Evolution of the Uranium Isotopic Compositions of the Groundwater and Rock in the Sandy-Clayey Aquifer

Малов, А. И.

doi:10.20944/preprints201710.0024.v1

Cited by 5 publications

(3 citation statements)

References 21 publications

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“…The results obtained partially confirm previously expressed ideas about the evolution of U isotopic compositions of the Vendian rock near the study area [20]. Our results are consistent with the experimental results of Lowson et al [16], Payne et al [17], and Dabous et al [18], which note the similarity of the 234 U: 238 U activity ratios in groundwater and in the most easily leached fractions of water-bearing rocks.…”

Section: Evolution Of Uranium Isotopic Compositionssupporting

confidence: 92%

“…At the same time, the lower average value of 234 U: 238 U activity ratio 0.92 [20] was established in the samples of green siltstones taken in the paleovalley, which was screened by the layer of sea clays.…”

Section: Evolution Of Uranium Isotopic Compositionsmentioning

confidence: 93%

“…These fractions were defined as adsorbed elements, carbonate minerals and amorphous iron minerals [19]. This may indicate the opposite process: the transition of nonequilibrium nuclides from water to rock with an increase in the ratio of U isotope activities in the rock [20]. Under such conditions, it is difficult to estimate the rate of chemical weathering by using the currently developed methods [21][22].…”

Section: Introductionmentioning

confidence: 99%

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<strong></strong>Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer Using Methods for the Extraction of Uranium with Different Strength Reagents in Combination with Groundwater Data

Ai¹,

Sb²

2019

Preprint

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A partial extraction procedure was used to study the distribution of uranium in the mineral phases of rocks of an aquifer of sandy-clay deposits of the Vendian in the northwest of Russia. This work is a part of a research project to develop a method for combined radiocarbon and uranium-isotope dating of groundwater. Representative aliquots of each core sample were subjected to five "partial" extractions by treatment with: distilled water, low mineralized fresh natural groundwater, minopolycarboxylic acid chelating agent (0.05M EDTA), 0.5M HCl, 15M HNO3, and a total digestion, with U isotopes reported in this study for each procedure. The following mineral phases of core samples: adsorbed material, carbonate minerals, amorphous iron oxides, aluminosilicates partial digestion and a crystalline iron oxides, aluminosilicates total digestion and a clay/quartz resistate were characterized. Red-colored siltstones depleted in uranium in relatively readily soluble mineral phases. The concentration of adsorbed uranium was established in the amount of 15.8±2.1 - 30.5±3.9 μg/kg. Carbonate minerals contain even less of this element. In iron hydroxides and the most readily soluble aluminosilicates, its concentrations are in the range 168±24 - 212±28 μg/kg. The most insoluble fraction contains 1.65±0.21 - 4.32±0.45 mg/kg of uranium. In green-colored siltstones, the concentration of adsorbed uranium is much higher: 106±14 - 364±43 μg/kg. Carbonate minerals and amorphous iron oxides contain 1.91±0.21 - 2.34±0.26 mg/kg of uranium. In aluminosilicates and a clay/quartz resistate, uranium concentrations are 5.6±0.5 - 16.8±1.4 mg/kg. Elevated values of 234U:238U activity ratio prevail in the adsorbed material and iron hydroxides. In aluminosilicates and clay/quartz resistate, the values decrease. This indicates the replacement of primary sedimentogenic uranium by secondary hydrogenic uranium adsorbed on the surface of minerals and coprecipitated with iron hydroxides. The results obtained made it possible to carry out preliminary quantitative estimates of the retardation factor and recoil loss factor of uranium in the groundwater of siltstones of the studied Vendian aquifer.

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Section: Evolution Of Uranium Isotopic Compositionssupporting

confidence: 92%

Section: Evolution Of Uranium Isotopic Compositionsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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<strong></strong>Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer Using Methods for the Extraction of Uranium with Different Strength Reagents in Combination with Groundwater Data

Ai¹,

Sb²

2019

Preprint

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Distribution of Uranium Isotopes in Sandy Deposits by Sequential Extraction

2021

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The sequential extraction procedure is used to reconstruct the processes of redistribution of uranium isotopes in the mineral phases of the aquifer of the Vendian sandy-argillaceous deposits developed in the coastal territory of the European North of Russia. This aquifer has large resources of drinking and mineral groundwater which, however, are used in extremely limited quantities. This is due to the very complex nature of the hydrochemical conditions, and uranium-isotopic methods are used to clarify these conditions. The following mineral phases of core samples were characterized: adsorbed trace materials and carbonate minerals; ferrihydrate, amorphous minerals of Fe, Al and Si, and secondary U minerals; crystalline iron minerals; clay and some refractory minerals; and all remaining resistant minerals. The most resistant minerals, whose fraction ranges from 70.58 to 96.4%, have a minimum average uranium concentration of 0.47 ppm. This uranium is practically conserved in the rock, as a result of which the average ratio of its 234U:238U isotopes is close to equilibrium. In the remaining fractions, uranium is redistributed by groundwater along their flow lines from recharge areas in watersheds to areas of discharge into river valleys. Its maximum concentration (12.89 ppm) measurement is carried out by coprecipitation with iron hydroxides, then the uranium is adsorbed and precipitated with carbonates (9.14 ppm). The average 234U:238U is maximum in adsorbed trace materials and carbonate minerals (2.39 ± 0.36) and is close to that in fresh groundwater (2.8 ± 0.42). It is also increased in the amorphous minerals of Fe (1.53 ± 0.23). In general, there is a dependence of the 234U:238U activity ratio in rock on the degree of participation of groundwater in the deposition of hydrogenic uranium isotopes into the cracks and pores of these rocks. The results obtained contribute to the refinement of such a parameter as the retardation factor, which is necessary for understanding the processes of migration and concentration of uranium in sedimentary basins.

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Isotopes in Hydrology and Hydrogeology

Barbieri

2019

Water

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The structure, status, and processes of the groundwater system, which can only be acquired through scientific research efforts, are critical aspects of water resource management. Isotope hydrology and hydrogeology is a genuinely interdisciplinary science. It developed from the application of methods evolved in physics (analytical techniques) to problems of Earth and the environmental sciences since around the 1950s. In this regard, starting from hydrogeochemical data, stable and radioactive isotope data provide essential tools in support of water resource management. The inventory of stable isotopes, which has significant implications for water resources management, has grown in recent years. Methodologies based on the use of isotopes in a full spectrum of hydrological problems encountered in water resource assessment, development, and management activities are already scientifically established and are an integral part of many water resource investigations and environmental studies. The driving force behind this Special Issue was the need to point the hydrological and water resource management societies in the direction of up-to-date research and best practices.

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Evolution of the Uranium Isotopic Compositions of the Groundwater and Rock in the Sandy-Clayey Aquifer

Abstract: Uranium isotopes actively investigated as mechanistic or time scale tracers of natural 9 processes. This paper describes the occurrence and redistribution of U in the Vendian aquifer of 10 the paleo valley at NW Russia. Forty-four rock samples were collected from boreholes, and

Cited by 5 publications

References 21 publications

<strong></strong>Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer Using Methods for the Extraction of Uranium with Different Strength Reagents in Combination with Groundwater Data

<strong></strong>Study of the Mobilization of Uranium Isotopes in a Sandstone Aquifer Using Methods for the Extraction of Uranium with Different Strength Reagents in Combination with Groundwater Data

Distribution of Uranium Isotopes in Sandy Deposits by Sequential Extraction

Isotopes in Hydrology and Hydrogeology

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