Mercury TMDL

A statewide mercury TMDL was developed to estimate the proportions of mercury contributions to water and fish from wastewater discharges, in-state air sources, and out-of-state air sources, and to calculate appropriate reductions needed. Click HERE for more information on mercury in North Carolina.

Documents:

Final NC Mercury TMDL (updated 10/16/12)
Post TMDL Wastewater Permitting Strategy (updated 9/12/12)
Reduction Options for Nonpoint Sources

Supplemental Information:

Information on Mercury in North Carolina

Mercury is a naturally occurring element. However, human activities have increased the amount of mercury that is available in the atmosphere, in soils and sediments, and in various water bodies. Anthropogenic mercury originates largely from air sources, such as coal-fired power plants and incinerators. Mercury in air falls as wet or dry deposition directly into waters, or onto adjacent lands, where it is washed off into surface waters when it rains. Some mercury is discharged in wastewater, although the amounts are usually very small compared to air sources. Most of the mercury found in the environment is in the form of metallic mercury and inorganic mercury compounds.

Mercury in Fish

Microorganisms in soils and sediments convert inorganic mercury to methylmercury. In this form, it is taken up by aquatic plants and animals. Fish that eat them build up, or bioaccumulate, methylmercury in their bodies. The highest concentrations of methylmercury are generally found in large fish that eat other fish. In North Carolina, the highest concentrations are usually found in largemouth bass and bowfin, and especially where mercury methylation rates are high.