Temporal variations in Sr and 87Sr/86Sr of the Ganga headwaters: estimates of dissolved Sr flux to the mainstream     

Gyana Ranjan Tripathy  Vineet Goswami  Sunil Kumar Singh  G. J. Chakrapani 《水文研究》2010,24(9):1159-1171

The headwaters of the Ganga (the Alaknanda, Bhagirathi and the Ganga) were analysed for their dissolved major ions, Sr and ⁸⁷Sr/⁸⁶Sr on a biweekly to monthly basis over a period of one year to determine their temporal variations and the factors contributing to them. The concentrations of major ions and Sr show significant seasonal variation with lower values during monsoon period in all the three rivers. A similar trend is also observed for ⁸⁷Sr/⁸⁶Sr and Na*/Ca (Na* = Na_r? Cl_r) suggesting relatively lower contribution of Sr and Na from silicates (which are more radiogenic in Sr) during monsoon. Budget calculations show that silicate derived dissolved Sr (Sr_s) in the river Ganga, Alaknanda and the Bhagirathi varied from 10 ± 4 to 27 ± 11, 7 ± 3 to 30 ± 12, 16 ± 6 to 57 ± 23% of measured Sr respectively with lower values during monsoon. The relative decrease in silicate erosion compared to carbonate during monsoon can result from several factors, these include higher dissolution kinetics of the carbonates, lower water–rock interaction time and availability of larger area for weathering. The annual discharge weighted Sr flux derived from the time series data is higher by ～20% from that based on peak flow Sr, and lower by ～40% compared to that derived from lean flow Sr concentration. The area‐normalized annual flux of dissolved Sr from the Ganga at Rishikesh is about five times its flux at Rajshahi (Bangladesh) and a few other major global rivers, such as the Amazon, indicating higher erosion rate over the Himalaya. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Drought assessment in the Dhar and Mewat Districts of India using meteorological,hydrological and remote-sensing derived indices   总被引：1，自引：1，他引：0  

R. N. Sahoo  Dipanwita Dutta  M. Khanna  N. Kumar  S. K. Bandyopadhyay 《Natural Hazards》2015,77(2):733-751

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Tracer-based estimation of temporal variation of water sources: an insight from supra- and subglacial environments     

Naveen Kumar  Tirumalesh Keesari  S. Chidambaram  Shyam Ranjan  Mohd Soheb 《水文科学杂志》2013,58(11):1717-1732

ABSTRACT

The temporal variations in electrical conductivity and the stable isotopes of water, δD and δ¹⁸O, were examined at Chhota Shigri Glacier, India, to understand water sources and flow paths to discharge. Discharge is highly influenced by supraglacially derived meltwater during peak ablation, and subglacial meltwaters are more prominent at the end of the melt season. The slope of the best fit linear regression line for δD versus δ¹⁸O, for both supraglacial and runoff water, is lower than that for precipitation (snow and rain) and surface ice, indicating strong isotopic fractionation associated with the melting processes. The slope of the local meteoric water line (LMWL) is close to that of the global meteoric water line (GMWL), reflecting that the moisture source is predominantly oceanic. The d-excess variation in rainwater confirms that the southwest monsoon is the main contributor during summer while the remainder including winter is mostly influenced by westerlies.  相似文献   

Horizontal Pullout Resistance for a Group of Two Vertical Plate Anchors in Clays     

Jagdish Prasad Sahoo  Jyant Kumar 《Geotechnical and Geological Engineering》2012,30(5):1279-1287

The horizontal pullout capacity of a group of two rigid strip plate anchors embedded along the same vertical plane in clays, under undrained condition, has been determined. An increase of cohesion with depth has also been incorporated. The analysis has been performed by using an upper bound finite element limit analysis in combination with linear optimization. For different clear spacing (S) between the anchors, the efficiency factor (η_cγ) has been determined to evaluate the group failure load for different values of (1) embedment ratio (H/B), (2) the normalized rate (m) which accounts for a linear increase of cohesion with depth, and (3) normalized unit weight (γH/c_o). The magnitude of the group failure load (1) becomes maximum corresponding to a certain spacing (S_cr) between the anchors, and (2) increases with an increase in the γH/c_o up to a certain value before attaining a certain maximum magnitude. The value of S_cr/B has been found to vary generally between 0.7 and 1.2. The maximum magnitude of η_cγ, associated with the critical spacing, (1) increases generally with increases in H/B, and (2) decreases with an increase in m. For a greater spacing between the anchors, the analysis reveals the development of a local shear zone around the lower anchor plate. The numerical results developed are expected to be useful for purpose of design.  相似文献   

Stabilization of a Clayey Soil with Fly Ash and Lime: A Micro Level Investigation   总被引：2，自引：0，他引：2  

Neeraj Kumar Sharma  S. K. Swain  Umesh C. Sahoo 《Geotechnical and Geological Engineering》2012,30(5):1197-1205

Pavement structures on poor soil sub grades show early distresses causing the premature failure of the pavement. Clayey soils usually have the potential to demonstrate undesirable engineering behavior, such as low bearing capacity, high shrinkage and swell characteristics and high moisture susceptibility. Stabilization of these soils is a usual practice for improving the strength. This study reports the improvement in the strength of a locally available cohesive soil by addition of both fly ash and lime. Analysis using X-ray diffraction, scanning electron microscopy, coupled with energy dispersive spectroscopy, thermal gravimetric analysis, zeta potential and pH value test was carried out in order to elucidate the stabilization mechanism. The micro level analysis confirmed the breaking of montmorrillonite structure present in the untreated clay after stabilization. In the analysis, it was also confirmed that in the stabilization process, pozzolanic reaction dominated over the cation exchange capacity.  相似文献   

Economic impacts of Pink Hibiscus Mealybug in Florida and the United States     

Ram Ranjan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(5):353-362

This paper estimates the expected annual impacts of the Pink Hibiscus Mealybug infestation on the economies of Florida and the rest of the United States. The approach involves a Markov chain analysis wherein both short run and long run expected damages from infestation are calculated. Use is made of the CLIMEX model that predicts the potential pest-establishment regions in the US. While predictions based upon the CLIMEX model extend the scope of damages beyond Florida, the damages are significantly dependent upon the rate of arrival and detection of species in those regions. Damages are significantly higher when a longer time horizon is considered. When nursery owners bear the full cost of quarantines in the form of loss of sales and treatment costs of infected plants, the cost-effectiveness of quarantines as a regulatory tool is diminished. The long run propensity of the system, in terms of the fraction of time spent in the possible ‘states’ of infestation and control, determines the extent of damages, and not the annual value of crops that could be potential hosts to the pest.

Ram RanjanEmail: Phone: +1-352-3921881Fax: +1-352-3929898

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Non-Existence of Five Dimensional Perfect Fluid Cosmological Model in Lyra Manifold     

G. Mohanty  K. L. Mahanta  R. R. Sahoo 《Astrophysics and Space Science》2006,306(4):269-272

In this paper we have taken an attempt to construct a five dimensional perfect fluid cosmological model within the framework of Lyra manifold. It is found that neither perfect fluid nor dust distributions survive. Finally the exact solutions of the vacuum field equations are obtained.  相似文献   

Bianchi type VI h perfect fluid cosmological model in f(R,T) theory     

B. Mishra  P. K. Sahoo 《Astrophysics and Space Science》2014,352(1):331-336

In this paper, we have investigated Bianchi type VI _h cosmological model filled with perfect fluid in the framework of f(R,T) gravity, where R is the Ricci scalar and T is the trace of the energy-momentum tensor proposed by Harko et al. (Phys. Rev. D 84:024020, 2011). We have obtained the cosmological models by solving the field equations. Some physical behaviors of the model are also studied.  相似文献   

Erratum to: Climate variability and change in mountain environments: some implications for water resources and water quality in the Sierra Nevada (USA)     

Mariza Costa-Cabral  Robert Coats  John Reuter  John Riverson  Goloka Sahoo  Geoffrey Schladow  Brent Wolfe  Sujoy B. Roy  Limin Chen 《Climatic change》2013,116(1):15-16

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The response of Lake Tahoe to climate change   总被引：2，自引：0，他引：2  

G. B. Sahoo  S. G. Schladow  J. E. Reuter  R. Coats  M. Dettinger  J. Riverson  B. Wolfe  M. Costa-Cabral 《Climatic change》2013,116(1):71-95

Meteorology is the driving force for lake internal heating, cooling, mixing, and circulation. Thus continued global warming will affect the lake thermal properties, water level, internal nutrient loading, nutrient cycling, food-web characteristics, fish-habitat, aquatic ecosystem, and other important features of lake limnology. Using a 1-D numerical model—the Lake Clarity Model (LCM) —together with the down-scaled climatic data of the two emissions scenarios (B1 and A2) of the Geophysical Fluid Dynamics Laboratory (GFDL) Global Circulation Model, we found that Lake Tahoe will likely cease to mix to the bottom after about 2060 for A2 scenario, with an annual mixing depth of less than 200 m as the most common value. Deep mixing, which currently occurs on average every 3–4 years, will (under the GFDL B1 scenario) occur only four times during 2061 to 2098. When the lake fails to completely mix, the bottom waters are not replenished with dissolved oxygen and eventually dissolved oxygen at these depths will be depleted to zero. When this occurs, soluble reactive phosphorus (SRP) and ammonium-nitrogen (both biostimulatory) are released from the deep sediments and contribute approximately 51 % and 14 % of the total SRP and dissolved inorganic nitrogen load, respectively. The lake model suggests that climate change will drive the lake surface level down below the natural rim after 2085 for the GFDL A2 but not the GFDL B1 scenario. The results indicate that continued climate changes could pose serious threats to the characteristics of the Lake that are most highly valued. Future water quality planning must take these results into account.  相似文献