Records |
Author |
Edmunds, W.M.; Shand, P.; Hart, P.; Ward, R.S. |
Title |
The natural (baseline) quality of groundwater: a UK pilot study |
Type |
Journal Article |
Year |
2003 |
Publication |
Science of The Total Environment |
Abbreviated Journal |
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Volume |
310 |
Issue |
1 |
Pages |
25-35 |
Keywords |
Baseline quality, Groundwater, Hydrogeochemistry, Monitoring, Water Policy |
Abstract |
Knowledge of the natural baseline quality of groundwaters is an essential prerequisite for understanding pollution and for imposing regulatory limits. The natural baseline of groundwaters may show a range of concentrations depending on aquifer mineralogy, facies changes, flow paths and residence time. The geochemical controls on natural concentrations are discussed and an approach to defining baseline concentrations using geochemical and statistical tools is proposed. The approach is illustrated using a flowline from the Chalk aquifer in Berkshire, UK where aerobic and anaerobic sections of the aquifer are separately considered. The baseline concentrations for some elements are close to atmospheric values whereas others evolve through time-dependent water–rock interaction. Certain solutes (K, NH4+), often considered contaminants, reach naturally high concentrations due to geochemical controls; transition metal concentrations are generally low, although their concentrations may be modified by redox controls. It is recommended that the baseline approach be incorporated into future management strategies, notably monitoring. |
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0048-9697 |
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THL @ christoph.kuells @ edmunds_natural_2003 |
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166 |
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Author |
Milena-Pérez, A.; Piñero-García, F.; Benavente, J.; Expósito-Suárez, V.M.; Vacas-Arquero, P.; Ferro-García, M.A. |
Title |
Uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes |
Type |
Journal Article |
Year |
2021 |
Publication |
Journal of Environmental Radioactivity |
Abbreviated Journal |
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Volume |
227 |
Issue |
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Pages |
106503 |
Keywords |
234U/238U, Betic cordillera, Groundwater, Hydrogeochemistry, Uranium natural isotopes |
Abstract |
This paper studies the uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes from 52 groundwater samples in the province of Granada (Betic Cordillera, southeastern Spain). According to the geological complexity of the zone, three groups of samples have been considered. In Group 1 (thermal waters; longest residence time), the average uranium content was 2.63 ± 0.16 μg/L, and 234U/238U activity ratios (AR) were the highest of all samples, averaging 1.92 ± 0.30. In Group 2 (mainly springs from carbonate aquifers; intermediate residence time), dissolved uranium presented an average value of 1.34 ± 0.13 μg/L, while AR average value was 1.38 ± 0.25. Group 3 comes from pumping wells in a highly anthropized alluvial aquifer. In this group, where the residence time of the groundwater is the shortest of the three, average uranium content was 5.28 ± 0.26 μg/L, and average AR is the lowest (1.17 ± 0.12). In addition, the high dissolved uranium value and the low AR brought to light the contribution of fertilizers (Group 3). In the three groups, 235U/238U activity ratios were similar to the natural value of 0.046. Therefore, 235U detected in the samples comes from natural sources. This study is completed with the determination of major ions and physicochemical parameters in the groundwater samples and the statistical analysis of the data by using the Principal Component Analysis. This calculation indicates the correlation between uranium isotopes and bicarbonate and nitrate anions. |
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0265-931x |
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THL @ christoph.kuells @ milena-perez_uranium_2021 |
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112 |
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Belz, L.; Schüller, I.; Wehrmann, A.; Köster, J.; Wilkes, H. |
Title |
The leaf wax biomarker record of a Namibian salt pan reveals enhanced summer rainfall during the Last Glacial-Interglacial Transition |
Type |
Journal Article |
Year |
2020 |
Publication |
Palaeogeography, Palaeoclimatology, Palaeoecology |
Abbreviated Journal |
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Volume |
543 |
Issue |
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Pages |
109561 |
Keywords |
-Alkanes, -Alkanols, Late Quaternary, Organic geochemistry, Palaeohydrology, Southern Africa |
Abstract |
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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