Felsic tuff from Rutland Island — A pyroclastic flow deposit in Miocene-sediments of Andaman-Java subduction complex

The bedded felsic tuff exposed in Rutland Island, Andaman, consists of two facies:

Dissolved Boron in the Tapi,Narmada and the Mandovi Estuaries,the Western Coast of India: Evidence for Conservative Behavior

The concentrations of dissolved boron have been measured during different seasons in three estuaries, the Tapi, Narmada and the Mandovi situated on the western coast of India, to investigate its geochemical behavior and inputs from the localized anthropogenic pressures of industrial effluents and sewage discharge. The measured boron concentrations in these estuaries (except the Tapi during non-monsoon) at salinity ≤0.1 fall in a narrow range?～?2–4 μmol/kg (average B?～?2.4?±?0.8 μmol/kg) within the reported wide range?～?0.1–18.6 μmol/kg for global rivers. The much higher estimate of boron concentration in the Tapi River during non-monsoon is attributed to its possible additional supply from the sewage and/or industrial effluents discharged along the river course. During monsoon, the rains seem to be a significant source of dissolved boron to all the three rivers. The distribution of dissolved boron in each estuary exhibits a conservative behavior during the seasons sampled suggestive of no measurable addition or removal of boron in the estuarine region. The orders of magnitude differences in boron concentration between the river waters and seawater, and the conservative behavior of dissolved boron indicate that its major contributor to the estuaries sampled is seawater.     

Nonlinear kinetic analysis of phenol adsorption onto peat soil

Phenolic compounds are considered as a serious organic pollutant containing in many industrial effluents particularly vulnerable when the plant discharge is disposed on land. In the present study, the phenol removal potential of peat soil as adsorption media was investigated as the adsorption process are gaining popular for polishing treatment of toxic materials in industrial wastewater. Batch experiments were performed in the laboratory to determine the adsorption isotherms of initial concentrations for 5, 8, 10, 15, and 20 mg/L and predetermined quantity of peat soil with size ranges between 425 and 200 μm poured into different containers. The effects of various parameters like initial phenol concentration, adsorbent quantity, pH, and contact time were also investigated. From experimental results, it was found that 42 % of phenol removal took place with optimized initial phenol concentration of 10 mg/L, adsorbent dose of 200 g/L, solution pH 6.0 for the equilibrium contact time of 6 h. The result exhibits that pseudo-first-order (R ² = 0.99) and Langmuir isotherm models are fitted reasonably (R ² = 0.91). Adams–Bohart, Thomas, Yoon–Nelson, and Wolborska models were also investigated to the column experimental data of different bed heights to predict the breakthrough curves and to determine the kinetic coefficient of the models using nonlinear regression analysis. It was found that the Thomas model is the best fitted model to predict the experimental breakthrough curves with the highest coefficient of determination, R ² = 0.99 and lowest root mean square error and mean absolute performance error values.     

Petrogenesis of chromites from the Manipur ophiolite belt,NE India: evidence for a supra-subduction zone setting prior to Indo-Myanmar collision

The Manipur ophiolite belt within the Western Ophiolite Belt of the Indo-Myanmar Ranges (IMR), consists of tectonised to massive serpentinised peridotite, dunite pods, chromitite pods/lenses, cumulates, dykes, volcanic rocks and pelagic sediments. Chromitite pods and lenses hosted in peridotitic mantle rocks show magmatic textures, post magmatic brecciation and ferritchromitisation. Electron microprobe analyses show two types of massive chromitite, with one group having high-Cr (Cr# 75–76), medium-Al (Al₂O₃ 12.2–12.4 wt%) chromites (Sirohi-type) and the other group (Gamnom-type) having a wide range of compositions with generally lower Cr and higher Al (Cr# 65–71, Al₂O₃ 15.7–19 wt%). Accessory chromites in peridotitic mantle rocks have consistently low Cr (Cr# 38–39) and high Al (Al₂O₃ 34–35 wt%), whereas chromites in dunite pods have intermediate compositions (Cr# ~60; Al₂O₃ 20.7–21.2 wt%). The chromite chemistry suggests moderate (20 %) partial melting of the tectonised mantle harzburgite. The estimated Al₂O_3melt, (FeO/MgO)_melt and TiO_2melt for the Sirohi-type chromites indicate boninitic parentage, whereas chromite compositions from the Gamnom area suggest mixed boninitic—island arc tholeiitic magmas. The compositions of magmatic chromites suggest that the Manipur ophiolite was formed in a supra-subduction zone (SSZ) setting.     

Analysis of plasma and field conditions during some intensely geo-effective transient solar/interplanetary disturbances of solar cycle 23

The problem of solar wind-magnetosphere coupling is investigated for intense geomagnetic storms (Dst < -100nT) that occurred during solar cycle 23. For this purpose interplanetary plasma and field data during some intensely geo-effective transient solar/interplanetary disturbances have been analysed. A geomagnetic index that represents the intensity of planetary magnetic activity at subauroral latitude and the other that measures the ring current magnetic field, together with solar plasma and field parameters (V, B, Bz, σB, N, and T) and their various derivatives (BV,-BVz, BV², -BzV², B²V, Bz²V, NV²) have been analysed in an attempt to study mechanism and the cause of geo-effectiveness of interplanetary manifestations of transient solar events. Several functions of solar wind plasma and field parameters are tested for their ability to predict the magnitude of geomagnetic storm.     

Field based index of flood vulnerability(IFV): A new validation technique for flood susceptible models

The flood hazard management is one of the major challenges in the floodplain regions worldwide. With the rise in population growth and the spread of infrastructural development, the level of risk has increased over time.Therefore, the prediction of flood susceptible area is a key challenge for the adoption of management plans.Flood susceptibility modeling is technically a common work, but it is still a very tough job to validate flood susceptible models in a very rigorous and scientific manner. Therefore, the present work in the Atreyee River Basin of India and Bangladesh was planned to establish artificial neural network(ANN), radial basis function(RBF), random forest(RF) and their ensemble-based flood susceptibility models. The flood susceptible models were constructed based on nine flood conditioning parameters. The flood susceptibility models were validated in a conventional way using the receiver operating curve(ROC). To validate the flood-susceptible models, a two dimensional(2 D) hydraulic flood simulation model was developed. Also, the index of flood vulnerability model was developed and applied for validating the flood susceptible models, which was a very unique way to validate the predictive models. Friedman test and Wilcoxon Signed rank test were employed to compare the generated flood susceptible models. Results showed that 11.95%–12.99% of the entire basin area(10188.4 km2) comes under very high flood-susceptible zones. Accuracy evaluation results have shown that the performance of ensemble flood susceptible models outperforms other standalone machine learning models. The flood simulation model and IFV model were also spatially adjusted with the flood susceptibility models. Therefore, the present study recommended for the ensemble flood susceptibility prediction and IFV based validation along with conventional ways.     

Land surface coupling in regional climate simulations of the West African monsoon

Coupling of the Community Land Model (CLM3) to the ICTP Regional Climate Model (RegCM3) substantially improves the simulation of mean climate over West Africa relative to an older version of RegCM3 coupled to the Biosphere Atmosphere Transfer Scheme (BATS). Two 10-year simulations (1992–2001) show that the seasonal timing and magnitude of mean monsoon precipitation more closely match observations when the new land surface scheme is implemented. Specifically, RegCM3–CLM3 improves the timing of the monsoon advance and retreat across the Guinean Coast, and reduces a positive precipitation bias in the Sahel and Northern Africa. As a result, simulated temperatures are higher, thereby reducing the negative temperature bias found in the Guinean Coast and Sahel in RegCM3–BATS. In the RegCM3–BATS simulation, warmer temperatures in northern latitudes and wetter soils near the coast create excessively strong temperature and moist static energy gradients, which shifts the African Easterly Jet further north than observed. In the RegCM3–CLM3 simulation, the migration and position of the African Easterly Jet more closely match reanalysis winds. This improvement is triggered by drier soil conditions in the RegCM3–CLM3 simulation and an increase in evapotranspiration per unit precipitation. These results indicate that atmosphere–land surface coupling has the ability to impact regional-scale circulation and precipitation in regions exhibiting strong hydroclimatic gradients.     

Impact of missing flow on active inundation areas and transformation of parafluvial wetlands in Punarbhaba–Tangon river basin of Indo-Bangladesh

Punarbhaba river of Indo-Bangladesh has experienced hydro-ecological alteration after installation of Komardanga dam in 1992 and consequently wetland and inundation areas have undergone into transformation. The present work intends to explore the impact of flow attenuation on contemporary and upcoming flood extent and flood plain wetlands. In post-dam condition, average and maximum flows are attenuated by 36 and 41%, respectively, and as a result the active flood prone area is squeezed considerably by 39.72%. Average flood water depth is also reduced by 37.87% (4.45metre) after flow modification. Due to shrinkages of flood prone areas, wetland area is also reduced from 215.70 to 90.40 km² and larger part of the present wetland area is under stress and critical state. Predicted flood prone areas in next 25 years will be 328.91 km² and consequently 65.63 km² wetland areas may further be under hydro-ecological threats. Release of ecological flow is essential to restore and preserve the wetland.