Tritium/3He dating of shallow groundwater - ScienceDirect H, half-life of 12.43 years (Unterweger and others, 1980)) has provided an excellent tracer of young waters. If we assume that no tritiogenic ~He is lost by diffusion across the groundwater table, the tritium/3He age of groundwater can be calculated by r = Tl/2/ln 2 In1 + -~He/3H 3 where r = tritium/~He age in years. This determination is independent of the initial tritium concentration.
USGS Groundwater Dating Lab Tritium input to ground water has occurred in a series of spikes following periods of atmospheric testing of nuclear devices that began in 1952 and reached a maximum in 1963-1964. Tritium measurements alone can be used to locate the depth of the mid-1960s bomb peak, but, because of radioactive decay, many samples may need to be collected and analyzed today to locate its position. Schlosser and others 1988, 1989 reported 3H/ 3He dating of shallow ground water sampled from wells screened at multiple levels at Liedern/Bocholt, Germany. The 3H from 1963-64 atmospheric nuclear-bomb testing was clearly evident in the tritiogenic 3He at a depth of 5 to 10 meters in the saturated zone.
Dating of shallow groundwater comparison of the transient. In systems younger than the mid-1960s, the bomb peak will not be present due to radioactive decay. The comparison of 3H/3He, CFC-11, CFC-12, and 85Kr age dating techniques in shallow groundwater shows close agreement between results obtained by the individual methods. This agreement can be attributed to aerobic conditions, permeable sand, nearly complete gas confinement, and low dispersion found on the Delmarva Peninsula.
Basics of 3H/3He dating Although initial H input to ground water and may be used to determine the position of the mid-1960s bomb peak in recharge areas. Because 3 He is a gas, the application of the tritium/ 3 He method to dating of groundwater depends strongly on the degree of confinement of 3 He trit in the groundwater. The confinement of 3 He trit is mainly determined by the ratio of advection to dispersion in water parcels moving away from the water table.