Excess 234U: An aging effect in confined waters
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Cited by (38)
Use of U-isotopes in exploring groundwater flow and inter-aquifer leakage in the south-western margin of the Great Artesian Basin and Arckaringa Basin, central Australia
2018, Applied GeochemistryCitation Excerpt :Where the uranium activity concentrations (or more commonly 234U/238U activity ratios) behave conservatively along groundwater flow paths variability can potentially identify inter-aquifer mixing, identify source waters and determine the relative proportions of source waters (Dabous and Osmond, 2001; Herczeg et al., 1996; Osmond et al., 1974; Paces et al., 2002; Paces and Wurster, 2014; Rosenthal and Kronfeld, 1982). Uranium isotope variations have also been used to determine groundwater flow rates by either the 234U excess decay model (Guttman and Kronfeld, 1982; Henderson et al., 1999; Kronfeld et al., 1975; Kronfeld and Rosenthal, 1981) or alternatively, by determining the progressive augmentation by aquifer processes (Ivanovich et al., 1991; Schaffhauser et al., 2014). Other groundwater studies found that U activities depended more upon the groundwater redox conditions (Andrews and Kay, 1983), radioelement distribution from diverse vadose zone inputs and weathering conditions (Kronfeld et al., 2004; Méjean et al., 2016; Post et al., 2017; Tricca et al., 2001), extent of water-rock interactions (Andrews et al., 1982) and stabilisation by the formation of uranium complexes (Herczeg et al., 1988; Jurgens et al., 2010).
Uranium isotopes in groundwater from the continental intercalaire aquifer in Algerian Tunisian Sahara (Northern Africa)
2009, Journal of Environmental RadioactivityCitation Excerpt :The Continental Intercalaire aquifer has a wide range of uranium contents (0.006–3.39 ppb) decreasing from the recharge area on the west (Algerian Atlas) to the discharge area of the east (Chott Djérid/Gulf of Gabès) and very scattered 234U/238U activity ratios (0.4–15.4) decreasing along this main W-E flow path. 234U/238U activity ratio have already been reported for deep groundwater and have been explained either by a long history of high surface area interaction between a water of low uranium solubility and an aquifer rock with relatively higher concentration of uranium (factor of 1000) (Kronfeld et al., 1975) or by an elevated temperatures that may cause rock–water isotopic re-equilibration to occur (Kramer and Kharaka, 1986). High 234U/238U activity ratios are often observed in large confined aquifer with steady long-term flow systems such Continental Intercalaire aquifer.
Chapter 10 Uranium- and Thorium-Series Radionuclides in Marine Groundwaters
2008, Radioactivity in the EnvironmentCitation Excerpt :This application is based on the fact that 234U, unlike 238U, can be mobilized to sediment pore water via recoil of 234Th and subsequent decay of the 234Th. This process accounts for greater-than-unity 234U/238U activity ratios in terrestrial groundwaters (e.g. Hussain and Krishnaswami, 1980; Kronfeld et al., 1975; Hussain and Lal, 1986; Osmond and Cowart, 1992; Porcelli, this volume) and 234U/238U activity ratios in marine sediment pore waters that are elevated relative to the seawater value of 1.149 (Cochran and Krishnaswami, 1980; Maher et al., 2004). Maher et al. (2004, 2006) have used high-resolution mass-spectrometric measurements of U concentrations and 234U/238U ratios in sediment pore water to determine low-temperature bulk and mineral dissolution rates of sediment over time-scales of ∼500,000 ky.
Rates of silicate dissolution in deep-sea sediment: In situ measurement using <sup>234</sup>U/<sup>238</sup>U of pore fluids
2004, Geochimica et Cosmochimica ActaCitation Excerpt :Rocks and minerals maintain the equilibrium activity ratio of unity unless they have been disturbed recently by physical or chemical processes such as comminution or leaching; thus unlike other radiogenic isotope systems used in geochemistry, rocks are nearly uniform in 234U/238U. Fine-grained solids, however, do not quantitatively retain intermediate decay products of uranium because of α-recoil effects (Bonotto and Andrews, 1993; Fleischer, 1980, 1982a, 1988; Kigoshi, 1971; Kronfeld et al., 1975; Ku, 1965). The α-recoil effect causes the 234U/238U ratio of fine-grained solids (<∼250 μm in diameter) to depart from the equilibrium value resulting in excess 234U in the interstitial fluid phase.
Uranium series isotopes in the Avon Valley, Nova Scotia
2004, Journal of Environmental Radioactivity
- 1
Present Address: Department of Geophysics and Planetary Sciences, Tel-Aviv University.
- 2
Permanent Address: Max-Planck-Institut für Kernphysik, Heidelberg.