Items 1-20 of 501

    • Journal Article

      Genesis and mechanisms controlling tornillo seismo-volcanic events in volcanic areas 

      Fazio, Marco; Alparone, Salvatore; Benson, Philip M.; Cannata, Andrea; Vinciguerra, Sergio
      Scientific Reports 2019; 9(1): Art. 7338
      Volcanic activity is often preceded or accompanied by different types of seismo-volcanic signals. Among these signals, the so-called tornillo (Spanish for "screw") events are considered to belong to a unique class of volcano-seismicity characterised by a long-duration coda, amplitude modulation and high-quality factor. These data constitute important evidence for the gas fraction inside magmatic fluids. However, the mechanism behind this unique signal remains not fully understood. Here we report new laboratory evidence showing that two different processes have either scale-invariant or scale-dependent effects in generating tornillo-like events. These processes are respectively the gas pressure gradient, which triggers the event and regulates the slow decaying coda, and the fluid resonance into small scale structures which, in turn, control the frequency content of the signal. Considering that the gas pressure gradient is proportional to the fluid flow, these new findings, as applied to volcanoes, provide new information to better quantify both gas rate and volume, and the dimension of the resonator.
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    • Journal Article

      Traces of Carnian volcanic activity in the Transdanubian Range, Hungary 

      Dunkl, István; Farics, Éva; Józsa, Sándor; Lukács, Réka; Haas, János; Budai, Tamás
      International Journal of Earth Sciences p.1-16
      The South Alpine–Dinaridic realm was affected by igneous activity in the Middle Triassic; the marine carbonate platforms and the adjacent basins contain highly variable intrusive-volcanic assemblages. We studied the petrography and determined the zircon U–Pb ages of the Triassic volcanic products in the Transdanubian Range. The geochemical features and thus the geodynamic context of the magmatism are badly known, as the rocks experienced variable chemical alteration. The exact duration of the igneous activity is also poorly constrained, as the geochronological data of the former studies were obtained mostly by the weathering-sensitive K–Ar and Rb–Sr methods and thus some data even being younger than the age of the stratigraphic cover. The presence of andesite dikes and of pebbles and cobbles (< 20 cm) of basalt, andesite, rhyolite and of rhyolitic tuff in the Triassic carbonate platform deposits indicates that within the Transdanubian Range formed a volcanic complex in Triassic. The major mineralogical and geochemical features of the Transdanubian igneous suite are similar to the Triassic formations in the Southern Alps. However, dissimilar zircon composition excludes the immediate relationship of the zircon-bearing silicic formations in the two tectonic units. New U–Pb ages show that the beginning of the volcanic activity is probably coeval with the eruption of the widespread “pietra verde” trachytic tuffs in the Upper Anisian–Ladinian successions, but the majority of the ages are younger than those ash layers. The new age constraints give a bench-mark for the termination of the volcanic activity in Carnian time in the Transdanubian Range.
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    • Journal Article

      Optical and SAR Remote Sensing Synergism for Mapping Vegetation Types in the Endangered Cerrado/Amazon Ecotone of Nova Mutum—Mato Grosso 

      de Souza Mendes, Flávia; Baron, Daniel; Gerold, Gerhard; Liesenberg, Veraldo; Erasmi, Stefan
      Remote Sensing 2019; 11(10): Art. 1161
      Mapping vegetation types through remote sensing images has proved to be e ective, especially in large biomes, such as the Brazilian Cerrado, which plays an important role in the context of management and conservation at the agricultural frontier of the Amazon. We tested several combinations of optical and radar images to identify the four dominant vegetation types that are prevalent in the Cerrado area (i.e., cerrado denso, cerradão, gallery forest, and secondary forest). We extracted features from both sources of data such as intensity, grey level co-occurrence matrix, coherence, and polarimetric decompositions using Sentinel 2A, Sentinel 1A, ALOS-PALSAR 2 dual/full polarimetric, and TanDEM-X images during the dry and rainy season of 2017. In order to normalize the analysis of these features, we used principal component analysis and subsequently applied the Random Forest algorithm to evaluate the classification of vegetation types. During the dry season, the overall accuracy ranged from 48 to 83%, and during the dry and rainy seasons it ranged from 41 up to 82%. The classification using Sentinel 2A images during the dry season resulted in the highest overall accuracy and kappa values, followed by the classification that used images from all sensors during the dry and rainy season. Optical images during the dry season were su cient to map the di erent types of vegetation in our study area.
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    • Journal Article

      A Numerical Study on Travel Time Based Hydraulic Tomography Using the SIRT Algorithm with Cimmino Iteration 

      Qiu, Pengxiang; Hu, Rui; Hu, Linwei; Liu, Quan; Xing, Yixuan; Yang, Huichen; Qi, Junjie; Ptak, Thomas
      Water 2019; 11(5): Art. 909
      Travel time based hydraulic tomography is a technique for reconstructing the spatial distribution of aquifer hydraulic properties (e.g., hydraulic di usivity). Simultaneous Iterative Reconstruction Technique (SIRT) is a widely used algorithm for travel time related inversions. Due to the drawbacks of SIRT implementation in practice, a modified SIRT with Cimmino iteration (SIRT-Cimmino) is proposed in this study. The incremental correction is adjusted, and an iteration-dependent relaxation parameter is introduced. These two modifications enable an appropriate speed of convergence, and the stability of the inversion process. Furthermore, a new result selection rule is suggested to determine the optimal iteration step and its corresponding result. SIRT-Cimmino and SIRT are implemented and verified by using two numerical aquifer models with di erent predefined (“true”) di usivity distributions, where high di usivity zones are embedded in a homogenous low di usivity field. Visual comparison of the reconstructions shows that the reconstruction based on SIRT-Cimmino demonstrates the aquifer’s hydraulic features better than the conventional SIRT algorithm. Root mean square errors and correlation coe cients are also used to quantitatively evaluate the performance of the inversion. The reconstructions based on SIRT-Cimmino are found to preserve the connectivity of the high di usivity zones and to provide a higher structural similarity to the “true” distribution.
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    • Journal Article

      Palaeoenvironmental setting of lacustrine stromatolites in the Miocene Wudaoliang Group, northern Tibetan Plateau 

      Zeng, Ling-Qi; Yi, Hai-Sheng; Xia, Guo-Qing; Simon, Klaus; Heim, Christine; Arp, Gernot
      Journal of Palaeogeography. 2019 May 02;8(1):18
      Lacustrine stromatolites were widespread in the Miocene Wudaoliang Group (stromatolites of the Wudaoliang Group), northern Tibetan Plateau; but only at one location nearby the Wudaoliang Town, they occurred intensively in thick, laterally traceable beds (Wudaoliang stromatolites). Although deposited in lacustrine environment, the lack of fossils in these rocks hampers determining whether the stromatolites formed in freshwater or saline conditions. To address this problem, and in an attempt to identify criteria to distinguish differences of freshwater and saline conditions, we studied the laminae microfabrics, stable carbon and oxygen isotope ratios, rare earth element patterns and biomarkers of the stromatolites. These stromatolites can be divided into fenestral stromatolites and agglutinated stromatolites. The fabric of fenestral stromatolites is formed by microcrystalline carbonate enclosing spar-cemented, angular crystal traces. Essentially, this fabric is interpreted as pseudomorph after former formed evaporite crystals. Faecal pellets identical to that of the present-day brine shrimp Artemia, lack of other eukaryotic fossils, and stable isotopic signals point to a shallow, evaporation-dominated hypersaline lake setting. Covariation of carbon and oxygen isotopes indicates hydrologically closed conditions of the Miocene lake on northern Tibetan Plateau. However, if compared to other lacustrine carbonates of the Wudaoliang Group, the high δ13C values of the investigated Wudaoliang stromatolites reveal an additional photosynthetic effect during the deposition of the stromatolites. Furthermore, although no direct evidence is available from field observations and microfabrics, a positive europium anomaly of Wudaoliang stromatolites indicates that a palaeo-hydrothermal inflow system had existed in the outcrop area. These new results favour a hypersaline lake setting subject to hot spring inflow for the Wudaoliang stromatolites, in contrast to earlier interpretations suggesting a freshwater lake setting (e.g. Yi et al., Journal of Mineralogy and Petrology 28: 106–113, 2008; Zeng et al., Journal of Mineralogy and Petrology 31: 111–119, 2011). This approach may be appropriate for other lacustrine, unfossiliferous microbialites in settings where the environmental conditions are difficult to determine.
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    • Journal Article

      Analogue Fracture Experiments and Analytical Modeling of Unsaturated Percolation Dynamics in Fracture Cascades 

      Noffz, Torsten; Dentz, Marco; Kordilla, Jannes
      Vadose Zone Journal 2019; 18(1)
      Infiltration and recharge dynamics in fractured aquifer systems often strongly deviate from diffuse Darcy–Buckingham type flows due to the existence of a complex gravity-driven flow component along fractures, fracture networks, and fault zones. The formation of preferential flow paths in the unsaturated or vadose zone can trigger rapid mass fluxes, which are difficult to recover by volume-effective modeling approaches (e.g., the Richards equation) due to the nonlinear nature of free-surface flows and mass partitioning processes at unsaturated fracture intersections. In this study, well-controlled laboratory experiments enabled the isolation of single aspects of the mass redistribution process that ultimately affect travel time distributions across scales. We used custom-made acrylic cubes (20 by 20 by 20 cm) in analog percolation experiments to create simple wide-aperture fracture networks intersected by one or multiple horizontal fractures. A high-precision multichannel dispenser produced gravity-driven free-surface flow (droplets or rivulets) at flow rates ranging from 1 to 5 mL min−1. Total inflow rates were kept constant while the fluid was injected via 15 (droplet flow) or three inlets (rivulet flow) to reduce the impact of erratic flow dynamics. Normalized fracture inflow rates were calculated and compared for aperture widths of 1 and 2.5 mm. A higher efficiency in filling an unsaturated fracture by rivulet flow observed in former studies was confirmed. The onset of a capillary-driven Washburn-type flow was determined and recovered by an analytical solution. To upscale the dynamics and enable the prediction of mass partitioning for arbitrary-sized fracture cascades, a Gaussian transfer function was derived that reproduces the repetitive filling of fractures, where rivulet flow is the prevailing regime. Results show good agreement with experimental data for all tested aperture widths.
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    • Journal Article

      Bisnorgammacerane traces predatory pressure and the persistent rise of algal ecosystems after Snowball Earth 

      van Maldegem, Lennart M.; Sansjofre, Pierre; Weijers, Johan W. H.; Wolkenstein, Klaus; Strother, Paul K.; Wörmer, Lars; Hefter, Jens; Nettersheim, Benjamin J.; Hoshino, Yosuke; Schouten, Stefan; et al.
      Sinninghe Damsté, Jaap S.Nath, NilamoniGriesinger, ChristianKuznetsov, Nikolay B.Elie, MarcelElvert, MarcusTegelaar, ErikGleixner, GerdHallmann, Christian
      Nature Communications 2019; 10(1): Art. 476
      Eukaryotic algae rose to ecological relevance after the Neoproterozoic Snowball Earth glaciations, but the causes for this consequential evolutionary transition remain enigmatic. Cap carbonates were globally deposited directly after these glaciations, but they are usually organic barren or thermally overprinted. Here we show that uniquely-preserved cap dolostones of the Araras Group contain exceptional abundances of a newly identified biomarker: 25,28-bisnorgammacerane. Its secular occurrence, carbon isotope systematics and co-occurrence with other demethylated terpenoids suggest a mechanistic connection to extensive microbial degradation of ciliate-derived biomass in bacterially dominated ecosystems. Declining 25,28-bisnorgammacerane concentrations, and a parallel rise of steranes over hopanes, indicate the transition from a bacterial to eukaryotic dominated ecosystem after the Marinoan deglaciation. Nutrient levels already increased during the Cryogenian and were a prerequisite, but not the ultimate driver for the algal rise. Intense predatory pressure by bacterivorous protists may have irrevocably cleared self-sustaining cyanobacterial ecosystems, thereby creating the ecological opportunity that allowed for the persistent rise of eukaryotic algae to global importance.
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    • Journal Article

      Archaean phosphates: a case study of transformation processes in apatite from the Barberton greenstone belt 

      Birski, Łukasz; Słaby, E.; Wirth, R.; Koch-Müller, M.; Simon, K.; Wudarska, A.; Götze, J.; Lepland, A.; Hofmann, A.; Kuras, A.
      Contributions to Mineralogy and Petrology 2019; 174(3): Art. 25
      Multiple tools have been used to determine the sensitivity of phosphates from the early Archaean Barberton greenstone belt to transformation. The assessment of the degree of transformation is crucial for verifying data about the parameters of the paleo-environment. From the obtained results, three generations of phosphates can be distinguished. Group A is observed in cherts and banded iron formation BIF early-generation fluor-hydroxyapatite that precipitated from seawater. It is characterized by flat rare earth element (REE) patterns with a positive Eu anomaly and high Y/Ho ratio in the range of 54–70. Apatites in this group lack any visible indicators of secondary alterations at the micro- and nanoscales. Fourier transform infrared spectra indicate that these apatites are relatively rich in water, and, due to cationic substitution, their OH-stretching regions exhibit complex ordering and numerous component bands. The characteristics observed in the cherts and silicified felsic volcaniclastics of group B imply advanced metasomatic alteration. They exhibit light and heavy REE depletion and an absence of water in the halogen site. Nanoscale investigations reveal cracks, pores, nanofluid inclusions and nanochannellike structures, as well as inclusions. Group C is represented by igneous-derived apatites that partially reflect their igneous origin. The phosphates are predominantly fluorapatite with typical magmatic apatite REE distribution patterns. Imaging at the micro- and nanoscales indicates that they partially preserve the signature of igneous origin. It seems that some of the analyzed apatite partially preserved their primordial features; therefore, they might be used for the reconstruction of Archaean abiotic systems.
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    • Journal Article

      Fe0/H2O Filtration Systems for Decentralized Safe Drinking Water: Where to from Here? 

      Nanseu-Njiki, Charles; Gwenzi, Willis; Pengou, Martin; Rahman, Mohammad; Noubactep, Chicgoua
      Water 2019; 11(3): Art. 429
      Inadequate access to safe drinking water is one of the most pervasive problems currently afflicting the developing world. Scientists and engineers are called to present affordable but efficient solutions, particularly applicable to small communities. Filtration systems based on metallic iron (Fe0) are discussed in the literature as one such viable solution, whether as a stand-alone system or as a complement to slow sand filters (SSFs). Fe0 filters can also be improved by incorporating biochar to form Fe0-biochar filtration systems with potentially higher contaminant removal efficiencies than those based on Fe0 or biochar alone. These three low-cost and chemical-free systems (Fe0, biochar, SSFs) have the potential to provide universal access to safe drinking water. However, a well-structured systematic research is needed to design robust and efficient water treatment systems based on these affordable filter materials. This communication highlights the technology being developed to use Fe0-based systems for decentralized safe drinking water provision. Future research directions for the design of the next generation Fe0-based systems are highlighted. It is shown that Fe0 enhances the efficiency of SSFs, while biochar has the potential to alleviate the loss of porosity and uncertainties arising from the non-linear kinetics of iron corrosion. Fe0-based systems are an affordable and applicable technology for small communities in low-income countries, which could contribute to attaining self-reliance in clean water supply and universal public health.
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    • Journal Article

      Application of Ordinary Kriging and Regression Kriging Method for Soil Properties Mapping in Hilly Region of Central Vietnam 

      Gia Pham, Tung; Kappas, Martin; Van Huynh, Chuong; Hoang Khanh Nguyen, Linh
      ISPRS International Journal of Geo-Information 2019; 8(3): Art. 147
      Soil property maps are essential resources for agricultural land use. However, soil properties mapping is costly and time-consuming, especially in the regions with complicated topographic conditions. This study was conducted in a hilly region of Central Vietnam with the following objectives: (i) to evaluate the best environmental variables to estimate soil organic carbon (SOC), total nitrogen (TN), and soil reaction (pH) with a regression kriging (RK) model, and (ii) to compare the accuracy of the ordinary kriging (OK) and RK methods. SOC, TN, and soil pH data were measured at 155 locations within the research area with a sampling grid of 2 km 2 km for a soil layer from 0 to 30 cm depth. From these samples, 117 were used for interpolation, and the 38 randomly remaining samples were used for evaluating accuracy. The chosen environmental variables are land use type (LUT), topographic wetness index (TWI), and transformed soil adjusted vegetation index (TSAVI). The results indicate that the LUT variable is more effective than TWI and TSAVI for determining TN and pH when using the RK method, with a variance of 7.00% and 18.40%, respectively. In contrast, a combination of the LUT and TWI variables is the best for SOC mapping with the RK method, with a variance of 14.98%. The OK method seemed more accurate than the RK method for SOC mapping by 3.33% and for TN mapping by 10% but the RK method was found more precise than the OK method for soil pH mapping by 1.81%. Further selection of auxiliary variables and higher sampling density should be considered to improve the accuracy of the RK method.
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    • Journal Article

      Rice-Residue Management Practices of Smallholder Farms in Vietnam and Their Effects on Nutrient Fluxes in the Soil-Plant System 

      Trong Hung, Dao; Hughes, Harold; Keck, Markus; Sauer, Daniela
      Sustainability 2019; 11(6): Art. 1641
      In Vietnam, approximately 39 million tons of rice (Oryza sativa) residues accrue every year. In this study, we quantified soil nutrient balances of paddy rice fields under different crop-residue management practices in northern Vietnam. On twelve farms, we calculated nutrient balances for the four prevalent rice-residue management practices, i.e., (1) direct incorporation of rice residues into the soil, (2) application of rice-residue compost, (3) burning of rice residues on the field, and (4) the use of rice residues as fodder for livestock. Soils under practices (1) to (3) showed a positive nutrient balance, which indicates that soil fertility can be maintained under these practices and that the amounts of chemical fertilizers can be considerably reduced. If not, there is a risk of eutrophication in the surrounding surface waterbodies. Practice (4), in contrast, resulted in a negative nutrient balance, which indicates the need for returning nutrients to the soils. From our findings we conclude that knowledge about the effects of rice-residue management practices on nutrient cycles may help to optimize the use of fertilizers, resulting in a more sustainable form of agriculture.
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    • Journal Article

      Constraining the applicability of organic paleotemperature proxies for the last 90 Myrs 

      de Bar, Marijke W.; Rampen, Sebastiaan W.; Hopmans, Ellen C.; Sinninghe Damsté, Jaap S.; Schouten, Stefan
      Organic Geochemistry 2019; 128 p.122-136
      We evaluated changes in the distributions of long-chain alkenones, long-chain diols and GDGTs, lipids commonly used for paleothermometry, over the last 90 Myrs for sediments deposited on the New Jersey shelf (the Bass River site) and assessed potential effects of different ancestral producers and diagenesis on their distributions and their impact on the associated temperature proxies. As reported before, the Paleogene distributions of alkenones are generally similar to those in modern haptophytes, but unusual alkenone distributions, characterized by a dominant di-unsaturated C40 alkenone, are observed for Late Cretaceous sediments, suggesting different ancestral source organisms for alkenones in this interval. The isoprenoid GDGT distributions remained comparable to modern-day distributions, suggesting that TEX86 can be applied up to ca. 90 Ma. The Miocene long-chain diol distributions are similar to modern-day distributions, but the older sediments reveal unusual distributions, dominated by the C28 1,12- and C26 1,13-diols, suggesting different source organisms before 30 Ma. Accordingly, the LDI does not match other paleotemperature proxies, suggesting its applicability might be compromised for sediments older than the Miocene. Our results indicate that of the three proxies, the TEX86 seems to be the most applicable for deep time temperature reconstructions.
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    • Journal Article

      Analogue Fracture Experiments and Analytical Modeling of Unsaturated Percolation Dynamics in Fracture Cascades 

      Noffz, Torsten; Dentz, Marco; Kordilla, Jannes
      Vadose Zone Journal 2019; 18(1)
      Infiltration and recharge dynamics in fractured aquifer systems often strongly deviate from diffuse Darcy–Buckingham type flows due to the existence of a complex gravity-driven flow component along fractures, fracture networks, and fault zones. The formation of preferential flow paths in the unsaturated or vadose zone can trigger rapid mass fluxes, which are difficult to recover by volume-effective modeling approaches (e.g., the Richards equation) due to the nonlinear nature of free-surface flows and mass partitioning processes at unsaturated fracture intersections. In this study, well-controlled laboratory experiments enabled the isolation of single aspects of the mass redistribution process that ultimately affect travel time distributions across scales. We used custom-made acrylic cubes (20 by 20 by 20 cm) in analog percolation experiments to create simple wide-aperture fracture networks intersected by one or multiple horizontal fractures. A high-precision multichannel dispenser produced gravity-driven free-surface flow (droplets or rivulets) at flow rates ranging from 1 to 5 mL min−1. Total inflow rates were kept constant while the fluid was injected via 15 (droplet flow) or three inlets (rivulet flow) to reduce the impact of erratic flow dynamics. Normalized fracture inflow rates were calculated and compared for aperture widths of 1 and 2.5 mm. A higher efficiency in filling an unsaturated fracture by rivulet flow observed in former studies was confirmed. The onset of a capillary-driven Washburn-type flow was determined and recovered by an analytical solution. To upscale the dynamics and enable the prediction of mass partitioning for arbitrary-sized fracture cascades, a Gaussian transfer function was derived that reproduces the repetitive filling of fractures, where rivulet flow is the prevailing regime. Results show good agreement with experimental data for all tested aperture widths.
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    • Journal Article

      Understanding the Coastal Ecocline: Assessing Sea–Land Interactions at Non-tidal, Low-Lying Coasts Through Interdisciplinary Research 

      Jurasinski, Gerald; Janssen, Manon; Voss, Maren; Böttcher, Michael E.; Brede, Martin; Burchard, Hans; Forster, Stefan; Gosch, Lennart; Gräwe, Ulf; Gründling-Pfaff, Sigrid; et al.
      Haider, FouziaIbenthal, MiriamKarow, NilsKarsten, UlfKreuzburg, MatthiasLange, XaverLeinweber, PeterMassmann, GudrunPtak, ThomasRezanezhad, FereidounRehder, GregorRomoth, KatharinaSchade, HannaSchubert, HendrikSchulz-Vogt, HeideSokolova, Inna M.Strehse, RobertUnger, ViktoriaWestphal, JuliaLennartz, Bernd
      Frontiers in Marine Science 2018; 5: Art. 342
      Coastal zones connect terrestrial and marine ecosystems forming a unique environment that is under increasing anthropogenic pressure. Rising sea levels, sinking coasts, and changing precipitation patterns modify hydrodynamic gradients and may enhance sea–land exchange processes in both tidal and non-tidal systems. Furthermore, the removal of flood protection structures as restoration measure contributes locally to the changing coastlines. A detailed understanding of the ecosystem functioning of coastal zones and the interactions between connected terrestrial and marine ecosystems is still lacking. Here, we propose an interdisciplinary approach to the investigation of interactions between land and sea at shallow coasts, and discuss the advantages and the first results provided by this approach as applied by the research training group Baltic TRANSCOAST. A low-lying fen peat site including the offshore shallow sea area on the southern Baltic Sea coast has been chosen as a model system to quantify hydrophysical, biogeochemical, sedimentological, and biological processes across the land–sea interface. Recently introduced rewetting measures might have enhanced submarine groundwater discharge (SGD) as indicated by distinct patterns of salinity gradients in the near shore sediments, making the coastal waters in front of the study site a mixing zone of fresh- and brackish water. High nutrient loadings, dissolved inorganic carbon (DIC), and dissolved organic matter (DOM) originating from the degraded peat may affect micro- and macro-phytobenthos, with the impact propagating to higher trophic levels. The terrestrial part of the study site is subject to periodic brackish water intrusion caused by occasional flooding, which has altered the hydraulic and biogeochemical properties of the prevailing peat soils. The stable salinity distribution in the main part of the peatland reveals the legacy of flooding events. Generally, elevated sulfate concentrations are assumed to influence greenhouse gas (GHG) emissions, mainly by inhibiting methane production, yet our investigations indicate complex interactions between the different biogeochemical element cycles (e.g., carbon and sulfur) caused by connected hydrological pathways. In conclusion, sea–land interactions are far reaching, occurring on either side of the interface, and can only be understood when both long-term and event-based patterns and different spatial scales are taken into account in interdisciplinary research that involves marine and terrestrial expertise.
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    • Journal Article

      A new method for selecting sites for soil sampling, coupling global weighted principal component analysis and a cost-constrained conditioned Latin hypercube algorithm 

      Nketia, Kwabena Abrefa; Asabere, Stephen Boahen; Erasmi, Stefan; Sauer, Daniela
      MethodsX 2019; 6 p.284-299
      Analysing spatial patterns of soil properties in a landscape requires a sampling strategy that adequately covers soil toposequences. In this context, we developed a hybrid methodology that couples global weighted principal component analysis (GWPCA) and cost-constrained conditioned Latin hypercube algorithm (cLHC). This methodology produce an optimized sampling stratification by analysing the local variability of the soil property, and the influence of environmental factors. The methodology captures the maximum local variances in the global auxiliary dataset with the GWPCA, and optimizes the selection of representative sampling locations for sampling with the cLHC. The methodology also suppresses the subsampling of auxiliary datasets from areas that are less representative of the soil property of interest. Consequently, the method stratifies the geographical space of interest in order to adequately represent the soil property. We present results on the tested method (R2 = 0.90 and RMSE = 0.18 m) from the Guinea savannah zone of Ghana.
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      The Impact of Selected Pretreatment Procedures on Iron Dissolution from Metallic Iron Specimens Used in Water Treatment 

      Hu, Rui; Ndé-Tchoupé, Arnaud; Lufingo, Mesia; Xiao, Minhui; Nassi, Achille; Noubactep, Chicgoua; Njau, Karoli
      Sustainability 2019; 11(3): Art. 671
      Studies were undertaken to determine the reasons why published information regarding the efficiency of metallic iron (Fe0) for water treatment is conflicting and even confusing. The reactivity of eight Fe0 materials was characterized by Fe dissolution in a dilute solution of ethylenediaminetetraacetate (Na2–EDTA; 2 mM). Both batch (4 days) and column (100 days) experiments were used. A total of 30 different systems were characterized for the extent of Fe release in EDTA. The effects of Fe0 type (granular iron, iron nails and steel wool) and pretreatment procedure (socking in acetone, EDTA, H2O, HCl and NaCl for 17 h) were assessed. The results roughly show an increased iron dissolution with increasing reactive sites (decreasing particle size: wool > filings > nails), but there were large differences between materials from the same group. The main output of this work is that available results are hardly comparable as they were achieved under very different experimental conditions. A conceptual framework is presented for future research directed towards a more processed understanding.
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      How One Rural Community in Transition Overcame Its Island Status: The Case of Heckenbeck, Germany 

      Grewer, Janes; Keck, Markus
      Sustainability 2019; 11(3): Art. 587
      In the public debate, sustainable innovations are mostly associated with urban contexts, whereas rural areas are rarely seen as potentially creative sites. In contrast to this widespread suggestion, however, recent studies show that rural communities can also play a pivotal role in generating sustainable solutions. Yet, the transformative potentials of villages often remain socially limited to pioneers’ personal networks and spatially restricted to insulated places. In this context the question arises of how rural communities in transition to sustainability can overcome their island-status to develop transformative potentials. In order to answer this question, we take the example of Heckenbeck, a village located in southern Lower Saxony (Germany), as a case and examine the social interactions and networks that exist between local sustainability niches and the socio-technical regime. By applying socio-technical transition theory in a multi-scalar perspective, our study illustrates how a group of niche actors has accomplished to effectively transform the local regime by spreading their ideas among their fellow village members and to put pressure on the regional regime by using windows of opportunity created in the socio-technical landscape to build multifaceted social networks to various sectors of society. The case provides lessons learnt and discusses possibilities and limits to transfer these lessons to other contexts.
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      Defeating Fluorosis in the East African Rift Valley: Transforming the Kilimanjaro into a Rainwater Harvesting Park 

      Marwa, Janeth; Lufingo, Mesia; Noubactep, Chicgoua; Machunda, Revocatus
      Sustainability 2018; 10(11): Art. 4194
      The high availability of fluoride in surface and groundwater in the East African Rift Valley was documented during the colonial period. Since the early 1960s, many studies have been conducted to solve the fluorosis crisis in this region. At present, no cost-effective solution to mitigate fluoride contamination is available for the large majority of the population. This situation prompted a process analysis of commonly used technologies. Results revealed that the geochemistry of fluoride is the main problem. Fluoride is very difficult to remove from the aqueous phase. Thus, eliminating the need for technical water defluoridation is an excellent way out of the fluorosis crisis. This goal can be achieved by harvesting fluoride-free rainwater. Harvested rainwater can be mixed with naturally polluted waters in calculated proportions to obtain safe drinking water (blending). This paper presents a concept to transform the Kilimanjaro Mountains into a huge rainwater harvesting park for drinking water supply for the whole East African Rift Valley. However, blended water may contain other pollutants including pathogens that are easy to treat using low-cost methods such as metallic iron based-filters (Fe0 filters). The proposed concept is transferable to other parts of the world still enduring fluoride pollution.
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    • Journal Article

      Fe0/H2O Systems for Environmental Remediation: The Scientific History and Future Research Directions 

      Hu, Rui; Cui, Xuesong; Gwenzi, Willis; Wu, Shuanghong; Noubactep, Chicgoua
      Water 2018; 10(12): Art. 1739
      Elemental iron (Fe0) has been widely used in groundwater/soil remediation, safe drinking water provision, and wastewater treatment. It is still mostly reported that a surface-mediated reductive transformation (direct reduction) is a dominant decontamination mechanism. Thus, the expressions “contaminant removal” and “contaminant reduction” are interchangeably used in the literature for reducible species (contaminants). This contribution reviews the scientific literature leading to the advent of the Fe0 technology and shows clearly that reductive transformations in Fe0/H2O systems are mostly driven by secondary (FeII, H/H2) and tertiary/quaternary (e.g., Fe3O4, green rust) reducing agents. The incidence of this original mistake on the Fe0 technology and some consequences for its further development are discussed. It is shown, in particular, that characterizing the intrinsic reactivity of Fe0 materials should be the main focus of future research.
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    • Journal Article

      Iron Corrosion: Scientific Heritage in Jeopardy 

      Hu, Rui; Noubactep, Chicgoua
      Sustainability 2018; 10(11): Art. 4138
      Research on the use of metallic iron (Fe0) for environmental remediation and water treatment has taken off during the past three decades. The results achieved have established filtration on Fe0 packed beds as an efficient technology for water remediation at several scales. However, the further development of Fe0-based filtration systems is impaired by the non-professional behavior of scientists who ignore available advances in knowledge. The confusion is overcome when due consideration is given to the fact that revealing state-of-the-art knowledge is a prerequisite to presenting individual achievements.
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