Advanced sampling and analytical methods are readily accessible and affordable, providing abundant geochemical and isotope data for high spatial resolution and high frequency time series. Groundwater Geochemistry and Isotopes provides the theoretical understanding and interpretive methods needed by students, researchers, and practitioners to apply isotopes and geochemistry in groundwater studies and contains a useful chapter presenting the basics of sampling and analysis. This text teaches the thermodynamic basis and principal reactions involving the major ions, gases, and isotopes during groundwater recharge, weathering and redox evolution. Subsequent chapters apply these principles in hands-on training for dating young groundwaters with tritium and helium and ancient systems with radiocarbon, radiohalides and noble gases, and for tracing reactions of the major contaminants of concern in groundwaters. Groundwater Geochemistry and Isotopes presents the basics of environmental isotopes and geochemistry and provides readers with a full understanding of their use in natural and contaminated groundwater..