2000 GSA Annual Meeting -- Reno, Nevada
2000 GSA Annual Meeting -- Reno, Nevada
Author(s): BALISTRIERI, Laurie S., USGS, Univ. of WA, Box 357940, Seattle, WA 98195, balistri@usgs.gov; TEMPEL, Regina N., Dept. of Geological Sciences, Univ. of NV, Reno, Reno, NV 89557; STILLINGS, Lisa L., USGS, Univ. of NV, Reno, Reno, NV 89557
Keywords: pit lakes, metals
Dexter Pit Lake began to form in 1990 after cessation of open-pit mining of the gold-silver deposits at Tuscarora. Wall rocks contain elevated concentrations of As and other toxic elements that could be mobilized into the pit lake waters. We sampled the water column of Dexter Pit Lake nearly every month over a 2-year period to obtain detailed physical, chemical, and biological information. We use this information to assess and model processes affecting the composition of the pit lake water. The data indicate that the important processes are thermal stratification that isolates bottom water in the pit during summer and fall, inputs of dilute surface water into the epilimnion of the pit lake in spring and concentrated groundwater into the hypolimnion of the pit lake in winter, evaporation, re-suspension of particles, mineral dissolution and precipitation, solution complexation, adsorption, early diagenesis of organic matter within the sediments, and benthic fluxes of dissolved elements that are mobilized during diagenesis. This talk will illustrate these processes using time and depth data collected from a HYDROLAB (temperature, pH, dissolved oxygen, and conductivity) and from discrete water samples (major cations, anions, nutrients, and minor ions). Identification of these processes provides a framework for developing a quantitative model that describes the seasonal cycling and distribution of elements in pit lakes.
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