Stable isotopes and chemistry of water as source indicators of aquifer recharge and contamination

Abstract

A multiuse area, 15 miles south of Tucson, Arizona, was selected to test a water-pollution source assessment technique emphasizing the combined study of stable isotopes of water, major anions and cations, trace elements, pH, specific conductance, and water temperature. Computer-based analytical techniques were developed to identify data patterns indicating effects of recharge sources. A large amount of water chemistry data were generated, and relationships between poor-quality water and potential contamination sources were defined. The range in isotopic ratios along the study transect suggested that tracing surface-water recharge by its isotopic signature is possible, if density and frequency of sampling are sufficient. A pattern showing increasingly heavy δ¹⁸O values with decreasing distance from a tailings pond supported inferences based on chemical data that tailings pond leakage may be contaminating downgradient ground water. From experience gained in applying the techniques, suggestions for improving the methods are presented.