| Toxaphene is a highly chlorinated pesticide that was heavily used as a pesticide on cotton in the southern U.S. from the 1950–1970's and is now being found at high concentrations in Great Lakes' sediment, water, fish, and air samples. This thesis describes our efforts to find out if toxaphene is being deposited into or volatilizing from Lakes Michigan and Superior and to determine if toxaphene is being transported to the Great Lakes from the southern United States. This thesis also describes the identification of chlorothalonil and Dacthal, two chlorinated pesticides that are still in use in the Great Lakes region, as highly concentrated contaminants in air and precipitation samples from around the Great Lakes.; To quantitate air-water exchange, we analyzed atmospheric samples paired with water samples from over Lakes Michigan and Superior. Toxaphene was found to be volatilizing from Lakes Superior and Michigan during 1997 and 1998. Our results indicate that both lakes will outgas toxaphene into the atmosphere for some considerable time into the future and that Lake Superior, because of its generally lower water temperature and higher toxaphene concentrations, will outgas toxaphene even longer than will Lake Michigan.; We implemented a nation-wide toxaphene air-sampling network in order to determine if toxaphene is being transported to the Great Lakes from the southern United States. We established sampling sites in Lubbock, Texas; Rohwer, Arkansas; Bloomington, Indiana; and Sleeping Bear Dunes, Michigan. The sampling sites listed in decreasing concentration were: Arkansas, Texas, Indiana, and Michigan. From the concentration and back trajectory data, we calculated source probabilities, which indicate where air trajectories with high toxaphene concentrations had resided most often. These data clearly show that Arkansas and nearby states are a source of toxaphene to the Great Lakes region.; In addition, we conducted a qualitative search of Great Lakes atmospheric samples for compounds not previously known to be present. Gas chromatographic mass spectrometry in full scan mode was used to identify peaks. This study concluded with the identification and quantitation of chlorothalonil and Dacthal, two pesticides presently used in the Great Lakes region, but not measured there before. |
