• Feasibility Studies
• Site Characterization

• Lahontan Reservoir, NV
• Carson River Basin, NV

• U.S. Environmental Protection Agency, Region 9
• University of Toronto
• Nevada Division of State Parks
• CH2M Hill

• Mercury
• Methylmercury

Due to concerns about elevated levels of mercury in fish in the Carson River Basin from Dayton, NV, to the Lahontan Reservoir, the Nevada State Division of Health is advising anglers to not eat fish caught from this part of the river basin. The source of the mercury in this part of the Carson River Basin comes from the erosion of upstream bank sediments that were severely contaminated with mercury during gold mining operations in the late 1800s at the Virginia City Comstock Load in the upper part of the Basin. In response to the growing concern about the mercury contamination in the Basin, USGS scientists in partnership with the U.S. Environmental Protection Agency (USEPA) began an investigation in April 2001 to determine factors affecting the fate and transport of mercury species in Lahontan Reservoir, part of the Carson River Basin. Based on methods developed by the USGS Toxic Substances Hydrology Program's San Francisco Bay studies, USGS scientists are determining the remobilization and discharge of mercury species from sediments of Lahontan Reservoir. The magnitude of the remobilization is estimated by determining the benthic flux of dissolved contaminants from the reservoir’s bottom sediments. In addition, water-column chemistry and mercury methylation/demethylation rates are being determined to provide a scientific basis for remedial actions for the reservoir and watershed, both in terms of water-quality and fisheries resources. Based on these measurements by the USGS research team, a mercury fate and transport model will be constructed for the Lahontan Reservoir by our collaborators at the University of Toronto. This information will then be used by USEPA (Region 9) to assess various remediation strategies aimed at reducing methylmercury production and bioaccumulation in the Reservoir and the river/wetland system downstream.

• Benthic Fluxes of Metals and Nutrients Studies, Lahontan Reservoir, Nevada, Investigation
• New Method for Assessing Bed Sediment Contamination
• Benthic Flux Method Photo Gallery
• Historical Mining Activities Have Been Sources of Trace Elements to Carson River Bottom Sediment
• News Release -- Large Amounts of Sediment and Mercury in Carson River During Flood of January 1997
• Solute Transport Involving Biological Processes in Surface Waters
• Real-Time Water Level Data for the Lahontan Reservoir
• Nevada-Division of Environmental Protection (A health advisory for fish in the Carson River Basin is reported.)
• U.S. Environmental Protection Agency's Fish Consumption Advisory Information

• James Kuwabara, USGS, National Research Program, Menlo Park, CA,
• Mark Marvin-Dipasquale, USGS, National Research Program, Menlo Park, CA,

Kuwabara, J.S., Marvin-Dipasquale, M., Praskins, W., Byron, E., Topping, B.R., Carter, J.L., Fend, S.V., Parchaso, F., and Krabbenhoft, D.P., 2002,

Flux of dissolved forms of mercury across the sediment-water interface in Lahontan Reservoir, Nevada: U.S. Geological Survey Water-Resources Investigations Report 02-4138, 48 p.

Bevans, H.E., Lico, M.S., and Lawrence, S.J., 1998,

Water quality in the Las Vegas Valley Area and the Carson and Truckee River Basins, Nevada and California, 1992-96,: U.S. Geological Survey Circular 1170, updated March 19, 1998.

Hoffman R.J., 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, 6 p.

Hoffman R.J., Thomas K.A., 2000,

Methylmercury in Water and Bottom Sediment Along the Carson River System, Nevada and California, September 1998: U.S. Geological Survey Water-Resources Investigations Report 00-4013, 17 p.

Kuwabara, J.S., Berelson, W.M., Balistrieri, L.S., Woods, P.F., Topping, B.R., Steding, D.J., and Krabbenhoft, D.P., 2000,

Benthic flux of metals and nutrients into the water column of Lake Coeur d'Alene, Idaho---Report of an August, 1999, pilot study: U.S. Geological Survey Water-Resources Investigations Report 00-4132, 74 p.

Marvin-DiPasquale, M., Agee, J., McGowan, C., Oremland, R.S., Thomas, M., Krabbenhoft, D., and Gilmour, C.C., 2000,

Methyl-mercury degradation pathways--A comparison among three mercury-impacted ecosystems: Environmental Science and Technology, v. 34, no. 23, p. 4908-4916.

Topping, B.R., Kuwabara, J.S., Parchaso, F., Hager, S.W., Arnsberg, A.J., and Murphy, F., 2001,

Benthic flux of dissolved nickel into the water column of South San Francisco Bay: U.S. Geological Survey Open-File Report 01-89, 50 p.

Other Studies Using the Same Methods to Determine the Benthic Flux of Metals

• Assessing Bottom Sediments as a Source of Mercury Contamination, Camp Far West Reservoir, California
• Lake Coeur d'Alene Remediation Assessment
• Nickel Cycling in the South San Francisco Bay

USGS Studies Related to Mercury Remediation

• Yolo Bypass Studies, Yolo Bypass, Sacramento, CA Cache Creek, CA
• Bear-Yuba Watersheds Interagency Abandoned Mine Lands Project, Bear-Yuba Watersheds, California
• Evaluation of the Effectiveness of Remediation Dredging--The Fox River Deposit N Demonstration Project, Lower Fox River, near Kimberly, Wisconsin

Mercury Information

• USGS Mobile Atmospheric Mercury Laboratory Makes an Impact
• Effect Of Mercury on Aquatic Ecosystems
• USGS Mercury Research Laboratory
• Mercury Contamination of Aquatic Ecosystems: U.S. Geological Survey Fact Sheet FS-216-95
• Other USGS Mercury Activities

San Francisco Bay Information

• Varied Human Influences on Estuaries -- San Francisco Bay, California
• Access USGS - San Francisco Bay and Delta