550 Geowissenschaften
Refine
Year of publication
Document Type
- Article (888)
- Doctoral Thesis (194)
- Contribution to a Periodical (32)
- Book (26)
- Working Paper (22)
- Part of Periodical (20)
- Conference Proceeding (18)
- Part of a Book (9)
- Diploma Thesis (8)
- diplomthesis (7)
- Other (5)
- Report (5)
- Master's Thesis (4)
- Review (4)
- Periodical (3)
- Bachelor Thesis (2)
- Habilitation (2)
- Preprint (2)
Language
Keywords
- climate change (11)
- Climate change (7)
- Klima (7)
- Klimaänderung (7)
- Modellierung (7)
- COSMO-CLM (6)
- Klimawandel (6)
- precipitation (6)
- Atmospheric chemistry (5)
- Deutschland (5)
Institute
- Geowissenschaften (775)
- Geowissenschaften / Geographie (135)
- Biodiversität und Klima Forschungszentrum (BiK-F) (61)
- Geographie (61)
- Senckenbergische Naturforschende Gesellschaft (54)
- Präsidium (44)
- Extern (28)
- Biowissenschaften (22)
- Institut für Ökologie, Evolution und Diversität (8)
- Physik (8)
Inclusions of breyite (previously known as walstromite-structured CaSiO3) in diamond are usually interpreted as retrogressed CaSiO3 perovskite trapped in the transition zone or the lower mantle. However, the thermodynamic stability field of breyite does not preclude its crystallization together with diamond under upper-mantle conditions (6–10 GPa). The possibility of breyite forming in subducted sedimentary material through the reaction CaCO3 + SiO2 = CaSiO3 + C + O2 was experimentally evaluated in the CaO–SiO2–C–O2 ± H2O system at 6–10 GPa, 900–1500 ∘C and oxygen fugacity 0.5–1.0 log units below the Fe–FeO (IW) buffer. One experimental series was conducted in the anhydrous subsystem and aimed at determining the melting temperature of the aragonite–coesite (or stishovite) assemblage. It was found that melting occurs at a lower temperature (∼1500 ∘C) than the decarbonation reaction, which indicates that breyite cannot be formed from aragonite and silica under anhydrous conditions and an oxygen fugacity above IW – 1. In the second experimental series, we investigated partial melting of an aragonite–coesite mixture under hydrous conditions at the same pressures and redox conditions. The melting temperature in the presence of water decreased strongly (to 900–1200 ∘C), and the melt had a hydrous silicate composition. The reduction of melt resulted in graphite crystallization in equilibrium with titanite-structured CaSi2O5 and breyite at ∼1000 ∘C. The maximum pressure of possible breyite formation is limited by the reaction CaSiO3 + SiO2 = CaSi2O5 at ∼8 GPa. Based on the experimental results, it is concluded that breyite inclusions found in natural diamond may be formed from an aragonite–coesite assemblage or carbonate melt at 6–8 GPa via reduction at high water activity.
The design of rainwater harvesting based gardens requires considering current climate but also climate change during the lifespan of the facility. The goal of this study is to present an approach for designing garden variants that can be safely supplied with harvested rainwater, taking into account climate change and adaptation measures. In addition, the study presents a methodology to quantify the effects of climate change on rainwater harvesting based gardening. Results of the study may not be accurate due to the assumptions made for climate projections and may need to be further refined. We used a tank flow model and an irrigation water model. Then we established three simple climate scenarios and analyzed the impact of climate change on harvested rain and horticulture production for a semi-arid region in northern Namibia. In the two climate scenarios with decreased precipitation and medium/high temperature increase; adaptation measures are required to avoid substantial decreases in horticulture production. The study found that the most promising adaptation measures to sustain yields and revenues are a more water efficient garden variant and an enlargement of the roof size. The proposed measures can partly or completely compensate the negative impacts of climate change.
In situ rainwater harvesting has a long history in arid and semi-arid regions of the world buffering water shortages for human consumption and agriculture. In the context of an Integrated Water Resource Management (IWRM) in the Cuvelai Basin in northern Namibia, roof top rainwater harvesting is being introduced to a rural community for the irrigation of household scale gardens for the cultivation of horticulture products. This study elaborates how harvested rainwater can be used for garden irrigation in a sustainable manner evaluating ecologic, economic and social implications. Considering local conditions eight cropping scenarios were designed, including different criteria as well as one and two annual planting seasons. These schemes were tested under present climate conditions and under three future climate change scenarios for 2050 with the help of a tank model designed to model monthly tank inflows and outflows. Special attention was laid on risk and uncertainty aspects of varying inter-annual and interseasonal precipitation and future climate change. A framework for the assessment of sustainability was adapted to the purposes of this study and indicators have been developed in order to assess the cropping and irrigation schemes for sustainability.
The study found that with the given tank size of 30 m³, depending on crop scenario, under optimized conditions a garden area of 60 to 90 m³ can be irrigated. The choice of crops highly impacts water use efficiency and economic profitability, compared to the considerably lower impact of amount of annual planting seasons and future climate change. In the case of worsening future climate conditions, adaptation measures need to be taken as especially the economic as well as the environmental situation are expected to exacerbate due to expected decreases in yields and revenues. Already under present conditions however, the economic dimension represents the most limiting factor to sustainability, particularly due to the excessive investment costs of the rainwater harvesting and gardening facility. Nonetheless, rainwater harvesting in combination with gardening can be regarded as successful in securing household nutrition, providing sufficient horticulture products for household consumption or market sale. At the same time with the optimal choice of crops the investment costs can be recovered within the end of the lifespan of the facility.
Water is scarce in semi-arid and arid regions. Using alternative water sources (i.e. non-conventional water sources), such as municipal reuse water and harvested rain, contributes to using existing water resources more efficiently and productively. The aim of this study is to evaluate the two alternative water sources reuse water and harvested rain for the irrigation of small-holder agriculture from a system perspective. This helps decision and policy makers to have proper information about which system and technology to adopt under local conditions. For this, the evaluation included ecologic, societal, economic, institutional and political as well as technical aspects. For the evaluation, the study area in central-northern Namibia was chosen in the frame of the research and development project CuveWaters. The main methods used include a mathematical material flow analysis, the computation and modelling of crop requirements, a multi-criteria decision analysis using the Analytical Hierarchy Process (AHP) method and a financial cost-benefit analysis. From a systemic perspective, the proposed novel systems were compared to the exciting conventional infrastructure. The results showed that both water reuse and rainwater harvesting systems for the irrigation of small-holder horticulture offer numerous technological, ecologic, economic, societal, institutional and political benefits. Rainwater harvesting based gardens have a positive benefit-cost ratio under favorable conditions. Government programs could fund the infrastructure investment costs, while the micro-entrepreneur can assume a micro-credit to finance operation and maintenance costs. Installing sanitation in informal settlements and reusing municipal water for irrigation reduces the overall water demand of households and agriculture by 39%, compared to improving sanitation facilities in informal settlements without reusing the water for agriculture. Given that water is the limiting factor for crop fertigation, the generated nutrient-rich reuse water is sufficient to annually irrigate about 10 m2 to 13 m2 per sanitation user. Compared to crop nutrient requirements, there are too many nutrients in the reuse water. Thus when using nutrient-rich reuse water, no use of fertilizers and a careful salt management is necessary. When comparing this novel system with improved sanitation, advanced wastewater treatment and nutrient-rich water reuse to the conventional and to two adapted systems, results showed that the novel CuveWaters system is the best option for the given context in a semi-arid developing country. Therefore, the results of this study suggest a further roll-out of the novel CuveWaters system. The methodology developed and the results of this study demonstrated that taking sanitation users into consideration plays a major role for the planning of an integrated water reuse infrastructure because they are the determinant factor for the amount of available nutrient-rich reuse water. In addition, it could be shown that water reuse and rainwater harvesting systems for the irrigation of small-scale gardens provide a wide range of benefits and can be key to using scarce water resources more efficiently and to contributing to the Sustainable Development Goals.
The theoretical basis for the link between the leaf exchange of carbonyl sulfide (COS), carbon dioxide (CO2) and water vapour (H2O) and the assumptions that need to be made in order to use COS as a tracer for canopy net photosynthesis, transpiration and stomatal conductance, are reviewed. The ratios of COS to CO2 and H2O deposition velocities used to this end are shown to vary with the ratio of the internal to ambient CO2 and H2O mole fractions and the relative limitations by boundary layer, stomatal and internal conductance for COS. It is suggested that these deposition velocity ratios exhibit considerable variability, a finding that challenges current parameterizations, which treat these as vegetation-specific constants. COS is shown to represent a better tracer for CO2 than H2O. Using COS as a tracer for stomatal conductance is hampered by our present poor understanding of the leaf internal conductance to COS. Estimating canopy level CO2 and H2O fluxes requires disentangling leaf COS exchange from other ecosystem sources/sinks of COS. We conclude that future priorities for COS research should be to improve the quantitative understanding of the variability in the ratios of COS to CO2 and H2O deposition velocities and the controlling factors, and to develop operational methods for disentangling ecosystem COS exchange into contributions by leaves and other sources/sinks. To this end, integrated studies, which concurrently quantify the ecosystem-scale CO2, H2O and COS exchange and the corresponding component fluxes, are urgently needed.
We investigate the potential of carbonyl sulfide (COS) for being used as a tracer for canopy net photosynthesis, transpiration and stomatal conductance by examining the theoretical basis of the link between leaf COS, carbon dioxide (CO2) and water vapour (H2O) exchange. Our analysis identifies several limitations that need to be overcome to this end, however at present we lack appropriate ecosystem-scale field measurements for assessing their practical significance. It however appears that COS represents a better tracer for CO2 than H2O. Concurrent measurements of ecosystem scale COS, CO2 and H2O exchange are advocated.
Unter dem Namen #climonomics – EU-Klimakonferenz für Schüler*innen: A Friday for Future veranstaltete das PolECulE-Projekt, ein Kooperationsprojekt der Englisch- und Politikdidaktik, am 25. Oktober eine Veranstaltung für Schüler*innen. Hier wurde die aktuelle EU-Klimapolitik im Rahmen eines Rollenspiels erörtert und debattiert. Nachdem die Hessenschau, FAZ, der Deutschlandfunk und die Frankfurter Rundschau ausgiebig über das Projekt berichteten, schreibt auch Charlotte Wittich (17), angehende Abiturientin am Heinrich-von-Gagern-Gymnasium, von ihren Erfahrungen.
The Arctic Svalbard Archipelago hosts the world’s northernmost cold-water ‘carbonate factories’ thriving here despite of presumably unfavourable environmental conditions and extreme seasonality. Two contrasting sites of intense biogenic carbonate production, the rhodolith beds in Mosselbukta in the north of the archipelago and the barnacle-mollusc dominated carbonate sediments accumulating in the strong hydrodynamic regime of the Bjørnøy-Banken south of Spitsbergen, were the targets of the RV Maria S. Merian cruise 55 in June 2016. By integrating data from physical oceanography, marine biology, and marine geology, the present contribution characterises the environmental setting and biosedimentary dynamics of these two polar carbonate factories. Repetitive CTD profiling in concert with autonomous temperature/salinity loggers on a long-term settlement platform identified spatiotemporal patterns in the involved Atlantic and Polar water masses, whereas short-term deployments of a lander revealed fluctuations of environmental variables in the rhodolith beds in Mosselbukta and at same depth (46 m) at Bjørnøy-Banken. At both sites, dissolved inorganic nutrients in the water column were found depleted (except for elevated ammonium concentrations) and show an overall increase in concentration and N:P ratios toward deeper waters. This indicates that a recycling system was fuelling primary production after the phytoplankton spring bloom at the time of sampling in June 2016. Accordingly, oxygen levels were found elevated and carbon dioxide concentrations (pCO2) markedly reduced, on average only half the expected equilibrium values. Backed up by seawater stable carbon and oxygen isotope signatures, this is interpreted as an effect of limited air-sea gas exchange during seasonal ice cover in combination with a boost in community photosynthesis during the spring phytoplankton bloom. The observed trends are enhanced by the onset of rhodophyte photosynthesis in the rhodolith beds during the polar day upon retreat of sea-ice. Potential adverse effects of ocean acidification on the local calcifier community are thus predicted to be seasonally buffered by the marked drop in pCO2 during the phase of sea-ice cover and spring phyto-plankton bloom, but this effect will diminish should the seasonal sea-ice formation continue to decline. Among the 25 macrobenthos taxa identified from images captured by the lander’s camera system, all but three species were calcifiers contributing to the carbonate production. Biodiversity was found to be much higher in Mosselbukta (21 taxa) compared to Bjørnøy-Banken (8 taxa), which is considered as a result of enhanced habitat diversity provided in the rhodolith beds by the bioengineering crustose alga Lithothamnion glaciale. Filter-feeding activity of selected key species did reveal group-specific but no common activity patterns. Biotic disturbance of the filtering activity was common, in contrast to abiotic factors, with hermit crabs representing the primary trigger. Motion tracking of rhodoliths revealed a high frequency of dislocation, triggered not by abiotic factors but by the activity of benthic invertebrates, in particular echinoids ploughing below or moving over the rhodoliths. The echinoid Strongylocentrotus sp. is the most abundant component of the associated fauna, thereby considerably contributing both to carbonate production and to grazing bioerosion. Together, these results portray a high degree of seasonal as well as short-term dynamics in environmental conditions that despite many similarities support distinctly different communities and biodiversity patterns in the calcifying macrobenthos at the two studied polar carbonate factories.
Samples of freshly fallen snow were collected at the high alpine research station Jungfraujoch (Switzerland) in February and March 2006 and 2007, during the Cloud and Aerosol Characterization Experiments (CLACE) 5 and 6. In this study a new technique has been developed and demonstrated for the measurement of organic acids in fresh snow. The melted snow samples were subjected to solid phase extraction and resulting solutions analysed for organic acids by HPLC-MS-TOF using negative electrospray ionization. A series of linear dicarboxylic acids from C5 to C13 and phthalic acid, were identified and quantified. In several samples the biogenic acid pinonic acid was also observed. In fresh snow the median concentration of the most abundant acid, adipic acid, was 0.69 micro g L -1 in 2006 and 0.70 micro g L -1 in 2007. Glutaric acid was the second most abundant dicarboxylic acid found with median values of 0.46 micro g L -1 in 2006 and 0.61 micro g L -1 in 2007, while the aromatic acid phthalic acid showed a median concentration of 0.34 micro g L -1 in 2006 and 0.45 micro g L -1 in 2007. The concentrations in the samples from various snowfall events varied significantly, and were found to be dependent on the back trajectory of the air mass arriving at Jungfraujoch. Air masses of marine origin showed the lowest concentrations of acids whereas the highest concentrations were measured when the air mass was strongly influenced by boundary layer air.