Identifying ground-water and evaporated surface-water interactions near a landfill using deuterium,¹⁸oxygen, and chloride, Norman, Oklahoma

By Jamie L. Schlottmann, Martha A. Scholl, and Isabelle M. Cozzarelli

Abstract

The composition of water discharging to a small wetland (the slough) downgradient from a closed municipal landfill was investigated using chloride concentration and enrichment in deuterium and ¹⁸oxygen to determine the source waters for the slough. Potential source waters include native alluvial ground water, shallow recent recharge to the alluvium from precipitation, and leachate-contaminated ground water. Effects of evaporation from the slough on those potential source waters were calculated to determine source waters for the slough.

Deuterium and chloride are enriched in the landfill leachate relative to the native ground water. Deuterium and ¹⁸oxygen have a great range and chloride concentration is low in recent recharge relative to native ground water. The initial water isotopic composition of the slough was estimated based on the range of temperature and humidity conditions under which the water was evaporated. The amount of evaporation of the potential source waters was then estimated by the change in deuterium, ¹⁸ oxygen, and chloride values of the slough from those in potential source waters. Results of calculating evaporation of potential source waters suggest the slough receives primarily uncontaminated native ground water but also some landfill leachate and the contribution from these sources varies over time. One of three slough samples had a suggested initial composition of leachate-contaminated water, which was diluted approximately 70 percent by recent recharge prior to entering the slough. Suggested initial compositions of other two samples included native ground water only.