Chlorinated Hydrocarbons in the Surface Microlayer and Subsurface Water of the Niagara River, 1985-86

Abstract The surface microlayer of the Niagara River at Niagara-on-the-Lake was sampled 34 times in 1985-86, and was shown to contain PCBs, chlorobenzenes and chlorinated hydrocarbons at concentrations generally up to 40 times greater than concentrations 1n subsurface water. Organisms which spend part or all of their lives at the air-water interface are thus likely to be at increased risk relative to subsurface water exposure. A small “spill” of PCBs 1n the river on July 29, 1986 was only detected in the surface micro-layer, and not in subsurface water. On this date, concentrations of PCBs in the surface microlayer were up to 6,400 times larger than concentrations in the subsurface water, and 1t appeared that the “spill” was downstream of Niagara Falls and the Whirlpool. Despite such high concentrations of chlorinated hydrocarbons in the surface microlayer, at no time during this study did the microlayer contribute significantly, relative to subsurface water, to the loading (i.e., amounts) of these chemicals from the Niagara River to Lake Ontario.