TY - JOUR
T1 - Impacts of agricultural irrigation recharge on groundwater quality in a basalt aquifer system (Washington, USA)
T2 - A multi-tracer approach
AU - Brown, Kyle B.
AU - McIntosh, Jennifer C.
AU - Rademacher, Laura K.
AU - Lohse, Kathleen A.
N1 - Funding Information:
The Science Foundation Arizona, University of Arizona Space Grant Program, and NSF (EAR-0635685; McIntosh) provided funding for this research. We thank R. Black and S. Embrey of the USGS, Tacoma Office, Washington, as well as C. Adkins and D. Gosch, for their tremendous help with field sampling, and the residents of central Washington for allowing access to sample their wells. We also thank T. Ferre for his input on an earlier version of the manuscript.
PY - 2011/8
Y1 - 2011/8
N2 - Irrigation in semi-arid agricultural regions can have profound effects on recharge rates and the quality of shallow groundwater. This study coupled stable isotopes ( 2, 18O), age-tracers ( 3H, CFCs, 14C), 87Sr/ 86Sr ratios, and elemental chemistry to determine the sources, residence times, and flowpaths of groundwater and agricultural contaminants (e. g. NO 3 -) in the Saddle Mountains Basalt Aquifer in central Washington, USA, where over 80% of the population depend on groundwater for domestic use. Results demonstrate the presence of two distinct types of water: contaminated irrigation water and pristine regional groundwater. Contaminated irrigation water has high NO 3 -concentrations (11-116 mg/l), 87Sr/ 86Sr ratios (0.70659-0.71078) within range of nitrogen-based fertilizers, detectable tritium (2.8-13.4 TU), CFC ages 20-40 years, high δ 18O values (-16.9 to -13.5‰), and ~100 percent modern 14C. Pristine regional groundwater has low NO 3 -concentrations (1-5 mg/l), no detectable tritium (≤0.8 TU), low δ 18O values (-18.9 to -17.3‰) and 14C ages from ~15 to 33 ky BP. Nitrogen and oxygen isotopes of NO 3 -,combined with high dissolved oxygen values, show that denitrification is not an important process in the organic-poor basalt aquifers resulting in transport of high NO 3 - irrigation water to depths greater than 40 m in less than 30 years.
AB - Irrigation in semi-arid agricultural regions can have profound effects on recharge rates and the quality of shallow groundwater. This study coupled stable isotopes ( 2, 18O), age-tracers ( 3H, CFCs, 14C), 87Sr/ 86Sr ratios, and elemental chemistry to determine the sources, residence times, and flowpaths of groundwater and agricultural contaminants (e. g. NO 3 -) in the Saddle Mountains Basalt Aquifer in central Washington, USA, where over 80% of the population depend on groundwater for domestic use. Results demonstrate the presence of two distinct types of water: contaminated irrigation water and pristine regional groundwater. Contaminated irrigation water has high NO 3 -concentrations (11-116 mg/l), 87Sr/ 86Sr ratios (0.70659-0.71078) within range of nitrogen-based fertilizers, detectable tritium (2.8-13.4 TU), CFC ages 20-40 years, high δ 18O values (-16.9 to -13.5‰), and ~100 percent modern 14C. Pristine regional groundwater has low NO 3 -concentrations (1-5 mg/l), no detectable tritium (≤0.8 TU), low δ 18O values (-18.9 to -17.3‰) and 14C ages from ~15 to 33 ky BP. Nitrogen and oxygen isotopes of NO 3 -,combined with high dissolved oxygen values, show that denitrification is not an important process in the organic-poor basalt aquifers resulting in transport of high NO 3 - irrigation water to depths greater than 40 m in less than 30 years.
KW - Agriculture
KW - Groundwater age
KW - Hydrochemistry
KW - Stable isotopes
KW - USA
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U2 - 10.1007/s10040-011-0736-z
DO - 10.1007/s10040-011-0736-z
M3 - Article
AN - SCOPUS:79961097265
SN - 1431-2174
VL - 19
SP - 1039
EP - 1051
JO - Hydrogeology Journal
JF - Hydrogeology Journal
IS - 5
ER -