APPLICATION OF BORON ISOTOPE RATIOS FOR IDENTIFYING NITRATE CONTAMINATION SOURCES IN THE GROUNDWATER OF AVRA VALLEY, ARIZONA

Leenhouts, James Merrell; Basset, R. L.; Maddock, Thomas, III

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Author

Leenhouts, James Merrell
Basset, R. L.
Maddock, Thomas, III

Affiliation

Department of Hydrology & Water Resources, The University of Arizona

Issue Date

1994-06

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This title from the Hydrology & Water Resources Technical Reports collection is made available by the Department of Hydrology & Atmospheric Sciences and the University Libraries, University of Arizona. If you have questions about titles in this collection, please contact repository@u.library.arizona.edu.

Abstract

The stable isotopes of the conservative element boron, 11B and 1°B, have been employed as co- migrating isotopic tracers to determine the origin of nitrate observed in groundwater from a large capacity (2500 gpm) irrigation well in the Avra Valley of southeastern Arizona. The isotopic ratios of the conservative element, boron, provided an identifying signature for various nitrate rich source waters. Additional chemical parameters were also examined to corroborate the isotopic indications. Findings of this investigation indicate that most of the nitrate observed in groundwater from well CMID 18 at the beginning of the 1993 irrigation season was due to municipal wastewater contamination. As the irrigation season progressed, an increasing proportion of nitrate was contributed by irrigation return flow from neighboring agricultural fields.

Series/Report no.

Technical Reports on Hydrology and Water Resources, No. 94-010

Sponsors

We would like to thank the many people who also contributed to the success of this project. Dr. Grey Wilson provided insight and advice whenever called upon. Dr. David Esposito shared with us the data, knowledge and samples which helped launch this research. Robert Condit and the entire staff at the Cortaro -Marana Irrigation District were always helpful and eagerly provided us with needed advice and access to records. A special thanks to Dr. Herman Bouwer and Dr. Bert Clements with the Agricultural Research Station in Phoenix, Arizona. Research and development was supported in part by the U.S. Water Conservation Lab, U.S. Department of Agriculture, Phoenix, Arizona. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the United States Government.

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