Effects of human-induced alteration of groundwater flow on concentrations of naturally-occurring trace elements at water-supply wells

AbstractThe effects of human-induced alteration of groundwater flow patterns on concentrations of naturally-occurring trace elements were examined in five hydrologically distinct aquifer systems in the USA. Although naturally occurring, these trace elements can exceed concentrations that are considered harmful to human health. The results show that pumping-induced hydraulic gradient changes and artificial connection of aquifers by well screens can mix chemically distinct groundwater. Chemical reactions between these mixed groundwaters and solid aquifer materials can result in the mobilization of trace elements such as U, As and Ra, with subsequent transport to water-supply wells. For example, in the High Plains aquifer near York, Nebraska, mixing of shallow, oxygenated, lower-pH water from an unconfined aquifer with deeper, confined, anoxic, higher-pH water is facilitated by wells screened across both aquifers. The resulting higher-O2, lower-pH mixed groundwater facilitated the mobilization of U from solid aquifer materials, and dissolved U concentrations were observed to increase significantly in nearby supply wells. Similar instances of trace element mobilization due to human-induced mixing of groundwaters were documented in: (1) the Floridan aquifer system near Tampa, Florida (As and U), (2) Paleozoic sedimentary aquifers in eastern Wisconsin (As), (3) the basin-fill aquifer underlying the California Central Valley near Modesto (U), and (4) Coastal Plain aquifers of New Jersey (Ra). Adverse water-quality impacts attributed to human activities are commonly assumed to be related solely to the release of the various anthropogenic contaminants to the environment. The results show that human activities including various land uses, well drilling, and pumping rates and volumes can adversely impact the quality of water in supply wells, when associated with naturally-occurring trace elements in aquifer materials. This occurs by causing subtle but significant changes in geochemistry and associated trace element mobilization as well as enhancing advective transport processes

Assessing ground-water vulnerability to contamination: providing scientifically defensible information for decision makers

Throughout the United States increasing demands for safe drinking water and requirements to maintain healthy ecosystems are leading policy makers to ask complex social and scientific questions about how to assess and manage our water resources. This challenge becomes particularly difficult as policy and management objectives require scientific assessments of the potential for ground-water resources to become contaminated from anthropogenic, as well as natural sources of contamination

Preliminary estimates of residence times and apparent ages of ground water in the Chesapeake Bay watershed, and water-quality data from a survey of springs /

"September 1998."Shipping list no.: 99-0027-P.Includes bibliographical references (p. 52-55).Mode of access: Internet

Estimating net drawdown resulting from episodic withdrawals at six well fields in the coastal plain physiographic province of Virginia /

Twenty-two maps on 7 folded leaves in envelope.Shipping list no.: 94-0062-P.Includes bibliographical references (p. 19).Mode of access: Internet

Dairy-Impacted Wastewater Is a Source of Iodinated Disinfection Byproducts in the Environment

Iodinated disinfection byproducts (DBPs) are among the most toxic DBPs, but they are not typically measured in treated water. Iodinated DBPs can be toxic to humans, and they also have the potential to affect aquatic communities. Because of the specific use of iodine and iodine-containing compounds in dairies, such livestock operations can be a potential source of iodinated DBPs in corresponding receiving water bodies. DBPs [trihalomethanes (THMs), including iodinated THMs] were measured within dairy processing facilities (milking and cheese manufacturing) and surface waters that receive dairy-impacted effluents [either directly from the dairy or through wastewater treatment plants (WWTPs)] in three areas of the United States (California, New York, and Wisconsin). Iodo-THMs comprised 15–29% of the total THMs in surface water near WWTP effluents that were impacted by dairy waste and 0–100% of the total THMs in samples from dairy processing facilities

Selected characteristics of stormflow and base flow affected by land use and cover in the Chickahominy River Basin, Virginia, 1989-91 /

Shipping list no.: 95-0221-P.Includes bibliographical references (p. 37).Mode of access: Internet

A retrospective analysis on the occurrence of arsenic in ground-water resources of the United States and limitations in drinking-water-supply characterizations /

Includes bibliographical references (p. 20-21).Mode of access: Internet

Occurrence of selected radionuclides in ground water used for drinking water in the United States : a reconnaissance survey, 1998 /

"Prepared in cooperation with the U.S. Environmental Protection Agency, Office of Ground Water and Drinking Water."Includes bibliographical references (p. 21-23).Mode of access: Internet