Nitrate in groundwater of the United States, 1991-2003
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Abstract
An assessment of nitrate concentrations in groundwater in the United States indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high N inputs. During 1991-2003, 5101 wells were sampled in 51 study areas throughout the U.S. as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program. The well networks reflect the existing used resource represented by domestic wells in major aquifers (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations were highest in shallow groundwater beneath agricultural land use in areas with well-drained soils and oxic geochemical conditions. Nitrate concentrations were lowest in deep groundwater where groundwater is reduced, or where groundwater is older and hence concentrations reflect historically low N application rates. Classification and regression tree analysis was used to identify the relative importance of N inputs, biogeochemical processes, and physical aquifer properties in explaining nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that dissolved iron concentrations explained most of the variation in groundwater nitrate concentration, followed by manganese, calcium, farm N fertilizer inputs, percent well-drained soils, and dissolved oxygen. Overall, nitrate concentrations in groundwater are most significantly affected by redox conditions, followed by nonpoint-source N inputs. Other water-quality indicators and physical variables had a secondary influence on nitrate concentrations.
Publication type | Article |
---|---|
Publication Subtype | Journal Article |
Title | Nitrate in groundwater of the United States, 1991-2003 |
Series title | Environmental Science & Technology |
DOI | 10.1021/es100546y |
Volume | 44 |
Issue | 13 |
Year Published | 2010 |
Language | English |
Publisher | ACS Publications |
Publisher location | Washington, D.C. |
Contributing office(s) | California Water Science Center |
Description | 10 p. |
Larger Work Type | Article |
Larger Work Subtype | Journal Article |
Larger Work Title | Environmental Science and Technology |
First page | 4988 |
Last page | 4997 |
Time Range Start | 1991-01-01 |
Time Range End | 2003-12-31 |
Country | United States |
Online Only (Y/N) | N |
Additional Online Files (Y/N) | N |
Google Analytic Metrics | Metrics page |