Uranium series disequilibrium in river sediments and waters: the significance of anomalous activity ratios

Plater, Andrew J.; Ivanovich, Μ.; Dugdale, R.E.

doi:10.1016/0883-2927(92)90029-3

Cited by 114 publications

(61 citation statements)

References 30 publications

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“…This elevated ratio, in the stratigraphically uppermost sample, may be a result of the uptake of U from 234 U enriched surficial pore water or significant 234 Th adsorption (e.g. Plater et al, 1992;Osmond and Ivanovich, 1992;Vigier et al, 2005). Another possibility is the incomplete removal of secondary clay or other secondary minerals during sample processing.…”

Section: Wilkawillina Sediment 234 U-238 U Disequilibriamentioning

confidence: 99%

“…The uranium-series (U-series) isotopes are a valuable tool for deriving the timescales of weathering and erosion processes (e.g., Plater et al, 1992;Scott et al, 1992;Vigier et al, 2001;Dequincey et al, 2002;Chabaux et al, 2003;Granet et al, 2007;Dosseto et al, 2008a;Dosseto et al, 2008b;Chabaux et al, 2008;Vigier and Bourdon, 2011). Recently, developed a method for dating the formation age of finegrained sediments, in other words, the time elapsed to present day since physical weathering of source rock to a threshold grain size (≤ ~50 µm), termed the 'comminution age' Lee et al, 2010;Handley et al, in press).…”

Section: Introductionmentioning

confidence: 99%

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Considerations for U-series dating of sediments: Insights from the Flinders Ranges, South Australia

Handley¹,

Turner²,

Dosseto³

et al. 2013

Chemical Geology

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Uranium isotope ratios have been determined for the fine-grained detrital fraction of Pleistocene Wilkawillina valley-fill sediments, four local Proterozoic bedrock samples and fine-grained aeolian material from a sand dune deposit of the Flinders Ranges, South Australia. The aim was to quantify the comminution age, i.e. the time elapsed since physical weathering of the bedrock, and residence time of the valley-fill sediments and to place tighter constraints on input parameters for the comminution age calculation. Despite using two independent approaches for determination of the recoil lost fraction of 234U from the sediment (weighted geometric and surface area estimates), samples fail to produce realistic comminution ages and hence, residence times. The issues involved in the ability to determine sediment comminution ages are discussed. The (234U/238U) activity ratio of the local bedrock is not in secular equilibrium, despite the bedrock being much older than 1Ma, i.e. the timeframe for 234U and 238U to reach secular equilibrium in a closed system. Using the average Flinders Ranges bedrock (234U/238U) ratio instead of an assumed (234U/238U) activity ratio of unity for the source would significantly reduce calculated residence times. This result warrants concern for future studies using the comminution approach for which a secular equilibrium source (234U/238U) activity ratio is assumed. Significant input of aeolian material may modify the measured (234U/238U) activity ratios. Such input may be more tightly constrained in future studies using rare earth element and radiogenic isotopic data. Future comminution studies would benefit from further consideration of the importance of 1) leaching lost 234U from source rock and bulk sediment samples, 2) wind deposition of fine-grained material and 3) the appropriateness and robustness of sample pre-treatment procedures. AbstractUranium isotope ratios have been determined for the fine-grained detrital fraction of Pleistocene Wilkawillina valley-fill sediments, four local Proterozoic bedrock samples and fine-grained aeolian material from a sand dune deposit of the Flinders Ranges, South Australia. The aim was to quantify the comminution age, i.e. the time elapsed since physical weathering of the bedrock, and residence time of the valley-fill sediments and to place tighter constraints on input parameters for the comminution age calculation. Despite using two independent approaches for determination of the recoil lost fraction of 234 U from the sediment (weighted geometric and surface area estimates), samples fail to produce realistic comminution ages and hence, residence times. The issues involved in the ability to determine sediment comminution ages are discussed. The ( 234 U/ 238 U) activity ratio of the local bedrock is not in secular equilibrium, despite the bedrock being much older than 1 Ma, i.e. the timeframe for 234 U and 238 U to reach secular equilibrium in a closed system. Using the average Flinders Ranges bedrock ( 234 U/ 238 U) ratio instead of an ass...

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Section: Wilkawillina Sediment 234 U-238 U Disequilibriamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Considerations for U-series dating of sediments: Insights from the Flinders Ranges, South Australia

Handley¹,

Turner²,

Dosseto³

et al. 2013

Chemical Geology

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“…However, Baston et al (1994) reported that in the presence of high concentrations of organic degradation products at neutral pH, significant reduction in uranium sorption was observed and K d values of U(VI) were two orders of magnitude lower than those at pH 12. Plater et al (1992) reported that the complexation of uranium with DOM in mobile river sediments appeared to increase the mobilization of uranium.…”

Section: Introductionmentioning

confidence: 99%

“…colloids or sediments) or immobile (host rock), thereby increasing or reducing the mobility of the complexes (Plater et al, 1992). Organic matter may sorb on the mineral surfaces to compete with soluble actinides species for sorption sites, hence reducing sorption of the actinides.…”

Section: Introductionmentioning

confidence: 99%

Actinide Sorption in Rainier Mesa Tunnel Waters from the Nevada Test Site

Zhao¹,

Zavarin²,

Leif³

et al. 2007

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The sorption behavior of americium (Am), plutonium (Pu), neptunium (Np), and uranium (U) in perched Rainier Mesa tunnel water was investigated. Both volcanic zeolitized tuff samples and groundwater samples were collected from Rainier Mesa, Nevada Test Site, NV for a series of batch sorption experiments. Sorption in groundwater with and without the presence of dissolved organic matter (DOM) was investigated.Am(III) and Pu(IV) are more soluble in groundwater that has high concentrations of DOM. The sorption K d for Am(III) and Pu(IV) on volcanic zeolitized tuff was up to two orders of magnitude lower in samples with high DOM (15 to 19 mg C/L) compared to samples with DOM removed (< 0.4 mg C/L) or samples with naturally low DOM (0.2 mg C/L). In contrast, Np(V) and U(VI) sorption to zeolitized tuff was much less affected by the presence of DOM. The Np(V) and U(VI) sorption K d s were low under all conditions. Importantly, the DOM was not found to significantly sorb to the zeolitized tuff during these experiment.The concentration of DOM in groundwater affects the transport behavior of actinides in the subsurface. The mobility of Am(III) and Pu(IV) is significantly higher in groundwater with elevated levels of DOM resulting in potentially enhanced transport. To accurately model the transport behavior of actinides in groundwater at Rainier Mesa, the low actinide K d values measured in groundwater with high DOM concentrations must be incorporated in predictive transport models.

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“…For natural uranium, the 235 U/ 238 U activity ratio has a constant value of 0.046, while the 234 U/ 238 U activity ratio is variable. The variation in the 234 U/ 238 U ratio is due to natural causes in many waters (Riotte and Chabaux, 1999;Plater et al, 1992), soil (Lowson and Short, 1988;Lowson et al, 1986;Hansen and Stout, 1968;Stuckless et al, 1977;Rosholt et al, 1966), sediment and uranium ores of different geographical origin (Richter et al, 1999). The mechanism of such variation is preferential leaching of 234 U compared with 238 U from the solid phase, caused by radiation damage of the crystal lattice upon alpha decay of 238 U, oxidation of insoluble tetravalent 234 U to soluble hexavalent 234 U during decay, and alpha recoil of 234 Th (and its daughter 234 U) into the solution phase.…”

Section: Introductionmentioning

confidence: 99%

Variation in the uranium isotopic ratios²³⁴U/²³⁸U,²³⁸U/total-U and²³⁴U/total-U in Indian soil samples: Application to environmental monitoring

et al. 2012

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The uranium isotopes 238 U, 235 U and 234 U are found naturally in the environment.238 U and 235 U are parent nuclides of two independent decay series of isotopes, while 234 U is a member of the 238 U decay chain. When decay series occur in a closed system the series tends to reach, with time, the state of secular equilibrium in which the activities of all series members are equal to the activity of its first nuclide. The activity ratio 234 U/ 238 U in natural uranium may vary as a consequence of decay chain disequilibrium due to alpha recoil and biogeochemical processes. A study based on measurement of uranium concentration and 234 U/ 238 U activity ratios in soil samples collected from Nalgonda district, Andhra Pradesh, India, a proposed mining site, was carried out to find the spatial distribution of uranium and the state of secular equilibrium of 234 U/ 238 U to examine the possibility of applying uranium concentration and uranium isotopic activity ratios to detect any hydrogeochemical changes in the environment during/post-operation. Soil samples were collected and analyzed for uranium concentration using the conventional UV fluorimetric method, showing a uranium concentration in the range of 0.7 ± 0.2 ppm to 7.9 ± 0.4 ppm with an average of 3.4 ppm, and 234 U/ 238 U activity ratios were estimated using the alpha spectrometry technique, showing an activity ratio in the range of 0.92 ± 0.11 to 1.02 ± 0.11. The 234 U/ 238 U activity ratio obtained indicated that these two uranium isotopes are in the state of secular radioactive equilibrium. The percent activity ratio of 238 U/total U and 234 U /total U is observed to vary from 47.94 ± 4.83 to 50.76 ± 4.87 and 45.80 ± 3.83 to 49.14 ± 3.99, respectively.

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Uranium series disequilibrium in river sediments and waters: the significance of anomalous activity ratios

Cited by 114 publications

References 30 publications

Considerations for U-series dating of sediments: Insights from the Flinders Ranges, South Australia

Considerations for U-series dating of sediments: Insights from the Flinders Ranges, South Australia

Actinide Sorption in Rainier Mesa Tunnel Waters from the Nevada Test Site

Variation in the uranium isotopic ratios²³⁴U/²³⁸U,²³⁸U/total-U and²³⁴U/total-U in Indian soil samples: Application to environmental monitoring

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Uranium series disequilibrium in river sediments and waters: the significance of anomalous activity ratios

Cited by 114 publications

References 30 publications

Considerations for U-series dating of sediments: Insights from the Flinders Ranges, South Australia

Considerations for U-series dating of sediments: Insights from the Flinders Ranges, South Australia

Actinide Sorption in Rainier Mesa Tunnel Waters from the Nevada Test Site

Variation in the uranium isotopic ratios234U/238U,238U/total-U and234U/total-U in Indian soil samples: Application to environmental monitoring

Contact Info

Product

Resources

About

Variation in the uranium isotopic ratios²³⁴U/²³⁸U,²³⁸U/total-U and²³⁴U/total-U in Indian soil samples: Application to environmental monitoring