Graduation date: 2009The use of semi-volatile organic compounds (SOCs) as molecular markers to identify the contributions of regional and long-range atmospheric transport, as well as current and historic sources, and contaminant deposition in remote ecosystems of the Western U.S. was investigated. Trans-Pacific air masses influenced by Siberian biomass burning events had elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) and the historic use pesticides dieldrin and alpha-HCH, while air masses influenced by regional fires in the Pacific Northwestern U.S. had enhanced concentrations of PAHs and the current-use pesticides dacthal and endosulfan. This suggests that previously deposited SOCs, such as pesticides, revolatilize to the atmosphere during forest fires. In addition, forest soils collected from a burned area in the Pacific Northwestern U.S. had significantly lower SOC concentrations (34 to 100 %) than soils collected from an un-burned area separated only by a two lane road. This confirms that SOCs re-volatilize and/or degrade from soils and vegetation during the burning process. The chiral signatures of alpha-HCH in air masses at three sites in the Pacific Northwestern U.S. indicated that the boundary layer has a non-racemic alpha-HCH signature likely due to re-volatilization of alpha-HCH from the Pacific Ocean and that the free troposphere is a source of racemic alpha-HCH. Racemic alpha-HCH was also associated with Asian and trans-Pacific air masses. Racemic cis and trans-chlordane in Pacific Northwestern U.S. air masses indicated that U.S. urban areas continue to be a source of chlordane to the atmosphere. The deposition of non-racemic alpha-HCH in seasonal snowpack in continental Western U.S. national park high elevation ecosystems reflected regional transport, while the high latitude, Alaskan national parks were influenced by long-range atmospheric transport of racemic alpha-HCH. The chiral signature of alpha-HCH in fish collected from high elevation and high latitude ecosystems in Western U.S. national parks reflected the chiral signature of the seasonal snowpack in the lake catchment. This indicates that the fish in these ecosystems do not enantioselectively biotransform alpha-HCH. Racemic cis-chlordane was measured in seasonal snowpack and lake sediments in Sequoia National Park due to the high population density surrounding the park and the past use of chlordane as a termiticide in urban areas. Non-racemic cis-chlordane was measured in sediment collected from Rocky Mountain National Park because this park receives chlordane due to re-volatilization from regional agricultural soil
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