HONO produced by the photolysis of adsorbed HNO3 on surfaces in CMAQ

Hi everyone,
Recently I am learning the mechanism of HONO production in CMAQ. I notice that Sarwar et al. (2008) says that “Zhou et al. (2003) recently conducted laboratory experiments and suggested that adsorbed HNO3 on surfaces can undergo photolysis to produce HONO and NO2. Adsorbed HONO and NO2 are then released into the atmosphere via desorption. A simplified photolysis reaction producing HONO and NO2 was added to the CMAQ modeling system. Adsorbed HNO3 on ground surfaces is assumed to equal the amount of HNO3 accumulated over time by dry deposition since the last precipitation event”. But I don’t find the related chemical reaction of HONO produced by the photolysis of adsorbed HNO3 on surfaces in “mech.def”. Is the chemical reaction of HNO3 producing HONO considered in CMAQ now? If yes, where can I find the codes or files related to this chemical reaction. Is the related code included in vdiffacmx.F? Any comments are highly appreciated!
Thanks very much for your help!

Best wishes,

Hi Lingyun,

Sarwar et al. (2008) included the pathway for HONO production from photolysis of adsorbed HNO3 on surfaces. However, it is not included in the CMAQ model. The current CMAQ model includes production of HONO from heterogeneous reaction of NO2 on aerosol and ground surface as well as HONO emissions. I plan to revise the HONO chemistry in the future CMAQ model to include updated chemistry.


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Hi Sarwar,
Thanks very much for your reply!
All the best,