Chemical Mechanism Assignment Database for Organic Compound Emissions

1. Chemical Mechanism Assignment Database for Organic Compound Emissions Overview • Background, Objectives and History of Database • Components of the speciation assignment system • Current status and problems • Discussion and recommendations William P. L. Carter University of California, Riverside, CA October 29, 2014 Model Species Assignment Database

2. Background • Over 1000 types of organic compounds are emitted into the atmosphere, each having widely varying effects on air quality. • These are usually represented in models using lumped chemical mechanisms with very limited numbers of model species. • How best to assign model species to chemical categories used in current emissions speciation profiles is often not obvious. • Many categories refer to mixtures of varying specificity • Many compounds do not have model species designed specifically to represent them in most mechanisms • Modelers usually only have direct assignments of model species to profile mixtures, with no other information or documentation. • Many of these were found to have inappropriate, questionable, or inconsistent assignments. • Difficulty with updating emissions speciation assignments has inhibited implementation of new or more detailed mechanisms. Model Species Assignment Database

3. Emissions Speciation Databases or Models Anthropogenic Speciation Databases • Several separately-maintained databases contain emissions speciation profile composition information, e.g.: • Speciate 4.4: Maintained by U.S. EPA. ~1700 categories • California and Texas maintain separate databases using different codes and categories in many cases • Many categories refer to mixtures and some are not well defined Biogenic Models • BEIS 3 outputs 32 compound and 3 mixture categories. • Undocumented model species assignments are available for a few mechanisms, but have errors and inconsistencies • MEGAN 2 outputs 13 compound and 5 mixture categories. • Undocumented model species assignments for a few mechanisms are built into the model code Model Species Assignment Database

4. Chemical Mechanismsfor which Assignments were Made Model Species Assignment Database

5. Objectives of theSpeciation Database Project • Consistent assignments are made for the major chemical mechanisms and speciation databases or models; • Model species are assigned to chemical compounds only and are consistent with intentions of the mechanism developers; • Model species assigned to mixture categories are based on estimated compositions and assignments for compounds; • Procedures are available to represent unknowns without bias; • The database can be updated as new mechanisms or emissions speciation databases and models are developed; • The database is documented to give sources of assignments and so others can add mechanisms or categories; and • The database and documentation are available online. Develop a database of model species assignments to chemical categories in speciation profiles or emissions models such that: Model Species Assignment Database

6. History of the Speciation Database Project • 2001-2: The American Chemistry Council initiated this project for the Reactivity Research Working Group (RRWG) because emissions processing was inhibiting modeling VOC reactivity. • 2002: First version of the systems became available online at http://www.cert.ucr.edu/~carter/emitdb. (Still available there.) • 2002-13: Database continuously updated to add new mechanisms and profile categorizations (e.g., Speciate) and to correct errors. • Used for assignment files distributed with CMAQ for SAPRC and other mechanisms and used in the Speciation Tool • 2014: Structure of database and programs revised and simplified. Changes allow assignments for very large mechanisms. • 2014: Assignments for biogenic categories output by BEIS 3 and MEGAN 2 were added • 2014: Documentation updated and is available online. Model Species Assignment Database

7. Current Structure of the Database Assignments are implemented in twoMicrosoft Excel files: • SpecDB.xls (previously named EmitDB.xls) contains: • Type and profile database codes for all categories; • Model species assignments and other information for the chemical compound categories; • Estimated mixture compositions (where possible) and footnotes documenting the estimates; and • Macros to process assignments and output them in files. • MechDB.xls (new) has sheets listing model species and their properties for the 12 currently supported mechanisms. Fortran programs are included to use the assignments to make model species assignments for profiles in selected databases Files, Programs, and documentation are available online at http://cert.ucr.edu/~carter/emitdb Model Species Assignment Database

8. Types of Chemical Categoriesin the Database * Fraction in total of all Speciate 4.4 profiles, each weighted equally ** Fraction in total Anthropogenic U.S. Emissions mixture (2005 inventory) Model Species Assignment Database

9. Distributions of Numbers of Compoundsof Various Chemical Types Note: Multifunctional compounds may be counted more than once Model Species Assignment Database

10. Derivation of Model Species Assignments SAPRC mechanisms • All assignments are made by the mechanism developer. Carbon Bond (CB) mechanisms • Most assignments taken from files provided by Greg Yarwood, the principal maintainer and implementer of these mechanisms. • Assignments for new compounds made by analogy with those provided by Yarwood. Footnotes indicate these cases. • Total CB species carbon numbers checked for all compounds. RADM and RACM mechanisms • General procedures and methods for most types of compounds were approved by Bill Stockwell and/or Wendy Goliff. MCM • Only compounds represented explicitly in MCM were assigned. • Compound and model species names were provided by Yi Ying, who implemented the MCM in CMAQ. Model Species Assignment Database

11. Mass Fractions of Representative Total Profile and Emissions MixturesAssigned Model Species * Representative mixtures used: [a] Total for all Speciate 4.4 profiles, each weighted equally [b] Total anthropogenic U.S. Emissions from the 2005ah toxics inventory [c] Annual total organic emissions for California statewide for 2010 Model Species Assignment Database

12. Changes in Model Species Assignmentsfor Representative Biogenic Mixtures [a] Derived for the global annual total for year 2000 calculated using MEGAN 2.1 in CLM4 using Megan-2 built-in assignments. [b] Derived for averaged biogenic emissions for eastern U.S. for 8/28 - 9/15/06 calculated by BEIS 3 using the EPA-distributed GSPRO file Model Species Assignment Database

13. Advantages of Use of Speciation System Use of this system improves the scientific integrity of models • Previously used speciation assignments found to have errors; • System makes consistent assignments for different compounds, mixtures, mechanisms, emissions databases, and models; • Assignments better reflect intentions of mechanism developers; • Assumptions and estimates about mixture compositions are completely separated from chemical mechanism issues; and • Better documentation of assumptions and assignments. Use of this system has advantages to modelers • Output can be used in existing speciation processing systems (SMOKE, Speciation tool) and can easily be adapted to others; • Easier to change lumping or update or add mechanisms; • Easier to update or add emissions profile databases; and • Files, programs, and documentation are available online. Model Species Assignment Database

14. Limitations and Work Needed • The current system does not support speciating PM emissions. • Volatility judgments are arbitrary and need expert review • Mixture assignments need to be reviewed and updated by emissions analysis experts. • Model species assignments to compounds need to be independently reviewed by chemical mechanism experts. • Not all mechanisms are implemented or fully implemented, e.g. • No assignments for the latest version of Carbon Bond (CB6) • No MCM assignments for emitted non-MCM compounds • Better database software may improve implementation • Need plan to support and continue system into the future • Maintaining and updating current system is now primarily an unfunded volunteer project • Person now maintaining system may soon completely retire Model Species Assignment Database

15. Recommendations • Continue improving profiles. Minimize use of mixture categories or recommend compositions; remove poorly defined categories. • Improve ability of biogenic models to incorporate model species assignments from the speciation database. • Develop means and protocols so emissions profile and mechanism developers can directly update the system. • Develop a funding mechanism to maintain and improve the system. (Cost small compared to other model components). • Identify persons or institutions to continue maintaining system. • Add a model species assignment system to the list of CMAS-supported products • This will encourage its more widespread use among modelers and model and database developers • Improved the chance for future maintenance and support Model Species Assignment Database

16. Acknowledgements Funding • American Chemical Council: Initial development • California ARB: Support for SAPRC updates and incorporating California profile database • U.S. EPA: periodically covered consulting costs to add mechanisms and support use with the Speciation Tool • University of California Retirement System: Primary source of support since 2005 Providing data and helpful discussions • Zac Adelman: Collaboration with initial development of system • Greg Yarwood, Bill Stockwell, Wendy Goliff: Assistance with model species assignments for CB, RADM, RACM mechanisms • Qi Ying (TAMU): Model species information for MCM • Deborah Luecken (EPA): Support and U.S. Emissions data • Paul Allen and Wenli Yang (CARB): California profile data Model Species Assignment Database

17. Thank You Database, files, programs and documentation available at http://www.cert.ucr.edu/~carter/emitdb Model Species Assignment Database

18. Numbers of Organic Compounds Contributing to total Mass and Reactivityin Anthropogenic Emissions in the U.S. Total anthropogenic U.S. Emissions based on the 2005ah toxics inventory Model Species Assignment Database

19. Examples of CurrentSpeciation Profile Databases and Models * Categories not used in any Speciate 4.4 VOC or TOG profile are not counted ** BEIS was developed by the EPA, but all links to it on the EPA’s web remain broken, despite being notified of the problem in February, 2014 Model Species Assignment Database

20. Information Given for Chemical Compounds All Compounds • Master List ID code and compound name(s) • Atom numbers and molecular weight calculated from them • Flag indicating whether the compound is judged to be volatile Most Compounds • CAS number if known and well defined • Codes for various types of chemical groups (aids assignments) • Model species assignments for all the lumped mechanisms Many compounds (where applicable) • Model species for explicit mechanism (MCM, detailed SAPRC) • Structure used by the SAPRC mechanism generation system Some compounds • Flag indicating that the compound is EPA exempt (“non VOC”) • Comments on assignments in a few special cases Model Species Assignment Database

21. Information Given for Other Categories All Categories • Master List ID code and category description (CAS no not used) • Code giving type of category (speciated, unspeciated volatile, unspeciated nonvolatile, other – see below) Speciated Mixture Categories • Mass fractions and ID codes for all components (compounds or other previously-defined speciated mixtures) • Code giving subjective assessment of quality of composition • References and notes documenting composition assignments Other Categories • Flag indicating whether this is to be treated as volatile • Code indicating type of category: unspeciated mixture; structure of components uncertain; poorly defined or inappropriate; or not yet classified because they are insignificant in all profiles Model Species Assignment Database

22. Treatment of Unknown,Non-Volatile and Inert Mass Three options for treating unknown or unassigned mass: • Do not process (i.e., ignore) such mass. This is equivalent to assuming it is unreactive (not recommended – introduces bias); • Pass “UNKN” or “NOASN” model species to the model to represent these on mass (not molar) basis; or • Represent this mass using “Unknown” or “Unassigned” mixtures included in the database for this purpose (recommended). Non-Volatile mass • Currently represented by an “NVOL” model species on mass (not molar) basis for all mechanisms. Unreactive mass (non-Carbon Bond mechanisms) • Represented by “NROG” on a mass (not molar) basis. • Not needed for Carbon Bond mechanisms because they have the “NR” model species to represent unreactive carbon. Model Species Assignment Database

23. Files Output by Macros in SpecDB.xlsfor preparing GSPRO files for SMOKE • The database ID, name, molecular weight, carbon number and flag indicating VOC exemption is given for all compounds; • Moles of model species per mole of compound is given for compounds with model species assignments * • Mass of compounds not assigned model species are assigned the special species “NOASN” (or code=“U” for CB mech’s) * • Mass of compounds judged to be nonvolatile are assigned the special species “NVOL” (or code=“N” for CB mech’s) * • Mass of compounds assigned as unreactive in lumped-molecule (non-CB) mechanisms are assigned the special species “NROG” ** 1. Files with model species assignment data (one per mechanism). Following given for each chemical compound in database: * Same compounds for all lumped mechanisms ** Varies with mechanism. Not used for CB mech’s Model Species Assignment Database

24. Files Output by Macros in SpecDB.xlsfor preparing GSPRO files for SMOKE(continued) • The first field gives the “Master List” category ID in the database • For compounds or known mixtures, the 2nd field gives a compound ID and the 3rd field gives the mass fraction of the compound. • For compounds the 1st and 2nd fields are the same and the 3rd is 1. • Multiple records are used for mixtures of more than 1 compound. • For unspeciated categories judged to be volatile, the 2nd field gives the code “UNKNOWN” and the 3rd gives the mass fraction of 1. • For unspeciated categories judged to be non-volatile, the 2nd field gives the code “NONVOL” and the 3rd gives the mass fraction of 1. 2. File with mixture and other category assignment data. Contains records with three data fields for each category in the database: 3. Files mapping chemical category codes used in emissions databases or models to master speciation database categories. Model Species Assignment Database

25. Programs for Preparing GSPRO files for use by SMOKE or Other Emissions Systems ProfPre program (run for each categorization system) • Converts mass of speciation categories to mass of individual chemical compounds, “UNKNOWN”, or “NONVOL”. ProfAsn program (run for each mechanism and categorizaation) • Creates the GSPRO files for specified mechanisms and speciation categorization system. • Program inputs determine how unknown or unassigned mass is to be assigned model species (or not). GSPRO files contain data to assign moles of model species per unit mass of profile or emissions model categories. One such file for each mechanism and speciation categorization system. Instructions, examples, and source files are provided. Programs can be compiled using the freely available Gfortran compiler. Model Species Assignment Database

26. Files Output by SpecDB.xls for Emissions Processing using the “Speciation Tool” • A file listing the supported chemical mechanisms; • A file listing model species for all mechanisms; • A file with the model species assignments (mole basis) for each Speciate 4 category and supported mechanism; and • The full “Species Table” file with information on all Speciate 4 categories. Molecular weights for mixture categories depend on assumed compositions for correct mass-to-mole conversions. The “Speciation Tool” was developed for the EPA for processing emissions with speciation profiles using Speciate 4 categories A macro in SpecDB.xls output the four CSV files that this system reads to properly obtain model species assignments, as follows: The macro has options to determine how unknown or unassigned mass are to be assigned model species (or not) Model Species Assignment Database

27. Total SAPRC-07 and CB05 Model Species Assignments for the U.S. Emissions Mixture Model Species Assignment Database

28. Assignments Causing Differences forSimilar SAPRC and CB05 Model Species Model Species Assignment Database

29. 1 – Sum (mass fractions of exempt compounds) 1 VOC-to-TOG factor = Treatment of VOC-to-TOG Factors • Some emissions databases may exclude mass of VOC-exempt compounds (e.g., ethane, acetone) from emissions totals. • These mass emissions must be multiplied by VOC-to-TOG factors for the profiles used to obtain total mass for speciation. • The database flags VOC-exempt compounds and program outputs include VOC-exempt mass fractions for the profiles. • However, VOC emissions databases may not exclude mass from recently exempted compounds, so VOC-to-TOG factors calculated using this system will be too high in these cases. • Use of old factors would be better in these cases. • The practice of excluding mass of VOC-exempt compounds in reported emissions needs to be phased out. Model Species Assignment Database

30. Mass Contributions of Compound Typesin the Total U.S. Emissions Mixture Note: Bifunctional compounds can be counted twice Model Species Assignment Database

31. Mass Contributions of Compound Typesin the Total California Emissions Mixture Note: Bifunctional compounds can be counted twice Model Species Assignment Database

32. Mass Contributions of Compound Typesin the Total Asia Emissions Mixture Note: Bifunctional compounds can be counted twice Model Species Assignment Database

33. Distribution of How Carbons in CB05 “PAR”in the Total U.S. Emissions MixtureAre Represented by SAPRC-07 Species Model Species Assignment Database