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Water: Mercury Maps

Mercury Maps—National Application

  • Evaluate benefits of technology-based mercury air emission control standards;
  • Perform Total Maximum Daily Load (TMDL) analyses for multiple watersheds
  • Coordinate air emission, water quality, and wastewater permitting programs
  • Estimated Percent Reduction in Air Deposition Load Necessary to Meet New Methylmercury Criterion In Watersheds with No Other Significant Mercury Sources

    * States currently use water column concentration-based mercury water quality standards and would need to adopt fissue tissue-based target levels in order to use this approach for mercury TMDLs. Additional reductions would be required to meet EPA national and most state fish advisory threshold concentrations, which are often set below the methylmercury criterion.

    Note: Watersheds highlighted yellow have 'significant' mercury sources other than deposition, defined as where the total estimated load from Publicly Owned Treatment Works (POTWs) and pulp and paper mills is greater than 5% of estimated waterbody delivered mercury at a typical air deposition load (10 g/km2/yr), and/or where mercury cell chlor-alkali facilities, mercury mines, or significant past producer gold mines are present. See text of report for data sources for point source dischargers and mines.

    Source: National Listing of Fish and Wildlife Advisories (NLFWA) Mercury Fish Tissue Database (June 2001). The national Mercury Maps analysis is based on the 22,000 georeferenced records of fish tissue mercury concentrations in 35 states (west coast and states in the eastern two thirds of the U.S.) in the National Listing of Fish and Wildlife Advisories (NLFWA) Fish Tissue Database available at the time of the analysis (June, 2001). Substantially more fish tissue data is currently available. This national analysis screens watersheds that contain potentially significant, but unquantified, runoff and effluent loads from mercury mines, large-producer gold mines, and mercury-cell chlor-alkali facilities. Watersheds are also eliminated when the total screening level effluent load estimates for municipal wastewater treatment plants and pulp and paper mills are above five percent of the estimated waterbody-delivered air deposition load.

  • Georeferenced and Non-Georeferenced Fish Samples
  • Considered Significant when Present in the Watershed and Considered Significant when Estimated Effluent Load below 5% Air Deposition Load

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