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Author |
Heaton, T.H.E.; Talma, A.S.; Vogel, J.C. |
Title |
Origin and history of nitrate in confined groundwater in the western Kalahari |
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Journal Article |
Year |
1983 |
Publication |
Journal of Hydrology |
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Volume |
62 |
Issue |
1 |
Pages |
243-262 |
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Abstract |
Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr. |
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0022-1694 |
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THL @ christoph.kuells @ Heaton1983243 |
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282 |
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Author |
Rosen, M.R.; Burow, K.R.; Fram, M.S. |
Title |
Anthropogenic and geologic causes of anomalously high uranium concentrations in groundwater used for drinking water supply in the southeastern San Joaquin Valley, CA |
Type |
Journal Article |
Year |
2019 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
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Volume |
577 |
Issue |
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Pages |
124009 |
Keywords |
California, Central Valley, Geochemistry, Groundwater San Joaquin Valley, Uranium |
Abstract |
Concentrations of uranium (U) \textgreater30 µg/L in groundwater are relatively uncommon in drinking water in the United States but can be of concern in those areas where complex interactions of aquifer materials and anthropogenic alterations of the natural flow regime mobilize U. High concentrations (\textgreater30 µg/L) of U in the southeastern San Joaquin Valley, California, USA, have been detected in 24 percent of 257 domestic, irrigation, and public-supply wells sampled across an approximately 110,000 km2 area. In this study we evaluated mechanisms for mobilization of U in the San Joaquin Valley proposed in previous studies, confirming mobilization by HCO3 and refuting mobilization by NO3 and we refined our understanding of the geologic sources of U to the scale of individual alluvial fans. The location of high concentrations depends on the interactions of geological U sources from fluvial fans that originate in the Sierra Nevada to the east and seepage of irrigation water that contains high concentrations of HCO3 that leaches U from the sediments. In addition, interactions with PO4 from fertilized irrigated fields may sequester U in the aquifer. Principal component analysis of the data demonstrates that HCO3 and ions associated with high total dissolved solids in the aquifer and the percentage of agriculture near the well sampled are associated with high U concentrations. Nitrate concentrations do not appear to control release of U to the aquifer. Age dating of the groundwater and generally increasing U concentrations of the past 25 years in resampled wells where irrigation is prevalent suggests that high U concentrations are associated with younger water, indicating that irrigation of fields over the past 100 years has significantly contributed to increasing concentrations and mobilizing U. In some places, the groundwater is supersaturated with uranyl-containing minerals, as would be expected in roll front deposits. In general, the interaction of natural geological sources high in U, the anthropogenically driven addition of HCO3 and possibly phosphate fertilizer, control the location and concentration of U in each individual fluvial fan, but the addition of nitrate in fertilizer does not appear control the location of high U. These geochemical interactions are complex but can be used to determine controls on anomalously high U in alluvial aquifers. |
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THL @ christoph.kuells @ rosen_anthropogenic_2019 |
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158 |
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Author |
Vogel, J.C.; Talma, A.S.; Heaton, T.H.E. |
Title |
Gaseous nitrogen as evidence for denitrification in groundwater |
Type |
Journal Article |
Year |
1981 |
Publication |
Journal of Hydrology |
Abbreviated Journal |
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Volume |
50 |
Issue |
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Pages |
191-200 |
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By investigating the nitrate, oxygen, nitrogen and argon concentrations and 15N14N ratios in artesian groundwater with radiocarbon ages ranging up to 27,000 yr. a process of very slow denitrification in a confined aquifer is demonstrated. The calculated nitrogenisotope fractionation factor associated with this reaction is comparable to that reported for bacterial cultures in vitro and in vivo. |
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0022-1694 |
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THL @ christoph.kuells @ Vogel1981191 |
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280 |
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Author |
Wang, B.; Luo, Y.; Liu, J.-hui; Li, X.; Zheng, Z.-hong; Chen, Q.-qian; Li, L.-yao; Wu, H.; Fan, Q.-ren |
Title |
Ion migration in in-situ leaching (ISL) of uranium: Field trial and reactive transport modelling |
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Journal Article |
Year |
2022 |
Publication |
Journal of Hydrology |
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Volume |
615 |
Issue |
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Pages |
128634 |
Keywords |
Acid in situ leaching, Banyan-Uul uranium deposit, Influence area, Reactive transport, Sensitivity analysis |
Abstract |
Acid in-situ leaching (ISL) can be used as a mining technique for in situ uranium recover from underground. Acids and oxidants as lixiviants were continuously injected into a sandstone-type uranium deposit in Bayan-Uul (China). It was conducted to facilitate the dissolution of uranium minerals to generate uranyl ions, which could then be extracted for the recovery of uranium resources by the pumping cycle. A reactive transport model based on PHAST was developed to investigate the dynamic reactive migration process of uranium. The simulated results well reproduce the fluid dynamic evolution in the injecting and pumping units, as well as the dynamic release of uranium. The simulated leaching area indicates that the uranium ore leaching area was much larger than the acidification area. In addition, the pollution plume of uranium and acid water was larger than that of the leaching area, which can be used as a reference for uranium mining schemes. Furthermore, the parameter sensitivity analysis indicates the volume fraction of uranium ore and the reaction rate were the main factors affecting uranium leaching efficiency. Without considering the blockage of pores by precipitation, the Fe2+ in the reinjection fluid had a significant negative influence on uranium leaching. |
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THL @ christoph.kuells @ wang_ion_2022 |
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195 |
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Author |
Morin, E.; Grodek, T.; Dahan, O.; Benito, G.; Külls, C.; Jacoby, Y.; Van Langenhove, G.; Seely, M.; Enzel, Y. |
Title |
Flood routing and alluvial aquifer recharge along the ephemeral arid Kuiseb River, Namibia |
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Journal Article |
Year |
2009 |
Publication |
Journal of Hydrology |
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Volume |
368 |
Issue |
1-4 |
Pages |
262-275 |
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Elsevier |
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THL @ christoph.kuells @ Morin2009flood |
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26 |
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