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Groundwater age is usually defined as the time between recharge at the water table to the time when groundwater was sampled.Groundwater age estimates are based on concentrations of environmental tracers (i.e., tracers derived from the atmosphere, as opposed to artificial tracers) in groundwater.Rapidly recharged groundwater is less likely to be depleted over time though it can be more vulnerable to surface activities leading to nitrate or pesticide contamination.Because water quality is a concern over the entire state, many groundwater age studies in Nebraska have utilized dating methods that focus on groundwater 45,000 years has been observed.Once this water reaches the water table, it moves though the aquifer.The time it takes to travel to a given location, known as the groundwater age, can vary from days to thousands of years.In addition to dating waters, -decay of natural U- and Th-series elements in rocks and sediments.Mass transfer between aquifer solids and ground water occurs, resulting in a relationship between ground-water travel time (or contact time) and the He as a quantitative tracer of ground-water travel times (e.g.
Groundwater transit times are strongly linked to the ratio of groundwater recharge rate and groundwater storage capacity (commonly represented as saturated thickness times porosity).These different sources of He to the atmosphere (Wuest et al., 1992), and will similarly lead to underestimates of ground-water ages (Schlosser et al., 1989).Analytical uncertainties usually result in errors in age estimates of less than 10% (Solomon et al., 1993).Once water enters an aquifer, it becomes isolated from the atmosphere, and it carries a CFC signature (a distinctive chemical composition) as it travels through the aquifer.This signature reflects the atmospheric concentration when the water was at the surface.
A high altitude continental paleotemperature record derived from noble gases dissolved in groundwater from the San Juan Basin, New Mexico, Stute, M., Forster, M., Frischkorn, H., Serejo, A., Clark, J. Schlosser, P., Dunkle-Shapiro, S., Stute, M., Aeschbach--Hertig, W., Plummer, L. Tritium/He dating of young groundwater: chronologies for environmental records. C., Jambon, A., de Marsily, G., and Schlosser, P., 1998. Age of irrigation water from the eastern Snake River Plain Aquifer, South-Central Idaho - implications for elevated nitrate concentrations.