end of this summary illustrate the performance of the

new and old equations compared to nephelometer data for Great Smoky

Mountains and Shenandoah National Parks and Cape Romain Wildlife Refuge.

Additional examples are available on the Air Resource Specialists ftp site 2 and in

the IMPROVE report referenced above.

2. The new algorithm recognizes that light ex tinction efficiencies vary from location

to location and time to time as the size dist ribution of the aerosol changes, and it

reflects this variation by in creasing the extinction efficiency as the concentrations

of sulfates, nitrates, and organics increas e. It also recognizes that the humidityrelated growth rates of particles differ depending on their sizes. As a result, the

new algorithm generally does a better job of representing li ght extinction at

individual sites than does the old algorith m, as indicated by the reduced fractional

biases in each RPO region (see Tables 3 and 5 compared to Tables 2 and 4 as

copied at the end of this summary from the IMPROVE report.)

3. The new algorithm recognizes research findings that show that fine sea salt can be

an important contributor to light extinc tion in coastal areas, and thus includes a

new term that reflects its contribution and its hygroscopic growth with increasing

relative humidity. The old algorithm ignor es sea salt, probably because it was

originally developed mainly for inland Cl ass I areas in the inter-mountain West

(although incorporating sea salt into the calculation was already considered in a

University of California at Davis memo in 1995).

1 http://vista.cira.colostate.edu/improve /Publications/GrayLit /gray_literature.htm

. 2 ftp://ftp.air-resource.com/VISTAS/4c_Neph_Compare/4. The new algorithm acknowledges that substantial recent research has shown that

the mass concentration of particulate or ganic matter (often denoted by OMC in

IMPROVE publications) in rural areas is a greater multiple of the measured OC

concentration than the 1.4 value used in the old algorithm. The new algorithm

updates the factor to a more-appropriate1.8.

5. The new algorithm recognizes that there may be times (near urban areas or in

some source emission plumes) when light absorption by NO 2 gas is a meaningful

contributor to light extinction, and t hus includes a new term based on the NO 2

concentration.

6. The new algorithm recognizes that the a ssumption of constant Rayleigh scattering

of 10 Mm -1 (representative of an elevation of about 5000 feet) may have been

adequate when only inter-mountain West s ites were considered, but is a distortion

for sites close to sea level or with very hot or cold climates. It thus allows for sitespecific values of the Rayleigh scattering.

At any given location, the net result of all these changes is typically small on average

because some changes result in increases in extinction and some in decreases, but the

apportionment of that extinction to the various components is more accurate with the new

algorithm, especially on the haziest and cleares t days. This is particularly important for

the development of emission management strate gies, because the benefits of control of

concentrations of each species will be represen ted more correctly with the new algorithm.

____________________________________

Figure 1. Aerosol Scatteri ng vs Nephelometer Scatteri ng Comparing New and Old

IMPROVE Algorithm and Daily f(RH), Great Smoky Mountains National Park, 1995-

2004.

All Days

y = 1.00x + 8.73

R 2 = 0.88

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) All Days

y = 0.75x + 17.21

R 2 = 0.89

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp (Mm -1 )24-hr Aerosol bsp(Mm-1) 

### New IMPROVE Old IMPROVE All Days

y = 1.00x + 8.73

R 2 = 0.88

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) All Days

y = 0.75x + 17.21

R 2 = 0.89

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp (Mm -1 )24-hr Aerosol bsp(Mm-1) 

### New IMPROVE Old IMPROVEFigure 2. Aerosol Scatteri ng vs Nephelometer Scatteri ng Comparing New and Old

IMPROVE Algorithm and Daily f(RH), Shenandoah National Park, 1996-2004.

igure 3. Aerosol Scatteri ng vs Nephelometer Scatteri ng Comparing New and Old All Days

y = 1.04x + 6.27

R 2 = 0.79

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) All Days

y = 0.80x + 13.76

R 2 = 0.81

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) 

### New IMPROVE Old IMPROVE All Days

y = 1.04x + 6.27

R 2 = 0.79

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) All Days

y = 0.80x + 13.76

R 2 = 0.81

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) 

### New IMPROVE Old IMPROVE

F

IMPROVE Algorithm and Daily f(RH), Ca pe Romain Wildlife Refuge, 2004.

All Days

y = 1.18x + 0.77

R 2 = 0.86

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) All Days

y = 1.00x + 5.80

R 2 = 0.91

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp (Mm -1 )24-hr Aerosol bsp(Mm-1) New IMPROVE Old IMPROVE All Days

y = 1.18x + 0.77

R 2 = 0.86

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp

(Mm -1 )24-hr Aerosol bsp(Mm-1) All Days

y = 1.00x + 5.80

R 2 = 0.91

0 50 100 150 200 250 300

0 50 100 150 200 250 300

24-hr Nephelometer b

sp (Mm -1 )24-hr Aerosol bsp(Mm-1) Old IMPROVE New IMPROVET he Tables below were copied from th e report “Revised IMPROVE Algorithm for

stimating Light Extinction from Particle Speciation Data”.

ent IMPROVE algorithm

ith quintiles based on measured light scattering (criterion 1). Bold font highlights

Average E

Table 2. Averaged fractional bias by RPO for the curr

w

the bias values that are lower than corresponding values in Table 3.

RPO Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5

CEN 0.67 0.18 0.10 0.02 -0.11 0.17

MANE 27 9 0 01 0.93 0. 0.1 0.1 0. 0.28

VISTA S 0.59 0.21 0.11 0.02 -0.13 0.16

WRAP 1.07 0.37 0.18 0.07 -0.08 0.32

Table 3. Averaged fractional

ith quintiles based on measured light scattering (criterion 1). Bold font highlights

Average bias by RPO for the current new proposed algorithm

w

the bias values that are lower than corresponding values in Table 2.

RPO Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5

CEN 0.51 0.08 0.02 -0.03 -0.08 0.10

MANE 14 6 1 2 0.74 0. 0.0 0.0 -0.0 0.17

VISTA S 0.50 0.16 0.11 0.06 -0.01 0.16

WRAP 0.84 0.25 0.08 0.01 -0.10 0.21

able 4. Averaged fractional bias by RPO for the current IMPROVE algorithm

ith quintiles based on estimated light scatt ering (criterion 2). Bold font highlights

Average T

w

the bias values that are lower than corresponding values in Table 5.

RPO Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5

CEN 0.42 0.19 0.18 0.09 -0.01 0.17

MANE 27 0 3 15 0.35 0. 0.3 0.3 0. 0.28

VISTA S 0.38 0.19 0.14 0.08 0.01 0.16

WRAP 0.58 0.37 0.26 0.25 0.15 0.32

Table 5. Averaged fractional bias by RP O for the current new proposed algorithm

ith quintiles based on estimated light scatt ering (criterion 2). Bold font highlights

Average w

the bias values that are lower than corresponding values in Table 4.

RPO Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5

CEN 0.23 0.11 0.08 0.06 0.02 0.10

MANE 14 5 9 21 0.15 0. 0.1 0.1 0. 0.17

VISTA S 0.25 0.14 0.08 0.13 0.21 0.16

WRAP 0.37 0.19 0.19 0.16 0.17 0.21

### I n s t r u c t i o n s :

A P os t p r oc e s s or f or R e c al c u l at i n g C A L P O S T V i s i b i l i t y O u t p u t s

w i t h t h e N e w I M P R O V E A l gor i t h m

V e r s i on 2

1 4 O c t ob e r 2006

I n t r od u c t i on

C A L P O S T c a n be us e d t o p r oc e s s e s out put s f r om C A L P U F F m ode l i ng of a s our c e ’ s e m i s s i ons

t o c a l c ul a t e t he 24

- h r a ve r a ge vi s i bi l i t y i m pa i r m e nt s c a us e d by pr i m a r y a nd s e c onda r y pa r t i c ul a t e

m a t t e r a t t r i but a bl e t o e m i s s i ons f r om t he m ode l e d s our c e

. T hos e i nc r e m e nt s a r e pr e s e nt e d i n t w o

t a

bl e s

, bot h l a be l e d “ R a nke d D a i l y V i s i bi l i t y C ha nge ”

, i n t he C A L P O S T o ut put (

. L S T ) f i l e

. T he

t a

bl e of i nt e r e s t t o us ha s t he s ubt i t l e “ M ode l e d E x t i nc t i on by S pe c i e s ” a nd l i s t s t he da t e s a nd

l oc a t i ons of s uc h i nc r e m e nt a l i m pa c t s i n l i ght e xt i n c t i on ( b

e x t ) i n r a nke d or de r

, s t a r t i ng w i t h t he

one t ha t r e pr e s e nt s t he l a r ge s t pe r c e nt a ge c ha nge i n l i ght e xt i nc t i on

. 1

I n a ddi t i on

, w i t h a di f f

e r e nt s e t up o f t he c ont r ol f i l e C A L P O S T

. I N P

, t he C A L P O S T

pos t pr oc e s s or c a n be us e d t o c a l c ul a t e 24

- hr a ve r a ge s of N O

x c onc e nt r a t i ons

. A s de s c r i be d

be l ow

, t he out put s f r om t ha t a ddi t i ona l C A L P O S T r un c a n be us e d t o a s s e s s t he vi s i bi l i t y i m pa c t

of t he N O 2 ga s i n t he s our c e pl um e

.

V i s i bi l i t y e f f

e c t s due t o pa r t i c ul a t e m a t t e r a r e c a l c ul a t e d i n C A L P O S T f r om C A L P U F F

- m ode l e d

pa r t i c ul a t e m a t t e r c om pone nt c onc e nt r a t i ons us i ng e f f

e c t i ve l y t he “ t r a di t i ona l ” I M P R O V E

a l gor i t hm

. C A L P O S T a l l ow s f o r c hoi c e of t he hu m i di t y s c a t t e r i ng e nha nc e m e nt f unc t i on ( f ( R H ) )

t o be us e d w i t h t he I M P R O V E a l go r i t hm ; f or m od e l i ng i n c onne c t i on w i t h t he U S E P A ’ s

R e gi ona l H a z e R e gul a t i ons ( R H R )

, t he a ppr opr i a t e f or m of f ( R H ) i s t he one de s c r i be d a nd

t a

bul a t e d i n t he E P A ’ s 2003 gui da nc e f o r t r a c ki ng pr ogr e s s unde r t he R H R

. V i s i bi l i t y e f f

e c t s due

t o N O 2 a r e not c ons i de r e d i n t he C A L P O S T vi s i bi l i t y c a l c ul a t i on

.

R e c e nt l y, t he I M P R O V E S t e e r i ng C om m i t t e e de ve l ope d a ne w a l gor i t h m f o r e s t i m a t i ng l i ght

e xt i nc t i on f r om pa r t i c ul a t e m a t t e r c om pone nt c onc e nt r a t i ons

. T hi s a l go r i t hm ( t he “ ne w

I M P R O V E a l gor i t hm ” ) pr ovi de s a be t t e r c or r e s ponde nc e be t w e e n t he m e a s ur e d vi s i bi l i t y a nd

1 T h e o t h er t ab l e i n t h e C A L P O S T v i s i b i l i t y o u t p u t fi l e, w i t h t h e s u b t i t l e “ % o f Mo d el ed E x t i n ct i o n b y

Sp eci es ”

, p ro v i d es eq u i v al en t res u l t s i n t er ms o f ch an g es i n t h e h a ze i n d ex

, i n d eci v i e w s

. T h e t w o t ab l es

rep res en t t h e s a me res u l t s

, w i t h i d en t i cal r an k i n g o f ev e n t s

, w h i l e j u s t u s i n g d i fferen t (b u t m at h em at i cal l y

rel at ed ) met ri cs

.2 t ha t c a l c ul a t e d f r om pa r t i c ul a t e m a t t e r c om pone nt c onc e nt r a t i ons

. T he ne w a l go r i t hm di f f

e r s i n

s e ve r a l s ubs t a nt i ve w a ys f r om t he t r a di t i ona l one :

• T he e xt i nc t i on e f f i c i e nc i e s of s ul f a t e s

, ni t r a t e s

, a nd or ga ni c s ha ve be e n c ha nge d a nd a r e

now f unc t i ons of t he i r c onc e nt r a t i ons

. T he e xt i nc t i on e f f i c i e nc i e s of s ul f a t e a nd ni t r a t e

a r e no l onge r i de nt i c a l

, a l t houg h t he ne w hygr os c o pi c s c a t t e r i ng e nha nc e m e nt f a c t or s

a

ppl i e d t o t he m a r e t he s a m e

.

• T he c onc e nt r a t i on o f pa r t i c ul a t e or ga ni c m a t t e r ( P O M ; va r i ous l y a l s o l a be l e d O C M or

O M C

, a nd s om e t i m e s j us t c a l l e d “ or ga ni c s ” ) i s no w t a ke n t o be 1. 8 t i m e s t ha t o f t he

m e a s ur e d or ga ni c c a r bon ( O C ) c onc e nt r a t i on. ( C onf us i ngl y, C A L P O S T l a be l s t he

or ga ni c s c onc e nt r a t i on a s O C

. )

• T he c ont r i but i on of f i ne s e a s a l t t o l i ght e xt i nc t i on ha s be e n a dde d, a nd i s a c c om pa ni e d

by i t s ow n hyg r os c opi c s c a t t e r i ng e nha nc e m e nt f a c t or

, f

s s ( R H )

.

• T he l i ght s c a t t e r i ng by a i r i t s e l f ( R a yl e i gh s c a t t e r i n g) now va r i e s w i t h s i t e e l e va t i on a nd

m e a n t e m pe r a t ur e

. I t i s t o be r ounde d o f f t o t he ne a r e s t one M m - 1 w he n us e d w i t h t he

ne w a l gor i t hm

.

• T he l i ght a bs or pt i on by N O 2 ga s ha s be e n a dde d.

T he ne w I M P R O V E a l gor i t hm i s r e pr e s e nt e d by t h e f ol l ow i ng f or m ul a : 2

b

e

x t = 2. 2 • f

S (

R H ) • [ s m al l s ul f

at e ] + 4. 8• f

L (

R H ) • [ l ar

ge s ul f

at e ]

+ 2. 4• f

S (

R H ) • [ s m al l ni t r at e ] + 5. 1 • f

L (

R H ) • [ l ar ge ni t r at e ]

+ 2. 8• [ s m al l or gani c s ] + 6. 1• [ l ar ge or gani c s ]

+ 10• [ e l e m e nt al c ar bon ]

+ 1• [ f

i ne s oi l ] ( E q. 1)

+ 1. 7• f

S

S (

R H ) • [ s e a s al t ]

+ 0. 6• [ c oar s e m at t e r ]

+ R ay l e i gh s c at t e r i ng ( s i t e s pe c i f

i c

)

+ 0. 33• [ N

O 2 ( ppb )

]

T he c onc e nt r a t i ons of “ l a r ge ” a nd “ s m a l l ” s ul f a t e pa r t i c l e s a r e c a l c ul a t e d a s f ol l ow s :

[

l ar ge s ul f

at e ]

= {[ t ot al s ul f

at e ]

/ 20}• [ t ot al s ul f

at e ] i f [ t ot al s ul f

at e ] < 20 μ g 3

[

l ar ge s ul f

at e ]

= [ t ot al s ul f

at e ] i f [ t ot al s ul f

at e ] ≥ 20 μ g/ m 3 ( E qs

. 2 )

[

s m al l s ul f

at e ]

= [ t ot al s ul f

at e ]

– [ l ar ge s ul f

at e ]

.

I de nt i c a l f or m u l a s

, w i t h c ha nge s i n c om pone nt na m e s

, a r e us e d f o r ni t r a t e a nd or ga ni c s

. I n

e f

f

e c t

, t he s e f o r m ul a s c onc l ude t ha t l ow c onc e nt r a t i ons of t he s e c om pone nt s a r e m a i nl y i n t he

f

or m o f “ s m a l l ” pa r t i c l e s w i t h t he i r ow n e xt i nc t i on e f f i c i e nc y a nd f S ( R H )

, w hi l e hi gh

2 Sq u ar e b r ack et s d en o t e co n c en t rat i o n s

.3 c onc e nt r a t i ons ( a ppr oa c hi ng 20 μ g / m 3 ) a r e m a i n l y i n t he f o r m o f “ l a r ge ” p a r t i c l e s w i t h a

di f f

e r e nt e xt i nc t i on e f f i c i e nc y a nd f L ( R H )

. T he s c a l i ng f a c t or [ t ot a l s ul f a t e ] / 20 s e t s t he f r a c t i on o f

t ot a l s ul f a t e t ha t i s s m a l l

.

T he s e a s a l t c onc e nt r a t i on i s t a ke n t o be 1

. 8• [ C l

- ] o r

, i f c hl o r i de i on m e a s ur e m e nt s a r e not

a va i l a bl e

, t he c hl or i ne c onc e nt r a t i on c a n be us e d i n i t s pl a c e

. S i t e s pe c i f i c R a yl e i gh s c a t t e r i ng

va l ue s ha ve be e n c a l c ul a t e d f or a l l I M P R O V E s i t e s

. 3 N i t r oge n di ox i de c onc e nt r a t i ons a r e not

m e a s ur e d a t I M P R O V E s i t e s

, but t he a m bi e nt N O 2 c onc e nt r a t i ons unde r na t ur a l c ondi t i ons c a n

be e xpe c t e d t o be ne gl i gi bl y s m a l l

. T he hi ghe r N O 2 c onc e nt r a t i on i n a s our c e pl um e m a y be

gr e a t e nough t o c a us e a c ha nge i n vi s i bi l i t y

, how e v e r

.

I n or de r t o e na bl e C A L P O S T t o c a l c ul a t e C A L P U F F

- m ode l e d s our c e i m pa c t s o n vi s i bi l i t y us i ng

t he ne w I M P R O V E a l gor i t hm

, i t w oul d ha ve t o be e xt e ns i ve l y r e pr ogr a m m e d. A s a n a l t e r na t i ve

,

s uc h a c a l c ul a t i on c oul d be done “ o f f l i ne ” by a ddi ng a not he r l a ye r of pos t pr oc e s s i ng a f t e r

C A L P O S T

. T o t hi s e nd, I ha ve de ve l ope d a p r oc e s s or

, i n t he f o r m o f a n E xc e l w or kbook

, t ha t

t a ke s t he C A L P O S T “ R a nke d D a i l y V i s i bi l i t y C ha nge : M ode l e d E xt i nc t i on by S pe c i e s ” out put

t a

bl e

, r e f e r e nc e d a ga i ns t de f a

ul t a nnua l a ve r a ge na t ur a l c ondi t i ons c onc e nt r a t i ons

, a nd c r e a t e s a n

e qui va l e nt t a bl e of r e s u l t s ba s e d on t he ne w a l go r i t hm

. I t c a n a l s o i nc or po r a t e t he v i s i bi l i t y

i m pa c t due t o l i ght a bs or pt i on by N O 2 i n t he pl um e

.

T he f ol l ow i ng de s c r i be s t he s c i e nc e be hi nd t he pr o c e s s or ( w hi c h w e ’ l l c a l l t he C A L P O S T

I M P R O V E P r oc e s s or ) a nd p r ovi de s i ns t r uc t i ons f o r us i ng i t

.

C on c e p t s

I n a ddi t i on t o t he m e c ha ni c a l c ha nge s i m pos e d by a l l t he ne w t e r m s i n t he ne w I M P R O V E

f

or m ul a

, a ppl yi ng t he ne w a l gor i t h m a l s o r e qui r e s s om e c onc e pt ua l c ha nge s

. T he bi gge s t of

t he s e i s t ha t t he e xt i nc t i on e f f i c i e nc i e s of s ul f a t e s

, ni t r a t e s

, a nd o r ga ni c s now de pe nd on t he

c onc e nt r a t i ons of t hos e s pe c i e s

. T he p r a c t i c a l i m pl i c a t i on of t h i s i s t ha t e xt i nc t i on i s no l onge r

l i ne a r l y a ddi t i ve

. T o c a l c ul a t e t ot a l e xt i nc t i on

, y ou c a nnot t a ke a ba c kgr ound l e ve l of e xt i nc t i on

a nd a dd t o i t C A L P O S T ’ s c a l c ul a t i on o f e xt i nc t i o n c a us e d by t he pa r t i c ul a t e m a t t e r c om i ng f r om

a s our c e

, be c a us e w he n t he t w o a e r os ol s m i x i n t he a t m os phe r e t he i r c om b i ne d m a s s

c onc e nt r a t i on r e s ul t s i n i nc r e a s e s i n t he e xt i nc t i on e f f i c i e nc i e s of bot h t he ba c kgr ound a nd t he

s our c e c ont r i but i on. T hi s m e a n s t ha t c om bi ni ng ba c kgr ound pa r t i c ul a t e m a t t e r w i t h t he

pa r t i c ul a t e m a t t e r f r om a s our c e gi ve s a n e xt i nc t i o n r e s ul t t ha t i s gr e a t e r t ha n t he s um o f t he t w o

s e pa r a t e e xt i nc t i ons

.

W i t h t he nonl i ne a r be ha vi or r e s ul t i ng f r om a ppl yi n g t he ne w I M P R O V E a l gor i t hm

, t he

e xt i nc t i on i m pa c t of t he s our c e ( i

. e

. , t he i nc r e a s e i n e xt i nc t i on r e s ul t i ng f r om i nt r oduc i ng s our c e

e m i s s i ons i nt o t he a t m os phe r e ) i s t he s um of t hr e e pa r t s :

1. T he s our c e i m pa c t c a l c ul a t e d by t he ne w I M P R O V E a l gor i t h m us i ng t he C A L P O S T

out put s f or a pl um e i n i s ol a t i on;

3 R evi s ed I M

P

R O V E A l g o r i t h m f o r es t i m a t i n g Li g h t E xt i n ct i o n f r o m P a r t i cl e S p e ci a t i o n D a t a

. Rep o rt t o

IMP R O V E St e eri n g Co m mi t t ee, N o v emb er 2 0 0 5

.4 2. A n i nc r e a s e i n t ha t s our c e i m pa c t be c a us e t he e xt i nc t i on e f f i c i e nc y i nc r e a s e s w he n t he

s our c e ’ s a e r os ol c om bi ne s w i t h t he ba c kgr ound a e r os ol ; a nd c or r e s pondi ngl y

,

3. A n i nc r e a s e i n t he e xt i nc t i on of t he ba c kgr ound a e r os ol be c a us e of t ha t s a m e m i xi ng

.

T he t ot a l ne w e xt i nc t i on i s t he s um of t he a bove t h r e e c om pone nt s pl us t he or i g i na l ba c kgr ound

e xt i nc t i on. T he or i gi na l ba c kgr ound e xt i nc t i on i s j us t t ha t c a l c ul a t e d by t he ne w I M P R O V E

a l gor i t hm f r om ba c kgr ound c onc e nt r a t i ons of t he v a r i ous c om pone nt s

, w i t hout a ny c ons i de r a t i on

of t he e f f

e c t s of t he pl um e

. F or t hi s a ppl i c a t i on

, t h e ba c kgr ound i s t a ke n t o be t ha t de s c r i be d by

E P A ’ s de f a

ul t na t ur a l c ondi t i ons

. T he di f f

e r e nc e b e t w e e n t he t ot a l e xt i nc t i on a nd t he ba c kgr ound

i s t he i m pa c t of t he s our c e

.

M or e de t a i l s a bout t he c a l c ul a t i on a r e gi ve n i n t he a ppe ndi x.

D e s c r i p t i on of P r oc e s s or

T he C A L P O S T

- I M P R O V E P r oc e s s or i s a M i c r os of t E xc e l w or kbook t ha t c ons i s t s of f ou r

w or ks he e t s

. I n V e r s i on 2 t he w or ks he e t s a r e t he f o l l ow i ng.

1. I nput & O ut put

– T he out put t a bl e f r om C A L P O S T i s i m po r t e d t o he r e a nd us e r e nt r i e s

a r e m a de f or t he R a yl e i gh s c a t t e r i ng c oe f f i c i e nt a n d, i f de s i r e d, f or a s e a s a l t

c onc e nt r a t i on a t t he C l a s s I a r e a of i nt e r e s t

. T he N O

x c onc e nt r a t i on on e a c h da y

a t t r i but a bl e t o t he e m i s s i ons f r om t he s our c e c a n a l s o be e nt e r e d t oge t he r w i t h a n

a s s um pt i on of w ha t f r a c t i on of t he N O

x i s i n t he f o r m of N O 2

. A r e vi s e d t a bl e

, w i t h

e xt i nc t i on ba s e d on t he ne w I M P R O V E a l gor i t h m i s t he n pr e s e nt e d on t he s a m e pa ge

. T hi s i s t he onl y pa ge on w hi c h us e r i nput t a ke s pl a c e

, a nd t he r e s ul t s of t he c a l c ul a t i ons

a

ppe a r on t hi s pa ge

.

2. C a l c ul a t i ons

- - T he c a l c ul a t i ons t he m s e l ve s a r e a l l done on t h i s w or ks he e t

. T he r e i s no

us e r i nput t o t hi s pa ge

. T he va r i a bl e s a r e e xpl a i ne d o n t he w o r ks he e t i t s e l f

, s o t he us e r

c a n f i nd i nt e r m e di a t e va l ue s i f s o i nc l i ne d.

3. F ( R H )

– T hi s w or ks he e t t a bul a t e s t he t r a di t i ona l I M P R O V E f ( R H ) a ga i ns t R H

, a nd t he n

a l s o l i s t s va l ue s f or t he t h r e e ne w hum i di t y gr ow t h f unc t i ons

, f S ( R H )

, f L ( R H )

, a nd

f

S S ( R H )

. I t s e r ve s a s a l ookup t a bl e f or t he “ C a l c ul a t i ons ” w or ks he e t

.

4. R a yl e i gh & S e a S a l t

– T hi s pa ge t a bul a t e s t he I M P R O V E

- r e c om m e nde d R a yl e i gh

s c a t t e r i ng c oe f f i c i e nt s f or a l l V I S T A S C l a s s I a r e a s a nd f or C l a s s I a r e a s i n a dj a c e nt

s t a t e s

. I t a l s o l i s t s t he a ve r a ge s e a s a l t c onc e nt r a t i o ns f or t he s a m e l oc a t i ons

, a s t a bul a t e d

on t he V I E W S w e b s i t e

, ba s e d on c hl or i de or c hl or i ne m e a s ur e m e nt s by I M P R O V E

m oni t or s be t w e e n 2000 a nd 2004. T hi s s he e t j us t p r ovi de s i nf or m a t i on f or t he us e r ; i t i s

not l i nke d t o t he r e s t of t he w or kbook

. T he us e r c a n obt a i n R a yl e i gh a nd s e a s a l t num be r s

f

or t he C l a s s I a r e a of i nt e r e s t f r om t hi s t a bl e a nd t he n m a nua l l y e nt e r t he m i n t he

de s i gna t e d s pa c e s i n w or ks he e t 1.5 I n s t r u c t i on s f or U s i n g t h e C A L P O S T

- I M P R O V E P r oc e s s or

T he s e i ns t r uc t i ons a pp l y t o V e r s i on 2 of t he p r oc e s s or

. V e r s i on 2 i nc l ude s t he a bi l i t y t o c a l c ul a t e

t he l i ght e xt i nc t i on e f f

e c t s of N O 2 r e s ul t i ng f r om t he s our c e ’ s e m i s s i ons

.

S t e p 1. B e gi n by ope ni ng t he out put (

. L S T ) f i l e f r o m a C A L P O S T vi s i bi l i t y c a l c ul a t i on r un i n a

t e xt e di t or o r w o r d pr oc e s s i ng pr ogr a m

. 4 I n t he s e c ond ha l f o f t he f i l e

, l oc a t e t he t a bl e “ R a nke d

D a i l y V i s i bi l i t y C ha nge ” w i t h t he s ubhe a di ng “ M ode l e d E xt i nc t i on by S pe c i e s ”

. 5

S t e p 2. C opy t hi s t a bl e a nd pa s t e i t ont o a ne w pa g e

. S a ve i t a s a t e xt (

. t xt ) f i l e

, not a s a f or m a t t e d

( e

. g.

, M S W o r d

. doc or

. r t f ) f i l e

. T he f i na l t a bl e s h oul d c ont a i n onl y t he c ol um n he a di ngs a nd t he

da t a

. D e l e t e a l l ot he r c a pt i ons

, a ny a ddi t i ona l da t a s um m a r i e s a t t he e nd, a nd bl a nk l i ne s be f or e

or a f t e r t he t a bl e

. T he pr oc e s s or c a n ha ndl e a m a xi m um of 22 l i ne s of da t a ( i

. e

. , t he hi ghe s t r a nk

i n t he l a s t

, unl a be l e d, c ol um n s houl d be 22 ) pl us a r ow of c ol um n c a pt i ons

. D e l e t e a ny da t a t ha t

e xc e e d t hi s l i m i t

. ( F e w e r t ha n 22 l i ne s of da t a a r e O K

. ) T he r e s ul t s houl d l ook l i ke t he e xa m pl e

i n F i gur e 1

, a l t hough t he l i ne w r a ppi ng m a y di f f

e r

.

S t e p 3. O pe n t he C A L P O S T

- I M P R O V E P r oc e s s or i n M i c r os of t E xc e l

. S a ve t he ope n f i l e unde r a

ne w na m e s o t ha t t he o r i gi na l e m p t y pr oc e s s or w i l l r e m a i n a va i l a bl e f or f ut ur e us e

. T he f r on t

w or ks he e t

, l a be l e d “ I nput & O ut put ” l ooks l i ke F i gur e 2. T he r e i s a l a r ge e m pt y box

, s ur r ounde d

by doubl e l i ne s

, i nt o w hi c h t he t a bl e c r e a t e d a bove w i l l be i m por t e d

, a s de s c r i be d be l ow

. 6 O n t he

r i ght i s a box i nt o w hi c h N O

x c onc e nt r a t i ons m a y be e nt e r e d m a nua l l y, a nd a s m a l l box be l ow

t hi s box i s pr ovi de d f or e nt r y of t he us e r ’ s a s s um pt i on of w ha t f r a c t i on of t ha t N O

s i s i n t he f or

m

of N O 2

. T w o s m a l l e r boxe s pr ov i de f o r us e r i nput of t he R a yl e i gh s c a t t e r i ng c oe f f i c i e nt a nd

, opt i ona l l y, s e a s a l t c onc e nt r a t i on f or t he C l a s s I a r e a

, a s de s c r i be d be l ow

. R e s ul t s of t he ne w

I M P R O V E a l gor i t hm c a l c ul a t i ons a ppe a r i n bl ue i n t he l ow e r ha l f o f t he w or ks he e t a nd s om e

a ddi t i ona l r e s ul t s

, t ha t a r e a l s o us e f ul f or qua l i t y c ont r ol

, a ppe a r i n gr e e n t o t he r i gh t of t he l a r ge

box. A t t he m om e nt

, m a ny r e s ul t s c e l l s w i l l di s pl a y nons e ns i c a l num be r s a nd e r r or m e s s a ge s

,

s uc h a s s how n i n F i gur e 2

.

S t e p 4. S e l e c t t he uppe r l e f t c e l l ( A 7) i n t he l a r ge b ox. O n t he E xc e l m e nu ba r

, go t o D at a > G e t

E

x t e r nal D at a a nd c l i c k on I m

por t T e

x t F i l e

. 7 ( I f t h e l a r ge box i s not e m pt y

, c l i c k on E di t T e

x t

I

m

por t i ns t e a d. ) S e l e c t t he f i l e t ha t c ont a i ns t he t a b l e c r e a t e d i n S t e p 2 a nd c l i c k on t he G e t D at a

but t on. G o t hr ough t he T e xt I m po r t W i z a r d s t e ps

, c he c ki ng t ha t a l l va l ue s a ppe a r c or r e c t l y i n

s e pa r a t e c ol um ns

. ( T he l a be l “ C O O R D I N A T E S ( k m ) ” w i l l be s pl i t ove r t w o c ol um ns ; t hi s i s

O K

. ) W he n e ve r yt hi n g a ppe a r s i n o r de r

, c l i c k F i ni s h

.

4 T h e b a ck g ro u n d co n c en t rat i o n s t h at w er e en t ered i n t o C A L P O S T mu s t b e t h e E P A

- p res c ri b ed d e fau l t

an n u al av er ag e n at u ral co n d i t i o n s co n cen t rat i o n s fo r t h e E as t

. T h e p ro ces s o r w i l l n o t g i v e co rr ect an s w ers

i f o t h er co n cen t rat i o n s w er e u s ed i n C A L P O S T

. 5 Fo r fu t u re ref eren ce i n St ep 7

, t h i s may al s o b e a g o o d t i me t o l o cat e t h e t ab l e w i t h t h e s a me t i t l e b u t

w i t h t h e s u b t i t l e “ % o f Mo d el ed E x t i n ct i o n b y Sp eci es ”

, w h i ch ap p ears l at er i n t h e o u t p u t fi l e.

6 If t h e w o rk b o o k h as al re ad y b e en u s ed

, t h e b o x es m ay n o t b e e mp t y

. T h i s d o es n o t m at t er.

7 T h e ex act w o rd i n g may v ary s l i g h t l y b et w een d i ffe ren t v ers i o n s o f Mi cro s o ft E x cel

. T h e t ermi n o l o g y

u s ed h ere i s fro m E x cel 2 0 0 4 fo r Ma ci n t o s h

.6 F i gu r e 1. E xam p l e of C A L P O S T O u t p u t T ab l e , i n P r op e r F or m at f or I m p or t i n g i n t o t h e

C A L P O S T

- I M P R O V E P r oc e s s or

.

S t e p 5. 8 T he “ I m po r t D a t a ” w i ndow w i l l a ppe a r

, w i t h c e l l A 7 i ndi c a t e d a s t he l oc a t i on a t w hi c h

da t a w i l l be e nt e r e d

. C l i c k on t he P r ope r t i e s but t on. I n t he w i ndow t ha t a ppe a r s

, s e l e c t

“ O ve r w r i t e e xi s t i ng c e l l s w i t h ne w da t a

, c l e a r unus e d c e l l s ” a nd unc he c k “ A dj us t c ol um n

w i dt h”

, t he n c l i c k on O K

. N ow c l i c k on t he O K bu t t on i n t he “ I m por t D a t a ” w i ndow

.

S t e p 6. A s s um i ng t ha t your E xc e l a ppl i c a t i on i s s e t up t o a ut om a t i c a l l y r e c a l c ul a t e w he ne ve r a ny

e nt r i e s a r e c ha nge d, you s houl d now ha ve f i l l e d t h e c e l l s i n t he l a r ge bo x on t he f i r s t w or ks he e t

,

8 If t h e p ro c es s o r al r ead y h ad d at a i n i t an d E d i t Text I m

p o r t w as cl i ck ed i n St ep 4

, t h en t h e “ Imp o rt D at a”

w i n d o w w i l l n o t ap p e ar an d St ep 5 can b e s k i p p ed

.7 F i gu r e 2. E xam p l e of A p p e ar an c e of I n p u t & O u t p u t Wor k s h e e t b e f or e D a t a E n t r y

.8 num be r s s houl d ha ve a ppe a r e d i n t he gr e e n c ol um ns t o t he r i ght

, a nd s om e num be r s w i l l

ha ve a ppe a r e d i n t he out pu t t a bl e i n bl ue on t he l o w e r ha l f o f t he w or ks he e t

. I f t he da t a

i m por t w or ke d pr ope r l y

, none of t he i m po r t e d da t a s houl d ha ve s pi l l e d out of t he l a r ge

box. C he c k t ha t a l l t he c ol um n c a pt i ons i n bol d out s i de t he l a r ge box a r e now dup l i c a t e d

on t he f i r s t l i ne i n t he box

. ( T he r e w on’ t be a c a pt i on f or R a nk. )

S t e p 7. A s a f u

r t he r c he c k on w he t he r e ve r yt h i ng i s c or r e c t s o f a r

, t he dv i n f or m a t i on i n

t he t hr e e c ol um ns t o t he r i ght o f t he l a r ge box s houl d be t he s a m e a s t ha t i n t he s e c ond

C A L P O S T t a bl e “ R a nke d D a i l y V i s i bi l i t y C ha nge : % o f M ode l e d E x t i nc t i on by

S pe c i e s ”

, w hi c h w a s m e nt i one d i n F oo t not e 1

.

S t e p 8

. B e ne a t h t he l a r ge box t ha t w a s j us t f i l l e d w i t h i m por t e d da t a

, e nt e r t he R a yl e i gh

s c a t t e r i ng c oe f f i c i e nt f o r t he C l a s s I a r e a of i nt e r e s t i n t o t he t op s m a l l box a f t e r r e d

i ns t r uc t i on 3

. A l s o, i f you w i s h, f i l l i n t he o t he r s m a l l box, t he one a f t e r r e d i ns t r uc t i on 4,

w i t h t he a nnua l a ve r a ge s e a s a l t c onc e nt r a t i on

. ( T h e s e a s a l t box m a y be l e f t bl a nk

, but

t he R a yl e i gh s c a t t e r i ng c oe f f i c i e nt box m us t be f i l l e d i n. ) T o he l p w i t h f i l l i ng i n t he s e t w o

boxe s

, t he f our t h w or ks he e t

, “ R a yl e i gh & S e a S a l t ”

, pr ovi de s I M P R O V E

- c a l c ul a t e d

va l ue s of t he R a yl e i gh c oe f f i c i e nt s f or C l a s s I a r e a s i n t he V I S T A S r e gi on a nd i n a dj a c e nt

s t a t e s

. A l s o, a ve r a ge s e a s a l t c onc e nt r a t i ons f or 20 00

- 2004, c a l c ul a t e d i n a c c or da nc e w i t h

t he ne w I M P R O V E p r oc e dur e s

, c a n be f ound t he r e

.

S t e p 9

. 9 I f t he i m pa c t due t o N O 2 i s t o be c ons i de r e d, a s e c ond C A L P O S T r un w i l l be

ne e de d t o pr ovi de t he 24

- hr a ve r a ge N O

x c onc e nt r a t i ons e s t i m a t e d by C A L P U F F

. F o r

t hi s pur pos e

, r un C A L P O S T us i ng t he A S P E C

= N O X opt i on i n I nput G r oup 1 of t he

C A L P O S T

. I N P c ont r ol f i l e

. T he N O

x va l ue s t o i ns e r t i n t he N O

x i nput box on t he I nput

& O ut put pa ge o f t he pr oc e s s or ha ve t o be e xt r a c t e d m a nua l l y f r om t he C A L P O S T out put

f i l e f o r e a c h da t e a nd r e c e pt or l i s t e d i n t he f i l e t ha t w a s i m por t e d i n S t e ps 1 t h r ough 5

a

bove a nd a r e di s pl a ye d i n t he l e f t ha nd c ol um ns i n t he l a r ge box

.

S t e p 10

. S e l e c t a va l ue be t w e e n 0 a nd 1 t o r e pr e s e nt w ha t f r a c t i on of N O

x i s i n t he f or m

of N O 2

. E n t e r t hi s va l ue i nt o t he s m a l l box a t r e d i ns t r uc t i on 6 be l ow t he c ol um n w he r e

t he N O

x c onc e nt r a t i ons w e r e e nt e r e d. 1 0

S t e p 11

. T he b l ue da t a t a bl e a t t he bot t om of t he pa ge r e pr e s e nt s t he ne w I M P R O V E

a l gor i t hm out put s

. A n e xa m pl e i s s how n i n F i gur e 3

. T h i s t a bl e c a n be c om pa r e d w i t h t he

or i gi na l C A L P O S T t a bl e a t t he t op of t he pa ge

. A l l of t he c ol um ns i n bo t h t a bl e s s how

e xa c t l y t he s a m e va r i a bl e s

, e xc e pt t ha t t he F ( R H ) c ol um n i n t he t op t a bl e i s r e pl a c e d by

j us t t he R H i n t he l ow e r t a bl e ( s i nc e t he ne w pr oc e dur e ha s t hr e e di f f

e r e nt f ( R H )

f unc t i ons ) a nd a ne w ba N O 2 c ol um n ha s be e n a dde d t o t he bot t om t a bl e t o s how t he l i ght

a

bs or pt i on due t o N O 2 ( i n M m - 1 )

. A l t hough t he e v e nt s a r e l i s t e d i n t he s a m e or de r i n bot h

t a

bl e s

, not e t ha t t he i r r a nki ngs m a y ha ve c ha nge d, a s i s t he c a s e f or m a ny of t he l i ne s i n

t he bl ue out put t a bl e i n F i gur e 3.

9 St ep s 8 an d 9 ar e o p t i o n al

. I f t h e i mp act d u e t o N O 2 i s n o t o f i n t eres t

, j u s t l e av e t h e en t ry fi el d s

men t i o n ed i n t h es e s t ep s b l an k

. 1 0 A n e as y w ay t o s ee t h e e ff e ct o f t h e N O 2 o n t h e s o u rc e ’ s i mp a ct i n t h e o u t p u t t ab l e i n t h e l o w er

h al f o f t h e p ag e i s t o t o g g l e t h i s N O 2 / N O

x v al u e b et w e e n t h e s el ect ed v a l u e an d z ero

.9 F or t hos e w ho a r e i nt e r e s t e d i n m or e de t a i l c onc e r ni ng t he c a l c ul a t i ons t ha t t a ke pl a c e

,

va l ue s of t he t h r e e f ( R H ) f unc t i ons a ppe a r i n c ol u m ns M t hr ough O on t he s e c ond,

“ C a l c ul a t i ons ” s pr e a d s he e t

. T he e xt i nc t i on i m pa c t of t he s our c e

, i nc l udi ng e nha nc e m e nt

of t he e xt i nc t i on e f f i c i e nc i e s f o r s ul f a t e s

, n i t r a t e s

, a nd or ga ni c s be c a us e o f gr e a t e r t o t a l

m a s s c onc e nt r a t i ons

, a ppe a r s i n c ol um ns V t hr oug h A C

. E xt i nc t i on due t o t he a nnua l

a ve r a ge na t ur a l ba c kgr ound a ppe a r s i n C ol um ns A J t hr ough A N ; na t u r a l ba c kgr ound

e xt i nc t i on s f or t hos e c om pone nt s t ha t a r e e nha nc e d by gr e a t e r t ot a l m a s s c onc e nt r a t i ons

a

ppe a r i n c ol um ns A U t h r ough A X

.10 F i gu r e 3. E xam p l e of A p p e ar an c e of F i n i s h e d I n p u t & O u t p u t Wor k s h e e t

.11 

### A p p e n d i x

D e t ai l s of C al c u l at i o n A p p r o ac h

A s a n e xa m pl e of t he c a l c ul a t i on s t e ps

, a s s um e t ha t t he s ul f a t e c onc e nt r a t i on r e s ul t i ng

f r om e m i s s i ons f r om a s our c e i s [ S E ] a nd t he s ul f a t e i n t he undi s t urbe d na t ur a l

ba c kgr ound i s [ S N ]

, f or a t ot a l a m bi e nt s ul f a t e c on c e nt r a t i on of [ S T ]

. A c c or di ng t o

E qua t i ons 1 a nd 2 i n t he m a i n body of t hi s doc um e nt

, t he t ot a l e xt i nc t i on due t o s ul f a t e

f

or t hi s c om b i na t i on i s

b

e

x t ( s ul f

at e )

= 2. 2 • f

S (

R H ) • [ s m a l l s ul f

at e ] + 4. 8• f

L (

R

H

) • [ l ar ge s ul f

at e ]

, ( E q. A

- 1 )

w he r e

[ l ar ge s ul f

at e T ]

= {[ S T

] /

20}• [ S T

] i f [ S T

] < 20 μ g 3

[

l ar ge s ul f

at e T ]

= [ S T

] i f [ S T

] ≥ 20 μ g/ m 3 ( E qs

. A

- 2 )

[

s m al l s ul f

at e T ]

= [ S T

]

– [ l ar ge s ul f

at e T ]

,

a nd t he s ubs c r i pt T de not e s t ot a l s ul f a t e

F or t he o r i gi na l ba c kgr ound

, w he r e t he r e i s no s ou r c e i m pa c t

, t he c or r e s pondi ng f or m ul a s

f

or t he t e r m s i n E qua t i on s A

- 2 a r e

[

l ar ge s ul f

at e N

]

= {[ S

N

]

/ 20}• [ S

N

] i f [ S

N

] < 20 μ g 3

[

l ar ge s ul f

at e N

]

= [ S

N

] i f [ S

N

] ≥ 20 μ g/ m 3 ( E qs

. A

- 3 )

[

s m al l s ul f

at e N

]

= [ S

N

]

– [ l ar ge s ul f

at e N

]

,

w he r e t he s ubs c r i pt N de not e s na t ur a l s ul f a t e

.

S i m i l a r c a l c ul a t i ons ne e d t o be c a r r i e d out f or ni t r a t e s

. C ont r i but i ons of t he ot he r

pa r t i c ul a t e c om pone nt s a r e l i ne a r a nd c a n j us t be c a l c ul a t e d a c c or di ng t o E qua t i on 1

.

I f t he i m pa c t due t o N O 2 i s a l s o t o be c ons i de r e d, t he n t he s our c e i m pa c t due t o t hi s

c om pone nt i s

, a c c or di ng t o E qua t i on 1

,

b

e

x t (

N

O 2 )

= 0

. 33• [ N

O 2 ]

, ( E q. A

- 4 )

w he r e [ N O 2 ] i s i n ppb

. I t i s r e a s ona bl e t o a s s um e t ha t t he a m bi e nt N O 2 c onc e nt r a t i ons

unde r na t ur a l c ondi t i ons w oul d be s o s m a l l a s t o c a us e ne gl i gi bl e l i ght a bs or pt i on

, s o t he

c or r e s pondi ng t e r m i s not ne e de d i n t he na t ur a l c o ndi t i ons c a l c ul a t i on

.

T he c ont r i but i ons due t o t he va r i ous c om pone nt s a r e s um m e d t oge t he r a s i n E qua t i on 1 t o

obt a i n t he t ot a l e xt i nc t i on b

e x t

, T a nd t he na t ur a l ba c kgr ound e xt i nc t i on b

e x t

, N

. T he12 f r a c t i ona l c ha nge i n e xt i nc t i on i s t he n c a l c u l a t e d a s t he di f f

e r e nc e

, no r m a l i z e d by t he

na t ur a l ba c kgr ound e xt i nc t i on

( b

e

x t

, T

– b

e x t

, N

) /

b

e

x t

, N

, ( E q. A

- 5 )

a r e s ul t t ha t c a n a l s o be e xpr e s s e d i n de c i vi e w s

.

T he s e f or m ul a s a r e us e d i n t he C A L P O S T

- I M P R O V E P r oc e s s or

. S i m i l a r f or

m ul a s a ppl y

f

or ni t r a t e s a nd or ga ni c s

. T he r e i s no nonl i ne a r i t y i n t he r e m a i ni ng t e r m s i n E qua t i on 1.