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Author |
Külls, C.H.; Eichinger, F.; Fader, H.J.; Leistert, H.; Lorenz, G.; Szakacs, E. |
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Title |
New Environmental Analytical Techniques to Monitor Carbon Sequestration |
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Conference Article |
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2011 |
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1st EAGE Sustainable Earth Sciences (SES) Conference and Exhibition |
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268 |
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European Association of Geoscientists & Engineers |
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THL @ christoph.kuells @ Kuells2011new |
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47 |
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Author |
Vogel, J.C.; Talma, A.S.; Heaton, T.H.E.; Kronfeld, J. |
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Title |
Evaluating the rate of migration of an uranium deposition front within the Uitenhage Aquifer |
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Journal Article |
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Year |
1999 |
Publication |
Journal of Geochemical Exploration |
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66 |
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1 |
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269-276 |
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Keywords |
redox changes in aquifer, sandstone-type uranium deposit, South Africa, uranium series |
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Abstract |
The solubility of uranium in groundwater is very sensitive to changes in redox conditions. Many secondary (sandstone-type) uranium deposits have been formed when soluble U has precipitated after encountering reducing conditions in the subsurface. In the groundwater of the Uitenhage Aquifer (Cape Province, South Africa), 238U-series isotopes were used to assist in studying the history of the reducing barrier. Uranium isotopes were used to determine the present position of the barrier. Radium and radon were used to evaluate the path of migration that the front of the oxygen depletion zone has taken over the past 105 years. During this time the reducing barrier has moved, leaving in its wake a trail of U in various stages of secular equilibrium with its daughter 230Th. The 226Ra daughter of 230Th is not very mobile. Its growth upon the aquifer wall is reflected in the Rn content of the water. This in turn, due to the relatively great age of the water, indicates the extent of the 230Th ingrowth (from precipitated U) that took place before the barrier migrated. |
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0375-6742 |
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THL @ christoph.kuells @ vogel_evaluating_1999 |
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126 |
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Post, V.E.A.; Vassolo, S.I.; Tiberghien, C.; Baranyikwa, D.; Miburo, D. |
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Title |
Weathering and evaporation controls on dissolved uranium concentrations in groundwater – A case study from northern Burundi |
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Journal Article |
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Year |
2017 |
Publication |
Science of The Total Environment |
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607-608 |
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281-293 |
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Keywords |
Geochemical modelling, Hydrochemistry, Lake Tshohoha South, Public health, Radionuclides, Water supply |
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The potential use of groundwater for potable water supply can be severely compromised by natural contaminants such as uranium. The environmental mobility of uranium depends on a suite of factors including aquifer lithology, redox conditions, complexing agents, and hydrological processes. Uranium concentrations of up to 734μg/L are found in groundwater in northern Burundi, and the objective of the present study was to identify the causes for these elevated concentrations. Based on a comprehensive data set of groundwater chemistry, geology, and hydrological measurements, it was found that the highest dissolved uranium concentrations in groundwater occur near the shores of Lake Tshohoha South and other smaller lakes nearby. A model is proposed in which weathering and evapotranspiration during groundwater recharge, flow and discharge exert the dominant controls on the groundwater chemical composition. Results of PHREEQC simulations quantitatively confirm this conceptual model and show that uranium mobilization followed by evapo-concentration is the most likely explanation for the high dissolved uranium concentrations observed. The uranium source is the granitic sand, which was found to have a mean elemental uranium content of 14ppm, but the exact mobilization process could not be established. Uranium concentrations may further be controlled by adsorption, especially where calcium-uranyl‑carbonate complexes are present. Water and uranium mass balance calculations for Lake Tshohoha South are consistent with the inferred fluxes and show that high‑uranium groundwater represents only a minor fraction of the overall water input to the lake. These findings highlight that the evaporation effects that cause radionuclide concentrations to rise to harmful levels in groundwater discharge areas are not only confined to arid regions, and that this should be considered when selecting suitable locations for water supply wells. |
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0048-9697 |
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THL @ christoph.kuells @ post_weathering_2017 |
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132 |
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Author |
Gómez, P.; Garralón, A.; Buil, B.; Turrero, M.J.; Sánchez, L.; Cruz, B. de la |
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Title |
Modeling of geochemical processes related to uranium mobilization in the groundwater of a uranium mine |
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Journal Article |
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Year |
2006 |
Publication |
Science of The Total Environment |
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366 |
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1 |
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295-309 |
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Geochemical modeling, Granite, Groundwater, Uranium mine, Uranium retention |
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This paper describes the processes leading to uranium distribution in the groundwater of five boreholes near a restored uranium mine (dug in granite), and the environmental impact of restoration work in the discharge area. The groundwater uranium content varied from \textless1 μg/L in reduced water far from the area of influence of the uranium ore-containing dyke, to 104 μg/L in a borehole hydraulically connected to the mine. These values, however, fail to reflect a chemical equilibrium between the water and the pure mineral phases. A model for the mobilization of uranium in this groundwater is therefore proposed. This involves the percolation of oxidized waters through the fractured granite, leading to the oxidation of pyrite and arsenopyrite and the precipitation of iron oxyhydroxides. This in turn leads to the dissolution of the primary pitchblende and, subsequently, the release of U(VI) species to the groundwater. These U(VI) species are retained by iron hydroxides. Secondary uranium species are eventually formed as reducing conditions are re-established due to water–rock interactions. |
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0048-9697 |
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THL @ christoph.kuells @ gomez_modeling_2006 |
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162 |
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Author |
Klaus, J.; Külls, C.; Dahan, O. |
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Title |
Evaluating the recharge mechanism of the Lower Kuiseb Dune area using mixing cell modeling and residence time data |
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Journal Article |
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Year |
2008 |
Publication |
Journal of Hydrology |
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358 |
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3-4 |
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304-316 |
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Elsevier |
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THL @ christoph.kuells @ Klaus2008evaluating |
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28 |
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Frumkin, A.; Gvirtzman, H. |
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Cross-formational rising groundwater at an artesian karstic basin: the Ayalon Saline Anomaly, Israel |
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Journal Article |
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Year |
2006 |
Publication |
Journal of Hydrology |
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318 |
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1 |
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316-333 |
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Confined karst, Groundwater, HS, Maze caves, Rising water, Yarkon–Taninim aquifer |
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It is proposed that a geothermal artesian karstic system at the central part of the Yarkon–Taninim aquifer creates the ‘Ayalon Saline Anomaly’ (ASA), whose mechanism has been under debate for several decades. A 4-year-long detailed groundwater monitoring was carried out at 68 new shallow boreholes in the Ayalon region, accompanied by a comprehensive survey of karstic voids. Results indicate the rising of warm-brackish groundwater through highly permeable swarms of karstic shafts, serving as an outflow of the artesian geothermal system. The ASA area contains ‘hot spots’, where groundwater contrasts with ‘normal’ water hundreds of meters away. The ASA temperature reaches 30°C (∼5°C warmer than its surroundings), chloride concentration reaches 528mg/l (50–100mg/l in the surrounding), H2S concentration reaches 5.6mg/l (zero all around) and pH value is 7.0 (compared with 7.8 around). Subsequently, the hydrothermal water flows laterally of at the watertable horizon through horizontal conduits, mixing with ‘normal’ fresh water which had circulated at shallow depth. Following rainy seasons, maximal watertable rise is observed in the ASA compared to its surroundings. Regional hydrogeology considerations suggest that the replenishment area for the ASA water is at the Samaria Mountains, east of the ASA. The water circulates to a great depth while flowing westward, and a cross-formational upward flow is then favored close the upper sub-aquifer’s confinement border. |
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0022-1694 |
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THL @ christoph.kuells @ frumkin_cross-formational_2006 |
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117 |
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Orloff, K.G.; Mistry, K.; Charp, P.; Metcalf, S.; Marino, R.; Shelly, T.; Melaro, E.; Donohoe, A.M.; Jones, R.L. |
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Title |
Human exposure to uranium in groundwater |
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Journal Article |
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Year |
2004 |
Publication |
Environmental Research |
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94 |
Issue |
3 |
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319-326 |
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Groundwater, Human exposure, Uranium, Urine |
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High concentrations of uranium (mean=620μg/L) were detected in water samples collected from private wells in a residential community. Based on isotopic analyses, the source of the uranium contamination appeared to be from naturally occurring geological deposits. In homes where well water concentrations of uranium exceeded the drinking water standard, the residents were advised to use an alternate water source for potable purposes. Several months after the residents had stopped drinking the water, urine samples were collected and tested for uranium. Elevated concentrations of uranium (mean=0.40μg/g creatinine) were detected in urine samples, and 85 percent of the urine uranium concentrations exceeded the 95th percentile concentration of a national reference population. Urine uranium concentrations were positively correlated with water uranium concentrations, but not with the participants’ ages or how long they had been drinking the water. Six months later, a second urine sample was collected and tested for uranium. Urine uranium concentrations decreased in most (63 percent) of the people. In those people with the highest initial urine uranium concentrations, the urine levels decreased an average of 78 percent. However, urine uranium concentrations remained elevated (mean=0.27μg/g), and 87 percent of the urine uranium concentrations exceeded the 95th percentile concentration of the reference population. The results of this investigation demonstrated that after long-term ingestion of uranium in drinking water, elevated concentrations of uranium in urine could be detected up to 10 months after exposure had stopped. |
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0013-9351 |
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THL @ christoph.kuells @ orloff_human_2004 |
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136 |
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Priestley, S.C.; Payne, T.E.; Harrison, J.J.; Post, V.E.A.; Shand, P.; Love, A.J.; Wohling, D.L. |
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Title |
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 |
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Journal Article |
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2018 |
Publication |
Applied Geochemistry |
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98 |
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331-344 |
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Activity ratios, Central Australia, Great Artesian Basin, Hydrogeology, Sequential extraction, Uranium isotopes |
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Abstract |
The distribution of uranium isotopes (238U and 234U) in groundwaters of the south-western margin of the Great Artesian Basin (GAB), Australia, and underlying Arckaringa Basin were examined using groundwater samples and a sequential extraction of aquifer sediments. Rock weathering, the geochemical environment and α-recoil of daughter products control the 238U and 234U isotope distributions giving rise to large spatial variations. Generally, the shallowest aquifer (J aquifer) contains groundwater with higher 238U activity concentrations and 234U/238U activity ratios close to secular equilibrium. However, the source input of uranium is spatially variable as intermittent recharge from ephemeral rivers passes through rocks that have already undergone extensive weathering and contain low 238U activity concentrations. Other locations in the J aquifer that receive little or no recharge contain higher 238U activity concentrations because uranium from localised uranium-rich rocks have been leached into solution and the geochemical environment allows the uranium to be kept in solution. The geochemical conditions of the deeper aquifers generally result in lower 238U activity concentrations in the groundwater accompanied by higher 234U/238U activity ratios. The sequential extraction of aquifer sediments showed that α-recoil of 234U from the solid mineral phases into the groundwater, rather than dissolution of, or exchange with the groundwater accessible minerals in the aquifer, caused enrichment of groundwater 234U/238U activity ratios in the Boorthanna Formation. Decay of 238U in uranium-rich coatings on J aquifer sediments caused resistant phase 234U/238U activity ratio enrichment. The groundwater 234U/238U activity ratio is dependent on groundwater residence time or flow rate, depending on the flow path trajectory. Thus, uranium isotope variations confirmed earlier groundwater flow interpretations based on other tracers; however, spatial heterogeneity, and the lack of clear regional correlations, made it difficult to identify recharge and inter-aquifer leakage. |
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0883-2927 |
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THL @ christoph.kuells @ priestley_use_2018 |
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115 |
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Author |
Udluft, P.; Külls, C. |
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Mapping the availability and dynamics of groundwater recharge. Part 1: modelling techniques |
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Conference Article |
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2000 |
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Proceedings of the Third Congress on Regional Geological Cartography and Information Systems |
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337-340 |
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THL @ christoph.kuells @ Udluft2000mapping |
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64 |
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Müller, M.; Alaoui, A.; Külls, C.; Leistert, H.; Meusburger, K.; Stumpp, C.; Weiler, M.; Alewell, C. |
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Tracking water pathways in steep hillslopes by δ18O depth profiles of soil water |
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Journal Article |
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2014 |
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Journal of hydrology |
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519 |
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340-352 |
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THL @ christoph.kuells @ Mueller2014tracking |
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20 |
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