Identifying and quantifying atmospheric sources of PCBs to Saint Lawrence Estuary beluga habitat

Frank Wania, Faqiang Zhan, Yuening Li, Jenny Oh, Chubashini Shnuthirasingham, Ying Duan Lei, Zhe Lu, Amina  Ben Chaaben, Abigaëlle Dalpé Castilloux, Nick   Alexandrou, Chunwen  Weng, Hayley Hung

Persistent organic contaminants, such as the polychlorinated biphenyls (PCBs), have been shown to bioaccumulate in the Saint Lawrence Estuary Belugas (SLEBs) and may be impacting their health. Atmospheric deposition is often the dominant source of organic contaminants to aquatic ecosystems and is likely also important in delivering PCBs to the SLEB habitat. We quantified concentrations of organic contaminants of potential concern for the SLEBs in air, water and atmospheric deposition using networks of passive air and water samplers across Southern Quebec, coupled with active air and deposition samplers in Tadoussac. The passive air sampling network encompassed the Saint Lawrence River valley between Montreal and Quebec City as well as the shores of the estuary up to Sept-Iles and Sainte Anne-des-Monts on the North and South shore, respectively. Air concentrations of PCBs were elevated at most sites along the Montreal-Quebec City corridor, consistent with the region's high population density and industrial history. Particularly high PCB concentrations were recorded in the vicinity of a waste incinerator in Quebec City and at a location in Montreal where PCB-containing equipment had been stored. Locally elevated levels also point to the existence of PCB sources to the atmosphere along the shores of the estuary (Sept-Iles) and in the Lac-Saint-Jean region (Alma). Conversely, the passive air sampling network could exclude several electrical transformer stations as significant sources of PCBs to the atmosphere. The analysis of a large number of PCB congeners allows us to employ multivariate statistical approaches to distinguish between PCB sources related to the use of technical PCB mixtures and those resulting from unintentionally produced PCBs. Combining our measurements with atmospheric dispersion and deposition calculations, driven by historical emission estimates, facilitates the estimation of the time-varying atmospheric input of PCBs to the habitat of the SLEBs.