PM25 and species in CMAQ_v5.4

I had finished running CMAQ_v5.4, and working in analysis now. Here, I meet some questions.
PM25_TOT was extract from ELMO/AELMO file directly in SpecDef_cb6r3_ae7_aq.txt, I wonder how it calculated in detail, can you tell me which script should I check, how many species was included in PM25 ?

An overview of ELMO is provided in this appendix of the user guide.
The code implementation of the calculations is described in this section.
The two pieces of code defining and performing all calculations, including those for PM25_TOT, are ELMO_DATA.F and ELMO_PROC.F.

For PM25_TOT, the CMAQv5.4 ELMO calculations are equivalent to the definition of PM25_TOT in the SpecDef files released with earlier versions of CMAQ, e.g. here.

Dear Christian
Thanks for your help. I had extracted all of PM25 related variables from ELMO file. There are 22 variables in total, which include PM25 and other 21 variables(PM25_SO4, PM25_No3, PM25_NH4, PM25_CL, PM25_NA, PM25_EC, PM25_OC, PM25_OA, PM25_MG, PM25_K, PM25_CA, PM25_OTHER, PM25_FE, PM25_SI, PM25_TI, PM25_MN, PM25_AL, PM25_SOIL, PM25_UNSP1, PM25_UNSPCRS, PM25_HP). However, PM25 is not equal to the sum of other 21 variables.
SpecDef files in CMAQ_v5.3 calculate PM25 with variable of PM25AT, PM25AC, PM25CO, these variables were collect from PMDIAG and APMDIAG file(removed from v5.4), it brings new question.
I want to analysis differences of each species between different scenarios, could you please tell me how to calculate the detailed PM25 and component species, for example PM25= PM25_SO4+PM25_NO3+PM25_NH4……

Please have a look at section F2 of the ELMO documentation that specifically talks about the relationship of ELMO to previous CMAQ versions.

PM25AT from CMAQv5.3 APMDIAG has been renamed to FPM25AIT in CMAQv5.4 ELMO, PM25AC to FPM25ACC, etc… These cutoff fractions are included in the ELMO files if the ELMO keyword DEFAULT was specified in the configuration file, i.e. MISC_CTRL_NML

The definition of the PM2.5 variables in the ELMO output is identical to the definition in the v5.3.3 SpecDef file, if that species existed in the CMAQv5.3.3. SpecDef file. For those cutoff-specific PM2.5 species that were not defined in the v5.3.3 SpecDef file, you will need to look at the code in ELMO_DATA.F and ELMO_PROC.F. For example, PM25_UNSPCRS was not a part of v5.3.3, and in v54 it is defined as the non-speciated portion of the coarse mode species ASOIL and ACORS that falls in the PM2.5 size cutoff range (see lines 1548 - 1556 of ELMO_PROC.F). Therefore, you can reference the v5.3.3. SpecDef files for PM2.5 species defined in v5.3.3. (their definition did not change in v5.4) but will need to reference the v5.4ELMO code (the two files I mentioned in my initial post) to get details on how PM2.5 v5.4 species not defined v5.3.3 are being computed. Importantly, the definition of total PM2.5 mass (PM25 in v54 and PM25_TOT in v5.3.3) is identical in both versions.

The reason that the sum of the 21 species-specific variables is greater than the total PM25 mass in either CMAQv5.3.3 or CMAQv5.4 is that there is some overlap in mass between what is represented by some of these species. For example, PM25_OA is the total mass of organic aerosols while PM25_OC is only the mass of the carbon portion of these aerosols, so if you were to sum PM25_OA and PM25_OC in your total PM25 computation, you would double count that carbon portion. The reason both PM25_OA and PM25_OC are present in the output file is that PM25_OC can be used for comparisons to observations while PM_OA provides the full accounting for the mass CMAQ calculates for these aerosols, even if that quantity cannot routinely be measured.