Volatilization of toxaphene from Lakes Michigan and Superior

The pesticide toxaphene was used extensively on cotton in the southern Unit ed States until its use was restricted in 1982. It was previously reported that the upper Great Lakes have received toxaphene by gas absorption follow ing long-range transport from the south and are currently saturated with re spect to toxaphene. However, the rate of loss of toxaphene from Lakes Michi gan and Superior had been estimated using sparse or estimated data, and thu s, these estimates had high uncertainties. For this investigation, samples were collected to provide extensive data on air, water, and sediment concen trations of toxaphene for the upper Great Lakes for the period 1997-98. The se data were used to calculate the annual an seasonal fluxes of toxaphene f rom water to air and sediment. Lake Superior is 200-1000% saturated with to xaphene, and Lake Michigan is 200-500% saturated. It seems clear that both lakes will outgas toxaphene into the atmosphere for some considerable time in the future, and Lake Superior, because of its generally lower water temp eratures and higher toxaphene concentration, will outgas toxaphene even lon ger than will Lake Michigan.