Exchange Dynamics of Typical Emerging and Legacy Persistent Organic Pollutants at the Air-Water Interface Over a Strongly Human-Influenced Large River Estuary

To explore the riverine or atmospheric influence on the source-sink fates of typical persistent organic pollutants (POPs): polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in the large river estuary, atmospheric and seawater samples were collected simultaneously over a whole year at a remote small island in the Yangtze River Estuary (YRE), the East China Sea. A comparable net input of BDE-209 from the atmosphere to the sea for both air-water gas exchange and dry/wet deposition was observed. The gas deposition of BDE-209 had a strong dependence on the gaseous concentration, which was in turn governed by atmospheric transport. For Br-<10-BDEs, which have been prohibited in recent years, the gas exchange almost reached equilibrium at the air-water interface during the whole observation period. However, a strong net gas volatilization was observed for legacy sigma(ICES)PCBs especially in the flood season, and the volatilization was significantly associated with ambient parameter-wind speed. These remarkably different exchange dynamics of PBDEs and PCBs at the air-water interface over the YRE could be attributed to their primary emission intensity and inconsistent environmental transport pathways. The reversal of the source-sink fates of BDE-209 and legacy PCBs suggest that the strongly human-influenced large river estuary water could act as a source-sink buffer for POPs during the switch from approved to prohibited usage.