Attachment I 

Answers to the nine specific questions from the CEC Record of Conversation 

1. Has the SJVAPCD provided the methodology used in developing the 

interpollutant trading ratios to either U.S. EPA or the California Air Resources 

Board for comment and/or review? 

A. Yes. Projects triggering New Source Review that contain this analysis 

method have been submitted to both US EPA and CARB for their review. The 

modeling methods used to prepare the basis for the analysis were submitted to 

both US EPA and CARB as part of prior State Implementation Plan (SIP) 

submissions. Modeling protocols were submitted to both US EPA and CARB for 

this SIP modeling. The Chemical Mass Balance (CMB) modeling was performed 

by CARB in consultation with the District and the District performed speciated 

rollback modeling based on the results of CMB output that were submitted for 

review by both US EPA and CARB. The use of these modeling results as the 

basis for the interpollutant assessment was selected due to the extensive review 

which this information has already received. 

2. What is the role of the Chemical Mass Balance modeling in developing the 

ratios? 

A. CMB receptor analysis provides evaluation which differentiates motor vehicle 

exhaust and vegetative burning from industrial emissions. An interpollutant 

relationship requires identifying how much particulate is observed per ton of 

emissions released. A ratio determination would only be qualitative without the 

ability to separate industrial emissions from other sources. CMB does not 

provide the full analysis by itself. The analysis also uses speciated rollback, with 

consideration of spatial extent of contributing sources, and regional modeling, to 

provide the nonlinear relationship for secondary formation of particulates from 

nitrogen oxides and sulfur oxides. 

3. What years of ambient air quality data were used and how do the 

interpollutant ratios vary over the years? 

A. Much of the analysis was conducted using the extensive evaluation of special 

sampling collected in 1999-2001 for the California Regional PM10/PM2.5 Air 

Quality Study (CRPAQS). Extensive evaluation was used to identify contributing 

sources and spatial influence of sources. Additionally, the speciation analysis 

projected the results to design value years for the SIP and future projected years. 

Recent reevaluation with new regional modeling conducted for the 2008 PM2.5 

Plan answers the second part of the question by showing that there is very little 

change projected for the ratio between 2005 and 2014 (summary of the 

evaluation is included as an attachment). This information was not available at 

the time of the evaluation of this project. 
4. Does the inventory of sulfate emissions (shown in the Avenal FDOC as 3.15 

ton per day for Kings and Tulare County, with a typo saying “NOx” on the 

SJVAPCD sulfate spreadsheet) include the inventory of banked sulfur dioxide 

credits for that area, and if not, should it? 

A. No, banked emission reduction credits are not included in the inventory, and 

they do not need to be included. District SIP modeling procedures include 

forecasting of growth for future years for all emission categories. Experience at 

the District has indicated that growth projections adequately represent the future 

increases. It is not reasonable to assume that the use of emission credits would 

be larger than the maximum of trends of industrial growth. Therefore, the growth 

estimate is considered as a reasonable estimate of emissions increase with or 

without the use of emission credits. 

5. In the February 13, 2009 “Draft Initial Comments” on the PSA from Avenal 

Power Center to CEC, Avenal says that “the relevant emission inventory and 

ambient air quality data for purposes of evaluating interpollutant trading ratios 

should come from the general vicinity of the new source of emissions [...].” CEC 

staff asks, how is the wider geographical scope considered, given that the 

locations of the proposed SOx credits (mainly from Stockton or Kern County) are 

outside the boundaries of the Kings and Tulare County inventory? 

A. The ratio analysis was conducted on a County specific basis. The wider 

scope of particulate influence is accounted for in District SIP modeling, but not in 

terms pertinent to this question. Provisions within the District New Source 

Review Rule (Rule 2201, Section 4.8) adjust for the use of offsite reductions. 

6. Given that the inventory of Kings and Tulare County is used to develop the 

ratio, should Avenal be required to surrender only credits from Kings and Tulare 

County? 

A. No. Only if the proposed project was, by itself, capable of producing a local 

exceedance of the ambient air quality standard would it be necessary to require 

credits that are local. The creation or retirement of credits from areas with higher 

PM levels should be considered as highly desirable; therefore, the use of credits 

issued with Kern County should be especially favorable, but no special weighting 

criteria has been established to encourage this use. The District New Source 

Review Rule allows the use of credits issued in the San Joaquin Valley with 

appropriate consideration for distance from the proposed emission source. 

7. Should a separate interpollutant ratio be applied to each credit considering the 

inventory and air quality of the vicinity of each original credit, rather than use a 

single local ratio for all distant credits? 
A. No, District regulations call for the analysis to establish reasonable 

requirements for the proposed facility location. The atmospheric relationships 

where a credit was issued are not germane to the evaluation of the proposed 

facility. 

8. Should a single district-wide interpollutant trading ratio, or the worst-case of 

the vicinity interpollutant ratios, be applied to all new source transactions in the 

district, since new sources may use credits from parts of the district with different 

local inventories and air quality? 

A. Not for this request. The District had not determined at the time of this project 

what a District-wide ratio should be. The evaluation was conducted at a local 

level in accordance with District regulations, as has been done in past projects. 

Recent requests for a ratio evaluation in the Northern part of the San Joaquin 

Valley have led to a determination that a valley-wide approach will be the best 

option for the District to address these requests in the future. This constitutes a 

change from policy in effect when the Avenal request was processed. 

9. What would be the interpollutant trading ratio considering a district-wide 

inventory and district-wide ambient air quality data? 

A. A valley-wide ratio has recently been determined, and the evaluation 

summary is included as an attachment. This was evaluated with new modeling 

conducted for the 2008 PM2.5 Plan and establishes a ratio of 1:1 for SOx to 

PM2.5 and PM10 and 2.63:1 for NOx to PM2.5 and PM10, for projects received 

in 2009 and thereafter to 2014. This information was not available at the time of 

the original evaluation for Avenal. 
Attachment II 
Interpollutant Offset Ratio Explanation 

The Air District’s Rule 2201, “New and Modified Source Review”, requires facilities to 

supply “emissions offsets” when a permittee requests new or modified permits that 

allow emissions of air contaminants above certain annual emission offset thresholds. 

In addition, Rule 2201 allows interpollutant trading of offsets amongst criteria pollutants 

and their precursors upon the appropriate scientific demonstration of an adequate 

trading ratio, herein referred to as the interpollutant ratio. A technical analysis is 

required to determine the interpollutant offset ratio that is justified by evaluation of 

atmospheric chemistry. This evaluation has been conducted using the most recent 

modeling analysis available for the San Joaquin Valley. The results of the analysis are 

designed to be protective of health for the entire Valley for the entire year, by applying 

the most stringent interpollutant ratio throughout the Valley. 

It is appropriate for District particulate offset requirements to be achieved by either a 

reduction of directly emitted particulate or by reduction of the gases, called particulate 

precursors, which become particulates from chemical and physical processes in the 

atmosphere. The District interpollutant offset relationship quantifies precursor gas 

reductions sufficient to serve as a substitute for a required direct particulate emissions 

reduction. Emission control measures that reduce gas precursor emissions at the 

facility may be used to provide the offset reductions. Alternatively, emission credits for 

precursor reductions may be used in accordance with District regulations. 

The amount of particulate formed by the gaseous emissions must be evaluated to 

determine how much credit should be given for the gaseous reductions. Gases 

combine and merge with other material adding molecular weight when forming into 

particles. Some of the gases do not become particulate matter and remain a gas. 

Both the extent of conversion into particles and resulting weight of the particles are 

considered to establish mass equivalency between direct particulate emissions and 

particulate formed from gas precursors. The Interpollutant offset ratio is expressed as 

a per-ton equivalency. 

The District interpollutant analysis uses the most recent and comprehensive modeling 

of San Joaquin Valley particulate formation from sulfur oxides (SOx) and nitrogen 

oxides (NOx). Modeling compares industrial directly emitted particulate to particulate 

matter from precursor emissions. The interpollutant modeling procedure, assumptions 

and uncertainties are documented in an extensive analysis file. Additional 

documentation of the modeling procedure for the San Joaquin Valley is contained in 

the 2008 PM2.5 Plan and its appendices. The 2008 PM2.5 Plan provides evaluation of 

the atmospheric relationships for direct particulate emissions and precursor gases 

when they are highest during the fourth quarter of the year. The southern portion of 

the Valley is evaluated by both receptor modeling and regional modeling of chemical 

relationships for precursor particulate formation. Regional modeling was conducted for 

the entire Valley through 2014. The two modeling approaches are combined to 

determine interpollutant offset ratios applicable to, and protective of, the entire Valley 

(SOx for PM 1:1 and NOx for PM 2.629:1). 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO 

For the proposed substitution of reductions of sulfur oxides (SOx) 

or nitrogen oxides (NOx) for directly emitted particulate matter 

March 2009 

INTRODUCTION .......................................................................................................................................................2

ANALYSES INCLUDED IN INTERPOLLUTANT EVALUATION ....................................................................3

FACTORS CONSIDERED ..............................................................................................................................................3

ELEMENTS FROM 2008 PM 2.5 PLAN.........................................................................................................................3

EXTENSION BY ADDITIONAL ANALYSIS......................................................................................................................4

STRENGTHS ...............................................................................................................................................................4

LIMITATIONS .............................................................................................................................................................5

ANALYSES CONTAINED IN RECEPTOR MODELING.....................................................................................6

FACTORS CONSIDERED ..............................................................................................................................................6

ANALYSES IN RECEPTOR MODELING THAT USE INPUT FROM REGIONAL MODELING ...................................................6

EXTENSION BY ADDITIONAL ANALYSIS......................................................................................................................6

STRENGTHS ...............................................................................................................................................................6

LIMITATIONS .............................................................................................................................................................7

ANALYSES CONTAINED IN REGIONAL MODELING .....................................................................................8

FACTORS CONSIDERED ..............................................................................................................................................8

EXTENSION BY ADDITIONAL ANALYSIS......................................................................................................................8

STRENGTHS ...............................................................................................................................................................9

LIMITATIONS .............................................................................................................................................................9

RESULTS AND DOCUMENTATION....................................................................................................................10
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

2

Introduction 

Goal of Interpollutant Evaluation: Establish the atmospheric exchange 

relationship for substitution of alternative pollutant or precursor reductions for 

required reductions of directly emitted particulate

Evaluation to establish the atmospheric relationship of different pollutants is required as 

a prerequisite for establishing procedures for allowing a required reduction to be met by 

substitution of a reduction of a different pollutant or pollutant precursor. Proposed new 

facility construction or facility modifications may result in increased emissions of a 

pollutant. The District establishes requirements for reductions of the pollutant to “offset” 

the proposed increase. A facility may propose a reduction of an alternative pollutant or 

pollutant precursor where reductions of that material have already been achieved at the 

facility beyond the amount required by District regulations or where emission reductions 

credits for reductions achieved by other facilities are economically available; however, 

for such a substitution to be allowed the District must establish equivalency standards 

for the substitution. The equivalency relationship used for offset requirements is 

referred to in this discussion as the interpollutant ratio. The interpollutant ratio is a 

mathematical formula expressing the amount of alternative pollutant or precursor 

reduction required to be substituted for the required regulatory reduction. This 

discussion is limited to the atmospheric relationships and does not address other policy 

or regulatory requirements for offsets such as are contained in District Rule 2201. 

The following description is provided to explain key elements of the analysis conducted 

to develop the atmospheric relationship between the commonly requested substitutions. 

Emission reductions of sulfur oxide emissions or nitrogen oxide emissions are proposed 

by many facilities as a substitution for reduction of directly emitted particulates. 

Elemental and organic carbon emissions are the predominant case and dominant 

contribution to directly emitted particulate mass from industrial facilities, although other 

types of directly emitted particulates do occur. Therefore this atmospheric analysis 

examines directly emitted carbon particulates from industrial sources in comparison to 

the formation of particles from gaseous emissions of sulfur oxides and nitrogen oxides. 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

3

Analyses included in Interpollutant evaluation 

 Factors Considered 

The foundation for this analysis is provided by the atmospheric modeling conducted for 

the 2008 PM2.5 Plan. Modeling conducted for this State Implementation Plan was 

conducted by the District and the California Air Resources Board using a variety of 

modeling approaches. Each separate model has technical limitations and uncertainties. 

To reduce the uncertainty of findings, a combined evaluation of results of all of the 

modeling methods is used to establish “weight of evidence” support for technical 

analysis and conclusions. The modeling methods are supported by a modeling protocol 

which was sent to ARB and EPA Region IX for review and was included in the 

appendices to the Plan. 

The analysis file prepared for the interpollutant ratio evaluation includes emissions 

inventories, regional model daily output files, chemical mass balance modeling and 

speciated rollback modeling as produced for the 2008 PM2.5 Plan. This well examined 

and documented modeling information was used as a starting point for additional 

evaluation to determine interrelationships between directly emitted pollutants and 

particulates from precursors. 

The interpollutant ratio analysis is limited to evaluation of directly emitted PM2.5 from 

industrial sources and formation of PM2.5 from precursor gases. While both directly 

emitted particulates and particulate from precursor gases also occur in the PM10 size 

range, there is much more uncertainty associated with deposition rates and particle 

formation rates for the larger size ranges. Additionally, because PM2.5 is a subset of 

PM10; all reductions of PM2.5 are fully creditable as reductions towards PM10 

requirements. This analysis concentrates on the quarter of the year when both directly 

emitted carbon from industrial sources and secondary particulates are measured at the 

highest levels. Assessing atmospheric ratios at low concentrations is subject to much 

greater uncertainty and has limited value toward assessment of actions to comply with 

the air quality standards. 

 Elements from 2008 PM 2.5 Plan 

• Regional modeling daily output for eleven locations 

• Chemical Mass Balance (CMB) modeling for four locations – source analysis, 

speciation profile selection, event meteorology evaluation 

• Receptor speciated rollback modeling with adjustment for nitrate nonlinearity for four 

locations, evaluation of spatial extent of contributing sources 

• Emission inventories and projections to future years as developed for the 2008 PM 

2.5 Plan 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

4

• Modeling protocols for receptor modeling, regional modeling, and Positive matrix 

Factorization (PMF) analysis and evaluation of technical issues applicable to 

particulate formation in the San Joaquin Valley 

• Model performance analysis as documented in appendices to the 2008 PM 2.5 Plan 

Extension by additional analysis 

Additional evaluation was conducted to evaluate the receptor modeling relationship 

between direct PM from industrial sources and sulfate and nitrate particulate formed 

from SOx and NOx precursor gases. Area of influence adjustments were evaluated to 

ensure appropriate consideration of contributing source area for different types of 

pollutants for both directly emitted and secondary particulate. This evaluation was 

possible only for the southern four Valley counties and was conducted for both 2000 

and 2009. 

The regional model output was evaluated for the fourth quarter to evaluate general 

atmospheric chemistry in 2005 and 2014 to determine the correlation between northern 

and southern areas of the Valley. This evaluation determined that the atmospheric 

chemistry observed and modeled in the north was within the range of values observed 

and modeled in the southern SJV. This establishes that a ratio protective of the 

southern Valley will also be protective in the north. 

The District determined from the additional analyses of both receptor and regional 

modeling that the most stringent ratio determined for the southern portion of the Valley 

would also be protective of the northern portion of the Valley. Due to the regional 

nature of these pollutants, actions taken in other counties must be assumed to have at 

least some influence on other counties; therefore to achieve attainment at the earliest 

practical date it is appropriate to require all counties to establish a consistent 

interpollutant ratio for the entire District. 

 Strengths 

The interpollutant ratio analysis uses established and heavily reviewed modeling and 

outputs as foundation data. Analysis of model performance has already been 

completed for the models and for the emissions inventories used for this analysis. The 

modeling was performed in accordance with protocols developed by the District and 

ARB and in accordance with modeling guidelines established by EPA. The combination 

of modeling approaches provides an analysis for the current year and provides 

projection to 2014. Weight of evidence comparison of various modeling approaches 

establishes the reliability of the foundation modeling, with all modeling approaches 

showing strong agreement in predicted results. Additional analysis performed to 

develop the interpollutant ratio uses both regional and receptor evaluations which were 

the primary models used for the 2008 PM 2.5 Plan. 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

5

 Limitations 

Both industrial direct emissions and secondary formed particulate may be both PM2.5 

and PM10. The majority of secondary particulates formed from precursor gases are in 

the PM2.5 range as are most combustion emissions from industrial stacks, however 

both secondary and stack emissions do contain particles larger than PM2.5. Regional 

modeling is more reliable for the smaller fraction due to travel distances and deposition 

rates. Large particles have much higher deposition and are much more difficult to 

replicate with a regional model. This leads to a strong technical preference for 

evaluating both emission types in terms of PM2.5 because the integration of receptor 

analysis and regional modeling for coarse particle size range up to PM10 has a much 

greater associated uncertainty. 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

6

Analyses contained in Receptor modeling 

 Factors Considered 

This modeling approach uses speciated linear modeling based on chemical mass 

balance evaluation of contributing sources with San Joaquin Valley specific 

identification of contributing source profiles, adjustments from regional modeling for the 

nonlinearity of nitrate formation, adjustments for area of influence impacts of 

contributing sources developed from back trajectory analysis of high concentration 

particulate episodes and projections of future emission inventories as developed for the 

2008 PM2.5 Plan. 

Analyses in receptor modeling that use input from regional 

modeling 

The receptor modeling analysis uses a modified projection of nitrate particulate 

formation from nitrogen oxides based upon results of regional modeling. The 

atmospheric chemistry associated with nitrate particulate formation has been 

determined to be nonlinear; while the default procedures for speciated rollback 

modeling assume a linear relationship. This adjustment has been demonstrated as 

effective in producing reliable atmospheric projections for the prior PM10 Plans. 

Extension by additional analysis 

Additional evaluations were added to results of the receptor modeling performed for the 

2008 PM2.5 Plan. Calculations determine the observed micrograms per ton of emission 

for each contributing source category that can be resolved by chemical mass balance 

modeling methods. These ten categories allow differentiation of industrial direct 

emissions of organic and elemental carbon from other sources that emit elemental and 

organic carbon. The interpollutant calculation is developed as an addition to the 

receptor analysis by calculating the ratio of emissions per ton of directly emitted 

industrial PM2.5 to the per ton ratio of secondary particulate formed from NOx and SOx 

emissions. Summary tables and issue and documentation discussion was added to the 

analysis. 

 Strengths 

Receptor modeling provides the ability to separately project the effect of different key 

sources contributing to carbon and organic carbon. This is critical for establishing the 

atmospheric relationship between industrial emissions and the observed concentrations 

due to industrial emissions. Regional modeling methods at this time do not support 

differentiation of vegetative and motor vehicle carbon contribution from the emissions 

form industrial sources. The area of influence of contributing sources was also 

considered as a factor with the methods developed by the District to incorporate the 

gridded footprint of contributing sources into the receptor analysis. While regional 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

7

models use gridded emissions, current regional modeling methods do not reveal the 

resulting area of influence of contributing sources. 

 Limitations 

Receptor modeling uses linear projections for future years and cannot account for 

equilibrium limitations that would occur if a key reaction became limited by reduced 

availability of a critical precursor due to emission reductions. The regional model was 

used to investigate this concern and did not project any unexpected changes due to 

precursor limitations. 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

8

Analyses contained in Regional modeling 

 Factors Considered 

The analysis file includes the daily modeling output representing modeled values for the 

base year 2005 and predicted values for 2014 for each of the eleven Valley sites that 

have monitoring data for evaluation of the models performance in predicting observed 

conditions. These sites are located in seven of the eight Valley counties. Madera 

County does not have monitoring site data for this comparison. 

Modeling data for all quarters of the year was provided. Due to the higher values that 

occur due to stagnation events in the fourth quarter, both industrial carbon 

concentrations and secondary particulates forming from gases are highest in the fourth 

quarter. Evaluating the interpollutant ratio for other quarters would be less reliable and 

of less significance to assisting in the reduction of high particulate concentrations. 

Modeling for lower values has higher uncertainty. Modeling atmospheric ratios when 

the air quality standard is being met are axiomatically not of value to determining offset 

requirements intended to assist in achieving compliance with the air quality standard. 

However, for consistency of analysis between sites, days when the standard was being 

met during the fourth quarter were not excluded from the interpollutant ratio analysis. 

Bakersfield fourth quarter modeled data included only eight days that were at or below 

the standard. Fresno and Visalia sites averaged twelve days; northern sites 24 days 

and the County of Kings 38 days. 

Modeling output provided data for both 2005 and 2014. While there is substantial 

emissions change projected for this period, the regional modeling evaluation does not 

project much change in the atmospheric ratios of directly emitted pollutants and 

secondary pollutants from precursor gases. This indicates that the equilibrium 

processes are not expected to encounter dramatic change due to limitation of reactions 

by scarcity of one of the reactants. This further justifies using the receptor evaluation 

determining the interpollutant ratio for 2009 through the year 2014 without further 

adjustment. If observed air quality data demonstrates a radical shift in chemistry or 

components during the next few years, such a change could indicate that a limiting 

reaction has been reached that was not projected by the model and such radical 

changes might require reassessment of the conclusion that the ratio should remain 

unchanged through 2014. 

Extension by additional analysis 

Regional modeling results prepared for the 2008 PM2.5 Plan were analyzed to extract 

fourth quarter data for all sites. The atmospheric chemistry for all counties was 

analyzed for consistency and variation. This analysis provided a determination that the 

secondary formation chemistry and component sources contributing to concentrations 

observed in the north fell within the range of values similarly determined for the 

southern four counties. Based upon examination of the components and chemistry, the 

northern counties would be expected to have an interpollutant ratio value less than the 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

9

ratio determined for Kern County but greater than the one for Tulare County. This 

establishes that the interpollutant ratio determined by receptor analysis of the southern 

four counties provides a value that is also sufficiently protective for the north. 

 Strengths 

Regional models provide equilibrium based evaluations of particulate formed from 

precursor gases and provide a regional assessment that covers the entire Valley. The 

projection of particulate formed in future years is more reliable than linear methods used 

for receptor modeling projections. 

 Limitations 

The regional model does not provide an ability to focus on industrial organic carbon 

emissions separate from other carbon sources such as motor vehicles, residential wood 

smoke, cooking and vegetative burning. Regional modeling does not provide an 

assessment method for determination of sources contributing at each site or the area of 

influence of contributing emissions. Receptor analysis provides a more focused tool for 

this aspect of the evaluation. 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

10

Results and Documentation 

SJVAPCD Interpollutant Ratio Results 

SOx for PM ratio: 1.000 ton of SOx per ton of PM 

NOx for PM ratio: 2.629 tons of NOx per ton of PM 

These ratios do not include adjustments for other regulatory 

requirements specified in provisions of District Rule 2201. 

The results of the modeling analysis developed an atmospheric interpollutant ratio for 

NOx to PM of 2.629 tons of NOx per ton of PM. This result was the most stringent ratio 

from the assessment industrial carbon emissions to secondary particulates at Kern 

County; with Fresno, Tulare and Kings counties having a lower ratio. The assessment 

of chemistry from the regional model required comparison of total carbon to secondary 

particulates and is therefore not directly useful to establish a ratio. However, the 

regional model does provide an ability to compare the general atmospheric similarity 

and compare changes in chemistry due to Plan reductions. Evaluation revealed that the 

atmospheric chemistry of San Joaquin, Stanislaus and Merced counties falls within the 

range of urban characteristics evaluated for the southern four counties; therefore the 

ratio established should be sufficiently protective of the northern four counties. 

Additionally, comparison of future year chemistry showed minimal change in pollutant 

ratio due to the projected changes in the emission inventory from implementation of the 

Plan. The SOx ratio as modeled indicates a value of less than one to one due to the 

increase in mass for conversion of SOx to a particulate by combination with other 

atmospheric compounds; however, the District has set guidelines that require at least 

one ton of an alternative pollutant for each required ton of reduction in accordance with 

District Rule 2201 Section 4.13.3. Therefore the SOx interpollutant ratio is established 

as 1.000 ton of SOx per ton of PM. These ratios do not include adjustments for other 

regulatory considerations, such as other provisions of District Rule 2201. 

A guide to the key technical topics and the reference material relevant to that topic is 

found on the next page. References from the 2008 PM2.5 Plan may be obtained by 

requesting a copy of that document and its appendices or by downloading the document 

from http://www.valleyair.org/Air_Quality_Plans/AQ_Final_Adopted_PM25_2008.htm. 

References in Italics are spreadsheets included in the interpollutant analysis file “09 

Interpollutant Ratio Final 032909.xls” which includes 36 worksheets of receptor 

modeling information from the 2008 PM2.5 Plan, 11 modified and additional 

spreadsheets for this analysis and two spreadsheets of regional model daily output. 

This file is generally formatted for printing with the exception of the two spreadsheets 

containing the regional model output “Model-Daily Annual” and “Model-Daily Q4” which 

are over 300 pages of raw unformatted model output files. The remainder of the file is 

formatted to print at approximately 100 pages. This file will be made available on 

request but is not currently posted for download. 
DEVELOPMENT OF THE INTERPOLLUTANT RATIO

11

Interpollutant Ratio Issues & Documentation 

TOPIC Reference 

1 Reason for using PM2.5 for establishing the substitution relationship 

between direct emitted carbon PM and secondary nitrate and sulfate 

PM: consistency of relationship between secondary particulates and 

industrial direct carbon combustion emissions.

2008 PM2.5 Plan, 

Sections 3.3.2 

through 3.4.2 

2 Reason for using 4th Quarter analysis: Highest PM2.5 for all sites. DV Qtrs 

3 Reason for using analysis of southern SJV sites to apply to regional 

interpollutant ratio: Northern site chemistry ratios are within the range of 

southern SJV ratios. Peak ratio will be protective for all SJV counties.

Q4 Model Pivot, 

Model-site chem, 

Model-Daily Q4 

4 Reason for using combined results of receptor and regional model: 

Receptor model provides breakdown of different carbon sources to isolate 

connection between industrial emissions and secondary PM. 

2008 PM2.5 Plan, 

Appendix F 

Regional model provides atmospheric information concerning the northern 

SJV not available from receptor analysis. 

2008 PM2.5 Plan, 

Appendix G 

5 Most significant contributions of receptor evaluation: Separation of 

industrial emissions from other source types. Area of influence evaluation for 

contributing sources.

2008 PM2.5 Plan, 

Appendix F 

6 Most significant contributions of regional model: Scientific equilibrium 

methods for atmospheric chemistry projections for 2014. Receptor technique 

is limited to linear methods.

2008 PM2.5 Plan, 

Appendix G 

7 Common area of influence adjustments used for all receptor 

evaluations: 

Geologic & Construction, Tire and Brake Wear, Vegetative Burning - 

contribution extends from more than just the urban area (L2) 

Mobile exhaust (primary), Organic Carbon (Industrial) primary, Unassigned - 

contribution extends from more than larger area, subregional (L3) 

Secondary particulates from carbon sources are dominated by the local area 

with some contribution from the surrounding area (average of L1 and L2) 

Marine emissions not found present in CMB modeling for this analysis. 

Modeling 

evaluation by 

J. W. Sweet 

February 2009 

Reflected in IPR 

County 2000-2009

worksheets 

8 Variations to reflect secondary area of influence specific to location: 

Fresno: Evaluation shows extremely strong urban signature (L1) for 

secondary sources 

Kern: Evaluation shows a strong urban signature mixed with emissions from 

the surrounding industrial areas (average L1 and L2) for both carbon and 

secondary sources 

Kings and Tulare: Prior evaluation has show a shared metropolitan 

contribution area (L2) 

Modeling 

evaluation by 

J. W. Sweet 

February 2009 

Reflected in IPR 

County 2000-2009

worksheets 

9 Reasons for using 2009 Interpollutant Ratio Projection:

2009 Interpollutant ratio is consistent with current emissions inventories 2008 PM2.5 Plan 

Regional modeling does not show a significant change in chemical 

relationships through 2014. Q4 Model Pivot 

10 Reason for using SOx Interpollutant Ratio at 1.000: A minimum offset 

ratio is established as 1.000 to 1.000 consistent with prior District policy and 

procedure for interpollutant offsets.

District Rule 2201 

Section 4.13.3