Predictive modelling of rainfall-induced landslide hazard in the Lesser Himalaya of Nepal based on weights-of-evidence

Landslide hazard mapping is a fundamental tool for disaster management activities in mountainous terrains. The main purpose of this study is to evaluate the predictive power of weights-of-evidence modelling in landslide hazard assessment in the Lesser Himalaya of Nepal. The modelling was performed within a geographical information system (GIS), to derive a landslide hazard map of the south-western marginal hills of the Kathmandu Valley. Thematic maps representing various factors (e.g., slope, aspect, relief, flow accumulation, distance to drainage, soil depth, engineering soil type, landuse, geology, distance to road and extreme one-day rainfall) that are related to landslide activity were generated, using field data and GIS techniques, at a scale of 1:10,000. Landslide events of the 1970s, 1980s, and 1990s were used to assess the Bayesian probability of landslides in each cell unit with respect to the causative factors. To assess the accuracy of the resulting landslide hazard map, it was correlated with a map of landslides triggered by the 2002 extreme rainfall events. The accuracy of the map was evaluated by various techniques, including the area under the curve, success rate and prediction rate. The resulting landslide hazard value calculated from the old landslide data showed a prediction accuracy of > 80%. The analysis suggests that geomorphological and human-related factors play significant roles in determining the probability value, while geological factors play only minor roles. Finally, after the rectification of the landslide hazard values of the new landslides using those of the old landslides, a landslide hazard map with > 88% prediction accuracy was prepared. The methodology appears to have extensive applicability to the Lesser Himalaya of Nepal, with the limitation that the model's performance is contingent on the availability of data from past landslides.     

Revisiting the stratigraphy of the Mesoproterozoic Chhattisgarh Supergroup,Bastar craton,India based on subsurface lithoinformation

In the last 10 years, several teams of geologists from different institutions in India and abroad have vigorously investigated the Chhattisgarh basin (Bastar craton, India). Based on the new results and the lithologs of more than 350 water wells, resistivity and gamma-ray logs, and extensive geological traverses, we present a revised geological map, relevant cross sections, a new comprehensive stratigraphic column and a discussion of the new findings. Major outcomes of this revision are: (1) confirming the existence of two sub-basins (Hirri and Baradwar) and two depocentres; (2) establishing the age of the basin to be essentially Mesoproterozoic; (3) discarding the ‘unclassified Pandaria Formation’ and classifying the package of Pandaria rock units into Chandi, Tarenga, Hirri and Maniari formations in the Hirri sub-basin; (4) accepting the ‘group’ status of the Singhora Group and the newly proposed Kharsiya Groups in the Baradwar sub-basin; (5) establishing an intrabasinal correlation of formations; (6) reappraising the thicknesses of the different formations; and (7) finding that the geometry of the basin is ‘bowl-shaped’, which is compatible with a sag model for the origin and evolution of the basin.     

Modified biomass of Phanerochaete chrysosporium immobilized on luffa sponge for biosorption of hexavalent chromium

Phanerochaete chrysosporium, a white rot basidiomycete, was immobilized over Luffa cylindrica sponge discs, treated with 0.1 N HCl and its potentiality for the removal of hexavalent chromium [Cr(VI)] from water was investigated in both batch and in up-flow fixed-bed bioreactor. The acid treatment of biomass increased the uptake capacity and percentage removal of Cr(VI) from 33.5 to 46.5 mg g^?1 and 67 to 92 %, respectively. Maximum uptake of Cr(VI) was achieved at pH 2, temperature 40 °C after 100 min of contact time. The Cr(VI) sorption on the biomass was better explained by Langmuir isotherm. Thermodynamic studies indicated that the process was spontaneous and endothermic. Sorption kinetic study showed that pseudo-second-order model best correlates the Cr(VI) sorption on the biomass as compare to pseudo-first-order kinetic model. The performance of fixed-bed bioreactor was evaluated at different bed heights (5, 15 and 25 cm) and flow rates (1.66, 4.98 and 8.33 mL min^?1) by using bed depth service time model. Response surface methodology statistical method was applied for optimizing the process parameters. FTIR analysis showed that amino groups were mainly involved in adsorption of Cr(VI).     

Bulk organic matter characteristics in the Pichavaram mangrove – estuarine complex,south-eastern India

The Pichavaram mangrove ecosystem is located between the Vellar and Coleroon Estuaries in south-eastern India. To document the spatial-depth-based variabilities in organic matter (OM) input and cycling, five sediment cores were collected. A comparative study was carried out of grain-size composition, pore water salinity, dissolved organic C (DOC), loss-on-ignition (LOI), elemental ratios (C/N and H/C), pigments (Chl a, Chl b, and total carotenoids), and humification indices. Sand is the major fraction in these cores ranging from 60% to 99% followed by silt and clay; cores from the estuarine margin have high sand content. In mangrove forests, pore-water DOC concentrations are high (32 ± 14 mg L⁻¹), whereas salinity levels are low (50 ± 5.5‰). Likewise, LOI, organic C and N, and pigment concentrations are high in mangroves. OM is mainly derived from upstream terrestrial matter and/or mangrove litter, and marine OM. The humification indices do not vary significantly with depth because of rapid OM turnover. The bulk parameters indicate that the Vellar and Coleroon Estuaries are more affected by anthropogenic processes than mangrove forests. Finally, greater variability and sometimes lack of specific trends in bulk parameters implies that the 2004 tsunami caused extensive mixing in sediments.