Georqia Department of Natural Resources 

Environmental Protection Division Air Protection Branch 

4244 International Parkway Suite 120 Atlanta Georgia 30354 

4041363-7000 Fax: 4041363-71 00 

Noel Holcomb, Commissioner 

Carol A. Couch, PhD., Director 

Heather Abrams, Branch Chief 

August 19,2008 

Mr. J. I. Palmer, Regional Administrator 

U.S. EPA: Region IV 

Atlanta Federal Center 

61 Forsyth Street, SW 

Atlanta, Georgia 30303-8909 

Subject: Request for Approval to Use New IMPROVE Equation for BART Modeling 

Dear Mr. Palmer: 

The Georgia Environmental Protection Division (GA EPD) has been working with the 

Visibility Improvement States and Tribal Association of the Southeast (VISTAS) and the 

U.S. Environmental Protection Agency (EPA) Region IV staff to implement the Best 

Available Retrofit Technology (BART) requirements of the Regional Haze Rule. As part 

of this process, the need for a methodology to post-process CALPUFFICALPOST 

modeling data to implement the new IMPROVE equation was identified. VISTAS 

tasked Dr. lvar Tombach to develop such a methodology. The resulting spreadsheet 

and supporting information was submitted by the State of North Carolina to EPA and the 

Federal Land Managers (FLMs) for 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 : Guideline on Air Quality 

iv7vdeis and that i4CiiAG ~mst obtain approval for its use from the EPA Regional 

Administrator. On the basis of these comments and for the reasons discussed below, 

GA EPD is providing the following additional information and requests a formal approval 

of use of this alternative by the affected sources for BART exemption and BART 

determination modeling. 

Rationale for Use of 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 equation, takes into account the latest 

scientific understanding of several parameters: 

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

and the clearest days as demonstrated by comparing the measured light 

extinction from nephelometers at Class I areas to light extinction calculated using 

each of the equations. 
Mr. J. I. Palmer 

August 19,2008 

Page Two 

2. The new algorithm recognizes spatial and temporal variation in light extinction as 

size distribution of the aerosol changes by increasing extinction efficiency as 

sulfate, nitrate and organic concentrations increase. 

3. The new algorithm incorporates a term to reflect 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. 

4. The new algorithm reflects research finding that the mass concentration of 

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

equation. 

5. The new algorithm includes a NO2 term to represent times when light absorption 

by NO2 is a meaningful contributor to light extinction. 

6. The new algorithm incorporates site-specific Rayleigh scattering values to better 

~spresent sites c!ose t:, sea level or with very hot or cold climates. 

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 strategies since 

the benefits of control of concentrations of each species will be represented more 

correctly with the new algorithm. Further discussion of these reasons is included in 

Enclosure 1. 

Two of Georgia's BART eligible sources, Georgia Pacific Cedar Springs and Georgia 

Power Company-Plant Bowen, have requested the use of the new IMPROVE equation. 

Specifically, the new IMPROVE equation will more accurately represent the spatial and 

temporal variation in light extinction caused by sulfate, nitrate, and organic carbon 

concentrations. As a result, these sources can better determine their contribution to 

haze and more accurately evaluate the benefits of potential control strategies. 

A spreadsheet was developed for VISTAS by Dr. Tombach to implement the entire new 

IMPROVE equation for use with CALPUFF and contains a modification of CALPOST 

that calculates the light extinction from the CALPUFF output. In the review of the 

spreadsheet and supporting documentation, EPA Region IV staff commented that the 

VISTAS methodology contained in the spreadsheet appropriately implements the 

features of the new IMPROVE equation, with the exception of the nitrogen dioxide term. 

EPA Region 4 further stated that it would be acceptable to use the total NOx 

concentration from the CALPOST output as a conservative surrogate for NO2 in order to 

address the NO2 term in the new IMPROVE equation. EPA Region IV indicated, that the 
Mr. J. I. Palmer 

August 19,2008 

Page Three 

VISTAS methodology to incorporate the new IMPROVE equation would be acceptable 

on a case-by-case basis upon consultation with the EPA Regional Office once the NO2 

term was addressed. Since the initial EPA review of the methodology, Dr. Tombach 

has modified the spreadsheet to address the NO2 contribution. A copy of the modified 

spreadsheet and instructions is provided as Enclosure 3 for your review. 

Evaluation Performance versus Measured Values 

Comparison of the old versus new IMPROVE equation and nephelometer data at 

several Class I areas, including Okefenokee and Cohutta, are included in Enclosure 2. 

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 slight high bias. The 

correlation coefficients are often slightly lower for the new equation than the old 

equation because there is slightly m+ore scatter at the low end of the equation. Overall, 

this data indicates that the new equation is overall a much better tool for converting 

mass data into visibility data than the old equation. 

We look forward to your response to this request for approval to use the VISTAS 

methodology for purposes of BART exemption modeling and BART determination 

modeling. Should you have any questions regarding this matter, please contact James 

Boylan at (404) 362-4851. 

Sincerely, 

Carol A. Couch 

Director 

CC:HA:JJ:JK:TV: klc 

c: Jimmy Johnson, GA EPD 

Jim Boylan, GA EPD 

Jim Kelly, GA EPD 

Dick Schutt, EPA Region 4 

Michele Notarianni, EPA Region 4 

Brenda Johnson, EPA Region 4 
Enclosure 1 

DRAFT 10/26/06 

Why Use the New IMPROVE Algorithm? 

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. Excellent justification of this conclusion is 

provided in the November 2005 report of the WROVE Steering Committee, "Revised 

IMPROVE Algorithm for Estimating Light Extinction £?om Particle Speciation Data." 

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 since the old algorithm was developed. The main 

reasons that justify using the new algorithm 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 extinction). 

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

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

reflects this variation by increasing the extinction efficiency as the concentrations 

of sulfates, nitrates, and organics increase. 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 light extinction at 

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

biases in each RPO region 

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

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

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

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

originally developed mainly for inland Class 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). 

4. . The new algorithm acknowledges that substantial recent research has shown that 

the mass concentration of particulate organic 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-appropriatel.8. 
5. The new algorithm recognizes that there may be times (near urban areas or in 

some source emission plumes) when light absorption by NO2 gas is a meaningfd 

contributor to light extinction, and thus includes a new term based on the NO2 

concentration. 

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

of 10 Mrn-' (representative of an elevation of about 5000 feet) may have been 

adequate when only inter-mountain West sites 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 clearest days. This is particularly important for 

the development of emission management strategies, because the benefits of control of 

concentrations of each species will be represented more correctly with the new algorithm. 
Enclosure 2. 

Old IMPROVE 

Figure 1. Aerosol Scattering vs Nephelometer Scattering Comparing New and Old IMPROVE 

Algorithm and Daily f(RH), Great Smoky Mountains National Park, 1995-2004 

New IMPROVE Old IMPROVE 

0 SO Ion iw 266 2W 3Qa 

Figure 2. Aerosol Scattering vs Nephelometer Scattering Comparing New and Old IMPROVE 

Algorithm and Daily f(RH), Cohutta Wilderness Area, 2004 
New IMPROVE 1 1 Old IMPROVE 

Figure 3. Aerosol Scattering vs Nephelometer Scattering Comparing New and Old IMPROVE 

Algorithm and Daily fo, Cape Romain Wildlife Refuge, 2004 

Old IMPROVE 

Figure 4. Aerosol Scattering vs Nephelometer Scattering Comparing New and Old IMPROVE 

Algorithm and Daily f(RH), Okefenokee Wilderness Area, 1993-1997 
lvar Tombach, Ph. D. 

8&dV+ 

753 Grada Ave. 

Camarillo, CA 93010 

805 388-2341 

805 445-9424 fax 

itornbach@aol.com 

Instructions: 

A Postprocessor for Recalculating CALPOST Visibility Outputs 

with the New IMPROVE Algorithm 

Version 2 

14 October 2006 

Introduction 

CALPOST can be used to processes outputs from CALPUFF modeling of a source's emissions 

to calculate the 24-hr average visibility impairments caused by primary and secondary particulate 

matter attributable to emissions from the modeled source. Those increments are presented in two 

tables, both labeled "Ranked Daily Visibility Change", in the CALPOST output (.LST) file. The 

table of interest to us has the subtitle "Modeled Extinction by Species" and lists the dates and 

locations of such incremental impacts in light extinction (bexJ in ranked order, starting with the 

one that represents the largest percentage change in light extinction.' 

In addition, with a different setup of the control file CALPOST.INP, the CALPOST 

postprocessor can be used to calculate 24-hr averages of NOx concentrations. As described 

below, the outputs from that additional CALPOST run can be used to assess the visibility impact 

of the NO2 gas in the source plume. 

Visibility effects due to particulate matter are calculated in CALPOST from CALPUFF-modeled 

particulate matter component concentrations using effectively the "traditional" IMPROVE 

algorithm. CALPOST allows for choice of the humidity scattering enhancement function (f(RH)) 

to be used with the IMPROVE algorithm; for modeling in connection with the US EPA's 

Regional Haze Regulations (RHR), the appropriate form of f(RH) is the one described and 

tabulated in the EPA's 2003 guidance for tracking progress under the RHR. Visibility effects due 

to NO2 are not considered in the CALPOST visibility calculation. 

Recently, the IMPROVE Steering Committee developed a new algorithm for estimating light 

extinction from particulate matter component concentrations. This algorithm (the "new 

IMPROVE algorithm") provides a better correspondence between the measured visibility and 

The other table in the CALPOST visibility output file, with the subtitle "% of Modeled Extinction by 

Species", provides equivalent results in terms of changes in the haze index, in deciviews. The two tables 

represent the same results, with identical ranking of events, while just using different (but mathematically 

related) metrics. 
that calculated from particulate matter component concentrations. The new algorithm differs in 

several substantive ways from the traditional one: 

The extinction efficiencies of sulfates, nitrates, and organics have been changed and are 

now functions of their concentrations. The extinction efficiencies of sulfate and nitrate 

are no longer identical, although the new hygroscopic scattering enhancement factors 

applied to them are the same. 

The concentration of particulate organic matter (POM; variously also labeled OCM or 

OMC, and sometimes just called "organics") is now taken to be 1.8 times that of the 

measured organic carbon (OC) concentration. (Confusingly, CALPOST labels the 

organics concentration as OC.) 

The contribution of fine sea salt to light extinction has been added, and is accompanied 

by its own hygroscopic scattering enhancement factor, f,,(RH). 

The light scattering by air itself (Rayleigh scattering) now varies with site elevation and 

mean temperature. It is to be rounded off to the nearest one ~m-' when used with the 

new algorithm. 

The light absorption by NO2 gas has been added. 

The new IMPROVE algorithm is represented by the following formu~a:~ 

bat = 2.2fs(RH)*[small sulfate] + 4.8f~(')*[large sulfate] 

+2.4.fs(RH).[small nitrate] + 5.1 $(RH)-[large nitrate] 

+2.8-[small organics] + 6.1 *[large organics] 

+I 0-[elemental carbon] 

+I-fine soil] 

+l. 7.fss(M)-[sea salt] 

+O. 6-[coarse matter] 

+Rayleigh scattering (site spec@) 

+O. 33*[NO.&pb)] 

The concentrations of "large" and "small" sulfate particles are calculated as follows: 

[large sulfate] = {[total sulfate]/20)-[total sulfate] $[total sulfate] < 20 ,ug3 

[large sulfate] = [total sulfate] $[total suljbte] 1 20 ,ug/m3 (Eqs- 2) 

[small sulfate] = [total sulfate] - [large sulfate]. 

Identical formulas, with changes in component names, are used for nitrate and organics. In 

effect, these formulas conclude that low concentrations of these components are mainly in the 

form of "small" particles with their own extinction efficiency and fs(RH), while high 

Square brackets denote concentrations. 
concentrations (approaching 20 &m3) are mainly in the form of "large" particles with a 

different extinction efficiency and ~L(RH). The scaling factor [total sulfate]/20 sets the fraction of 

total sulfate that is small. 

The sea salt concentration is taken to be 1.8*[Cl-] or, if chloride ion measurements are not 

available, the chlorine concentration can be used in its place. Site specific Rayleigh scattering 

values have been calculated for all IMPROVE sites.3 Nitrogen dioxide concentrations are not 

measured at IMPROVE sites, but the ambient NO2 concentrations under natural conditions can 

be expected to be negligibly small. The higher NO2 concentration in a source plume may be 

great enough to cause a change in visibility, however. 

In order to enable CALPOST to calculate CALPUFF-modeled source impacts on visibility using 

the new IMPROVE algorithm, it would have to be extensively reprogrammed. As an alternative, 

such a calculation could be done "off line" by adding another layer of post processing after 

CALPOST. To this end, I have developed a processor, in the form of an Excel workbook, that 

takes the CALPOST "Ranked Daily Visibility Change: Modeled Extinction by Species" output 

table, referenced against default annual average natural conditions concentrations, and creates an 

equivalent table of results based on the new algorithm. It can also incorporate the visibility 

impact due to light absorption by NO2 in the plume. 

The following describes the science behind the processor (which we'll call the CALPOSTIMPROVE Processor) and provides instructions for using it. 

Concepts 

In addition to the mechanical changes imposed by all the new terms in the new IMPROVE 

formula, applying the new algorithm also requires some conceptual changes. The biggest of 

these is that the extinction efficiencies of sulfates, nitrates, and organics now depend on the 

concentrations of those species. The practical implication of this is that extinction is no longer 

linearly additive. To calculate total extinction, you cannot take a background level of extinction 

and add to it CALPOST's calculation of extinction caused by the particulate matter coming from 

a source, because when the two aerosols mix in the atmosphere their combined mass 

concentration results in increases in the extinction efficiencies of both the background and the 

source contribution. This means that combining background particulate matter with the 

particulate matter from a source gives an extinction result that is greater than the sum of the two 

separate extinctions. 

With the nonlinear behavior resulting from applying the new IMPROVE algorithm, the 

extinction impact of the source (i.e., the increase in extinction resulting from introducing source 

emissions into the atmosphere) is the sum of three parts: 

1. The source impact calculated by the new IMPROVE algorithm using the CALPOST 

outputs for a plume in isolation; 

Revised IMPROVE Algorithm for estimating Light Extinction from Particle Speciation Data. Report to 

IMPROVE Steering Committee, November 2005. 
2. An increase in that source impact because the extinction efficiency increases when the 

source's aerosol combines with the background aerosol; and correspondingly, 

3. An increase in the extinction of the background aerosol because of that same mixing. 

The total new extinction is the sum of the above three components plus the original background 

extinction. The original background extinction is just that calculated by the new IMPROVE 

algorithm fiom background concentrations of the various components, without any consideration 

of the effects of the plume. For this application, the background is taken to be that described by 

EPAYs default natural conditions. The difference between the total extinction and the background 

is the impact of the source. 

More details about the calculation are given in the appendix. 

Description of Processor 

The CALPOST-IMPROVE Processor is a Microsoft Excel workbook that consists of four 

worksheets. In Version 2 the worksheets are the following. 

Input & Output -The output table from CALPOST is imported to here and user entries 

are made for the Rayleigh scattering coefficient and, if desired, for a sea salt 

concentration at the Class I area of interest. The NO, concentration on each day 

attributable to the emissions fiom the source can also be entered together with an 

assumption of what fi-action of the NOx is in the form of NOz. A revised table, with 

extinction based on the new IMPROVE algorithm is then presented on the same page. 

This is the only page on which user input takes place, and the results of the calculations 

appear on this page. 

Calculations -- The calculations themselves are all done on this worksheet. There is no 

user input to this page. The variables are explained on the worksheet itself, so the user 

can find intermediate values if so inclined. 

F(RH) - This worksheet tabulates the traditional IMPROVE f(RH) against RH, and then 

also lists values for the three new humidity growth functions, fs(RH), fL(RH), and 

fss(RH). It serves as a lookup table for the "Ca1cu1ations" worksheet. 

Rayleigh & Sea Salt - This page tabulates the IMPROVE-recommended Rayleigh 

scattering coefficients for all VISTAS Class I areas and for Class I areas in adjacent 

states. It also lists the average sea salt concentrations for the same locations, as tabulated 

on the VIEWS web site, based on chloride or chlorine measurements by IMPROVE 

monitors between 2000 and 2004. This sheet just provides information for the user; it is 

not linked to the rest of the workbook. The user can obtain Rayleigh and sea salt numbers 

for the Class I area of interest fiom this table and then manually enter them in the 

designated spaces in worksheet 1. 
Instructions for Using the CALPOST-IMPROVE Processor 

These instructions apply to Version 2 of the processor. Version 2 includes the ability to calculate 

the light extinction effects of NO2 resulting from the source's emissions. 

Step 1. Begin by opening the output (.LST) file from a CALPOST visibility calculation run in a 

text editor or word processing program.4 In the second half of the file, locate the table "Ranked 

Daily Visibility Change" with the subheading "Modeled Extinction by 

Step 2. Copy this table and paste it onto a new page. Save it as a text (.txt) file, not as a formatted 

(e.g., MS Word .doc or .rtf) file. The final table should contain only the column headings and the 

data. Delete all other captions, any additional data summaries at the end, and blank lines before 

or after the table. The processor can handle a maximum of 22 lines of data (i.e., the highest rank 

in the last, unlabeled, column should be 22) plus a row of column captions. Delete any data that 

exceed this limit. (Fewer than 22 lines of data are OK.) The result should look like the example 

in Figure 1, although the line wrapping may differ. 

Step 3. Open the CALPOST-IMPROVE Processor in Microsoft Excel. Save the open file under a 

new name so that the original empty processor will remain available for future use. The front 

worksheet, labeled "Input & Output" looks like Figure 2. There is a large empty box, surrounded 

by double lines, into which the table created above will be imported, as described be10w.~ On the 

right is a box into which NOx concentrations may be entered manually, and a small box below 

this box is provided for entry of the user's assumption of what fraction of that NO, is in the form 

of NO2. Two smaller boxes provide for user input of the Rayleigh scattering coefficient and, 

optionally, sea salt concentration for the Class I area, as described below. Results of the new 

IMPROVE algorithm calculations appear in blue in the lower half of the worksheet and some 

additional results, that are also useful for quality control, appear in green to the right of the large 

box. At the moment, many results cells will display nonsensical numbers and error messages, 

such as shown in Figure 2. 

Step 4. Select the upper left cell (A7) in the large box. On the Excel menu bar, go to DataBGet 

External Data and click on Import Text ~ile.~ (If the large box is not empty, click on Edit Text 

Import instead.) Select the file that contains the table created in Step 2 and click on the Get Data 

button. Go through the Text Import Wizard steps, checking that all values appear correctly in 

separate columns. (The label "COORDINATES (km)" will be split over two columns; this is 

OK.) When everything appears in order, click Finish. 

4 The background concentrations that were entered into CALPOST must be the EPA-prescribed default 

annual average natural conditions concentrations for the East. The processor will not give correct answers 

if other concentrations were used in CALPOST. 

For future reference iil Step 7, this may also be a good time io locate the table wiih the same title but 

with the subtitle "% of Modeled Extinction by Species", which appears later in the output file. 

If the workbook has already been used, the boxes may not be empty. This does not matter. 

The exact wording may vary slightly between different versions of Microsoft Excel. The terminology 

used here is from Excel 2004 for Macintosh. 
YEAR DAY HR RECEPTOR COORDINATES (km) TYPE BEXT(Mode1) BEXT(BKG) 

BEXT(Tota1) %CHANGE F(RH1 bxS04 bxN03 bxOC bxEC bxPMC bxPMF 

Figure 1. Example of CALPOST Output Table, in Proper Format for Importing into the 

CALPOST-IMPROVE Processor. 

Step 5.' The "Import Data" window will appear, with cell A7 indicated as the location at which 

data will be entered. Click on the Properties button. In the window that appears, select 

"Overwrite existing cells with new data, clear unused cells" and uncheck "Adjust column 

width", then click on OK. Now click on the OK button in the "Import Data" window. 

Step 6. Assuming that your Excel application is set up to automatically recalculate whenever any 

entries are changed, you should now have filled the cells in the large box on the first worksheet, 

If the processor already had data in it and Edit Text Import was clicked in Step 4, then the "hpoi-t Data" 

window will not appear and Step 5 can be skipped. 
. At cell A7, import "Ranked Daily Visibility Change" (bext) table, ~ncluding column headings, 

2. Check calculated values below 5. (Optional) 

agalnst CALPOST% "Ranked Daily Enter 24hr 

-om CALPOST (22 days, nlax) V~siblh~ Chsltge" (dv) table NOx conc. 

EARDAY HR RECEPTOR COORDINATES (km) TYPE BEXT(Mode1) BEXT(BKG)BEXT(Total) %CHANGE F(RH) bxSO4 bxNO3 bxOC bxEC bxPMC bxPMF Rank NOx(ppb) dv!total\ dv(bk0' ' '-NUMl ' iNLlMl Nut41 ' "NUM1 " JNLINI * 4NUMI ' %NUMI ' 8NUMI * INCIM~ Adv I 

. (Optaonnl) Insert .tnnuat average sea salt concentration, from "Raylelgh Sea Salt" 

mrksheet. Leave blenk if not used, 1.e. default Is 0. 

Figure 2. Example of Appearance of Input & Output Worksheet before Data Entry. 
numbers should have appeared in the green columns to the right, and some numbers will 

have appeared in the output table in blue on the lower half of the worksheet. If the data 

import worked properly, none of the imported data should have spilled out of the large 

box. Check that all the column captions in bold outside the large box are now duplicated 

on the fust line in the box. (There won't be a caption for Rank.) 

Step 7. As a further check on whether everything is correct so far, the dv information in 

the three columns to the right of the large box should be the same as that in the second 

CALPOST table "Ranked Daily Visibility Change: % of Modeled Extinction by 

Species", which was mentioned in Footnote 1. 

Step 8. Beneath the large box that was just filled with imported data, enter the Rayleigh 

scattering coefficient for the Class I area of interest into the top small box after red 

instruction 3. Also, if you wish, fill in the other small box, the one after red instruction 4, 

with the annual average sea salt concentration. (The sea salt box may be left blank, but 

the Rayleigh scattering coefficient box must be filled in.) To help with filling in these two 

boxes, the fourth worksheet, "Rayleigh & Sea Salty', provides IMPROVE-calculated 

values of the Rayleigh coefficients for Class I areas in the VISTAS region and in adjacent 

states. Also, average sea salt concentrations for 2000-2004, calculated in accordance with 

the new IMPROVE procedures, can be found there. 

Step 9.' If the impact due to NO2 is to be considered, a second CALPOST run will be 

needed to provide the 24-hr average NO, concentrations estimated by CALPUFF. For 

this purpose, run CALPOST using the ASPEC = NOX option in Input Group 1 of the 

CALPOST.INP control file. The NO, values to insert in the NO, input box on the Input 

& Output page of the processor have to be extracted manually from the CALPOST output 

file for each date and receptor listed in the file that was imported in Steps 1 through 5 

above and are displayed in the left hand columns in the large box. 

Step 10. Select a value between 0 and 1 to represent what fraction of NOx is in the form 

of NO2. Enter this value into the small box at red instruction 6 below the column where 

the NO, concentrations were entered.'' 

Step 11. The blue data table at the bottom of the page represents the new IMPROVE 

algorithm outputs. An example is shown in Figure 3. This table can be compared with the 

original CALPOST table at the top of the page. All of the columns in both tables show 

exactly the same variables, except that the F(RH) column in the top table is replaced by 

just the RH in the lower table (since the new procedure has three different f(RH) 

fimctions) and a new baNO2 column has been added to the bottom table to show the light 

absorption due to NO2 (in ~m-I). Although the events are listed in the same order in both 

tables, note that their rankings may have changed, as is the case for many of the lines in 

the blue output table in Figure 3. 

Steps 8 and 9 are optional. If the impact due to NO2 is not of interest, just leave the entry fields 

mentioned in these steps blank. 

lo An easy way to see the effect of the NO2 on the source's impact in the output table in the lower 

half of the page is to toggle this N02/NO, value between the selected value and zero. 
For those who are interested in more detail concerning the calculations that take place, 

values of the three f(RH) functions appear in columns M through 0 on the second, 

"Calculations" spreadsheet. The extinction impact of the source, including enhancement 

of the extinction efficiencies for sulfates, nitrates, and organics because of greater total 

mass concentrations, appears in columns V through AC. Extinction due to the annual 

average natural background appears in Columns AJ through AN; natural background 

extinctions for those components that are enhanced by greater total mass concentrations 

appear in columns AU through AX. 
1. At cell A?, import "Ranked Dally Visibility Change" (bext) table, including column headings, 2. Check calculated values below 5. (Opttonal) 

from CALPOST (22 days, max) against CALPOST's "Ranked Dally Enter 24hr 

Vlslblllty Change" (dv) table NO% conc. 

NWPW 

dv~lolal) dv(bkg) Aclv 

Q <I9 7 72 2 26 

4.923 21.65 26.573 22.74 3.5 4.475 0 404 0.038 0.001 0.001 0.004 2 9 77 7 72 2 05 

3.15 21.47 24.62 14.67 3.3 2.684 0.428 0.033 0.001 0.001 0.003 3 9 01 / 64 1 37 

2.594 21.29 23.884 12 18 3.1 2.017 0.557 0.018 0,001 0 0.002 4 8 71 / 56 1 15 

2.502 21.47 23.972 11.65 3.3 2.269 0.201 0.028 0,001 0,001 0.003 5 874 164 110 

2.011 21.83 23.841 9.21 3.7 1.963 0.031 0.015 0,001 0 0.001 6 8 69 7 81 0 88 

1.872 21.2 23.072 8.83 3 1.542 0.32 0.009 0 0 0.001 7 8 Po 7 51 0 8'1 

1.649 21.65 23.299 7.62 3.5 1.625 0.012 0.01 0 0 0.001 S4U 7 12 U 13 

1.524 22.19 23.714 6.87 4.1 1.482 0.0290.011 0 0 0,001 863 797 066 

1.459 21.47 22.929 6.8 3.3 1.284 0.16 0.014 0.001 0 0.001 1 8 30 7.64 0.66 

21.47 22.906 6.69 3.3 1.281 0.14 0.013 0 0 0,001 1 8 29 7 64 l 65 

21.47 22.74 5.92 3.3 1.202 0.058 0.009 0 0 0.001 1 8 22 7 64 0 57 

22.1 23.337 8 47 7.?3 0 54 

8 45 7.03 0.52 

8 0') 7 64 0 45 

6 12 7 72 0 40 

/ 99 7 60 0.39 

7 93 7.56 0.3s 

7 94 7.60 0 34 

8 06 7 72 0.3, 

7 8s 7 56 0 32 

8 22 7.93 0.29 

Figure 3. Example of Appearance of Finished Input & Output Worksheet. 
Appendix 

Details of Calculation Approach 

As an example of the calculation steps, assume that the sulfate concentration resulting 

from emissions from a source is [SE] and the sulfate in the undisturbed natural 

background is [SN], for a total ambient sulfate concentration of [ST]. According to 

Equations 1 and 2 in the main body of this document, the total extinction due to sulfate 

for this combination is 

b,,(sulfate) = 2.2.fs(RH)*[small sulfate]+ 4.8.fL(RH)*[large sulfate], (Eq. A-1) 

where 

(Eqs. A-2) 

[small sulfateT] = [ST] - [large sulfateT], 

and the subscript T denotes total sulfate 

For the original background, where there is no source impact, the corresponding formulas 

for the terms in Equations A-2 are 

[large sulfate^] = [SN] if[S~] > 20 ,ug/m3 (Eqs. A-3) 

[small sulfate^] = [SN] - [large sulfate^], 

where the subscript N denotes natural sulfate. 

Similar calculations need to be carried out for nitrates. Contributions of the other 

particulate components are linear and can just be calculated according to Equation 1. 

If the impact due to NO2 is also to be considered, then the source impact due to this 

component is, according to Equation 1, 

where PO2] is in ppb. It is reasonable to assume that the ambient NO2 concentrations 

under natural conditions would be so small as to cause negligible light absorption, so the 

corresponding term is not needed in the natural conditions calculation. 

The contributions due to the various components are summed together as in Equation I to 

obtain the total extinction bext,T and the natural background extinction bext,N. The 
fractional change in extinction is then calculated as the difference, normalized by the 

natural background extinction 

a result that can also be expressed in deciviews. 

These formulas are used in the CALPOST-IMPROVE Processor. Similar formulas apply 

for nitrates and organics. There is no nonlinearity in the remaining terms in Equation 1.