Study of enzyme-catalysed and noncatalysed interactions between soil humic acid and C-labelled 2-aminobenzothiazole using solid-state C NMR spectroscopy

Chemical interactions between 2-aminobenzothiazole (ABT) and a soil humic acid (HA) extracted from a gleyic planosol were investigated by solid-state ¹³C CP/MAS NMR spectroscopy. Reactions of the HA with ABT ¹³C-labelled at the C-2 position were performed in aqueous solution under noncatalysed and enzyme-catalysed conditions. Without enzymic catalysis the amount of ABT-2-¹³C taken up by soil HA in an oxygen atmosphere was about twice the uptake under argon. In the presence of the oxidative enzyme laccase and air, about three times as much ABT was bound to HA as compared to the uptake in a control experiment with inactivated laccase. The results suggest that oxidation reactions of the humic acid significantly enhance the extent of binding between ABT and HA. The ¹³C NMR spectra of the HA–ABT adducts indicated that in both noncatalysed and enzyme-catalysed reactions ABT may be bound to humic acid by noncovalent as well as covalent bonds.     

Regional review: the hydrology of the Okavango Delta, Botswana—processes, data and modelling

The wetlands of the Okavango Delta accommodate a multitude of ecosystems with a large diversity in fauna and flora. They not only provide the traditional livelihood of the local communities but are also the basis of a tourism industry that generates substantial revenue for the whole of Botswana. For the global community, the wetlands retain a tremendous pool of biodiversity. As the upstream states Angola and Namibia are developing, however, changes in the use of the water of the Okavango River and in the ecological status of the wetlands are to be expected. To predict these impacts, the hydrology of the Delta has to be understood. This article reviews scientific work done for that purpose, focussing on the hydrological modelling of surface water and groundwater. Research providing input data to hydrological models is also presented. It relies heavily on all types of remote sensing. The history of hydrologic models of the Delta is retraced from the early box models to state-of-the-art distributed hydrological models. The knowledge gained from hydrological models and its relevance for the management of the Delta are discussed.     

Landslide impacts in Germany: A historical and socioeconomic perspective

Landslide impacts on infrastructure and society in the Federal Republic of Germany are associated with damage costs of about US$300 million on annual average. Despite the large overall losses due to widespread landslide activity, there is a lack of historical impact assessments, not just for Germany’s low mountain areas but those of entire Central Europe as well. This paper is a collection of three case studies from Germany that seek a better understanding of landslide impacts and their economic relevance at local and regional level. The first case study investigates damage types and mitigation measures at a representative landslide site in ways that support to gain insight into historical hazard interactions with land use practices. This case history is followed by a case study dealing with fiscal cost impacts of landslide damages for an example city and the highway system of the Lower Saxon Uplands, NW Germany. In addition to a cost-burden analysis for affected public budgets, an overview of the principles of disaster financing in landslide practice is given. The third case study is focused on the conflicts of urban development in hazard areas, with an economic approach to balancing safety and public welfare interests. Each case study is based on historical data sets extracted from Germany’s national landslide database. This paper presents three different case studies that in combination are a first step towards assessing landslide impacts in integrated perspective.     

Geochemistry of Peruvian near-surface sediments

Sixteen short sediment cores were recovered from the upper edge (UEO), within (WO) and below (BO) the oxygen minimum zone (OMZ) off Peru during cruise 147 of R/V Sonne. Solids were analyzed for major/trace elements, total organic carbon, total inorganic carbon, total sulfur, the stable sulfur isotope composition (δ³⁴S) of pyrite, and sulfate reduction rates (SRR). Pore waters were analyzed for dissolved sulfate/sulfide and δ³⁴S of sulfate. In all cores highest SRR were observed in the top 5 cm where pore water sulfate concentrations varied little due to resupply of sulfate by sulfide oxidation and/or diffusion of sulfate from bottom water. δ³⁴S of dissolved sulfate showed only minor downcore increases. Strong ³²S enrichments in sedimentary pyrite (to −48‰ vs. V-CDT) are due to processes in the oxidative part of the sulfur cycle in addition to sulfate reduction. Manganese and Co are significantly depleted in Peruvian upwelling sediments most likely due to mobilization from particles settling through the OMZ, whereas release of both elements from reducing sediments only seems to occur in near-coastal sites. Cadmium, Mo and Re are exceptionally enriched in WO sediments (<600 m water depth). High Re and moderate Cd and Mo enrichments are seen in BO sediments (>600 m water depth). Re/Mo ratios indicate anoxic and suboxic conditions for WO and BO sediments, respectively. Cadmium and Mo downcore profiles suggest considerable contribution to UEO/WO sediments by a biodetrital phase, whereas Re presumably accumulates via diffusion across the sediment-water interface to precipitation depth. Uranium is distinctly enriched in WO sediments (due to sulfidic conditions) and in some BO sediments (due to phosphorites). Silver transfer to suboxic BO sediments is likely governed by diatomaceous matter input, whereas in anoxic WO sediments Ag is presumably trapped due to sulfide precipitation. Cadmium, Cu, Zn, Ni, Cr, Ag, and T1 predominantly accumulate via biogenic pre-concentration in plankton remains. Rhenium, Sb, As, V, U and Mo are enriched in accordance with seawater TE availability. Lead and Bi enrichment in UEO surface sediments is likely contributed by anthropogenic activity (mining). Accumulation rates of TOC, Cd, Mo, U, and V from Peruvian and Namibian sediments exceed those from the Oman Margin and Gulf of California due to enhanced preservation off Peru and Namibia.     

Tonian to early Cryogenian synorogenic basin of the São Gabriel Terrane,Dom Feliciano Belt,southernmost Brazil

A provenance and stratigraphic study of the Neoproterozoic Pontas do Salso Complex (PSC), western portion of the Dom Feliciano Belt (DFB), was conducted with U–Pb zircon geochronological analysis of the metasediments and the host rocks. The U–Pb isotopic data from detrital zircon of the metasediments indicate the source from the latest Middle Tonian to Late Cryogenian (between 897 and 684 Ma) and maximum depositional age of 685 ± 18 Ma in an arc-related basin setting adjacent in the Sao Gabriel Arc. The metasediments of the PSC form an elongated body in the N35°E direction and occur in the central portion of the São Gabriel Terrane (SGT), which is constituted by ophiolitic complexes and arc-related rocks, generated probably during the final consolidation of Rodinia supercontinent, although this question is still open. Low- to medium-K calc-alkaline, metaluminous affinity, and trace-element geochemistry suggest that the chemical composition of the protoliths was generated from metasomatized mantle sources in subduction zones. The PSC is composed of meta-arkoses, with subordinate metaconglomerates and metapelites. The meta-arkoses are disposed in plane-parallel layers, which also internally feature small-scale cross-bedding structures. The matrix has a blastopsammitic, poorly selected, fine to coarse texture, and hexagonal quartz and plagioclase porphyroclasts with superimposed thermal metamorphism. The polymict metaconglomerates are matrix-supported, with 15–55% of clasts of metavolcanic rocks, metasediments, undeformed granites, and quartz veins. The metapelites comprise mainly muscovite phyllites with syn-tectonic garnet and chloritoid porphyroblasts. The PSC represents a sedimentary succession deposited on an arc-related basin formed during the collapse and uplift of the SGT.     

Sedimentology of a Late Quaternary lacustrine record from the south-eastern Carpathian Basin

The Upper Pleistocene geoarchives in the south-eastern Carpathian Basin are represented predominantly by loess–palaeosol records. In 2015, a 10 m sediment core composed of clay-rich lacustrine sediments was recovered by vibracoring a dry lake basin located between the Vršac Mountains (Serbia) and the Banat Sands in the south-eastern Carpathian Basin; a location relevant for placing regional archaeological results in a palaeoenvironmental context. Here, we present results from geoelectrical prospection and a lithostratigraphic interpretation of this sequence supported by a detailed granulometric study supplemented by ostracod analysis. An age model based on luminescence dating is discussed against sedimentological proxy data and its implication for palaeoenvironmental change. The cores show a stratigraphy of lighter ochre-coloured and darker greyish sediment, related to the deposition of clay and silt trapped in an aquatic environment. Geophysical measurements show ~20 m thick lacustrine sediments. The grain-size distributions including the variability in fine clay are indicative of a lacustrine environment. Fine particles were brought into the depositional environments by aquatic input and settled from suspension; also, direct dust input is constrained by grain-size results. Riverine input and aeolian dust input interplayed at the locality.     

Bacterial tetraether membrane lipids in peat and coal: Testing the MBT-CBT temperature proxy for climate reconstruction

Peatlands are widespread and important natural archives of environmental change. Here we explore the potential of the recently introduced MBT-CBT proxy (methylation index and cyclisation ratio of branched tetraethers) to estimate past annual mean air temperature (MAT) based on the distribution of bacterially-derived branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in peat and coal. To this end, branched GDGTs in an ombrotrophic peat bog from Switzerland and three coal deposits of increasing maturity were analysed.For the surface of the bog, reconstructed annual MAT is higher than both measured annual MAT and measured in situ pore water temperature. Changes in the CBT ratio, considered a proxy for pH, with depth in the bog do not match with present day in situ pore water pH, but coincide with a peat stratigraphic boundary. This indicates that GDGTs down the bog profile are predominantly fossil and not derived from extant biomass. The MBT-CBT derived annual MAT record also shows a large drop at this stratigraphic boundary, which likely relates to past change in trophic status of the bog. Branched GDGTs are abundant in an immature lignite (vitrinite reflectance, R_o 0.25%), but occur in low amount in a slightly more mature coal (R_o 0.32%). Annual MAT could be reconstructed for the lignite alone and is higher than other proxy-based estimates from approximately the same time and location.Our results indicate potential for the application of the MBT-CBT proxy in peat and immature coals, but improved constraints on the effects of different types of peat on branched GDGT distributions as well as improved calibration of MAT estimates are needed before the method can be confidently applied.