Arsenic-contaminated ground- and drinking water is a global environmental problem with about 1-2Prozent of the world's population being affected. The upper drinking water limit for arsenic (10 Micro g/l) recommended by the WHO is often exceeded, even in industrial nations in Europe and the USA. Chronic intake of arsenic causes severe health problems like skin diseases (e.g. blackfoot disease) and cancer. In addition to drinking water, seafood and rice are the main reservoirs for arsenic uptake. Arsenic is oftentimes of geogenic origin and in the environment it is mainly bound to iron(III) minerals. Iron(III)-reducing bacteria are able to dissolve these iron minerals and therefore release the arsenic to the environment. In turn, iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II)- oxidation at neutral pH followed by iron(III) mineral precipitation. This process may reduce arsenic concentrations in the environment drastically, lowering the potential risk for humans dramatically.The main goal of this study therefore is to quantify, identify and isolate anaerobic and aerobic Fe(II)-oxidizing microorganisms in arsenic-containing paddy soil. The co-precipitation and thus removal of arsenic by iron mineral producing bacteria will be determined in batch and microcosm experiments. Finally the influence of rhizosphere redox status on microbial Fe oxidation and arsenic uptake into rice plants will be evaluated in microcosm experiments. The long-term goal of this research is to better understand arsenic-co-precipitation and thus arsenic-immobilization by iron(II)-oxidizing bacteria in rice paddy soil. Potentially these results can lead to an improvement of living conditions in affected countries, e.g. in China or Bangladesh.
Groundwater contamination by organic compounds represents a widespread environmental problem. The heterogeneity of geological formations and the complexity of physical and biogeochemical subsurface processes, often hamper a quantitative characterization of contaminated aquifers. Compound specific stable isotope analysis (CSIA) has emerged as a novel approach to investigate contaminant transformation and to relate contaminant sources to downgradient contamination. This method generally assumes that only (bio)chemical transformations are associated with isotope effects. However, recent studies have revealed isotope fractionation of organic contaminants by physical processes, therefore pointing to the need of further research to determine the influence of both transport and reactive processes on the observed overall isotope fractionation. While the effect of gasphase diffusion on isotope ratios has been studied in detail, possible effects of aqueous phase diffusion and dispersion have received little attention so far.The goals of this study are to quantify carbon (13C/12C) and, for chlorinated compounds, chlorine (37Cl/35Cl) isotope fractionation during diffusive/dispersive transport of organic contaminants in groundwater and to determine its consequences for source allocation and assessment of reactive processes using isotopes. The proposed research is based on the combination of high-resolution experimental studies, both at the laboratory (i.e. zero-, one- and two-dimensional systems) and at the field scales, and solute transport modeling. The project combines the expertise in the field of contaminant transport with the expertise on isotope methods in contaminant hydrogeology.
Zearalenon ist ein nichtsteroides Mykotoxin mit östrogener Wirkung, das vorwiegend vom pflanzenpathogenen Pilzen wie Fusarium graminearum (Gibberella zea) und Fusarium culmorum gebildet wird. Infolge der von diesen Pilzen hervorgerufenen Krankeiten von wichtigen Kulturpflanzen, wie z.B. Ährenfusariose von Weizen und Kolbenfäule von Mais, kann es zur Kontamination von Lebensmitteln und Futtermitteln mit gesundheitsrelevanten Mengen des Mykotoxins kommen. Gegenwärtig ist völlig ungeklärt, ob die Fähigkeit zur Produktion von Zearalenon die Fähigkeit des Pilzes beeinflußt, als Pflanzenpathogen zu wirken. Es ist auch unbekannt, ob Zearalenon imstande ist, in bestimmte pflanzenphysiologische Vorgänge einzugreifen und es dadurch dem Pilz erleichtert, die Pflanze zu kolonisieren. Im Rahmen dieser Arbeit soll versucht werden, Voraussetzungen zur Beantwortung dieser Fragen zu schaffen: Durch die Einbringung des Reportergens GFP (Green Fluorescent Protein) in den pflanzenpathogenen Pilz Fusarium culmorum sollte es möglich werden, den Infektionsprozeß zu verfolgen und die Rolle von Zearalenon zu untersuchen. Durch Etablierung der REMI-Methode (Restriction Enzyme Mediated Integration) soll die Grundlage geschaffen werden, Insertionsmutanten von F. culmorum zu identifizieren, die nicht mehr imstande sind das Mykotoxin Zearalenon zu bilden.
Virus inactivation processes at water-solid interfaces are key factors determining the persistence of viruses in various aqueous environments. These include environmental systems such as surface and groundwater, various food products, and blood and other bodily fluids. Once released into a body of water, viruses rapidly associate with water-solid interfaces. Interactions with solid surfaces influence virus disinfection, and thus determine the spread and persistence of infective viruses. Despite the importance of interfacial disinfection processes, their underlying causes remain poorly understood. In this sinergia project, we will identify the most important processes contributing to virus inactivation at interfaces, and we will develop a comprehensive model of the virus characteristics and surface properties that influence inactivation behavior. Our investigations will focus on model systems representative of one of the great challenges to public health, namely water resources contaminated by viral pathogens. To obtain a system characterization at the molecular level, we will use a combined computational and experimental approach. This project is divided into three sub-projects: sub-project A will establish the computational framework that simulates the physical-chemical interactions of virus with the water-solid interface; sub-project B will experimentally evaluate the extent and relative importance of physical and chemical processes that lead to virus inactivation; sub-project C will be dedicated to characterizing the microscale distribution of oxidizing chemical species at the solid-water interfaces. The combination of theory and experiment is well suited to overcome the challenges associated with the complex virus-interface system, and to derive a generally valid concept of virus inactivation at solid-water interfaces.
Due to the tendency to bioaccumulate, trace concentrations of selenium in fresh waters have led to disastrous toxicity effects on water birds and fish in the past. Although this adverse impact was first noticed in the early 1980s, to date no sustainable solution has been found for the remediation of selenium contaminated drainage and waste waters. Compared to water soluble forms, elemental selenium is considered less toxic. Therefore, various remediation approaches try to use microorganisms that are highly efficient in reducing selenium oxyanion concentrations by formation of insoluble elemental selenium. Such biogenic elemental selenium, however, does not crystallize to large particles and remains dispersed in solution as a colloidal suspension, thus being subject to re-oxidation, uptake and assimilation by biota. The probable reason for the tendency of biogenic selenium to remain in solution suspended as nanoparticles is an organic polymer layer modifying the surface, preventing crystallization and conferring the selenium core with physico-chemical properties different from particles without such a layer. To date, it is not known, which molecules (proteins, (poly)saccharides, etc.) form this organic polymer layer. Consequently, it is furthermore unknown, if all microbial groups mediating selenium reduction (either via a respiratory or via co-metabolic reduction) produce the same organic polymer layer around the selenium core. The physico-chemical properties of the layer, however, will strongly influence sedimentation and transport processes of selenium in the environment. Due to the complex chemistry and the nanocrystalline character of the selenium particles, uncertainties persist concerning the selenium solid phase, which is formed biogenically. It is not known, if and to which extent selenium that bears such a polymers layer is subject to further biotic and abiotic oxidation and reduction processes, although these processes will largely govern the ecotoxicological effects of selenium. The present project aims at filling the gaps in understanding biogenic selenium formation by systematically investigating the morphology and speciation of the solid phase and the surface modification mechanisms. By direct (spectroscopic) methods we will determine selenium solid phase speciation and its transformations under environmental conditions. We will develop methods allowing the identification of the organic polymer layers modifying selenium nanoparticles by different microbial groups. Thus we will be able to deliver a mechanistic model describing both layer and core of biogenic selenium nanoparticles and the possible impact(s) they have on each other.
The proposed project is the follow-up project of our present SNF-project CAPAC (Climate And Pol-lution Analysis of Cairo) phase one. Its main purpose is the finishing of the work begun in phase one in terms of methodology and data analysis. CAPAC is conducted by a doctorand, Miss Corinne Frey. CAPAC aims to combine in situ measurements of the energy balance with remote sensing tech-niques to parameterise urban and non-urban heat fluxes of the mega-city Cairo, Egypt and its surroundings. Cairo is located within a green north-south oriented strip of agricultural land and on the other hand between two desserts in the west and east. This makes the location of Cairo unique and very interesting for an urban climate study like this. Scientific objectives are the computation of very high resolution radiation and heat fluxes in urban areas under the conditions of spatial homogeneity/ heterogeneity of urban land cover. Very interesting is the analysis of how urban greens influence the urban heat fluxes and how the new suburbs of Cairo, which are expanding into the dessert explosively, will modify the local climate. The population of Cairo is growing several hundred thousand people per year. During the first phase of CAPAC a field campaign was conducted in Cairo. This data serve as calibration and validation of the remote sensing analysis. Following this campaign, algorithm development and data analysis will be the main task of the following months. This includes the analysis of the in situ measured flux data, as well as the evaluation of the estimated radiation and energy balance terms using ASTER and LANDSAT remotely sensed data. Main tasks in the determination of the radiation and energy balance terms using satellite data will be (1) the completion of the haze-removal-algorithm for the haze contaminated scenes, (2) the completion of the algorithm for estimation of the aerosol optical depth from satellite data and (3) to improve the S-Sebi method for the estimation of the Bowen-ratio or to find a better suited method for the estimation of heat fluxes. Another task, which is primarily related to quality control is the determination of the Bi-directional reflectance function (BRF) over Cairo using satellite data from CHRIS/PROBA, which are already acquired by the European Space Agency (ESA) on our demand. To substantiate the findings from Cairo another area of interest was chosen, namely Beer Sheva, Israel. Beer Sheva is located in the middle of the desert, offering a pure desert climate. There a small follow-up field campaign is planed together with Dr. Oded Potcher from Ben Gurion University in Beer Sheva.
Although the use of genetically modified plants for bioremediation, or the in situ cleaning of contaminated sites, has been known for quite some time, little attention has so far been paid to the production of antibodies in plants and their ex vivo application in selective depletion. Therefore, highly affine and specific antibodies against algal toxins using microcystin as an example will be produced in plants at low cost within this research project. The basis is a monoclonal antibody (Mab 10E7, species: mouse) generated in a former research project. The sequence of the variable domains will be determined, optimized for plants and sub cloned into suitable plant transformation vectors, which already contain constant antibody sequences. In addition, a scFv fragment containing different tag sequences and fusion proteins will be constructed. Leaf-based (tobacco) as well as seed-based (barley) systems will be used.Affinity-purified plant-produced antibodies (plantibodies) will be characterized in detail for their binding properties using microtitre plate-ELISA and surface plasmon resonance (SPR). The monoclonal mouse antibody will be used as reference. To assure cost-efficiency for future applications, roughly purified fractions (sequential pH and temperature treatment followed by filtration) will be tested for the upscaling. Following immobilization of the plantibody fractions on suitable substrates, for instance membranes, porous polymer monoliths or in porous glasses, their application for depletion will be defined using model water samples spiked fortified with microcystins.
Understanding transport of contaminants is fundamental for the management of groundwater re-sources and the implementation of remedial strategies. In particular, mixing processes in saturated porous media play a pivotal role in determining the fate and transport of chemicals released in the subsurface. In fact, many abiotic and biological reactions in contaminated aquifers are limited by the availability of reaction partners. Under steady-state flow and transport conditions, dissolved reactants come into contact only through transverse mixing. In homogeneous porous media, transverse mixing is determined by diffusion and pore-scale dispersion, while in heterogeneous formations these local mixing processes are enhanced. Recent studies investigated the enhancement of transverse mixing due to the presence of heterogeneities in two-dimensional systems. Here, mixing enhancement can solely be attributed to flow focusing within high-permeability inclusions. In the proposed work, we will investigate mixing processes in three dimensions using high-resolution laboratory bench-scale experiments and advanced modeling techniques. The objective of the proposed research is to quantitatively assess how 3-D heterogeneity and anisotropy of hydraulic conductivity affect mixing processes via (i) flow focusing and de-focusing, (ii) increase of the plume surface, (iii) twisting and intertwining of streamlines and (iv) compound-specific diffusive/dispersive properties of the solute species undergoing transport. The results of the experimental and modeling investigation will allow us to identify effective large-scale parameters useful for a correct description of conservative and reactive mixing at field scales allowing to explain discrepancies between field observations, bench-scale experiments and current stochastic theory.
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