Ecological risk assessment for a mine pit lake, Nevada, USA Sampson, Jennifer R.; Mellott, Ron S.; Pastorok, Robert A.
Closure of an open pit gold mine in central Nevada, USA, will result in cessation of dewatering at the mine and formation of a pit lake. The future pit lake will occur in a desert shrub community and have no surface water inflows or outflows. An ecological risk assessment far the pit lake was conducted as part of an environmental impact statement required for expansion of mine facilities. Because the pit lake does not yet exist, ecological risks were estimated from the results of predictive water quality models and measurement of chemical concentrations in the rock wall of the pit. The exposure of birds and mammals to individual metals through food and water ingestion was estimated on the basis of concentrations of metals in water and bioconcentration factors and through sediment ingestion was estimated from concentrations of metals in wall rock. Exposure estimates, which were expressed as daily rates of intake of individual metals, were compared to no-effects and lowest-effects doses reported in the literature for those metals. Results of the risk assessment demonstrated minimal risks to dabbling ducks from exposure to zinc and no risk to other wildlife from chemical exposures.
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