Marine TSP samples were collected over the South China Sea by three different cruises, and the PM_2.5 samples were also simultaneously sampled during the first cruise in the north South China Sea. Concentrations of water-soluble ions were measured both in TSP and PM_2.5. Together with aerosol optical depth, firing spots and air masses backward trajectories, we divided the sampling periods into Asian outflow period, biomass burning period and the Philippine period. Water-soluble ionic levels displayed an obviously differences among the three cruises, which dominantly affected by ionic sources and atmospheric chemical processes. In addition, aerosol water-soluble ionic concentrations in fine and coarse mode also showed different patterns. The calculated dry deposition velocity ranged from 0.03 to 0.19 cm/s for fine mode and varied from 0.2~1.0 cm/s for coarse mode in 1°×1° latitude–longitude grids. Based on the dry deposition velocities, the dry deposition fluxes of NH₄⁺ and NO₃⁻ were estimated.

South China Sea; marine aerosol; water-soluble ions; dry deposition fluxes