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Krüger, N.; Külls, C.; Bruggeman, A.; Eliades, M.; Christophi, C.; Rigas, M.; Eracleous, T. |
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Groundwater recharge estimates with soil isotope profiles-is there a bias on coarse-grained hillslopes? |
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2020 |
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EGU General Assembly Conference Abstracts |
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9840 |
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THL @ christoph.kuells @ Krueger2020groundwater |
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42 |
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Tziritis, E.; Aschonitis, V.; Balacco, G.; Daras, P.; Doulgeris, C.; Fidelibus, M.D.; Gaubi, E.; Gueddari, M.; Güler, C.; Hamzaoui, F.; others |
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MEDSAL Project-Salinization of critical groundwater reserves in coastal Mediterranean areas: Identification, risk assessment and sustainable management with the use of integrated modelling and smart ICT tools |
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2020 |
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EGU General Assembly Conference Abstracts |
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2326 |
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THL @ christoph.kuells @ Tziritis2020medsal |
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43 |
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Doulgeris, C.; Tziritis, E.; Pisinaras, V.; Panagopoulos, A.; Külls, C. |
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Prediction of seawater intrusion to coastal aquifers based on non-dimensional diagrams |
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Conference Article |
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2020 |
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EGU Geophysical Abstracts |
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4073 |
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THL @ christoph.kuells @ Doulgeris2020prediction |
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41 |
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Jin, Z.; Külls, C. |
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FDM based OA-ICOS for high accuracy 13C quantification in gaseous CO2 |
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Journal Article |
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2020 |
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Earth and Environmental Science |
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EES |
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446 |
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3 |
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032061 |
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IOP Conference Series |
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THL @ christoph.kuells @ Jin2020fdm |
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16 |
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Mahindawansha, A.; Külls, C.; Kraft, P.; Breuer, L. |
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Investigating unproductive water losses from irrigated agricultural crops in the humid tropics through analyses of stable isotopes of water |
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Journal Article |
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2020 |
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Hydrology and Earth System Sciences |
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24 |
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7 |
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3627-3642 |
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Copernicus GmbH |
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yes |
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THL @ christoph.kuells @ Mahindawansha2020investigating |
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14 |
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Belz, L.; Schüller, I.; Wehrmann, A.; Köster, J.; Wilkes, H. |
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The leaf wax biomarker record of a Namibian salt pan reveals enhanced summer rainfall during the Last Glacial-Interglacial Transition |
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Journal Article |
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Year |
2020 |
Publication |
Palaeogeography, Palaeoclimatology, Palaeoecology |
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543 |
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109561 |
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-Alkanes, -Alkanols, Late Quaternary, Organic geochemistry, Palaeohydrology, Southern Africa |
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Conventional continental geoarchives are rarely available in arid southern Africa. Therefore, palaeoclimate data in this area are still patchy and late Quaternary climate development is only poorly understood. In the western Kalahari, salt pans (playas, ephemeral lakes) are common and can feature quasi-continuous sedimentation. This study presents the first climate-related biomarker record using sediments from the Omongwa Pan, a Kalahari salt pan located in eastern Namibia. Our approach to reconstruct vegetation and hydrology focuses on biogeochemical bulk parameters and plant wax-derived lipid biomarkers (n-alkanes, n-alkanols, and fatty acids) and their compound-specific carbon and hydrogen isotopic compositions. The presented record reaches back to 27 ka. During the glacial, rather low δ2H values of n-alkanes and low sediment input exclude a strong influence of winter rainfall. n-Alkane and n-alkanol distributions and δ13C values of n-hentriacontane (n-C31) indicate a shift to a vegetation with a higher proportion of C4 plants at the end of the Last Glacial Maximum until the end of Heinrich Stadial I (ca. 18–14.8 ka), which we interpret to indicate an abrupt excursion to a short wetter period likely to be caused by a temporary southward shift of the Intertropical Convergence Zone. Shifts in δ2H values of n-C31 and plant wax parameters give evidence for changes to drier conditions during early Holocene. Comparison of this dataset with representative continental records from the region points to a major influence of summer rainfall at Omongwa Pan during the regarded time span and demonstrates the potential of southern African salt pans as archives for biomarker-based climate proxies. |
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0031-0182 |
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THL @ christoph.kuells @ belz_leaf_2020 |
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104 |
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Zhou, Y.; Li, G.; Xu, L.; Liu, J.; Sun, Z.; Shi, W. |
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Uranium recovery from sandstone-type uranium deposit by acid in-situ leaching – an example from the Kujieertai |
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Journal Article |
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Year |
2020 |
Publication |
Hydrometallurgy |
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191 |
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105209 |
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Acid in-situ leaching, Sandstone-type uranium deposit, Uranium deportment in the ore, Uranium recovery, Water-rock interaction |
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The factors influencing uranium recovery in water-rock systems during acid in-situ leaching (ISL) were studied at the Kujieertai uranium deposit in Xinjiang. Using an ISL unit, a field leach trial (FLT) had been carried out to test the sequential effects of a leaching solution without oxidant (H2SO4 solution 4–8 g/L) and a leaching solution with oxidant (H2SO4 3–7 g/L, and Fe (III) 2–6 g/L). The observation of the leaching process revealed clearly defined stages of uranium release from the solid mineral to solution. Uranium mobilization from solid mineral into solution can be described in four stages. At the beginning of the acid ISL process, there was no oxidant to be added to the leaching solution and the desorption of hexavalent uranyl ions in the open pores, as well as dissolution of hexavalent uranium minerals, led to a short-term peak in the pregnant solution, which happened while pH decreased from about 5.3 to 2.62. Following the depletion of the adsorbed hexavalent uranium and a decline in uranium dissolution intensity, the addition of Fe(III) facilitated the oxidation of tetravalent uranium, which enabled intensive uranium mobilization again. During this process, the dissolution of uranium had a strong positive correlation with the reduction of Fe(III) and Eh in the leach solution. Beside hydrochemical factors, the deportment of uranium was also an important factor affecting uranium recovery. Uranium located in the open pores can be completely exposed to the solution and the mobilization intensity was significantly affected by hydrogeochemical conditions; but the uranium present in microfissures and in the ore matrix could not be fully exposed to the solution, so, their dissolution intensity was primarily controlled by corrosion and permeability of the ore. In general, the hydrogeochemical conditions and the deportment of uranium were the external and internal factors that significantly affected the dissolution and recovery of uranium in the early and middle stages of the FLT. However, in the latest stages, due to uranium depletion, enhancing the chemical potential of the leaching solution, specifically acidity and/or the amount of oxidant, had little improvement on uranium recovery. |
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0304-386x |
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THL @ christoph.kuells @ zhou_uranium_2020 |
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205 |
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Bonnetti, C.; Zhou, L.; Riegler, T.; Brugger, J.; Fairclough, M. |
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Large S isotope and trace element fractionations in pyrite of uranium roll front systems result from internally-driven biogeochemical cycle |
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Journal Article |
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2020 |
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Geochimica et Cosmochimica Acta |
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282 |
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113-132 |
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Activity cycle, Pyrite composition, Roll front uranium deposits, S isotope and trace element fractionation |
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Complex pyrite textures associated with large changes in isotopic and trace element compositions are routinely assumed to be indicative of multi-faceted processes involving multiple fluid and sulfur sources. We propose that the features of ore-stage pyrite from roll front deposits across the world, revealed in exquisite detail via high-resolution trace element mapping by LA-ICP-MS, reflect the dynamic internal evolution of the biogeochemical processes responsible for sulfate reduction, rather than externally driven changes in fluid or sulfur sources through time. Upon percolation of oxidizing fluids into the reduced host-sandstones, roll front systems become self-organized, with a systematic reset of their activity cycle after each translation stage of the redox interface down dip of the aquifer. Dominantly reducing conditions at the redox interface favor the formation of biogenic framboidal pyrite (δ34S from −30.5 to −12.5‰) by bacterial sulfate reduction and the genesis of the U mineralization. As the oxidation front advances, oxidation of reduced sulfur minerals induces an increased supply of sulfate and metals in solution to the bacterial sulfate reduction zone that has similarly advanced down the flow gradient. Hence, this stage is marked by increased rates of the bacterial sulfate reduction associated with the crystallization of variably As-Co-Ni-Mo-enriched concentric pyrite (up to 10,000′s of ppm total trace contents) with moderately negative δ34S values (from −13.7 to −7.5‰). A final stage of pyrite cement with low trace element contents and heavier δ34S signature (from −6.9 to +18.8‰) marks the end of the roll front activity cycle and the transition from an open to a predominantly closed system behavior (negligible advection of fresh sulfate). Blocky pyrite cement is formed using the remaining sulfate, which now becomes quickly heavy according to a Rayleigh isotope fractionation process. This ends the cycle by depleting the nutrient supplies for the sulfate-reducing bacteria and cementing pore spaces within the host sandstone, effectively restricting fluid infiltration. This internally-driven roll front activity cycle results in systematic, large S isotope and trace element fractionation. Ultimately, the long-time evolution of the basin and fluid sources control the metal endowment and evolution of the system; these events, however, are unlikely to be preserved by the roll front, as a direct result of its hydrodynamic nature. |
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0016-7037 |
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THL @ christoph.kuells @ bonnetti_large_2020 |
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185 |
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Sedghi, M.M.; Zhan, H. |
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Semi-analytical solutions of discharge variation of a qanat in an unconfined aquifer subjected to general areal recharge and nearby pumping well discharge |
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Journal Article |
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2020 |
Publication |
Journal of Hydrology |
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584 |
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124691 |
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Analytical solution, Laplace domain, Screen segmentation, Qanat, Areal recharge, Constant head |
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Qanat is a type of drain that extract water from aquifers by gravity. Significant amount of fresh water used in Middle East and other parts of the world are supplied by qanats. Despite their importance, discharge variation of these type of wells received almost no attention. The aim of this research is to obtain a Laplace domain solution of discharge variation of a qanat installed in an anisotropic unconfined aquifer subjected to arbitrary areal recharge and nearby pumping well(s) discharge. A new semi-analytical solution of drawdown is obtained first to implement the effects of arbitrary areal recharge and nearby pumping well(s) using the principle of superposition. Then, the discharge variation solution of the qanat is obtained from the drawdown solution. To establish a constant-head boundary condition at the qanat periphery, the qanat is discretized into several segments. The results of this study are presented in dimensionless discharge-dimensionless time curves. The effects of hydraulic as well as geometric parameters on the discharge variation of the qanat due to arbitrary areal recharge, falling of water table from its initial position and discharge of nearby wells are explored. We also investigate the influences of distance and screen depth and location of the nearby well on the discharge variation of the qanat. The results of this study can be utilized for multiple purposes: 1) to predict discharge of qanat in response to rainfall and nearby pumping well(s); 2) to estimate the aquifer parameters using hydrograph of the qanat; 3) to determine optimal location and pumping pattern of the nearby wells to minimize their influences on the discharge of the qanat; 4) to calculate water budget of aquifers drained by a qanat. The equation presented in this work can also be used to estimate discharge of a horizontal drain installed in cropland subjected to arbitrary irrigation pattern. |
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0022-1694 |
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THL @ christoph.kuells @ Sedghi2020124691 |
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261 |
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Jroundi, F.; Descostes, M.; Povedano-Priego, C.; Sánchez-Castro, I.; Suvannagan, V.; Grizard, P.; Merroun, M.L. |
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Profiling native aquifer bacteria in a uranium roll-front deposit and their role in biogeochemical cycle dynamics: Insights regarding in situ recovery mining |
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Journal Article |
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Year |
2020 |
Publication |
Science of The Total Environment |
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721 |
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137758 |
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Bacterial diversity, Bioremediation, In-situ recovery, Natural attenuation, Network analysis, Uranium |
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A uranium-mineralized sandy aquifer, planned for mining by means of uranium in situ recovery (U ISR), harbors a reservoir of bacterial life that may influence the biogeochemical cycles surrounding uranium roll-front deposits. Since microorganisms play an important role at all stages of U ISR, a better knowledge of the resident bacteria before any ISR actuations is essential to face environmental quality assessment. The focus here was on the characterization of bacteria residing in an aquifer surrounding a uranium roll-front deposit that forms part of an ISR facility project at Zoovch Ovoo (Mongolia). Water samples were collected following the natural redox zonation inherited in the native aquifer, including the mineralized orebody, as well as compartments located both upstream (oxidized waters) and downstream (reduced waters) of this area. An imposed chemical zonation for all sensitive redox elements through the roll-front system was observed. In addition, high-throughput sequencing data showed that the bacterial community structure was shaped by the redox gradient and oxygen availability. Several interesting bacteria were identified, including sulphate-reducing (e.g. Desulfovibrio, Nitrospira), iron-reducing (e.g. Gallionella, Sideroxydans), iron-oxidizing (e.g. Rhodobacter, Albidiferax, Ferribacterium), and nitrate-reducing bacteria (e.g. Pseudomonas, Aquabacterium), which may also be involved in metal reduction (e.g. Desulfovibrio, Ferribacterium, Pseudomonas, Albidiferax, Caulobacter, Zooglea). Canonical correspondence analysis (CCA) and co-occurrence patterns confirmed strong correlations among the bacterial genera, suggesting either shared/preferred environmental conditions or the performance of similar/complementary functions. As a whole, the bacterial community residing in each aquifer compartment would appear to define an ecologically functional ecosystem, containing suitable microorganisms (e.g. acidophilic bacteria) prone to promote the remediation of the acidified aquifer by natural attenuation. Assessing the composition and structure of the aquifer’s native bacteria is a prerequisite for understanding natural attenuation and predicting the role of bacterial input in improving ISR efficiency. |
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0048-9697 |
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THL @ christoph.kuells @ jroundi_profiling_2020 |
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177 |
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