Long-range transport of anthropogenic air pollutants into the marine air: Insight into fine particle transport and chloride depletion on sea salts
Abstract. Long-range transport of anthropogenic air pollutants from East Asia can affect the downwind marine air quality during spring and winter. Long-range transport of continental air pollutants and their interaction with sea salt aerosols (SSA) significantly modify the radiative forcing of marine aerosols and influence ocean biogeochemical cycling. Previous studies poorly characterize variations of aerosol particles along with air mass transport from the continental edge to the remote ocean. Here, the research ship R/V Dongfanghong 2 traveled from the eastern China seas (ECS) to the northwestern Pacific Ocean (NWPO) to understand what and how air pollutants were transported from the highly polluted continental air to clean marine air in spring. A transmission electron microscope (TEM) was used to find the long-range transported anthropogenic particles and the possible Cl-depletion phenomenon of SSA in marine air. Primary and secondary anthropogenic aerosols were identified and dramatically declined from 87 % to 8 % by number from the ECS to remote NWPO. For the SSA aging, 86 % of SSA particles in the ECS were identified as fully aged, while the proportion of fully aged SSA particles in the NWPO decreased to 31 %. The result highlights that anthropogenic acidic gases in the troposphere (e.g., SO2, NOx, and volatile organic compounds) were transported longer distances compared to the anthropogenic aerosol and could exert a significant impact on marine aerosols in the NWPO. These results show that anthropogenic particles and gases from East Asia significantly perturb aerosol chemistry in marine air. The optical properties and cloud condensation nucleation of the modified SSA particles should be incorporated into the more accurately modeling of clouds in the ECS and NWPO in spring and winter.