Radiogenic age dating of groundwater. Groundwater age-dating for water resource characterization
Accurate analysis of dissolved Neon allows determination of excess air concentration; analysis of the heavy noble gases, Krypton and Xenon allows a plegatines online dating calculation of the noble gas recharge temperature; an estimate of accumulated radiogenic 4-Helium can be made from total dissolved helium.
Expertise in the use of noble gas tracers: This increased reliance on the groundwater in concert with the strict regulation on water quality has led to a need by water managers and regulators to understand: Radiogenic helium 4 4Herad has been used in numerous studies as a tracer of groundwater age in the range of — years.
When mixing is ignored, as it often is, tritium alone can overestimate the mean age of the modern less than 50 year age component. Construction of this facility was funded by LLNL.
We have measured 4Herad along shallow groundwater flow paths at a variety of hydrogeologically distinct sites and postulate its use for dating groundwater as young as years. Characterization of mean groundwater age and recharge temperature through the use of noble gas techniques provides information that is relevant to answering these questions and that is not accessible through traditional hydrogeologic approaches.
The 4Herad release rate at the Ontario site is extraordinarily similar to sites in Tennessee, Nebraska, and Germany in spite of major hydrogeologic differences.
Groundwater samples may or may not contain tritium above the method detection limit. Laboratory release experiments conducted by sequentially heating the aquifer solids, measuring the amount of 4He released, and then extrapolating release rates to the in situ temperature agree well with the field results and suggest that diffusion from aquifer solids is the source of 4He rad.
Both observations and modeling suggest that 4He may be useful as a groundwater dating tool over a range of tens to hundreds of years. Less model-dependent than tritium age dating: High throughput and rapid turn-around: The facility is staffed by Ph.
A solute transport model suggests that the aquifer solids are the source of 4He rad as vertical fluid velocities are too great to allow upward diffusion of 4He rad from the underlying shield rocks.
The natural and non-natural processes that impart a dissolved gas composition to recharging groundwater are complex and variable.
Source of radiogenic helium 4 in shallow aquifers: