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The Reston Stable Isotope Laboratory conducts research on the use of isotope ratio measurements in studies of water resources and environmental quality.

Analyses of hydrogen, carbon, nitrogen, oxygen, and sulfur stable isotope-ratios of water, rock, and biological samples have contributed to understanding water-supply sustainability, groundwater-surface-water interactions, paleoclimate history, biologic cycling of nutrients, ground-water contamination, and natural remediation. Members of the Reston Stable Isotope Laboratory (RSIL) conduct research on the use of isotope-ratio measurements in studies of water resources and environmental quality. One objective of the RSIL is to develop new techniques for isotopic analysis of oxygen-, sulfur-, carbon-, hydrogen-, and nitrogen- bearing materials. New analytical techniques expand the range of tools available for studying the movement of those elements in hydrologic and biogeochemical systems. 

Noble gases, measured by the RSIL, are a suite of chemically inert elements that are universally present at trace levels in air and water on earth. As their concentrations are not modified by chemical reactions or microbial activity, they are powerful indicators of physical processes, including temperature of recharge, gas exchange, diffusion, and transport phenomena. By measuring their concentrations and isotope ratios, we can infer groundwater residence time, recharge temperature, recharge conditions, and gas diffusion processes in the subsurface. 

Tritium concentrations, measured by our collaborative, RSIL-satellite Menlo Park Isotope Laboratory, are used to determine groundwater ages, investigate ground-water contamination, explore groundwater-surface-water interaction, and study a host of other hydrologic phenomena.