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.
Degradation of the soil productivity due to salt accumulation (salinization) is a major concern in arid, semi-arid and coastal regions. Soil salinization is an old issue but encouraged irrigation practices have been rapidly increasing its intensity and magnitude in the past few decades. Studies have shown that excess of the irrigated water contributes significantly to evaporation from the bare soil surface and therefore to the salinization. In some parts of the world soil salinity has grown so acute that the agricultural lands have been abandoned. Evaporation salinization is mainly influenced by interaction between the flow and transport processes in the atmosphere and the porous-medium. On the atmosphere side, wind velocity, air temperature and radiation have a strong impact on evaporation. Furthermore, turbulence causes air mixing, influences the vapor transport and creates a boundary layer at the soil-atmosphere interface which indeed influences evaporation. On the porous-medium side, dissolved salt is transported under the influence of viscous forces, capillary forces, gravitational forces and advective and diffusive fluxes. The water either directly evaporates from the water-filled pores or it is transported to air due to diffusive processes. Continuous evaporation promotes salt accumulation and precipitation resulting in soil salinization. In the scope of this work we attempt to develop a model concept capable of handling flow, transport and precipitation processes related to evaporative salinization of an unsaturated porous-medium.
Warm conveyor belts (WCBs) are coherent airstreams that typically develop along cold fronts associated with extratropical cyclones. These airstreams originate in the moist subtropical marine boundary layer and ascend within 1-2 days to the upper troposphere whilst moving more than 2000 km towards the pole. They occur most frequently during winter in the western North Pacific and North Atlantic where they are responsible for the major part of precipitation. The key role of WCBs for the dynamics of the synoptic and large-scale atmospheric flow stems from their profound impact upon the tropospheric distribution of potential vorticity (PV). The coherent ascent of WCBs leads to the diabatic production of a positive PV anomaly in the lower troposphere and of a negative PV anomaly in upper-level ridges just below the tropopause. When interacting with the extratropical waveguide, these negative PV anomalies can exert a profound impact upon the downstream flow evolution. Hence a WCB can be the trigger for the amplification and breaking of an upper-level Rossby wave, which is particularly relevant in situations where Rossby wave breaking events act as precursors of high-impact weather systems (e.g., heavy precipitation in the western Mediterranean, Saharan dust storms, cold air outbreaks). Recent studies indicate that errors in medium-range numerical weather predictions might be related to the inaccurate representation of WCBs and their effect on upper-level PV. In order to advance the basic understanding of these complex, non-linear and highly important dynamical processes, this project will (i) investigate the parameters and processes that determine the intensity of a WCB, its associated PV evolution and downstream effects, (ii) assess the errors in global models' analyses and forecasts associated with the different stages of a WCB life cycle, (iii) quantify the climatological frequency of the triggering and intensification of upper-level Rossby waves by WCBs, and (iv) provide clear guidance for investigating the dynamics of WCBs within the framework of THORPEX field experiments. In three subprojects, complementary techniques will be applied in order to reach these objectives, including idealized simulations of moist baroclinic waves, real case sensitivity experiments, diagnostic investigations based upon (re-)analysis and forecast data, and a feature-based verification of WCBs in global models using independent observational datasets. In this way this project will contribute to an improved basic understanding of the dynamical effects of WCBs on the downstream evolution of upper-level Rossby waves and (high-impact) surface weather events.
The understanding of long-term, natural climate variability on different spatial and temporal scales is crucial to assess the recent climate change in a global to regional context. Since glaciers are considered as very important climate indicators, the understanding of past and present glacier variations is a key task for evaluating current climate change. Alpine and Scandinavian glaciers do react differently on variations of energy balance, temperature, precipitation and atmospheric circulation. This project investigates the importance of regional/continental temperature and precipitation as driving factors for glacier dynamics (retreats, advances) during the period from the Little Ice Age (LIA) to the early 21st century. Historical information from different archives will allow the reconstructions of glacier length fluctuations and mass balances from (western) Scandinavian glaciers and of a transect from western to the eastern Alps. Further, the sensitivity of Alpine and Scandinavian glaciers to variations of temperature and precipitation, including glacier advances and retreats covering half a millennium, will be studied by means of (non-linear) statistical approaches. A complementary method by reconstruction of mass balances using a continuity approach combined with a GIS-based energy balance model and gridded climate data will also be applied. Finally, the mass balances are extrapolated for the entire Alps and Scandinavia using a distributed energy balance model. This enables a synoptical analysis of European climate related to its significance for glacier fluctuations for the last half millennium. Moreover, the project will shed some light on the future glacier behaviour within the different mountain ranges of Scandinavia and the Alps using existing distributed mass balance and ELA models using different scenarios on the increase of temperature and the change of precipitation. We will also address the question of a changing perception of the glaciers in the Alps and Scandinavia for the last few centuries. The fear of threat by glaciers in early times has changed today to a fear of loss of glaciers as beautiful landscape by the current rapid change of climate. The long-term glacier length record for the Alps and Scandinavia will be stored in the existing database of the Global Terrestrial Network on Glaciers (GTN-G) as part of the World Glacier Monitoring Service (WGMS). A close cooperation between the Universities in Bern/Zurich and Bergen, Norway, will ensure a mutual enrichment of the scientific research. The project is coupled with a joint proposal submitted by the Bjerknes Centre for Climate Research in Bergen. Both projects base on a mutual collaboration of data and knowledge exchange. Finally, to inform the public about the consequences of the current glacier change is crucial, and glaciers are excellent indicators for the public perception of climate change in mountainous areas.
In the South-Indian city of Chennai (formerly called Madras), disastrous tropical monsoon linked with excessive precipitation frequently lead to wide-flat floods in the coastal plains. Caused by rapid urbanisation, the population in urban and periurban areas is more and more affected by these events. Besides the marginalised population living in disfavoured areas, increasingly also the more wealthy population that settles in flood prone areas is affected. Interdisciplinary assessments are needed to explain the complex causes of floods. The project analysed environmental aspects of risk exposure as well as socioeconomic aspects of risk perceptions and response strategies. By combining natural-scientific with socio-scientific approaches, a holistic perspective of the complex reasons and impacts of flooding could be covered. The project consisted of the following steps: 1. Analysis of flood risk exposure: Physio-geographic, hydrological and meteorological realities in risk areas were assessed using remote sensing (RS) data and geographical information systems (GIS). 2. Analysis of risk perception and management: Affected marginalised poor segments of the population, affected middle class groups as well as local planning authorities were interviewed to analyse local perceptions of floods and dominant management strategies. 3. Development of a flood risk map: The results of the risk assessment were integrated in an interactive flood risk map. The map - using several different layers - functions as a flood risk management tool including often neglected socioeconomic and socio-cultural parameters which reflect local vulnerability. 4. Holding of two workshops: A policy workshop with different stakeholders involved in flood management and affected by floods was held in Chennai in August 2007. This workshop was to foster communication and dialogue between different stakeholders and to create awareness on the current situation and problems in the area. A roundtable with the partners from India and organisations dealing with flood management and flood relief measures took place in October 2007 in Freiburg in order to present and discuss the findings and to strengthen future co-operation, communication and networks.
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.
A crucial vulnerability faced by the international community in the near future will be access to fresh water in sufficient quantity and of adequate quality to meet increasing and more diverse needs of a growing world population. Mountains have always held a privileged relationship with water, as the sources of the world's greatest rivers and as the home of the great reserves of water held in glaciers.Major global forces nevertheless threaten these mountain reservoirs. Climate change is predicted to modify quantities of water available as well as shift its seasonality. It is likely that even greater challenges will come from the dynamics of human behavior. Population growth is perhaps the most obvious threat to sufficient water supply but it goes hand in hand with changing norms and evolving activities, leading to increasing competition among use for agriculture, industry, leisure, and domestic activities. Influencing production and distribution are societal rules and norms such as pricing schemes, regulations, and property rights that determine who gets how much water and when. Appropriate solutions to oversee water use will contribute to efficient and equitable distribution. Poor management can aggravate shortages, increase social and economic disparities, and is a potential source of deadly international conflict.Mountain regions are generally considered to be the 'water towers of the world' not only because they receive important quantities of precipitation, but also because this water is then stored there in the form of snow and ice. Populations living in mountains have a very long history of overseeing this precious resource and can be the source of important knowledge about solving the dilemmas of managing a public good that knows no boundaries and can therefore be diverted and traded. Resources governed by natural processes in this way become inextricably linked with political and economic forces. (...)
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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