Bioavailability of arsenic in the soil horizon: a laboratory column study     

Sudip Jyoti Sahu  Bibhash Nath  Sharmi Roy  Biswapati Mandal  Debashis Chatterjee 《Environmental Earth Sciences》2012,65(3):813-821

Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long-term detrimental effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable and fruits, are used for human consumption. Therefore, an understanding of the leaching behavior of As in surface soils is of high importance, because such behavior may increase the bioavailability of As in the soil horizon. In this study, we have investigated the role of phosphate ions in leaching and bioavailability of As in the soil horizon, where drinking groundwater contains elevated levels of As (≥50 μg/L). Soil and groundwater samples were characterized in the laboratory and measured for physical and chemical constituents. The soils are generally neutral to slightly alkaline in character (pH range 7.5–8.1) with low to moderate levels of free Fe₂O₃, Al₂O₃, CaCO₃, organic carbon, and clay content. The measured electrical conductivity (mean 599 μS/cm) of the soils demonstrates their non-saline nature. The Eh values (range −37 to −151 mV) of the groundwater indicate anoxic condition with low to moderate levels of bicarbonate (range 100–630 mg/L) and phosphate (range 0.002–4.0 mg/L). The arsenic content (range 50–690 μg/L; mean 321 μg/L) in groundwater has exceeded both WHO recommended guideline values (10 μg/L) and the National safe drinking water limit (50 μg/L). Regression analyses demonstrate that the bioavailability of As in the soil horizon is mainly controlled by the composition of free Fe₂O₃ and CaCO₃ content of the soils. However, application of P could increase bioavailability of As in the soil horizon and become available to plants for uptake.  相似文献   

Strange pulsar hypothesis     

Raka Dona Ray Mandal  Monika Sinha †  Manjari Bagchi  Sushan Konar  Mira Dey ‡  Jishnu Dey 《Monthly notices of the Royal Astronomical Society》2006,365(4):1383-1386

It appears that there is a genuine shortage of radio pulsars with surface magnetic fields significantly smaller than ∼10⁸ G. We propose that the pulsars with very low magnetic fields are actually strange stars locked in a state of minimum free energy and therefore at a limiting value of the magnetic field which cannot be lowered by the system spontaneously.  相似文献   

Cylindrical Zakharov–Kuznestov equation for ion-acoustic waves with electrons featuring non-extensive distribution     

Uday Narayan Ghosh  Pankaj Kumar Mandal  Prasanta Chatterjee 《Astrophysics and Space Science》2014,349(2):765-771

Cylindrical Zakharov–Kuznestov equation for ion-acoustic waves comprising of ions and electrons featuring non-extensive distribution are derived from the fluid equations through reductive perturbation technique. System of first order ordinary differential equations is obtained from Zakharov–Kuznestov equation through dynamical system approach and ultimately it is solved using numerical method. It is found that the electron to positron ratio parameter and the non-extensive distributed parameter due to electron play crucial role on the solution.  相似文献   

Zakharov–Kuznestov–Burger Equation for Ion-Acoustic Waves in Cylindrical Geometry     

Pankaj Kumar Mandal  Uday Narayan Ghosh  Prasanta Chaterjee 《Earth, Moon, and Planets》2015,115(1-4):45-58

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Seismogenesis of the uninterrupted occurrence of the aftershock activity in the 2001 Bhuj earthquake zone, Gujarat, India, during 2001�C2010     

Prantik Mandal 《Natural Hazards》2013,65(2):1063-1083

Seismogenesis of aftershocks occurring in the Kachchh seismic zone for more than last 10?years is investigated through modeling of fractal dimensions, b-value, seismic velocities, stress inversion, and Coulomb failure stresses, using aftershock data of the 2001 Bhuj earthquake. Three-dimensional mapping of b-values, fractal dimensions, and seismic velocities clearly delineate an area of high b-, D-, and Vp/Vs ratio values at 15?C35?km depth below the main rupture zone (MRZ) of the 2001 mainshock, which is attributed to higher material heterogeneities in the vicinity of the MRZ or deep fluid enrichment due to the release of aqueous fluid/volatile CO₂ from the eclogitisation of the olivine-rich lower crustal rocks. We notice that several aftershocks are occurred near the contacts between high (mafic brittle rocks) and low velocity regions while many of the aftershocks including the 2001 Bhuj mainshock are occurred in the zones of low velocity (low dVp, low dVs and large Vp/Vs) in the 15?C35?km depth range, which are inferred to be the fractured rock matrixes filled with aqueous fluid or volatiles containing CO₂. Further support for this model comes from the presence of hydrous eclogitic layer at sub-lithospheric depths (34?C42?km). The depth-wise stress inversions using the P- and T-axes data of the focal mechanisms reveal an increase in heterogeneity (i.e., misfit) with an almost N?CS ??₁ orientation up to 30?km depth. Then, the misfit decreases to a minimum value in the 30?C40?km depth range, where a 60^o rotation in the ??₁ orientation is also noticed that can be explained in terms of the fluid enrichment in that particular layer. The modeling of Coulomb failure stress changes (??CFS) considering three tectonic faults [i.e., NWF, GF, and Allah bund fault (ABF)] and the slip distribution of the 2001 mainshock on NWF could successfully explain the occurrences of moderate size events (during 2006?C2008) in terms of increase in positive ??CFS on GF and ABF. In a nutshell, we propose that the fluid-filled mafic intrusives are acting as stress accentuators below the Kachchh seismic zone, which generate crustal earthquakes while the uninterrupted occurrence of aftershocks is triggered by stress transfer and aqueous fluid or volatile CO₂ flow mechanisms. Further, our results on the 3-D crustal seismic velocity structure, focal mechanisms, and b-value mapping will form key inputs for understanding wave propagation and earthquake hazard-related risk associated with the Kachchh basin.  相似文献   

Estimation of Wheat/Rice Residue Burning Areas in Major Districts of Haryana,India, Using Remote Sensing Data     

Manoj Yadav  M. P. Sharma  R. Prawasi  Rajeev Khichi  Pavan Kumar  V. P. Mandal  Abdul Salim  R. S. Hooda 《Journal of the Indian Society of Remote Sensing》2014,42(2):343-352

Haryana has emerged as an important state for Rice & Wheat production in India contributing significantly in the central pool. Mechanized combine harvesting technologies, which have become common in Rice Wheat System (RWS) in India, leave behind large quantities of straw in the field for open burning of residue. Besides causing pollution, the burning kills the useful micro flora of the soil causing soil degradation. There is no field survey (Girdawari) data available with the Government for the areas where stubble burning is taking place. The present paper describes the methodology and results of wheat and rice residue burning areas for three districts of Haryana namely Kaithal, Kurukshetra and Karnal for the year 2010 using complete enumeration approach of multi-date IRS-P6 AWiFS and LISS-III data. In season ground truth was collected using hand held GPS and used to identify area of burnt wheat/rice residues, associated crops and land features. After geo-referencing the satellite images, district images were masked-out and multi-date image data stacks were created. Normalized Difference Vegetation Index (NDVI) of each date was generated and used at the time of classification along with other spectral bands. The non-agricultural classes in the image included: forest, wasteland, water bodies, urban/settlement and permanent vegetation etc. The vector of these non-agriculture classes were extracted from the land use, imported and mask was generated. During the classification non-agriculture area was excluded by using mask of these classes. From this the agricultural area could be separated out. The area was estimated by computing pixels under the classified image mask. In season multi-date AWiFS data along with available single-date LISS-III data between third week of April to last week of May are found to be useful for estimation of wheat residue burning areas estimation. The data between second week of October to last week of November is useful for estimation of rice residue burning areas estimation at district level.  相似文献   

Delineation and characterization of waterlogging and salt affected areas in a canal irrigated semiarid region of north west India     

A. K. Mandal  R. C. Sharma 《国际地球制图》2013,28(3):181-195

Indian Remote Sensing (IRS) Linear Imaging Self Scanning (LISS II) data are interpreted, followed by ground verification facilitated identification of waterlogged areas (ponded water), salt affected soils (salt efflorescence) and high water table zones (potential waterlogging zones) in the Indira Gandhi Nahar Pariyojona (IGNP) command area (India). The false colour composites (bands 4, 3, 2) for February 1996, November 1996 and June 1998 on 1:50 000 scale revealed occurrence and seasonal dynamics of permanent waterlogging in low-lying flats and depressions. The extent of waterlogging was higher in February 1996 due to less evaporation and more agricultural operation during the period. Salt accumulation was higher in November 1996 due to freshly precipitated seasonal salts. Seepage and accumulation of excess irrigation water through coarse sandy mass was primarily responsible for the development of waterlogging in the irrigated zone. The capillary rise of soluble salts with a rising water table and high evaporative demand caused secondary soil salinization. A ground truth study found areas with a high water table (<1.5 m) with patchy crop stands and a potentially sensitive zone with a fluctuating (1.5–6.0 m) water table with poor vegetative growth. The soil characteristics showed moderate to high soil salinity in the control section of soil profiles. These were characterized by medium to coarse texture, weak to moderately strong structure, weak consistency, low organic matter content and the presence of abundant CaCO₃ nodules. The composition of saturated soil paste showed a preponderance of chlorides and sulphates of sodium, calcium and magnesium. The presence of fine texture and calcium carbonate layers at a depth below the surface caused the development of a perched water table indicating unsuitability for traditional irrigated agriculture. The quality of pond water was extremely poor and unfit for reuse. The ground water was saline in some areas but normally lies within the prescribed limit. The quality of drainage water was poor in saline depressions and unsuitable for reuse but moderate in other areas suggesting its safe reuse when mixed with good quality water. Suitable soil and water management practices were necessary for sustainable crop production in the command area.  相似文献   

Geophysical signatures of uranium mineralization and its subsurface validation at Beldih,Purulia District,West Bengal,India: a case study          下载免费PDF全文

Animesh Mandal  W.K. Mohanty  S.P. Sharma  Arkoprovo Biswas  Joydip Sen  A. K. Bhatt 《Geophysical Prospecting》2015,63(3):713-726

The Beldih open cast mine of the South Purulia Shear Zone in Eastern India is well known for apatite deposits associated with Nb–rare‐earth‐element–uranium mineralization within steeply dipping, altered ferruginous kaolinite and quartz–magnetite–apatite rocks with E–W strikes at the contact of altered mafic–ultramafic and granite/quartzite rocks. A detailed geophysical study using gravity, magnetic, and gradient resistivity profiling surveys has been carried out over ～1 km² area surrounding the Beldih mine to investigate further the dip, depth, lateral extension, and associated geophysical signatures of the uranium mineralization in the environs of South Purulia Shear Zone. The high‐to‐low transition zone on the northern part and high‐to‐low anomaly patches on the southeastern and southwestern parts of the Bouguer, reduced‐to‐pole magnetic, and trend‐surface‐separated residual gravity–magnetic anomaly maps indicate the possibility of highly altered zone(s) on the northern, southeastern, and southwestern parts of the Beldih mine. The gradient resistivity survey on either side of the mine has also revealed the correlation of low‐resistivity anomalies with low‐gravity and moderately high magnetic anomalies. In particular, the anomalies and modeled subsurface features along profile P6 perfectly match with subsurface geology and uranium mineralization at depth. Two‐dimensional and three‐dimensional residual gravity models along P6 depict the presence of highly altered vertical sheet of low‐density material up to a depth of ～200 m. The drilling results along the same profile confirm the continuation of uranium mineralization zone for the low‐density material. This not only validates the findings of the gravity model but also establishes the geophysical signatures for uranium mineralization as low‐gravity, moderate‐to‐high magnetic, and low‐resistivity values in this region. This study enhances the scope of further integrated geophysical investigations along the South Purulia Shear Zone to delineate suitable target areas for uranium exploration.  相似文献   

A unified earthquake catalogue for South Asia covering the period 1900–2014     

Nath  Sankar Kumar  Mandal  Suman  Das Adhikari  Manik  Maiti  Soumya Kanti 《Natural Hazards》2017,85(3):1787-1810

Seismicity analysis is very much pertinent for Indian subcontinent and its adjoining region which is seismically active including many great earthquakes associated with collision and subduction tectonics in the northern, north-eastern part of the subcontinent and in the Andaman and Nicobar Island. An earthquake catalogue has been generated for South Asia covering the period 1900–2014 by compiling the records of earthquake occurrences from International Seismological Center, Global Centroid Moment Tensor (GCMT), US Geological Survey, India Meteorological Department and published literature. The uniform magnitude scaling in moment magnitude M _W,GCMT is achieved through connecting relationships between different magnitude types. These relationships are derived by orthogonal standard regression analysis on available data pairs. The derived relationships have been compared with the existing equations already reported by others. The catalogue is subsequently subjected to a seismicity declustering algorithm to identify the foreshocks, main-shocks and aftershocks. The catalogue thus compiled is envisaged to be a useful resource for seismotectonic and seismic hazard studies in the region.

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Modeling of source parameters and moment tensors of local earthquakes occurring in the eastern Indian shield     

Koushik Biswas  Prantik Mandal 《Journal of the Geological Society of India》2017,89(6):619-630

Earthquake source parameters and crustal Q are being estimated simultaneously through the inversion of S-wave displacement spectra from three-component recordings of ten local cratonic intraplate earthquakes from 3-6 broadband stations in the eastern Indian shield, wherein, an iterative Levenberg-Marquardt inversion technique is used. The estimated seismic moment (M_o) and source radii (r) vary from 7.4 x 10¹² to 7.1 x 10¹⁴ N-m and 144.2 to 211.3 m, respectively, while estimated stress drops (Δσ) and multiplicative factor (E_mo) values range from 0.11 to 4.13 MPa and 1.33 to 2.16, respectively. The corner frequencies range from 6.23 to 8.62 Hz while moment magnitudes vary from 2.44 to 3.57. The radiated seismic energy and apparent stresses range from 8.3 x 10⁶ to 2.0 x 10¹⁰ Joules and 0.06 to 0.94 MPa, respectively, wherein the estimated corner frequencies and seismic moment satisfy the relation Mo ∞ f _c ^–(3+ε) for ε = 12.7. Thus, the source scaling of these events clearly deviates from the self-similarity i.e. f^–3. Estimated Zuniga parameters reveal that all selected events satisfy the partial stress drop model, which is in good agreement with the global observations. Our estimated crustal S-wave quality factors vary from 1091 to 4926 with an average of 3006, suggesting a less heterogeneous crustal structure underlying the study region.We also perform moment tensor inversion of five selected local events using ISOLA software, which reveals that the dominant deformation mode for the eastern Indian shield is left-lateral strike slip motion with minor normal dip-slip component on an almost vertical plane. This observation suggests that neotectonic vertical movements might have played a key role in generating these earthquakes. Our modeling also depicts that the seismically mildly active Singhbhum shear zone and Eastern Ghats mobile belt are characterized by the left-lateral strike motion while two events in the Chotanagpur half graben belt suggest a normal dip-slip motion along a south dipping plane. A north-south orientation of P-axis is found to be dominant in the area, which is consistent with the prevailing north–south compression over the Indian plate.  相似文献