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  • Sorption
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  • 1
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    Universität Tübingen: 16 Geowissenschaftliche Fakultät. Bereich 16 Geowissenschaftliche Fakultät (ohne Institutszuordnung)
    Language: German
    Description: Subsurface contaminations with hydrophobic organic contaminants such as polycyclic aromatic hydrocarbons (PAH) or chlorinated solvents are frequently found in shallow Aquifer systems like the River Neckar valley in SW-Germany. Possible risks that arise for the groundwater quality or the choice of remediation techniques depend on the transport behavior of the contaminants. The transport velocity is mainly determined by sorptive interactions between the dissolved pollutants and the heterogeneous aquifer material. Objective of this work was to investigate sorption and sorption kinetics of phenanthrene and trichloroethylene in different lithocomponents of the heterogeneous River Neckar valley sediments and of fresh rocks of the respective source areas. In addition to petrography methods mainly laboratory batch experiments were performed. Sorption was nonlinear for all samples investigated. In the River Neckar aquifer sediments sorption was governed by triassic and jurassic carbonates. Distribution coefficients are mainly a function of organic carbon content and organic carbon quality. An estimation of sorption capacity based on the organic carbon content and coal petrography methods is possible but gets more difficult due the heterogeneity of the organic matter. Sorption kinetics is diffusion limited and can be modeled using a numerical solution of Fick’s 2nd law. Due to their high sorption capacities and low intraparticle porosities the jurassic and especially the triassic carbonates showed very slow sorption kinetics. Faster sorption kinetics was observed for the sandstones due to their low sorption capacities and high intraparticle porosities. In most cases sorption kinetics was governed by intraparticle pore diffusion and predictions of effective diffusion coefficients were possible based on the intraparticle porosity and Archie’s Law. For small grains or highly porous sandstones containing coarse particulate organic matter (POM) diffusion into the organic matter (intrasorbent pore diffusion) is the limiting process in sorptive uptake. Particle sizes of up to 50 µm were observed for POM, furthermore mature organic matter may contain significant amounts of microporosity (pores 〈 2 nm). For highly porous sandstones containing a low porosity matrix (e.g. as cementation), the diffusion into this matrix may be the limiting process in sorptive uptake. Weathering and transport of the components had no significant impact on sorption and sorption kinetics. Sorption and desorption seems to be reversible at least for the components investigated in this work. Predictions of sorption/desorption kinetics in the heterogeneous River Neckar aquifer sediments is possible based on physical properties and sorption capacities of the different lithocomponents using the numerical modeling for a multi-component system. Based on the results of this work the reactive transport under non equilibrium conditions in the River Neckar aquifer sediments can be modeled.
    Description: Eine Vielzahl der heute bekannten Untergrundverunreinigungen in SW-Deutschland befindet sich in den Lockersedimenten der Talaquifere. Diese sind durch die bevorzugte Nutzung der Flusstäler für urbane und industrielle Ansiedlungen in besonderem Maße einem Eintrag von Schadstoffen ausgesetzt. Zur Beurteilung möglicher Sanierungsmethoden oder zur Gefahrenbeurteilung z.B. für das Grundwasser kommt einer möglichst genauen Kenntnis der Transportvorgänge hier eine große Bedeutung zu. Der Transport gelöster organischer Schadstoffe im Grundwasser unterliegt in großem Ausmaß den Wechselwirkungen mit den verschiedenen Bestandteilen des heterogenen Aquifermaterials. Ziel dieser Arbeit war es, die Sorption und Sorptionskinetik hydrophober organischer Verbindungen (PHE und TCE) innerhalb der petrographisch unterschiedlichen Komponenten (Lithokomponenten) der heterogenen Aquifersedimente des Neckartals und von Festgesteinen aus deren Liefergebiet zu untersuchen. Neben verschiedenen sedimentpetrographischen Methoden kamen dabei vor allem Laborversuche zur Gleichgewichtssorption und zur Sorptionskinetik zum Einsatz. Die Sorption im Gleichgewicht lässt sich für alle untersuchten Komponenten mittels dem nichtlinearen Freundlich-Sorptionsmodell beschreiben. Innerhalb der Aquifersedimente des Neckartals wird die Sorption eindeutig durch die Muschelkalke und Jurakalke dominiert, wobei die Verteilungskoeffizienten v.a. eine Funktion des Gehalts an organisch gebundenem Kohlenstoff und darüber hinaus des Inkohlungsgrades (Reife) des organischen Materials sind. Eine Abschätzung der Verteilungskoeffizienten aus dem Gehalt an organischem Kohlenstoff ist unter Verwendung kohlenpetrographischer Methoden möglich. Die Sorptionskinetik der untersuchten Lithokomponenten und Festgesteinsfragmente ist diffusionslimitiert und läßt sich sehr gut durch eine numerische Lösung des 2. Fick’schen Gesetzes beschreiben. Die Jurakalke und v.a. die Muschelkalke zeigten aufgrund hoher Verteilungskoeffizienten und niedriger Intrapartikelporositäten eine sehr langsame Kinetik. Eine schnellere Kinetik aufgrund niedrigerer Verteilungskoeffizienten und hoher Porositäten zeigten die Sandsteine. I.d.R. folgte die Sorptionskinetik dem Modell der Intrapartikelporendiffusion, womit eine Abschätzung effektiver Diffusionskoeffizienten aus der Intrapartikelporosität nach Archie’s Law möglich ist. Für sehr kleine Korngrößen oder hochporöse Sandsteine, die grobes organisches Material enthalten, ist die Diffusion in das partikuläre organische Material (POM) der die Kinetik limitierende Prozess. Für das POM, das innerhalb des Korngefüges der Sedimentgesteine lokalisiert ist, wurden Partikelgrößen von bis zu 50 µm beobachtet. Gereiftes organisches Material verfügt darüber hinaus über deutliche Anteile an Mikroporosität (Poren 〈 2 nm). Für hochporöse Sandsteine, die über eine gering poröse Matrix verfügen (z.B. als Zement), kann u.U. die Diffusion in diese Matrix der die Kinetik limitierende Prozess sein. Verwitterung und Transport der Komponenten haben keinen wesentlichen Einfluss auf die Sorptionskinetik. Sorption und Desorption scheinen zumindest für die in dieser Arbeit untersuchten Komponenten reversibel zu sein. Eine Vorhersage der Sorptions-/Desorptionskinetik in den heterogenen Aquifersedimenten des Neckartal auf der Basis der physikalischen Parameter und der Sorptionskapazität der verschiedenen Komponenten ist unter Verwendung des Lithokomponentenansatzes und der numerischen Lösung für die Intrapartikelporendiffusion möglich. Auf der Basis dieser Ergebnisse lässt sich der reaktive Stofftransport im Grundwasser auch unter Ungleichgewichtsbedingungen berechnen.
    Keywords: Sorption ; Organische Schadstoffe ; Diffusion ; Neckartal ; Aquifer Material ; Organic Contaminants ; Schadstofftransport ; Sorptionskinetik ; Aquifermaterial ; Intraparticle Porosity ; Sorption Kinetics ; Intrapartikelporen ; Grundwasserleiter ; Modellierung ; Diffusion ; Earth Sciences
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 2
    Language: English
    In: Science of the Total Environment, 15 August 2014, Vol.490, pp.191-198
    Description: Transport of many pollutants in rivers is coupled to mobilization of suspended particles which typically occurs during floods. Since the amount of total suspended solids ( ) in rivers can be monitored by turbidity measurements this may be used as a proxy for the total concentration of particle associated pollutants such as PAHs, PCBs, etc. and several heavy metals. Online turbidity measurements (e.g. by optical backscattering sensors) would then also allow for an assessment of particle and pollutant flux dynamics if once calibrated against and total pollutant concentrations for a given catchment. In this study, distinct flood and thus turbidity events were sampled at high temporal resolution in three contrasting sub-catchments of the River Neckar in Southwest Germany (Ammer, Goldersbach, Steinlach) as well as in the River Neckar itself and investigated for the total amount of PAHs and in water; turbidity (NTU) and grain size distributions of suspended solids were determined as well. Laboratory experiments were performed with natural river bed sediments from different locations (Ammer) to investigate PAH concentrations, and turbidity during sedimentation of suspended particles under controlled conditions (yielding smaller and smaller suspended particles and with time). Laboratory and field results agreed very well and showed that turbidity and were linearly correlated over an extended turbidity range up to 2000 NTU for the field samples and up to 8000 NTU in lab experiments. This also holds for total PAH concentrations which can be reasonably well predicted based on turbidity measurements and vs. PAHs relationships — even for high turbidity values observed during flood events (〉 2000 NTU). Total PAH concentrations on suspended solids were independent of grain size of suspended particles. This implies that for the rivers investigated the sorption capacity of particles did not change significantly during the observed events.
    Keywords: Pollutant Fluxes in Rivers ; Turbidity ; Total Suspended Solids ; Particle Facilitated Transport ; Polycyclic Aromatic Hydrocarbons ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Environmental Science & Technology, 05/1999, Vol.33(10), pp.1645-1651
    Description: Most aquifer materials are heterogeneous in terms of grain size distribution and petrography. To understand sorption kinetics, homogeneous subfractions, either separated from heterogeneous sands and gravels (lithocomponents) or fragments of fresh rocks, have to be studied. In this paper we present data on long-term sorption kinetics of phenanthrene for homogeneous samples consisting of one type of lithocomponents or fresh rock fragments in different grain sizes. Diffusion rate constants were determined in batch experiments using a numerical model for retarded intraparticle pore diffusion and correlated to grain size and intraparticle porosity of the lithocomponents. Sorption isotherms were nonlinear for all samples investigated (Kleineidam et al. (1)). The numerical model described the sorption kinetics very well for coarse sand and gravels. Tortuosity factors, which were obtained as final fitting factors, agreed with Archie's law predictions based on the intraparticle porosity. The dependency of sorptive uptake on grain size revealed that for smaller grains intrasorbent diffusion may become significant. This is attributed to relatively large particulate organic matter (POM) within the sedimentary rock fragments. Specifically, charcoal and coal particles, which were found in some of the sandstones, controlled the sorptive uptake rates.
    Keywords: Geochemistry Of Rocks, Soils, And Sediments ; Environmental Geology ; Aquifers ; Aromatic Hydrocarbons ; Charcoal ; Clastic Rocks ; Clastic Sediments ; Coal ; Coarse-Grained Materials ; Diffusion ; Experimental Studies ; Fragments ; Geochemistry ; Grain Size ; Gravel ; Ground Water ; Homogeneous Materials ; Hydrocarbons ; Kinetics ; Laboratory Studies ; Numerical Models ; Organic Compounds ; Particulate Materials ; Phenanthrene ; Physicochemical Properties ; Pollution ; Polycyclic Aromatic Hydrocarbons ; Sand ; Sandstone ; Sedimentary Rocks ; Sediments ; Sorption;
    ISSN: 0013-936X
    E-ISSN: 1520-5851
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  • 4
    Language: English
    In: Environmental Science & Technology, 05/1999, Vol.33(10), pp.1637-1644
    Description: Remediation of groundwater contamination in unconsolidated aquifers by dissolved hydrophobic compounds (HOC) requires detailed information on the sorption parameters present in the sediments. Equilibrium sorption isotherms were measured for phenanthrene for a wide variety of lithocomponents (constituents of sand and gravel sediments) and unweathered rock fragments (limestones and sandstones). The lithocomponents were separated based on macroscopic appearance of different lithologies (e.g. limestones, sandstones, shales, mudstones, and igneous rocks) and characterized in terms of organic carbon content and specific surface area. In addition the organic matter (OM) was characterized using coal petrography methods (white and UV light microscopy). As confirmed by heat-treated samples sorption was solely due to OM. Organic carbon normalized sorption coefficients (K sub(OC)) varied by almost 3 orders of magnitude among the samples investigated. The different origin and maturity of isolated organic matter (organic facies) is believed to be responsible. For example, extremely high K sub(OC) values were found for particulate organic matter such as charcoal and coal particles which were preserved within the sandstone and limestone grains. In a second paper we report data on sorption kinetics of the samples used in this study (1).
    Keywords: Chemical Equilibrium ; Sediment Pollution ; Particulate Organic Matter ; Pollutant Persistence ; Adsorption ; Groundwater Pollution ; Aquifers ; Sediment Pollution ; Sorption ; Limestone ; Organic Matter ; Remediation ; Groundwater Pollution ; Geology ; Aquifers ; Sorption ; Rocks ; Water Pollution Treatment ; Organic Matter ; Remediation ; Groundwater Pollution ; Isotherms ; Phenanthrene ; Hydrophobic Compounds ; Physics and Chemistry ; Characteristics, Behavior and Fate ; Sources and Fate of Pollution ; Freshwater Pollution ; Hydrophobic Compounds ; Phenanthrene;
    ISSN: 0013-936X
    E-ISSN: 1520-5851
    Source: American Chemical Society (via CrossRef)
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  • 5
    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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  • 6
    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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  • 7
    Language: English
    In: Sedimentary Geology, 1999, Vol.129(3), pp.311-325
    Description: Quaternary fluvial valley deposits form major groundwater reservoirs for the drinking water supply, which are at the same time favorable urban and industrialized areas where contamination of the aquifers and their sediments occurs frequently. The transport behavior of dissolved hydrophobic organic contaminants (HOC) depends on the sorptive interactions (sorption isotherms, sorption kinetics) with the sediment grains and therefore on the sediment history in terms of source rocks (lithocomponents), petrographic composition, and depositional processes (lithofacies, e.g. grain-size distribution). The geological formations present in the source rock area already determine the variability of lithocomponents and thus the sorption capacities for organic contaminants in the valley (aquifer) sediments since they show distinct differences in organic carbon content (C (sub org) ) and nature of organic matter (both influence the sorption behavior of hydrophobic organic compounds). In general, lithocomponents originating from sedimentary rock have higher C (sub org) contents and thus higher sorption capacities compared to metamorphic and magmatic components, and the quartz and feldspar minerals. The petrographic composition of the samples is grain-size-dependent but very similar within a specific lithofacies. Higher fractions of sedimentary rock fragments occur in the gravel-dominated lithofacies, which therefore have higher sorption capacities. In contrast to this, the sand grain-size fractions (sand facies) are, due to decay and transport processes (sediment maturity), enriched in stable lithocomponents such as quartz minerals which consequently lead to lower sorption capacities for HOC. Attention has to be drawn to the impact of strongly sorbing constituents such as Tertiary coal fragments (local source rock area) present in some of the sand samples.
    Keywords: Petrography ; Fluvial Sediments ; Organic Matter ; Equilibrium Sorption ; Geology
    ISSN: 0037-0738
    E-ISSN: 1879-0968
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