Driftwood deposition from debris flows at slit-check dams and fans

Experience shows that debris flows containing large woody debris (driftwood) can be more damaging than debris flows without driftwood. In this study, the deposition process of debris flows carrying driftwood was investigated using numerical simulations and flume experiments. Debris-flow trapping due to driftwood jamming in a slit-check dam was also investigated. A numerical model was developed with an interacting combination of Eulerian expression of the debris flow and Lagrangian expression of the driftwood, in which the fluctuating coordinates and rotation of the driftwood were treated stochastically. The calculated shapes and thicknesses of a debris-flow fan and the positions and orientations of the deposited driftwood on a debris-flow fan were consistent with experimental flume results. The jamming of driftwood in a slit-check dam was evaluated based on geometry and probability. The simulated results of outflow discharge and the proportion of driftwood passed through the slit-check dam also agreed with the experimental results.     

Numerical simulation and optimization of CO2 sequestration in saline aquifers for vertical and horizontal well injection

With heightened concerns on CO₂ emissions from pulverized-coal (PC) power plants, there has been major emphasis in recent years on the development of safe and economical geological carbon sequestration (GCS) technology. Saline aquifers are considered very attractive for GCS because of their large storage capacity in U.S. and other parts of the world for long-term sequestration. However, uncertainties about storage efficiency as well as leakage risks remain major areas of concern that need to be addressed before the saline aquifers can be fully exploited for carbon sequestration. A genetic algorithm-based optimizer has been developed and coupled with the well-known multiphase numerical solver TOUGH2 to optimally examine various injection strategies for increasing the CO₂ storage efficiency as well as for reducing its plume migration. The optimal injection strategies for CO₂ injection employing a vertical injection well and a horizontal injection well are considered. To ensure the accuracy of the results, the combined hybrid numerical solver/optimizer code was validated by conducting simulations of three widely used benchmark problems employed by carbon sequestration researchers worldwide. The validated code is then employed to optimize the proposed water-alternating-gas injection scheme for CO₂ sequestration using both the vertical and the horizontal injection wells. The results suggest the potential benefits of CO₂ migration control and dissolution. The optimization capability of the hybrid code holds a great promise in studying a host of other problems in GCS, namely how to optimally enhance capillary trapping, accelerate the dissolution of CO₂ in water or brine, and immobilize the CO₂ plume.     

Hydrogeochemical parameters for assessment of groundwater quality in a river sub-basin

Hydrogeochemical studies were carried out in the Ghataprabha River sub-basin to assess the quality and suitability of groundwater for domestic and irrigation purposes. In the present study, an integrated, geophysical and chemical investigation was carried out in the basaltic terrain. Groundwater samples were collected covering the entire major hydrogeological environment for one hydrological cycle. Comparison of the groundwater quality in relation to drinking water quality standards proves that most of the water samples are not suitable for drinking. Chemical indices such as sodium percentage, sodium adsorption ratio and chloroalkaline indices used for evaluating the water quality for irrigation suggest that the majority of the groundwater samples were good for irrigation. Positive values of 74% of groundwater samples indicated the absence of base exchange reaction (chloroalkaline disequilibrium) and negative ratio of 26% samples indicated a base exchange reaction (chloroalkaline equilibrium). Resistivity tomography studies revealed that the high concentration of total dissolved solids, chloride and sodium were due to the local anthropogenic activities and weathering of basalt rocks.     

Role of intra-seasonal oscillations in modulating Indian summer monsoon rainfall

The day-to-day behavior of Indian summer monsoon rainfall (IMR) is associated with a hierarchy of quasi-periods, namely 3?C7, 10?C20 and the 30?C60?days. These two periods, the 10?C20?days and the 30?C60?days have been related with the active and break cycles of the monsoon rainfall over the Indian sub-continent. The seasonal strength of Indian summer monsoon rainfall may depend on the frequency and duration of spells of break and active periods associated with the fluctuations of the above intra-seasonal oscillations (ISOs). Thus the predictability of the seasonal (June through September) mean Indian monsoon depends on the extent to which the intra-seasonal oscillations could be predicted. The primary objective of this study is to bring out the dynamic circulation features during the pre-monsoon/monsoon season associated with the extreme phases of these oscillations The intense (weak) phase of the 10?C20 (30?C60) days oscillation is associated with anti-cyclonic circulation over the Indian Ocean, easterly flow over the equatorial Pacific Ocean resembling the normal or cold phase (La Nina) of El Nino Southern Oscillation (ENSO) phenomenon, and weakening of the north Pacific Sub-tropical High. On the other hand the weak phase of 10?C20?days mode and the intense phase of 30?C60?days mode shows remarkable opposite flow patterns. The circulation features during pre-monsoon months show that there is a tendency for the flow patterns observed in pre-monsoon months to persist during the monsoon months. Hence some indications of the behavior of these modes during the monsoon season could be foreshadowed from the spring season patterns. The relationship between the intensity of these modes and some of the long-range forecasting parameters used operationally by the India Meteorological Department has also been examined.     

Paleoproterozoic quartz-pebble conglomerate type uranium mineralisation in Mankarhachua area,Angul district,Orissa

Ground Radiometric survey of Paleoproterozoic pyritiferous quartz-pebble conglomerate (QPC) occurring to the north of Pallahara area led to the discovery of a QPC type uranium mineralisation near Mankarhachua village. Significant radioactivity is recorded in three sub-parallel uraniferous QPC horizons with metamorphosed pebbly to medium grained recrystallised massive sandstones. Detrital grains of uranothorite, thorite, radioactive allanite, monazite, zircon, minute uraninite grains in carbonaceous matter and thucolite contributes to the radioactive phases present in QPC matrix. Adsorbed U on limonite and goethite, secondary uranyl minerals in matrix, along bedding planes and fractures are commonly observed. This discovery has opened up a new horizon for future exploration for QPC type uranium mineralization in the area. The paper presents observations on geology, radioactivity, petrological and geochemical nature of the uraniferous QPC horizons.     

Assessment of groundwater contamination from a hazardous dump site in Ranipet, Tamil Nadu, India

Tanneries located in an industrial development area of Ranipet (India) manufactured chromate chemicals during 1976?C1996. A large quantity of associated hazardous solid wastes has been stacked about 5-m high above ground level, spread over 3.5?ha inside one of the factory premises. The study area receives an average annual rainfall of 1,100?mm. The granitic formation in the northern part of Palar River catchment has high infiltration rates and has resulted in fast migration of the contamination to the water table. Chromium levels in the groundwater were found up to 275?mg/l. The available hydrogeological, geophysical and groundwater quality data bases have been used to construct a groundwater flow and mass transport model for assessing the groundwater contamination and it has been calibrated for the next 30?years. The migration has been found to be very slow, with a groundwater velocity of 10?m/year. This is the first field-scale study of its kind in this industrial area. The findings are of relevance to addressing the groundwater pollution due to indiscriminate disposal practices of hazardous waste in areas located on the phreatic aquifer. Further, it has been reported that the untreated effluent discharge adjacent to the chromium dump site is most influential in the migration of contaminants.     

Anthropogenic platinum,palladium and rhodium concentrations in road dusts from Hyderabad city,India

This paper presents the first study of accessing the Pt, Pd and Rh levels in road dusts collected from Hyderabad city, India, as these metals, emitted from automobile catalytic converters, are accumulating in the environment causing concern about human health and ecological risks. Samples were analyzed by ICP-MS following preconcentration by NiS-fire assay and Te coprecipitation. Pt (1.5–43 ng/g), Pd (1.2–58 ng/g) and Rh (0.2–14.2 ng/g) concentrations obtained were above upper crust values, but were lower when compared with several other cities around the world. Dust samples from road junctions and traffic signals with heavy and erratic traffic flow showed higher PGE levels than those from roads with low and free flow traffic suggesting that traffic flow conditions greatly influenced emission of PGE from the catalyst. Significant correlation of Pt, Pd and Rh indicate a common source for these metals. PGE were also positively correlated with Ce, Zr, Hf and Y. These positive inter-element correlations identified traffic as the main source of PGE emission to the roadway environment. The results obtained indicate to an appreciable increase in auto catalyst-derived PGE. In consideration of the adverse effects of PGE, monitoring their level and transformation paths is of prime importance.     

Nitrogen sources for new production in the NE Arabian Sea

New productivity measurements using the ¹⁵N tracer technique were conducted in the north-eastern (NE) Arabian Sea during six expeditions from 2003 to 2007, mostly in winter. Our results indicate that the NE Arabian Sea has a potential for higher new productivity during blooms. Nitrate uptake by plankton is the highest during late winter. New productivity and f-ratios in the NE Arabian Sea are mainly controlled by hydrodynamic and meteorological parameters such as wind strength, sea surface temperature (SST), mixed layer depth (MLD) and mixed layer nitrate. Deepening of the mixed layer supplies nitrate from below, which supports the observed nitrogen uptake. Higher f-ratios during blooms indicate the strong coupling between surface layers and sub-surface layers. Deepening of mixed layer below 100 m (from its inter-monsoon value between 30 and 40 m) transferred often more than 100 mmol N–NO₃ m^? 2 into the surface layers from below. The observed winter blooms in the region are supported by such input and are sustained for more than a month. Higher new productivity has been found in late winter, whereas transport of nitrate is maximum in early winter. In general, new production varies progressively during winter. Diurnal cycling of the mixed layer could be the reason for the under utilization of entrained nitrate during early winter. New productivity values and wind strength show significant differences during Feb–Mar 03 and Feb–Mar 04. These differences indicate that the winter cooling and parameters related the biological productivity also vary inter-annually. However, the difference between the new productivity values between Feb–Mar 03 and Feb–Mar 04 is much lower than the difference between Jan 03 and Feb–Mar 03. The results suggest that amplitude of seasonal variation is higher than the inter-annual variation in the region. During spring, Fickian diffusive fluxes of nitrate into the surface layer range from 0.51 to 1.38 mmol N–NO₃ m^? 2 day^? 1, and can account for 67% and 78% of the observed nitrogen uptake in the coastal and open ocean regions, respectively. We document the intra-seasonal and inter-annual variations in new productivity during winter and identify sources of nitrate which support the observed productivity during spring.     

Bastnaesite from Kanigiri granite, Prakasam district, Andhra Pradesh

For the first time we report bastnaesite and hydroxyl bastnaesite (lanthanum cerium fluoro-carbonate) from the Kanigiri granite. The host granitoids are of A-type and vary in composition from quartz syenites to peralkaline granites. Rare metal and rare earth-bearing minerals identified by X-ray diffraction (XRD) studies in Kanigiri granite are bastnaesite and hydroxyl bastnaesite, besides columbite-tantalite, monazite, fergusonite, thorite and euxenite. Petromineralogical studies have also revealed the presence of bastnaesite. The presence of bastnaesite in Kanigiri granite suggests that the host felsic rocks may also form a potential source for light rare earth mineral, bastnaesite, apart from the already known rare-metal minerals.     

Signature of potassium enrichment in granite of the Chitrial area, Nalgonda district, Andhra Pradesh: Inferences using its U, Th, K2O, Na2O, Rb, Ba and Sr contents

A medium tonnage unconformity proximal uranium deposit has been established at Chitrial by the Atomic Minerals Directorate in the Srisailam sub-basin. In this type of deposits, the association of uranium with potassic alteration (illitization) is well-documented. The present study is directed towards understanding such an association in the Chitrial area for which the uranium mineralized borehole core samples were collected and analyzed. It is observed that the average concentrations of K₂O, Na₂O, Rb, Ba and Sr in the granite of the Chitrial area are 5.35%, 1.78%, 252 ppm, 564 ppm and 52 ppm, respectively, and they show average critical elemental ratios of K/Rb, Ba/Rb and Rb/Sr as 191, 2.37 and 7.13, respectively. The granites show low K/Rb, low Rb/Ba and high Rb/Sr ratios compared to that of the average crust indicating its derivation from crustal source. The samples have higher values of uranium (av. 53 ppm), thorium (av. 66 ppm) and lead (av. 41 ppm). The U/Th ratio in the granite varies from 0.07 to 20.86 with an average of 1.68. They also exhibit high K₂O/Na₂O ratio typical of post-Archaean granite and very high values suggest the possibility of later potassium enrichment.