The Nevada Test Site (NTS) was used for underground nuclear tests before the 1960\u27s. Yucca Mountain in southern Nevada has been proposed as the site for the first high-level radioactive waste repository in the U.S. Because groundwater is a likely medium for transporting radio-nuclides to the accessible environment, determining the nature and path of groundwater movement through the aquifers at the NTS and Yucca Mountain is a critical task for assessing the risks and the future performance of the repository. In this study, systematic investigations of major ion and trace [mainly rare earth element (REE)] element geochemistry were conducted on different components of groundwater flow systems in southern Nevada, including groundwaters from representative springs and wells, aquifer rocks that comprise major aquifers, secondary minerals from fractures and veins in the aquifer rocks, and solutions from water/rock interactions. The geochemical data collected in this study help us characterize and compare major ion and REE signatures in different sample media, study changes in trace elements and REEs resulting from water/rock interactions, and develop a geochemical framework to trace groundwater from sources and predict groundwater flow paths and fluid mixing at the Nevada Test Site and the Yucca Mountain region of southern Nevada. The study also enhances our geologic and hydrologic understanding of trace element and REE geochemistry in the groundwater flow systems
