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  • Rugner, Hermann  (8)
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  • 1
    Language: English
    In: Science of the Total Environment, 01 January 2016, Vol.540, pp.444-454
    Description: Increasing numbers of organic micropollutants are emitted into rivers via municipal wastewaters. Due to their persistence many pollutants pass wastewater treatment plants without substantial removal. Transport and fate of pollutants in receiving waters and export to downstream ecosystems is not well understood. In particular, a better knowledge of processes governing their environmental behavior is needed. Although a lot of data are available concerning the ubiquitous presence of micropollutants in rivers, accurate data on transport and removal rates are lacking. In this paper, a mass balance approach is presented, which is based on the Lagrangian sampling scheme, but extended to account for precise transport velocities and mixing along river stretches. The calculated mass balances allow accurate quantification of pollutants' reactivity along river segments. This is demonstrated for representative members of important groups of micropollutants, e.g. pharmaceuticals, musk fragrances, flame retardants, and pesticides. A model-aided analysis of the measured data series gives insight into the temporal dynamics of removal processes. The occurrence of different removal mechanisms such as photooxidation, microbial degradation, and volatilization is discussed. The results demonstrate, that removal processes are highly variable in time and space and this has to be considered for future studies. The high precision sampling scheme presented could be a powerful tool for quantifying removal processes under different boundary conditions and in river segments with contrasting properties.
    Keywords: Micropollutants ; River Segments ; Mass Balances ; Removal Processes ; Diurnal Patterns ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 2
    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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  • 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: Applied Geochemistry, 2007, Vol.22(12), pp.2606-2617
    Description: Oxidation of reduced pollutants such as in groundwater often takes place at steep redox gradients where oxygenated water is being mixed into polluted water such as landfill leachate. In order to identify controlling parameters and quantify the influence of environmental factors for degradation, sensitivity analysis was performed by means of scenario specific numerical modelling. Geometrical factors such as aquifer thickness have been shown to be very influential on the capability of natural attenuation of pollutants in groundwater. The scenarios investigated here include biodegradation at redox gradients in groundwater, so called fringe processes, for (i) a partly contaminated aquifer with two reaction fronts, (ii) and a spatially variable aquifer thickness. In addition, (iii) the influence of groundwater recharge and (iv) restricted supply of O to contaminated water by slow dispersion and diffusion across the capillary fringe are investigated. Contaminated aquifer thickness, zones of enhanced mixing due to flow focussing and diffusion/dispersion coefficients in the capillary fringe are identified qualitatively as controlling factors for natural attenuation under complex conditions, whereas predictive functions will require further research.
    Keywords: Geology
    ISSN: 0883-2927
    E-ISSN: 1872-9134
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  • 5
    Language: English
    In: Environmental Science and Policy, 2006, Vol.9(6), pp.568-576
    Description: The prospect of more efficient, economically advantageous management strategies has driven the development of contaminated land management concepts particularly for large and complex contaminated sites during the last years. Consequently, the conscious and controlled use of naturally occurring degradation and retardation processes of pollutants in the subsurface (monitored natural attenuation—MNA) has gained increasing attention. Today, there are in principle two different MNA concepts available: risk-based MNA concepts as used, for example, in the USA, and MNA concepts which rely on a precautionary principle of soil and groundwater protection as developed, for example, in Germany. Based on a discussion of the virtues and limitations of these concepts, the manuscript provides a review and a synthesis of these concepts as well as recommendations for further improvements.
    Keywords: Monitored Natural Attenuation ; Degradation and Retardation of Pollutants ; Contaminated Land Management ; Groundwater Remediation ; Decision Making ; Environmental Sciences
    ISSN: 1462-9011
    E-ISSN: 1873-6416
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  • 6
    Language: English
    In: Science of the Total Environment, 10 January 2019, Vol.647, pp.645-652
    Description: Transport of hydrophobic pollutants in rivers such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals is often facilitated by suspended sediment particles, which are typically mobilized during high discharge events. Suspended sediments thus represent a means of transport for particle related pollutants within river reaches and may represent a suitable proxy for average pollutant concentrations estimation in a river reach or catchment. In this study, multiple high discharge/turbidity events were sampled at high temporal resolution in the Globaqua River Basins Sava (Slovenia, Serbia), Adige (Italy), and Evrotas (Greece) and analysed for persistent organic pollutants such as PAHs (polycyclic aromatic hydrocarbons) or PCBs (polychlorinated biphenyls) and heavy metals. For comparison, river bed sediment samples were analysed as well. Further, results are compared to previous studies in contrasting catchments in Germany, Iran, Spain, and beyond. Overall results show that loadings of suspended sediments with pollutants are catchment-specific and relatively stable over time at a given location. For PAHs, loadings on suspended particles mainly correlate to urban pressures (potentially diluted by sediment mass fluxes) in the rivers, whereas metal concentrations mainly display a geogenic origin. By cross-comparison with known urban pressure/sediment yield relationships (e.g. for PAHs) or soil background values (for metals) anthropogenic impact – e.g. caused by industrial activities – may be identified. Sampling of suspended sediments gives much more reliable results compared to sediment grab samples which typically show a more heterogeneous contaminant distribution. Based on mean annual suspended sediment concentrations and distribution coefficients of pollutants the fraction of particle facilitated transport versus dissolved fluxes can be calculated.
    Keywords: Particle Associated Pollutants ; Suspended Sediments ; Persistent Organic Pollutants ; Heavy Metals ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 7
    Language: English
    In: Waste Management, 2009, Vol.29(2), pp.839-850
    Description: In this study, contaminant leaching from three different secondary materials (demolition waste, municipal solid waste incineration ash, and blast furnace slag) to groundwater is assessed by numerical modeling. Reactive transport simulations for a noise protection dam and a road dam (a typical German autobahn), in which secondary materials are reused as base layers, were performed to predict the breakthrough of a conservative tracer (i.e., a salt) and sorbing contaminants (e.g., PAHs like naphthalene and phenanthrene or heavy metals) at the groundwater table. The dam constructions have a composite architecture with soil covers in inclined layers and distinct contrasts in the unsaturated hydraulic properties of the used materials. Capillary barrier effects result in strong spatial variabilities of flow and transport velocities. Contaminant breakthrough curves at the groundwater table show significant tailing due to slow sorption kinetics and a wide distribution of travel times. While conservative tracer breakthrough depends primarily on subsoil hydraulic properties, equilibrium distribution coefficients and sorption kinetics represent additional controlling factors for contaminant spreading. Hence, the three secondary materials show pronounced differences in the temporal development of leached contaminant concentrations with consequences for breakthrough times and peak concentrations at the groundwater table. Significant concentration reductions due to dispersion occur only if the source concentrations decrease significantly prior to the arrival of the contaminant at the groundwater table. Biodegradation causes significant reduction of breakthrough concentrations only if flow velocities are low.
    Keywords: Engineering ; Chemistry
    ISSN: 0956-053X
    E-ISSN: 1879-2456
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  • 8
    Language: English
    In: Environmental Toxicology and Chemistry, August 1999, Vol.18(8), pp.1673-1678
    Description: Groundwater contamination by dissolved organic compounds frequently occurs in valley aquifers that consist of highly heterogeneous sand and gravel sediments. Remediation and risk assessment (e.g. reactive transport modeling) requires detailed information on the sorption/desorption kinetics in such aquifer materials. In this paper we present data on slow sorption kinetics of phenanthrene and the composition of several aquifer materials that are typical for southern Germany and Switzerland. The heterogeneity of the aquifer material is described in terms of the physical and chemical properties (e.g., grain size, organic carbon content, intraparticle porosity, sorption parameters, and rate constants for intraparticle diffusion) of the sediment constituents (lithocomponents). Phenanthrene sorptive uptake in a heterogeneous bulk sample can be predicted using a numerical model only if the composition and geochemical heterogeneity (different sorptivities and porosities of the lithocomponents) are considered. It could be shown that even within a narrow grain size fraction, the geochemical heterogeneity has to be incorporated for the prediction of long‐term sorptive uptake or release of organic contaminants.
    Keywords: Heterogeneity ; Sorption Kinetic ; Numerical Modeling ; Aquifer Material
    ISSN: 0730-7268
    E-ISSN: 1552-8618
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