Das Projekt "Immobilisation of arsenic in paddy soil by iron(II)-oxidizing bacteria" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Universität Tübingen, Institut für Geowissenschaften, Zentrum für Angewandte Geowissenschaften.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.
Das Projekt "Indonesian Throughflow variability on sub-orbital timescales during Marine Isotopes Stages (MIS) 2 and 3" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Universität Kiel, Institut für Geowissenschaften, Abteilung Angewandte Geophysik.This project will provide quantitative estimates of the flow of low-salinity warm water through the Indonesian Gateway on suborbital timescales during MIS 2 and 3 (focusing on Dansgaard Oeschger (D-O) oscillations) and will assess the Indonesian Throughflow (ITF) s impact on the hydrography of the eastern Indian Ocean and global thermohaline circulation during this critical interval of high climate variability. ITF fluctuations, associated with sea level change, temperature and salinity variations in the West Pacific Warm Pool (WPWP) strongly influence precipitation over Australia, the strength of the southeast-Asian summer monsoon, and the intensity of warm meridional currents in the Indian Ocean. We will test the hypothesis that increased ITF is associated with warm interstadials of MIS 3, whereas a strong reduction in ITF occurred during stadials. We will use as main proxies planktonic and benthic foraminiferal isotopes in conjunction with Mg/Ca temperature estimates and radiogenic isotopes (mainly Nd) as tracers of Pacific water masses along depth transects in the Timor Passage and the eastern Indian Ocean. This project will provide the paleoceanographic framework that will be crucial to validate and refine circulation models of D-O events and high-frequency climate variability on a global scale.
Das Projekt "Forschergruppe (FOR) 861: Cross-scale Monitoring: Biodiversity and Ecosystem Functions, Quantification of functional hydro-biogeochemical indicators in Ecuadorian ecosystems and their reaction on global change" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Universität Gießen, Institut für Landschaftsökologie und Ressourcenmanagement, Professur für Landschafts-, Wasser- und Stoffhaushalt.Water is an intrinsic component of ecosystems acting as a key agent of lateral transport for particulate and dissolved nutrients, forcing energy transfers, triggering erosion, and driving biodiversity patterns. Given the drastic impact of land use and climate change on any of these components and the vulnerability of Ecuadorian ecosystems with regard to this global change, indicators are required that not merely describe the structural condition of ecosystems, but rather capture the functional relations and processes. This project aims at investigating a set of such functional indicators from the fields of hydrology and biogeochemistry. In particular we will investigate (1) flow regime and timing, (2) nutrient cycling and flux rates, and (3) sediment fluxes as likely indicators. For assessing flow regime and timing we will concentrate on studying stable water isotopes to estimate mean transit time distributions that are likely to be impacted by changes in rainfall patterns and land use. Hysteresis loops of nitrate concentrations and calculated flux rates will be used as functional indicators for nutrient fluxes, most likely to be altered by changes in temperature as well as by land use and management. Finally, sediment fluxes will be measured to indicate surface runoff contribution to total discharge, mainly influenced by intensity of rainfall as well as land use. Monitoring of (1) will be based on intensive sampling campaigns of stable water isotopes in stream water and precipitation, while for (2) and (3) we plan to install automatic, high temporal-resolution field analytical instruments. Based on the data obtained by this intensive, bust cost effective monitoring, we will develop the functional indicators. This also provides a solid database for process-based model development. Models that are able to simulate these indicators are needed to enable projections into the future and to investigate the resilience of Ecuadorian landscape to global change. For the intended model set up we will couple the Catchment Modeling Framework, the biogeochemical LandscapeDNDC model and semi-empirical models for aquatic diversity. Global change scenarios will then be analyzed to capture the likely reaction of functional indicators. Finally, we will contribute to the written guidelines for developing a comprehensive monitoring program for biodiversity and ecosystem functions. Right from the beginning we will cooperate with four SENESCYT companion projects and three local non-university partners to ensure that the developed monitoring program will be appreciated by locals and stakeholders. Monitoring and modelling will focus on all three research areas in the Páramo (Cajas National Park), the dry forest (Reserva Laipuna) and the tropical montane cloud forest (Reserva Biologica San Francisco).
Das Projekt "The role of intermediate sulfur species (ISS) for isotopic fractionation processes during abiotic and chemolithoautotrophic sulfide oxidation in a natural environment" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft / Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Helmholtz-Zentrum für Umweltforschung GmbH - UFZ, Department Catchment Hydrology.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.
Das Projekt "Antarctic precipitation, snow accumulation processes, and ice-ocean interactions" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Ecole Polytechnique Federale de Lausanne (EPFL), Faculte ENAC, IIE, Laboratoire des sciences cryospheriques (CRYOS).The Antarctic ice sheet and ice shelves cover an area of ca. 14 million km2, over 300 times the area of Switzerland. An additional 19 million km2 of winter sea ice expands the overall southern cryosphere to greater than 6 percent of the Earths surface. With ca. 15 million km2 of that sea ice melting away each summer, the Southern Ocean sea ice cover is one of the largest annual changes on the Earths surface. These large numbers underscore the importance of the Antarctic to global climate processes, and challenge our ability to accurately represent the Antarctic in global climate models. Switzerlands long history of involvement in Antarctic climate and paleoclimate research became grounds for its advancement to full membership in the Scientific Committee on Antarctic Research in 2004. In recognition of growing Swiss interest in the Antarctic, field research described in this proposal will be an international collaborative effort, using logistics and environmental permits issued by Australia, Belgium and Germany. Three distinct lines of research will be pursued with the support requested from SNF and with the assistance of facilities and graduate students provided by the EPFL-ENAC-IIE-CRYOS Laboratory. These research topics will contribute to an increased understanding of oceanic and atmospheric processes influencing the mass balance of the Antarctic sea ice and ice sheet. 1) Field measurements of precipitation, blowing snow, and snow thickness distribution in the Antarctic sea ice zone. International research cruises into Antarctic sea ice fields in consecutive austral winters (September - October 2012 and June - August 2013) will measure blowing snow transport, precipitation, and snow accumulation patterns on sea ice. A PhD student whose dissertation research focuses on snow distribution on sea ice will participate in this work. 2) Numerical modeling of precipitation, blowing snow, and accumulation of snow over sea ice and coastal regions of the Antarctic ice sheet. Precipitation, blowing snow and related measurements obtained during these expeditions will be used in the validation of a high-resolution numerical model of blowing snow transport. That model will in turn be used in larger-scale studies of precipitation enhancement of blowing snow processes, sublimation and riming of atmospheric ice crystals, and the recycling of moisture between the sea ice zone and the Antarctic ice sheet. 3) Time-series oceanographic measurements in a remote area of the east Antarctic coastline, in collaboration with Belgian and EU research programs on ice sheet stability and sea level rise. This study will focus on coastal ocean processes that have been largely overlooked in recent assessments of ice sheet mass balance and the potential contribution of the East Antarctic ice sheet to near-term sea level rise.
Das Projekt "The impact of precipitation intensity and vegetation in the catchment area on autochthonous and allochthonous carbon transfer in stream biofilm food webs" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Justus-Liebig-Universität Gießen, Institut für Tierökologie und Spezielle Zoologie - Tierökologie.In rivers and streams, biofilms are major sites of carbon cycling. They retain large amounts of dissolved organic carbon (DOC) and consequently are most important for the development of aquatic organisms on higher trophic levels. Besides autochthonous primary production, which supports heterotrophic production in biofilms, large amounts of organic carbon (OC) are derived from the surrounding catchment areas. More precipitation and more frequent and severe floods due to climate change will increase the transport of material into streams. Moreover, catchment characteristics including vegetation affect the transport and nature of DOC into aquatic ecosystems. Thus, carbon dynamics depend on how a stream is embedded within and interacts with its surrounding terrestrial environment. Despite its importance for carbon cycling it is not understood to which extent autochthonous or allochthonous carbon is used in biofilms and how increased addition of allochthonous carbon determines the relative use of both carbon sources. The combined application of 13C and 14C analysis on differently labeled DOC sources intend to answer to which extent DOC from different sources is used by bacteria in biofilms and finally transported to higher trophic levels. The use of 13C and 14C signals on carbon compounds and biomarkers is an excellent method to determine carbon sources for microorganisms and the transport of labeled material within the food web.
Das Projekt "Sedimentstabilität und Sedimenttransportvorgänge, Watershed sediment yield modelling for data scarce areas; a case study, Awash River Basin, Ethiopia" wird/wurde gefördert durch: International Postgraduate Studies in Water Technologies (IPSWaT) Scholarship. Es wird/wurde ausgeführt durch: Universität Stuttgart, Institut für Wasserbau.The main goal of the research was to device an alternative solution for watershed sediment yield modelling for data scarce areas where the existing physically based models can not be applicable. Awash River Basin in Ethiopia was selected as case study area. GIS data on soil, land use, precipitation, temperature, stream flow and suspended sediment yield was collected from the Federal Ministry of Water Resources of Ethiopia (FMWRE) and from the National Metrology Service Agency (NMSA) offices. Soil data obtained from FMWRE and Food and Agriculture Organization (FAO) world soil 1974 database was used for derivation of the soil erodibility factor (ERFAC) estimation equation. The ratio of silt to sand and clay content was considered as the governing factor for soil erodibility in developing the ERFAC equation. The SWAT2005 model was selected for calibration and validation of stream flow and sediment yield. A sensitivity analysis was carried out to prioritize model calibration parameters. From the sensitivity analysis, curve number II (CN2), soilwater available to plants (SOL-AWC) and ground water base flow factor (ALPHA-BF) were selected as major stream flow calibration parameters. Similarly CN2, SURLAG (surface lag), slope and sediment routing factor (SPCON) were taken as the major sediment calibration parameters. Parameters related to the soil properties and river channel characteristics were given special attention during the model calibration. Eleven years (1990-2000) stream flow and sediment data were used for model calibration and six years data (2001-2006) were used for model validation. Calibration has been done at three gauging stations located in the Awash River basin. The statistical indicators, Coefficient of determination (R2), Nash-Sutclife efficiency (NSE), Root mean square error observations standard deviation (RSR were applied to evaluate the calibration and validation results. The values of these indicators were used to ratethe performance of the model. Watershed geomorphologic and topographic factors were extracted from the SWAT2005 watershed configuration, using a GIS tool and empirical equations. The relative importance of the factors was determined using Pearsons correlation coefficient based on the sediment yield output obtained from the SWAT2005 model calibration. The results show that, the sediment yield is highly correlated with stream flow, watershed area and watershed slope. Based on the identified parameters and the SWAT2005 model output, an alternative sediment yield estimation equation was derived and checked for its validity.
Das Projekt "Scanning in-situ reflectance spectroscopy as a novel tool for high-resolution climate reconstructions from lake sediments, southern Chile" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: University of Bern, Oeschger Centre + NCCR Climate.Seasonal to annual quantitative reconstructions of spatially-explicit climate state variables for the last 1000 years are recognized as one of the primary targets for current climate research (IGBP-PAGES / WCRP-CLIWAR). The lack of adequate paleoclimate data series is strikingly evident for the southern hemisphere. This proposal will (i) explore systematically the potential of in-situ reflectance spectroscopy as a novel tool for quantitative high-resolution climate reconstructions in a variety of lakes in south-central Chile, and (ii) produce a number of temporally highly resolved temperature and/or precipitation reconstructions for the regional expression of climate variability during the past 1000 years. The project contributes to the international regional multi-proxy climate reconstruction in South America (IGBP-PAGES LOTRED-SA).
Das Projekt "Annual- to decadal-scale quantitative climate reconstructions from varved Alpine lake sediments for the last 3300 years / ENLARGE II" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Universität Bern, Geographisches Institut.Current climate change research is fundamentally challenged by three questions: (i) the characteristics of natural climate variability, (ii) the discrimination of anthropogenic forcing, and (iii) ecological, societal and economic risks when natural variability and anthropogenic forcing are superposed in a future climate. Insight into the regional (here Alpine) expression of climate change and changes of variability is critically important for two reasons: (1) regional trends (e.g. in the Alps), amplitudes and statistics of extremes strongly exceed values reported for the global scale, and (2) latest modelling results (IPCC AR4) suggest that Europe is globally the hotspot for a future increase in the inter-annual variability (e.g., summer temperatures), which will be the greatest challenge. This project will examine varved (annually laminated) lake sediments and provide seasonally to annually resolved quantitative time series for temperature and precipitation for the eastern and north-western Swiss Alps (Engadine, Berner Oberland) back to ca 3300 years. Varved lake sediments are unique paleoclimatic archives and most suitable for very long records since they preserve the low-frequency (>10^2 yrs) climate signal. More specifically, this project will extend the record of interannual quantitative autum SON temperature reconstructions (biogenic silica flux, r=0.70), summer precipitation reconstructions (mica/chlorite ratios, r=0.59) and autum precipitation (mica/plagioclase ratios, r=0.68) in Lake Silvaplana back from 1580 AD to 1300 BC. The applicability of the methods will be tested for Lake Seeberg and Lake Oeschinen in the limestone province and the climate regime of the northwester Swiss Alps. These time series will provide insight into (i) the structure and absolute amplitudes of decadal-century scale climate variability, (ii) quantified multi-decadal climate trends and rates of change, (iii) the hypothesis of greater interannual climate variability during warm periods of the past (e.g. Iron/Roman Age, Medieval ), as it is suggested for Central Europe in the future ('global hotspot of variability'). This project develops in the core theme of IGBP and WCRP PAGES / CLIVAR Intersection. Our data are made available to the NOAA WDC data base for Paleoclimatology.
Das Projekt "The role of bacteria in the formation of iron sulfide minerals under low pH conditions" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Helmholtz-Zentrum für Umweltforschung GmbH - UFZ, Department Seenforschung.Bacteria can trigger mineral formation by their metabolic activity or by provision of sorption and nucleation sites on cell surfaces. Sulfide minerals occur in marine and freshwater sediments primarily as the result of dissimilatory sulfate reduction which is mediated by a phylogenetically diverse group of Prokaryotes that gain their energy by anaerobic respiration with sulfate as terminal electron acceptor. In principle it is the reversal process of pyrite oxidation which generates acidic metal-rich waters causing severe environmental pollution in coal and metal ore mining areas. The formation of iron sulfides is a major process in controlling global element cycling, besides, it is the target process during the treatment of acid mine drainage by the use of dissimilatory sulfate reduction. The sustainability of bioremediation depends on the extent and stability of iron sulfides formed. However, so far little is known about iron sulfide formation under acidic conditions and the role that bacteria play in this process. The objectives of this project are i) to investigate the formation of iron sulfide minerals in sulfate-reducing enrichment cultures under low pH-conditions, ii) to analyse and characterise mineral structures and cell-mineral interactions, iii) to elucidate community structure and its response to varying pH values, and iv) to find out whether the involved bacteria benefit from iron sulfide precipitation. This study may contribute to our general understanding of biomineral formation and sulfate reduction under acidic conditions and may help us to further improve bioremediation strategies.
