The study also found that nitrate is a continuing human-health concern in many shallow aquifers across the Nation that are sources of drinking water. In agricultural areas, more than one in five shallow, private wells contained nitrate at levels above the EPA drinking water standard. The quality and safety of water from private wellswhich are a source of drinking water for about 40 million peopleare not regulated by the Federal Safe Drinking Water Act and are the responsibility of the homeowner.
Because nitrate can persist in groundwater for years and even decades, nitrate concentrations are likely to increase in aquifers used for public drinking-water supplies during at least the next decade, as shallow groundwater with high nutrient concentrations moves downward into deeper aquifers.
"Strategies designed to reduce nutrient inputs on the land will improve the quality of water in near-surface parts of aquifers; however, decades may pass before quality improves in deeper parts of the aquifer, which serve as major sources for public-supply wells," said Neil Dubrovsky, USGS hydrologist and lead scientist on this study. "Unfortunately, similar time delays for improvements are expected for streams that receive substantial inputs of groundwater."
A variety of sources can contribute nutrients to surface and groundwater, such as wastewater and industrial discharges, fertilizer and manure applications to agricultural land, runoff from urban areas, and atmospheric sources. USGS findings show that nutrient sources and resul
|Contact: Kara Capelli|
United States Geological Survey