Introduction into the environment of elements (such as arsenic, cadmium, lead, and mercury) which have a deleterious effect on living organisms when found naturally in only minor amounts (concentrations less than 1.0 milligram per liter) in water or sediment.
Trace elements are inorganic chemicals occurring in small amounts in nature. This web site of the National Water Quality Assessment links to U.S. data, publications, news, and other sites on trace metals, metalloids and radionuclides in water.
Explains the natural and human-affected factors that determine the concentration of contaminants in groundwater, especially where the concentration is different at the surface than at depth, and where pumping varies with time.
Homepage for the Toxic Substances Hydrology Program, which provides scientific information on contaminated sites and on human and environmental health. Links to news, topical information, investigations, meetings, publications, and photos.
Arsenic is a naturally occurring element in rocks, soils, and the waters in contact with them. It is found in ground water as the result of minerals dissolving from weathered rocks and soils. This site links to data, maps, and more.
Information on arsenic in United States ground water largely as a result of minerals dissolving from weathered rocks and soils. Includes links to publications, data, maps, and links to other sites with information on arsenic.
Maps and text (Word or PDF format) and database (Excel or HTML format) for bedrock, forest floor, and mineral soil sampling in Voyageurs National Park, Minnesota to establish the background and baseline geochemistry and terrestrial mercury sources.