Molecular evidence on potential contribution of marine emissions to aromatic and aliphatic organic sulfur and nitrogen aerosols in the South China Sea

Abstract. Marine atmospheric organic aerosols play a pivotal role in regulating global climate dynamics and influencing marine biogeochemical cycles. Compared to the extensive research on marine isoprene-derived secondary organic aerosols (SOAs), the origins of marine aromatic and aliphatic organic aerosols remain elusive. Here, organosulfates (OSs) and nitrogen-containing organic compounds (NOCs) were measured in PM2.5 collected in Sansha (the South China Sea), a region with minimal anthropogenic pollution, to investigate the potential impact of marine emissions on their formation. The proportion of aliphatic and aromatic OSs in the total OSs was higher in Sansha than in other Chinese cities investigated. The abundances of biogenic OSs correlated with both total aliphatic OS and NOC abundances, as well as with total aromatic OS and NOC abundances. Two typical SOA tracers (C6H5O4S− and C7H7O4S−), which are formed via the atmospheric oxidation of marine benzene and toluene, were found to increase with rising chlorophyll a and isoprene levels in surface seawater. Additionally, the impact of long-range transport and ship emissions on the abundances of OSs and NOCs was found to be insignificant. These results together with mantel test analysis suggest that marine-derived precursors may substantially contribute to the formation of aliphatic and aromatic OSs and NOCs in the Sansha region. Overall, this study provides the observation-based molecular evidence that marine biogenic emissions may play a significant role in the formation of aromatic and aliphatic organic aerosols in the South China Sea.