Solar radiation and photochemical processes drive a large fraction of chemical reactions in the atmosphere. In the condensed phase (aerosol, cloud droplets, fog) solar radiation can drive both primary and secondary photolysis reactions. This increases the challenge in characterizing lifetimes of molecules in these systems. Atmospheric brown carbon (BrC) consists of molecules that can absorb solar radiation in the visible region and thus can play important roles in chemical transformations and energy budgets in the atmosphere. Recent work has developed a deeper understanding of the sources and formation processes of BrC, but gaps remain in our understanding of their decomposition and lifetimes, especially in complex, condensed-phase atmospheric water and particles. Here, we utilize UV-vis spectroscopy methods to characterize the photochemical decomposition of model BrC molecules in cloud water proxies containing mixtures of secondary organic aerosol and inorganic components. Our studies focus on the effects of a-pinene secondary organic aerosol and ammonium nitrate on the photolytic lifetime of 4-Nitrophenol. Preliminary data suggests a reduction in the half-life of this brown carbon molecule when it is photolyzed in mixed solutions.

Brown carbon photolysis: Impacts of organic and inorganic components in cloud water proxies

2019 Fall National Meeting

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