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Title: Sources of groundwater nitrate revealed using residence time and isotope methods

Abstract

Nitrate concentrations approaching and greater than the maximum contaminant level (MCL) are impairing the viability of many groundwater basins as drinking water sources. Nitrate isotope data are effective in determining contaminant sources, especially when combined with other isotopic tracers such as stable isotopes of water and tritium-helium ages to give insight into the routes and timing of nitrate inputs to the flow system. This combination of techniques is demonstrated in Livermore, CA, where it is determined that low nitrate reclaimed wastewater predominates in the northwest, while two flowpaths with distinct nitrate sources originate in the southeast. Along the eastern flowpath, {delta}{sup 15}N values greater than 10{per_thousand} indicate that animal waste is the primary source. Diminishing concentrations over time suggest that contamination results from historical land use practices. The other flowpath begins in an area where rapid recharge, primarily of low-nitrate imported water (identified by stable isotopes of water and a tritium-helium residence time of less than 1 year), mobilizes a significant local nitrate source, bringing groundwater concentrations up to 53 mg NO{sub 3} L{sup -1}. In this area, artificial recharge of imported water via local arroyos increases the flux of nitrate to the regional aquifer. The low {delta}{sup 15}N valuemore » (3.1{per_thousand}) in this location implicates synthetic fertilizer. In addition to these anthropogenic sources, natural nitrate background levels between 15 and 20 mg NO{sub 3} L{sup -1} are found in deep wells with residence times greater than 50 years.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
886919
Report Number(s):
UCRL-JRNL-207110
Journal ID: ISSN 0883-2927; APPGEY; TRN: US0604144
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Applied Geochemistry
Additional Journal Information:
Journal Volume: 21; Journal ID: ISSN 0883-2927
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPES AND RADIATION SOURCES; 58 GEOSCIENCES; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; ANIMALS; CONTAMINATION; DRINKING WATER; LAND USE; NITRATES; STABLE ISOTOPES; VIABILITY; WASTES; WATER

Citation Formats

Moore, K B, Ekwurzel, B, Esser, B K, Hudson, G B, and Moran, J E. Sources of groundwater nitrate revealed using residence time and isotope methods. United States: N. p., 2004. Web.
Moore, K B, Ekwurzel, B, Esser, B K, Hudson, G B, & Moran, J E. Sources of groundwater nitrate revealed using residence time and isotope methods. United States.
Moore, K B, Ekwurzel, B, Esser, B K, Hudson, G B, and Moran, J E. 2004. "Sources of groundwater nitrate revealed using residence time and isotope methods". United States. https://www.osti.gov/servlets/purl/886919.
@article{osti_886919,
title = {Sources of groundwater nitrate revealed using residence time and isotope methods},
author = {Moore, K B and Ekwurzel, B and Esser, B K and Hudson, G B and Moran, J E},
abstractNote = {Nitrate concentrations approaching and greater than the maximum contaminant level (MCL) are impairing the viability of many groundwater basins as drinking water sources. Nitrate isotope data are effective in determining contaminant sources, especially when combined with other isotopic tracers such as stable isotopes of water and tritium-helium ages to give insight into the routes and timing of nitrate inputs to the flow system. This combination of techniques is demonstrated in Livermore, CA, where it is determined that low nitrate reclaimed wastewater predominates in the northwest, while two flowpaths with distinct nitrate sources originate in the southeast. Along the eastern flowpath, {delta}{sup 15}N values greater than 10{per_thousand} indicate that animal waste is the primary source. Diminishing concentrations over time suggest that contamination results from historical land use practices. The other flowpath begins in an area where rapid recharge, primarily of low-nitrate imported water (identified by stable isotopes of water and a tritium-helium residence time of less than 1 year), mobilizes a significant local nitrate source, bringing groundwater concentrations up to 53 mg NO{sub 3} L{sup -1}. In this area, artificial recharge of imported water via local arroyos increases the flux of nitrate to the regional aquifer. The low {delta}{sup 15}N value (3.1{per_thousand}) in this location implicates synthetic fertilizer. In addition to these anthropogenic sources, natural nitrate background levels between 15 and 20 mg NO{sub 3} L{sup -1} are found in deep wells with residence times greater than 50 years.},
doi = {},
url = {https://www.osti.gov/biblio/886919}, journal = {Applied Geochemistry},
issn = {0883-2927},
number = ,
volume = 21,
place = {United States},
year = {Thu Oct 07 00:00:00 EDT 2004},
month = {Thu Oct 07 00:00:00 EDT 2004}
}