SO₂ Uptake on Oleic Acid: A New Formation Pathway of Organosulfur Compounds in the Atmosphere

Abstract

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 (SO 2 ) 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 SO 2 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 SO 2 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.