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ORGANIC POLLUTANT DEPOSITION TO THE SIERRA NEVADA (CALIFORNIA, USA) SNOWPACK AND ASSOCIATED LAKE AND STREAM ECOSYSTEM
Citation:
Landers, D H., J L. Stoddard, AND D. Muir. ORGANIC POLLUTANT DEPOSITION TO THE SIERRA NEVADA (CALIFORNIA, USA) SNOWPACK AND ASSOCIATED LAKE AND STREAM ECOSYSTEM. Presented at First International Conference on Trans-Pacific Transport of Atmospheric Contaminants, Seattle, WA, July 27-29, 2000.
Description:
High elevation ecosystems in the western USA and Canada are receiving deposition of persistent organic pollutants (POPs) that presumably originate in the USA as well as outside its borders. In April 1992 we obtained paired snowpack samples from each of two watersheds located in the Sierra Nevada mountains: Wolverton (2207 m.a.s.l.) and Mosquito Flats (3495 m.a.s.l.). In addition to the elevation differences, sites are located on opposite sides of the Sierra Nevada divide (Wolverton - West and Mosquito Flats - East). The purpose of this research was to characterize snowpack in late winter with regard to POP concentrations and loadings and to obtain some idea of the effect of elevation and the Sierra Nevada divide on contaminant concentrations. Clean field sampling techniques were used. Extractions from large volume snow samples were analyzed for a broad POP suite using capillary gas chromatography with electron capture detection.
Endosulfan and hexachlorocyclohexanes were the major constituents in the snowpack, especially in samples from Mosquito Flats. Samples from Wolverton had 4-times lower levels of HCH than those from Mosquito Flats, higher amounts of chlordanes and DDT, and similar endosulfan levels. Toxaphene levels were higher at Mosquito Flats (226 pg/L) than at Wolverton (110 pg/L). Both locations had similar levels of PCBs (1060 and 1260 pg/L at Mosquito Flats and Wolverton, respectively). Levels of low molecular weight PAHs (naphthalene, fluorene and phenanthrene) in snow were in the range of 0.8 to 27 ng/L. The sample from Wolverton had greater amounts of high molecular weight PAHs such as benzopyrenes, chrysene and benxofluoranthenes than Mosquito Flats. Results indicate that both of these sites are receiving POP deposition and that concentrations of the more volatile constituents (e.g.,. HCH, Endosulphan) appear to increase with elevation, consistent with data from the Canadian Rockies. This suggests that the cold vapor distillation phenomenon is functioning with elevation gradients in the Sierra. High elevation lakes in the Sierra receive as much as 99% of hydrologic inputs from snowmelt. This dominance of the annual hydrologic cycle by snow, coupled with cold vapor distillation, creates a high probability that POPs are loading to Sierran aquatic systems at reasonably high rates.