| Records |
| Author |
Ammar, F.H.; Deschamps, P.; Chkir, N.; Zouari, K.; Agoune, A.; Hamelin, B. |
| Title |
Uranium isotopes as tracers of groundwater evolution in the Complexe Terminal aquifer of southern Tunisia |
Type |
Journal Article |
| Year |
2020 |
Publication |
Quaternary International |
Abbreviated Journal |
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| Volume |
547 |
Issue |
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Pages |
33-49 |
Keywords  |
CT southern Tunisia, Holocene, Mixing, Radicarbon, Uranium isotopes, Water-rock interaction |
| Abstract |
The Complexe Terminal (CT) multi-layer aquifer is formed by Neogene/Paleogene sand deposits, Upper Senonian (Campanian-Maastrichtian limestones) and Turonian carbonates. The chemical composition and isotopes of carbon and uranium were investigated in groundwater sampled from the main hydrogeological units of the (CT) aquifer in southern Tunisia. We paid special attention to the variability of uranium contents and isotopes ratio (234U/238U) to provide a better understanding of the evolution of the groundwater system. Uranium concentrations range from 1.5 to 19.5 ppb, typical of oxic or mildly reducing conditions in groundwaters. The lowest concentrations are found southeast of the study area, where active recharge is supposed to take place. When looking at the isotope composition, it appears that all the samples, including those from carbonate levels, are in radioactive disequilibrium with significant 234U excess. A clear-cut distinction is observed between Turonian and Senonian carbonate aquifers on the one hand, with 234U/238U activity ratios between 1.1 and 1.8, and the sandy aquifer on the other hand, showing higher ratios from 1.8 to 3.2. The distribution of uranium in this complex aquifer system seems to be in agreement with the lithological variability and are ultimately a function of a number of physical and chemical factors including the uranium content of the hosting geological formation, water-rock interaction and mixing between waters having different isotopic signatures. Significant relationships also appear when comparing the uranium distribution with the major ions composition. It is noticeable that uranium is better correlated with sulfate, calcium and magnesium than with other major ions as chloride or bicarbonate. The 14C activities and δ13C values of DIC cover a wide range of values, from 1.1 pmc to 30.2 pmc and from −3.6‰ to −10.7‰, respectively. 14C model ages estimated by the Fontes and Garnier model are all younger than 22 Ka and indicate that the recharge of CT groundwater occurred mainly during the end of the last Glacial and throughout the Holocene. |
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| ISSN |
1040-6182 |
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THL @ christoph.kuells @ ammar_uranium_2020 |
Serial |
119 |
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| Author |
Robin, V.; Beaufort, D.; Tertre, E.; Reinholdt, M.; Fromaget, M.; Forestier, S.; Boissezon, H. de; Descostes, M. |
| Title |
Fate of dioctahedral smectites in uranium roll front deposits exploited by acidic In Situ Recovery (ISR) solutions |
Type |
Journal Article |
| Year |
2020 |
Publication |
Applied Clay Science |
Abbreviated Journal |
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| Volume |
187 |
Issue |
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Pages |
105484 |
| Keywords |
Dissolution, In situ recovery, Ion exchange, Post mining, Remediation, Smectite |
| Abstract |
In Situ Recovery (ISR) is the most important process of uranium production in the world (50%). It consists of an injection of a leaching solution into a permeable mineralized aquifer (sandstone), pumping of the solution after dissolution of the ore minerals and recovery of the uranium from the pregnant solution in a surface plant. In this context, the fate of swelling clay minerals such as smectites is of main importance due to their role in the mobility of cationic elements by diverse geochemical processes such as ion-exchange reactions or dissolution. The present study details analysis of dioctahedral smectites before and after in-situ leaching by acidic (H2SO4) ISR solutions. Samples were collected from two sedimentary basins hosting some of the main uranium roll front deposits exploited by acidic ISR (Tortkuduk deposit, Shu-Saryssu basin, Kazakhstan, and Dulaan Uul and Zoovch Ovoo deposits, Sainshand basin, Mongolia). Scanning Electron Microscope and X-Ray Diffraction analysis revealed that dioctahedral smectite is a ubiquitous mineral in all analyzed samples, before and after acidification, and revealed a difference of crystal chemistry of the smectites between deposits of Kazakhstan (beidellite type) and Mongolia (montmorillonite type). Chemical analysis and semi-quantification of the smectites before and after acidification also revealed a difference in chemical reactivity, with a higher dissolution of montmorillonite layers compared to beidellite ones, and the importance of ion-exchange reactions. These findings are consistent with literature data obtained on model systems. The persistence of dioctahedral smectites after several years of acidification is crucial for the understanding of geochemical processes during uranium production or remediation of the aquifers. Finally, based on the analysis of samples from U-deposits hosted in both sedimentary basins, a schematic model of the impact of acid solutions on dioctahedral smectite was proposed. |
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0169-1317 |
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no |
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THL @ christoph.kuells @ robin_fate_2020 |
Serial |
179 |
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Sahoo, S.K.; Jha, V.N.; Patra, A.C.; Jha, S.K.; Kulkarni, M.S. |
| Title |
Scientific background and methodology adopted on derivation of regulatory limit for uranium in drinking water – A global perspective |
Type |
Journal Article |
| Year |
2020 |
Publication |
Environmental Advances |
Abbreviated Journal |
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| Volume |
2 |
Issue |
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Pages |
100020 |
| Keywords |
Drinking water, Global policy, Regulatory limits, Toxicity, Uranium |
| Abstract |
Guideline values are prescribed for drinking water to ensure long term protection of the public against anticipated potential adverse effects. There is a great public and regulatory agencies interest in the guideline values of uranium due to its complex behavior in natural aquatic system and divergent guideline values across the countries. Wide variability in guideline values of uranium in drinking water may be attributed to toxicity reference point, variation in threshold values, uncertainty within intraspecies and interspecies, resource availability, socio-economic condition, variation in ingestion rate, etc. Although guideline values vary to a great extent, reasonable scientific basis and technical judgments are essential before it could be implemented. Globally guideline values are derived considering its radiological or chemical toxicity. Minimal or no adverse effect criterions are normally chosen as the basis for deriving the guideline values of uranium. In India, the drinking water limit of 60 µg/L has been estimated on the premise of its radiological concern. A guideline concentration of 2 µg/L is recommended in Japan while 1700 µg/L in Russia. The relative merit of different experimental assumption, scientific approach and its methodology adopted for derivation of guideline value of uranium in drinking water in India and other countries is discussed in the paper. |
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Edition |
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| ISSN |
2666-7657 |
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no |
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THL @ christoph.kuells @ sahoo_scientific_2020 |
Serial |
127 |
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| Author |
Su, X.; Liu, Z.; Yao, Y.; Du, Z. |
| Title |
Petrology, mineralogy, and ore leaching of sandstone-hosted uranium deposits in the Ordos Basin, North China |
Type |
Journal Article |
| Year |
2020 |
Publication |
Ore Geology Reviews |
Abbreviated Journal |
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| Volume |
127 |
Issue |
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Pages |
103768 |
| Keywords |
Geochemical composition, leach mining, Mineralogy, Ordos Basin, Sandstone-hosted uranium deposit |
| Abstract |
The Nalinggou–Daying uranium metallogenic belt is situated at the northern Ordos Basin, China. Petrographical, mineralogical and geochemical techniques were used to study the ore-bearing sandstones and host rocks in the Nalinggou–Daying uranium metallogenic belt. The present study shows that uranium minerals, i.e., coffinite, pitchblende, and brannerite, are mostly disseminated around pyrite and detrital particles. The ore-bearing sandstones are enriched in organic matter, with which this reductive environment influenced uranium leaching. The carbonate concentration of the uranium ores is markedly higher than that of the host rocks, and intense carbonatization occurs in the ore-bearing sandstones. In this case, the usage of the classical in-situ leach uranium mining technique by injecting H2SO4 + H2O2 solution produces calcium sulfate precipitate, which can lead to blocking of the ore-bearing strata. For this reason, laboratory and field uranium mining tests were conducted using CO2 + O2 in-situ leaching technology and were demonstrated to be successful, illustrating that this approach is technically feasible. Inhibiting ore bed blockage and increasing the amount of injected O2 are important for uranium leaching in this setting. |
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0169-1368 |
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no |
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THL @ christoph.kuells @ su_petrology_2020 |
Serial |
120 |
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| Author |
Christofi, C.; Bruggeman, A.; Külls, C.; Constantinou, C. |
| Title |
Hydrochemical evolution of groundwater in gabbro of the Troodos Fractured Aquifer. A comprehensive approach |
Type |
Journal Article |
| Year |
2020 |
Publication |
Applied Geochemistry |
Abbreviated Journal |
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| Volume |
114 |
Issue |
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Pages |
104524 |
| Keywords |
geochemistry |
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Pergamon |
Place of Publication |
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English |
Summary Language |
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no |
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THL @ christoph.kuells @ Christofi2020hydrochemical |
Serial |
13 |
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