Modelling multiphase chemistry in deliquescent aer

Authors: A Tilgner P Bräuer R Wolke H Herrmann

Publish Date: 2013/09/01

Volume: 70, Issue: 3, Pages: 221-256

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Abstract

Modelling studies were performed with the multiphase mechanism RACMMIM2ext/CAPRAM 30i to investigate the tropospheric multiphase chemistry in deliquesced particles and nonprecipitating clouds using the SPACCIM model framework Simulations using a nonpermanent cloud scenario were carried out for two different environmental conditions focusing on the multiphase chemistry of oxidants and other linked chemical subsystems Model results were analysed by timeresolved reaction flux analyses allowing advanced interpretations The model shows significant effects of multiphase chemical interactions on the tropospheric budget of gasphase oxidants and organic compounds Incloud gasphase OH radical concentration reductions of about 90  and 75  were modelled for urban and remote conditions respectively The reduced incloud gasphase oxidation budget increases the tropospheric residence time of organic trace gases by up to about 30  Aqueousphase oxidations of methylglyoxal and 14butenedial were identified as important OH radical sinks under polluted conditions The model revealed that the organic C3 and C4 chemistry contributes with about 38 /48  and 8 /9  considerably to the urban and remote cloud / aqueous particle OH sinks Furthermore the simulations clearly implicate the potential role of deliquescent particles to operate as a reactive chemical medium due to an efficient TMI/HOxy chemical processing including eg an effective insitu formation of OH radicals Considerable chemical differences between deliquescent particles and cloud droplets eg a circa 2 times more efficient daytime iron processing in the urban deliquescent particles were identified The incloud oxidation of methylglyoxal and its oxidation products is identified as efficient sink for NO3 radicals in the aqueous phase

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