LAUSR

The Arctic Ocean is known to be contaminated by various persistent organic pollutants (POPs). The Fram Strait, the only deepwater passage to the Arctic Ocean (from the Atlantic Ocean), represents an unquantified gateway for POPs fluxes into and out of the Arctic. Polyethylene passive samplers were deployed in vertical profiles in the Fram Strait and in air and surface water in the Canadian Archipelago to determine the concentrations, profiles, and mass fluxes of dissolved polychlorinated biphenyls (PCBs) and organochlorine pesticides. In the Fram Strait, higher concentrations of ΣPCBs (1.3–3.6 pg/L) and dichlorodiphenyltrichloroethanes (ΣDDTs, 5.2–9.1 pg/L) were observed in the deepwater masses (below 1,000 m), similar to nutrient-like vertical profiles. There was net southward transport of hexachlorobenzene and hexachlorocyclohexanes (ΣHCHs) of 0.70 and 14 Mg/year but a net northward transport of ΣPCBs at 0.16 Mg/year through the Fram Strait. Plain Language Summary Persistent organic pollutants can reach the Arctic Ocean by long-range atmospheric transport, ocean currents, and inputs from the large Arctic rivers. Polychlorinated biphenyls (PCBs) and organochlorine pesticides, which have been extensively used since the 1930s, were banned and listed in the United Nations Environment Programme Stockholm Convention on persistent organic pollutants in 2001. We performed the first pan-Arctic deployments of passive samplers to gain knowledge of the occurrence, transport, and fate of these legacy contaminants in the remote Arctic. Our results demonstrated the ubiquitous presence of persistent industrial and agricultural contaminants across the Canadian Arctic and throughout the water column of the Fram Strait. While atmospheric transport seems mostly responsible for the presence of these pollutants in the surface Arctic Ocean, in the Fram Strait, concentrations of PCBs and dichlorodiphenyltrichloroethanes (DDTs) increased in deep waters, indicating their penetration to the deep ocean environment. Our results also showed the legacy hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) are released from the Arctic Ocean to the Atlantic Ocean via the deepwater Fram Strait, while PCBs are still loaded from the Atlantic Ocean to the Arctic Ocean.