The relevance of biogeochemical gradients for turnover of organic matter and contaminants is yet poorly understood. This study aims at the identification and quantification of the interaction of different redox processes along gradients. The interaction of iron-, and sulfate reduction and methanogenesis will be studied in controlled batch and column experiments. Factors constraining the accessibility and the energy yield from the use of these electron acceptors will be evaluated, such as passivation of iron oxides, re-oxidation of hydrogen sulfide on iron oxides. The impact of these constraints on the competitiveness of the particular process will then be described. Special focus will be put on the evolution of methanogenic conditions in systems formerly characterized by iron and sulfate reducing condition. As methanogenic conditions mostly evolve from micro-niches, methods to study the existence, evolution and stability of such micro-niches will be established. To this end, a combination of Gibbs free energy calculations, isotope fractionation and tracer measurements, and mass balances of metabolic intermediates (small pool sizes) and end products (large pool sizes) will be used. Measurements of these parameters on different scales using microelectrodes (mm scale), micro sampling devices for solutes and gases (cm scale) and mass flow balancing (column/reactor scale) will be compared to characterize unit volumes for organic matter degradation pathways and electron flow. Of particular interest will be the impact of redox active humic substances on the competitiveness of involved terminal electron accepting processes, either acting as electron shuttles or directly providing electron accepting capacity. This will be studied using fluorescence spectroscopy and parallel factor analysis (PARAFAC) of the gained spectra. We expect that the results will provide a basis for improving reactive transport models of anaerobic processes in aquifers and sediments.
Chromium (Cr) is introduced into the environment by several anthropogenic activities. A striking ex-ample is the area around Kanpur in the Indian state of Uttar Pradesh, where large amounts of Cr-containing wastes have been recently illegally deposited. Hexavalent Cr, a highly toxic and mobile contaminant, is present in significant amounts in these wastes, severely affecting the quality of sur-roundings soils, sediments, and ground waters. The first major goal of this study is to clarify the solid phase speciation of Cr in these wastes and to examine its leaching behavior. X-ray diffraction and synchrotron-based X-ray absorption spectroscopy techniques will be employed for quantitative solid phase speciation of Cr. Its leaching behavior will be studied in column experiments performed at un-saturated moisture conditions with flow interruptions simulating monsoon rain events. Combined with geochemical modeling, the results will allow the evaluation of the leaching potential and release kinetics of Cr from the waste materials. The second major goal is to investigate the spatial distribution, speciation, and solubility of Cr in the rooting zone of chromate-contaminated soils surrounding the landfills, and to study the suitability of biochar as novel soil amendment for mitigating the deleterious effects of chromate pollution. Detailed field samplings and laboratory soil incubation studies will be carried out with two agricultural soils and biochar from the Kanpur region.
In this project we experimentally explore the transport of engineered inorganic nanoparticles (EINP) through soils. This is done for original EINPs and some pre-aged form. Transport of NPs in soil is expected to be different from that of reactive solutes, in that hydrodynamic drag, inertial and shear forces as well as the affinity to water-gas interfaces are expected to be more relevant. Hence, the mobility of EINPs in soil is highly sensitive to the morphology of the porous structure and the dynamics of water saturation.This project provides the pore network structure for natural soils using X-ray micro-tomography to allow for an up-scaling of pore-scale interactions explored by project partners to the scale of soil horizons. The pore structure is represented by a network model suitable for pore scale simulations including the dynamics of water-gas interfaces.Pore network simulations will be compared to column experiments for conservative tracers as well as for unaltered and pre-aged EINPs (obtained from INTERFACE). This includes steady state flow scenarios for saturated (ponding) and unsaturated conditions as well as for transient flow to explore the impact of moving water-gas interfaces. The final goal is to arrive at a consistent interpretation of experimental findings and numerical simulations to develop a module for modelling EINP transfer through soil as a function of particle properties, soil structural characteristics and external forcing in terms of flux boundary conditions.
Sulfur isotope fractionation (34S/32S) has been used since the late 1940s to study the chemical and biological sulfur cycle. While large isotope fractionations during bacterial sulfate reduction were used successfully to interpret, e.g., accumulation of sulfate in ancient oceans or the evolution of early life, much less is known about fractionation during sulfide oxidation. The fractionation between the two end-members sulfide and sulfate is commonly much smaller and inconsistencies exist whether substrate or product are enriched. These inconsistencies are explained by a lack of knowledge on oxidation pathways and rates as well as intermediate sulfur species, such as elemental sulfur, polysulfides, thiosulfate, sulfite, or metalloid-sulfide complexes (e.g. thioarsenates), potentially acting as 34S sinks.In the proposed project, we will develop a method for sulfur species-selective isotope analysis based on separation by preparative chromatography. Separation of Sn2- and S0 will be achieved after derivatization with methyl triflate on a C18 column, separation of the other sulfur species in an alkaline eluent on an AS16 column. Sulfur in the collected fractions will be extracted directly with activated copper chips (Sn2-, S0), or precipitated as ZnS (S2-) or BaSO4 and analyzed by routine methods as SO2. Results of this species-selective approach will be compared to those from previous techniques of end-member pool determinations and sequential precipitations.The method will be applied to sulfide oxidation profiles at neutral to alkaline hot springs at Yellowstone National Park, USA, where we detected intermediate sulfur species as important species. Determining 34S/32S only in sulfide and sulfate, our previous study has shown different fractionation patterns for two hot spring drainages with sulfide oxidation profiles that seemed similar from a geochemical perspective. The reasons for the different isotopic trends are unclear. In the present project, we will differentiate species-selective abiotic versus biotic fractionation using on-site incubation experiments with the chemolithotrophic sulfur-oxidizing bacteria Thermocrinis ruber as model organism. For selected samples, we will test whether 33S and 36S further elucidate species-selective sulfide oxidation patterns. We expect that lower source sulfide concentrations increase elemental sulfur disproportionation, thus increase redox cycling and isotope fractionation. We also expect that the larger the concentration of intermediate sulfur species, including thioarsenates, the larger the isotope fractionation. Following fractionation in species-selective pools, we will be able to clarify previously reported inconsistencies of 34S enrichment in substrate or product, elucidate sulfide oxidation pathways and rates, and reveal details about sulfur metabolism. Our new methodology and field-based data will be a basis for more consistent studies on sulfide oxidation in the future.
The aim of the project is to investigate the role of physical forcing, resource availability, and organismic interactions for the spatial and temporal distribution patterns of plankton in lakes. The research is focused on the distribution patterns of the buoyant cyano bacterium Planklothrix rubescens in Lake Ammer and compares the abundance of P. rubescens with the temporal and spatial variability of abiotic conditions and of phyto- and zooplankton. The main hypotheses are that (1) transport by internal wave motions has a substantial influence on the horizontal distribution patterns of P. rubescens and also affects the distribution of other phyto- and zooplankton; (2) vertical water column motions associated with internal waves cause fluctuations in the vertical layering of P. rubescens and thus alters its competitive abilities; (3) horizontal differences in habitat conditions, i.e. limited vertical water column depth in bays and resource gradients near river inflows, result in longer-term characteristic horizontal distribution patterns of P. rubescens and other plankton; (4) layers of toxic P. rubescens may interfere with the vertical migration of zooplankton. These research questions will be addressed in extensive field experiments measuring horizontal and vertical distribution patterns of plankton and abiotic conditions at temporal scales ranging from minutes to several weeks. In-situ measuring techniques for plankton and abiotic parameters, providing sufficient teniporal and spatial resolution, will be combined with water sample analyses to support them. The distribution of P. rubescens will be measured by using our newly developed in-situ technique that combines information from optic and acoustic instruments. The field experiments will be complemented with 3D and 1D model approaches. The intension of the modeling work is to support the interpretation of the field data by performing numerical experiments that investigate the response of horizontal distribution patterns of P. rubescens to physical forcing, patchy nutrient distribution (e.g. river inflow) or the presence of a shallow bay and by studying the implications of water column depth, internal wave induced fluctuations in light intensity, and grazing for the layering of p. rubescens in a vertical water column.
Two related SNF-projects are the Swiss contribution to the Lake Van Drilling Project being carried out by the International Continental Scientific Drilling Program (ICDP). This Lake Van Drilling project (PALEOVAN) the key to trigger the newly established SNF-supported Swiss membership in ICDP. One proposal covers the Swiss share of the drilling operations to recover several hundred meters of sediments. The other proposal addresses the scientific activities of the involved Swiss research groups. Lake Van (eastern Anatolia, Turkey), the fourth largest terminal lake on Earth, is surrounded by lively volcanoes within a tectonically active area. Lake Van's annually-laminated sediments are expected to be excellent paleoclimate and paleoenvironment archive because they contain a long and continuous continental sequence that covers several glacial-interglacial cycles (ca.500 kyr). Therefore, ICDP identified Lake Van is a key site to investigate climatic, environmental, volcanic and tectonic evolution during the last few hundred thousands years of the Near East in the cradle of human civilization. This Swiss initiative embedded in the overarching ICDP Drilling project on Lake Van consist of five complementary research modules: Module A: Sedimentology and stratigraphic framework and implications for lake level changes and paleoseismology. Module B: Geochemical analyses of solid phase (climate proxies) and fluid phase. Module C: Organic geochemistry, biomarkers, 14C dating of single compounds. Module D: 10Be as a tracer of solar and geomagnetic variability and erosion rate. 10Be as well as 14C and 36Cl provide a unique tool to reconstruct the history of solar variability and changes in the geomagnetic field intensity. The large laminated sediment body of Lake Van allows to study the evolution of long-lived radio nuclides at high temporal resolution on much longer time scales than those being assessable by ice-cores. Module E: Noble gases as proxy for vertical fluid transport in the sediment column and lake level fluctuation.
The simulation models developed in the 1st phase integrate the chemical fate of the veterinary medicines sulfadiazine (SDZ) and difloxacin (DIF) in bulk soil and their subsequent effects on soil microorganisms and on soil functions after single-dose application with manure. In the 2nd project phase, this approach is extended to the rhizosphere, which represents the hotspot of microbial growth in soil and a continuous source of organic compounds released from active roots. The processes of fast and slow sorption, transformation and formation of bound residues of the antibiotics and their main metabolites are adapted to the rhizosphere. The developed effect models for soil functions, structural diversity, and resistance dynamics are extended by relevant plant-soil interactions in close collaboration with the experimental subprojects. The integrated fate-effect model is coupled with a transport model taking heterogeneities of the rhizosphere and plant uptake into account. Processes are parameterized for the two antibiotics SDZ and DIF in rhizosphere and bulk soil with data from the central mesocosm experiment and several planned satellite experiments. The resulting integrated fate-effect models will be evaluated with data from the field experiments. The model is further used to develop indicators such as structural resilience and functional redundancy for antibiotic induced effects, evaluate their applicability for risk assessment and to generate new hypotheses to corroborate the conclusions.
The project Non-Linear Threshold for amplification analyses for moderate earthquakes in alpine valleys (NLT) aims to enhance the use of non-linear soil models in amplification analyses. Due to the complexity of the non-linear soil models, especially when incorporated in 2 or 3 dimensional dynamic calculations, the knowledge of threshold conditions need to be studied in detail to reduce computational efforts. The so-called non-linear soil behaviour is governed by the change of stiffness of soils under loading, deformation and in case of high water table levels by an increase in porewater pressure, which can reach values equivalent to the effective stress (liquefaction). Whereas studies exists on the threshold for stress and strain to consider nonlinearity in dry conditions (e.g. Vucetic, 1994), no such value exists for the interaction between earthquake loading causing porewater pressure build-up and subsequently softening of the material and a change of the stress state. The increase in porewater pressure depends on the incoming stresses and strains as well as the length of an earthquake. As long as particle reorientation is involved, porewater pressures increase already under low loading states, even though liquefaction might only be reached after significant numbers of load cycles. The influence of pore pressure increase, change in directivity and elongated earthquakes, as shown by Faeh et al. 2006 due to topographical effects, will be studied with a series of cyclic laboratory experiments using advanced triaxial and a hollow cylinder apparatus. These tests will be accompanied by field experiments, which have been partially funded with matching funds from the Competence Centre for Environment and Sustainability (CCES) in the project COGEAR . This study is absolutely essential for countries like Switzerland, where big earthquakes are rare whereas moderate earthquakes occur quite frequently and valley effects amplify and lengthen an earthquake in time. To be able to study the amplification further, different material models developed to describe non-linear soil behaviour in the last decades need to be judged to which extent the non-linearity caused by an increase of pore pressures can be covered with these models. While the judgment will be based on one-dimensional calculations and on the existing codes, the most promising model(s) will be transferred into a hybrid calculation building on the developments from the Swiss Seismological Survey (SED). The area of non-linearity can be separated from the linear equivalent calculations. For specific valley conditions (Visp, VS), a model is in preparation to incorporate topographical effects into the study. The Valais, and specifically the area of Visp, has been selected for its high seismic hazard and their well reported non-linear effects observed after the 1855 event. In the past, the Valais has experienced a magnitude 6 or larger event every 100 years, the last in 1946, and the region of (...).
Aerobic granular sludge-based systems have been recently proposed as a promising innovative alternative for wastewater treatment. Aerobic granular sludge may be developed in bubble column-type reactors operated in a sequencing batch mode with anaerobic and aerobic phases. The advantages are relatively low operating and maintenance costs and a high density biomass sludge blanket which results in a compact and efficient treatment system. For a successful operation of this promising treatment system, formation of physically and metabolically stable granular sludge is a prerequisite. A detailed understanding of the granule formation, the bacterial populations involved, and the physical structure is still missing and therefore we investigate three main objectives: (i) the competition and relative importance of PAO and GAO in granular sludge structure, (ii) granule formation and stability for optimized nitrogen and phosphorus removal, and (iii) the microbial assembly and community in relation to granular structure. A combination of process engineering approaches with the molecular characterization of the microbial communities of the granules is applied. The results of the first two project years showed that with propionate as substrate a more stable biological phosphorous removal by PAO could be achieved than with acetate. Microbial community characterization showed that it was indeed dominated by PAO in the propionate reactor whereas GAO were predominant when phosphorous removal was low in the acetate reactor. A new methodology to measure PAO activity in real time inside the reactor based on conductivity measurement was developed and will now be applied to study the competition between PAO and GAO in aerobic granular sludge. Different aeration strategies for improving nitrogen removal were also successfully tested leading to increased biological nitrogen removal. Furthermore, a detailed characterization of granule structure showed that they are composed of multiple micro-granules containing one population and that they resemble rather a cauliflower than an onion with several layers. This increased understanding of the granular sludge formation, activity and structure will allow tailoring aerobic granules with desired physical and metabolic characteristics which is required for a robust implementation and reliable operation of this novel system for the treatment of different kinds of wastewaters from municipalities or industry.
We propose to develop a computationally efficient way of coupling benthic and pelagic components of biogeochemical ocean and climate models. Neural network-based techniques are to be employed in order to provide the biogeochemical ocean model component with benthic boundary conditions that are consistent with its spatially and temporally varying simulated watercolumn properties. In this novel approach, the neural network associates actual bottom-water properties and sedimentation fluxes simulated by the water column model with consistent local steady-state fluxes of biogeochemical tracers across the sediment surface. This concept does not require long spin-up simulations of the coupled benthic-pelagic models over tens of thousands of years, and instead relies on previous training of the neural net s associative mapping capacity by a large number of long, computationally inexpensive, runs of a one-dimensional benthic model under varying bottom-water and sedimentation-flux conditions.
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