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  • 1
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.429-441
    Description: The impact of diffuse pollution, agricultural land use and climate change on the long-term response of subsurface–surface water quality is not well understood, but is a prerequisite for evaluation of water management options. The goal of this study is to model geochemical evolution of water chemistry from the infiltration through soil into the unsaturated zone, transport through bedrocks and granular aquifers to a river in order to identify zones of steep concentration gradients and high dynamics under transient flow conditions. A numerical model was constructed comprising a 2-D 1,500 m × 150 m vertical cross-section of typical sedimentary rock formations, a glacio-fluvial quaternary gravel aquifer in the valley and soil layers. The model coupled saturated/un-saturated flow and reactive transport under steady state and transient conditions. Geochemical interactions, include intra-aqueous kinetic reactions of oxygen with dissolved organic matter, as well as kinetics of carbonate dissolution/precipitation. This model section was chosen to provide insight in to the principal processes and time scales affecting water chemistry along different flow paths. The numerical simulator MIN3P was used, a finite volume program for variably saturated subsurface flow and multi-component reactive transport. The results show that subsurface water residence times range from approximately 2 to 2,000 years. Different zones are to be expected with respect to the development of mineral equilibria; namely, purely atmospherically influenced, as well as open and closed system carbonate dissolution. Short-term responses to daily averaged changes in precipitation, however, are only visible to some extent in the shallower and near-river parts of flow system and solute loads. This can most likely be explained by directional changes in flow paths, indicating that equilibrium geochemical condition predominate at the hillslope scale, i.e. water quality depends on transport pathways rather than on kinetic effects. The extent of reducing conditions is controlled by the presence of organic-rich layers (i.e. peat deposits), the dissolution kinetics of aquifer organic matter and the subsequent mixing with oxygenated water by hydrodynamic dispersion.
    Keywords: Rock water interaction ; Water chemistry evolution ; Hydrogeochemical modelling ; Water residence time ; Catchment hydrology
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 2
    Language: English
    In: Environmental Earth Sciences, 5/2013, Vol.69(2), pp.313-315
    Keywords: Geology;
    ISSN: 1866-6280
    E-ISSN: 1866-6299
    Source: Springer (via CrossRef)
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  • 3
    Language: English
    In: Environmental Earth Sciences, 2013, Vol.69(2), pp.373-380
    Description: Transport of hydrophobic organic pollutants in rivers is mainly coupled to transport of suspended particles. Turbidity measurements are often used to assess the amount of suspended solids in water. In this study, a monitoring campaign is presented where the total concentration of polycyclic aromatic hydrocarbons (PAHs), the amount of total suspended solids (TSS), and turbidity was measured in water samples from five neighboring catchments in southwest Germany. Linear correlations of turbidity and TSS were obtained which were in close agreement to the literature data. From linear regressions of turbidity versus total PAH concentrations in water, mean concentrations of PAH on suspended particles could be calculated and these varied by catchment. These values furthermore comprise a robust measure of the average sediment quality in a given catchment. Since in the catchments investigated in this study, PAH concentrations on suspended particles were stable over a large turbidity range (1–114 Nephelometric Turbidity Units), turbidity could be used as a proxy for total PAHs and likely other highly hydrophobic organic pollutants in river water if the associated correlations are established. Based on that, online monitoring of turbidity (e.g., by optical backscattering sensors) seems very promising to determine annual pollutant fluxes.
    Keywords: Turbidity ; Total suspended solids ; Hydrophobic pollutants ; Particle-facilitated transport ; Catchment hydrology
    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: German
    In: Grundwasser, 2004, Vol.9(2), pp.98-108
    Description: Im Abstrom der „ehemaligen Abfalldeponie Osterhofen“ wurden Konzentrationen an Ammonium festgestellt, die deutlich über dem in Baden-Württemberg geltenden Prüfwert liegen. Im Rahmen detaillierter Natural Attenuation (NA) Untersuchungen wurde überprüft, inwieweit die Nutzung mikrobiologischer Abbau- und Rückhalteprozesse des Ammoniums eine geeignete Entscheidungsoption für den Standort darstellt. Das Ergebnis der hierbei im Wesentlichen durchgeführten Frachtbestimmungen (mittels Immissionspumpversuchen) sowie einer konzeptionellen numerischen Modellierung des Ammoniumabbaues am Standort war, dass ein mikrobiologischer Abbau des Ammoniums zu Nitrat stattfindet (70–85 % Abbau innerhalb einer Distanz von ca. 450 m), dass allerdings aufgrund der diffusiv-/dispersiv bedingten langsamen Zufuhr von Sauerstoff in die Abstromfahne ein insgesamt ca. 550–680 m langer, stationärer Reaktionsraum existiert. Eine Gefahr für das Grundwasser im weiteren Abstrom der Deponie konnte ausgeschlossen werden. Eine gezielte Überwachung der NA-Prozesse kann am Standort an die Stelle einer aktiven Sanierungsmaßnahme treten. In groundwater downgradient of the former municipal landfill site “Osterhofen” concentrations of Ammonium much above the legal limit were detected. Based on detailed site investigations it was evaluated whether natural attenuation (NA) may be used as a contaminated land management option at the site. Investigations were mainly based on the determination of contaminant mass flow rates (by integral pumping tests) and numerical conceptual modelling of the ammonium degradation. As result it was found that biodegradation of ammonium is very effective (70–85 % degradation within a distance of approx. 450 m). Because oxygen supply into the plume is limited by transverse mixing a steady state plume of approx. 550–680 m in length exists. Since beyond this reactive zone no further risk for groundwater arises, monitored natural attenuation (MNA) is an appropriate contaminated land management option at the site.
    Keywords: Geosciences ; Environmental Sciences ; Geography;
    ISSN: 1430-483X
    E-ISSN: 1432-1165
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  • 6
    Language: German
    In: Grundwasser, 2004, Vol.9(1), pp.43-53
    Description: Im Abstrom des „ehemaligen Gaswerkes Kehl“ wurden Konzentrationen an PAK festgestellt, die über dem geltenden Prüfwert liegen. Im Rahmen detaillierter Natural Attenuation-Untersuchungen wurde überprüft, inwieweit die Nutzung mikrobiologischer Abbau- und Rückhalteprozesse der PAK eine geeignete Entscheidungsoption für den Standort darstellt. Hierzu kamen im Wesentlichen Frachtbestimmungen entlang von zwei aufeinander folgenden Kontrollebenen (mittels Immissionspumpversuchen) sowie numerische Modellierungen zum Ausbreitungsverhalten der PAK am Standort zum Einsatz. Die Ergebnisse zeigten, dass für die 2-3-Ring PAK ein effektiver mikrobiologischer Abbau innerhalb eines Reaktionsraums von ca. 130 m stattfindet. Für die ≥ 4-Ring PAK ist v. a. aufgrund nur niedriger Konzentrationen im direkten Abstrom nicht mit Prüfwertüberschreitungen im weiteren Abstrom zu rechnen. Sorptionsprozesse am Aquifermaterial führen darüber hinaus zu einem stark retardierten Transport dieser Verbindungen. Auf Basis der Ergebnisse hat die Altlastenbewertungskommission die Implementierung einer aktiven Sanierungsmaßnahme ausgesetzt und sich für die gezielte Überwachung der NA-Prozesse entschieden. In groundwater downgradient of the former gas work site “City of Kehl” concentrations of PAH above the legal limit were detected. Based on detailed site investigations it was evaluated whether monitored natural attenuation (MNA) may be used as a contaminated land management option at the site. Investigations were mainly based on the determination of contaminant mass flow rates at two consecutive control planes (by integral pumping tests) and numerical transport modelling of PAH. As result it was found that 2-3-ring PAH are biodegraded within a distance of approx. 130 m. Due to already low concentrations directly downgradiant of the source zone no exceedance of the legal limits beyond the reactive zone is expected for ≥ 4-Ring PAH. In addition transport of these compounds is highly retarded due to strong sorption processes. Based on the results it was decided to rely on monitored natural attenuation as a contaminated land management option at the site.
    Keywords: Geosciences ; Environmental Sciences ; Geography;
    ISSN: 1430-483X
    E-ISSN: 1432-1165
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  • 7
    Language: German
    In: Grundwasser, 1997, Vol.2(3), pp.133-138
    Description: Anhand von definierten Laborversuchen zum Sorptionsverhalten von hydrophoben organischen Schadstoffen wurde der Zusammenhang zwischen den sorptionsrelevanten Parametern und den physikalischen und chemischen Eigenschaften der Gesteine untersucht. Zu diesem Zweck wurden an den verschiedenen petrographischen Komponenten eines Kieses aus dem Neckartal und an den Festgesteinen aus deren Liefergegieten Experimente zur Sorptionskapazität und -kinetik von Phenanthren durchgeführt. Die Sorptionskapazität hängt vom Gehalt an organisch gebundenem Kohlenstoff und von der Zusammensetzung des organischen Materials ab. Die Sorptionskinetik folgt dem Modell der Intrapartikel-Porendiffusion. Die Diffusivität kann analog zu Archie's Law aus der Porosität abgeleitet werden. Prozesse wie Verwitterung und Transport haben keinen wesentlichen Einfluß auf die sorptionsrelevanten Parameter. In laboratory batch experiments equilibrium sorption and sorption kinetics of phenanthrene in the different petrographic components of a gravel aquifer material (river Neckar valley) and the source rocks of the valley sediments were investigated. The sorption coefficients depend on organic carbon content and the composition of the organic matter. The sorption kinetics follow the intraparticle pore diffusion modell. Diffusivities can be predicted from the intraparticle porosity analogous to Archie's Law. No significant influence of weathering processes and transport of the aquifer sediments was found for the sorption parameters.
    Keywords: Earth Sciences ; Hydrogeology ; Hydrology/Water Resources ; Water Quality/Water Pollution ; Geoengineering, Foundations, Hydraulics ; Soil Science & Conservation ; Geoecology/Natural Processes ; Environmental Sciences ; Geography;
    ISSN: 1430-483X
    E-ISSN: 1432-1165
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