Polychlorinated dibenzo-p-dioxins and dibenzofurans in Niagara River suspended sediments

• Archived Niagara River suspended sediment was analyzed for dioxins and furans.
• Results indicate episodic discharges of dioxins and furans from identified hazardous waste sites.
• Congener profiles in Lake Ontario implicate the Niagara River as a source of dioxins.
• The temporal trend indicates little change since 1990.

Niagara River archived suspended sediments were analyzed for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) to investigate temporal trends and to assess congener profiles as source indicators. In general, concentrations ranged from 6 to 35 pg g−1 toxic equivalents (TEQs) and 1000–6000 pg g−1 total PCDDs/Fs and reflected a slight decline in the 1980s, but with little apparent change since that time. This temporal trend was consistent with those observed in Lake Ontario environmental compartments. The observed levels generally reflected ambient background levels in the Niagara River; however, three samples were substantially above ambient levels and a fourth sample, while not elevated, had a profile that was distinctly different from those typically observed at Niagara-on-the-Lake at the mouth of the Niagara River. Event-based concentrations ranged from approximately 160–620 pg g−1 TEQs; congener profiles for these samples were consistent with known source areas in the Niagara River watershed, including Pettit Flume and Bloody Run Creek. These qualitative and quantitative results indicated loadings of dioxins and furans from hazardous waste sites in the Niagara River are occurring episodically, and can be measured in suspended sediments downstream at the river mouth at Niagara-on-the-Lake.