Seasonal Air–Sea Exchange Dynamics of Polychlorinated Biphenyls Over the East China Marginal Seas: The Role of Water Masses in a Complex Coastal–Ocean Current System

Abstract

Continental marginal seas are key reservoirs of anthropogenic pollutants. Understanding the physical processes controlling the air–sea exchange dynamics of polychlorinated biphenyls (PCBs) in the continental margin seas is crucial to constrain the contribution of PCBs from land and rivers to the ocean; however, the transport and fate of PCBs, and their controlling factors of air–sea exchange in the continental marginal seas still remain poorly understood. Here, we collected atmospheric and surface water samples from the Yellow Sea (YS) and East China Sea (ECS) in summer 2018 and winter 2019, and examined the PCB concentrations. The PCB air–sea gas exchange fluxes showed higher net volatilization in winter, largely due to southward movement of the strengthened Yellow Sea Coastal Current and Yangtze River Diluted Water with high PCB concentrations. Both the dissolved PCB concentrations in seawater and wind speed were the primary factors influencing the PCB air–sea exchange fluxes in winter. By contrast, weak PCB volatilization fluxes occurred when the Taiwan Warm Current with low PCB concentrations dominated in the ECS in summer. In comparison, the accumulation and release of some PCB homologues caused by a green tide in the coastal YS could lead to increased volatilization flux in summer. Our results suggest the transfer of air–sea exchange dynamics of PCBs from a water concentration‐dominated pattern to an environmental parameter‐controlled one due to their decreased land‐based input, and highlight the impact of water mass‐triggered changes (environmental parameters and algal blooms) on the air–sea exchange behavior of PCBs in the continental marginal sea.