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  • 1
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.381-393
    Description: In this study near-continuous time series of nitrate, electrical conductivity, and discharge were used to identify the dominating hydrological mechanisms that control nitrate export dynamics in two agricultural catchments. The main goal was to assess relationships between contrasting event based as well as long-term nitrate transport behaviour and catchment hydrology. Data records were obtained from online probes that allow field based high-frequency analyses over long time periods. The catchments of the Ammer River (southwestern Germany) and the Weida River (eastern Germany) are similar with respect to size (~100 km²), morphology, and climate and are dominated by agricultural use. Main differences are the stronger urbanization and the occurrence of karstic rocks in the Ammer catchment. Nitrate concentrations are high in water of both streams and range mostly between 20 and 50 mg l −1 . Nitrate export in the Ammer catchment is dominated by baseflow and a minor second, diluting runoff component generated in urbanized areas. In contrast, nitrate dynamics of the Weida catchment is governed by the interplay of at least three runoff components, while the largest amount of nitrate is mobilized intermittently by a delayed fast component generated in the catchment’s soils during wet conditions. These interpretations, derived with one online probe at the outlet of each catchment, are well in line with the former modeling results. This study shows that high-resolution data obtained by online techniques offers a large potential to improve the conceptualization of dominating flow and transport processes at catchment scales at relatively low costs and effort.
    Keywords: Nitrate export ; Catchment ; Hydrology ; High-frequency monitoring ; Online probe
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 2
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.349-358
    Description: Performing tracer tests using artificial tracer compounds is a common practice to characterize natural streams regarding their (reactive) transport properties. Recently, the fluorescent compound resazurin was introduced as a reactive stream tracer to quantify hyporheic exchange and metabolic activity of streams. This tracer, together with its reaction product resorufin and a conservative tracer (in our case fluorescein), provides additional information about transport properties of the stream and its hyporheic zone and can therefore overcome restrictions that are commonly affiliated with the use of conservative tracers alone. However, all previously published studies using this tracer system were based on manual sampling of the water. This usually limits the number of measurements and thus the achievable temporal resolution, and potentially endangers data quality due to inadequate handling of samples. In this paper, a modified version of the GGUN-FL30 on-line fluorometer is presented in which the optics have been modified to allow measuring the concentrations of all three tracers simultaneously at intervals of 10 s. Experiments under controlled and natural conditions showed that the performance of the on-line fluorometer regarding tracer separation efficiency and practical detection limits is comparable to a high-performance laboratory spectrofluorometer. Furthermore, suggestions are given on how to correct tracer signal fluctuations caused by temporal changes in temperature and pH that might occur during a field tracer test.
    Keywords: Fluorometer ; Tracer test ; Groundwater/surface water interaction ; Resazurin
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 3
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.359-372
    Description: First results of a multi-disciplinary hyporheic monitoring study are presented from the newly established Steinlach Test Site in Southern Germany. The site is located in a bend of the River Steinlach (mean discharge of 1.8 m³/s) underlain by an alluvial sandy gravel aquifer connected to the stream. The overall objective is a better understanding of hyporheic exchange processes at the site and their interrelations with microbial community dynamics and biochemical reactions at the stream–groundwater interface. The present paper focuses on the distribution of lateral hyporheic exchange fluxes and their associated travel times at the Steinlach Test Site. Water level dynamics in various piezometers correspond to the different domains of hydraulic conductivity in the shallow aquifer and confirms hyporheic exchange of infiltrated stream water across the test site. Hydrochemical compositions as well as increased damping of continuous time series of electrical conductivity (EC) and temperature at the respective piezometers confirmed the inferred distribution of hyporheic flowpaths. Mean travel times ranging from 0.5 days close to the stream to more than 8 days in the upstream part of the test site could be estimated from deconvolution of EC and δ 18 O–H 2 O data. The travel times agree well with the presumed flowpaths. Mg/Ca ratios as well as model fits to the EC and δ 18 O data indicate the presence of an additional water component in the western part of the test site which most likely consists of hillslope water or groundwater. Based on the mean travel times, the total lateral hyporheic exchange flux at the site was estimated to be of the order of 1–2 L/s.
    Keywords: Hyporheic zone ; Stream–groundwater interaction ; Travel time distribution ; Deconvolution ; Monitoring
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 4
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.317-333
    Description: Sustainable water quality management requires a profound understanding of water fluxes (precipitation, run-off, recharge, etc.) and solute turnover such as retention, reaction, transformation, etc. at the catchment or landscape scale. The Water and Earth System Science competence cluster (WESS, http://www.wess.info/ ) aims at a holistic analysis of the water cycle coupled to reactive solute transport, including soil–plant–atmosphere and groundwater–surface water interactions. To facilitate exploring the impact of land-use and climate changes on water cycling and water quality, special emphasis is placed on feedbacks between the atmosphere, the land surface, and the subsurface. A major challenge lies in bridging the scales in monitoring and modeling of surface/subsurface versus atmospheric processes. The field work follows the approach of contrasting catchments, i.e. neighboring watersheds with different land use or similar watersheds with different climate. This paper introduces the featured catchments and explains methodologies of WESS by selected examples.
    Keywords: Water and solute fluxes ; Water quality ; Catchments ; Land-surface atmosphere exchange ; Processes and feedbacks ; Modeling ; Monitoring
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 5
    Language: English
    In: Journal of Soils and Sediments, 2008, Vol.8(1), pp.23-33
    Description: Byline: Gerhard Strauch (1), Monika Moder (2), Rainer Wennrich (2), Karsten Osenbruck (3), Hans-Reinhard Glaser (1), Timo Schladitz (1), Claudia Muller (1), Kristin Schirmer (4), Frido Reinstorf (1), Mario Schirmer (1) Keywords: Carbamacepine; endocrine disrupters; gadolinium; indicators; stable isotopes; urban water; xenobiotics Abstract: Background, Aim and Scope Our study focuses on the indication of anthropogenic impacts on the urban surface and groundwater in large cities, demonstrated for the cities of Halle/Saale and Leipzig (Germany). For the study we selected indicator substances such as xenobiotics, trace elements, and stable isotopes which are connected to human activities in urban areas. The xenobiotics reported here are the pharmaceutical carbamacepine, the polycylic musk compounds galaxolide and tonalide, the life style product caffeine, and industrial chemicals such as bisphenol A and t-nonylphenol. The investigated xenobiotics pose largely unknown risks to human health and the aquatic ecosystem. Trace elements are represented by the rare earth element gadolinium (Gd), used as magnetic resonance imaging contrast substance. Nitrogen isotopes in dissolved nitrate characterize the origin of nitrogen compounds, mixing and reaction processes. Methodology River water was sampled along the flow path of the rivers Saale and Weisse Elster through the city of Halle/Saale, the rivers Luppe and Weisse Elster through the city of Leipzig. Separate samples were collected from the effluent of the local waste water treatment plants. Groundwater from Quaternary plain aquifers along the rivers and from different urban locations was collected at the same time. The indicators were analysed and assessed according to their sources, concentration and distribution patterns. Results and Discussion Based on the nitrogen isotopic signature, dissolved nitrate in river water of the Saale was referred mainly to two sources: the effluent of the water treatment plant and a mixture of diffusive inputs from rain water channels, sewage leakages and agriculture activities along the rivers. The Gd anomaly was recognized in surface water of both cities, particularly in the effluent of the water treatment plants, but clearly attenuated in groundwater. We measured concentrations of xenobiotics in river and sewer water between 10 and 60,000 ng L.sup.-1, and, in groundwater, one order of magnitude lower. Distinctions of xenobiotic patterns were found in river water before and after the effluent of treated waste water into the rivers. Degradation of endocrine disrupters and fragrances, but also persistence of carbamacepine were recognized as essential processes during waste water treatment. At the study site Halle/Saale, mass balances were set up for xenobiotics and water fluxes. Conclusions At both sites, we demonstrated that indicators such as xenobiotics, gadolinium, and nitrogen isotopes are suitable for assessing anthropogenic impacts on urban water. However, the behaviour of these indicators in surface and groundwater has to be considered according to the different geochemical environments. Author Affiliation: (1) Department of Hydrogeology, UFZ Helmholtz Centre for Environmental Research, Leipzig, Germany (2) Deptartment of Analytical Chemistry, UFZ Helmholtz Centre for Environmental Research, Leipzig, Germany (3) Department of Isotope Hydrology, UFZ Helmholtz Centre for Environmental Research, Theodor-Lieser-Str. 4, 06120, Halle, Germany (4) Department of Cell Toxicology, UFZ Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318, Leipzig, Germany Article History: Registration Date: 03/03/2007 Received Date: 06/11/2006 Accepted Date: 11/06/2007 Online Date: 12/06/2007
    Keywords: Carbamacepine ; endocrine disrupters ; gadolinium ; indicators ; stable isotopes ; urban water ; xenobiotics
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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