I can find the switch about turn off the aerosol heterogeneous reactions in earlier versions (model 3,https://cmascenter.org/cmaq/documentation/0*madrid_2004/CMAQ-MADRID-2004-UsersGuide.pdf)，does this switch still exist? Or is there any other way which can help me to achieve turn off the aerosol heterogeneous reactions, such as changing the rate to 0?
Most heterogeneous reactions use a factor of 1.0 (for example, 1.0~<HETERO_N2O5IJ> in mech.def). You can revise 1.0 to 0.0 and recompile and run the model.
Alternately, you can revise RXNS_FUNC_MODULE.F90. You can find the reaction label associated with the heterogeneous rection, revise the RKI value to assign 0.0 values, recompile, and run the model.
In both cases, please check the results to make sure the revised reaction produces the intended results.