| Records |
| Author |
Brook, G.A.; Railsback, L.B.; Marais, E. |
| Title |
Reassessment of carbonate ages by dating both carbonate and organic material from an Etosha Pan (Namibia) stromatolite: Evidence of humid phases during the last 20ka |
Type |
Journal Article |
| Year |
2011 |
Publication  |
Quaternary International |
Abbreviated Journal |
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| Volume |
229 |
Issue |
1 |
Pages |
24-37 |
| Keywords |
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| Abstract |
Previous research on lacustrine stromatolites from Etosha Pan in Namibia obtained ages on carbonate close to or beyond the limits of radiocarbon dating. These ages suggested that the basin was likely not subject to extensive flooding during the last ca. 40ka. This study shows that AMS radiocarbon ages for the carbonate of a stromatolite from Poacher’s Point are 15–21ka older than ages for organic material in the stromatolite structure. Calibrated ages range from 30 to 40ka for carbonate and 3–19ka for the organic residue. The new ages, together with petrographic and isotopic data for the stromatolite, have provided important new information on past flooding of Etosha Pan including evidence of prolonged lacustrine conditions during the Holocene Climatic Optimum. |
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1040-6182 |
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no |
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THL @ christoph.kuells @ brook_reassessment_2011 |
Serial |
110 |
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| 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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1040-6182 |
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no |
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THL @ christoph.kuells @ ammar_uranium_2020 |
Serial |
119 |
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| Author |
Gasse, F. |
| Title |
Hydrological changes in the African tropics since the Last Glacial Maximum |
Type |
Journal Article |
| Year |
2000 |
Publication |
Quaternary Science Reviews |
Abbreviated Journal |
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| Volume |
19 |
Issue |
1 |
Pages |
189-211 |
| Keywords |
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| Abstract |
Paleohydrological data from the African tropics and subtropics, including lake, groundwater and speleothem records, are reviewed to show how environments and climates from both hemispheres are inter-related. Although orbitally induced changes in the monsoon strength account for a large part of long-term climatic changes in tropical Africa, the Late Pleistocene–Holocene hydrological fluctuations rather appear to have been a series of abrupt events that reflect complex interactions between orbital forcing, atmosphere, ocean and land surface conditions. During the Last Glacial Maximum (23–18ka BP), most records indicate that generally dry conditions have prevailed in both hemispheres, associated with lower tropical land- and sea-surface temperatures. This agrees with simulations using coupled ocean–atmosphere models, which predict cooling and reduced summer precipitation in tropical Africa; the global hydrological cycle was weaker than today when the extent of large polar ice-sheets and sea-ice was a prominent forcing factor of the Earth’s climate. Glacial-interglacial climatic changes started early: a first wetting/warming phase at ca. 17–16ka BP took place during a period of rapid temperature increase in Antarctica. Next, two drastic arid-humid transitions in equatorial and northern Africa occurred around 15–14.5ka BP and 11.5–11ka BP. Both are thought to match the major Greenland warming events, in concert with the switching of the oceanic thermohaline circulation to modern mode. However, part of the climatic signal after 15 ka BP also seems related to the Antarctica climate. During the Holocene, Africa has also experienced rapid hydrological fluctuations of dramatic magnitude compared to the climatic changes at high latitudes. In particular, major dry spells occurred around 8.4–8ka and 4.2–4ka BP in the northern monsoon domain. Comparison with other parts of the world indicates that these events have a worldwide distribution but different regional expressions. In the absence of large polar ice sheets, changes in the continental hydrological cycles in the tropics may have a significant impact on the global climate system. Climate information gathered here allows to identify geographical and methodological gaps, and raise some scientific questions that remain to be solved to better understand how the tropics respond to changes in major climate-forcing factors, and how they influence climate globally. |
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Edition |
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| ISSN |
0277-3791 |
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no |
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THL @ christoph.kuells @ gasse_hydrological_2000 |
Serial |
96 |
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| Author |
Röttcher, K. |
| Title |
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Type |
Book Chapter |
| Year |
2018 |
Publication |
Risikomanagement und Nachhaltigkeit in der Wasserwirtschaft: Erfolgreiche Navigation durch die Komplexität und Dynamik des Risikos |
Abbreviated Journal |
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Issue |
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Pages |
165-174 |
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| Abstract |
Im vorliegenden Beitrag werden beispielhaft unterschiedliche Ansätze des Risikomanagements und das Verständnis von Nachhaltigkeit in der Wasserwirtschaft dargelegt. Die Darstellung richtet sich insbesondere an Leser aus anderen Fachdisziplinen, wie das Rechts- und Finanzwesen, den Fahrzeug- und Maschinenbau oder auch die sozialen Berufe. Die Zusammenhänge werden überblicksartig mit einzelnen konkreten Beispielen dargestellt mit dem Fokus auf die grundsätzlichen Denk- und Vorgehensweisen. |
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Springer Fachmedien Wiesbaden |
Place of Publication |
Wiesbaden |
Editor |
Michalke, A.; Rambke, M.; Zeranski, S. |
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ISBN |
978-3-658-19684-4 |
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no |
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THL @ christoph.kuells @ Röttcher2018 |
Serial |
90 |
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| Author |
Pisa, P.F.; Nehren, U.; Sebesvari, Z.; Rai, S.; Wong, I. |
| Title |
Chapter 17 – Nature-based solutions to reduce risks and build resilience in mountain regions |
Type |
Book Chapter |
| Year |
2024 |
Publication |
Safeguarding Mountain Social-Ecological Systems |
Abbreviated Journal |
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Issue |
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Pages |
115-126 |
| Keywords |
Nature-based solutions, mountains, climate change adaptation, disaster risk reduction, ecosystem services, SDGs |
| Abstract |
Nature-based solutions (NbS) are increasingly recognized as effective environmental-management measures to address societal challenges such as climate change, water and food security, and disaster risk reduction, thus contributing to human well-being and protecting biodiversity. In addition to being particularly susceptible to these challenges, mountain areas are prone to multihazard conditions, due to their steep topography and particular climatic conditions. NbS can contribute greatly to the sustainable development of mountain ecosystems. This chapter presents examples of NbS in mountain areas around the globe that demonstrate how this approach contributes to achieving sustainable development. |
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Elsevier |
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Editor |
Schneiderbauer, S.; Pisa, P.F.; Shroder, J.F.; Szarzynski, J. |
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ISBN |
978-0-12-822095-5 |
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no |
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THL @ christoph.kuells @ Fontanellapisa2024115 |
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263 |
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Post, V.E.A.; Vassolo, S.I.; Tiberghien, C.; Baranyikwa, D.; Miburo, D. |
| Title |
Weathering and evaporation controls on dissolved uranium concentrations in groundwater – A case study from northern Burundi |
Type |
Journal Article |
| Year |
2017 |
Publication |
Science of The Total Environment |
Abbreviated Journal |
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| Volume |
607-608 |
Issue |
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Pages |
281-293 |
| Keywords |
Geochemical modelling, Hydrochemistry, Lake Tshohoha South, Public health, Radionuclides, Water supply |
| Abstract |
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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no |
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THL @ christoph.kuells @ post_weathering_2017 |
Serial |
132 |
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| Author |
Jroundi, F.; Povedano-Priego, C.; Pinel-Cabello, M.; Descostes, M.; Grizard, P.; Purevsan, B.; Merroun, M.L. |
| Title |
Evidence of microbial activity in a uranium roll-front deposit: Unlocking their potential role as bioenhancers of the ore genesis |
Type |
Journal Article |
| Year |
2023 |
Publication |
Science of The Total Environment |
Abbreviated Journal |
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| Volume |
861 |
Issue |
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Pages |
160636 |
| Keywords |
ISR, Metatranscriptomes, Microbial metabolisms, Ore genesis, Roll-front deposit, Uranium |
| Abstract |
Uranium (U) roll-front deposits constitute a valuable source for an economical extraction by in situ recovery (ISR) mining. Such technology may induce changes in the subsurface microbiota, raising questions about the way their activities could build a functional ecosystem in such extreme environments (i.e.: oligotrophy and high SO4 concentration and salinity). Additionally, more information is needed to dissipate the doubts about the microbial role in the genesis of such U orebodies. A U roll-front deposit hosted in an aquifer driven system (in Zoovch Ovoo, Mongolia), intended for mining by acid ISR, was previously explored and showed to be governed by a complex bacterial diversity, linked to the redox zonation and the geochemical conditions. Here for the first time, transcriptional activities of microorganisms living in such U ore deposits are determined and their metabolic capabilities allocated in the three redox-inherited compartments, naturally defined by the roll-front system. Several genes encoding for crucial metabolic pathways demonstrated a strong biological role controlling the subsurface cycling of many elements including nitrate, sulfate, metals and radionuclides (e.g.: uranium), through oxidation-reduction reactions. Interestingly, the discovered transcriptional behaviour gives important insights into the good microbial adaptation to the geochemical conditions and their active contribution to the stabilization of the U ore deposits. Overall, evidences on the importance of these microbial metabolic activities in the aquifer system are discussed that may clarify the doubts on the microbial role in the genesis of low-temperature U roll-front deposits, along the Zoovch Ovoo mine. |
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0048-9697 |
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no |
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THL @ christoph.kuells @ jroundi_evidence_2023 |
Serial |
138 |
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| Author |
Liesch, T.; Hinrichsen, S.; Goldscheider, N. |
| Title |
Uranium in groundwater — Fertilizers versus geogenic sources |
Type |
Journal Article |
| Year |
2015 |
Publication |
Science of The Total Environment |
Abbreviated Journal |
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| Volume |
536 |
Issue |
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Pages |
981-995 |
| Keywords |
Drinking water, Fertilizer, Geogenic background, Groundwater, Uranium |
| Abstract |
Due to its radiological and toxicological properties even at low concentration levels, uranium is increasingly recognized as relevant contaminant in drinking water from aquifers. Uranium originates from different sources, including natural or geogenic, mining and industrial activities, and fertilizers in agriculture. The goal of this study was to obtain insights into the origin of uranium in groundwater while differentiating between geogenic sources and fertilizers. A literature review concerning the sources and geochemical processes affecting the occurrence and distribution of uranium in the lithosphere, pedosphere and hydrosphere provided the background for the evaluation of data on uranium in groundwater at regional scale. The state of Baden-Württemberg, Germany, was selected for this study, because of its hydrogeological and land-use diversity, and for reasons of data availability. Uranium and other parameters from N=1935 groundwater monitoring sites were analyzed statistically and geospatially. Results show that (i) 1.6% of all water samples exceed the German legal limit for drinking water (10μg/L); (ii) The range and spatial distribution of uranium and occasional peak values seem to be related to geogenic sources; (iii) There is a clear relation between agricultural land-use and low-level uranium concentrations, indicating that fertilizers generate a measurable but low background of uranium in groundwater. |
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0048-9697 |
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no |
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THL @ christoph.kuells @ liesch_uranium_2015 |
Serial |
145 |
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| Author |
N, D.; Panda, B.; S, C.; V, P.M.; Singh, D.K.; L, R.A.; Sahoo, S.K. |
| Title |
Spatio-temporal variations of Uranium in groundwater: Implication to the environment and human health |
Type |
Journal Article |
| Year |
2021 |
Publication |
Science of The Total Environment |
Abbreviated Journal |
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| Volume |
775 |
Issue |
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Pages |
145787 |
| Keywords |
Groundwater, Health risk, Speciation, Stable isotopes, Statistics, Uranium |
| Abstract |
Groundwater overexploitation has resulted in huge scarcity and increase in the demand for water and food security in India. Groundwater in India has been observed to have experienced various water quality issues like arsenic, fluoride, and Uranium (U) contamination, leading to risk in human health. Markedly, the health risk of higher U in drinking water, as well as its chemical toxicity in groundwater have adverse effects on human. This study has reported occurrence of U as an emerging and widespread phenomenon in South Indian groundwater. Data on U in groundwater were generated from 284 samples along the Cretaceous Tertiary boundary within 4 seasons viz. pre-monsoon (PRM), southwest monsoon (SWM), northeast monsoon (NEM), and post-monsoon (POM). High U concentrations (74 μgL−1) showed to be above the World Health Organization’s provisional guideline value of 30 μgL−1. The geochemical, stable isotope and geophysical studies suggested that U in groundwater could vary with respect to season and was noted to be highest during NEM. The bicarbonate (HCO3) released by weathering process during monsoon could affect the saturation index (SI)Calcite and carbonate species of U. However, the primary source of U was found to be due to geogenic factors, like weathering, dissolution, and groundwater level fluctuation, and that, U mobilization could be enhanced due to anthropogenic activities. The findings further indicated that groundwater in the study area has reached the alarming stage of chemical toxicity. Hence, it is urgent and imperative that workable management strategies for sustainable drinking water source be developed and preventive measures be undertaken, relative to these water quality concerns to mitigate their disconcerting effect on human health. |
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0048-9697 |
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no |
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THL @ christoph.kuells @ n_spatio-temporal_2021 |
Serial |
146 |
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| Author |
Sahoo, P.K.; Virk, H.S.; Powell, M.A.; Kumar, R.; Pattanaik, J.K.; Salomão, G.N.; Mittal, S.; Chouhan, L.; Nandabalan, Y.K.; Tiwari, R.P. |
| Title |
Meta-analysis of uranium contamination in groundwater of the alluvial plains of Punjab, northwest India: Status, health risk, and hydrogeochemical processes |
Type |
Journal Article |
| Year |
2022 |
Publication |
Science of The Total Environment |
Abbreviated Journal |
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| Volume |
807 |
Issue |
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Pages |
151753 |
| Keywords |
Agrochemicals, Geogenic contamination, Punjab, Salinity, Shallow aquifer, Uranium enrichment |
| Abstract |
Despite numerous studies, there are many knowledge gaps in our understanding of uranium (U) contamination in the alluvial aquifers of Punjab, India. In this study, a large hydrogeochemical dataset was compiled to better understand the major factors controlling the mobility and enrichment of uranium (U) in this groundwater system. The results showed that shallow groundwaters (\textless60 m) are more contaminated with U than from deeper depths (\textgreater60 m). This effect was predominant in the Southwest districts of the Malwa, facing significant risk due to chemical toxicity of U. Groundwaters are mostly oxidizing and alkaline (median pH: 7.25 to 7.33) in nature. Spearman correlation analysis showed that U concentrations are more closely related to total dissolved solids (TDS), salinity, Na, K, HCO3−, NO3− Cl−, and F− in shallow water than deep water, but TDS and salinity remained highly correlated (U-TDS: ρ = 0.5 to 0.6; U-salinity: ρ = 0.5). This correlation suggests that the salt effect due to high competition between ions is the principal cause of U mobilization. This effect is evident when the U level increased with increasing mixed water species (Na-Cl, Mg-Cl, and Na-HCO3). Speciation data showed that the most dominant U species are Ca2UO2(CO3)2− and CaUO2(CO3)3−, which are responsible for the U mobility. Based on the field parameters, TDS along with pH and oxidation-reduction potential (ORP) were better fitted to U concentration above the WHO guideline value (30 μg.L−1), thus this combination could be used as a quick indicator of U contamination. The strong positive correlation of U with F− (ρ = 0.5) in shallow waters indicates that their primary source is geogenic, while anthropogenic factors such as canal irrigation, groundwater table decline, and use of agrochemicals (mainly nitrate fertilizers) as well as climate-related factors i.e., high evaporation under arid/semi-arid climatic conditions, which result in higher redox and TDS/salinity levels, may greatly affect enrichment of U. The geochemical rationale of this study will provide Science-based-policy implications for U health risk assessment in this region and further extrapolate these findings to other arid/semi-arid areas worldwide. |
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0048-9697 |
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Approved |
no |
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THL @ christoph.kuells @ sahoo_meta-analysis_2022 |
Serial |
150 |
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