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Sources, fractionation and fate of polybrominated diphenyl ethers and polychlorinated biphenyls in the Strait of Georgia, Canada Sun, Yuanji


The sources, dispersion, fractionation and fate of two persistent organic contaminants, polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs), were studied in the Strait of Georgia (SoG), by measuring dissolved (< 2.2 μm) and particulate (> 2.2 μm) PCBs and PBDEs concentrations in seawater at various Salish Sea stations from 2013 to 2018. Our results show that the primary sources of particulate PBDEs (pPBDEs) into the southern SoG are effluent particles from Vancouver’s main wastewater treatment plant at Iona Island and sediment resuspension in Burrard Inlet. In contrast, dissolved PBDEs (dPBDEs) in the southern SoG are generated from the desorption of PBDEs from these particles during their transport with the SoG water circulation, leading to high dPBDEs and low pPBDEs concentrations. These findings were supported by changes in particulate PBDEs contribution to the total PBDE concentrations at various stations, as well as the systematic fractionation of PBDE congeners during desorption from sewage particles and re-adsorption onto marine particles. In addition, the SoG estuarine circulation (including tides) leads to substantial temporal variability of dPBDEs concentrations in southern SoG and near Bowen Island. Most PBDEs in the SoG are eventually removed to the sediment through particle scavenging, leaving the less brominated congeners in the dissolved phase to be exported to the Pacific Ocean. The box model simulation demonstrated that the Fraser River is an important PBDE source due to its high flow rate, despite its low dPBDEs concentrations. Low modelled dPBDEs concentrations, compared with what we measured, point to unquantified sources or an increase in the PBDEs Iona discharge. PCBs have been banned for decades, and showed very different behaviour to PBDEs in SoG. Our limited data suggest that industrialized areas in Burrard Inlet are the main sources to SoG, and not the Iona outfall. Furthermore, the PCB homologs’ distribution supports preferential removal of the more hydrophobic dissolved PCBs congeners added to SoG from Burrard Inlet by particle scavenging. Once PCB-contaminated seawater and particles have been in contact long enough in SoG there is a clear increasing trend in particulate to dissolved partitioning with the degree of hydrophobicity of the PCB homologs.

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