O.k., this makes sense now. Others on this forum certainly are more knowledgeable than me about this topic, but here is the basic idea:
First, you need to decide if you want to map your primary OC emissions into a nonvolatile or semivolatile framework. For the former, 100% of POC is mapped to APOC and 100% of PNCOM is mapped to APNCOM. For the latter, POC and PNCOM are each distributed across the gas phase species VLVPO1, VSVPO1, VSVPO2, VSVPO3, VIVPO1 and the aerosol species ALVPO1, ASVPO1, ASVPO2, ASVPO3, AIVPO1, though some of the default weights are zero. The weights for POC and PNCOM add up to 1 each. If you use the semivolatile framework, you cannot currently perform source apportionment of (primary) OC, but you would gain a more realistic representation of how primary OC emissions affect ambient OC and OM concentrations.
Regardless of your choice, you want to make sure that the scaling factors applied to your POC and PNCOM emissions each add up to 1 to avoid losing or gaining mass. In the case of selecting the nonvolatile framework, this portion of EmissCtrl would look as follows:
! → Nonvolatile POA
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘APOC’ ,‘FINE’,1. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘APNCOM’ ,‘FINE’,1. ,‘MASS’,‘a’,
! → Semivolatile POA
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘VLVPO1’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘VLVPO1’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘VSVPO1’ ,‘GAS’ ,0.,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘VSVPO1’ ,‘GAS’ ,0.,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘VSVPO2’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘VSVPO2’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘VSVPO3’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘VSVPO3’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘VIVPO1’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘VIVPO1’ ,‘GAS’ ,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘ALVPO1’ ,‘FINE’,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘ALVPO1’ ,‘FINE’,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘ASVPO1’ ,‘FINE’,0.,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘ASVPO1’ ,‘FINE’,0.,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘ASVPO2’ ,‘FINE’,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘ASVPO2’ ,‘FINE’,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘ASVPO3’ ,‘FINE’,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘ASVPO3’ ,‘FINE’,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘POC’ ,‘AIVPO1’ ,‘FINE’,0. ,‘MASS’,‘a’,
‘EVERYWHERE’, ‘ALL’ ,‘PNCOM’ ,‘AIVPO1’ ,‘FINE’,0. ,‘MASS’,‘a’,
When you look at the SpecDef file used for post-processing CMAQ output, you’ll see that the definitions of APOCI, APOCJ, AOMI, and AOMJ include both the non-volatile and semi-volatile primary organic carbon species, with the understanding that the user selected either framework in EmissCtrl and set the emission scaling factors for the non-selected framework to zero. Thus, when you mentioned in your initial post that OC was zero, you may only have looked at APOCI, APOCJ, ANCOMI, and ANCOMJ but not all of the other primary organic aerosol species used in your default emissions assignment (ALVPO1, ASVPO1, ASVPO2, ASVPO3, AIVPO1).