Recent Submissions

  • Journal Article

    Benefits and Constraints of the Agricultural Land Acquisition for Urbanization for Household Gender Equality in Affected Rural Communes: A Case Study in Huong Thuy Town, Thua Thien Hue Province, Vietnam 

    Pham Thi, Nhung; Kappas, Martin; Wyss, Daniel
    Land 2020; 9(8) p.1-19: Art. 249
    The Vietnamese Government has implemented agricultural land acquisition for urbanization (ALAFU) since 2010 which has caused a high level of social-economic transition in the country. In this paper, we applied the gender and development approach to discover how ALAFU has influenced the household gender equality in affected areas in Thua Thien Hue province, Vietnam. The data for this paper was mainly collected from two household group surveys, four group discussions, and six key informant interviews. Group 1 covers 50 affected households whose agricultural land was acquired for urbanization, while Group 2 consists of 50 households whose agricultural land was not taken away. The findings reveal that ALAFU has led to reduced access to agricultural land for group 1, but has contributed to an increase of economic status for women in both groups by creating non-farming job opportunities with a good income. However, most of their new jobs are still informal, contain potential risks, and the unpaid care work burden is heavy. Moreover, although the rate of women participating in household decision making has increased, the quality of participation is limited. Their participation in social activities and vocational training courses has improved insignificantly. Therefore, if the Government continues to promote ALAFU, they should take structural gender inequalities into account to achieve their sustainable development goals.
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  • Journal Article

    Designing the Next Generation of Fe$^0$-Based Filters for Decentralized Safe Drinking Water Treatment: A Conceptual Framework 

    Yang, Huichen; Hu, Rui; Ndé-Tchoupé, Arnaud Igor; Gwenzi, Willis; Ruppert, Hans; Noubactep, Chicgoua
    Processes 2020; 8(6) p.1-16: Art. 745
    The ambitious United Nations Sustainable Development Goal for 2030 to “leave no one behind” concerning safe drinking water calls for the development of universally applicable and affordable decentralized treatment systems to provide safe drinking water. Published results suggest that well-designed biological sand filters (BSFs) amended with metallic iron (Fe$^0$-BSFs) have the potential to achieve this goal. Fe$^0$-BSFs quantitatively remove pathogens and a myriad of chemical pollutants. The available data were achieved under various operating conditions. A comparison of independent research results is almost impossible, especially because the used Fe$^0$ materials are not characterized for their intrinsic reactivity. This communication summarizes the state-of-the-art knowledge on designing Fe$^0$-BSFs for households and small communities. The results show that significant research progress has been made on Fe$^0$-BSFs. However, well-designed laboratory and field experiments are required to improve the available knowledge in order to develop the next generation of adaptable and scalable designs of Fe$^0$-BSFs in only two years. Tools to alleviate the permeability loss, the preferential flow, and the use of exhausted filters are presented.
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  • Journal Article

    Quantifying forest cover at Mount Kenya: Use of Sentinel-2 for a discrimination of tropical tree composites 

    Jonas, Fierke; Martin, Kappas; Daniel, Wyss
    African Journal of Environmental Science and Technology 2020; 14(6) p.159-176
    The aim of the present study is totest ESA’s Sentinel-2 (S2) satellites (S2A and S2B) for an efficient quantification of land cover (LC) and forest compositions in a tropical environment southwest of Mount Kenya. Furthermore, outcome of the research is used to validate ESA’s S2 prototype LC 20m map of Africa that was produced in 2016. A decision tree that is based on significant altitudinal ranges was used to discriminatefour natural tree compositions that occur within the investigation area. In addition, the classification process was supported by Google Earthimages, and land use (LU) data that wereprovided by the local Kenyan Forest Service(KFS). Final classification products include four LC classes and five subclasses of forest (four natural forestsubclasses plus one non-natural forest class). Results of theJeffries-Matusita (JM) distance test show significant differences in spectral separability between all classes. Furthermore, the study identifies spectral signatures and significant wavelengths for a classification of all LC classes and forest subclasseswherewavelengths of SWIR and the red-edge domain show highestimportancefor the discrimination of tree compositions.Finally, considerable differences can be seen between the utilized multi-temporal classification set (total of 39 bands fromthree acquisition dates) and ESA’s S2 prototype LC 20m map of Africa 2016. A visual comparison of ESA’s prototypemapwithin the investigation area indicates an overrepresentation of tree cover areas (as confirmed in previous studies) andalso an underrepresentation of water.
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  • Journal Article

    Authigenic formation of Ca-Mg carbonates in the shallow alkaline Lake Neusiedl, Austria 

    Fussmann, Dario; von Hoyningen-Huene, Avril Jean Elisabeth; Reimer, Andreas; Schneider, Dominik; Babková, Hana; Peticzka, Robert; Maier, Andreas; Arp, Gernot; Daniel, Rolf; Meister, Patrick
    Biogeosciences 2020; 17(7) p.2085-2106
    Despite advances regarding the microbial and organic-molecular impact on nucleation, the formation of dolomite in sedimentary environments is still incompletely understood. Since 1960, apparent dolomite formation has been reported from mud sediments of the shallow, oligohaline and alkaline Lake Neusiedl, Austria. To trace potential dolomite formation or diagenetic alteration processes in its deposits, lake water samples and sediment cores were analyzed with respect to sediment composition, hydrochemistry and bacterial community composition. Sediments comprise 20 cm of homogenous mud with 60 wt % carbonate, which overlies dark-laminated consolidated mud containing 50 wt % carbonate and plant debris. Hydrochemical measurements reveal a shift from oxic lake water with pH 9.0 to anoxic sediment pore water with pH 7.5. A decrease in SO$_2^{−4}$ with a concomitant increase in ΣH$_2$S and NH$^+_4$ from 0 to 15 cm core depth indicates anaerobic heterotrophic decomposition, including sulfate reduction. The bacterial community composition reflects the zonation indicated by the pore water chemistry, with a distinct increase in fermentative taxa below 15 cm core depth. The water column is highly supersaturated with respect to (disordered) dolomite and calcite, whereas saturation indices of both minerals rapidly approach zero in the sediment. Notably, the relative proportions of different authigenic carbonate phases and their stoichiometric compositions remain constant with increasing core depth. Hence, evidence for Ca–Mg carbonate formation or ripening to dolomite is lacking within the sediment of Lake Neusiedl. As a consequence, precipitation of high-magnesium calcite (HMC) and protodolomite does not occur in association with anoxic sediment and sulfate-reducing conditions. Instead, analytical data for Lake Neusiedl suggest that authigenic HMC and protodolomite precipitate from the supersaturated, well-mixed aerobic water column. This observation supports an alternative concept to dolomite formation in anoxic sediments, comprising Ca–Mg carbonate precipitation in the water column under aerobic and alkaline conditions.
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  • Journal Article

    Characterizing the Reactivity of Metallic Iron for Water Treatment: H$_2$ Evolution in H$_2$SO$_4$ and Uranium Removal Efficiency 

    Ndé-Tchoupé, Arnaud Igor; Hu, Rui; Gwenzi, Willis; Nassi, Achille; Noubactep, Chicgoua
    Water 2020; 12(6) p.1-18: Art. 1523
    Metallic iron (Fe$^0$) has been demonstrated as an excellent material for decentralized safe drinking water provision, wastewater treatment and environmental remediation. An open issue for all these applications is the rational material selection or quality assurance. Several methods for assessing Fe$^0$ quality have been presented, but all of them are limited to characterizing its initial reactivity. The present study investigates H$_2$ evolution in an acidic solution (pH 2.0) as an alternative method, while comparing achieved results to those of uranium removal in quiescent batch experiments at neutral pH values. The unique feature of the H$_2$ evolution experiment is that quantitative H$_2$ production ceased when the pH reached a value of 3.1. A total of twelve Fe$^0$ specimens were tested. The volume of molecular H$_2$ produced by 2.0 g of each Fe$^0$ specimen in 560 mL H$_2$SO$_4$ (0.01 M) was monitored for 24 h. Additionally, the extent of U(VI) (0.084 mM) removal from an aqueous solution (20.0 mL) by 0.1 g of Fe$^0$ was characterized. All U removal experiments were performed at room temperature (22 ± 2 °C) for 14 days. Results demonstrated the difficulty of comparing Fe$^0$ specimens from different sources and confirmed that the elemental composition of Fe$^0$ is not a stand-alone determining factor for reactivity. The time-dependent changes of H$_2$ evolution in H$_2$SO$_4$ confirmed that tests in the neutral pH range just address the initial reactivity of Fe$^0$ materials. In particular, materials initially reacting very fast would experience a decrease in reactivity in the long-term, and this aspect must be incorporated in designing novel materials and sustainable remediation systems. An idea is proposed that could enable the manufacturing of intrinsically long-term efficient Fe$^0$ materials for targeted operations as a function of the geochemistry.
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  • Journal Article

    Application of Wavelet De-Noising for Travel-Time Based Hydraulic Tomography 

    Yang, Huichen; Hu, Rui; Qiu, Pengxiang; Liu, Quan; Xing, Yixuan; Tao, Ran; Ptak, Thomas
    Water 2020; 12(6) p.1-23: Art. 1533
    Travel-time based hydraulic tomography is a promising method to characterize heterogeneity of porous-fractured aquifers. However, there is inevitable noise in field-scale experimental data and many hydraulic signal travel times, which are derived from the pumping test’s first groundwater level derivative drawdown curves and are strongly influenced by noise. The required data processing is thus quite time consuming and often not accurate enough. Therefore, an effective and accurate de-noising method is required for travel time inversion data processing. In this study, a series of hydraulic tomography experiments were conducted at a porous-fractured aquifer test site in Goettingen, Germany. A numerical model was built according to the site’s field conditions and tested based on diagnostic curve analyses of the field experimental data. Gaussian white noise was then added to the model’s calculated pumping test drawdown data to simulate the real noise in the field. Afterward, different de-noising methods were applied to remove it. This study has proven the superiority of the wavelet de-noising approach compared with several other filters. A wavelet de-noising method with calibrated mother wavelet type, de-noising level, and wavelet level was then determined to obtain the most accurate travel time values. Finally, using this most suitable de-noising method, the experimental hydraulic tomography travel time values were calculated from the de-noised data. The travel time inversion based on this de-noised data has shown results consistent with previous work at the test site.
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  • Journal Article

    Understanding the Operating Mode of Fe$^0$/Fe-Sulfide/H$_2$O Systems for Water Treatment 

    Xiao, Minhui; Hu, Rui; Cui, Xuesong; Gwenzi, Willis; Noubactep, Chicgoua
    Processes 2020; 8(4) p.1-15: Art. 409
    The general suitability of water treatment systems involving metallic iron (Fe$^0$) is wellestablished. Various attempts have been made to improve the effciency of conventional Fe$^0$ systems. One promising approach combines granular Fe$^0$ and an iron sulfide mineral to form Fe$^0$/Fe-sulfide/H$_2$O systems. An improved understanding of the fundamental principles by which such systems operate is still needed. Through a systematic analysis of possible reactions and the probability of their occurrence, this study establishes that sulfide minerals primarily sustain iron corrosion by lowering the pH of the system. Thus, chemical reduction mediated by Fe$^{\text{II}}$ species (indirect reduction) is a plausible explanation for the documented reductive transformations. Such a mechanism is consistent with the nature and distribution of reported reaction products. While considering the mass balance of iron, it appears that lowering the pH value increases Fe$^0$ dissolution, and thus subsequent precipitation of hydroxides. This precipitation reaction is coupled with the occlusion of contaminants (co-precipitation or irreversible adsorption). The extent to which individual sulfides impact the effciency of the tested systems depends on their intrinsic reactivities and the operational conditions (e.g., sulfide dosage, particle size, experimental duration). Future research directions, including the extension of Fe$^0$/Fe-sulfide/H$_2$O systems to drinking water filters and (domestic) wastewater treatment using the multi-soil-layering method are highlighted.
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  • Journal Article

    Middle Class, Tradition and the Desi-Realm—Discourses of Alternative Food Networks in Bengaluru, India 

    Erler, Mirka; Dittrich, Christoph
    Sustainability 2020; 12(7) p.1-15: Art. 2741
    It has repeatedly been claimed that persistent traditional agriculture and marketing in countries of the Global South, such as India, are a fruitful basis for the foundation of alternative food networks (AFNs). However, literature on AFNs in the Global South is scarce and it thus remains uncertain how the appropriation of traditional agri-food practices plays out. We conducted semi-structured expert interviews with representatives of 14 AFNs in Bengaluru, India, in order to explore their aims and approaches. We found that there is a high variety of different AFNs in the city. One salient discourse among the representatives was that the agri-food system can be improved by a revitalization of tradition. In this paper, we discuss the implications of this conviction on representatives of AFNs. Traditionalism, we argue, does rather represent a deflection from achieving the stated goals of the AFN, namely the improvement of the livelihood of Indian farmers.
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  • Journal Article

    Steel Wool for Water Treatment: Intrinsic Reactivity and Defluoridation Efficiency 

    Hildebrant, Benjamin; Ndé-Tchoupé, Arnaud Igor; Lufingo, Mesia; Licha, Tobias; Noubactep, Chicgoua
    Processes 2020; 8(3) p.1-21: Art. 265
    Studies were undertaken to characterize the intrinsic reactivity of Fe$^0$-bearing steel wool (Fe$^0$ SW) materials using the ethylenediaminetetraacetate method (EDTA test). A 2 mM Na$_2$-EDTA solution was used in batch and column leaching experiments. A total of 15 Fe$^0$ SW specimens and one granular iron (GI) were tested in batch experiments. Column experiments were performed with four Fe$^0$ SW of the same grade but from various suppliers and the GI. The conventional EDTA test (0.100 g Fe$^0$, 50 mL EDTA, 96 h) protocol was modified in two manners: (i) Decreasing the experimental duration (down to 24 h) and (ii) decreasing the Fe$^0$ mass (down to 0.01 g). Column leaching studies involved glass columns filled to 1/4 with sand, on top of which 0.50 g of Fe$^0$ was placed. Columns were daily gravity fed with EDTA and effluent analyzed for Fe concentration. Selected reactive Fe$^0$ SW specimens were additionally investigated for discoloration effciency of methylene blue (MB) in shaken batch experiments (75 rpm) for two and eight weeks. The last series of experiments tested six selected Fe$^0$ SW for water defluoridation in Fe$^0$/sand columns. Results showed that (i) the modifications of the conventional EDTA test enabled a better characterization of Fe$^0$ SW; (ii) after 53 leaching events the Fe$^0$ SW showing the best k$_{\text{EDTA}}$ value released the lowest amount of iron; (iii) all Fe$^0$ specimens were effcient at discoloring cationic MB after eight weeks; (iv) limited water defluoridation by all six Fe$^0$ SW was documented. Fluoride removal in the column systems appears to be a viable tool to characterize the Fe$^0$ long-term corrosion kinetics. Further research should include correlation of the intrinsic reactivity of SW specimens with their effciency at removing different contaminants in water.
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  • Journal Article

    Nonlinear Autoregressive Neural Networks to Predict Hydraulic Fracturing Fluid Leakage into Shallow Groundwater 

    Taherdangkoo, Reza; Tatomir, Alexandru; Taherdangkoo, Mohammad; Qiu, Pengxiang; Sauter, Martin
    Water 2020; 12(3) p.1-14: Art. 841
    Hydraulic fracturing of horizontal wells is an essential technology for the exploitation of unconventional resources, but led to environmental concerns. Fracturing fluid upward migration from deep gas reservoirs along abandoned wells may pose contamination threats to shallow groundwater. This study describes the novel application of a nonlinear autoregressive (NAR) neural network to estimate fracturing fluid flow rate to shallow aquifers in the presence of an abandoned well. The NAR network is trained using the Levenberg–Marquardt (LM) and Bayesian Regularization (BR) algorithms and the results were compared to identify the optimal network architecture. For NAR-LM model, the coeffcient of determination ($R^2$) between measured and predicted values is 0.923 and the mean squared error ($MSE$) is $4.2\times 10^{-4}$, and the values of $R^2 = 0.944$ and $MSE = 2.4\times 10^{-4}$ were obtained for the NAR-BR model. The results indicate the robustness and compatibility of NAR-LM and NAR-BR models in predicting fracturing fluid flow rate to shallow aquifers. This study shows that NAR neural networks can be useful and hold considerable potential for assessing the groundwater impacts of unconventional gas development.
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  • Journal Article

    Fresh groundwater discharge insignificant for the world’s oceans but important for coastal ecosystems 

    Luijendijk, Elco; Gleeson, Tom; Moosdorf, Nils
    Nature Communications 2020; 11(1) p.1-12: Art. 1260
    The flow of fresh groundwater may provide substantial inputs of nutrients and solutes to the oceans. However, the extent to which hydrogeological parameters control groundwater flow to the world’s oceans has not been quantified systematically. Here we present a spatially resolved global model of coastal groundwater discharge to show that the contribution of fresh groundwater accounts for ~0.6% (0.004%–1.3%) of the total freshwater input and ~2% (0.003%–7.7%) of the solute input for carbon, nitrogen, silica and strontium. However, the coastal discharge of fresh groundwater and nutrients displays a high spatial variability and for an estimated 26% (0.4%–39%) of the world’s estuaries, 17% (0.3%–31%) of the salt marshes and 14% (0.1–26%) of the coral reefs, the flux of terrestrial groundwater exceeds 25% of the river flux and poses a risk for pollution and eutrophication.
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  • Journal Article

    Geothermal play typing in Germany, case study Molasse Basin: a modern concept to categorise geothermal resources related to crustal permeability 

    Moeck, Inga S.; Dussel, Michael; Weber, Josef; Schintgen, Tom; Wolfgramm, Markus
    Netherlands Journal of Geosciences 2019; 98
    The majority of running geothermal plants worldwide are located in geological settings with convection- or advection-dominant heat transport. In Germany as in most regions in Europe, conduction is the dominating heat transport mechanism, with a resulting average geothermal gradient. The geothermal play type concept is a modern methodology to group geothermal resources according to their geological setting, and characteristic heat transport mechanisms. In particular, the quantity of heat transport is related to fluid flow in natural or engineered geothermal reservoirs. Hence, the permeability structure is a key element for geothermal play typing. Following the existing geothermal play type catalogue, four major geothermal play types can be identified for Germany: intracratonic basins, foreland basins and basement/crystalline rock provinces as conduction-dominated play types, and extensional terrains as the convection-dominated play type. The installed capacity of geothermal facilities sums up to 397.1 MWth by the end of 2018. District heating plants accounted for the largest portion, with about 337.0 MWth. The majority of these installations are located in the play type ‘foreland basin’, namely the Molasse Basin in southern Germany. The stratigraphic unit for geothermal use is the Upper Jurassic, also known as ‘Malm’ formation, a carbonate reservoir with high variability in porosity and permeability. Recently drilled wells in the southernmost Molasse Basin indicate the Upper Jurassic as a tight, fracture-controlled reservoir, not usable for conventional hydrothermal well doublets. Our new data compilation including the recently drilled deep geothermal well Geretsried reveals the relation of porosity and permeability to depth. The results suggest that obviously diagenetic processes control permeability with depth in carbonate rock, diminishing the predictability of reservoir porosity and permeability. The play type concept helps to delineate these property variations in play type levels because it is based on geological constraints, common for exploration geology. Following the general idea of play typing, the results from this play analysis can be transferred to geological analogues as carbonate rock play levels in varying depth.
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  • Journal Article

    Siboglinidae Tubes as an Additional Niche for Microbial Communities in the Gulf of Cádiz—A Microscopical Appraisal 

    Rincón-Tomás, Blanca; González, Francisco Javier; Somoza, Luis; Sauter, Kathrin; Madureira, Pedro; Medialdea, Teresa; Carlsson, Jens; Reitner, Joachim; Hoppert, Michael
    Microorganisms 2020; 8(3): Art. 367
    Siboglinids were sampled from four mud volcanoes in the Gulf of Cádiz (El Cid MV, Bonjardim MV, Al Gacel MV, and Anastasya MV). These invertebrates are characteristic to cold seeps and are known to host chemosynthetic endosymbionts in a dedicated trophosome organ. However, little is known about their tube as a potential niche for other microorganisms. Analyses by scanning and transmission electron microscopy showed dense biofilms on the tube in Al Gacel MV and Anastasya MV specimens by prokaryotic cells. Methanotrophic bacteria were the most abundant forming these biofilms as further supported by 16S rRNA sequence analysis. Furthermore, elemental analyses with electron microscopy and energy-dispersive X-ray spectroscopy point to the mineralization and silicification of the tube, most likely induced by the microbial metabolisms. Bacterial and archaeal 16S rRNA sequence libraries revealed abundant microorganisms related to these siboglinid specimens and certain variations in microbial communities among samples. Thus, the tube remarkably increases the microbial biomass related to the worms and provides an additional microbial niche in deep-sea ecosystems.
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  • Journal Article

    Sterol preservation in hypersaline microbial mats 

    Shen, Yan; Thiel, Volker; Suarez-Gonzalez, Pablo; Rampen, Sebastiaan W.; Reitner, Joachim
    Biogeosciences 2020; 17(3) p.649-666
    Microbial mats are self-sustaining benthic ecosystems composed of highly diverse microbial communities. It has been proposed that microbial mats were widespread in Proterozoic marine environments, prior to the emergence of bioturbating organisms at the Precambrian–Cambrian transition. One characteristic feature of Precambrian biomarker records is that steranes are typically absent or occur in very low concentrations. This has been explained by low eukaryotic source inputs, or degradation of primary produced sterols in benthic microbial mats (“mat-seal effect”). To better understand the preservational pathways of sterols in microbial mats, we analyzed freely extractable and carbonate-bound lipid fractions as well as decalcified extraction residues in different layers of a recent calcifying mat (∼1500 years) from the hypersaline Lake 2 on the island of Kiritimati, central Pacific. A variety of C27–C29 sterols and distinctive C31 4α-methylsterols (4α-methylgorgosterol and 4α-methylgorgostanol, biomarkers for dinoflagellates) were detected in freely extractable and carbonate-bound lipid pools. These sterols most likely originated from organisms living in the water column and the upper mat layers. This autochthonous biomass experienced progressive microbial transformation and degradation in the microbial mat, as reflected by a significant drop in total sterol concentrations, up to 98 %, in the deeper layers, and a concomitant decrease in total organic carbon. Carbonate-bound sterols were generally low in abundance compared to the freely extractable portion, suggesting that incorporation into the mineral matrix does not play a major role in the preservation of eukaryotic sterols in this mat. Likewise, pyrolysis of extraction residues suggested that sequestration of steroid carbon skeletons into insoluble organic matter was low compared to hopanoids. Taken together, our findings argue for a major mat-seal effect affecting the distribution and preservation of steroids in the mat studied. This result markedly differs from recent findings made for another microbial mat growing in the nearby hypersaline Lake 22 on the same island, where sterols showed no systematic decrease with depth. The observed discrepancies in the taphonomic pathways of sterols in microbial mats from Kiritimati may be linked to multiple biotic and abiotic factors including salinity and periods of subaerial exposure, implying that caution has to be exercised in the interpretation of sterol distributions in modern and ancient microbial mat settings.
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  • Journal Article

    FXD-CSD-GUI : a graphical user interface for the X-ray-diffraction-based determination of crystallite size distributions 

    Neher, Sigmund H.; Klein, Helmut; Kuhs, Werner F.
    Journal of Applied Crystallography 2019; 52(6) p.1437-1439
    Bragg intensities can be used to analyse crystal size distributions in a method called FXD-CSD, which is based on the fast measurement of many Bragg spots using two-dimensional detectors. This work presents the Python-based software and its graphical user interface FXD-CSD-GUI. The GUI enables user-friendly data handling and processing and provides both graphical and numerical crystal size distribution results.
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  • Journal Article

    Two new ant species (Formicidae: Dorylinae, Ponerinae) from New Caledonia 

    Ramage, Thibault; Jouault, Corentin; Schmidt, Alexander R.; Seyfullah, Leyla J.; Perrichot, Vincent
    European Journal of Taxonomy(589) p.1-14
    Two new species of ants (Hymenoptera: Formicidae) collected from New Caledonia are described and figured based on worker specimens: Leptogenys loarelae Ramage sp. nov. (Ponerinae, Ponerini) and Lioponera neocaledonica Jouault, Ramage & Perrichot sp. nov. (Dorylinae, Cerapachyini). All specimens were collected from the South Province of Grande Terre. These two new species are primarily distinguished from the other New Caledonian relatives by the size and shape of petiole for L. loarelae Ramage sp. nov. and by the presence of dorsolateral margins on the mesosoma for L. neocaledonica Jouault, Ramage & Perrichot sp. nov. Keys to New Caledonian Leptogenys and Lioponera are provided.
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  • Journal Article

    A numerical sensitivity study of how permeability, porosity, geological structure, and hydraulic gradient control the lifetime of a geothermal reservoir 

    Bauer, Johanna F.; Krumbholz, Michael; Luijendijk, Elco; Tanner, David C.
    Solid Earth 2019; 10(6) p.2115-2135
    Geothermal energy is an important and sustainable resource that has more potential than is currently utilized. Whether or not a deep geothermal resource can be exploited, mostly depends on, besides temperature, the utilizable reservoir volume over time, which in turn largely depends on petrophysical parameters. We show, using over 1000 (n=1027) 4-D finite-element models of a simple geothermal doublet, that the lifetime of a reservoir is a complex function of its geological parameters, their heterogeneity, and the background hydraulic gradient (BHG). In our models, we test the effects of porosity, permeability, and BHG in an isotropic medium. Furthermore, we simulate the effect of permeability contrast and anisotropy induced by layering, fractures, and a fault. We quantify the lifetime of the reservoir by measuring the time to thermal breakthrough, i.e. how many years pass before the temperature of the produced fluid falls below the 100 ∘C threshold. The results of our sensitivity study attest to the positive effect of high porosity; however, high permeability and BHG can combine to outperform the former. Particular configurations of all the parameters can cause either early thermal breakthrough or extreme longevity of the reservoir. For example, the presence of high-permeability fractures, e.g. in a fault damage zone, can provide initially high yields, but it channels fluid flow and therefore dramatically restricts the exploitable reservoir volume. We demonstrate that the magnitude and orientation of the BHG, provided permeability is sufficiently high, are the prime parameters that affect the lifetime of a reservoir. Our numerical experiments show also that BHGs (low and high) can be outperformed by comparatively small variations in permeability contrast (103) and fracture-induced permeability anisotropy (101) that thus strongly affect the performance of geothermal reservoirs.
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  • Journal Article

    Characterizing a Newly Designed Steel-Wool-Based Household Filter for Safe Drinking Water Provision: Hydraulic Conductivity and Efficiency for Pathogen Removal 

    Tepong-Tsindé, Raoul; Ndé-Tchoupé, Arnaud Igor; Noubactep, Chicgoua; Nassi, Achille; Ruppert, Hans
    Processes 2019; 7(12): Art. 966
    This study characterizes the decrease of the hydraulic conductivity (permeability loss) of a metallic iron-based household water filter (Fe0 filter) for a duration of 12 months. A commercial steel wool (SW) is used as Fe0 source. The Fe0 unit containing 300 g of SW was sandwiched between two conventional biological sand filters (BSFs). The working solution was slightly turbid natural well water polluted with pathogens (total coliform = 1950 UFC mL−1) and contaminated with nitrate ([NO3−] = 24.0 mg L−1). The system was monitored twice per month for pH value, removal of nitrate, coliforms, and turbidity, the iron concentration, as well as the permeability loss. Results revealed a quantitative removal of coliform (>99%), nitrate (>99%) and turbidity (>96%). The whole column effluent depicted drinking water quality. The permeability loss after one year of operation was about 40%, and the filter was still producing 200 L of drinking water per day at a flow velocity of 12.5 L h−1. A progressive increase of the effluent pH value was also recorded from about 5.0 (influent) to 8.4 at the end of the experiment. The effluent iron concentration was constantly lower than 0.2 mg L−1, which is within the drinking-water quality standards. This study presents an affordable design that can be one-to-one translated into the real world to accelerate the achievement of the UN Sustainable Development Goals for safe drinking water.
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  • Journal Article

    Intertwined effects of climate and land use change on environmental dynamics and carbon accumulation in a mangrove‐fringed coastal lagoon in Java, Indonesia 

    Hapsari, K. Anggi; Jennerjahn, Tim C.; Lukas, Martin C.; Karius, Volker; Behling, Hermann
    Global Change Biology
    The identification and quantification of natural carbon (C) sinks is critical to global climate change mitigation efforts. Tropical coastal wetlands are considered important in this context, yet knowledge of their dynamics and quantitative data are still scarce. In order to quantify the C accumulation rate and understand how it is influenced by land use and climate change, a palaeoecological study was conducted in the mangrove-fringed Segara Anakan Lagoon (SAL) in Java, Indonesia. A sediment core was age-dated and analyzed for its pollen and spore, elemental and biogeochemical compositions. The results indicate that environmental dynamics in the SAL and its C accumulation over the past 400 years were controlled mainly by climate oscillations and anthropogenic activities. The interaction of these two factors changed the lagoon's sediment supply and salinity, which consequently altered the organic matter composition and deposition in the lagoon. Four phases with varying climates were identified. While autochthonous mangrove C was a significant contributor to carbon accumulation in SAL sediments throughout all four phases, varying admixtures of terrestrial C from the hinterland also contributed, with natural mixed forest C predominating in the early phases and agriculture soil C predominating in the later phases. In this context, climate-related precipitation changes are an overarching control, as surface water transport through rivers serves as the "delivery agent" for the outcomes of the anthropogenic impact in the catchment area into the lagoon. Amongst mangrove-dominated ecosystems globally, the SAL is one of the most effective C sinks due to high mangrove carbon input in combination with a high allochthonous carbon input from anthropogenically enhanced sediment from the hinterland and increased preservation. Given the substantial C sequestration capacity of the SAL and other mangrove-fringed coastal lagoons, conservation and restoration of these ecosystems is vitally important for climate change mitigation.
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  • Journal Article

    First evidence of terrestrial ambrein formation in human adipocere 

    von der Lühe, Barbara; Mayes, Robert W.; Thiel, Volker; Dawson, Lorna A.; Graw, Matthias; Rowland, Steven J.; Fiedler, Sabine
    Scientific Reports 2019; 9(1): Art. 18370
    To date, the only known occurrence of ambrein, an important perfumery organic molecule, is in coproliths found in about one in a hundred sperm whales. Jetsam ambergris coproliths from the whale are also found occasionally on beaches worldwide. Here we report on the surprising occurrence of ambrein in human adipocere. Adipocere is a waxy substance formed post-mortem during incomplete anaerobic decomposition of soft tissues. Adipocere samples obtained from grave exhumations were analysed using gas chromatography-mass spectrometry (GC-MS). In addition to the typical fatty acids of adipocere, lesser amounts of ambrein were identified in the samples, in abundances similar to those of the major accompanying faecal steroids. The distribution of these compounds suggests that ambrein was produced post-mortem during the microbial decomposition of faecal residues and tissues. It is assumed that the adipocere matrix of saturated fatty acidsaided the preservation of ambrein over extended periods of time, because adipocere is stable against degradation. The association of ambrein formation in ageing faecal material, under moist, oxygen-depleted conditions, now requires more attention in studies of other mammalian and geological samples. Indeed, ambrein and its transformation products may be useful novel chemical indicators of aged faecal matter and decomposed bodies.
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