A study on the impact of weathering in groundwater chemistry of a hard rock aquifer     

V. S. Adithya  S. Chidambaram  C. Thivya  R. Thilagavathi  M. V. Prasanna  M. Nepolian  N. Ganesh 《Arabian Journal of Geosciences》2016,9(2):158

Hydrogeochemistry of groundwater in hard rock terrain are mainly governed by lithology and land use practices. A study area near Madurai region of central Tamil Nadu was selected with various litho-units and a hard rock sedimentary contact with an unconformity. Land use practices in these regions are also varied with lithology. The study was conducted by collecting 54 groundwater samples spatially covering the major litho-units. Collected samples were analyzed for electrical conductivity, pH, total dissolved solids (TDS), temperature, Ca, Mg, Na, K, Cl, HCO₃, NO₃, H₄SiO₄, PO₄, and SO₄. The results of the samples analyzed found to vary spatially. Dominance of ion shows that the alkalies are predominant and HCO₃ is the dominant anion. Piper facies show that the samples are alkali-carbonate type indicating the predominance of weathering. Most of the parameters exceed the drinking water permissible limit. Standard plots and statistical analysis also indicate weathering as the major process governing the hydrogeochemistry of the groundwater in the region. Relative mobility of cations indicates that the rate of liberation of alkalies from the lithology is more prominent.  相似文献   

El Niño and Indian summer monsoon rainfall relationship in retrospective seasonal prediction runs: experiments with coupled global climate models and MMEs     

P. K. Pradhan  Venkatraman Prasanna  Doo Young Lee  Myong-In Lee 《Meteorology and Atmospheric Physics》2016,128(1):97-115

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Understanding fen hydrology across multiple scales          下载免费PDF全文

Prasanna Venkatesh Sampath  Hua‐Sheng Liao  Zachary Kristopher Curtis  Matthew E. Herbert  Patrick J. Doran  Christopher A. May  Douglas A. Landis  Shu‐Guang Li 《水文研究》2016,30(19):3390-3407

Fens, which are among the most biodiverse of wetland types in the USA, typically occur in glacial landscapes characterized by geo‐morphologic variability at multiple spatial scales. As a result, the hydrologic systems that sustain fens are complex and not well understood. Traditional approaches for characterizing such systems use simplifying assumptions that cannot adequately capture the impact of variability in geology and topography. In this study, a hierarchical, multi‐scale groundwater modelling approach coupled with a geologic model is used to understand the hydrology of a fen in Michigan. This approach uses high‐resolution data to simulate the multi‐scale topographic and hydrologic framework and lithologic data from more than 8500 boreholes in a statewide water well database to capture the complex geology. A hierarchy of dynamically linked models is developed that simulates groundwater flow at all scales of interest and to delineate the areas that contribute groundwater to the fen. The results show the fen receiving groundwater from multiple sources: an adjacent wetland, local recharge, a nearby lake and a regional groundwater mound. Water from the regional mound flows to an intermediate source before reaching the fen, forming a ‘cascading’ connection, while other sources provide water through ‘direct’ connections. The regional mound is also the source of water to other fens, streams and lakes in this area, thus creating a large, interconnected hydrologic system that sustains the entire ecosystem. In order to sustainably manage such systems, conservation efforts must include both site‐based protection and management, as well as regional protection and management of groundwater source areas. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Hydrological impact of Eucalyptus plantation in India   总被引：1，自引：0，他引：1  

Ian R. Calder  Robin L. Hall  K. T. Prasanna 《Journal of Hydrology》1993,150(2-4):635-648

A brief review is given of the results of hydrological studies carried out in southern India on the effects of plantations of Eucalyptus and other fast growing exotic tree species on water resources, erosion and soil nutrients at sites of differing rainfall and soil depth in Karnataka. New results on the impacts of the plantations on raindrop-induced erosion and preliminary results from studies that are aimed at improving the water use efficiency of the plantations are also presented.

The erosion studies indicate that soil detachment resulting from net rainfall beneath Eucalyptus camaldulensis will be greater than beneath Pinus caribaea but less than that beneath the indigenous species, Tectona grandis.

The water use efficiency studies, which make use of a controlled environment facility, have confirmed that in the dry zone of southern India water availability is the principal limiting factor on growth although, when water is available, nutrient limitations become important. Removal of both water and nutrient stress results typically in a fivefold increase in volume growth for the first year of growth.  相似文献   

The variations of stable carbon isotope ratio of land plant-derived n-alkanes in deep-sea sediments from the Bering Sea and the North Pacific Ocean during the last 250,000 years   总被引：1，自引：0，他引：1  

Nalin Prasanna Ratnayake  Noriyuki Suzuki  Makoto Okada 《Chemical Geology》2006,228(4):197-208

Two piston cores, one located far from the continents (The North Pacific Ocean: ES core), and another located comparatively closer to the continents (The Bering Sea: BOW-8a core) were investigated to reconstruct environmental changes on source land areas. The results show significant contribution of terrestrial organic matter to sediments in both cores. The δ¹³C values of n-C₂₇, n-C₂₉, and n-C₃₁ alkanes in sediments from the North Pacific ES core show significant glacial to interglacial variation whereas those from the Bering Sea core do not. Variations of δ¹³C values of land plant n-alkanes are related to the environmental or vegetational changes in the source land areas. Environmental changes, especially, aridity, rainfall, and pCO₂ during glacial/interglacial transitional periods can affect vegetation, and therefore C₃ / C₄ plant ratios, resulting in δ¹³C changes in the preserved land plant biomarkers. Maximum values of δ¹³C as well as maximum average chain length values of long chain n-alkanes in the ES core occur mostly at the interglacial to glacial transition zones reflecting a time lag related to incorporation of living organic matter into soil and transportation into ocean basins via wind and/or ability of C₄ plants to adapt for a longer period before being replaced by C₃ plants when subjected to gradual climatic changes. Irregular variations with no clear glacial to interglacial trends in the BOW-8a core may result from complex mixture of aerosols from westerly winds and riverine organic matter from the Bering Sea catchments. In addition, terrestrial organic matter entering the Bering Sea could originate from multiple pathways including eolian, riverine, and ice rafted debris, and possibly be disturbed by turbidity and other local currents which can induce re-suspension and re-sedimentation causing an obliterated time relation in the Bering Sea biomarker records.  相似文献   

A modelling study of the latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum     

G. J. Bailey  M. H. Denton  R. A. Heelis  S. Venkatraman 《Annales Geophysicae》2000,18(11):1435-1446

Latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum have been examined by using values modelled by SUPIM (Sheffield University Plasmasphere Ionosphere Model) and observations made by the DMSP F10 satellite at 21.00 LT near 800 km altitude. The modelled values confirm that the crests observed near 15° latitude in the winter hemisphere are due to adiabatic heating and the troughs observed near the magnetic equator are due to adiabatic cooling as plasma is transported along the magnetic field lines from the summer hemisphere to the winter hemisphere. The modelled values also confirm that the interhemispheric plasma transport needed to produce the required adiabatic heating/cooling can be induced by F-region neutral winds. It is shown that the longitudinal variations in the observed troughs and crests arise mainly from the longitudinal variations in the magnetic meridional wind. At longitudes where the magnetic declination angle is positive the eastward geographic zonal wind combines with the northward (summer hemisphere to winter hemisphere) geographic meridional wind to enhance the northward magnetic meridional wind. This leads to deeper troughs and enhanced crests. At longitudes where the magnetic declination angle is negative the eastward geographic zonal wind opposes the northward geographic meridional wind and the trough depth and crest values are reduced. The characteristic features of the troughs and crests depend, in a complicated manner, on the field-aligned flow of plasma, thermal conduction, and inter-gas heat transfer. At the latitudes of the troughs/crests, the low/high plasma temperatures lead to increased/decreased plasma concentrations.  相似文献   

Assessment of South Asian Summer Monsoon Simulation in CMIP5-Coupled Climate Models During the Historical Period (1850–2005)     

Venkatraman Prasanna 《Pure and Applied Geophysics》2016,173(4):1379-1402

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Formulation of stability-dependent empirical relations for turbulent intensities from surface layer turbulence measurements for dispersion parameterization in a lagrangian particle dispersion model     

K.?B.?R.?R.?Hari Prasad  C.?V.?SrinivasEmail author  A.?N.?V.?Satyanarayana  C.?V.?Naidu  R.?Baskaran  B.?Venkatraman 《Meteorology and Atmospheric Physics》2015,127(4):435-450

Season- and stability-dependent turbulence intensity (σ _u /u _*, σ _v /u _*, σ _w /u _*) relationships are derived from experimental turbulence measurements following surface layer scaling and local stability at the tropical coastal site Kalpakkam, India for atmospheric dispersion parameterization. Turbulence wind components (u′, v′, w′) measured with fast response UltraSonic Anemometers during an intense observation campaign for wind field modeling called Round Robin Exercise are used to formulate the flux–profile relationships using surface layer similarity theory and Fast Fourier Transform technique. The new relationships (modified Hanna scheme) are incorporated in a Lagrangian Particle Dispersion model FLEXPART-WRF and tested by conducting simulations for a field tracer dispersion experiment at Kalpakkam. Plume dispersion analysis of a ground level hypothetical release indicated that the new turbulent intensity formulations provide slightly higher diffusivity across the plume relative to the original Hanna scheme. The new formulations for σ _u , σ _v , σ _w are found to give better agreement with observed turbulent intensities during both stable and unstable conditions under various seasonal meteorological conditions. The simulated concentrations using the two methods are compared with those obtained from a classical Gaussian model and the observed SF₆ concentration. It has been found that the new relationships provide comparatively higher diffusion across the plume relative to the model default Hanna scheme and provide downwind concentration results in better agreement with observations.  相似文献   

Regional climate change scenarios over South Asia in the CMIP5 coupled climate model simulations   总被引：1，自引：0，他引：1  

Venkatraman Prasanna 《Meteorology and Atmospheric Physics》2015,127(5):561-578

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A study on the mixing proportion in groundwater samples by using Piper diagram and Phreeqc model   总被引：1，自引：0，他引：1  

Karmegam U.  Chidambaram S.  Prasanna M.V.  Sasidhar P.  Manikandan S.  Johnsonbabu G.  Dheivanayaki V.  Paramaguru P.  Manivannan R.  Srinivasamoorthy K.  Anandhan P 《中国地球化学学报》2011,30(4):490-495

Piper (1944) diagram has been the basis for several important interpretations of the hydrogeochemical data. As seen in this diagram, most natural waters contain relatively few dissolved constituents, with cations (metals or bases) and anions (acid radicles) in chemical equilibrium with one another. Apart from the facies representation, the composition of the mixed sample can be identified in terms of the composition of the parental solution. To bring out this advantage of the Piper diagram, a study was conducted in the Kalpakkam region of Tamilnadu, South India. By taking the geology and water table into consideration, two sample locations were selected as parent solution and third one as the mixture sample. All three samples were analyzed for calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chloride (Cl), sulphate (SO4) and phosphate (PO4) by Ion Chromatograph (Metrohm IC 861). HCO3 was determined by volumetric titration. The Piper diagram shows that parent solutions clustered towards Na-Mg-Ca-HCO3-Cl and Na-HCO3 facies, and the mixing sample belongs to Na-Mg-HCO3 facies. Phreeqc interac-tive (Ver 2.8) along with the original composition of the mixture sample was used to correlate the mixing proportion identified by the Piper diagram.  相似文献