Volatile Halocarbon Contaminants in the Niagara River and in Lake Ontario

Water samples from 95 stations in Lake Ontario and 16 stations in the lower Niagara River Were analyzed for volatile halocarbons and carbon disulfide. The following contaminants were observed at many stations with their lake-wide means and standard deviations: trichloro-fluoromethane (Freon 11), 249 ± 882 ng · L^?1; methylene chloride, 572 ± 1,826 ng · L^?1; chloroform, 18 ± 92 ng · L^?1; bromodichloromethane, 3 ± 9 ng · L^?1; and tetrachloroethylene, 9 ± 65 ng · L^?1. Eleven other compounds, including carbon disulfide, 1, 1–dichloroethylene, 1,1,1–trichloroethane, carbon tetra-chloride, and tetrachloroethylene were observed at trace levels or absent at most stations. Six compounds were observed in virtually all Niagara River samples and were traceable into the lake. As apparent from the large relative standard deviations for the above, contaminant concentrations varied strongly between stations, indicating areas of contaminant sources. Both industrialized and urban areas, such as Toronto, Hamilton, and the Niagara River, as well as comparatively small tributaries, such as Twelve Mile, Eighteen Mile, and Oak Orchard Creeks, Black River, and the Welland Canal, appear to be sources for several of the observed contaminants.