Major ion chemistry of two cratonic rivers in the tropics: Weathering rates and their controlling factors

Continental weathering plays a dominant role in regulating the global carbon cycle, soil chemistry and nutrient supply to oceans. The CO₂-mediated silicate weathering acts as a major CO₂ sink, whereas sulphuric acid-mediated carbonate dissolution releases CO₂ to the atmosphere–ocean system. In this study, dissolved major ions and silica concentrations of two tropical (Damodar and Subarnarekha) river systems from India have been measured to constrain the type and rate of chemical weathering for these basins. The total dissolved solids (TDS) of these rivers, a measure of total solute supply from all possible sources, are about 2–3 times higher than that of the global average for rivers. Mass balance calculations involving inverse modelling estimate that 63 ± 11% of total cations are derived from rock weathering, of which 27 ± 7% of cations are supplied through silicate weathering. The sulphide-S concentrations are estimated by comparing the water chemistry of these two rivers with that of a nearby river (Brahmani) with similar lithology but no signatures of sulphide oxidation. The outflows of Damodar and Subarnarekha rivers receive 17% and 55% of SO₄ through sulphide oxidation, respectively. The sulphide oxidation fluxes from the ore mining areas, such as upper Damodar (0.52 × 10⁹ mol/yr) and lower Subarnarekha (0.66 × 10⁹ mol/yr) basins, are disproportionally (~9 times) higher compared to their fractional areal coverage to the global drainage area. The corresponding CO₂ release rate (2.84 × 10⁴ mol/km²/yr) for the Damodar basin is lower by five times than its CO₂ uptake rate (1.38 × 10⁵ mol/km²/yr). The outcomes of this study underscore the dominance of sulphide oxidation in controlling the dissolved chemical (cationic and sulphur) fluxes.     

Submarine Ground Water Discharge Driven by Tidal Pumping in a Heterogeneous Aquifer

Submarine ground water discharge (SGD) is now recognized as an important water pathway between land and sea. It is difficult to quantitatively predict SGD owing to its significant spatial and temporal variability. This study focuses on quantitative estimation of SGD caused by tidally induced sea water recirculation and a terrestrial hydraulic gradient. A two-dimensional hydrogeological model was developed to simulate SGD from a coastal unconfined aquifer in the northeastern Gulf of Mexico, where previous SGD studies were performed. A density-variable numerical code, SEAWAT2000, was applied to simulate SGD. To accurately predict discharge, various influencing factors such as heterogeneity in conductivity, uncertain boundary conditions, and tidal pumping were systematically assessed. The tidally influenced sea water recirculation zone and the fresh water–salt water mixing zone under various tidal patterns, tidal ranges, and water table heights were also investigated. The model was calibrated and validated from long-term, intensive measurements at the study site. The percentage of fresh SGD relative to total SGD ranged from 4% to 50% under normal conditions. Based on simulations of two field measurements in summer and spring, respectively, the fresh water ratios were 9% and 15%, respectively. These results support the hypothesis that the SGD induced by tidally driven sea water recirculation is much larger than terrestrial fresh ground water discharge at this site. The estimates of total and fresh SGD are at the low and high ends, respectively, of the estimation ranges obtained from geochemical tracers (e.g., ²²²Rn).     

新疆旅游资源新评价与开发新方略

新疆幅员广阔,深居内陆,自然复杂,人文多样,是中国旅游资源特丰区。通过组织跨部门,多学科的专家按照《中国旅游资源普查规范》(试行稿)实地考察,对新疆旅游资源的丰度、类型、功能、地域结构给出了新评价,确认它是中国旅游业发展的重要资源后备基地。从新疆地处欧亚大陆腹心,毗邻八国的特殊区位,以及世界旅游重心东移,中国旅游资源开发向内陆推进的多维多元化出发,提出了树立超前意识以市场为导向,深层次,高品位,多元化开发新疆旅游资源的新方略。即确立发展大旅游业的战略观念构建“引爆工程”、“转动效应”的特种旅游、专题旅游和常规旅游项目,完善旅游管理体制,发展以航空运输为主体的综合运输网络,强化旅游软硬件设施,建设能满足不同层次需求、富有特色功能、具有国际意义的国家级旅游地域新网络系统。     

Geotechnical study and slope design of a phosphorite mine

This paper aims at examining how the data for the geomechanical properties of slope material and for groundwater condition can be precisely and quickly collected, evaluated, and best used for optimum slope design in a block of phosphorite in an open cast mine. It is also directed at determining the influence of all the slope design parameters on the safety factor by using sensitivity analysis, which indicates that the effect of groundwater and friction angle is prominent in the slope. Suitable remedial measures, e.g., proper drainage and design of high slopes with relatively safe slope angle, have been planned for the critical slopes after sensitivity analysis. Monitoring of the designed slopes has revealed no movement.     

Barium in Deccan Basalt Rivers: Its Abundance, Relative Mobility and Flux

The concentration of dissolved Ba in a number of rivers having their drainage almost entirely in Deccan Trap basalts has been measured. These results along with available data on the abundances of major elements in these waters, and on Ba and major elements in bed sediments of these rivers provide a measure of (i) the relative mobility of Ba during chemical weathering and erosion of basalts, particularly with respect to alkaline earths, Mg, Ca and Sr, and (ii) the flux of Ba out of the Deccan and its global significance. The concentration of dissolved Ba ranges from 8 to 105 nM. The average Ba/Mg*, Ba/Ca* and Ba/Sr (* is concentration corrected for atmospheric contribution) in waters is lower than the corresponding mean ratios in Deccan basalts, though they overlap within errors. Majority of the water samples, however, have ratios less than that in basalts. These findings can be interpreted as a cumulative effect of limited release/mobility of Ba during chemical weathering and erosion of basalts and its reactive behaviour in waters which promote its association with clays and oxy-hydroxides of Fe. These results also indicate that during chemical erosion of Deccan basalts, Ba is the least mobile among the alkaline earth elements. The abundance of Ba in sediments and their Ba/Al ratios relative to basalts are consistent with the above conclusion. Ba/Mg and Ba/Ca ratios in water and in sediments from the same location are strongly correlated; however, the mean ratios in waters are far less than those in sediments. This is a result of limited Ba mobility, effectively 5–6 times lower than that of Mg. The annual flux of dissolved Ba out of the Deccan Traps is ~1 × 10⁷ moles, ~ 0.2% of its global riverine transport to oceans. The contribution of dissolved Ba from Deccan Traps, seem lower than its aerial coverage, ~ 0.5% of the global drainage area; the potential causes for this could be the lower abundance of Ba in basalts relative to “average continental crust”, and its behaviour during chemical weathering and erosion.     

Resampling routine on heterogeneous networked-based environment

In this paper, we have described a model to parallelize the resampling routine, which is used in the geometric correction of data provided by remote sensing satellites. Our model is a typical master-slave model consisting of N machines termed as hosts out of which one is designated as the master. The input image data resides on the master. Processing of the input image data is done in parallel on the N machines. Issues related to load-balancing and various error conditions that may occur during execution like one of the machines going down have been studied and are incorporated in the model. It also provides the flexibility to add or delete the hosts during the execution of the resampling routine. The serial version of this routine involves huge amount of computations and takes substantial amount of time even for an image of 473 MB. We have implemented our model with the help of PVM which is most often used in distributed computing environment. Our approach has been tested for geometric correction on LISS-III 4 band data of size 473 MB. It is found that if one uses 2, 3 or 4 hosts the overall execution time is reduced by 33%, 42% and 49%, respectively.     

Artificial Neural Network Approach for Reconstruction of Event Arrival-Direction in Wide-Angle Atmospheric Cerenkov Detector Arrays: A Feasibility Study

A feasibility study has been carried out to assess the potentialof an Artificial Neural Network (ANN) for determiningthe direction of incidence of an Atmospheric Cerenkov Event(ACE) from the arrival-time information registered by aspaced-array of wide-angle Cerenkov detectors. Theresults obtained so far, using both, simulated and experimental data, indicate that a properly-trained net can yield a degree of accuracy which is comparable with what is achieved through the conventional ²-minimization, wavefront-fitting procedure.     

Evaluation of Recharge and Groundwater Dynamics of a Shallow Alluvial Aquifer in Central Ganga Basin,Kanpur (India)

Evaluation of recharge and groundwater dynamics of an aquifer is an important step for finding a proper groundwater management scenario. This has been performed on the basis of statistical Kendall Tau test to find a relationship between groundwater levels and hydro-meteorological parameters (e.g., precipitation, temperature, evaporation). Recharge to the aquifer was estimated for identification of critical areas/locations based on the analytical Soil and Water Assessment Tool. Moreover, spatiotemporal variability of groundwater levels has been quantified using space–time variogram. The overall characterization method has been applied to the shallow alluvial aquifer of Kanpur city in India. The analysis was performed using groundwater level data from 56 monitoring piezometer locations in Kanpur from March 2006 to June 2011. Groundwater level shows relatively higher correlation with temperature. Performance of the geostatistical model was evaluated by comparing with the observed values of groundwater level from January 2011 to June 2011 for two scenarios: “with limited spatiotemporal data” and “without spatiotemporal data.” It is evident that spatiotemporal prediction of groundwater level can be performed even for the unmonitored/missing data. This analysis demonstrates the potential applicability of the method for a general aquifer system.