Variability of Nonionellina labradorica Dawson in Surface Sediments from Kongsfjorden, West Spitsbergen     

Suhas SHETYE  Rahul MOHAN  Sunil Kumar SHUKLA  Sudhakar MARUTHADU  Rasik RAVINDRA 《《地质学报》英文版》2011,85(3):549-558

Kongsfjorden is a fjord in Spitsbergen (Svalbard archipelago) that lies adjacent to both Arctic and Atlantic water masses and is therefore a suitable site to understand the effects of climate change on ecosystems. To decipher the effect of the lateral advection of transformed Atlantic water (TAW) within the fjord, spatial variations of foraminiferal tests, their test size variations and stable isotopic composition (δ13C and δ18O) in the surface sediments were studied. Total organic carbon and textural analyses were also carried out. The dominant benthic foraminifera included Nonionellina labradorica, Elphidium excavatum, Cassidulina reniforme, Quinqueloculina stalkeri and Islandiella islandica. Nonionellina labradorica was the predominant species in the outer fjord, whereas Elphidium excavatum and Cassidulina reniforme were dominant in the inner fjord. Total organic carbon and the test size of Nonionellina labradorica within the fjord were highly correlated (r2?=?0.97) and both showed a decreasing trend towards the inner fjord. Based on the distribution and abundance of Nonionellina labradorica as well as temperature profiles, we suggest that there was little or no major change in the lateral advection of TAW within the fjord in the immediate past.  相似文献   

Debris control on glacier thinning—a case study of the Batal glacier,Chandra basin,Western Himalaya     

Lavkush Kumar Patel  Parmanand Sharma  Meloth Thamban  Ajit Singh  Rasik Ravindra 《Arabian Journal of Geosciences》2016,9(4):309

Complex factors such as climate, glacial geometry, topographical features and debris covers have significant influence on the dynamics of the Himalayan glaciers. Presence of debris covers on the surface of glaciers can significantly alter the surface energy balance and influence the climatic response of glaciers. In this study, the influence of debris covers and its impact on the ablation processes were analyzed from the in situ data collected over the surface of the Batal glacier in Chandra Basin, Western Himalaya. Almost 90 % of the ablation zone of the Batal glacier is covered by debris, 35 % of which is thick debris (>10 cm). Fourteen stakes (depth ～10 m) with increasing altitude and with varying debris thicknesses were installed to cover the whole ablation zone. Among them, four stakes represent thin debris (<2 cm), two stakes represent 2–5 cm debris thickness, two stakes represent 5–25 cm debris thickness, three stakes represent 25–50 cm debris thickness and three stakes represent >50 cm debris thickness. Our study has revealed high surface melting (?2.0 cm. w.e.d^?1) in the debris free glacier while low surface melting observed in thick debris covered ice (?0.6 cm. w.e.d^?1). Although limited to one season, this observation revealed a significant difference in the rate of surface melting as per the increasing debris thickness. Contrasting to normal ablation pattern over glaciers, Batal has experienced inverse retreat rate of ablation along with increasing altitude. A high degree of negative correlation (r = ?0.82, p < 0.05) between ablation rate and debris thickness in Batal suggest a significant control of debris thickness over ablation rate.  相似文献   

Seismic site characterization and site response study of Nirsa (India)     

Gupta  Ravindra K.  Agrawal  Mohit  Pal  S. K.  Das  M. K. 《Natural Hazards》2021,108(2):2033-2057

Natural Hazards - The Nirsa block, a coal mining area, and an industrial town lies in the southern part of Dhanbad district, at the border between the Indian states of Jharkhand and West Bengal....  相似文献   

Coexisting chloritoid-staurolite from the Sillimanite (fibrolite) zone,Sini, district Singhbhum,India     

Ravindra K. Lal  Dietrich Ackermand 《Lithos》1979,12(2):133-142

Microprobe analyses of the minerals from an unusual chloritoid-staurolite-garnet (+ muscovite + quartz + ilmenite) assemblage from the sillimanite (fibrolite) zone of Sini, India are presented and the petrological significance of the paragenesis is discussed. The X Mg in the different minerals from the chloritoid-staurolite-bearing rock varies in the order, muscovite > chlorite > chloritoid > staurolite > garnet > ilmenite, and from the associated sillimanite-bearing schists: muscovite > biotite > staurolite > garnet rim > garnet core > ilmenite. A graphical representation of the mineral compositions in an AFM projection displays a consistent topology if the effects of non-AFM components such as Zn in the staurolite and Mn in the garnet are taken into account. Petrographic and mineralogical data are consistent with a prograde formation of the chloritoid-staurolite-garnet assemblage. It is suggested that the paragenesis has been formed at similar PT conditions to the associated sillimanite (fibrolite)-staurolite-garnet-mica schists. These conditions are estimated to be 600–625°C/6±0.5 Kb.  相似文献   

Structure and Evolution of the Transition Region Network Observed in he ii λ304     

Ravindra  B.  Venkatakrishnan  P. 《Solar physics》2003,215(2):239-259

The length scale and life time of the transition region network cells were studied using Heii 304 filtergrams. The temporal structure function was calculated from spatially aligned Heii 304 images. The estimated life time of the network cell was about 27 hr. We compared this life time with the life time of photospheric magnetic network and of the extrapolated magnetic network. The spatial structure function was calculated from the Heii 304 filtergrams. The calculated spatial structure function saturates at 25000 km. The transition region network elements are bigger in size than the photospheric magnetic network element. The magnetic network element equals the size of the Heii 304 network element when the photospheric magnetic field is extrapolated to a height of 3000 km above the photosphere where the magnetic fluxes are deployed. The derived value of the diffusion speed of the network elements was 0.098 km s^–1.  相似文献   

An improved practical approach for estimating catchment-scale response functions through wavelet analysis     

Ravindra Dwivedi  Christopher Eastoe  John F. Knowles  Lejon Hamann  Thomas Meixner  Paul A. “Ty” Ferre  Christopher Castro  William E. Wright  Guo-Yue Niu  Rebecca Minor  Greg A. Barron-Gafford  Nathan Abramson  Bhaskar Mitra  Shirley A. Papuga  Michael Stanley  Jon Chorover 《水文研究》2021,35(3):e14082

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Development of hyperspectral model for rapid monitoring of soil organic carbon under precision farming in the Indo-Gangetic Plains of Punjab,India     

Rajeev Srivastava  Dipak Sarkar  Siddhartha S. Mukhopadhayay  Anil Sood  Manjeet Singh  Ravindra A. Nasre  Sanjay A. Dhale 《Journal of the Indian Society of Remote Sensing》2015,43(4):751-759

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Removal of metal from acid mine drainage (AMD) by using natural zeolite of Nizarneshwar Hills of Western India     

Ravindra W. Gaikwad  S. A. Misal  Dhirendra  D. V. Gupta 《Arabian Journal of Geosciences》2011,4(1-2):85-89

The mining industry faces stringent effluent discharge regulations and has acknowledged that it is necessary to look into innovative technologies to recycle considerable amount of effluent rather than discharging into surface water. Effluents from mines give rise to aesthetic unpleasantness. The focus of the investigations was to cope with more stringent effluent discharge regulations and to protect the ecosystem from harmful pollutants in the mine effluents. Copper is one of the heavy metal in the mine systems, which are known to be a harmful element. The present study has been undertaken to investigate a process that might remove Cu(II) from mine waste water by using natural zeolite, such as stilbite, and compared with synthetic resins like CSA-9 and CSA-609D. In this study, natural zeolite was used as a low-cost adsorbent to evaluate its ability to remove heavy metals from acid mine drainage. The zeolite used in this study is the natural clay mineral from the Nizarneshwar Hills of Western India. Three resins tested are CSA-9, natural zeolite–stilbite, and CSA-609D. Batch testing has been conducted to select effective ion-exchange resins for copper removal and to determine effective regenerants for regeneration of exhausted resins. All tests were conducted at bench scale and in batch mode. Three strong acid cation exchangers were evaluated to compare their metal removal capacities. The metal concentration in the effluent was reduced with all resins tested. It was found that, among all the three types of natural zeolite, stilbite shows the highest removal efficiency of copper in every parameter that is considered for evaluating the performance of resins.  相似文献   

The bottomless dam     

Ravindra M. Phatarfod 《Journal of Hydrology》1979,40(3-4):337-363

The purpose of the work reported here is to show that it is more fruitful to consider the bottomless (infinitely deep) dam as an approximation to the finite dam rather than the topless (infinitely high) dam considered hitherto. It is shown by taking a wide variety of input models that the theory for the former is far simpler, and the final results are in a form simple enough to give a quick estimate of the size of the reservoir required.  相似文献   

Anthropogenic arsenic menace in Delhi Yamuna Flood Plains   总被引：2，自引：1，他引：1  

Chandra S. Dubey  Bhupendra K. Mishra  Dericks P. Shukla  Ravindra P. Singh  M. Tajbakhsh  Purushottam Sakhare 《Environmental Earth Sciences》2012,65(1):131-139

Arsenic, one of the most poisonous chemical elements, was analyzed in the waters of the host of the 2010 Commonwealth Games, i.e., New Delhi. The study revealed shocking outcomes with arsenic concentrations well beyond the safe limits set by WHO, and a maximum concentration up to 180 ppb was found in the groundwater. Analysis of around 120 water samples collected extensively along the Yamuna Flood Plain showed that more than 55% had arsenic contamination beyond the WHO limit of 10 ppb. The maximum value of arsenic in coal and fly ash from Rajghat coal-based thermal power plant contained 200 and 3,200 ppb, respectively. Moreover, the ore petrography of coal samples shows the presence of arsenopyrite mineral. Maximum concentration of arsenic contamination is found within a 5-km radius from power plants. In the perspective of Delhi, arsenic contamination is purely anthropogenic due to coal-based thermal power plants, which had already shown toxic arsenic, fluorine and China-type coal effects. The presence of such power plants in coal field locations, e.g., West Bengal and Bangladesh, could release the arsenic due to combustion in superthermal power plants, thus accentuating the arsenic concentration besides the natural arsenic coming from the foreland basins of the Himalaya in Indian sub-continent.  相似文献