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.
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).
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.
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 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.
Forecasted change in precipitation may lead to an increase of biomass in area covered by savannah and to a consequent increase in biomass burning, affecting the carbon emissions at global scale. Understanding how tropical ecosystems will react to those changes is relevant particularly for East Africa, where population density is the highest of the continent. We generated high-resolution sediment charcoal data spanning the last 2000 years across a climatic gradient (wet to dry savannah) to assess the long-term impact of fire, climate and land use on tropical savannah ecosystems. Records of biomass burnings show contrasting fire pattern among the two regions. In wet savannah ecosystems, fire was limited by wetter periods until the colonial period (AD 1800), when biomass removal led to a decrease in burning. In contrast, in the dry setting of Kenya, fire conditions during the last 2k years peaked at intermediate rainfall, and increased in recent times following land use intensification. On the basis of our data we hypothesize that under a future scenario with increased rainfall fire will increase in the wet savannah and decrease in the (eastern) dry savannah, unless fuel will be limited by agriculture practices. Yet, it is not understood how important vegetation properties and ecosystem services such as plant biomass and diversity will respond to inter-annual to seasonal variation in the moisture balance, and how tropical species will cope with extreme events, such as droughts. The following proposal addresses highly relevant questions for todays key issues of biodiversity and the adaptation of vulnerable communities to global change. Additionally, it will contribute to ongoing multi-proxy research concerning the magnitude, frequency, and rates of past climate change in equatorial East Africa. Finally, the project will improve our understanding of tropical ecosystem functioning and its interaction with cultural and economic systems at local to regional scales.
The proposed research contributes to the following overarching goals: (i) better understanding of the complex hydro-biogeochemical and biological interactions in tropical montane forest systems under natural and altered conditions; (ii) the integration of this knowledge in an integrated modeling system that will be tested to long-term and spatially dense datasets; and (iii) prognosis of the likely impact of climate change scenarios on the hydro-biogeochemical and biological processes considering for each process the uncertainty range on the prediction. A main deliverable of the project will be the expanded CMF modeling tool enabling the simulation of the combined impact of land use and climate change on hydro-biogeochemical processes and biological interaction. The project follows the general philosophy of cooperative researchers between experimentalists and modelers, thereby facilitating the implementation of state-of-the-art system understanding into simulation tools. The integrated modelframework developed in D4 will therefore allow to assess the likely impacts of global change on tropical montane rainforest ecosystems of Ecuador.
Temperatures in Switzerland increased about 0.57 C over the last three decades and climate models predict that this increase will continue during the 21st century and beyond. Accompanied by changes in the water supply due to the expected increase in the frequency and intensity of heavy precipitation and/or drought events, these effects will strongly force changes in forest productivity, spatial distribution of tree species, and changes in the species composition within forests. Projections of the future dimensions and interactions of these effects require detailed understanding of short and long-term changes in eco-physiological responses to past and present climate variation. Stable isotopes in tree rings have become a significant tool in obtaining retrospective insight into the plant physiological response to climate and other environmental variables. The increasing number of isotope records, however, also highlights important unsolved questions and current limitations of this tree-ring parameter. Obviously, an improved understanding of the mechanisms leading to variations in the tree's internal carbon and water cycle in relation to climate, soil moisture conditions, transpiration and expansion of the root system is urgently needed. ISOPATH aims to decipher the origin and variability of the isotopic signal in the tree rings of two alpine species, frequently used in climate reconstructions, and to understand the environmental and physiological information encoded. We will develop weekly resolved records of carbon and oxygen isotopes in xylem and needle water, needle sugars, phloem sugars and stem wood/cellulose of two physiologically differing species (larch and spruce) growing under varying temperature, soil moisture and relative humidity conditions. Those data will be related to a large suite of external variables including precipitation and soil water, temperature, and vapour pressure deficit. We act (i) on a spatial scale by following the complete pathway of stable isotopes from the atmosphere into the tree ring under varying environmental conditions and (ii) on a temporal scale by studying seasonal cycles of the isotope signals in all these different components, covering four growth seasons (2008-2011). This unique dataset in terms of length, resolution and number of measured variables will be used to test and improve advanced models for isotope fractionation at the leaf level and in the tree ring, in relation to species-specific traits, temperature and soil moisture conditions. The measured and modelled isotope signatures will allow to predict plant physiological adaptation in the alpine environment to climate change of the 21st century.
The goal of this study was to enable a prognosis on the future rainfall conditions of the Nile Equatorial Lakes regions by delivering time-series of monthly rainfall sums for the time-period from 2021 to 2050 that can be used for all kinds of applications. One example might be the dimensioning of hydraulic structures. In these very long lasting investments, future climatic conditions have to be considered during present planning and construction.The principal sources of information on future climate conditions are General Circulation Models (GCMs). These are physically based atmospheric models that resemble a numerical weather prediction system but on a much coarser scale. This forecast cannot be perfect. Especially, it cannot predict single values, e. g. if January 2050 will be rather wet or dry, but only climatic references, i.e. state, if Januaries in general will become wetter or dryer in the future. Even if the predictions of a GCM were perfect, its output could not be used directly for hydrological purposes, due to its coarse resolution. The monthly precipitation values that are provided by the GCM present the spatially averaged precipitation over a grid cell of several thousand square kilometres. This 'block rainfall' can differ significantly from rainfall measured at the ground. Rain gauges are influenced by local effects like micro climatic conditions or orographic effects of mountain ranges that GCMs are not able to resolve.This study combined the information from different data sources. As global trend information, monthly precipitation values from two GCMs (ECHAM5 and HadCM3) were used. Three CO2-emission scenarios (A1b, A2 and B1) were considered in this data. As local ground reference observed monthly rainfall sums from several rain gauges in East Africa as well as from three reanalysis projects (Climate Research Unit, University of Delaware and GPCC) were used.At each rain gauge or observation point in the reanalysis a technique called 'Quantile-Quantile-Transformation' was applied to establish a relationship between the Cumulative Distribution Function (CDF) of the GCMs and that of the ground references during the calibration period from 1961-1990. The CDFs were fitted by non-parametric Kernel-Smoothing. To account for potential shifts in the annual cycles of GCMs and ground references, the transformations was done separately for each month.Assuming that the relation between Global Model and local response will be constant in the future, the global predictions of the GCM can be downscaled to local scale, leading to future rainfall scenarios that are coherent with observed past rainfall.Combining the data from three CO2-emission scenarios of two GCM with three reanalysis data sets, an ensemble of 18 different rainfall time-series was created for each observation point. The range of this ensemble helps to estimate the possible uncertainties in the prognosis of future monthly precipitation sums from 2021 to 2050.
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).
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