Water, carbon and nitrogen are key elements in all ecosystem turnover processes and they are related to a variety of environmental problems, including eutrophication, greenhouse gas emissions or carbon sequestration. An in-depth knowledge of the interaction of water, carbon and nitrogen on the landscape scale is required to improve land use and management while at the same time mitigating environmental impact. This is even more important under the light of future climate and land use changes.In the frame of the proposal 'Uncertainty of predicted hydro-biogeochemical fluxes and trace gas emissions on the landscape scale under climate and land use change' we advocate the development of fully coupled, process-oriented models that explicitly simulate the dynamic interaction of water, carbon and nitrogen turnover processes on the landscape scale. We will use the Catchment Modelling Framework CMF, a modular toolbox to implement and test hypothesis of hydrologic behaviour and couple this to the biogeochemical LandscapeDNDC model, a process-based dynamic model for the simulation of greenhouse gas emissions from soils and their associated turnover processes.Due to the intrinsic complexity of the models in use, the predictive uncertainty of the coupled models is unknown. This predictive (global) uncertainty is composed of stochastic and structural components. Stochastic uncertainty results from errors in parameter estimation, poorly known initial states of the model, mismatching boundary conditions or inaccuracies in model input and validation data. Structural uncertainty is related to the flawed or simplified description of natural processes in a model.The objective of this proposal is therefore to quantify the global uncertainty of the coupled hydro-biogeochemical models and investigate the uncertainty chain from parameter uncertainty over forcing data uncertainty up the structural model uncertainty be setting up different combinations of CMF and LandscapeDNDC. A comprehensive work program has been developed structured in 4 work packages, that consist of (1) model set up, calibration and uncertainty assessment on site scale followed by (2) an application and uncertainty assessment of the coupled model structures on regional scale, (3) global change scenario analyses and finally (4) evaluating model results in an ensemble fashion.Last but not least, a further motivation of this proposal is to provide project results in a manner that they support planning and decision taking under uncertainty, as this proposal is part of the package proposal on 'Methodologies for dealing with uncertainties in landscape planning and related modelling'.
Dissolved organic matter (DOM) is one major source of subsoil organic matter (OM). P5 aims at quantifying the impact of DOM input, transport, and transformation to the OC storage in the subsoil environment. The central hypotheses of this proposal are that in matric soil the increasing 14C age of organic carbon (OC) with soil depth is due to a cascade effect, thus, leading to old OC in young subsoil, whereas within preferential flowpaths sorptive stabilization is weak, and young and bioa-vailable DOM is translocated to the subsoil at high quantities. These hypotheses will be tested by a combination of DOC flux measurements with the comparative analysis of the composition and the turnover of DOM and mineral-associated OM. The work programme utilizes a DOM monitoring at the Grinderwald subsoil observatory, supplemented by defined experiments under field and labora-tory conditions, and laboratory DOM leaching experiments on soils of regional variability. A central aspect of the experiments is the link of a 13C-leaf litter labelling experiment to the 14C age of DOM and OM. With that P5 contributes to the grand goal of the research unit and addresses the general hypotheses that subsoil OM largely consists of displaced and old OM from overlying horizons, the sorption capacity of DOM and the pool size of mineral-associated OM are controlled by interaction with minerals, and that preferential flowpaths represent 'hot spots' of high substrate availability.
We consider clay minerals, iron oxides and charcoal as major components controlling the formation of interfaces relevant for sorption of organic chemicals, as they control the assemblage of organic matter and mineral particles. We studied the formation of interfaces in batch incubation experiments with inoculated artificial soils consisting of model compounds (clay minerals, iron oxide, char) and natural soil samples. Results show a relevant contribution of both iron oxides and clay minerals to the formation of organic matter as sorptive interfaces for hydrophobic compounds. Thus, we intend to focus our work in the second phase on the characterization of the interface as formed by organic matter associated with clay minerals and iron oxides. The interfaces will be characterized by the BET-N2 and ethylene glycol monoethyl ether (EGME) methods and 129Xe and 13C NMR spectroscopy for determination of specific surface area, sorptive domains in the organic matter and microporosity. A major step forward is expected by the analysis of the composition of the interface at different resolution by reflected-light microscopy (mm scale), SEM (scanning electron microscopy, micrometer scale) and secondary ion mass spectrometry at the nanometer scale (nanoSIMS). The outcomes obtained in combination with findings from cooperation partners will help to unravel the contribution of different types of soil components on the formation and characteristics of the biogeochemical interfaces and their effect on organic chemical sorption.
For surface soils, the mechanisms controlling soil organic C turnover have been thoroughly investigated. The database on subsoil C dynamics, however, is scarce, although greater than 50 percent of SOC stocks are stored in deeper soil horizons. The transfer of results obtained from surface soil studies to deeper soil horizons is limited, because soil organic matter (SOM) in deeper soil layers is exposed to contrasting environmental conditions (e.g. more constant temperature and moisture regime, higher CO2 and lower O2 concentrations, increasing N and P limitation to C mineralization with soil depth) and differs in composition compared to SOM of the surface layer, which in turn entails differences in its decomposition. For a quantitative analysis of subsoil SOC dynamics, it is necessary to trace the origins of the soil organic compounds and the pathways of their transformations. Since SOM is composed of various C pools which turn over on different time scales, from hours to millennia, bulk measurements do not reflect the response of specific pools to both transient and long-term change and may significantly underestimate CO2 fluxes. More detailed information can be gained from the fractionation of subsoil SOM into different functional pools in combination with the use of stable and radioactive isotopes. Additionally, soil-respired CO2 isotopic signatures can be used to understand the role of environmental factors on the rate of SOM decomposition and the magnitude and source of CO2 fluxes. The aims of this study are to (i) determine CO2 production and subsoil C mineralization in situ, (ii) investigate the vertical distribution and origin of CO2 in the soil profile using 14CO2 and 13CO2 analyses in the Grinderwald, and to (iii) determine the effect of environmental controls (temperature, oxygen) on subsoil C turnover. We hypothesize that in-situ CO2 production in subsoils is mainly controlled by root distribution and activity and that CO2 produced in deeper soil depth derives to a large part from the mineralization of fresh root derived C inputs. Further, we hypothesize that a large part of the subsoil C is potentially degradable, but is mineralized slower compared with the surface soil due to possible temperature or oxygen limitation.
Chlorinated ethylenes are prevalent groundwater contaminants. Numerous studies have addressed the mechanism of their reductive dehalogenation during biodegradation and reaction with zero-valent iron. However, despite insight with purified enzymes and well-characterized chemical model systems, conclusive evidence has been missing that the same mechanisms do indeed prevail in real-world transformations. While dual kinetic isotope effect measurements can provide such lines of evidence, until now this approach has not been possible for chlorinated ethylenes because an adequate method for continuous flow compound specific chlorine isotope analysis has been missing. This study attempts to close this prevalent research gap by a combination of two complementary approaches. (1) A novel analytical method to measure isotope effects for carbon and chlorine. (2) A carefully chosen set of well-defined model reactants representing distinct dehalogenation mechanisms believed to be important in real-world systems. Isotope trends observed in biotic and abiotic environmental dehalogenation will be compared to these model reactions, and the respective mechanistic hypotheses will be confirmed or discarded. With this hypothesis-driven approach it is our goal to elucidate for the first timdehalogenation reactions.
Das Hauptziel des ComparCE Projekts ist eine umfassende Einschätzung verschiedener Climate Engineering (CE) Maßnahmen gegeneinander und gegenüber Mitigationsbemühungen. Dabei sollen insbesondere Modelunsicherheiten berücksichtigt werden, da eine solche Einschätzung im CE Fall ausschließlich auf Modellsimulationen beruht. In diesem Projekt wollen wir darüber hinaus Fragen beantworten, die unserer Meinung bislang im CE Zusammenhang nicht bearbeitet wurden. Als ersten und zentralen Schritt wollen wir untersuchen welche Metriken und Indikatoren für die Beurteilung von CE Methoden, und somit für das gesamte Schwerpunkt Programm, wichtig sind und wie diese sich von den Metriken im Kontext von Klimawandel unterscheiden. Diese Art der Forschung gab es im Kontext Klimawandel bereits, sie fehlt bislang aber für CE. Durch Austausch mit internationalen Forschergruppen wurde klar, dass eine die wahrscheinlichste Implementierung von CE Maßnahmen aus einer Kombination der verschiedenen Technologien besteht. Daher wollen wir in diesem Projekt untersuchen wie das Erdsystem auf eine Kombination verschiedener CE Maßnahmen reagiert, und ob es möglich ist die Signale der einzelnen Methoden jeweils zuzuordnen. In diesem Zusammenhang werden wir ebenfalls untersuchen ob und wie die Effektivität der CE Maßnahmen vom Hintergrund-Klimazustand abhängt und ob z.B. der Zeitpunkt der Umsetzung von CE eine Rolle spielt. Darüber hinaus wollen wir robuste, regionale CE Muster untersuchen um ebenfalls auf die regionalen Auswirkungen von CE eingehen zu können. Das ist besonders wichtig, weil für die lokale Öffentlichkeit regionale Klimaextreme mehr Bedeutung haben als globale Mittelwerte. Diese Analysen werden ebenfalls den Findungsprozess der Metriken informieren. Zusätzlich wird die plötzliche Terminierung von CE Maßnahmen im Kontext der Geschwindigkeit des Terminations-Schocks untersucht. Schlussendlich basiert die gesamte Beurteilung von CE Maßnahmen auf Modellergebnissen, daher finden wir, dass ein wichtiger Beitrag für die CE Debatte eine Beurteilung der model-internen Unsicherheiten ist. Diese werden mit Anhang von Änderungen der Wahrscheinlichkeitsverteilung von Metriken quantifiziert, so können zum Beispiel aussagen über die Wahrscheinlichkeit einer Richtwert-Überschreitung der gegebenen Zukunftsszenarien getroffen werden. Die Ergebnisse diese Projekts erlauben eine umfassende Einschätzung der untersuchten CE Maßnahmen gegenüber Migration, unter Berücksichtigung von Unsicherheiten in Modellen, den Zukunftsszenarien und Metriken, welche im Laufe des Projekts iterative mit anderen Teilprojekten diskutiert werden.
The relevance of biogeochemical gradients for turnover of organic matter and contaminants is yet poorly understood. This study aims at the identification and quantification of the interaction of different redox processes along gradients. The interaction of iron-, and sulfate reduction and methanogenesis will be studied in controlled batch and column experiments. Factors constraining the accessibility and the energy yield from the use of these electron acceptors will be evaluated, such as passivation of iron oxides, re-oxidation of hydrogen sulfide on iron oxides. The impact of these constraints on the competitiveness of the particular process will then be described. Special focus will be put on the evolution of methanogenic conditions in systems formerly characterized by iron and sulfate reducing condition. As methanogenic conditions mostly evolve from micro-niches, methods to study the existence, evolution and stability of such micro-niches will be established. To this end, a combination of Gibbs free energy calculations, isotope fractionation and tracer measurements, and mass balances of metabolic intermediates (small pool sizes) and end products (large pool sizes) will be used. Measurements of these parameters on different scales using microelectrodes (mm scale), micro sampling devices for solutes and gases (cm scale) and mass flow balancing (column/reactor scale) will be compared to characterize unit volumes for organic matter degradation pathways and electron flow. Of particular interest will be the impact of redox active humic substances on the competitiveness of involved terminal electron accepting processes, either acting as electron shuttles or directly providing electron accepting capacity. This will be studied using fluorescence spectroscopy and parallel factor analysis (PARAFAC) of the gained spectra. We expect that the results will provide a basis for improving reactive transport models of anaerobic processes in aquifers and sediments.
Forschungsschwerpunkt: - Entwicklung differenzierter Materialien und E-Learning-Konzeptionen zur Qualifizierung von Zielgruppen, die in energiebezogenen Bereichen tätig sind bzw. entsprechende Qualifikationen anstreben - systematische mediendidaktische Fortentwicklung bestehender Blended-Learning-Konzeptionen. Ziele: - Vermittlung grundlegende energiewirtschaftliche Zusammenhänge für Nicht-Ökonomen, die in der Energiebranche tätig sind bzw. entsprechende Qualifikationen anstreben - Ziel ist das Erlangen vertiefter Einsichten in die verschiedenen Facetten der Energieversorgung und -nutzung, um ein breiteres Verständnis für die vielschichtigen Aufgaben und Anforderungen an Unternehmen in der Branche. Beschreibung: - Im Rahmen der ersten Projektphase wurde ein internetgestützter Qualifizierungsbaustein 'Energy Economics' entwickelt und eine internetgestützte Lehreinheit konzipiert. Diese wurde im Wintersemester 2013/2014 im Studiengang 'Engineering Physics' erprobt und evaluiert. Das Feedback der Teilnehmer fiel sehr positiv aus. - In der zweiten Projektphase (2014) ein weiterer internetgestützter Qualifizierungsbaustein entwickelt, auf dessen Basis ebenfalls eine Veranstaltung konzipiert, durchgeführt und evaluiert wird. Im Mittelpunkt steht darin die Auseinandersetzung mit den erneuerbaren Energien, insbesondere im Hinblick auf ihren Einsatz in Entwicklungs- und Schwellenländern. Die Lehrveranstaltung wird ausschließlich onlinebasiert durchgeführt werden. Ergebnisse/Materialien: Qualifizierungsbaustein 'Energy Economics', der sich thematisch mit den Schwerpunkten - grundlegende Strukturen internationaler Energiemärkte (insb. Erdöl, Erdgas, Kohle), - Besonderheiten der Märkte für leitungsgebundene Energieversorgung, - Bedeutung energiepolitischer Rahmensetzung auf den Märkten sowie - Förderung erneuerbarer Energien und ihrer Wirkung auf Märkten auseinandersetzt.
The magnetosphere of a planet is controlled by a number of factors such as the intrinsic magnetic field, the atmosphere and ionosphere, and the solar wind. Different combinations of these control factors are at work at the terrestrial planets Mercury, Venus, Earth, and Mars, hence they form a very suitable set for quantitative comparative studies. A significant intrinsic dipolar magnetic field is present only on Earth and on Mercury. However, the configuration at Mercury differs considerably from that at Earth because Mercury does not support an atmosphere and ionosphere, the dipolar field is much weaker, the solar wind denser, and the interplanetary magnetic field stronger. Both Mars and Venus have atmospheres but lack a global planetary magnetic field, with regional crustal magnetization being present on Mars. This proposal aims at investigating and comparing electrical current systems in the space environments of terrestrial planets using magnetic vector data collected by orbiting spacecraft such as Venus Express, Mars Global Surveyor, CHAMP (Earth), and MESSENGER (Mercury). We propose to construct data-driven and physically meaningful representations that reveal and quantify the influence of various control factors. To achieve this, we will tailor Empirical Orthogonal Function (EOF) analysis and other multivariate methods to the specifics of planetary magnetic field observations. In contrast to representations that build on predefined functions like spherical harmonics, basis functions in the EOF approach are derived directly from the data. EOFs are designed to extract dominant coherent variations for further interpretation in terms of known physical phenomena, and then, in a regression step, for modeling using suitable control variables. The EOF methodology thus allows quantifying the relative importance of control factors for each planet individually, and thus contributes to the solution of topical science questions. The resulting empirical models will facilitate comparative studies of current systems at the terrestrial planets.
To predict ecosystem reactions to elevated atmospheric CO2 (eCO2) it is essential to understandthe interactions between plant carbon input, microbial community composition and activity and associated nutrient dynamics. Long-term observations (greater than 13 years) within the Giessen Free Air Carbon dioxide Enrichment (Giessen FACE) study on permanent grassland showed next to an enhanced biomass production an unexpected strong positive feedback effect on ecosystem respiration and nitrous oxide (N2O) production. The overall goal of this study is to understand the long-term effects of eCO2 and carbon input on microbial community composition and activity as well as the associated nitrogen dynamics, N2O production and plant N uptake in the Giessen FACE study on permanent grassland. A combination of 13CO2 pulse labelling with 15N tracing of 15NH4+ and 15NO3- will be carried out in situ. Different fractions of soil organic matter (recalcitrant, labile SOM) and the various mineral N pools in the soil (NH4+, NO3-, NO2-), gross N transformation rates, pool size dependent N2O and N2 emissions as well as N species dependent plant N uptake rates and the origin of the CO2 respiration will be quantified. Microbial analyses will include exploring changes in the composition of microbial communities involved in the turnover of NH4+, NO3-, N2O and N2, i.e. ammonia oxidizing, denitrifying, and microbial communities involved in dissimilatory nitrate reduction to ammonia (DNRA). Stable Isotope Probing (SIP) and mRNA based analyses will be employed to comparably evaluate the long-term effects of eCO2 on the structure and abundance of these communities, while transcripts of these genes will be used to target the fractions of the communities which actively contribute to N transformations.
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