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  • Weise, Stephan M.
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  • 1
    Language: English
    In: Procedia Earth and Planetary Science, 2017, Vol.17, pp.574-577
    Description: Lithium and its isotopes has generally been used as a proxy for silicate weathering and only in a few case studies investigated the link between Lithium isotope systematics of surface and ground waters with respect to residence times in crustal reservoirs and aquifers. However, the processes controlling the Lithium isotope fractionation in such systems are not fully understood, yet. In order to gain a better understanding of how Lithium isotopes are fractionated in large catchments we analyzed Lithium concentrations and Lithium isotope compositions of different water reservoirs (rivers, groundwater, thermal water and lakes) of a high alpine granitic catchment in the Pamir Mountains. We also determined the Lithium concentration and Lithium isotope composition of the (granitic) basement as well as the suspended particulate matter (SPM) in the waters. We observe large isotopic variations in the water samples (from δ Li = +3 to +36‰) and light isotopic compositions for the bedrock and SPM (δ Li = -14 to +1.5‰). The wide span of Li isotope composition in the water samples reflects the weathering of silicate rock along the flow path of the (sub) surface water within the catchment.
    Keywords: Lithium Isotopes ; River Water ; Ground Water ; Granite ; Pamir ; Central Asia ; Geology
    ISSN: 1878-5220
    E-ISSN: 1878-5220
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  • 2
    Language: English
    In: Isotopes in Environmental and Health Studies, 01 September 2010, Vol.46(3), pp.257-258
    Keywords: Chemistry ; Physics
    ISSN: 1025-6016
    E-ISSN: 1477-2639
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  • 3
    Language: English
    In: Geochimica et Cosmochimica Acta, 2009, Vol.73(4), pp.911-922
    Description: Groundwater is an important and often exclusive water resource in arid and semi-arid regions. The aim of the present paper was to gain insight into the processes and conditions that control the deterioration of groundwater quality in the semi-arid Kalahari of Botswana. Measurements of He, He, Ne, Ne, and of C of dissolved inorganic carbon (DIC) were combined with existing isotopic and hydrochemical data to investigate groundwater from the Ntane Sandstone Aquifer, which is affected by high nitrate concentrations of non-anthropogenic origin. All groundwater samples revealed neon concentrations in excess to air-saturated water, which we attributed to the addition of excess air during recharge. Neon concentrations ranged from values close to air saturation for C DIC rich samples (up to 80.5%MC) up to values of 90% in excess to air-saturated water for lower C DIC contents (2.6–61.3%MC). A strong linear correlation of excess Ne with nitrate concentrations suggests an intimate connection between groundwater quality and the processes and conditions during groundwater recharge. Low groundwater recharge rates under present-day semi-arid conditions are associated with low amounts of excess Ne and elevated nitrate concentrations. In contrast to this, higher excess Ne values in groundwater of lower C DIC and nitrate contents indicate that the high quality groundwater end-member presumably is related to higher groundwater table fluctuations during wetter climatic conditions in the past. We attribute the decline in groundwater quality with respect to nitrate to a decreasing rate and temporal variability of groundwater recharge, and to concurrent changes in biogeochemical activities following a transition to a drier climate during the Holocene. Under such conditions, a much stronger decrease in groundwater recharge compared to the release of nitrate from soil organic matter may result in elevated nitrate concentrations in the vadose zone and groundwater. This implies a strong impact of climate change on the transport of solutes like nitrate through the vadose zone which needs to be considered in predictions of future groundwater quality.
    Keywords: Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 4
    Language: English
    In: Water Research, 2007, Vol.41(15), pp.3259-3270
    Description: In this study, we used isotopic ( O, H, S-SO ) and chemical tracers (boron) to assess the sources and transport processes of the micropollutants carbamazepine, galaxolide, and bisphenol A in groundwater underlying the city of Halle (Saale), Germany. Their ubiquitous presence in urban groundwater results from a combination of local river water infiltration, sewer exfiltration, and urban stormwater recharge. Attenuation during transport with infiltrating river water increased from carbamazepine (0–60%) to galaxolide (60–80%) in accordance with their increasing sorption affinity and decreasing recalcitrance against biodegradation. Distinctly higher attenuation during transport was found for carbamazepine (85–100%) and galaxolide (95–100%) if micropollutants originated from sewer exfiltration. Most likely, this is related to higher contents of organic matter and higher transit times of the respective flow paths. Although attenuation undoubtedly also affects the transport of bisphenol A, quantification is limited due to additional contributions from the urban stormwater recharge. As a consequence, micropollutant loads in groundwater indicate that groundwater discharge may dominate the export of bisphenol A from urban areas.
    Keywords: Urban Groundwater ; Pharmaceuticals ; Personal Care Products ; Endocrine Disruptors ; Stable Isotopes ; Sewer Exfiltration ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 5
    In: Water Resources Research, December 2006, Vol.42(12), pp.n/a-n/a
    Description: Nitrate pollution from agricultural activities often persistently affects groundwater quality due to long residence times in the vadose and saturated zone. In this study we used a lumped parameter approach to estimate the residence time of groundwater and nitrate from the agriculturally used Jahna‐Aue drinking water catchment in Saxonia, Germany. Inverse modeling of measured concentrations of tritium and tritiogenic He revealed consistent mean residence times between 25 and 50 years for the young, nitrate‐rich groundwater component, and high contributions (〉75%) of an old, tracer‐free, and nitrate‐poor groundwater. The obtained age distributions are in accordance with the complex hydrogeological situation of the investigated catchment, suggesting that the shallow and therefore most vulnerable part of the aquifer is not connected to the production wells. High residence times are supported by low concentrations of CFCs and by radiogenic He as an independent age indicator. CFC concentrations only yield lower age limits due to identified problems with CFC contamination. Using the tracer‐calibrated age distributions, future nitrate concentrations in the production wells most probably will remain below the drinking water limit because of the high dilution with old, nitrate‐poor groundwater. Deterioration of the groundwater quality with respect to nitrate may occur if the groundwater pumping regime is changed so that the fraction of the younger, nitrate‐bearing water is increased.
    Keywords: Groundwater Age Distribution ; Lumped Parameter Model ; Nitrate Pollution ; Nitrate Stable Isotopes ; Tritium/He
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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