In the Earth, the dynamo action is strongly linked to core freezing. There is a solid inner core, the growth of which provides a buoyancy flux that drives the dynamo. The buoyancy in this case derives from a difference in composition between the solid inner core and the fluid outer core. In planetary bodies smaller than the Earth, however, this core differentiation process may differ - Fe may precipitate at the core-mantle boundary (CMB) rather than in the center and may fall as iron snow and initially remelt with greater depth. A chemical stable sedimentation zone develops that comprises with time the entire core - at that time a solid inner core starts to grow. The dynamics of this system is not well understood and also whether it can generate a magnetic field or not. The Jovian moon Ganymede, which shows a present-day magnetic dipole field, is a candidate for which such a scenario has been suggested. We plan to study this Fe-snow regime with both a numerical and experimental approach. In the numerical study, we use a 2D/3D thermo-chemical convection model that considers crystallization and sinking of iron crystals together with the dynamics of the liquid core phase (for the 3D case the influence of the rotation of the Fe snow process is further studied).The numerical calculations will be complemented by two series of experiments: (1) investigations in metal alloys by means of X-ray radioscopy, and (2) measurements in transparent analogues by optical techniques. The experiments will examine typical features of the iron snow regime. On the one hand they will serve as a tool to validate the numerical approach and on the other hand they will yield important insight into sub-processes of the iron snow regime, which cannot be accessed within the numerical approach due to their complexity.
The study investigates the chemical and physical characteristics of porewater and soil samples from peatlands across 64 sites in Germany, Poland, Estonia, Scotland, Sweden, and Georgia sampled between 1997 and 2017. The sites covers oceanic (Cfb, Cfc) and continental (Dfb, Dfc) climate zones and include both minerotrophic fens and ombrotrophic bogs. Fens were further classified into poor and rich types based on acidity and floristic composition, with rich fens characterized by higher pH and calcium concentrations due to mineral-rich groundwater inputs. The study also distinguishes between natural sites with stable near-surface water tables and rewetted sites previously subjected to drainage and agricultural use.
The hydrochemical and stable isotope composition of fresh surface water in rivers (Sieber and Oder) of a karst area in the southwestern foreland of the Harz Mountains, Germany, was investigated at several occasions between years 1986 and 1992. The campaigns covered different seasonal and hydrological (discharge) conditions, including a snow-melt induced high water at the rivers. Aim of the study was the investigation of the impact of discharge conditions at the river water loosing water to underground passage in the Basin of Pöhlde, dissolving carbonate and sulfate minerals in the karst aquifers, and reappearing in the karst springs of the Rhume river. Besides physical characterization, hydrochemical major and minor elements were measaured, as weill as the carbon isotope composition of DIC, the sulfur and oxygen isotope composition of sulfate, and the oxygen isotope composition of water. Results reflect the impact of hydrological conditions on the subterrestrial carbon and sulfur cycles.
Im Rahmen des Projekts STABLE soll die Sanierung eines Mehrfamilienhauses (MFH) wissenschaftlich begleitet werden, wobei eine sozialgerechte Klimaneutralität oberste Prämisse ist. Das Projektkonsortium bringt die notwendigen Expert:innen aus Wissenschaft und Praxis an einen Tisch und schafft somit einen Verfahrensrahmen für die gesellschaftlich akzeptierte Energiewende im Gebäudebereich. Die Untersuchung aller relevanten Akteur:innen stellt sicher, dass die Transformation im Sinne der Gesellschaft stattfindet, was den langfristigen Erfolg des Konzepts sichert. Das Projekt umfasst sowohl die Konzeptionierung eines klimaneutralen Energiesystems für ein existierendes MFH als auch dessen Umsetzung und nachträgliche Begleitung. Damit ermöglicht das Projekt die ganzheitliche Untersuchung des Energiesystems auf der einen Seite und der relevanten Akteur:innen auf der anderen Seite. Für relevante Akteur:innen werden partizipative Methodiken angewandt, um die Energiewende für alle erlebbar zu machen, Bewohner:innen einzubinden und Interessenskonflikte sichtbar zu machen. Die Begleitung der Umsetzung garantiert, dass die zur sozialverträglichen Transformation des Gebäudebestandes existierenden Hürden erkannt sowie Lösungsstrategien entwickelt werden. Zudem wird durch den Dialog mit allen relevanten Akteur:innen angestrebt, dass ein Drehbuch die Erfahrungen aus den Beteiligungsprozessen und innovativen Partizipationsformaten für Sanierungsprojekte anderer Gebäudetypen übertragbar macht.
The rewetting of drained peatlands is a promising measure to mitigate carbon dioxide (CO2) emissions by preventing the further mineralization of the peat soil through aeration. While freshwater rewetted peatlands can be significant methane (CH4) sources in the short-term, in coastal ecosystems the input of sulfate-rich seawater could potentially mitigate these emissions. The purpose of the data collection was to examine whether the presence of sulfate, known as an alternative electron acceptor, can cause lower CH4 production and thus, emissions by favoring the growth of sulfate-reducers, which outcompete methanogens for substrate. We therefore investigated underlying variables such as the methane-cycling microbial community along with CH4 fluxes and set them in context with CO2 fluxes along a transect in a coastal peatland before and directly after rewetting. In this way, a conclusion about the short-term greenhouse gas mitigation potential of brackish water rewetting of coastal peatlands could be drawn. This data collection consists of six data sets, with direct comparisons before and after rewetting of CO2 and CH4 fluxes (Tab. 2) and associated microbial communities (Tab. 1) being the main data. Pore water geochemistry (Tab. 1 and 3) and surface water parameters (Tab. 4) were collected simultaneously to provide potential explanatory variables. The sampling of continuous water level (Tab. 5) within wells and atmospheric weather data (air and soil temperature, relative humidity, photosynthetic photon flux density; Tab. 6) from a weather station was done in addition. Measurements started in June/July/August 2019 after field installation was finalized and were conducted on the drained coastal fen "Polder Drammendorf" on the island of Rügen in North-East Germany. On 26th November 2019, the dike was opened and channeled in order to rewet the peatland with brackish water. Before, the dike separated the peatland from the adjacent bay "Kubitzer Bodden", which is part of a brackish lagoon system connected to the Baltic Sea. Therefore, the peatland was nearly completely flooded and now resembles a shallow lagoon with high fluctuating water levels. We measured along a humidity (pre-rewetting)/water level (post-rewetting) gradient (stations 0-8) towards and across the main North-South oriented drainage ditch, including four stations on the Eastern side of the ditch (1–4), two ditch stations (0, 5) and two stations (6, 7) on the Western side of the ditch. Station 8 was chosen as an additional station farther towards the adjacent bay on the Western side, but was only accessible before rewetting. CH4 and CO2 fluxes (stations 0-7) were calculated from online gas concentrations measurements using laser-based analyzers and manual closed chambers (Livingston, G. P., & Hutchinson, G. (1995). Enclosure-based measurement of trace gas exchange: Applications and sources of error. In P.A. Matson, & R.C. Harriss (Eds.). Biogenic trace gases: Measuring emissions from soil and water (pp. 14–51). Blackwell Science Ltd., Oxford, UK). Soil cores for microbial, dissolved gas concentrations and isotopic analysis were taken using a Russian type peat corer (De Vleeschouwer, F., Chambers, F. M., & Swindles, G. T. (2010). Coring and sub-sampling of peatlands for palaeoenvironmental research. Mires and Peat, 7, 1–10) before and after rewetting. Each time, we took duplicates at stations 1-8 for this rather labor-intensive process and divided the core into four depth sections: surface, 5–20, 20–40 and 40–50 cm. Subsamples for dissolved gases and stable carbon isotope analyses were taken with tip-cut syringes with a distinct volume of 3 ml (Omnifix, Braun, Bad Arolsen, Germany) and immediately placed into NaCl-saturated vials (20 ml, Agilent Technologies, 5182-0837, Santa Clara, USA) leaving no headspace and closed gas-tight using rubber stoppers and metal crimpers (both: diameter 20 mm, Glasgerätebau Ochs, Bovenden, Germany). Absolute abundances of specific functional target genes, including methane- and sulfate-cycling microorganisms, were measured with quantitative PCR (qPCR) after DNA was extracted (GeneMATRIX Soil DNA Purification Kit, Roboklon, Berlin, Germany) and quantified (Qubit 2.0 Fluorometer, ThermoFisher Scientific, Darmstadt, Germany). Surface and pore water parameters were measured in parallel to the gas measurements and soil coring for microbial analyses. Most surface water variables (pH, specific conductivity, salinity, nutrients, oxygen, sulfate and chloride concentrations, DOC/DIC) were measured in-situ using a multiparameter digital water quality meter or taken to the laboratory as water samples for further analysis. Likewise, pore water/soil variables (pH, specific conductivity, nutrients, metals, sulfate and chloride concentrations, CNS) were either measured in-situ or taken to the laboratory as soil samples. While surface water analysis was only conducted in the drainage ditch before rewetting, it was done along the entire transect after rewetting. In contrast, pore water/soil analysis was mostly conducted before rewetting and only repeated occasionally after rewetting where possible.
Urbanization affects ecological communities but urban ecology has mostly focused on large and charismatic species. Water-filled tree holes and other ephemeral small standing waters in cities constitute unique but inconspicuous breeding habitats for a range of insects. Their biodiversity is not well known and how their communities respond to increased urbanization in particular, has rarely been studied. Using a Citizen Science Project, we investigated how urbanization (measured as imperviousness, human population density and altered temperature), additional environmental parameters (pH, electric conductivity) and detritus serving as a food source affected larval insect communities in artificial aquatic microhabitats. We found that these habitats were colonized quickly by a range of insect taxa. Their community abundance, richness and decomposition rates were largely stable across different levels of urbanization. Fine detritus content increased larval abundance. Community composition shifted strongly with urbanization. The most abundant and frequent species in our study, the exotic mosquito species Aedes japonicus, responded negatively to imperviousness. Aquatic microhabitats could be shown to be important habitats for aquatic insects in cities. However, their community composition may change with increased urbanization. As our results showed, exotic species such as mosquitoes may dominate the communities in these habitats. In the case of vector species, high abundances may affect human and animal health via increased pathogen transmission. Therefore, we suggest raising awareness about potential risks of these habitats and possible measures preventing the establishment and spread of harmful species, while still supporting native biodiversity in urban spaces.
The data set contains the results for the porewater composition of samples, collected from different (up to 11) depths (down to 4.5 mbsf) at two sites in front of the Hütelmoor, southern Baltic Sea. Porewater was under impact by submarine groundwater discharge and collected during 6 field campaigns in years 2020 and 2021 using permanent multi-port samplers. Stable isotope signatures (H, C, O, S), major, and trace element data are presented to characterize the mixture between the endmembers freshwater and the brackish surface water component, superimposed by benthic diagenesis.
This dataset contains data from the RV Heincke cruise HE582 to the German Bight of the North Sea in late summer 2021. The aim of the research was to investigate the source of sedimentary glycan concentrations in subtidal sandy sediments. Glycans represent a substantial fraction of extracellular polymeric substances and may affect flow dynamics in marine sandy sediments. The origin and concentration of glycans in sands remain understudied until today. To gain insights into oxygen supply and glycan concentrations in sandy sediment, we conducted in situ measurements and sampled sediment via a van Veen grab for ex situ investigations. Oxygen penetration depths were determined by a benthic lander, which was deployed for ca. 24h at each station. Chlorophyll a concentrations as an indicator for potentially photosynthetically active sedimentary biomass were derived via extraction with 90% acetone against Sigma Aldrich standards. Glycan concentrations served as indicator for extracellular polymeric substances and were quantified against a glucose standard curve via a phenol sulfuric acid assay after prior sequential glycan extraction (MilliQ, EDTA, NaOH). The final glycan concentrations are referred to per volume of porespace, and therefore given in mmol/l porewater. To investigate if benthic primary producers could be responsible for the extracted sedimentary glycan concentrations, we conducted stable isotope incubations.
The dataset contains multi-proxy-analyses (element geochemistry, stable Pb isotopes, humification index, ash content) of a 500-cm-long, 14C dated peat core covering the past ~5000 years from the ombrotrophic Pürgschachen Moor in the Styrian Enns Valley (Austrian Alps).
Recent and predicted increases in extremely dry and hot summers emphasise the need for silvicultural approaches to increase the drought tolerance of existing forests in the short-term, before adaptation through species changes may be possible. We aim to investigate whether resistance during droughts, as well as the recovery following drought events (resilience), can be increased by allocating more growing space to individual trees through thinning. Thinning increases access of promoted trees to soil stored water, as long as this is available. However, these trees may also be disadvantaged through a higher transpirational surface, or the increased neighbourhood competition by ground vegetation. To assess whether trees with different growing space differ in drought tolerance, tree discs and cores from thinning experiments of Pinus sylvestris and Pseudotsuga menziesii stands will be used to examine transpirational stress and growth reduction during previous droughts as well as their subsequent recovery. Dendroecology and stable isotopes of carbon and oxygen in tree-rings will be used to quantify how assimilation rate and stomatal conductance were altered through thinning. The results will provide crucial information for the development of short-term silvicultural adaptation strategies to adapt forest ecosystems to climate change. In addition, this study will improve our understanding of the relationship between resistance and resilience of trees in relation to extreme stress events.
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