Advances in modelling hydrological dynamics in drained and cultivated peatlands

Process-modelling of hydrological dynamics in drained and cultivated fen soil profiles is essential for a precise calculation of greenhouse gas emissions. Until now, several estimation procedures exist, basically depending on site-specific conditions like land-use, vegetation, water table and fen soil type. To some extent these approaches are vulnerable to under- and overestimation of local greenhouse gas emissions by neglecting heterogeneous properties along fen soil profiles potentially differing from horizon to horizon. Hydrological modelling of water dynamics in fen soils characterised by progressed moorsh-forming process is restricted due to a lack of valid parameters describing available water retention functions. In the present study, a general applicable parameter set to solve the van Genuchten-Mualem water retention equation for fen soil horizons formed by drainage and cultivation has been developed based on a comprehensive dataset consisting of 520 horizontal data from fen soil profiles sampled at altogether 15 peatland areas in Germany. Different categorizations of the data were proofed to account for various states of peat decomposition and to reduce the range of measured volumetric soil water contents at specific pressure heads. Finally, bulk density was used as a cluster variable to consider the intensity of moorsh-forming process within every horizon category. Subsequent parameter estimation was conducted by the RETC programme and validation of the estimated parameters was realized for in total four monitoring plots varying in land-use type, climate and fen soil profile, by modelling water dynamics using HYDRUS-1d

Heißwasserextrahierbarer Kohlenstoff und Bodenatmung als Parameter zur Abschätzung der potentiellen Kohlenstofffreisetzung aus organischen Böden

Durch Ihre hohen Gehalte an Kohlenstoff (C) und organischer Bodensubstanz (OBS) und besitzen Moorböden eine herausragende Rolle im globalen Kohlenstoffkreislauf. Bei unsachgemäßer Nutzung setzen diese organischen Böden besonders hohe Mengen an C, z.B in Form von CO2 frei. Der labile und aktive Anteil der OBS, der potentiell besonders leicht freigesetzt werden kann, lässt sich allgemein mit dem Parameter heißwasserextrahierbarer Kohlenstoff (Chwe) abschätzen, da diese Fraktion große Mengen leicht umsetzbarer Bestandteile wie etwa hohe Anteile an mikrobieller Biomasse, Einfachzucker oder Ligninmonomere enthält. Bis jetzt ist aber unklar, wie gut sich dieser Parameter zur Ableitung der potentiellen C-Freisetzung aus Moorböden eignet. Für verschiedene Mineralböden konnten bereits enge Korrelationen zwischen dem Chwe und der jeweiligen Bodentamung aufgezeigt werden. Studien zur Beziehung der CO2-Freisetzung und dem Parameter Chwe speziell für organische Böden fehlen bisher. Ziel der vorliegenden Untersuchung war es deshalb, diese möglichen Korrelationen für organische Böden zu untersuchen. Dazu wurde der Chwe an über 50 unterschiedlichen Moorbodensubstraten ermittelt. Hier wurde eine Extraktionsmethode angewandt, welche speziell an die hohen Anteile an OBS angepasst wurde. Daneben wurde die jeweilige Bodenatmung mittels Inkubationsversuchen im Labor gemessen und mit dem Gehalt an Chwe verglichen. Die bisherigen Ergebnisse zeigen mittlere bis hohe Korrelationen zwischen der Bodenatmung und dem Chwe, so dass davon auszugehen ist, dass der Chwe zur Abschätzung einer potentiellen C-Freisetzung auch für organische Böden herangezogen werden kann, um damit die Empfindlichkeit gegenüber Kohlenstoffverlusten beschreiben zu können. Die gewonnenen Daten sollten allerdings durch zusätzliche Untersuchungen, vor allem an bisher nicht genügend berücksichtigten Moorbodensubstraten, weiter überprüft werden

Physical and hydrological properties of peat as proxies for degradation of South African peatlands: Implications for conservation and restoration

The physical and hydrological properties of peat from seven peatlands in northern Maputaland (South Africa) were investigated and related to the degradation processes of peatlands in different hydrogeomorphic settings. The selected peatlands are representative of typical hydrogeomorphic settings and different stages of human modification from natural to severely degraded. Nineteen transects (141 soil corings in total) were examined in order to describe peat properties typical of the distinct hydrogeomorphic settings. We studied degree of decomposition, organic matter content, bulk density, water retention, saturated hydraulic conductivity and hydrophobicity of the peats. From these properties we derived pore size distribution, unsaturated hydraulic conductivity and maximum capillary rise. We found that, after drainage, degradation advances faster in peatlands containing wood peat than in peatlands containing radicell peat. Eucalyptus plantations in catchment areas are especially threatening to peatlands in seeps, interdune depressions and unchannelled valley bottoms. All peatlands and their recharge areas require wise management, especially valley-bottom peatlands with swamp forest vegetation. Blocking drainage ditches is indispensable as a first step towards achieving the restoration of drained peatland areas, and further measures may be necessary to enhance the distribution of water. The sensitive swamp forest ecosystems should be given conservation priority

Heterogeneous integration of contact-printed semiconductor nanowires for high-performance devices on large areas

In this work, we have developed a contact-printing system to efficiently transfer the bottom-up and top-down semiconductor nanowires (NWs), preserving their as-grown features with a good control over their electronic properties. In the close-loop configuration, the printing system is controlled with parameters such as contact pressure and sliding speed/stroke. Combined with the dry pre-treatment of the receiver substrate, the system prints electronic layers with high NW density (7 NWs/μm for bottom-up ZnO and 3 NWs/μm for top-down Si NWs), NW transfer yield and reproducibility. We observed compactly packed (~115 nm average diameters of NWs, with NW-to-NW spacing ~165 nm) and well-aligned NWs (90% with respect to the printing direction). We have theoretically and experimentally analysed the role of contact force on NW print dynamics to investigate the heterogeneous integration of ZnO and Si NWs over pre-selected areas. Moreover, the contact-printing system was used to fabricate ZnO and Si NW-based ultraviolet (UV) photodetectors (PDs) with Wheatstone bridge (WB) configuration on rigid and flexible substrates. The UV PDs based on the printed ensemble of NWs demonstrate high efficiency, a high photocurrent to dark current ratio (>104) and reduced thermal variations as a result of inherent self-compensation of WB arrangement. Due to statistically lesser dimensional variations in the ensemble of NWs, the UV PDs made from them have exhibited uniform response

Immunological and antitumor effects of coumarin and some derivatives

Coumarin and its 4-OH and 7-OH derivatives, as well as o-, m- and p-coumaric acid were tested against P-815 and P-388 tumor cells in vitro. In addition, the compounds were investigated in various in vitro immunological test systems and genuine coumarin was tested furthermore against the Sarcoma-180 in CD1 mice. In vivo, coumarin showed only a moderate antitumor effect against the allogeneic Sarcoma-180 at concentrations of 10 and 40 mg/kg, with inhibition rates of 49 and 60%, respectively. However, both concentrations were markedly toxic. In vitro all compounds were more or less cytotoxic against P-815 and P-388 tumor cell lines starting at a concentration of 100 micrograms/ml. At subtoxic concentrations (less than or equal to 10 micrograms/ml) the samples showed no mitogenic activity against murine spleen lymphocytes and PHA costimulated human peripheral blood lymphocytes. Furthermore, with the coumarin derivatives neither cytotoxic macrophages could be induced against P-815 tumor cells nor an increased release of Il-2 and TNF-alpha could be observed. Only 7-OH coumarin, in concentrations of 2 and 20 micrograms/ml, caused a strong increase in phagocytosis of 124 and 84% in both, human peripheral blood granulocytes and murine peritoneal macrophages, respectively

Impact of the spatial resolution of soils data on climate reporting for organic soils using the example of Germany

As a result of the climate conferences in Durban (2011) and Doha (2012), voluntary accounting for greenhouse gas emissions from organic soils is now possible in national climate reporting. The quality of the data describing the spatial extent of organic soils and their relevant soil properties thus becomes particularly important. For climate reporting issues, maps for organic soils at different scales and levels of detail are used. In Germany, for example, the soil map at scale 1:1,000,000 is the basis for the emission inventory (NIR 2013). In contrast, the national inventory report of The Netherlands is based on a soil map at scale 1:50,000 (Coenen et al. 2013). This leads to questions about the optimal level of detail or scale for climate reporting. Datasets with scales ranging from 1:25,000 up to 1:1,000,000 were used to derive the spatial distribution of organic soils in two characteristic areas of the temperate zone, one in northern and one in southern Germany. Comparison of the results shows large differences in both areal and spatial accuracy, depending on the origin and quality of the data as well as on scale and landscape characteristics. In southern Germany, for example, only 50 % of the organic soils derived from smaller-scale maps can be verified by detailed data, in contrast to more than 70 % in northern Germany. In combination with the partially poor spatial accuracy, these differences have a strong impact on the calculation of greenhouse gas emissions from organic soils, leading to errors of more than 60 %. As a result, for the temperate zone we recommend a minimum scale of 1:200,000 for maps of organic soils. However, in mountainous regions with higher geomorphic heterogeneity, more detailed data may be necessary

Untersuchung und Optimierung von Fließ- und Durchströmungsverhalten von Schüttungen zur thermochemischen Wärmespeicherung

Am Institut für Technische Thermodynamik des DLR in Stuttgart werden neuartige Wärmespeicherkonzepte auf Basis von reversiblen Gas-Feststoff-Reaktionen untersucht und entwickelt. Ein geeignetes Reaktionssystem für den Hochtemperaturbereich stellt dabei die Reaktion von Calciumoxid (CaO) mit Wasserdampf (H2O) zu Calciumhydroxid (Ca(OH)2) dar. Anwendungsbedingt ist es notwendig, das feinkörnige Reaktionsmaterial zu optimieren, um trotz des kohäsiven Charakters der Schüttung eine Förderung durch schmale Reaktorgeometrien zu ermöglichen. Aufgrund der reaktionsbedingten Volumenänderung der Partikeln ist ein Pelletieren nicht möglich. Daher wird im Rahmen dieses Beitrags die Minimierung der Van-der-Waals Kräfte durch das Einbringen von Nanopartikeln untersucht. In der Schüttguttechnik ist das Prinzip der Erhöhung der Oberflächenrauhigkeit von Partikeln durch Einbringung von Nanopartikeln bekannt [1]. Für die thermochemische Wärmespeicherung stellen sich jedoch besondere Herausforderungen aufgrund der hohen Temperaturen (~500°C), der anorganische Materialien sowie der Volumen- und Oberflächenänderung des Materials während der chemischen Reaktion. Es wird ein Verfahren vorgestellt, welches unter den genannten Bedingungen eine Bewegung des Reaktionsbetts durch Verbesserung der Fließfähigkeit und Vermeidung der Agglomeration ermöglicht. Darüber hinaus werden die Ergebnisse im Kontext der Entwicklung zukünftiger kostengünstiger Wärmespeicher diskutiert