Use of Chemical and Isotopic Identifiers to Characterize a Uranium Contaminated Groundwater Plume in New Mexico

Schatz, Mitchell

Use of Chemical and Isotopic Identifiers to Characterize a Uranium Contaminated Groundwater Plume in New Mexico

Tuesday, February 23, 2016: 11:15 a.m.

Mitchell Schatz , Civil Engineering, University of New Mexico, Albuquerque, NM

Jose Cerrato , Civil Engineering, University of New Mexico, Albuquerque, NM

Bruce Thomson, Ph.D. , Dept. of Civil Engineering, University of New Mexico, Albuquerque, NM

Groundwater in shallow aquifers near Milan, New Mexico is the major source of water for agriculture and human consumption. Since 1983, groundwater in the region has high levels of uranium, selenium, nitrates, and vanadium, and determined to be too contaminated for human use, and other sources of water have been provided to the region. Isotopic and chemical identifiers were used to help distinguish contaminants derived from anthropogenic and natural occurring sources near a former uranium mining and milling site near Milan. Private wells near the uranium disposal site were sampled in the fall of 2015 and compared to mill-derived groundwater from a former uranium mill site and known natural groundwater sources in the area. Principal Component Analysis was used to display similarities and differences in groundwater chemistry for sampled wells, natural sources, and uranium mill site groundwater. Several of the private wells had similar levels of contaminants as mill-derived water. Activity ratios (ARs) for uranium-234 and uranium-238 were compared to naturally derived groundwater, where recent studies show mill-derived groundwater ARs are near secular ratios of 1 and natural derived groundwater have ARs values above 2. Leaching of the mill tailings involved the use of sulfuric acid and other leaching agents. Dissolved sulfate in mill-derived groundwater was enriched with sulfur-34 whereas natural occurring groundwater showed a depletion of sulfur-34. Other stable isotopes were used to determine sources of recharge in the aquifers. The use of chemical and isotopic identifiers in this study help to determine that groundwater contaminants in private wells downgradient from the milling site were most likely derived from the mill site dewatering activities and not the natural occurring contaminants from Morrison formations in the San Mateo Creek basin aquifers.

Mitchell Schatz, Civil Engineering, University of New Mexico, Albuquerque, NM

Mitchell Schatz received a Bachelor of Science (Environmental Science) from the University of Washington in 2009 and is currently working on a Master of Science at the University of New Mexico. His interests include groundwater contamination and remediation.

Jose Cerrato, Civil Engineering, University of New Mexico, Albuquerque, NM

Jose Cerrato’s research interest is related to biogeochemical processes at the interface of water and energy that affect the cycle of metals and radionuclides in the environment. He leads the E-H2O Research Group which applies spectroscopy, microscopy, aqueous chemistry, and molecular biology tools for the study of complex environmental interactions.

Bruce Thomson, Ph.D., Dept. of Civil Engineering, University of New Mexico, Albuquerque, NM

Bruce Thomson is Director of the Water Resources Program and Professor of Civil Engineering at the University of New Mexico. His research interests focus on water chemistry and treatment. He has a Ph.D. from Rice University in Environmental Science and Engineering.