SAPRC Atmospheric Chemical Mechanisms and VOC Reactivity Scales

W.P.L. Carter
Air Pollution Research Center and
College of Engineering Center for Environmental Research and Technology
University of California, Riverside

Phone: 951 781-5797
Mail: CE-CERT, University of California; Riverside, CA 92521, USA
Email: carter@cert.ucr.edu
URL: http://www.cert.ucr.edu/~carter

Date last updated
Item
September 14, 2013  This page
February 22, 2013Revised version of SAPRC-11 (Gas phase only)
May 21, 2012Preliminary SAPRC-11 Aromatics and Aromatic SOA mechanisms
May 21, 2012 Mechanism Documentation
January 25, 2010 SAPRC-07 mechanism
January 25, 2010 Condensed versions of SAPRC-07
January 25, 2010"Toxics" versions of SAPRC-07
September 14, 2013 VOC reactivity scales (SAPRC-07) (May 11, 2011 for most compounds)
January 25, 2010 Mechanism implementation files for CMAQ
June 21, 2012
Mechanism implementation files for SAPRC software
December 15, 2011
Emissions assignments (see Speciation Database page)

Please notify me if you want to be added to the list of people to be informed by email if there are significant updates or additions to the SAPRC mechanisms, reactivity scales or web pages. (You are already on this list if you received my email dated May 21, 2012 concerning the SAPRC-11 mechanisms. Notify me if you would like to be removed.)

Click here for the files implementing this mechanism for CMAQ and SAPRC modeling systems. Click here for files and programs implementing the mechanism in the SAPRC box and chamber modeling software

SAPRC-11 Aromatics and Aromatic SOA Mechanisms. A new version of the SAPRC aromatics mechanism, designated SAPRC-11, has been developed and preliminary documentation is now available. The updates are restricted to aromatic chemistry and mechanisms for non-aromatic species are the same as SAPRC-07. Note that files implementing this version of the mechanism in models are not yet available, and it is recommended that modelers continue to use SAPRC-07 until the ongoing project to comprehensively update SAPRC-07 is completed. The available documentation is summarized below.

The updates to the gas-phase mechanism, and its performance in simulating ozone formation in environmental chamber experiments, is documented in the report "Development of Revised SAPRC Aromatics Mechanisms," by W. P. L. Carter and Gookyoung Heo (click here for abstract). This is available in PDF format (saprc11.pdf) and is dated April 12, 2012.

An extensive series of environmental chamber experiments to measure secondary organic aerosol (SOA) formation from aromatics have been completed and the results were used to develop a version of the SAPRC-11 aromatics mechanism to predict SOA formation from aromatics This is documented in the report "SOA Formation: Chamber Study and Model Development," by W. P. L. Carter, Gookyoung Heo, David R. Cocker III, and Shunsuke Nakao (click here for abstract). This is available in PDF format (pmchrpt.pdf) and is dated May 21, 2012.

Note: In the process of preparing a manuscript describing the gas-phase SAPRC-11 aromatics mechanism, several corrections and modifications were made to the gas-phase mechanim.  These are described in a manuscript that has been submitted to Atmospheric Environment and is avaible upon request. The files implementing the gas-phase mechanism, which are available at the SAPRC mechanism files download page, incorporates this version of SAPRC-11, which is different than the versions documented in the 2012 reports of Carter and Heo referenced above.

A revised version of the aromatic SOA mechanism that is consistent with the revised SAPRC-11 gas-phase mechanism is in preparation.

SAPRC-07 Mechanism. The SAPRC-07 mechanism was finalized in 2010 and is the latest stable version of the SAPRC mechanisms and was used to develop the current SAPRC reactivity scale. Information concerning its available documentation and associated files is summarized below.

Peer reviewed journal articles documenting the full and condensed SAPRC-07 mechanism have been published, and are as follows: W. P. L. Carter, "Development of the SAPRC-07 Chemical Mechanism," Atmospheric Environment, 44, 5324-5335 (2010) and W. P. L. Carter, "Development of a Condensed SAPRC-07 Chemical Mechanism, Atmospheric Environment, 44, 5336-5345 (2010).

The final report documenting the mechanism, its evaluation, and the updated reactivity scales is available in Microsoft Word (saprc07.doc) and PDF (saprc07.pdf) formats. The current version is dated January 27, 2010.

Tables in the Appendices to the report Excel format (saprc07.xls). This includes the large tables not in the main body of the report, the VOC reactivity tabulation (MIR and other scales) and uncertainty classifications in Table B-1 of the report, and other tables. The current version is dated May 11, 2011.

The table with the MIR and other reactivity data is also available in a separate Excel file (scales07.xls) that contains only this table and the associated footnotes, with a few updates as indicated in a sheet with notes for the table. This includes the data in (saprc07.xls) that may be more useful for those only interested in the reactivity data, and is also more up-to-date. It also contains reactivity values for individual city-specific MIR, MOIR, and EBIR scenarios that are not in saprc07.xls. It includes new VOCs added for the 2009-2010 MIR update discussed in the MIR10 report discussed below. The current version is dated September 14, 2013. The only change relative to the version dated March 31, 2010 concerns the reactivity of ethyl methyl ketone oxime (EMKO), which was revised based on new data in a recent report to the CARB. The only change since then is the addition of several new VOCs to the listing, the deletion of a redundant VOC category, and the addition of a listing of the changes made since the May 11, 2011 version as part of the notes given with the table.

A report discussing the update to the MIR values resulting from the use of the SAPRC-07 mechanism and describing the revised method used to calculate MIR values for the 24 hydrocarbon "bins" used in some CARB reactivity-based regulations is available in Microsoft Word (MIR10.doc) and PDF (MIR10.pdf) formats. The spreadsheet (HCcalc.xls) used to derive the compositions used to calculate the reactivities of the 24 hydrocarbon bins, which is referenced in the report, is also available. This can also be used to estimate compositions and reactivities of other hydrocarbon mixtures given type distributions and boiling point ranges. The current versions of the spreadsheet and report are Jaunary 28, 2010. They incorporate the updates in the SAPRC-07 mechanism and reactivity scale as of this date, and should replace earlier versions.

The CARB contracted Merched Azzi, Richard Derwent, Robert Harley, and William Stockwell to conduct peer reviews of the SAPRC-07 mechanism.  These reviews are available at the CARB RSAC website. My response to these reviews is available in Microsoft word (RespRev.doc) and PDF (RespRev.pdf) formats. This document is dated March 20, 2009.

The final report documenting the condensed versions of the SAPRC-07 mechanism is available. Available in Microsoft Word (csaprc07.doc) and PDF (csaprc07.pdf) formats. The report, which was revised to incorporate recent updates to the base mechanism,  is dated January 28, 2010 and supersedes earlier versions. The SAPRC-07 condensed mechanisms have been updated to be consistent with the current (1/25/10) version of SAPRC-07 and the files implementing these updated mechanisms are available on the "SAPRC-07 Chemical Mechanism and Emissions Speciation Files for CMAQ" page. The revised versions after July 13, 2009, were modified to retain methane, so it can be used for cleaner air simulations.

The maximum ozone impacts of NO, NO2, and HONO, which have their highest positive impacts on ozone under very low NOx conditions, have been added to the reactivity tabulation in scales07.xls. These are more appropriate to use than MIR values for these NOx species for applications, such as life cycle analyses, where maximum ground-level ozone impacts of NOx are compared to those for VOCs. A report documenting the derivation of these NOx Maximum Incremental Reactivity (NMIR) values is available in Microsoft Word (NOxMIR.doc) and PDF (NOxMIR.pdf) formats. This report has not been updated to the current version of the mechanism, but the NMIR the values tabulated in scales07.xls have been updated.

A version of the distributed files and programs have been prepared, including files for the various versions of the SAPRC-07 mechanism (including condensed versions) and files to conduct chamber simulations and test calculations. This contains the corrected version of the mechanism and should replace any versions of the mechanism downloaded prior to January 25, 2010. Some of the programs have been updated as well. See the SAPRC mechanism files distribution page to download the files and for more information. 

(Note: if these files open in your browser, use "save as" to save them as regular .DOC or .XLS files.)

Changes and additions to mechanism, reactivity scales, distributed programs, or documentation:

2/22/13: The SAPRC-11 gas-phase aromatics mechanism was revised and the files implementing this mechanism at the SAPRC mechanism files download page correspond to this version. This is described in a manuscript that has been submitted to Atmospheric Environment and is avaible upon request.

6/21/12: Major revisions have been made to the distributed SAPRC software , as described in SAPRCfiles.PDF. All programs are now compiled with the public domain GNU Fortran compiler fortran, and the method used to

5/21/12:
A new version of the SAPRC aromatics mechanism, designated SAPRC-11, has been developed and preliminary documentation is available in two reports to the CARB. The updates to the gas-phase mechanism is documented in the report "Development of Revised SAPRC Aromatics Mechanisms," by W.P.L. Carter and Gookyoung Heo (saprc11.pdf). The development of a version to predict secondary organic aerosol formation from aromatics is documented in the report SOA Formation: Chamber Study and Model Development,” by W.P.L. Carter,  Gookyoung Heo, David R. Cocker III, and Shunsuke Nakao (pmchrpt.pdf). The latter report also documents the results of an extensive series of environmental chamber experiments on aromatic SOA formation.

5/11/11
: The reactivity scale in scales07.xls and saprc07.xls has been updated to include new reactivity values for ethyl methyl ketone oxime (EMKO), which was revised based on new data in a recent report to the CARB. The reactivity values for all other VOCs are unchanged.

2/4/11
: SAPRC-07 box modeling programs and files updated and programs and files needed to do reactivity scale calculations were added. See SAPRCfiles.pdf for a discussion of the files and their installation and use.

4/20/10
: Duplicate entries of several perfluoro ethers, with incorrect MIR and other reactivity values, have been deleted from the reactivity tabulations in Table B-1 in saprc07.xls and in scales07.xls. The deleted entries, with incorrect reactivity values, were for "methyl-nonafluoro-butyl ether", "methyl-nonafluoro-isobutyl ether", "ethyl nonafluorobutyl ether", and "ethyl nonafluoroisobutyl ether". These are the same compounds as methoxy-perfluoro-n-butane, methoxy-perfluoro-isobutane, ethoxy-perfluoro-n-butane, and ethoxy-perfluoro-isobutane, which are also on the reactivity list but with the correct reactivity values. The correction to the table was made on 3/31/10 but not uploaded to the website until 4/20/10. Note that the reactivity tabulations in saprc07.docsaprc07.pdf, MIR10.doc, MIR10.pdf, and in the supplementary material for the Atmospheric Environment journal article have not been corrected and still contain these erroneous duplicate entries.

2/2/10: Web pages distributing the SAPRC-07 mechanism files and the SAPRC modeling software were reorganized and a spreadsheet giving the calculated photolysis rates for the solar actinic fluxes used for the reactivity scale calculations is now included in the distribution if mechanism files.

1/28/10
: An error in the files implementing the mechanism that caused in the rate constant for the O1D+H2O reaction to be low by ~18% was found and corrected. This resulted in slightly increased O3 predictions in ambient simulations, though still lower than calculated using SAPRC-99, and also resulted in MIR values being somewhat closer to those for SAPRC-99. The effects of this change on the chamber simulations used to evaluate the mechanism are negligible. All versions of the mechanism are affected. The mechanism documentation reports, reactivity scales, and mechanism implementation files have been updated to incorporate this correction.

1/22/10
: A minor error in the procedure used to output.MEC files where the "N" parameter in falloff reactions was not being given when it was different than 1.0 was corrected. This affects only the files for CMAQ and not the calculations using the SAPRC software, which are the basis of the calculations and reactivity tables in the reports.

1/20/10: The report to the CARB documenting the MIR and hydrocarbon bin MIR update has been updated to the current mechanism version and renamed from MIR09 to MIR10. The spreadsheet HCcalc.xls for calculating hydrocarbon bin and mixture reactivities has also been updated.

1/15/10:
A number of errors were found in the base SAPRC-07 mechanism and corrected, and the reactivity scales, documentation, and files have been updated accordingly. A number of edits were also made to the documentation not only to correct the errors but to make editorial changes and corrections noticed as part of preparing journal articles documenting the mechanisms. The corrections and updates are described in Appendix E in saprc07.doc or saprc07.pdf. Most of the errors concern low NOx reactions that do not significantly affect O3 predictions, though an error was found that affected MIR values for tertiary amines. The changes affect all versions of the mechanism, and all files and reports downloaded prior to this date should be replaced by the current versions.

11/13/09
: Minor corrections made to "C" versions of SAPRC07 and SAPRC07T. (This is the version that uses explicit reactions for peroxy radical operators to be consistent with most airshed model software. The correction involved adding 0.5 PROD to reactions of the xPROD operator with MEO2, RO2C, and RO2XC, for consistency with the treatment of these reactions in the "B" version. The effect on most model simulations should be negligible.) See distributions of mechanism files for CMAQ and the SAPRC software.

11/12/09: Input and data files for simulations of chamber experiments for modeling using SAPRC software have been corrected and updated. A few experiments had errors in model simulation input files that were updated, and some experimental data files are missing. Input files and chamber data files should be current and complete for all experiments listed in Table C-1 in saprc07.xls.

9/9/09 and 8/26/09
: The report documenting the MIR update (MIR09.pdf, now renamed MIR10.pdf) has been updated and several VOCs and mixtures have been added. These new VOCs have also been added to scales07.xls

7/28/09
: Files implementing SAPRC-07A, the otherwise uncondensed version of the mechanism using the SAPRC-99 peroxy radical operators, have been added to the files implementing the mechanism in CMAQ and the SAPRC software.

7/13/09:
The condensed mechanism was revised to retain methane so it can be used in cleaner air simulations. The condensed mechanism documentation report (csaprc07.doc and csaprc07.pdf) was revised accordingly, and several corrections were made to the report. In addition, several corrections and updates were made to the files implementing the mechanism for SAPRC software.

6/22/09:
The report to the CARB describing the update to the MIR scale and bin calculation method for their regulatory purposes (MIR09.pdf, now renamed MIR10.pdf) was revised. This included revisions to the methods used to calculate the hydrocarbon Bin MIR's, so the reactivity and composition tabulations in the SAPRC-07 documentation report (saprc07.pdf or saprc07.doc and saprc07.xls) were revised accordingly.

6/8/09:
The report and reactivity tabulations have been updated to include several new compounds and minor additions have been made to the mechanism documentation tabulations for a few other compounds.

4/9/09: The files implementing the SAPRC-07 mechanisms on SAPRC software, available on the SAPRC mechanism files page, have and the condensed SAPRC-07 mechanism report, been updated to be consistent with the current mechanisms as of this date.

4/8/09: The condensed and "toxics" versions of SAPRC-07 have been revised to be consistent with the 3/19/09 version of SAPRC-07, and the files implementing the various versions of SAPRC-07 have been prepared and are available on the "SAPRC-07 Chemical Mechanism and Emissions Speciation Files for CMAQ" page. The report documenting condensed SAPRC-07 still and the files implementing the mechanism in the SAPRC modeling software still need to be updated. Please contact me if you need the updated versions sooner.

3/19/09: Changes have been made to the base SAPRC-07 mechanism to correct some errors found in the previous versions. The documentation report (saprc07.doc and saprc07.pdf) and the reactivity scales tabulations (saprc07.xls and scales07.xls) have been updated accordingly. The changes are summarized in Appendix E of the documentation report. (The condensed and "toxics" versions of SAPRC-07 and the available files not implementing the mechanisms were not updated until 4/8/09 -- see above.) These changes do not affect the emissions speciation assignments.

12/17/08: The final report for the condensed version of SAPRC-07 has been finalized and made available. Available in Microsoft Word (csaprc07.doc) and PDF (csaprc07.pdf) formats. Other than being finalized, the version is dated July 4, 2008 was unchanged.

7/7/08: Several corrections have been made to the mechanism and the documentation, reactivity scales, and mechanism files have been updated accordingly.

7/7/08: Files for the preliminary "toxics" version of of SAPRC-07, designated SAPRC07T have been added. This is being developed for the EPA for implementation in CMAQ. See the readme file for the current SAPRC-07T distribution.

6/3/08: The CARB hydrocarbon bins have been added to the reactivity tabulation in Table B-2 (scales07.xls). The compositions used to derive the reactivities of the bins have been added to Table B-10, which is included in saprc07.xls. Footnotes to Table B-2 references how these bin compositions were derived.

5/28/08: A number of corrections were made to the mechanism, the documentation report was updated, and the reactivity scales were recalculated. Any versions of the documentation, mechanism files, or reactivity tabulations uploaded prior to this date need to be replaced by the current versions. See Appendix E in the documentation report (e.g., saprc07.pdf). The changes in reactivity values compared to the 12/31/07 version were small except for 1,1-dichloroethene, where there was an error in the rate constant that was corrected.

1/22/08: The maximum ozone impacts of NO, NO2, and HONO, which have their highest positive impacts on ozone under very low NOx conditions, have been added to the reactivity tabulation in scales07.xls. A report documenting the derivation of these values is available in Microsoft Word (NOxMIR.doc) and PDF (NOxMIR.pdf) formats. Also, the tabulations in scales07.xls also give the reactivities in the individual MIR, MOIR and EBIR as well as base case scenarios.

12/31/07. Documentation report and mechanism and reactivity tabulations updated to incorporate results of recent studies of the mechanism of methyl iodide (Carter, 2007) and of amines and several other consumer product VOCs (Carter, report on CARB Contract 06-408,  in preparation). The mechanism and reactivity values for methyl iodide have been added, the mechanisms and reactivity values have changed for all amines, and several consumer product VOC have been added. The amine reactivities in previous tabulations should not be used. Reactivities have not changed for any other previously tabulated compounds.

6/28/07. Error in Table B-1 in saprc07.xls and scales07.xls corrected. The previous version had incorrect standard deviations for the "Base" reactivities.

8/31/07. A number of errors in the report have been corrected when preparing the final (8/31/07) version. See the summary of revisions.

8/31/07. The mechanism as listed in the June 15 version of the report had two errors. Reaction BR08 should be changed from "RO2C + HO2 = HO2" "RO2C + HO2 =" and reaction BR13 should be changed from "RO2XC + HO2 = HO2" to "RO2XC + HO2 =". This has been corrected in the current (8/31) version of the report and reactivity scales. The change has only small effects on O3 and reactivity scales, but a non-negligible effect on calculations of HO2 in low NOx scenarios.

A distribution of the files and programs used in the evaluation against the chamber data and other test calculations is now available.  Go to files.htm for additional information and to download the files. Note that the documentation is only very preliminary and incomplete, and this has not been fully tested. The mechanism and programs are current as of January 15, 2010. If you need updated or additional files and information, please contact me.


Related Links
  • Carter main web page
  • Current version of files implementing SAPRC-07 for CMAQ and other modeling software systems.
  • Current version of the programs and files implementing the mechanisms using the SAPRC box and chamber modeling software.
  • Emissions speciation project containing assignments of emissions categories to model species in SAPRC and other mechanisms
  • The following links give information about SAPRC-99
  • SAPRC-99 mechanism documentation report
  • Latest VOC Reactivity tabulations for SAPRC-99 Mechanism
  • Files implementing SAPRC-99 Chemical Mechanism and Associated Software
  • Current Information on Emissions Speciation Database Work


  • William P. L. Carter
    Research Chemist
    Air Pollution Research Center and
    College of Engineering, Center for Environmental Research and Technology
    University of California, Riverside, CA, USA
    Mailing Address: CE-CERT, University of California, Riverside CA 92521
    Street Address: CE-CERT, 1084 Columbia Ave, Riverside, CA 92507
    Phone: (951) 788-8425
    FAX: (951) 781-5790
    E-mail: carter@cert.ucr.edu
    URL: http://www.cert.ucr.edu/~carter