Mercury studies at Sulphur Bank Mercury Mine and Clear Lake, California Active
The abandoned Sulphur Bank Mercury Mine on the shores of Clear Lake in Northern California has been designated as a "Superfund Site" by the U.S. Environmental Protection Agency (EPA). This means that the EPA has determined that the area is contaminated by hazardous waste and requires cleanup because it poses a risk to human health and/or the environment. One of the chief contaminants at the site is mercury (Hg). Methylmercury (MeHg) is a highly toxic form of mercury that becomes magnified as it works its way up the food chain. To help the EPA address the problem, the USGS has been asked to study the presence and spread of methylmercury at the Clear Lake site.
Background
The Sulphur Bank Mercury Mine is an inactive mercury mine located on a 200-acre property on the southeast shores of Clear Lake. The mine site includes a flooded open pit mine and approximately 3,000,000 cubic yards of contaminated mine waste. Contaminants from the Sulphur Bank Mercury Mine have been detected in lake sediments in nearby areas. Previous work at Clear Lake has shown that primary production (algae growth) driven by an excessive richness of nutrients is a key driver to methylation of mercury and its introduction into the food web. Getting a better understanding of mercury cycling in Clear Lake will depend on understanding nutrient cycling and its effects on the depletion of dissolved oxygen in the water column and surface sediment, which increases mercury methylation.
In addition, a research effort on nutrient cycling in Clear Lake by the University of California, Davis (UCD) began in 2018 in association with the Blue Ribbon Committee for the Rehabilitation of Clear Lake, affording the USGS the opportunity to integrate their work with the ongoing UCD study.
Objectives
The overarching goal of the planned research is to improve understanding of the relationships between contaminants derived from Sulphur Bank Mercury Mine with concentrations of mercury in sediment, water, and fish tissue in Clear Lake. A related goal is to determine the proportion of methylmercury in the food web of Clear Lake that is derived from the Sulphur Bank Mercury Mine using geochemical and isotopic methods. A third goal is to further examine and develop the relationships between various dissolved and particulate mercury fractions and optical properties in the water column, such that these relationships can be leveraged to develop monitoring platforms that will generate data that can inform future efforts. A fourth goal is to develop a model for mercury cycling in Clear Lake that is a useful management tool for the EPA and other stakeholders for testing the potential benefits of reducing levels of MeHg bioaccumulation in the Clear Lake food web.
Science Plan
The planned work is divided into eight tasks:
- Technical assistance (USGS scientists with expertise in several areas to assist the EPA)
- Prepare Quality Assurance Project Plan and Field Sampling Plans
- Water sampling and analysis
- Solids sampling and analysis
- Biological sampling and analysis
- Mercury isotope analysis
- Evaluating water column mercury methylation rates
- Modeling of mercury cycling in Clear Lake
Timeline and Deliverables
A six-year project is planned. The USGS will release data on ScienceBase throughout the project as it becomes available. Interpretive reports are planned for Fiscal Year 2025.
Mercury stable isotopes in biota, sediment, groundwater, and waste piles, Clear Lake area, Lake County, California, 2019-2022
Mercury in fishes from Clear Lake, California, 2019 and 2020 (ver. 2.0, February 2022)
The Geochemistry of Mercury and Other Constituents in Redox Manipulated Sediment cores from Clear Lake, Lake County, California
Surface-Water Geochemistry of Mercury, Methylmercury, Nutrients, and other Constituents in Clear Lake, Lake County, California, July 2019
Below are partners associated with this project.
- Overview
The abandoned Sulphur Bank Mercury Mine on the shores of Clear Lake in Northern California has been designated as a "Superfund Site" by the U.S. Environmental Protection Agency (EPA). This means that the EPA has determined that the area is contaminated by hazardous waste and requires cleanup because it poses a risk to human health and/or the environment. One of the chief contaminants at the site is mercury (Hg). Methylmercury (MeHg) is a highly toxic form of mercury that becomes magnified as it works its way up the food chain. To help the EPA address the problem, the USGS has been asked to study the presence and spread of methylmercury at the Clear Lake site.
Background
The Sulphur Bank Mercury Mine is an inactive mercury mine located on a 200-acre property on the southeast shores of Clear Lake. The mine site includes a flooded open pit mine and approximately 3,000,000 cubic yards of contaminated mine waste. Contaminants from the Sulphur Bank Mercury Mine have been detected in lake sediments in nearby areas. Previous work at Clear Lake has shown that primary production (algae growth) driven by an excessive richness of nutrients is a key driver to methylation of mercury and its introduction into the food web. Getting a better understanding of mercury cycling in Clear Lake will depend on understanding nutrient cycling and its effects on the depletion of dissolved oxygen in the water column and surface sediment, which increases mercury methylation.
In addition, a research effort on nutrient cycling in Clear Lake by the University of California, Davis (UCD) began in 2018 in association with the Blue Ribbon Committee for the Rehabilitation of Clear Lake, affording the USGS the opportunity to integrate their work with the ongoing UCD study.Objectives
The overarching goal of the planned research is to improve understanding of the relationships between contaminants derived from Sulphur Bank Mercury Mine with concentrations of mercury in sediment, water, and fish tissue in Clear Lake. A related goal is to determine the proportion of methylmercury in the food web of Clear Lake that is derived from the Sulphur Bank Mercury Mine using geochemical and isotopic methods. A third goal is to further examine and develop the relationships between various dissolved and particulate mercury fractions and optical properties in the water column, such that these relationships can be leveraged to develop monitoring platforms that will generate data that can inform future efforts. A fourth goal is to develop a model for mercury cycling in Clear Lake that is a useful management tool for the EPA and other stakeholders for testing the potential benefits of reducing levels of MeHg bioaccumulation in the Clear Lake food web.
Science Plan
The planned work is divided into eight tasks:
- Technical assistance (USGS scientists with expertise in several areas to assist the EPA)
- Prepare Quality Assurance Project Plan and Field Sampling Plans
- Water sampling and analysis
- Solids sampling and analysis
- Biological sampling and analysis
- Mercury isotope analysis
- Evaluating water column mercury methylation rates
- Modeling of mercury cycling in Clear Lake
Timeline and Deliverables
A six-year project is planned. The USGS will release data on ScienceBase throughout the project as it becomes available. Interpretive reports are planned for Fiscal Year 2025.
- Science
- Data
Mercury stable isotopes in biota, sediment, groundwater, and waste piles, Clear Lake area, Lake County, California, 2019-2022
Samples were collected from Clear Lake, California from 2019-2022 by the U.S. Geological Survey (USGS) California Water Science Center, the USGS Forest and Rangeland Ecosystem Science Center (FRESC), the US Environmental Protection Agency, and EA Engineering Science and Technology Inc. to assess the extent and cycling of legacy mercury (Hg) contamination from Sulphur Bank Mine. Samples of waste roMercury in fishes from Clear Lake, California, 2019 and 2020 (ver. 2.0, February 2022)
Comma-separated values (.csv) file containing data related to mercury in fishes collected from Clear Lake, California.The Geochemistry of Mercury and Other Constituents in Redox Manipulated Sediment cores from Clear Lake, Lake County, California
Clear Lake, located within the Coast Range west of California's Central Valley, is the largest natural freshwater lake contained fully within the state and geologically is considered to be the oldest lake in North America. Clear Lake is popular for recreation and provides critical habitat to a wide variety of fish and bird species. Water quality in Clear Lake is degraded by both by mercury contamiSurface-Water Geochemistry of Mercury, Methylmercury, Nutrients, and other Constituents in Clear Lake, Lake County, California, July 2019
Clear Lake is a 180 km2 freshwater lake located in the California Coast Range, approximately 120 km northwest of Sacramento. The lake supports a wide variety of fish and bird species and is a very popular sport-fishing destination. However, fish consumption advisories associated with mercury (Hg) contamination exist for several popular recreational species. The lake is comprised of three main regi - Partners
Below are partners associated with this project.