Nitrate source history for Livermore, California using environmental isotopes, noble-gases, and major ions
AuthorMoore, Keara Bevin.
Nitrates -- Environmental aspects -- California.
Groundwater -- California -- Livermore Valley.
Committee ChairEkqurzel, Brenda
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThis investigation of a nitrate contaminated groundwater basin in Livermore, California, demonstrates that nitrate isotope data are especially effective in determining contaminant sources when paired with other chemical and isotopic analyses. Major ion data distinguish three water types. Low-nitrate wastewater predominates in the northwest region, while two flowpaths with distinct nitrate sources originate in the southeast. Along the eastern flowpath, δN values >10%o 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, mobilizes a significant local nitrate source, bringing groundwater concentrations to >50 mg/L. The low 615N value (3.l%) in this location implicates synthetic fertilizer. In addition to these anthropogenic sources, relatively high natural nitrate background levels (15- 20 mg/L) are found in deep wells with residence times greater than 50 years.
Degree ProgramHydrology and Water Resources