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.
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.
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).
Over the past decades, the source of drinking water in Bangladesh has been largely shifted from surface water to groundwater and more and more ground water is being used for the irrigation of paddy rice to meet the increasing food demand. Only in 1998 has it been established that 40-50Prozent of the abstracted groundwater in Bangladesh contains arsenic at concentrations above the WHO drinking water guideline (10 myg/L). 30-50 million people in Bangladesh are estimated to consume drinking water with >50 myg/L As. More than 100'000 cases of As poisoning have been >documented so far. In addition to the immediate threat from the consumption of As-rich drinking water, arsenic input into soils may lead to additional long-term risks for the environment and human health. Arsenic may accumulate in surface soils and eventually decrease the crop yield. Arsenic taken up by rice plants additionally increases the arsenic burden to the local population. Numerous biogeochemical processes affect the cycling of arsenic in the paddy soil - rice plant system. However, the relative importance of these processes and their effect on the fate and impact of arsenic are only poorly understood. In this context, we perform a combined field and laboratory study involving two research teams in Switzerland (EAWAG and ETHZ) and researchers from the Bangladesh University of Engineering and Technology (BUET). One part of the project consists of an extensive field study in the village of Srinagar 30 km south of Dhaka, where we collect extensive data on the fate of arsenic in the irrigation and flood water and its distribution in the paddy fields and the uptake by rice plants. The second part of the project consists of well-controlled laboratory experiments related to the biogeochemistry of arsenic in the studied field system. The aim of these laboratory studies is to gain a detailed understanding of the most relevant biogeochemical processes that control the fate of arsenic at the field scale. The project is the basis for two dissertations. One PhD student working at the EAWAG focuses on transformation processes of arsenic in the irrigation and flood water at the field site and performs laboratory studies on the chemical interactions of arsenic at mineral surfaces. The second PhD student working at the ETH investigates the spatial and temporal variations of the arsenic concentration in the field soils and in paddy rice and performs complementary laboratory experiments on the reduction and oxidation of As in paddy soil and the uptake of As by rice. This project will provide detailed information on the fate of As that is transported into rice fields by irrigation. Detailed investigations of the relevant biogeochemical processes will lead to a better understanding of the key reactions that determine the spatial distribution and the temporal behavior of arsenic in these soils and its uptake by rice.
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.
Global climate change will alter the species composition of forests with far reaching consequences for the biogeochemistry of the water, carbon and nitrogen cycles, the sustainability of economic development and even human health. The annual productivity of wood is substantial for the carbon sequestration and budget of the forests in Eurasia. Whereas a number of publications on the climatic influence on tree radial growth exist, little is known about the precise mechanisms of tree-ring formation, timing and rates of their growth, and about the influence of other exogenous factors such as forest fires, permafrost, or logging on biomass accumulation and carbon sequestration. An improved mechanistic understanding will be particularly important with respect to the prediction of future forest response. In the proposed project, we aim to study the influence of a changing climate on trees by analyzing the main factors controlling tree-ring growth in extreme conditions. We will focus our study on forest ecosystems in regions which are very sensitive to climatic changes and where rapid and dramatic environmental and climatic changes can take place: 1) The high latitude permafrost region in Central Siberia (Russia) 2) The semi-arid dry areas in Central Asia (Uzbekistan) 3) The high altitude temperature-sensitive region of the Swiss Alps (Lötschental, Switzerland). The conifer trees growing in these regions could be seriously damaged due to expected future changes in temperature, CO2 and water availability. The thawing of permafrost and increasing drought situation could be key factors influencing forest growth and possible forest decline. Tree ring samples from the above mentioned regions will be considered to analyze the climatic response according to the following approaches: Intra-seasonal dynamics of tree-ring formation will be recorded and correlated with monitored environmental factors, like air and soil temperature and humidity, permafrost depth and the isotope composition of soil water, precipitation, river and stream water. A broad network of dendrochronological data from different research stations will be developed for each region to cover various local conditions. Special attention will be paid to the carbon/water relations of trees by determination of stable isotope ratios of different ecosystem compartments and tree rings. Project partners are Paul Scherrer Institut, Switzerland (PSI), Swiss Federal Research Institute WSL, Switzerland (WSL), V.N.Sukachev Institute of Forest, Krasnoyarsk, Russia (IF) and Samarkand State University, Uzbekistan (UZ).
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.
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).
Cold-water coral reefs thriving on carbonate mounds have been discovered in the late 90-s off western Ireland and recently off Morocco. Mound building seems to be a fundamental but still enigmatic strategy of Life, developed since Precambrian times onwards. Various arguments suggest that microorganisms are playing a major role in reef development and biodiversity. Mounds may find their origin at the confluence of fluxes from external (oceanic) and internal origin (geofluids). Long cores taken in 2004 showed that the 'Pen Duick- mounds off Morocco, in which microbial action was demonstrated by an strong emission of hydrogen sulfide, may be considered as giant biogeochemical reactors. MiCROSYSTEMS proposes to turn the Pen Duick mounds into a natural laboratory through the following actions and experiments:- Biotope exploration and characterization of biodiversity through geophysical and video imaging, targeted microbiological profiling, evaluation of present and past oceanic conditions,- Microbial diversity census and evaluation of the functional link microbes-metazoans through metazoan species analysis, biogeochemical and molecular fingerprinting, laboratory culturing, fauna-microbe interactions analysis, evaluation of microbially mediated processes of carbonate precipitation,- Assessment of the impact of biodiversity changes through the development of a reactor technology to simulate and assess the functionality of the micro-ecological niches and the impact of environmental changes.The MiCROSYSTEMS project closely dovetails with European projects on deep-water coral ecosystem conservation and with IODP Expedition 307. The project will foster a Europe-Maghreb cooperation on the Moroccan margin and contribute to the ICoMM initiative within the Census of Marine Life Programme.
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.
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