Secondary organic aerosols (SOA) produced by photooxidation of biogenic and anthropogenic volatile organic compounds (VOCs) are the dominant component of particulate matter. SOA particles continuously change their chemical composition over time as a result of various chemical and physical aging processes. This paper reports a combined experimental and modeling study of the aging chemistry of SOA resulting from reactions of ammonia with carbonyl compounds in SOA. Various types of VOCs are oxidized in a smog chamber to form SOA, and the resulting particles are exposed to a pulse of ammonia. The gases and particles in the smog chamber are monitored with a suite of instruments to measure the uptake rate of ammonia by SOA. The chemical composition of SOA particles is analyzed by on-line and off-line methods to determine the mechanism of the ammonia + SOA reactions. The experimental results are incorporated into the University of California, Irvine - California Institute of Technology (UCI-CIT) regional airshed model to investigate the effect of the ammonia + SOA chemistry on the amount of particulate matter produced under different scenarios. The model predicts that the chemical uptake of ammonia by SOA can significantly reduce the concentration of gas-phase ammonia, thereby indirectly affecting the amount of ammonium sulfate and ammonium nitrate in particulate matter.

Reactive uptake of ammonia by biogenic and anthropogenic organic aerosols

254th National Meeting (2017)

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