Gas-to-particle partitioning of atmospheric water-soluble organic aerosols: Indications from high-resolution observations of stable carbon isotope

One-hour resolution observations of stable carbon isotopes in both gaseous water-soluble organic carbon (WSOCg) and particulate water-soluble organic carbon (WSOCp) were conducted at a city site in the Yangtze River Delta. WSOCg exhibited significantly higher concentrations and lower 13C compared to WSOCp. The presence of radiation emerged as a crucial factor influencing the gas-particle partitioning mechanism of WSOC. There appeared to be distinct formation processes for WSOCp and WSOCg during nighttime, except on hazy days with elevated particulate matter concentrations. Gas-particle partitioning of WSOC may become inactive in environments with high temperatures and ozone concentrations, while it may become active in environments characterized by high relative humidity (RH) and elevated WSOCg concentrations. When addressing WSOC pollution, it's essential to focus not only on its sources but also on the suitable environmental conditions for gas-particle partitioning. Active gas-particle partitioning of WSOC may coincide with the formation of secondary inorganic ions (NH4+, NO3− and SO42−). Thus, in targeting WSOC sources, it's imperative to implement coordinated strategies to control the sources of secondary inorganic ions. •Photochemical production is a critical mechanism of WSOC gas-particle partitioning during the wintertime.•δ13C–WSOC is influenced by both WSOC source compositions, meteorological conditions and gaseous pollutants concentrations.•Secondary inorganic ions are formed synergistically during gas-particle partitioning of WSOC.