Atmospheric organosulfate formation regulated by continental outflows and marine emissions over East Asian marginal seas

Abstract. Organosulfates (OSs) represent an unrecognized fraction and a potentially important source of marine organic aerosols. Based on shipboard observations over East Asian marginal seas, we characterized OSs in marine aerosols during spring, summer, and autumn. The C2–C3 OSs and isoprene-/monoterpenes-derived OSs were quantified using synthesized standards. The total quantified OSs concentrations ranged from 4.5 to 109.1 ng m−3, contributing 0.1 %–3.2 % of the mass concentration of marine organic aerosols. The highest OSs concentrations, dominated by C2–C3 OSs and isoprene-OSs, were observed in summer, which surpassed the abundance of methane sulfonic acid, a key component in climate regulation by oceanic phytoplankton sulphur emissions. Abundant OSs formation in summer was mainly attributed to the increased isoprene emissions from the ocean. During the spring and autumn cruises, transported continental pollutants resulted in the higher fraction of monoterpene-derived (nitrooxy-)OSs, as well as the elevated OSs concentrations over regions surrounded by the continent. This work highlights the joint effects of marine emissions and continental outflows on the formation and distribution of atmospheric OSs over marginal seas.