Tritium fallout in southern Australia and its hydrologic implications

Allison, G.B.; Holmes, J. W.; Hughes, M.W.

doi:10.1016/0022-1694(71)90041-2

Cited by 11 publications

(1 citation statement)

References 17 publications

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“…In any one year, maximum 3H concentrations in rainfall occur in spring, and minimum 3H concentrations occur in winter. An early summer peak has also been observed at southern hemisphere stations [Allison et al, 1971]. Chlorine 36 has the advantage that its half-life (301,000 _+ 2000 years [Browne and Firestone, 1986]) is much longer than that of 3H (12.4 years [Unterweger et al, 1980]), and so the signature has not been attenuated through radioactive decay.…”

Section: ½( Z) = C Z)mentioning

confidence: 99%

Unsaturated zone tritium and chlorine 36 profiles from southern Australia: Their use as tracers of soil water movement

Cook¹,

Jolly²,

Leaney³

et al. 1994

Water Resources Research

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In this paper we present seven unsaturated zone profiles of 36C1 and three 3H profiles from southern Australia. All profiles show single peaks corresponding to high radionuclide fallout from nuclear testing in the 1950s and 1960s. The profiles are used to estimate rates of water movement leading to recharge of the groundwater. Among these profiles is the first profile on. which high concentrations of 36C1 have been found below a 2-m d,e•pth. In this profile, øH and 36C1 peaks coincide. In six of the seven profiles, total øoC1 fallout was found to be between 1.2 and 2.4 x 10 •2 atoms m -2, and is of similar magnitude to that found at similar latitudes in the northern hemisphere. Comparisons of soil water fluxes estimated with 3H, 36C1, and chloride are briefly discussed. of soil water movement in arid areas [Norris et al., 1987; Phillips et al., 1988; Walker et al., 1992; Scanlon, 1992]. In all of these cases, however, most of the 36C1 was confined to the upper 2 m of soil profile, where evapotranspiration complicates soil water movement. In this paper we present 3H and 36C1 profiles from low to moderate rainfall (300-700 mm yr -•) areas of South Australia. in particular, we present the first deep (> !0 m) profile on which both 3H and 36C1 have been measured. Soil water fluxes estimated using 3H and 36C1 profiles are compared. Where measurements have Paper number 94WR00161. 0043-1397/94/94WR-00161 $05.00 not been made on the same profile, comparisons of soil water fluxes inferred from the bomb tracers can be compared with those inferred from a reference tracer, chloride. Theory Tracing Soil Water Movement In a recent review of recharge estimation in arid regions, Gee and Hillel [1988] concluded that techniques based on conventional water balance methods are likely to yield large errors. This is because most approaches rely on estimates of evapotranspiration, the errors of which usually exceed the magnitude of the recharge flux being estimated. Also, in areas where water tables are deep, piezometric techniques axe inapplicable because the unsaturated zone buffers the response to seasonal rainfall. Furthermore, where recharge rates are low, insufficient displacement of artificial tracers occurs over the period of measurement to give useful results. It is for these reasons that much of the recent effort on recharge estimation in arid and semiarid regions has focused on the use of environmental tracers [Allison, 1988]. The most useful natural tracers of soil water movement in these areas are chloride, 3H, and 36CI [Walker et al., !991]. Chloride as a Tracer When water containing chloride percolates into a soil that is subject to water loss by transpiration, then, under steady state, piston flow, the chloride concentration of the soil water increases monotonically through the root zone [Gardner, 1967]. If the water table is sufficiently deep, the chloride concentration below the root zone will be constant with depth. If the water table is shallower, a diffusion profile will form between the bottom of the root zone and ...

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Section: ½( Z) = C Z)mentioning

confidence: 99%