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.
High uncertainties in future climate predictions arise from insufficient knowledge of the interaction of clouds with visible (solar) and infrared (terrestrial) radiation. The optical properties and lifetime of clouds are strongly influenced by the ability of atmospheric aerosol particles to act as cloud condensation nuclei (CCN) or ice nuclei (IN). This so-called indirect aerosol effect has been recognized as one of the greatest source of uncertainty in assessing human impact on climate. Up to now, the climate relevant properties of clouds and their formation processes are still poorly understood, particularly those of mixed-phase clouds where supercooled cloud droplets and ice crystals coexist. Previous research has found that the cloud radiative properties strongly depend on the cloud ice mass fraction, which is influenced by the abundance of IN. Increased IN concentrations are also thought to enhance precipitation, thus causing a decrease in cloud lifetime and cloud cover, resulting in a warming of the atmosphere. Burning questions that we will address are: Which aerosol particles act as IN in our atmosphere ? By which detailed mechanisms do atmospheric aerosols contribute to the formation of ice ? To answer these questions, one major goal of this project is to develop a new inlet for the measurement of cloud droplets and ice crystals. This inlet will also allow the extraction of small ice particles in mixed-phase clouds for the physico-chemical characterization of tropospheric IN. The inlet will represent a novel tool for the in-situ investigation of clouds and will deliver information that is not available by means of any other existing inlet. Measurements will be performed at the Jungfraujoch, one of the world's most prominent high Alpine research stations located at 3580 m altitude in the middle of Switzerland. This unique location offers the possibility to perform these studies in mixed-phase clouds that are representative for the current European background. The proposed research will be performed in a collaborative effort of the Laboratory of Atmospheric Chemistry of the Paul Scherrer Institut (aerosol/cloud research) and the Institute for Meteorology and Climate Research at the Karlsruhe Institute of Technology (cloud microphysics and optics).
Even remote areas such as tropical montane forests suffer from continuously high atmospheric nitrogen (N) and phosphorus (P) deposition. In studies on ecosystem responses to atmospheric nutrient deposition, P cycling has played an underrated role compared to N, although P is thought to limit organism growth in main parts of the Tropics. Furthermore, the responses of tropical montane forests to atmospheric nutrient deposition might depend on the predicted climate change i.e., shifts in temperature and precipitation. Altitudinal gradients represent an ideal means to study environmental changes in tropical montane forests in southern Ecuador, because climate scenarios and unpublished trends in longer-term climate data predict increasing temperatures and decreased moisture which parallels the altitudinal gradient from 4000 m to 1000 m asl.Previous experiments, including the NUMEX experiment in Ecuador, showed that the main proportion of P added to forests to simulate atmospheric deposition was retained in soil. While total P pools in soil respond slowly to low P addition rates, the biological and geochemical processes underlying retention in the organic layer or in soil are expected to react faster. Our overarching objective is to assess the fate of fertilized P in the organic layer and in mineral soil and to elucidate the processes involved in P cycling in soil (immobilization and release rates by microorganisms, sorption/desorption, precipitation/dissolution) along the NUMEX-X altitudinal gradient (1000, 2000, 3000, 4000m; the latter including a Polylepis and a Páramo ecosystem). We will assess P fractions in soil and use a combination of 33P tracer studies and incubation experiments to disentangle biological and geochemical processes controlling P retention. The mechanistic understanding gathered by this proposal is crucial for predictions of ecosystems responses to the continuously high atmospheric N (and P) deposition, because single mechanisms might respond differently (and oppositionally) in the long run. Because the processes involved in P cycling are expected to respond faster to environmental changes than e.g., P pools in soil, these different responses are an essential basis to evaluate effects of environmental change and finally, to develop early-warning ecosystem indicators for environmental change.
Proposed research: This research programme proposes to analyze the predictability of the hydrologic behaviour of Alpine ecosystems at the spatio-temporal scales relevant for water management, i.e. at spatial scales of between 200 km2 (e.g. a hydropower production catchment) and around 5000 km2 (e.g. flood management of the Swiss Rhone catchment) and at temporal scales ranging from hours to seasons. Research context: Quantitative stream flow predictions are essential for the sustainable management of our natural and man-made environment and for the prevention of natural hazards. Despite of ever better insights into the involved physical processes at the point scale, many existing catchment scale runoff prediction models still show a lack of reliability for stream flow prediction. The present research programme addresses this foremost issue in Alpine environments, which are the source of many major European rivers and play a dominant role for hydropower production and flood protection. Stream flow prediction in such environments is particularly challenging due to the high spatial variability of the meteorological driving forces opposed to notorious data scarcity in remote and high elevation areas. Project context: The present proposal is a follow-up proposal of the Ambizione project Hydrologic Prediction in Alpine Environments. During the main phase of the project (3 years), certain essential research objectives could not be reached, due namely to the maternity leave of the principal investigator (PI), but also due to additional research questions that emerged at the very beginning of this research. The present follow-up project proposes to complete the research programme during a complementary project phase (2 years). Objectives: The main objective of this research programme is to assess under which conditions simple hydrological models can give reliable stream flow predictions in Alpine environments. This objective will be reached based on an analysis of the variability of natural flow generation processes and of the variability of corresponding state-of-the-art hydrological model outputs. During the main phase of the project, the research was concentrated on the analysis of flow generation processes related to snowmelt, which in Alpine areas dominate the hydrological response over a large part of the year. The achieved results include a new hourly snowmelt model combined to a spatially-explicit precipitation-runoff model, an improved snowfall-limit prediction method for hydrological models and a weather generator that produces coupled temperature and prediction scenarios to analyze how these two meteorological variables integrate to the snow-hydrological response.(...)
The effects of climate change in mountain regions are expected to be more intense and detectable than in many other regions of the world since climatic conditions vary sharply with elevation. The climatic impacts on fragile ecosystems of Nepal's Himalaya are no exception. It is increasingly being observed that biological systems are disrupted, migrations are starting earlier and species' geographic ranges are shifting. The overall goal of this research collaboration is to identify and analyze threats and opportunities related to climate change. In mountain regions, climate warming is generally considered to be correlated with a change in seasonal precipitation. Both changes will influence the way and intensity of human land use. In our project we therefore propose to study how different levels of land-use intensity (from primeval forests to arable fields) do affect biodiversity. We will investigate replicated land-use gradients at various altitudes in three regions with a different regional climate, and in particular, different levels of seasonal precipitation. Our core study region will be the Manasalu Conservation Area characterized by an oceanic climate and this region will be compared to a hyper-oceanic region in Annapurna Conservation Area and a semi-oceanic region of the Sagarmatha (Everest) region. By using a quasi-experimental landscape approach organisms will be investigated in six valleys covering different precipitation regimes, altitudinal gradients of 1600 m representing different temperatures, and four land use types ranging from closed forests to open landscapes. These organisms will include plants, lichens, mushrooms, butterflies and birds. Population data of Red Listed mammals (Flags
The main goal of the project is to improve the use of carbon and oxygen isotope ratios in tree-rings as a tool to detect the response of Siberian larch forests on permafrost to the recent climate change. The goal will be achieved by a detailed analysis of the incorporation and fractionation of isotopes in a Siberian forest ecosystem (64 N, 100 E) on a seasonal scale, at an approximately weekly time resolution during the vegetation period. A new approach involving compound-specific isotope analysis of different plant components will be applied to enhance the understanding of post-photosynthetic fractionation and carbon allocation processes. These results will be used to calibrate isotope fractionation transfer models along the leaf and stem. Oxygen isotope values of water samples extracted from soil, leaves and branches will be the basis for a better understanding of the water-use of trees, with a focus on time-lags caused by storage and release of permafrost water. Earlywood and latewood isotope chronologies covering the last 100 years on sites contrasting in permafrost depth will enable the application of the results on longer timescales. This will reveal if the thawing of permafrost and the deteriorating summer drought conditions are the key factors influencing forest growth. The results will be compared to studies conducted in the Alpine region in the Lötschental, where tree growth is also temperature-limited, but where the soil conditions (without permafrost) are very different. Siberian larch forests in the continuous permafrost region are sensitive ecosystems and have been especially exposed to the global warming of the recent decades. These forests are vulnerable, as the vegetation period is short, and water and nutrient availabilities are low. Our previous research on Siberian sites indicated a complex interplay of environmental factors, isotope ratios and tree growth. The t and provoke a risk of an additional radiative forcing of the climate system. 2 century were detected. The permafrost in this region has an important role as a direct water source during summer drought due to extremely low precipitation. Increasing temperatures in the future will enhance the leaf-to-air vapour pressure difference, thus the evaporative demand and water loss of the plants, which may reduce productivity and carbon sequestration of these forests. Furthermore, higher decomposition rates in the uppermost part of soils and accessibility of carbon currently stored in permafrost to microbial degradation could release COthemperature signal in the isotope chronologies was lower than expected, but indications for an increasing drought situation in the 20
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 hydrogeochemical dynamics in mountainous areas of the Korean Peninsula are mainly driven by a monsoon-type climate. To examine the interplay between hydrological processes and the mobilization and subsequent transport and export of nitrate and DOC from catchments, a field study was initiated in the Haean catchment in north-eastern South Korea under highly variable hydrologic conditions. In order to identify nitrate and DOC source areas, a subcatchment (blue dragon river) within the Haean basin, which includes different types of landuses (forest, dry land farming, and rice paddies), was selected. In 2009, high frequency surface water samples were collected at several locations during summer storm events. A similar but more comprehensive sampling routine was completed in 2010. In order to investigate the groundwater level fluctuations relative to the hydraulic potentials, a piezometer transect was installed across a second order stream of the subcatchment. The results so far suggest deep groundwater seepage to the aquifer with practically no base flow contributions to the stream in the mid-elevation range of the catchment. In 2009 the focus of research was within the subcatchment, in 2010 additionally a second piezometer transect was installed at a third order stream in the lower part of the catchment (main stem of the Mandae River) where more dynamic groundwater/surface water interactions are assumed due to expected higher groundwater levels in this part of the basin. In order to investigate these interactions piezometers equipped with temperature sensors and pressure transducers were installed directly into the river bed. Based on the observed temperature time series and the hydraulic potentials the water fluxes between the groundwater and the river can be calculated using the finite-difference numerical code, VS2DH. VS2DH solves Richard s equation for variably-saturated water flow, and the advection-conduction equation for energy transport. The field data collected at the second piezometer transect suggest that the investigated river reach exhibits primarily losing surface conditions throughout most of the year. Gaining groundwater conditions at the river reach are evident after monsoonal extreme precipitation events. At the transect streambed aggradation and degradation due to bedload transport was observed. Significant erosion has been reported throughout the catchment after extreme events. Results indicate that the event-based changes in streambed elevation, is an additional control on groundwater and surface water exchange. The streambed flux reversals were found to occur in conjunction with cooler in-stream temperatures at potential GW discharge locations. The export of nitrate and DOC were found to be variable in time and strongly correlated to the hydrologic dynamics, i.e. the monsoon and pre- and post-monsoon hydrological conditions. usw.
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