An Experimental Assessment of the Importance of S(IV) Oxidation by Hypohalous Acids in the Marine Atmosphere

Abstract

AbstractHypohalous acids (HOCl + HOBr) play an important but highly uncertain role in sulfate aerosol production in the marine atmosphere due to the unmeasured reaction rate constants (k) of HOCl/HOBr and HSO3−, the dominant S(IV) species in acidified sea salt aerosols and cloudwater. We directly determined by investigating the kinetics of aqueous oxidation of dissolved SO2 by HOCl in low pH aerosol particles in a flow tube. Further, we predicted using a novel kinetics model developed from the HOCl/HSO3− results. and were estimated to be 2 and 3 orders of magnitude lower, respectively, than the values used in atmospheric models. We assess the importance of halogen‐driven S(IV) oxidation in the marine atmosphere with this new fundamental understanding and find that in‐cloud sulfate production via HOBr oxidation remains an important atmospheric process, but the HOCl oxidation pathway in acidified sea salt aerosols is unlikely to be important.