Integration of Criteria and Toxic Pollutants in SMOKE

1. Integration of Criteria and Toxic Pollutants in SMOKE For the Models 3 User’s Workshop October 22, 2002 Madeleine Strum, OAQPS Collaborators: Marc Houyoux, MCNC/EMC Ron Ryan & Greg Stella, OAQPS Bill Benjey & Gerald Gipson, ORD Rich Cook, OTAQ strum.madeleine@epa.gov

2. EPA’s Toxics and Criteria Modeling Systems Separate Issues: Sound Science Consistency Efficiency • Photochemical vs Gaussian • SMOKE vs EMS-HAP • Criteria vs NTI Grid EPA is moving towards one-atmosphere modeling to address these issues strum.madeleine@epa.gov

3. One-Atmosphere Approach COMMENTS: National Emissions Inventory Still two separate inventories for 1999: toxics (HAPs) & criteria Modify to process multipollutant inventories SMOKE Add capabilities for toxics CMAQ strum.madeleine@epa.gov

4. Main Issue for SMOKE is to Address Overlap in Pollutants VOC from criteria inventory • No double-counting • Use of toxics inventory pollutants, where possible • Conservation of VOC mass, where possible Volatile organic HAPs from toxics inventory Note: even though we’re not looking at particulates, addressing the VOC – HAP overlap will impact PM modeling strum.madeleine@epa.gov

5. Steps in Determining Changes Needed to SMOKE • Examine criteria and toxics inventories; select when to use toxics in cases of overlap • Mobile sources: EPA-generated nonroad and MOBILE6 onroad inventories for toxics and critera are consistent • Stationary source: Generally not consistent • Examine potential modeling applications • Modeling ozone/PM using emission estimates for toxics from the toxics inventory in place of the criteria inventory • Modeling toxics using emission estimates for toxics from the toxics inventory strum.madeleine@epa.gov

6. Steps in Determining Changes Needed to SMOKE (continued) • Determine how CMAQ could be modified for the applications • No modifications needed for modeling ozone/PM • Develop new mechanisms and solvers to handle toxics • Modify CB-IV to treat key toxics explicitly (e.g., formaldehyde and acetaldyde) • Add capability to approximate chemical loss of other toxics outside chemical mechanism via pseudo-first order reaction rates • Determine model species needed and how SMOKE will produce them – see next slide for details strum.madeleine@epa.gov

7. How SMOKE Will Produce Model Species For Ozone/PM Modeling Mobile sources: integration - toxic pollutants (gaseous organic HAP) from toxics inventory - non toxics (nonHAP VOC) from criteria inventory Stationary sources: speciate criteria For Toxics Modeling Mobile sources: integration (same as above) Stationary sources: - speciate criteria for mechanism species that are not toxics - use toxics inventory for mechanism species that are explicit toxics (e.g., formaldehyde) - use toxics inventory for toxics modeled outside of mechanism strum.madeleine@epa.gov

8. Integration Approach for Mobile Sources VOC or TOG (criteria) emissions Gaseous HAP emissions Create NONHAPTOG or NONHAPVOC: = VOC – sum(gaseous toxics species) New SMOKE function Existing SMOKE function: but new speciation profiles are needed Speciation Model species strum.madeleine@epa.gov

9. Practical Considerations for Integration • The emission sources must be exactly the same for the toxics and the VOC/TOG • The methodology to estimate emissions should be consistent between the two inventories Both of these hold true for EPA-generated nonroad emissions and MOBILE6 generated emissions Generally, these don’t hold true for stationary sources strum.madeleine@epa.gov

10. Integration for Onroad Mobile Sources • SMOKE runs MOBILE6.2 to generate TOG and 26 gaseous HAPs such as benzene, acetaldehdye, PAHs • For each emission source, SMOKE creates a nonHAPTOG pollutant by subtracting the toxics from the TOG • SMOKE applies speciation profiles for nonHAPTOG and individual HAPs to generate emissions of model species. • For a toxic modeled outside the mechanism, SMOKE maps the toxic to itself and its mechanism species EXAMPLE SPECIATION PROFILES FOR ONROAD SOURCES 1313A NONHAPTOG OLE 0.00127373705 1 0.0357011 1313A NONHAPTOG PAR 0.03439269933 1 0.491116 0000 BENZENE BENZENE 1.00 78.11 1.0 0000 BENZENE PAR 1.00 78.11 0.1666667 0000 BENZENE NR 5.00 78.11 0.8333333 strum.madeleine@epa.gov

11. Integration for Nonroad Mobile SourcesSimilar to Onroad • SMOKE imports toxic and criteria nonroad emission sources to be integrated- user assures consistency in sources • SMOKE creates a nonHAPVOC pollutant by subtraction • SMOKE applies speciation profiles strum.madeleine@epa.gov

12. Approach For Stationary Sources is Replacement, not Integration • SMOKE imports both criteria and toxic inventories • SMOKE speciates criteria inventory using speciation profiles that zero out the explicit toxics model species (e.g., formaldehyde) • SMOKE maps the toxics inventory pollutants to the CB-IV explicit toxics model species • For a toxic modeled outside the mechanism, SMOKE maps the toxic to itself, but not its mechanism species EXAMPLE SPECIATION PROFILES FOR STATIONARY SOURCES 0307 TOG OLE 0.00126649899 1 0.03553 0307 TOG PAR 0.03791738749 1 0.5397267 0000 FORM FORM 0.00126649899 1 0.03553 0000 BENZENE_ST BENZENE 1.00 30.03 1 strum.madeleine@epa.gov

13. Summary • We have explored one-atmosphere modeling using toxics and criteria inventories in the SMOKE/CMAQ modeling system, focusing on gaseous HAPS • Benefits to ozone/PM modeling: better estimates of a subset of the pollutants (gaseous TOG) than current VOC speciation approach • Benefits to Toxics modeling: allows for use of photochemical grid models with toxics inventory • Wider integration will be possible when inventories become more consistent strum.madeleine@epa.gov