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Nitrate in groundwater of the United States, 1991-2003

Environmental Science and Technology

By:
, , , and
DOI: 10.1021/es100546y

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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.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Nitrate in groundwater of the United States, 1991-2003
Series title:
Environmental Science and 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