Das Forschungsvorhaben PeTroS befasst sich mit den Durchlässigkeitseigenschaften von Steinsalz bei hohen Drücken und Temperaturen. Hinblick auf experimentell und konzeptionell gesicherte Dichtheits- bzw. Integritätskriterien gegenübergestellt. Steinsalz verliert seine Integrität danach unter zwei Bedingungen: Falls durch mechanische Schädigung mit Volumenzuwachs Porosität erzeugt wird (Dilatanzkriterium) oder falls der angreifende Fluiddruck größer ist als die minimale Hauptspannung, so dass Fluide sich Wegsamkeiten entlang der Korngrenzen schaffen können (druckgetriebene Perkolation, Minimalspannungskriterium). Die Kriterien werden durch Versuche in Labor und situ, Beispiele aus dem weltweiten Salz- und Kalibergbau und der Endlagerung sowie natürliche und technische Analoga unterlegt. Es existieren allerdings Druck- und Temperaturbereiche, die zwar potentiell endlagerrelevant sind und in denen gemäß der static pore-scale theory (Lewis, Holness 1996; Ghanbarzadeh et al. 2015) hohe Permeabilitäten vorliegen sollten, die aber bisher nicht experimentell untersucht worden sind. Im Rahmen des vorliegenden Forschungsvorhabens wurde die Durchlässigkeit von Proben aus natürlichem Steinsalz mit Stickstoff und Salzlösung geprüft. Die Versuche umfassten Temperaturen von 140°C bis 180°C und Drücke von 18 MPa bzw. 36 MPa. Die Ergebnisse zeigen, dass eine erhöhte Permeabilität, wie sie aufgrund eines verbundenen Porennetzwerkes zu erwarten wäre, nicht nachzuweisen ist. Hingegen wird die druckgetriebene Perkolation auch im betrachteten Bereich als wesentlicher Mechanismus bestätigt, so dass auch die experimentelle Evidenz für die deformationsgetriebene Perkolation in Frage gestellt ist.
technologyComment of chlor-alkali electrolysis, diaphragm cell (RER): In the diaphragm process, all reactions take place in only one cell. A diaphragm is used to separate the feed brine (anolyte) and the chlorine formed at the anode from the sodium hydroxide containing solution (catholyte) and the hydrogen formed at the cathode. Without the diaphragm being present during electrolysis, chlorine and hydrogen would form an explosive mixture and sodium hydroxide and chlorine would react to form sodium hypochlorite (NaOCl). Diaphragms used to be made from asbestos but up-todate technology allows for asbestos-free polymer-based diaphragms. Purified brine is fed to the anode compartment and percolates through the diaphragm into the cathode compartment. The percolation rate is controlled by a difference in liquid level between both compartments. At the anodes (metal oxide coated titanium), chlorine gas is formed which is collected and directed to further processing. Cathodes, where water decomposition takes place, are made of activated carbon steel. Catholyte leaving the cell, also called cell liquor, is a mixture of 10-12 wt.-% sodium hydroxide and 15-17 wt.-% sodium chloride in water. This solution is usually evaporated to 50 wt.-% NaOH. In this process, simultaneously most of the salt is removed by precipitation to a final residual of 1 wt.-%. The resulting salt is typically recirculated to brine preparation. The advantage of diaphragm cells is that the quality requirements for the brine and the electrical energy consumption are low. Disadvantageous are the high amount of thermal energy necessary for sodium hydroxide concentration and the comparably low quality of the produced sodium hydroxide and chlorine. References: Euro Chlor (2013) An Eco-profile and Environmental Product Declaration of the European Chlor-Alkali Industry, Chlorine (The chlor-alkali process). technologyComment of chlor-alkali electrolysis, membrane cell (RER): In the membrane cell process, the anode and cathode compartments are separated by a perfluoropolymer cation-exchange membrane that selectively transmits sodium ions but suppresses the migration of hydroxyl ions (OH-) from the catholyte into the anolyte. Saturated brine flows through the anode compartment, where chlorine gas is produced at the anode. The electric field in the electrolysis cell causes hydrated sodium ions to migrate through the membrane into the cathode compartment. The cathode compartment is fed with diluted sodium hydroxide solution. Water is electrolysed at the cathode releasing gaseous hydrogen and hydroxyl ions, which combine with the sodium ions and thus increase the concentration of sodium hydroxide in the catholyte. Typically, the outlet concentration of sodium hydroxide is around 32 wt.-%. A part of the product stream is diluted with demineralised water to about 30 wt.-% and used as catholyte inlet. In some units, a more diluted 23 wt.-% NaOH solution is produced. In these cases, the inlet concentration is adjusted to 20-21 wt.-%. Usually the NaOH solution is evaporated to the marketable concentration of 50 wt.-% using steam. Depleted brine leaving the anode compartment is saturated with chlorine and is therefore sent to a dechlorination unit to recover the dissolved chlorine before it is resaturated with salt for recirculation. The advantages of the membrane cell technique are the very high purity of the sodium hydroxide solution produced and the comparably low energy demand. Disadvantages comprise the high requirements on brine purity, the need for sodium hydroxide evaporation to increase concentration, and the comparably high oxygen content in the produced chlorine. In general, multiple cell elements are combined into a single unit, called electrolyser, of whom the design can be either monopolar or bipolar. In a monopolar electrolyser, the anodes and cathodes of the cells are connected electrically in parallel, whereas in the bipolar design, they are connected in series. Therefore, monopolar electrolysers require high current and low voltage, whereas bipolar electrolysers require low current and high voltage. Since bipolar systems allow higher current densities inside the cells, investment and operating costs are usually lower than for monopolar systems. References: Euro Chlor (2013) An Eco-profile and Environmental Product Declaration of the European Chlor-Alkali Industry, Chlorine (The chlor-alkali process). technologyComment of chlor-alkali electrolysis, mercury cell (RER): The mercury cell process comprises an electrolysis cell and a decomposer. Purified and saturated brine (25-28 wt.-% NaCl in water) is fed to the electrolysis cell on top of a film of mercury (Hg) flowing down the inclined base of the cell. The base of the cell is connected to the negative pole of a direct current supply forming the cathode of the cell. Anodes consisting of titanium coated with oxides of ruthenium and titanium are placed in the brine without touching the mercury film. At the anodes, chlorine gas is formed which is collected and directed to further processing. Due to a high overpotential of hydrogen at the mercury electrode, no gaseous hydrogen is formed; instead, sodium is produced and dissolved in the mercury as an amalgam (mercury alloy). The liquid amalgam is removed from the electrolytic cell and fed to a decomposer, where it reacts with demineralised water in the presence of a graphite-based catalyst to form sodium hydroxide solution and hydrogen. The sodium-free mercury is recirculated back into the cell. Cooling of hydrogen is essential to remove any water and mercury. The sodium hydroxide solution is very pure, almost free from chloride contamination and has usually a concentration of 50 %. Further treatment comprises cooling and removal of catalyst and mercury traces by centrifuges or filters. Advantages of the mercury cell process are the high quality of chlorine and the high concentration and purity of sodium hydroxide solution produced. The consumption of electric energy for electrolysis is, however, higher than for the other techniques and a high purity of the feed brine is required. Inherently, the use of mercury gives rise to environmental releases of mercury. References: Euro Chlor (2013) An Eco-profile and Environmental Product Declaration of the European Chlor-Alkali Industry, Chlorine (The chlor-alkali process). technologyComment of potassium hydroxide production (RER): Potassium hydroxide is manufactured by the electrolysis of potassium chloride brine in electrolytical cells. Hydrogen and chlorine are withdrawn from the cell. The rest of the reaction mixture contains KOH, water, and unreacted potassium chloride. This reaction mixture is then concentrated in an evaporator. Most of the potassium chloride crystallizes by evaporation, and is recycled. After evaporation, the potassium hydroxide is precipitated. Potassium hydroxide, chlorine and hydrogen are obtained from potassium chloride brine according to the following reaction: 2 KCl + 2 H2O -> 2 KOH + Cl2 + H2 Reference: Jungbluth, N., Chudacoff, M., Dauriat, A., Dinkel, F., Doka, G., Faist Emmenegger, M., Gnansounou, E., Kljun, N., Schleiss, K., Spielmann, M., Stettler, C., Sutter, J. 2007: Life Cycle Inventories of Bioenergy. ecoinvent report No. 17, Swiss Centre for Life Cycle Inventories, Dübendorf, CH. technologyComment of sodium chloride electrolysis (RER): Sodium chloride electrolysis
technologyComment of chlor-alkali electrolysis, diaphragm cell (RER, RoW): In the diaphragm process, all reactions take place in only one cell. A diaphragm is used to separate the feed brine (anolyte) and the chlorine formed at the anode from the sodium hydroxide containing solution (catholyte) and the hydrogen formed at the cathode. Without the diaphragm being present during electrolysis, chlorine and hydrogen would form an explosive mixture and sodium hydroxide and chlorine would react to form sodium hypochlorite (NaOCl). Diaphragms used to be made from asbestos but up-todate technology allows for asbestos-free polymer-based diaphragms. Purified brine is fed to the anode compartment and percolates through the diaphragm into the cathode compartment. The percolation rate is controlled by a difference in liquid level between both compartments. At the anodes (metal oxide coated titanium), chlorine gas is formed which is collected and directed to further processing. Cathodes, where water decomposition takes place, are made of activated carbon steel. Catholyte leaving the cell, also called cell liquor, is a mixture of 10-12 wt.-% sodium hydroxide and 15-17 wt.-% sodium chloride in water. This solution is usually evaporated to 50 wt.-% NaOH. In this process, simultaneously most of the salt is removed by precipitation to a final residual of 1 wt.-%. The resulting salt is typically recirculated to brine preparation. The advantage of diaphragm cells is that the quality requirements for the brine and the electrical energy consumption are low. Disadvantageous are the high amount of thermal energy necessary for sodium hydroxide concentration and the comparably low quality of the produced sodium hydroxide and chlorine. References: Euro Chlor (2013) An Eco-profile and Environmental Product Declaration of the European Chlor-Alkali Industry, Chlorine (The chlor-alkali process). technologyComment of chlor-alkali electrolysis, membrane cell (CA-QC, RER, RoW): In the membrane cell process, the anode and cathode compartments are separated by a perfluoropolymer cation-exchange membrane that selectively transmits sodium ions but suppresses the migration of hydroxyl ions (OH-) from the catholyte into the anolyte. Saturated brine flows through the anode compartment, where chlorine gas is produced at the anode. The electric field in the electrolysis cell causes hydrated sodium ions to migrate through the membrane into the cathode compartment. The cathode compartment is fed with diluted sodium hydroxide solution. Water is electrolysed at the cathode releasing gaseous hydrogen and hydroxyl ions, which combine with the sodium ions and thus increase the concentration of sodium hydroxide in the catholyte. Typically, the outlet concentration of sodium hydroxide is around 32 wt.-%. A part of the product stream is diluted with demineralised water to about 30 wt.-% and used as catholyte inlet. In some units, a more diluted 23 wt.-% NaOH solution is produced. In these cases, the inlet concentration is adjusted to 20-21 wt.-%. Usually the NaOH solution is evaporated to the marketable concentration of 50 wt.-% using steam. Depleted brine leaving the anode compartment is saturated with chlorine and is therefore sent to a dechlorination unit to recover the dissolved chlorine before it is resaturated with salt for recirculation. The advantages of the membrane cell technique are the very high purity of the sodium hydroxide solution produced and the comparably low energy demand. Disadvantages comprise the high requirements on brine purity, the need for sodium hydroxide evaporation to increase concentration, and the comparably high oxygen content in the produced chlorine. In general, multiple cell elements are combined into a single unit, called electrolyser, of whom the design can be either monopolar or bipolar. In a monopolar electrolyser, the anodes and cathodes of the cells are connected electrically in parallel, whereas in the bipolar design, they are connected in series. Therefore, monopolar electrolysers require high current and low voltage, whereas bipolar electrolysers require low current and high voltage. Since bipolar systems allow higher current densities inside the cells, investment and operating costs are usually lower than for monopolar systems. References: Euro Chlor (2013) An Eco-profile and Environmental Product Declaration of the European Chlor-Alkali Industry, Chlorine (The chlor-alkali process). technologyComment of chlor-alkali electrolysis, mercury cell (RER, RoW): The mercury cell process comprises an electrolysis cell and a decomposer. Purified and saturated brine (25-28 wt.-% NaCl in water) is fed to the electrolysis cell on top of a film of mercury (Hg) flowing down the inclined base of the cell. The base of the cell is connected to the negative pole of a direct current supply forming the cathode of the cell. Anodes consisting of titanium coated with oxides of ruthenium and titanium are placed in the brine without touching the mercury film. At the anodes, chlorine gas is formed which is collected and directed to further processing. Due to a high overpotential of hydrogen at the mercury electrode, no gaseous hydrogen is formed; instead, sodium is produced and dissolved in the mercury as an amalgam (mercury alloy). The liquid amalgam is removed from the electrolytic cell and fed to a decomposer, where it reacts with demineralised water in the presence of a graphite-based catalyst to form sodium hydroxide solution and hydrogen. The sodium-free mercury is recirculated back into the cell. Cooling of hydrogen is essential to remove any water and mercury. The sodium hydroxide solution is very pure, almost free from chloride contamination and has usually a concentration of 50 %. Further treatment comprises cooling and removal of catalyst and mercury traces by centrifuges or filters. Advantages of the mercury cell process are the high quality of chlorine and the high concentration and purity of sodium hydroxide solution produced. The consumption of electric energy for electrolysis is, however, higher than for the other techniques and a high purity of the feed brine is required. Inherently, the use of mercury gives rise to environmental releases of mercury. References: Euro Chlor (2013) An Eco-profile and Environmental Product Declaration of the European Chlor-Alkali Industry, Chlorine (The chlor-alkali process).
Das Projekt "Schutz und Entwicklung des Benninger Rieds" wird vom Umweltbundesamt gefördert und von Bayerisches Staatsministerium für Landesentwicklung und Umweltfragen durchgeführt. The goal is to preserve and improve the core zones as an ecologically valuable calcareous fen, and to create humid meadows in the surroundings by rehumidification. However, the hydrological measures required first need to be examined through a detailed hydrological survey as to their possible impact on the nearby built-up areas; their implementation can only take place, after consultation with the Commission and appropriate authorities, during the second stage of the project. Presumably these measures will entail reduction of the outflow of streams and ditches and the filling of drainage systems. The purchase or lease of about 42 hectares in the core zone and surroundings and intensive information of the residents affected, are a necessary precondition. Furthermore, it is planned to remove non-indigenous trees, in particulars firs, from the core zone. Public relations work to raise awareness among the local community and visitors of the value of this forgotten site, will also be carried out. There is a little corner of forgotten nature, right next to built-up areas, between the towns of Benningen and Memmingen, dubbed the Benninger Ried. It is a 22 hectare calcareous fen and petrifying springs complex with expanses of water where groundwater reaches the surface, containing rare plants such as Armeria purpurea, which occurs nowhere else in the world, and Apium repens. Around the core zone that areas not built up are occupied by extensively and intensively used pastures. Because of changes in the quality and percolation volume of the groundwater, considerable alternations to the vegetation have occured over the past decades. Open springs have become overgrown, natural succession toward bushes is taking hold. Reasons for this are primarily the development of housing estates, which means that the site's core is no longer hydrologically connected to its surroundings, and intensive agricultural use.
Das Projekt "Verbessrung des SPA 'Rieselfelder Muenster'" wird vom Umweltbundesamt gefördert und von Biologische Station Rieselfelder Münster durchgeführt. The idea is to close the currently easily accessible core area to visitors. Simply banishing the inhabitants of Muenster city from one of their favourite recreation spots is however impossible unless this is balanced by a compensatory measure. Therefore, the project will develop an adjoining 150 ha site, which will permit pedestrians, cyclists and birdwatchers to observe the core area and its avifauna from a respectful distance, and simultaneously bring about an expansion of the wetlands available to the birds. As a result, the Rieselfelder SPA will almost double in size and link up to two nearby nature reserves. The site to be developed, currently arable land, is donated by the City of Muenster; LIFE will fund the investment in the works needed to transform it. These include the establishment of a 22 ha lake with nesting islets, several expanses of shallow water whose levels will be allowed to fluctuate and 40 ha of humid meadows and marsh, to be grazed by an Auerochs herd. To round off, visitor infrastructure (paths, observation platforms) which is as unobtrusive as possible, will of course be built. That humans not only destroy natural habitats, but also, perhaps with very different intentions, occasionally create some, is illustrated by the saga of the Rieselfelder Muenster. It begins in 1901, when a chessboard of hectare-sized dyked and drained basins was laid out to receive sewage water from the city of Muenster. As this water flowed through the basins, it was purified by microbial metabolism and percolation through the subsoil. As time passed, waterfowl and waders discovered the eutrophic waters of this biological treatment system and, given the lack of alternatives in this intensively farmed region, it became an important inland staging area for migrating birds. However, in 1975 a mechanical treatment plant was opened and the Rieselfelder were henceforth irrigated with the clean water emitted by this plant. The 233 ha site was designated SPA, but simultaneously became a tourist attraction and favorite spot for walks. That is its paradox: before 1975 the site was left to the birds on account of its overpowering stench of sewage, but now, thanks to the wastewater treatment plant which eliminated the smells, visitors (up to a thousand a day) have become a serious source of disturbance for the nesting and resting birds. Urgent action is required.
Das Projekt "Teilprojekt 7" wird vom Umweltbundesamt gefördert und von VISTA Geowissenschaftliche Fernerkundung GmbH durchgeführt. Im Rahmen der Projektes ViWA (siehe dazu die ViWA- Gesamtvorhabensbeschreibung) bestehen die Ziele des Vorhabens des Projektpartners VISTA in der Entwicklung und der Nutzung eines globalen, hochaufgelösten, fernerkundungsgestützten Monitoringsystems für Wasserflüsse, landwirtschaftlicher Erträge und Wassernutzungseffizienz. Daten der seit neuestem verfügbaren Satelliten des Copernicus Programms der EU, die sowohl mit optischen (Sentinel-2) als auch mit Mikrowellen-Sensoren (Sentinel-1) ausgestattet sind, werden dazu prozessiert, ausgewertet und in das Wasserhaushalts- und Pflanzenwachstumsmodell PROMET assimiliert. Hierzu werden umfangreiche Ensemble-Simulationen der landwirtschaftlichen Produktion einer breiten Palette von Kulturpflanzen, sowie die Wasserflüsse Verdunstung, laterale Abflüsse, Perkolation und Gerinneabfluss für landwirtschaftliche und natürliche Flächen mit PROMET (Mauser (2009, 2015) genutzt. Um die Flut an Satellitendaten, die durch eine sehr hohe räumliche Auflösung (10-20 m) und zeitliche Wiederholung (alle 2-5 Tage) gekennzeichnet sind, zu bewältigen, wird ein automatisiertes Verfahren unter Nutzung eines modellgestützten Ansatzes entwickelt und validiert. AP2 'Globales Monitoring und Simulation der Wasserflüsse, Erträge und Wassernutzungseffizienzen' ist die zentrale Aufgabe für Vista im ViWA Projekt. Dabei steuert Vista die Copernicus Komponente bei. Nach der globalen Simulation von Wasserflüssen, Ertrag und Wassernutzungseffizienz (AP2.1) wird der der Abgleich mit Beobachtungen und Validierung (AP2.4) im Fokus stehen. Eine Untersuchung der Möglichkeiten der Erdbeobachtung zum Monitoring von signifikanten Veränderungen der Nachhaltigkeit der landwirtschaftlichen Aktivität unter Nutzung von Testgebieten, die von TP4.2 als hot-spots identifiziert wurden wird durchgeführt (AP4.1). Der Stakeholderprozess (AP1) wird während des gesamten Projektzeitraums unterstützt.
Das Projekt "Land Use and Water Resources Management under Changing Environmental" wird vom Umweltbundesamt gefördert und von Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V., Institut für Landschaftswasserhaushalt durchgeführt. Intensive agricultural production in the Hai River catchment had detrimental impacts on the quantity and quality of ground and surface water. High cropping intensity, irrigation and fertilizer applications of more than 300 kg N/ha resulted in a decrease of the ground water table by more than 30 m within the last decades and severe deterioration of water quality in the Piedmont Plain Region, a part of the Hai River catchment. The shortage of water resources in the Hai River basin not only hinders the development of the local economy, but also results in severe environmental problems such as:- subsidence of the ground surface due to over-exploitation of groundwater, - degradation of ecosystems, - shrinking of rivers and lakes, - non point source pollution of soil and ground water - serious water pollution in the main channels and tributaries. Sustainable land use in that region requires a sound knowledge of the effects of single management measures. However, subsoil heterogeneity is one of the major obstacles, impeding relating cause and effect at larger scales and to assess the effect of single management strategies. In this study, a three-step up-scaling approach is suggested that combines some innovative methodologies, and enables to grasp the heterogeneities usually encountered at the management scale. First, a recently developed robust methodology will be applied to determine deep percolation and groundwater recharge in situ without requiring a fully-fledged soil hydrological model. The results can be compared to seepage data from lysimeters of the Luancheng station. Moreover, spatial heterogeneities and temporal patterns can be determined and can be related to soil hydrological properties. Second, spatial functional hydrological heterogeneity can be assessed based on principal component analysis of time series of soil water content and groundwater recharge, allowing to up-scale detailed measurements from single field sites. Third, processes affecting groundwater quality, and exchange between groundwater and surface water can be investigated using non-linear PCA of soil water, groundwater, and stream water quality data, combined with stable isotope data. The outcome of the project is expected to provide valuable contributions to scale-specific simulation of water and solute fluxes at the management scale.
Das Projekt "Si-Aufnahme durch Pflanzen und Transformation von phytogenem Si" wird vom Umweltbundesamt gefördert und von Universität Bayreuth, Fachgruppe Geowissenschaften, Bayreuther Zentrum für Ökologie und Umweltforschung (BayCEER), Lehrstuhl für Agrarökosystemforschung durchgeführt. Das phytogene amorphe Si ist einer der aktivsten Si-Pools in terrestrischen Biogeosystemen. Seine Lösung beeinflusst den Si-Austrag aus Böden, die Wiederaufnahme von Si durch Pflanzen und somit entscheidend den Si-Kreislauf. Die Aufnahme von Si aus verschiedenen Si-Pools des Bodens durch 4 typische Laub- und Nadelbäume, sowie 2 Gräser wird quantifiziert und die Bildung des phytogenen Si wird in Gefäßversuchen bestimmt. In Inkubationsexperimenten wird die Kinetik der Auflösung von phytogenem Si unter verschiedenen pH- und Redoxbedingungen des Bodens, aber auch bei Anwesenheit der komplexbildenden Karbonsäuren quantifiziert. In einem Perkolationsversuch wird die Verlagerung im Boden und Auswaschung von phytogenem Si aus dem Boden bestimmt. Alle Experimente , T1/2=172 a) durchgeführt, wodurch eine?werden mit radioaktivem 32Si (schwaches Differenzierung der pflanzlichen Aufnahme von Si aus verschiedenen Bodenpools ermöglicht wird, zwischen der Auflösung von phytogenem und geogenem Si unterschieden wird und sehr hohe Nachweisgrenzen erreicht werden. Die morphologischen Formen des phytogenen Si und ihre Veränderungen während der Lösung werden durch eine Kopplung von Mikroautoradiographie und Mikroskopie identifiziert. Quantifizierte kinetische Parameter der biogenen Si-Flusse werden wesentliche Beiträge zur internen Si-Kreisläufen in Ökosystemen liefern
Das Projekt "Mikrobielle 'in situ'-Sanierung mittels Frac-Verfahren" wird vom Umweltbundesamt gefördert und von Osthannoversche Eisenbahnen durchgeführt. Objective: The project is to clean up the soil of the Nettelbeck railway station that is contaminated by hydrocarbons due to approximately 30 years of trans-shipment activities. Soil excavation not being possible without seriously disturbing normal operation at the station, OHE decided to wash the soil using the FRAK technology for breaking up the bound soil structures. The soil is then percolated in situ with water enriched with nutrients and oxygen in order to create optimum conditions for microbial activity; the groundwater whose level is closely below the surface is extracted and hydrocarbons are skimmed off by an external skim reactor. General Information: After two years of operation, German authorities accepted the FRAK-assisted microbial clean-up of the railway trans-shipment site of OSTHANNOVERSCHE EISENBAHNEN AG (OHE) at Nettelbeck near Hamburg which had been contaminated with mineral oil as satisfactory. This demonstration of the efficiency of the FRAK installation was granted assistance by the European Commission, within its ACE 89 programme on demonstration projects on clean technologies and contaminated site monitoring and rehabilitation. The project demonstrated the successful clean-up of soil contaminated by mineral oil at an average concentration of 3.500 mg hydrocarbons per kg. The goal was to clean up the soil to concentration values below 1000 mg/kg and groundwater to concentrations of less than 0,1 mg/l, the national tolerability limits being 0,4 mg/l. It was shown that this in-situ clean-up had no adverse effects on the neighbouring groundwater environment. The process was to extract polluted groundwater, remove oil beyond the dilution limits of approximately 5 mg/l, load the cleaned-up water with oxygen and nutrients and percolate the soil with the recycled water. Within this cycle, microbes feeding on mineral oil digested the remaining hydrocarbons. It could be shown that the initial nutrient reservoir was used up during digestion, which made the addition of phosphate and nitrate necessary in later phases of the cycle. To achieve clean-up to the goals set, the percolating water - ca. 75 times the average rainfall quantity - had to be recycled for approximately 160 times. The rate of hydrocarbon removal was remarkable: within eight weeks on the average, approximately 90 per cent of the contaminants could be removed. The digestion and percolation processes were greatly enhanced by air-pressure-assisted tear-up of the soil structure using a FRAK installation that had been constructed by DETLEF HEGEMANN ENGINEERING GmbH with Commission assistance within the ACE 89 programme; water percolation was drastically enhanced by a factor of five, which made the microbial in-situ treatment of soils with low penetrability (kF) value below 10-4 feasible...
Das Projekt "Die Bedeutung des Bodenskeletts als Speicher für kurzfristig verfügbare Nährelemente" wird vom Umweltbundesamt gefördert und von Universität Freiburg, Institut für Geo- und Umweltnaturwissenschaften, Professur für Bodenökologie durchgeführt. For soil chemical analyses, the soil skeleton is normally rejected because this size fraction is considered to have no significant short-term nutritional potential. In order to revise this practice, the short-term potential for ion storage and ion mobilization of the isolated and cleaned soil skeleton was investigated by model experiments, using undisturbed and homogenized soil samples as references. The cleaned skeleton was embedded in an inert quartz-silt-matrix ('fine earth substituted soil systems'). The study considered different soil profiles on granite, gneiss and sandstone bedrock from Black Forest, Germany. The method allowed for the investigation of soil columns at a water status near field capacity. After the extraction of water soluble ions with deionized water, cation exchange properties were determined by percolation of the soil cores with ammonium chloride (NH4Cl). The results revealed site-specific ion mobilization potentials of the soil skeleton. Below the A-horizon, the skeleton fraction of the gneiss site plays the dominant role as a source for short-term base cation supply. The fine earth of the corresponding soil horizon had lost this function, since the base saturation was less than 5 %. More than 80 % of the exchangeable Ca and Mg in naturally layered soil cores originate from the skeleton. The skeleton of the granite site had much lower ion mobilization rates, but nevertheless, due to the high skeletal contents in soil the importance for ion mobilization must not be neglected. The soil skeleton of the sandstone site showed cation exchange capacities which were comparable to the gneiss site, but its ecological importance is less because of the low skeleton content in soil.
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