Mapping 2017gb_17j emission surrogates to CMAQv5.3.2 cb6r3_ae7_aq species

SMOKE Emissions Inventory
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  1. If I provide 2017gb_17j emissions as input to CMAQv5.3.2 with cb6r3_ae7_aq chemical mechanism, which CMAQ species should I map the surrogates NVOL and IVOC to?
  2. What is the motivation behind introducing AACD and FACD in 2017 emissions since they were not present in 2016 emissions?
  3. Should SULF species in the emissions files not be mapped to SULF gas species of CMAQ, but rather to ASO4 fine aerosol species?
  4. Should ACROLEIN in emission files be mapped to both ACROLEIN as well as to ACRO_PRIMARY gas species of CMAQ?
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Did you review the speciation section of the 2017 TSD?

https://www.epa.gov/air-emissions-modeling/2017-emissions-modeling-platform

It may answer some of these questions. Other answers will need to wait for next week, although I don’t think we use ACRO_PRIMARY in any of our emissions files.

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I have not seen SMOKE species to CMAQ species mapping being addressed in the document https://www.epa.gov/sites/production/files/2020-11/documents/2017_emissionschapter.pdf ; but this document may only be a chapter and not the full TSD.

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Here is some information we have pulled together:

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Hi @eyth.alison did you intend to include some link here?

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Hmm, that is strange – I had a lot of text in my response that got stripped out… Let me try again and see if it gets through

  1. If I provide 2017gb_17j emissions as input to CMAQv5.3.2 with cb6r3_ae7_aq chemical mechanism, which CMAQ species should I map the surrogates NVOL and IVOC to? In the currently-released CMAQ, there are no relevant model species for NVOL and IVOC and these emissions get dropped.

  2. What is the motivation behind introducing AACD and FACD in 2017 emissions since they were not present in 2016 emissions? Technically, these were always part of CB6, per Heather Simon “Acetic acid (AACD) and Formic acid (FACD) were not explicit species in CB05 but are explicit in CB6 which we began to use with CMAQv5.2. AACD and FACD both participate in radical/ozone chemistry in CB6r3.” Heather also stated “: “ I am not sure that this will have much impact on ozone, but it will be more technically correct. “ Heather’s response is correct. We first started generating AACD and FACD emissions when we moved to CB6R3AE7 although CMAQ supported AACD/FACD before we updated the mechanism on the emissions side. Before we updated the emissions mechanism to CB6R3AE7, we just didn’t pass any AACD/FACD emissions to CMAQ.

  3. "Should SULF species in the emissions files not be mapped to SULF gas species of CMAQ, but rather to ASO4 fine aerosol species? I believe these are generated from gaseous SO2 and I think ASO4 comes from the speciation of PM2.5 only. We haven’t changed how SULF is generated since 2007. SULF is generated as a fraction of SO2 for 119 point and nonpoint SCCs (mostly coal and oil boilers). It doesn’t subtract from SO2, it’s in addition to SO2. For those 119 SCCs, SULF is 1-3% of SO2 (varies depending on the SCC). We are not sure how CMAQ uses SULF.

  4. Should ACROLEIN in emission files be mapped to both ACROLEIN as well as to ACRO_PRIMARY gas species of CMAQ? yes

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Thanks a lot for the response!

1 Like
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Hi,

I can provide a bit more information for the third question:
3. "Should SULF species in the emissions files not be mapped to SULF gas species of CMAQ, but rather to ASO4 fine aerosol species? I believe these are generated from gaseous SO2 and I think ASO4 comes from the speciation of PM2.5 only. We haven’t changed how SULF is generated since 2007. SULF is generated as a fraction of SO2 for 119 point and nonpoint SCCs (mostly coal and oil boilers). It doesn’t subtract from SO2, it’s in addition to SO2. For those 119 SCCs, SULF is 1-3% of SO2 (varies depending on the SCC). We are not sure how CMAQ uses SULF .

In CMAQv5.3 and beyond, an emission rule is added automatically, after all other rules, that zeros out SULF emissions and maps them instead to ASO4. You can find this in EMIS_VARS.F. This choice is consistent with CMAQ versions before 5.3. In those previous versions, I believe the remapping was done in AERO_EMIS.F. The assumption that any sulfuric acid produced in point source plumes immediately converts to ASO4 is a natural one considering the extremely low volatility of sulfuric acid and the assumption of emitted particle diameters consistent with urban background aerosol (presumably after immediately available condensable vapors have condensed).