Abstract View
Multiphase Heterogeneous OH Oxidation of a Long Chain Alkyl Sulfate
SZE IN MADELEINE NG, Rongshuang Xu, Man Nin Chan, The Chinese University of Hong Kong
Abstract Number: 636
Working Group: Aerosol Chemistry
Abstract
Atmospheric organosulfur species are ubiquitous in aerosols. Among these species, organosulfates are one of the major classes. A large variety of alkyl sulfates has been found but their sources and transformation pathways are poorly understood. We carried out an laboratory experiments on the heterogeneous OH oxidation of sodium dodecyl sulfate (SDS) aerosol, which investigates how this long chain alkyl sulfate chemically transformation in the atmosphere by identifying the reaction products before and after oxidation using an aerosol flow tube coupled with an atmospheric pressure soft ionization source (Direct analysis in Real Time, DART) and a high resolution mass spectrometer. From aerosol-DART spectra, we found that SDS decays at a faster rate (an effective OH rate constant of 2.65 ×10-12 cm3 molecule-1 s-1) than that of smaller alkyl sulfates (e.g. methyl- and ethyl sulfate). Product analysis show that a number of more oxygenated functionalization products were formed upon oxidation. Inorganic sulfate was also formed, but with a lower abundance. We postulate that the small sulfate yield might attribute to the longer carbon chain and the morphology of SDS near the aerosol surface, which may unfavor fragmentation processes and the generation of sulfate radicals upon oxidation. This limits the formation of inorganic sulfate via sulfate radical chemistry. The results of this work provide greater insights into the heterogeneous OH chemistry of organosulfates and their atmospheric fates.