In soils and sediments there is a strong coupling between local biogeochemical processes and the distribution of water, electron acceptors, acids, nutrients and pollutants. Both sides are closely related and affect each other from small scale to larger scale. Soil structures such as aggregates, roots, layers, macropores and wettability differences occurring in natural soils enhance the patchiness of these distributions. At the same time the spatial distribution and temporal dynamics of these important parameters is difficult to access. By applying non-destructive measurements it is possible to overcome these limitations. Our non-invasive fluorescence imaging technique can directly quantity distribution and changes of oxygen and pH. Similarly, the water content distribution can be visualized in situ also by optical imaging, but more precisely by neutron radiography. By applying a combined approach we will clarify the formation and architecture of interfaces induces by oxygen consumption, pH changes and water distribution. We will map and model the effects of microbial and plant root respiration for restricted oxygen supply due to locally high water saturation, in natural as well as artificial soils. Further aspects will be biologically induced pH changes, influence on fate of chemicals, and oxygen delivery from trapped gas phase.
Der Beginn der nordhemisphärischen Vereisung und die Entwicklung kontinuierlichen Permafrostes in Eurasien zwischen dem Ende des Miozäns und dem frühen Pleistozän zählt zu den bedeutendsten klimatischen Ereignissen des Känozoikums. Der Zeitpunkt extensiver Vereisung auf den Kontinenten und des Arktischen Ozeans und damit verbundene Veränderungen der klimatischen Bedingungen bleibt bislang ungenau bestimmt.Speläotheme (sekundäre Höhlenkarbonate) stellen ein wichtiges Archiv kontinentaler Umweltbedingungen dar, welches durch besonders genaue radiometrische Altersmodelle für eine grosse Bandbreite an Paläoklimaproxies charakterisiert ist.Wir konnten erfolgreich diagenetisch unveränderte und datierbare Proben aus Zentral- und Nordsibirien identifizieren und schlagen eine Multi-proxy-Studie an U/Pb-datierten Stalagmiten vor. Diese Studie wird Einblicke in die thermalen und hydrologischen Bedingungen zwischen 10.3 Ma und 8 Ma liefern. Wasser aus in den Speläothemen eingeschlossenen Fluidinklusionen wird auf seine Isotopenzusammensetzung hin untersucht. Zudem wird die in den Speläothemen beobachtete Lamination genutzt, um die Saisonalität während des Torton und Messiniums zu rekonstruieren. Wir suchen finanzielle Unterstützung für die parallele Analyse der Isotopie des Fluidinklusionswassers, der Sauerstoff- und Kohlenstoffisotopie des Karbonates, und der Elementkonzentration in den Speläothemen. Diese Kombination geochemischer Methoden wird Einblicke in regionale Umweltbedingungen, die Niederschlagshistorie und Temperaturen während des Miozäns und vor der Entwicklung kontinuierlichen Permafrostes geben. Zusätzliche Proben werden genutzt, um den Wechsel vom eisfreien zu einem durch Permafrost charakterisierten Sibirien zeitlich genauer einzugrenzen.Das vorgeschlagene Projekt wird unser Wissen zur atmosphärischen Zirkulation, und daran geknüpfter Veränderungen des Feuchte- und Temperaturregimes während eines saisonal eisfreien Arktischen Ozeans erweitern.
It has been suggested that dying and decaying fine roots and root exudation represent important, if not the most important, sources of soil organic carbon (SOC) in forest soils. This may be especially true for deep-reaching roots in the subsoil, but precise data to prove this assumption are lacking. This subproject (1) examines the distribution and abundance of fine roots (greater than 2 mm diameter) and coarse roots (greater than 2 mm) in the subsoil to 240 cm depth of the three subsoil observatories in a mature European beech (Fagus sylvatica) stand, (2) quantifies the turnover of beech fine roots by direct observation (mini-rhizotron approach), (3) measures the decomposition of dead fine root mass in different soil depths, and (4) quantifies root exudation and the N-uptake potential with novel techniques under in situ conditions with the aim (i) to quantify the C flux to the SOC pool upon root death in the subsoil, (ii) to obtain a quantitative estimate of root exudation in the subsoil, and (iii) to assess the uptake activity of fine roots in the subsoil as compared to roots in the topsoil. Key methods applied are (a) the microscopic distinction between live and dead fine root mass, (b) the estimation of fine and coarse root age by the 14C bomb approach and annual ring counting in roots, (c) the direct observation of the formation and disappearance of fine roots in rhizotron tubes by sequential root imaging (CI-600 system, CID) and the calculation of root turnover, (d) the measurement of root litter decomposition using litter bags under field and controlled laboratory conditions, (e) the estimation of root N-uptake capacity by exposing intact fine roots to 15NH4+ and 15NO3- solutions, and (f) the measurement of root exudation by exposing intact fine root branches to trap solutions in cuvettes in the field and analysing for carbohydrates and amino acids by HPLC and Py-FIMS (cooperation with Prof. A. Fischer, University of Trier). The obtained data will be analysed for differences in root abundance and activity between subsoil (100-200 cm) and topsoil (0-20 cm) and will be related to soil chemical and soil biological data collected by the partner projects that may control root turnover and exudation in the subsoil. In a supplementary study, fine root biomass distribution and root turnover will also be studied at the four additional beech sites for examining root-borne C fluxes in the subsoil of beech forests under contrasting soil conditions of different geological substrates (Triassic limestone and sandstone, Quaternary sand and loess deposits).
During the first project period we developed a general approach to quantify soil pore structure based on X-ray micro-tomography Vogel et al. (2010) which is applicable at various scales to cover soil pores larger that 0.05 mm in a representative way. Based on this method we generated equivalent network models to numerically simulate flow and transport of dissolved chemicals. The existing network model was extended to handle reactive transport and infiltration processes which are especially critical for matter flux in soil. The results were compared to experimental findings. The original research question 'what does a particle see on its way through soil' could be answered quantitatively for various boundary conditions including steady state flux and infiltration. However, we identified various critical aspects of the proposed modeling concept which will be in the focus of the second period. This includes 1) the spatial arrangement of interfaces having different quality which is crucial for chemical interactions and pore scale water dynamics, 2) the realistic multiphase dynamics at the pore scale which need to reflect the dynamic pressure and movement of trapped non-wetting phase and 3) the parametrization of structural complexity which need to be developed beyond the measurement of continuous Minkowski functions to allow the development of quantitative relations between structure and function. These aspects will be explored in a joint experiments in cooperation with partners within the SPP.
Die südecuadorianischen Anden beherbergen eine außergewöhnlich hohe Artenvielfalt. Viele verschiedene Umweltfaktoren beeinflussen sich auf sehr limitiertem Raum und erschaffen so einzigartige und komplexe Ökosysteme. Dieses Gebiet ist jedoch auf Grund des zunehmenden menschlichen Einflusses durch die fortschreitende Intensivierung der Landnutzung und des globalen Wandels hochgefährdet. Wir wissen nur wenig über die paläoökologische Geschichte und Landschaftsdynamik dieses Gebiets. Die Information über das warum und wie einer Veränderung von Ökosystemen ist unerlässlich für die Entwicklung innovativer Strategien für Naturschutz und im Hinblick auf zukünftige Klimaveränderungen. In der vorliegenden Studie werden palynologische Analysen aus den südecuadorianischen Anden vorgestellt, die dazu beitragen, Muster und Prozesse heutiger und vergangener Ökosysteme zu beleuchten. Eine paläoökologische Studie des Quimsacocha-Vulkanbeckens auf der östlichen Erhebung der Westkordillere der südecuadorianischen Anden deckt Klima-, Vegetations- und Brandregimeveränderungen in dieser Region seit dem frühen Holozän auf. Das mittlere Holozän war eine Zeit starker Umweltveränderungen, verursacht durch ein trockenes und wohl wärmeres Klima. Während des späten Holozäns wechselten sich mehrere Kalt-und Warmphasen ab. Brände können seit dem frühen Holozän im Gebiet verzeichnet werden. Sie könnten ein erstes Zeichen menschlichen Einflusses darstellen. Mit anderen paläoökologischen Aufzeichnungen aus den südecuadorianischen Anden verglichene multivariate Analysen decken teilweise konstrastierende Entwicklungen an den verschieden Standorten auf, die vermutlich durch die Heterogenität der Umweltfaktoren zu erklären sind. Weiterhin wurden Studien zum Verhältnis von heutigem Pollenregen mit der Vegetation in der Podocarpus Nationalpark-Region durchgeführt, um die Pollenverbreitungsmuster innerhalb der verschiedenen Vegetationstypen, prämontaner Wald, unterer Bergwald, oberer Bergwald und Páramo, zu verstehen und damit eine bessere Grundlage zur Interpretation fossiler Pollendaten zu schaffen. Ein Vergleich von Abundanz und An-/Abwesenheitsdaten von Familien als taxonomischer Einheit für Pollen- und Vegetation zeigt, dass Diversität, Verbreitung und Häufigkeiten beider Datensätze gut miteinander in Verbindung gebracht werden können. Dennoch werden die Muster durch variierende Anteile von durch Ferntransport eingetragenen Pollenkörnern sowie durch unterschiedliche Pollenproduktivität verschiedener Taxa und heterogene Windsysteme beeinflusst. Analysen der Pollenakkumulationsraten, die über drei Jahre erfasst wurden, lassen auf eine geringe inter-annuelle aber hohe räumliche Variation in den Daten schließen. (Text gekürzt)
Soil erosion and desertification, blowing and drifting snow, transport of pollen and seeds, dust entrainment and transport of (particulate) pollutants are some among a large number of processes governed by wind blowing on an erodible surface. The impact of these processes on the environment and both directly and indirectly on the human societies is huge, having implications for land surface geomorphology, human health, water resources, soil fertility and ecosystem biogeochemistry. In order to have full understanding of the physical mechanisms responsible for soil/snow entrainment, it is thus of crucial importance to investigate the very inner layer of the atmosphere, as close as possible to the ground. The interaction between the wind and the earth surface gives rise to a turbulent boundary layer which can lead to erosion of particles, often ranging from micron sized dust to millimeter sand grains. The action of the turbulent boundary layer essentially lead to a stress acting on the surface and ultimately a force acting on each single particle. In fluid mechanics the latter is referred to as the shear stress. In all surface transport models (from dust in deserts, to gravel in rivers, to PM10 particles in an industrial area) the shear stress is the key parameter. The amount of particles transported has almost always been described as a function of the difference between the shear stress and a threshold. Therefore, the prediction of the shear stress acting on the surface is a crucial pre-requisite to estimate mass transport rates. Very often, erodible soil or snow surfaces are covered by vegetation. It has long been known that vegetated surfaces prevent soil erosion by means of mainly three mechanisms. Firstly vegetation shelters the soil by simply reducing the surface exposed to the wind. Secondly, vegetation can trap particles in motion hence acting like a sink for sediments. Finally, vegetation decreases the shear stress acting on the erodible ground by absorbing the momentum flux from the airflow above, therefore weakening the erosive power of the wind. In this project we are concerned with quantifying this last effect for a selected variety of plants species and plant cover densities. The long term application of such study will be to develop a model which, for a given wind velocity and vegetation cover is able to predict the shear stress acting on the bottom surface. Such information can then be used as an input for sediment/snow transport models.
The aim of CH-HALOMED is to install a measurement equipment to analyse halogenated greenhouse gases in the laboratory of Empa in addition to the continuously running identical system at Jungfraujoch (MEDUSA). This measurement equipment has been developeed by SIO in La Jolla (California) and is the main instrumentation used world-wide to perform state-of-the art measurements of halogenated greenhouse gases. The scientific goals of CH-HALOMED are to developing analytical methods for new halocarbons used in the industry and in consumer products and advance the sample trapping technology within the MEDUSA. Furthermore, the new system will allow sustaining the intercomparability within the European network: System for Observation of Halogenated Greenhouse Gases in Europe (SOGE) and its extension to China (SOGE-A) and linking of standards and scales at Jungfraujoch to those of AGAGE/NOAA. The instrumentation of CH-HALOMED will be used to analyse atmospheric halocarbons from international projects such as CARIBIC (air sampled by commercial aircrafts) and Antarctic samples by KOPRI (Korea Polar Research Institute) and NILU (Norwegian Institute for Air Research). Finally the MEDUSA system will be used for quantification of Swiss emissions of halogenated greenhouse gases by analysing air samples from the suburban station of Duebendorf (near Zurich). The context of CH-HALOMED is the global effort to assess the contribution of halogenated greenhouse gases to global warming. This is achieved by estimating global emissions of halogenated greenhouse gases (i.e. CFCs, HFCs, SF6) uisng their behaviour in the background air masses and to assess regional sources, using pollution events occuring at measurement sites in different continents. Furthermore, the MEDUSA system is extremely well-suited for detection of newly released industrial compounds in the atmosphere. The applicability of this concept has already been shown by Empa using existing equipments. With the new MEDUSA Empa has the possibility to advance in this field to faster reacting hydrofluorcarbons, which will be produced by industry in the next years. Although these compounds do have a minor influence on the global warming, their degradation products (i.e. fluorinated organic acids) could potentially affect aquatic bio-organisms.
Introduction: In aquatic systems, the bioavailability of a compound is dependent on numerous factors such as partitioning between water, different organisms and solids, biotransformation and food web transfer. This project dealt with the fate of an important environmental xeno-estrogen, 17-ethinylestradiol (EE2), in the aquatic environment. Therefore, the kinetics of EE2 in indicator species representing the different trophic levels of an ecosystem were assessed. As primary producers, green algae (Desmodesmus suspicatus) were selected. The water flea Daphnia magna and larvae of the midge Chironomus riparius were introduced as primary consumers of the water phase and the sediment, respectively. Finally, water as well as dietary uptake of EE2 were investigated in a target species and secondary consumer: zebrafish (Danio rerio). Methodology: In a first series of experiments, uptake of 14C-labelled EE2 (14C-EE2) from the water phase and elimination by the different organisms were investigated over time. In a second test series, both primary consumers were fed 14C-EE2 spiked algae in order to study bioaccumulation. Uptake of 14C-EE2 by chironomid larvae after water and sediment spiking was compared, including sediments of different composition. In a third series of experiments, male fish were short term (48 h) exposed to 14C-EE2 through different routes: by water exposure (WE) and by dietary exposure (DE) via both contaminated daphnids and chironomid larvae. Distribution of 14C-EE2 in the fish was studied by measuring the amount of radioactivity (RA) in the different fish tissues. Additionally, the effect of EE2 on the vitellogenin (Vtg) induction in male fish was compared after WE and DE in a long term (14 d) experiment. The RA in liquid samples was quantified by means of liquid scintillation counting (LSC). Solid samples were subjected to combustion in a biological oxidiser, trapping (14)CO2, measured with LSC. Water and organism extracts were analysed by means of HPLC with a radiodetector, except for algae extracts that were subjected to TLC. Metabolites were identified with GC-MS, high resolution LC-MS and enzymatic hydrolysis followed by HPLC with radiodetection. Metabolites, detected in the water phase, were tested for estrogenic activity by means of YES and ER-CALUX assays. Results: Accumulation and effects: Of the four organisms mentioned above, bioconcentration of 14C-EE2 was highest in the algae. Whereas the growth rate of D. subspicatus was significantly affected at high EE2 concentrations compared to unexposed algae, EE2 had no acute effects on D. magna and C. riparius. Daphnids showed a higher bioaccumulation potential after exposure via spiked algae. For chironomids, water exposure was the predominant uptake route. The presence of sediment lowered the bioavailability of 14C-EE2 to the larvae after both water and sediment spiking. Nevertheless, uptake was higher when the nutritional quality of the sediment was better. Etc.
Selenium is a natural trace element that is of fundamental importance to human health. However, it is also an element with a small range between dietary deficiency (less than 40 micrograms per day) and toxic dosages (over 400 micrograms per day). The extreme geographical variation in environmental selenium concentrations has resulted in significant health problems. For example, in China, widespread serious diseases such as Kashin-Beck and Keshan disease have been related to the very low selenium contents of locally produced food. To deal with health problems related to deficient or excess levels of selenium in the environment, it is essential to get a better understanding of the processes that control the global distribution of selenium. This research project is aimed at investigating potentially important sources, pathways and sinks of natural selenium species. Two interdisciplinary work programs are planned that combine different scientific methodologies in the field of environmental biogeochemistry. One work program will focus on the production of volatile selenium species by marine phytoplankton, which could be an important source of selenium to the continent. Research methods involve microcosm studies with marine phytoplankton and subsequent trapping and characterization of produced volatile selenium species. Expected results will greatly contribute to an improved understanding of the role of marine phytoplankton in the global selenium cycle. Also, field experiments are planned to quantify fluxes of volatile selenium compounds from continental environments. The deposition of atmospherically transported selenium on the continent will be the main focus of the other work program. A key field site for this work program is the Chinese Loess Plateau, which has the potential to serve as environmental archive of atmospherically deposited selenium over the last 2.6 million years. The presence and mobility of trace elements will be studied in the loess sediments using different geochemical analytical techniques. Expected results will advance understanding of atmospheric selenium deposition and give insight in the role that climate plays on the continental abundance of selenium. These studies will pave the way for future predictions of selenium distribution patterns based on climate data. Knowledge on biogenic selenium production in the ocean and continental deposition of selenium is needed to understand the environmental fate of both natural and anthropogenic selenium emissions. This understanding is essential to prevent future selenium health hazards in a world that is increasingly affected by human activities.
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