# How to turn off aerosol heterogeneous reactions

**URL:** <https://forum.cmascenter.org/t/how-to-turn-off-aerosol-heterogeneous-reactions/4426>\
**Category:** CMAQ\
**Created:** [September 26, 2023, 12:32pm UTC](https://forum.cmascenter.org/t/how-to-turn-off-aerosol-heterogeneous-reactions/4426 "2023-09-26T12:32:57Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![bandaoshutiao](https://avatars.discourse-cdn.com/v4/letter/b/9fc348/32.png) [@bandaoshutiao](https://forum.cmascenter.org/u/bandaoshutiao)\
**Post date:** [September 26, 2023, 12:32pm UTC](https://forum.cmascenter.org/t/how-to-turn-off-aerosol-heterogeneous-reactions/4426/1 "2023-09-26T12:32:57Z")

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Hi everyone

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](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?

shutiao

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**Author:** ![gsarwar](https://avatars.discourse-cdn.com/v4/letter/g/5f9b8f/32.png) [@gsarwar](https://forum.cmascenter.org/u/gsarwar)\
**Post date:** [November 11, 2023, 4:00pm UTC](https://forum.cmascenter.org/t/how-to-turn-off-aerosol-heterogeneous-reactions/4426/2 "2023-11-11T16:00:48Z")

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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.

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**Author:** ![lizadams](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@lizadams](https://forum.cmascenter.org/u/lizadams)\
**Post date:** [November 17, 2023, 8:41pm UTC](https://forum.cmascenter.org/t/how-to-turn-off-aerosol-heterogeneous-reactions/4426/3 "2023-11-17T20:41:08Z")

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Closed on November 17, 2023, 8:41pm UTC