Distribution, sources and dispersion of polybrominated diphenyl ethers in the water column of the Strait of Georgia, British Columbia, Canada

Yuanji Sun; Roger Francois; Richard Pawlowicz; Maria T Maldonado; Samuel W Stevens; Maureen Soon

doi:10.1016/j.scitotenv.2023.162174

Distribution, sources and dispersion of polybrominated diphenyl ethers in the water column of the Strait of Georgia, British Columbia, Canada

Sci Total Environ. 2023 May 15:873:162174. doi: 10.1016/j.scitotenv.2023.162174. Epub 2023 Feb 11.

Authors

Yuanji Sun¹, Roger Francois², Richard Pawlowicz¹, Maria T Maldonado¹, Samuel W Stevens¹, Maureen Soon¹

Affiliations

¹ Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, 2207 Main Mall #2020, Vancouver, BC V6T 1Z4, Canada.
² Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, 2207 Main Mall #2020, Vancouver, BC V6T 1Z4, Canada. Electronic address: rfrancois@eoas.ubc.ca.

PMID: 36781132
DOI: 10.1016/j.scitotenv.2023.162174

Abstract

Dissolved and particulate polybrominated diphenyl ether (PBDE) concentrations were measured in the water column of the Strait of Georgia (SoG), Haro Strait, Juan de Fuca Strait, Burrard Inlet, and the Fraser River to assess their sources and dispersion. Total PBDE concentrations in the water column of the southern basin of the SoG are surprisingly high (similar to the load reported for coastal zones heavily impacted by human activities). Moreover, the dissolved fraction (i.e. passing through a 2.2 μm pore size filter) accounts for >95 % of the total load, which is unlike what is more typically found in other coastal zones, where particulate PBDEs generally dominate. Decreasing concentrations away from the southern SoG, eventually reaching typical open ocean values in Juan de Fuca Strait, point to the Vancouver metropolitan area as the main proximal source of PBDEs. About half of the direct PBDE input comes from wastewater treatment plants, with atmospheric deposition and the Fraser river accounting for most of the rest. However, these direct sources alone cannot explain the high dissolved PBDE load observed in the water column of southern SoG. PBDE scavenging rates estimated from concentration gradients and water transit times imply a PBDE flux to the seafloor which largely exceeds the measured burial rates of PBDEs in sediments. To reconcile these observations and explain the dominance of the dissolved fraction in the water column of the southern SoG, we invoke and provide supporting evidence for the release of colloidal PBDE from the resuspension of PBDE-contaminated sediments by bottom currents. If confirmed, this continued PBDE exchange between sediments and the water column would maintain high levels of PBDEs, and possibly other hydrophobic and persistent organic contaminants, in the water column of the southern SoG until the contaminated sediments are buried below the sediment mixed layer.

Keywords: PBDE; Salish Sea; Seawater; Sediment resuspension.