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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 41 (2003), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: A field tracer test performed under natural flow conditions at the Twin Lake test site, Chalk River Laboratories of the Atomic Energy of Canada Ltd. in Chalk River, Ontario, Canada, using tritium and three herbicides (Chlor-toluron, Terbuthylazine, and Pendimethalin) was interpreted using the dispersion equation with a combined reaction model. The reaction model couples an instantaneous equilibrium reaction governed by a linear adsorption isotherm with a reversible or irreversible kinetic reaction of the first order, and decay. An improved interpretation method consists of a simultaneous fitting of theoretical concentration and mass-recovery curves to the experimental data, which leads to a more reliable determining of reaction models and improves the accuracy of fitting. Tritium served as the reference tracer to determine the flow velocity, dispersivity, and the recovery of the herbicides. Chlortoluron was slightly delayed by equilibrium exchange with strongly reduced concentration due to an irreversible kinetic reaction and/or decay. Terbuthilazine was slightly delayed by equilibrium exchange, with strongly reduced concentration due to a reversible kinetic reaction with some influence of decay. A strong equilibrium reaction and a strong reversible kinetic reaction without degradation governed the transport of Pendimethalin, reducing considerably its concentration. The results obtained show that simulations based only on Kd and decay constant, especially if these parameters are found in the laboratory, may considerably differ from those performed with reaction parameters determined in properly performed field tests. The dominant reaction types, and the values of parameters found in the study, supply useful information on the transport of the investigated herbicides in sandy aquifers under natural flow conditions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 5 (1983), S. 49-52 
    ISSN: 1432-0495
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The underground transport of pathogenic bacteria and viruses may be described by the general transport equation considering dispersion, adsorption, and biological elimination. The survival time of bacteria and viruses in groundwater is different for the specific species and for the specific groundwater environment. Dispersion causes a distribution of pollutants in time and space, thus their concentration decreases over time and with transport distance. Microorganisms are reversibly adsorbed on underground particles, which causes a retardation of their transport velocity with respect to groundwater flow velocity. An additional approach is provided by the filter theory.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    GeoJournal 7 (1983), S. 435-443 
    ISSN: 1572-9893
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract The concentration and migration of contaminants in ground-water is influenced by many geochemical, physical, and biological processes. The mobility of inorganic and organic contaminants in ground-water is controlled by their solubility. The dissolution and precipitation behaviour of many substances can be predicted with help of geochemical models on basis of chemical thermodynamics. The adsorption of contaminants on the surface of solid particles and the desorption of other components into solution cause a retardation of contaminant transport with respect to surrounding ground-water. The empirical distribution coefficient as characteristic measure for this process is specific for the given contaminant and the geochemical environment. Convection and hydrodynamic dispersion control the transport and the mixing processes of contaminated ground-water with natural ground-water. The concentration of the contaminants decreases in time and with transport distance whereas the volume of the contaminated plume increases. The specific properperties of immiscible organic fluids, e.g. mineral oil products and chlorinated hydrocarbons, result in lower or higher flow velocities than that of water and in the tendency to form separate impregnation bodies on the water table or at the base of the aquifer. Gas transport is important for the removal of volatile contaminants and decay products. The transport of suspended particles is controlled by filtration processes. Organic compounds are decomposed by autochthonic microorganisms that obtain from these processes carbon and hydrogen for their cell synthesis and energy for their metabolism. The main effect of microbial activity is an acceleration of geochemical processes. The propagation of pathogenic bacteria and viruses in ground-water is controlled by the same general mechanisms as that of the other contaminants. However, the active attachment and mobility of bacteria may improve the effectivity of the specific processes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 77 (1990), S. 551-553 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Innerhalb eines interdisziplinären Forschungsvorhabens wurden ausgewählte Umweltchemikalien (Simazin, Lindan, Trichlorethen, Tetrachlorethen) in ein 100 m langes künstliches Grundwassergerinne eingespeist, welches mit verdünntem Sickerwasser einer aerob betriebenen Deponie beschickt wird. Durch eine Vielzahl von Probenahmestellen ist es möglich, eine Vorstellung von der dreidimensionalen Verteilung der Substanzen im Gerinne zu erhalten. Außerdem lassen sich Schlüsse hinsichtlich Eliminations- und Rückhalteprozessen machen. Über die Probleme der Probenahme und Analytik der ausgewählten Stoffe wird berichtet. Es zeigte sich, daß die Entnahme- und Meßverfahren wegen der schwierigen Feldbedingungen bzw. der komplexen Zusammensetzung der Matrix zunächst gewisser Anpassungen bedurften.
    Notes: Summary Selected chemical substances (simazine, lindane, tri-, tetrachloroethene) were fed into an artificial aquifer (100 m) operated with diluted seepage water from an aerobic landfill. Numerous sampling points made it possible to obtain more information about a three-dimensional distribution of the substances within the aquifer. Elimination and retention can be observed as well. Problems of sampling and analytical procedures are discussed. It was obvious that the methods of sampling and determination required certain adaptions because of the difficult local conditions and the complex matrix composition, respectively. The work was carried out within the scope of an interdisciplinary research programme.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 66 (1977), S. 826-838 
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract In a general survey the groundwater supply of the Federal Republic of Germany is a quantity defined by rock permeability and groundwater recharge. Taking into account bank filtered river water and artificial groundwater recharge the future demand of high quality groundwater will be available. Difficulties arise from areal distances between centres of demand and of supply, from the necessity to explore groundwater in hard rocks which have been rarely used up to this time due to its difficult exploration, from the quantitative and qualitative groundwater protection and from competition of groundwater use with the exploitation of other natural resources. Geoscientists are challenged to contribute to the solution of these problems in interdisciplinary cooperation together with engineers, water chemists and other water experts by using their special knowledges and scientific techniques.
    Abstract: Résumé D'après une estimation globale, la disponibilité en eau souterraine de la République Fédérale Allemande représente une quantité limité par la perméabilité des roches et par la réalimentation en eau de la nappe. En tenant compte de l'apport à la nappe aquifère par suite de l'infiltration d'eau de rivière et de son enrichessement artificiel, la demande future en eau souterraine de haute qualité peut être couverte. Les difficultés qui se produiront, vont être provoquées par les distancees entre les points de consommation et les points d'alimentation, par l'exploration difficile des eaux souterraines en roches fissurées, et karstifiées, par la protection quantitative et qualitative des eaux souterraines et par la compétition entre l'usage des eaux souterraines et l'exploitation des autres ressources naturelles. Les chercheurs sont appelés, pour resoudre ces problèmes dans un cadre interdisciplinaire, à collaborer avec les ingénieurs, les chimistes et autres éxperts en eaux, chacun avec leurs connaissances spéciales et leurs méthodes de travail.
    Notes: Zusammenfassung Bei einer pauschalen Betrachtung ist das Grundwasserdargebot der Bundesrepublik Deutschland eine durch die Durchlässigkeit der Gesteine und die Grundwasserneubildung begrenzte Größe. In Verbindung mit Uferfiltratgewinnung und künstlicher Grundwasseranreicherung kann auch der künftige Bedarf an qualitativ hochwertigem Grundwasser gedeckt werden. Schwierigkeiten ergeben sich jedoch aus dem Auseinanderfallen von Bedarfs- und Gewinnungsschwerpunkten, aus der Notwendigkeit, bisher wenig genutzte, schwierig zu erschließende Grundwasservorkommen in Festgesteinen zu erschließen, aus dem qualitativen und quantitativen Grundwasserschutz und aus der Konkurrenzsituation der Grundwassernutzung mit der Nutzung anderer Rohstoffe. Die Geowissenschaftler sind aufgerufen, zur Lösung dieser Probleme in interdisziplinärer Zusammenarbeit mit den Ingenieuren, Wasserchemikern und anderen Wasserfachleuten durch ihre speziellen Kenntnisse und Arbeitsmethoden beizutragen.
    Type of Medium: Electronic Resource
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