SO2 Uptake on Oleic Acid: A New Formation Pathway of Organosulfur Compounds in the Atmosphere
Résumé
Organosulfates are tracers for secondary organic aerosol (SOA)
formation. We propose a new mechanism of organosulfur product formation
in the atmosphere, in which sulfur dioxide (SO2) reacts directly with
alkenes. The experiments were conducted at the gas-liquid interface with
a coated-wall flow tube reactor. It was shown, for the first time, that
SO2 reacts efficiently with the unsaturated bond in oleic acid under
atmospheric conditions (without ozone), leading to the formation of C-9
and C-18 organosulfur products. The associated uptake coefficients were
in excess of 10(-6), decreasing with initial SO2 concentration and
increasing with humidity. These results might explain a fraction of
organosulfur products detected in atmospheric particles. This work tends
to elucidate the role of organosulfates' interfacial chemistry as a
potentially unrecognized pathway for their contribution to SOA
formation; however, it remains to be determined how significant this
pathway is to the overall organosulfate abundances measured in ambient
aerosol.