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DISTRIBUTION OF SEDIMENT MERCURY CONCENTRATIONS IN THE HUMBOLDT RIVER WATERSHED
Citation:
Hall, R. K., S. Ellsworth, P. Husby, C. Rosamond, H. Powell, A. Lincoff, AND D T. Heggem. DISTRIBUTION OF SEDIMENT MERCURY CONCENTRATIONS IN THE HUMBOLDT RIVER WATERSHED. Presented at Historic and Current Mining Activities Conference, San Francisco, CA, November 6-10, 2000.
Impact/Purpose:
The primary objectives of this research are to:
Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;
Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;
Develop and validate multivariate models based on quantification studies;
Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;
Complete an initial draft (potentially web based) of a national landscape condition assessment.
This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.
Description:
In 1998 the United States Environmental Protection Agency (USEPA) required the mining industry to list all releases to the environment exceeding the Toxic Release Inventory (TRI) reporting threshold. Mining activities in Arizona, California and Nevada accounted for approximately 66% (2.3 billion pounds) of the total releases nationally. Of the 57 facilities in these three states reporting toxic releases, 36 (63%) are in the State of Nevada, with 22 (38%) located in the Humboldt River watershed. Mercury releases occur from weathering of waste rock and mercury is one of the primary compounds released into the air from ore processing facilities. Mining facilities within the Humboldt reported releasing approximately 14,000 lbs of mercury into the atmosphere. Mercury was analyzed in water and stream sediment samples from 35 randomly selected sites as part of the USEPA Region IX Humboldt River Watershed Regional environmental Monitoring and Assessment Program (R-EMAP) project. Mercury m stream sediment was detected at 24 (68%) of the sites wiffi concentrations ranging from 0.07 - 1.50 mg/kg. The Lowest Effects Level for aquatic organism for mercury of 0.2 mg/kg was exceeded at 6 (17%) sites located in tributaries to the Humboldt River west of Winnemucca, and the Carlin Trend area and in tributaries to the Mary, s River, Rock Creek and Reese River. Mercury in the water column was below the detection limit of 0. I ug/L in all 35 samples. This study indicates mercury is wide spread throughout the watershed in low to moderate levels.
The highest concentrations are associated with general geology and mining.