AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Studies of OH Oxidation of Cloudwater Organics
JONATHAN ABBATT, Rachel Hems, Alex Lee, Ran Zhao, University of Toronto, Toronto, Canada
Abstract Number: 101 Working Group: There Must be Something in the Water: Cloud, Fog and Aerosol Aqueous Chemistry for Aerosol Production
Abstract Although oxidative processes proceed readily in cloudwater, there remain significant uncertainties that preclude comprehensive modeling of this chemistry. This talk will present laboratory studies that address a number of these uncertainties. Particular attention will be given to the impacts of OH oxidation, wherein the properties of simulated and real cloudwater are observed. Most recent results are for the oxidation chemistry of dimeric substances that are common constituents of SOA. These molecules are easily oxidized in solution, forming monomers as products. Coloured compounds are also readily modified. For example, OH oxidation of the nitrophenols, a class of brown carbon constituent, leads initially to efficient formation of more colored compounds via functionalization of the aromatic ring, followed by loss of colour as ring-opening occurs under high oxidation conditions. The second portion of the talk addresses the sources of OH radicals in cloudwater. We demonstrate that dissolved SOA constituents can enhance the rates of OH generation, likely via direct photolysis of dissolved organic hydroperoxides. It is also observed that the rates of photoFenton chemistry involving light, dissolved iron, and hydrogen peroxide are suppressed in the presence of biogenic SOA compounds. We hypothesize that complex formation between iron and SOA molecules drives this behavior.