Examination of Metal Contamination within the UNESCO Designated Rideau River Waterway
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The Rideau River Waterway, also known as the Rideau Canal, is a constructed navigation channel that links Ottawa to Kingston, Ontario. Opened in 1832, it was designated a Canadian Heritage Site in 2003 and a UNESCO World Heritage Site in 2007. South of Smiths Falls, the Rideau Canal consists of a series of 14 interconnected lakes, primarily used for recreational purposes, as well as commercial fishing. The objectives of this study were to examine the spatial and temporal distributions of anthropogenic elements to three headwater lakes of the Rideau Canal system and to examine the relationship between sport fish Hg and historical sediment Hg concentrations. Utilizing paleolimnological techniques, historical records of As, Cd, Co, Cr, Cu, Hg, K, Ni, Pb, Rb, and Zns were analyzed from chronologically deposited lake sediments. Overall, Indian Lake, though the smallest of the three studied lakes, consistently had the highest overall As, Cd, Cu, Hg, Ni, Pb and Zn concentrations. While all peak concentrations were buried, recent surface sediment Hg, Cd, and Zn concentrations still remain above the federal interim sediment quality guideline and the concentration of Pb remains above the federal probable effect level within Indian Lake, leading to continued concern for human and ecosystem health. The general agreement between lake sediment profiles for Cd, Pb and Zn and then Cu and Ni suggest that each group of elements is primarily contributed from the same source. The similarity in trends and timing of peak concentrations between the study lakes and other Ontario lakes suggests large-scale, atmospheric contributions of elements to the freshwater systems in the area. Although only historical northern pike (Esox lucius) THg tissue concentration data was available for analysis, results indicate that concentrations in fish have decreased more than 60% since the late 1970âs, while sediment THg concentrations have decreased 35% within the same time period. Overall, this study has demonstrated that the headwater lakes to the Rideau Canal are presently impacted by elements, at concentrations which are of potential concern for human health.