Recharge mechanism and processes controlling groundwater chemistry in a Precambrian sedimentary terrain: a case study from Central India     

R. K. Ray  T. H. Syed  Dipankar Saha  B. C. Sarkar  D. V. Reddy 《Environmental Earth Sciences》2017,76(3):136

Unplanned and unsustainable extraction has created stress on groundwater resources in many parts of India. The stress symptoms are more pronounced in hard rock areas, where the aquifer potentials are comparatively low. Present research targeted an area of 3000 km² in the interstream region between the Kharun and Seonath rivers, which is one such region in Central India. In spite of being a water-stressed area, so far, little is understood about processes of recharge, amount of recharge and processes controlling chemical quality, which are key inputs for groundwater management in the area. This study presents an appraisal of recharge mechanism, recharge rate and prevailing water–rock interactions in the study area. Stable isotope composition of groundwater when compared to that of rainfall indicates monsoon rainfall as the primary source of groundwater recharge. Winter rains, which are characteristically enriched in heavier isotopes, do not contribute notably to groundwater recharge. Recharge is rapid with minor or no evaporative enrichment before recharge. Further, analysis of stable isotopes show that ‘macropore recharge’ is dominant in limestone or calcareous shale, covering more than 70% of the study area. Also apparent is the vertical connectivity amongst the aquifers. However, active intermixing of surface water and groundwater is not a predominant process. Annual groundwater recharge from rainfall, as derived from chloride mass balance, is 105.26 million cubic metre. Groundwater is predominantly of bicarbonate type, irrespective of its hydrostratigraphic (lithology) setting. Dissolution of carbonates and gypsum (occurring as veins), weathering of feldspar and ion exchange of clay minerals are amongst the most likely processes controlling the regional groundwater chemistry.  相似文献   

Groundwater contamination with arsenic in Sherajdikhan,Bangladesh: geochemical and hydrological implications     

M. A. Halim  R. K. Majumder  S. A. Nessa  K. Oda  Y. Hiroshiro  B. B. Saha  S. M. Hassain  Sk. A. Latif  M. A. Islam  K. Jinno 《Environmental Geology》2009,58(1):73-84

An integrated study has been carried out to elucidate the distribution and occurrence of arsenic in selected groundwater samples in the area of Sherajdikhan, Bangladesh. Arsenic and other parameters (T, pH, EC, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃ ⁻, SO₄ ²⁻, HCO₃ ⁻, PO₄ ³⁻, Fe, Mn and DOC) have been measured in groundwater samples collected from shallow/deep tube wells at different depths. Hydrogeochemical data suggest that the groundwaters are generally Ca–Mg–HCO₃ and Mg–Ca–HCO₃ types with bicarbonate (HCO₃ ⁻) as the dominant anion, though the other type of water has also been observed. Dissolved arsenic in groundwater ranged from 0.006 to 0.461 mg/l, with 69% groundwater samples exceeded the Bangladesh limit for safe drinking water (0.05 mg/l). Correlation and principal component analysis have been performed to find out possible relationships among the examined parameters in groundwater. Low concentrations of NO₃ ⁻ and SO₄ ²⁻, and high concentrations of DOC, HCO₃ ⁻ and PO₄ ³⁻ indicate the reducing condition of subsurface aquifer where sediments are deposited with abundant organic matter. Distinct relationship of As with Fe and Mn, and strong correlation with DOC suggests that the biodegradation of organic matter along with reductive dissolution of Fe–Mn oxyhydroxides has being considered the dominant process to release As in the aquifers studied herein.  相似文献   

On particle trajectories in restricted 3-body problem including the effect of radiation: Sun-Jupiter system     

M. K. Das  Pankaj Narang  M. Yuasa  L. M. Saha 《Astrophysics and Space Science》2008,314(1-3):59-71

In this work, we have simulated orbits of a particle moving in gravitational field of the Sun-Jupiter system. The effect of solar radiation pressure, including Poynting Robertson drag, on the evolution of particle orbits in phase space have been studied for different values of the parameter β ₁ (the ratio of radiation to gravitational force) and initial conditions. Characteristics of various computed trajectories have been studied using wavelet transform (WT), Fourier transform (FT) and Poincare surface of section method. We use wavelet analysis to identify transitions of a trajectory in time-frequency plane and further apply it to classify it as regular or chaotic in phase space. Unlike the Fourier transform method (FT), we observe that the wavelet transform (WT) also provides a basis to identify ‘sticky’ trajectories in the present dynamical system.  相似文献   

Hazardous Waste Pollution Prevention Using Clay with Admixtures     

Papita Saha  Siddhartha Datta  Shyamal Kanti Sanyal 《洁净——土壤、空气、水》2008,36(2):230-238

Landfill is the most commonly used method for disposal of waste materials since it is one of the least expensive methods. In order to dispose of any hazardous material to a landfill, a liner is used, which protects the underlying land and groundwater since it acts as a barrier to fluid movement. Of the various methods available for providing improved and more effective properties of landfills, methods involving the use of bentonite, cement, lime, gypsum, etc., have been explored in the laboratory. The aim is to overcome the problem and deficiencies of the existing liners. It is observed from the experimental results that the metal concentrations of the input waste solution can be reduced to 80–98% using a soil‐cement admixture, 60–95% using a soil‐gypsum mixture, 45–95% using a soil‐bentonite mixture, 50–90% for soil, 35–80% using a soil‐lime mixture, as liner materials. The permeation rate of different metals through the different soil‐admixture media depends on various factors. A simple mathematical treatment of the phenomenon related to the permeation of liquid through the admixture of the clay and other components has been developed. The experimental results show satisfactory agreement with the predictions.  相似文献   

Development of a Speckle Interferometer and the Measurement of Fried's Parameter (ro) at the Telescope Site     

S. K. Saha  G. Sudheendra  A. Umesh Chandra  V. Chinnappan 《Experimental Astronomy》1999,9(1):39-49

A new optical speckle interferometer for use at the 2.34 meter Vainu Bappu Telescope (VBT), at Vainu Bappu Observatory (VBO), Kavalur, India, has been designed and developed. Provisions have been made for observation both at the prime focus (f/3,25), as well as at the Cassegrain focus (f/13) of the said telescope. The technical details of this sensitive instrument and the design features are described. An interface between the telescope and the afore-mentioned interferometer is made based on a concept of eliminating the formation of eddies due to the hot air entrapment. The performances of this instrument has been tested both at the laboratory, as well as at the Cassegrain end of the telescope. It is being used routinely to observe the speckle-grams of close-binary (separation < 1 arc second) stars. The size of the Fried's parameter, r_o, is also measured.  相似文献   

Low-latitude infrasonics associated with geomagnetic activity     

B. J. Srivastava  R. Venkatachari  A. K. Saha 《Geophysical Journal International》1982,71(1):241-245

Summary. Certain associated fluctuations in geomagnetic records and infrasonic pressure variations at ground level noted at Hyderabad and Delhi are discussed with the help of simultaneous records taken during 1980. Typical infrasound signals are noted, apparently generated by the magnetic substorms in the auroral zones and travelling down to near tropical latitudes with speeds in the range of 400–500m s^-1. Characteristic signatures in infrasound records, corresponding to SSCs and storm time fluctuations are also noted, but only when substorms are associated with the storms.  相似文献   

Variation of γ-Ray and Particle Fluxes At the Sea Level During the Total Solar Eclipse of 24 October, 1995     

Abhijit Bhattacharyya  Sukumar Biswas  Barun K. Chatterjee  Mala Das  Pradipta K. Das  Tapan K. Das  Tarun K. De  M.H. Engineer  Rabi N. Mukherjee  Sibaji Raha  S.C. Roy  Swapan K. Saha  A.K. Sen  Bikash Sinha  Debapriyo Syam 《Astrophysics and Space Science》1997,250(2):313-326

A Total Solar Eclipse (TSE) was observed from Diamond Harbour (lat. 22.2°N, long 88.2°E) on 24 October 1995. The variation of -ray intensity was measured in the energy range of 0.3–3.0 MeV for different time spans throughout the period of the eclipse. A CR-39 detector was used to look at the change in the fluxes of neutral and charged particles. The maximum drop ( 25%) in the intensity of -ray was observed in the range 2.5–3 MeV during TSE. The CR-39 results showed the appearance of a good number of tracks and a small variation of proton and neutron flux of 10% which was not significant statistically. Low energy -ray fluxes at sea level originate from the secondary electron-photon components of cosmic rays in the atmosphere; its modulation by TSE is interpreted as follows. The cooling of the atmosphere in the path of the umbra induces a reduction of the height of the main production layer of the nuclear component, as a result of which, fewer µ^± mesons (from the decay of the^± mesons) decay to e^±. This leads to a small reduction in the flux of electron-photon component at sea level which originates from this branch; the main branch of e - component from ⁰ decay remains nearly unaffected. As the total mass of air remains the same, little or no change in the slow proton or the neutron flux at sea level is expected. These are consistent with the present observations. For a better understanding, further studies of this new phenomenon during future TSE are suggested.  相似文献   

Effect of tsunamis from Makran Subduction Zone and its impact on the Androth Island of Lakshadweep     

Shila Saha  Kirti Srivastava 《Natural Hazards》2016,82(3):1755-1766

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Application of a New Symmetry-Based Cluster Validity Index for Satellite Image Segmentation   总被引：2，自引：0，他引：2  

Saha  S. Bandyopadhyay  S. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(2):166-170

An important approach for image segmentation is clustering pixels based on their spectral properties. In particular, satellite images contain land cover types, some of which cover significantly large areas, while some (e.g., bridges and roads) occupy relatively much smaller regions. Automatically detecting regions or clusters of such widely varying sizes presents a challenging task. In this letter, a symmetry-based cluster validity index, named Sym-index (Symmetry distance-based index), is proposed. It is able to correctly indicate the presence of clusters of different sizes as long as they are internally symmetrical. A genetic-algorithm-based clustering technique that optimizes the Sym-index is used for image segmentation where the number of clusters is determined automatically. The superiority of the proposed index, as compared to other indices, is established for automatically segmenting the land cover types from SPOT and Indian Remote Sensing satellite images of two different cities in India.  相似文献   

Arsenic mitigation by chitosan-based porous magnesia-impregnated alumina: performance evaluation in continuous packed bed column     

S. Saha  P. Sarkar 《International Journal of Environmental Science and Technology》2016,13(1):243-256

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