Fingerprinting of ground water by ICP-MS. Progress report, July 1, 1995--September 30, 1995

Understanding the groundwater flow regime in south-central Nevada and the Death Valley region of California is of particular concern for both the Nevada Test Site and Yucca Mountain region because of the potential of contamination of the regional groundwater with radionuclides. Previous investigations indicated that groundwater in the region is recharged in the north and subsequently flows towards the south, eventually discharging partially to the Muddy River system as well as within Ash Meadows National Wildlife Refuge and Death Valley National Park. We have examined the previous conclusions concerning the groundwater flow regime using the rare earth elements (REE). In general we see that the heavy REEs (HREES) (ie., Gd - Lu), for a groundwater mixture of these proportions, closely resembles the Ash Meadows groundwater. A major depletion is, however, recorded for the fight REEs (LREES) (ie., La - En) in this mixture. These results suggest that although the Ash Meadows groundwaters are most likely a mixture of Spring Mountain and Pahranagat Valley groundwater as discussed by previous investigators, there must also be a small component of groundwater from the perched aquifers of the Nevada Test Site that contributes to the discharge ofthe Ash Meadows springs in order for these waters to aquire their REE signature