Monitoring Mercury and Suspended Sediment in the Carson River, Nevada: Continuation of a Unique, Long-Term Dataset Active
The USGS Nevada Water Science Center (NVWSC), in collaboration with the U.S. Environmental Protection Agency (EPA), monitored mercury in the Carson River from 1997 to 2013. To preserve this long-term dataset, NVWSC is monitoring mercury concentrations and suspended sediment in the Carson River above and below Lahontan Reservoir. NVWSC also is beginning process-based sampling above and below Lahontan Reservoir.
NVWSC will be collecting samples under conditions known to be critical to the environmental fate and transport of mercury for the sites. To evaluate chemical conditions known or thought to be important to the methylation of mercury, the USGS will begin process-based sampling. Process-based sampling includes:
- Reactive mercury
- Dissolved and Particulate Organic Carbon
- Nutrients
- Sulfate
- Chloride
BACKGROUND
An estimated 7,500 tons of mercury were lost to the Carson River during the 40-year period of intense mining of gold and silver from the Comstock Mining district in the late 1800s1. The mercury, used as part of the amalgamation process to extract the gold and silver from the crushed ore, was incorporated in mill tailings that eventually eroded and was redeposited as bank material and bed sediment lower in the Carson River system. Past studies indicated that mercury is largely transported with suspended sediment2 with 90 percent trapped by Lahontan Reservoir3.
In 1990, the EPA listed over 50 miles of the lower Carson River system on the National Priorities List as the Carson River Mercury Site4. In collaboration with the EPA, the NVWSC collected and analyzed surface-water samples and suspended sediment for mercury and methylmercury from 1997 to 2013 at two sites on the Carson River, about 4 miles upstream and 1-mile downstream of Lahontan Reservoir, respectively. The USGS-EPA dataset represents one of the longest continuous records of mercury and methylmercury for any riverine system2.
References
1 Smith, G.A., Tingley, J.V., 1943. The history of the Comstock Lode, 1850-1920. Univ. Nev. Bull. 37, 305 pp.
2 Morway, E.D., Thodal, C.E., Marvin-DiPasquale, Mark, 2017, Long-term trends of surface-water mercury and methylmercury concentrations downstream of historic mining within the Carson River watershed: Environmental Pollution, vol. 229, p. 1006-1018.
3 Hoffman, R.J. and Taylor, R.L., 1998, Mercury and suspended sediment, Carson River Basin, Nevada: Loads to and from Lahontan Reservoir in flood year 1997 and deposition in reservoir prior to 1983: U.S. Geological Survey Fact Sheet FS-001-98.
4 United States Environmental Protection Agency, 2018, Carson River Mercury Site, Dayton, Nevada, Cleanup Activities, accessed January 28, 2018.
- Overview
The USGS Nevada Water Science Center (NVWSC), in collaboration with the U.S. Environmental Protection Agency (EPA), monitored mercury in the Carson River from 1997 to 2013. To preserve this long-term dataset, NVWSC is monitoring mercury concentrations and suspended sediment in the Carson River above and below Lahontan Reservoir. NVWSC also is beginning process-based sampling above and below Lahontan Reservoir.
Sources/Usage: Public Domain. View Media DetailsMap of mercury sampling sites on the Carson River, Nev. (Public domain.) NVWSC will be collecting samples under conditions known to be critical to the environmental fate and transport of mercury for the sites. To evaluate chemical conditions known or thought to be important to the methylation of mercury, the USGS will begin process-based sampling. Process-based sampling includes:
- Reactive mercury
- Dissolved and Particulate Organic Carbon
- Nutrients
- Sulfate
- Chloride
BACKGROUND
An estimated 7,500 tons of mercury were lost to the Carson River during the 40-year period of intense mining of gold and silver from the Comstock Mining district in the late 1800s1. The mercury, used as part of the amalgamation process to extract the gold and silver from the crushed ore, was incorporated in mill tailings that eventually eroded and was redeposited as bank material and bed sediment lower in the Carson River system. Past studies indicated that mercury is largely transported with suspended sediment2 with 90 percent trapped by Lahontan Reservoir3.
In 1990, the EPA listed over 50 miles of the lower Carson River system on the National Priorities List as the Carson River Mercury Site4. In collaboration with the EPA, the NVWSC collected and analyzed surface-water samples and suspended sediment for mercury and methylmercury from 1997 to 2013 at two sites on the Carson River, about 4 miles upstream and 1-mile downstream of Lahontan Reservoir, respectively. The USGS-EPA dataset represents one of the longest continuous records of mercury and methylmercury for any riverine system2.References
1 Smith, G.A., Tingley, J.V., 1943. The history of the Comstock Lode, 1850-1920. Univ. Nev. Bull. 37, 305 pp.
2 Morway, E.D., Thodal, C.E., Marvin-DiPasquale, Mark, 2017, Long-term trends of surface-water mercury and methylmercury concentrations downstream of historic mining within the Carson River watershed: Environmental Pollution, vol. 229, p. 1006-1018.
3 Hoffman, R.J. and Taylor, R.L., 1998, Mercury and suspended sediment, Carson River Basin, Nevada: Loads to and from Lahontan Reservoir in flood year 1997 and deposition in reservoir prior to 1983: U.S. Geological Survey Fact Sheet FS-001-98.
4 United States Environmental Protection Agency, 2018, Carson River Mercury Site, Dayton, Nevada, Cleanup Activities, accessed January 28, 2018.
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