Legacy and novel halogenated flame retardants in seawater and atmosphere of the Bohai Sea: Spatial trends, seasonal variations, and influencing factors

Seventeen halogenated flame retardants (HFRs) were concurrently analyzed in surface seawater and low atmospheric samples from the Bohai Sea during four research cruises. HFRs mainly existed in particulate phases, and in general decabromodiphenyl ethane (DBDPE) was the predominant compound in both air and water samples. Relatively high concentrations were observed in the water of Laizhou Bay (LB), where the largest manufacturing base of brominated flame retardants (BFRs) in China is located and weak water exchange occurs. Transport from LB by coastal currents may be the main source of BFRs in some areas without emission sources. The HFRs in seawater exhibited distinct seasonal variation, with significantly higher concentrations in winter than those in summer. The controlling factors include the resuspension of sediment induced by large wind waves in winter and phytoplankton scavenging in spring and seawater stratification in summer. HFRs composition varied largely in different seasons, due to the different extents of riverine input and atmospheric deposition. Normally, for air masses passing through the nearby industrial regions, high concentrations of DBDPE (up to 1780 pg m-3) co-existed with high total suspended particle (TSP) levels (up to 150 μg m-3). The estimated atmospheric deposition fluxes of HFRs were 19, 51, and 80 kg season-1 in spring, summer, and winter, respectively, indicating that the Bohai Sea is a sink of HFRs via atmospheric deposition. This study has increased our understanding of the behaviors and fates of the legacy and novel HFRs in the shallow coastal sea.