My research is concerned broadly with the use of stable isotopes, primarily hydrogen, carbon and oxygen, to examine the dynamics of hydrological systems and associated geochemical problems. I perform studies in the identification and quantification of ground-water recharge, discharge, surface-water/ground-water interaction, redox processes in contaminated aquifers, as well as source identification of stray methane gas in drinking water wells. I develop new sample- preparation techniques in the laboratory including inlet systems for continuous- flow isotope- ratio analytical techniques , such as EA, TC/EA, GPI, Gasbench, GCC, TC/GCC, and TIC/TOC and publish Sandard Operating Procedures in the U.S. Geological Survey Techniques and Methods. [...]