TY - JOUR A1 - Klaver, Martijn A1 - Steenstra, Edgar S. A1 - Borchert, Manuela A1 - Welter, Edmund A1 - Wilke, Max A1 - Berndt, Jasper A1 - Klemme, Stephan T1 - The effect of alkalinity on Ni-O bond length in silicate glasses BT - implications for Ni isotope geochemistry JF - Chemical geology : official journal of the European Association for Geochemistry N2 - Equilibrium mass-dependent ("stable") isotopic fractionation of an element during magmatic processes is driven by a contrast in bonding environment between minerals and silicate melt, which is expressed as an isotopic fractionation factor. A quantitative understanding of such isotopic fractionation factors is vital to interpret observed isotopic variations in magmatic rocks. It is well known that the local environment and the bond strength of an element dictate the sign and magnitude of isotopic fractionation between minerals, but it is uncertain how the structure and chemical composition of a silicate melt can affect mineral-melt isotopic fractionation factors. To explore this, we studied the coordination environment of nickel (Ni) in different silicate glasses using extended X-ray absorption fine structure (EXAFS) measurements at the German synchrotron X-ray source (DESY). We determined -Ni-O bond lengths in a suite of synthetic but near-natural silicate glasses using EXAFS and found that the former vary systematically with melt alkalinity, which is best described by the parameter ln[1 + (Na + K)/Ca]. With increasing melt alkalinity, Ni occupies more IV-fold coordinated sites, which are associated with a shorter -Ni-O bond length. Next, we use the ionic model, which allows to predict isotopic fractionation factors based on the difference in bond length between two phases. We find that more alkaline melts have a stronger preference for the heavier isotopes of Ni than less alkaline melts. This implies that the magnitude of mineral-melt Ni isotope fractionation factors, for instance between olivine and melt, will depend on the alkalinity of the melt. At magmatic temperatures, however, the variation in fractionation factors caused by melt alkalinity will rarely exceed 0.05 parts per thousand and is thus mostly negligible, in particular in the realm of basaltic melt compositions. Nevertheless, the relationship between melt alkalinity and fractionation factor reported here can be used to extrapolate empirical data for mineral-melt Ni isotope fractionation factors, once such data become available, to the full range of magma compositions on Earth and other Solar System bodies. KW - EXAFS KW - Ni-O bond length KW - silicate glasses KW - Ni isotopes KW - isotopic fractionation factors Y1 - 2022 U6 - https://doi.org/10.1016/j.chemgeo.2022.121070 SN - 0009-2541 SN - 1872-6836 VL - 610 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Regenspurg, Simona A1 - Virchow, Lioba A1 - Wilke, Franziska D. H. A1 - Zimmer, Martin A1 - Jolie, Egbert A1 - Hachenberger, Annika A1 - Yirgu, Gezahegn A1 - Gebru, Ermias Filfilu A1 - Vieth-Hillebrand, Andrea A1 - Gizaw, Berhanu T1 - Origin and migration of fluoride in the area of the Aluto Volcanic Complex (Main Ethiopian Rift) JF - Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry N2 - Fluoride-enriched ground and surface waters represent a major health risk for the local population in many areas along the East African Rift. The present study investigates the origin of fluoride and the reason for its accumulation in the rift waters, following two hypotheses: (i) fluid-rock-interactions release fluoride from minerals into the water and (ii) magmatic-derived fluoride-containing liquids and gases migrate along permeable fault zones until they dissolve in ground-and surface water or be released to the atmosphere. Rock-, gas, water-, soil-, and plant samples were collected from the area within and close by the Aluto Volcanic Complex, which is part of the Main Ethiopian Rift. Most analyzed waters showed fluoride concentrations above the drinking water limit (> 1.5 mg/L) with the highest values in hot springs (up to 70 mg/L) and the geothermal well (76 mg/L). In the solid phase, a high fluoride content was found in acid volcanic rocks (ignimbrite: 4391 ppm; rhyolite: 3248 ppm) as well as in pumice (up to 1955 ppm). The fluoride content of soil samples collected within the volcanic complex varied between 82 and 1036 ppm, whereas former lake sediments from outside the Aluto Volcanic Complex showed higher fluoride contents ranging from 674 to 8171 ppm. Identified fluoride-rich minerals are various amphiboles (about 3 wt.-% F-), fluor-apatite (about 3 wt % F-), minerals of the fluorcaphite group (about 5 wt.-% F-), parisite (up to 9 wt.-% F-), and fluorite (CaF2). Elevated fluoride concentrations were also measured in some gas samples from fumaroles (up to 50 ppm) and in plant samples collected next to the fumaroles (up to 65 ppm). Leaching experiments of solid samples with deionized water demonstrated that fluoride can easily be mobilized from pumice and sediments but hardly from consolidated rocks. This fluoride release increased with temperature (up to 150 C) and correlated roughly with dis-solved silica indicating the binding of some fluoride to the amorphous or weakly crystalline silica fraction. Based on these results it was concluded that fluoride migrates via different pathways through the environment: At the depth of the magma chamber during magmatic differentiation fluoride enriches initially in the magmatic melt and accumulates in some late-crystallizing minerals of igneous rocks such as fluorite or mica. Upon volcanic eruption fluoride is predominantly incorporated in the glass (ignimbrite) and ash phase (pumice). On the surface, these rocks are exposed to weathering and fluoride leaches partly out into the aqueous phase. Soft and porous rocks such as pumice release fluoride first whereas hard extrusive/igneous rocks are less prone to weathering and retain the fluoride. Pumice and (lake) sediments might act both, as source and as sink for fluoride in the area. Although some fluoride might drain from the surface into the deeper subsoil, we conclude that magmatic fluids (liquid and gas) contribute more substantially to the overall fluoride ground water content because (i) of the much higher fluoride content in deep geothermal waters and hot springs as compared to surface-near waters; (ii) active geothermal surface manifestations located along fault zones indicate that fluids migrate from deep magmatic intrusions (as gas and liquid) towards the surface, where fluoride dissolves in groundwater; (iii) and the good correlation between bicarbonate (deriving from dissolution of magmatic CO2) and fluoride content in all analyzed water samples. KW - fluoride KW - environmental contaminant main Ethiopian rift KW - volcanic area KW - Aluto volcanic complex KW - volcanic gases KW - pumice Y1 - 2022 U6 - https://doi.org/10.1016/j.apgeochem.2022.105403 SN - 0883-2927 SN - 1872-9134 VL - 146 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Van der Looven, Thomas A1 - Winterleitner, Gerd A1 - Betzler, Christian A1 - Mutti, Maria T1 - A biotic perspective on the Oligo-Miocene evolution of the Maldives carbonate platform from forward stratigraphic modelling (Indian Ocean) JF - Marine and petroleum geology N2 - Forward stratigraphic modelling is a fast-developing modelling approach, used to test conceptual models, and predict stratigraphic architecture and depositional facies from basin to reservoir scales. Published subsurface applications demonstrate its added value by integrating multidisciplinary data as well as geological concepts into its constraints. When applied to carbonate depositional systems, composed of multiple sediment factories, the cooperating and interdependent production mechanisms remain poorly studied. By applying the technique to a well-studied section of the Maldives carbonate platform, a specific model design-adapted to the geological age and setting, and constrained by available data-sheds light on the interaction of its carbonate producers. The results yield a naturalistic depositional facies distribution and offer insight in the changing relationship between biotic communities during the platform evolution. After calibration, the reference model unequivocally links the formerly proposed genetic model to the seismostratigraphic architecture. Furthermore, the results show how environmental changes (seemingly of secondary impact compared to changes in physical accommodation in the stratigraphic record) can induce substantial fluctuations in carbonate production rates of biotic communities, affect the ecological accommodation, and thus impact the platform architecture. Therefore, it is crucial to treat carbonate production rates during periods of environmental change as variables with associated uncertainties in a forward stratigraphic model setup. KW - neogene KW - Maldives carbonate platform KW - forward stratigraphic modelling KW - sequence stratigraphy KW - carbonate production Y1 - 2022 U6 - https://doi.org/10.1016/j.marpetgeo.2022.105907 SN - 0264-8172 SN - 1873-4073 VL - 145 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Singh, Manudeo A1 - Sinha, Rajiv T1 - Integrating hydrological connectivity in a process-response framework for restoration and monitoring prioritisation of floodplain wetlands in the Ramganga Basin, India JF - Water N2 - Floodplain wetlands are critical for sustaining various ecological and hydrological functions in a riverine environment. Severe anthropogenic alterations and human occupation of floodplains have threatened these wetlands in several parts of the world. A major handicap in designing sustainable restoration and monitoring strategies for these wetlands is the lack of scientific process-based understanding and information on the basin-scale controls of their degradation. Here, we offer a novel approach to integrate the connectivity of the wetlands with the surrounding landscape along with other attributes such as stream density, hydrometeorological parameters, and groundwater dynamics to explain their degradation and then to prioritise them for restoration and monitoring. We hypothesise that the best possible connectivity scenario for the existence of a wetland would be if (a) the wetland has a high connectivity with its upslope area, and (b) the wetland has a low connectivity with its downslope region. The first condition ensures the flow of water into the wetland and the second condition allows longer water residence time in the wetland. Accordingly, we define four connectivity-based wetland health scenarios-good, no impact, bad, and worst. We have implemented the proposed method in 3226 wetlands in the Ramganga Basin in north India. Further, we have applied specific selection criteria, such as distance from the nearest stream and stream density, to prioritise the wetlands for restoration and monitoring. We conclude that the connectivity analysis offers a quick process-based assessment of wetlands' health status and serves as an important criterion to prioritise the wetlands for developing appropriate management strategies. KW - floodplain protection KW - ganga plains KW - hydrological connectivity KW - wetland health KW - wetland management Y1 - 2022 U6 - https://doi.org/10.3390/w14213520 SN - 2073-4441 VL - 14 IS - 21 PB - MDPI CY - Basel ER - TY - JOUR A1 - Loh, Yvonne Sena Akosua A1 - Fynn, Obed Fiifi A1 - Manu, Evans A1 - Afrifa, George Yamoah A1 - Addai, Millicent Obeng A1 - Akurugu, Bismark Awinbire A1 - Yidana, Sandow Mark T1 - Groundwater-surface water interactions BT - application of hydrochemical and stable isotope tracers to the lake bosumtwi area in Ghana JF - Environmental earth sciences N2 - This research demonstrated the application of hydrochemical data and stable water isotopes of delta O-18 and delta D (or delta 2H) for evaluating the relationship between surface water in Lake Bosumtwi and the underlying groundwater system. It aimed at determining the presence or absence of a hydraulic relationship and for evaluating the possible direction of flow at the interface between the two reservoirs. The study also estimated evaporative losses of infiltrating rainwater as it transits the unsaturated zone and provided important information on the hydrological processes prevailing in the area. The results of Q-Mode hierarchical cluster analysis (HCA) clearly differentiate the lake water from the groundwater based on their spatial relationship. These results indicated that groundwater recharge occurs on the hilltops of the crater, where it is slightly acidic with low levels of dissolved ions, characterised by short residence time and rapid unrestricted vertical infiltration and recharge. The groundwater becomes more mineralized with longer contact times and deeper circulation with the host rock, while it flows from the recharge areas towards the lake at lower elevations. Analyses of delta O-18 and delta D showed a high evaporation rate on the lake surface (90%) with a significant evaporative enrichment, whereas groundwater showed no significant isotopic variations. Thus suggesting that the aquifers have been recharged by recent meteoric water that has undergone some evaporative enrichment since the study established an evaporation rate of water infiltrating the unsaturated zone ranging from 54 to 60%. Both reservoirs do not appear to be hydraulically connected, and where such a connection exists, it is expected to favour the lake. KW - Lake Bosumtwi KW - stable isotopes KW - kinetic fractionation KW - surface water KW - groundwater KW - Ghana Y1 - 2022 U6 - https://doi.org/10.1007/s12665-022-10644-x SN - 1866-6280 SN - 1866-6299 VL - 81 IS - 22 PB - Springer CY - New York ER - TY - JOUR A1 - Lipus, Daniel A1 - Jia, Zeyu A1 - Bartholomäus, Alexander A1 - Burckhardt, Oliver A1 - Sondermann, Megan A1 - Wagner, Dirk A1 - Kallmeyer, Jens T1 - Circular metagenome-assembled genome of Methanobacterium sp. strain ERen5, a putative methanogenic, H2-utilizing terrestrial subsurface archaeon JF - Microbiology Resource Announcements N2 - A circular, single-contig Methanobacterium sp. metagenome-assembled genome (MAG) was recovered from high-CO2 enrichments inoculated with drill core material from the tectonic Eger Rift terrestrial subsurface. Annotation of the recovered MAG highlighted putative methanogenesis genes, providing valuable information on archaeal activity in the deep biosphere. Y1 - 2022 U6 - https://doi.org/10.1128/mra.00676-22 SN - 2576-098X VL - 11 IS - 10 PB - American Society for Microbiology CY - Washington ER - TY - JOUR A1 - Schifferle, Lukas A1 - Speziale, Sergio A1 - Lobanov, Sergey S. T1 - High-pressure evolution of the refractive index of MgO up to 140 GPa JF - Journal of applied physics N2 - Refractive index provides fundamental insights into the electronic structure of materials. At high pressure, however, the determination of refractive index and its wavelength dispersion is challenging, which limits our understanding of how physical properties of even simple materials, such as MgO, evolve with pressure. Here, we report on the measurement of room-temperature refractive index of MgO up to similar to 140 GPa. The refractive index of MgO at 600 nm decreases by similar to 2.4% from similar to 1.737 at 1 atm to similar to 1.696 (+/- 0.017) at similar to 140 GPa. Despite the index at 600 nm is essentially pressure independent, the absolute wavelength dispersion of the refractive index at 550-870 nm decreases by similar to 28% from similar to 0.015 at 1 atm to similar to 0.011 (+/- 8.04 x 10(-4)) at similar to 103 GPa. Single-effective-oscillator analysis of our refractive index data suggests that the bandgap of MgO increases by similar to 1.1 eV from 7.4 eV at 1 atm to similar to 8.5 (+/- 0.6) eV at similar to 103 GPa. Y1 - 2022 U6 - https://doi.org/10.1063/5.0106626 SN - 0021-8979 SN - 1089-7550 VL - 132 IS - 12 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Bartholomäus, Alexander A1 - Mitzscherling, Julia A1 - Lipus, Daniel A1 - MacLean, Joana A1 - Wagner, Dirk T1 - Draft genome sequence of Paenalcaligenes niemegkensis NGK35T, isolated from plastic-polluted soil of an abandoned landfill JF - Microbiology Resource Announcements N2 - The Gram-negative bacterium Paenalcaligenes niemegkensis NGK35(T) was isolated from plastic debris in an abandoned landfill. It has the ability to grow on polyethylene and hexadecane as the sole carbon sources. Here, we report the corresponding draft genome, which contains 3.66 Mbp and is characterized by a G+C content of 52.1%. Y1 - 2022 U6 - https://doi.org/10.1128/mra.00671-22 SN - 2576-098X VL - 11 IS - 10 PB - American Society for Microbiology CY - Washington ER - TY - JOUR A1 - Rikani, Albano A1 - Frieler, Katja A1 - Schewe, Jacob T1 - Climate change and international migration BT - exploring the macroeconomic channel JF - PLoS one N2 - International migration patterns, at the global level, can to a large extent be explained through economic factors in origin and destination countries. On the other hand, it has been shown that global climate change is likely to affect economic development over the coming decades. Here, we demonstrate how these future climate impacts on national income levels could alter the global migration landscape. Using an empirically calibrated global migration model, we investigate two separate mechanisms. The first is through destination-country income, which has been shown consistently to have a positive effect on immigration. As countries' income levels relative to each other are projected to change in the future both due to different rates of economic growth and due to different levels of climate change impacts, the relative distribution of immigration across destination countries also changes as a result, all else being equal. Second, emigration rates have been found to have a complex, inverted U-shaped dependence on origin-country income. Given the available migration flow data, it is unclear whether this dependence-found in spatio-temporal panel data-also pertains to changes in a given migration flow over time. If it does, then climate change will additionally affect migration patterns through origin countries' emigration rates, as the relative and absolute positions of countries on the migration "hump" change. We illustrate these different possibilities, and the corresponding effects of 3 degrees C global warming (above pre-industrial) on global migration patterns, using climate model projections and two different methods for estimating climate change effects on macroeconomic development. Y1 - 2022 U6 - https://doi.org/10.1371/journal.pone.0276764 SN - 1932-6203 VL - 17 IS - 11 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Dahm, Torsten A1 - Hainzl, Sebastian T1 - A Coulomb stress response model for time-dependent earthquake forecasts JF - Journal of geophysical research : Solid earth N2 - Seismicity models are probabilistic forecasts of earthquake rates to support seismic hazard assessment. Physics-based models allow extrapolating previously unsampled parameter ranges and enable conclusions on underlying tectonic or human-induced processes. The Coulomb Failure (CF) and the rate-and-state (RS) models are two widely used physics-based seismicity models both assuming pre-existing populations of faults responding to Coulomb stress changes. The CF model depends on the absolute Coulomb stress and assumes instantaneous triggering if stress exceeds a threshold, while the RS model only depends on stress changes. Both models can predict background earthquake rates and time-dependent stress effects, but the RS model with its three independent parameters can additionally explain delayed aftershock triggering. This study introduces a modified CF model where the instantaneous triggering is replaced by a mean time-to-failure depending on the absolute stress value. For the specific choice of an exponential dependence on stress and a stationary initial seismicity rate, we show that the model leads to identical results as the RS model and reproduces the Omori-Utsu relation for aftershock decays as well stress-shadowing effects. Thus, both CF and RS models can be seen as special cases of the new model. However, the new stress response model can also account for subcritical initial stress conditions and alternative functions of the mean time-to-failure depending on the problem and fracture mode. KW - seismicity KW - physics based model KW - earthquake physics Y1 - 2022 U6 - https://doi.org/10.1029/2022JB024443 SN - 2169-9313 SN - 2169-9356 VL - 127 IS - 9 PB - American Geophysical Union CY - Washington ER -