If you want to add a heterogeneous reaction or modify an existing heterogeneous reaction, then you need to define them in the mechanism definition file and use CHEMMECH processor to generate RXNS_DATA_MODULE.F90 and RXNS_FUNC_MODULE.F90. You may need to modify GC_*nml file. Then you need to revise AEROSOL_CHEMISTRY.F to add or update rate constants for the heterogeneous reaction. You will need to define all parameters and calculate first order rate constant in AEROSOL_CHEMISTRY.F.

CMAQ/DOCS/Users_Guide/Tutorials/CMAQ_UG_tutorial_chemicalmechanism.md at main · USEPA/CMAQ · GitHub