International dune atlas meeting     

H. S. Saini  Nilesh Bhatt  Pradeep Srivastava 《Journal of the Geological Society of India》2012,80(5):742-742

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Soil chemical changes resulting from irrigating with petrochemical effluents   总被引：1，自引：0，他引：1  

N. K. Sharma  S. Bhardwaj  P. K. Srivastava  Y. J. Thanki  P. K. Gadhia  M. Gadhia 《International Journal of Environmental Science and Technology》2012,9(2):361-370

Irrigating food crops with treated wastewater is a popular management option in India. This study evaluated the impacts of land application of treated petrochemical effluent on soil chemical properties. Soil samples were collected from different depths from sites irrigated with petrochemical effluent for 2?years and from control sites. The effluent collected was analysed for different physic?Cchemical properties and its impact on Lagenaria siceraria (Bottle gourd) growth. 100% concentrated effluent was used for the study and compared with the control. It was observed that application of effluent significantly increased the major cations and anions in the field. On the basis of the study, it may be suggested that treated petrochemical effluent can be used as an alternate source for irrigating crops as it increases the nutrient content of the soil. The overall application indicates a lavishing growth of L. siceraria crop in petrochemical irrigated soil than control sites. This study provides information for better understanding of changes in soil properties due to land application of petrochemical effluent. These changes must be considered in developing possible criteria for preserving delicate ecosystems.  相似文献   

Assimilation of Indian Doppler Weather Radar observations for simulation of mesoscale features of a land-falling cyclone     

Kuldeep Srivastava  Rashmi Bhardwaj  S. K. Roy Bhowmik 《Natural Hazards》2011,59(3):1339-1355

In this paper, impact of Indian Doppler Weather Radar (DWR) data, i.e., reflectivity (Z), radial velocity (Vr) data individually and in combination has been examined for simulation of mesoscale features of a land-falling cyclone with Advance Regional Prediction System (ARPS) Model at 9-km horizontal resolution. The radial velocity and reflectivity observations from DWR station, Chennai (lat. 13.0°N and long. 80.0°E), are assimilated using the ARPS Data Assimilation System (ADAS) and cloud analysis scheme of the model. The case selected for this study is the Bay of Bengal tropical cyclone NISHA of 27–28 November 2008. The study shows that the ARPS model with the assimilation of radial wind and reflectivity observations of DWR, Chennai, could simulate mesoscale characteristics, such as number of cells, spiral rain band structure, location of the center and strengthening of the lower tropospheric winds associated with the land-falling cyclone NISHA. The evolution of 850 hPa wind field super-imposed vorticity reveals that the forecast is improved in terms of the magnitude and direction of lower tropospheric wind, time, and location of cyclone in the experiment when both radial wind and reflectivity observations are used. With the assimilation of both radial wind and reflectivity observations, model could reproduce the rainfall pattern in a more realistic way. The results of this study are found to be very promising toward improving the short-range mesoscale forecasts.  相似文献   

Storm activities during the sedimentation of late Paleocene-middle Eocene Subathu Formation,western Himalayan foreland basin     

B. P. Singh  A. K. Srivastava 《Journal of the Geological Society of India》2011,77(2):130-136

Late Paleocene-middle Eocene Subathu Formation represents the earliest deposits of the western Himalayan foreland basin. A large part of this formation is comprised of impure limestone and grey shale intercalations. The limestones contain sole marks, intraformational conglomerates, hummocky cross stratification and wave ripples. The occurrence of sole marks suggests that they are developed by the unidirectional currents at the initial phase of the storm that resulted erosion and subsequent deposition. The intraformational limestone conglomearate also suggests erosion of the earlier deposited limestone hardgrounds as a consequence of storm associated transgression. The hummocky cross stratification formed by the oscillatory flows during the long-shore littoral drift. The depth of formation of the hummocky cross stratified limestone facies was less than 40 m and most likely deposited between shore-face to backshore regions of the gulf similar to present day Persian Gulf. The identification of deeper facies (shelf facies) from Pakistan and coastal facies from India suggest that the gulf was open from the west and closed from the east.  相似文献   

Mineral chemistry of clays associated with the Jhilmili intertrappean bed in the eastern Deccan volcanic province: Palaeoenvironmental inferences and KTB transition     

Sucharita Pal  Surabhi Srivastava  J. P. Shrivastava 《Journal of the Geological Society of India》2013,82(1):38-52

Jhilmili intertrappean bed (～13 m thick) attains its significance with the recent discovery of brackish water ostrocod and planktonic foraminifera fossils (Keller et al. 2009; Khosala et al. 2009). Present XRD data revealed abundance of montmorillonite > montmorillonite/chlorite mixed layer > palygorskite in five physically distinct lithounits namely: (a) lower chocolate brown siltstone with green patches, followed by (b) brick red clayey siltstone, (c) greenish grey clay, (d) yellowish brown clay and (e) uppermost olive grey to dark brown silt layers in the successionrepresent higher weathering indices and annual precipitation, reflecting cyclic, but longer spells of weathering. Occurrence of M/C mixed layer with the smectite in Jhilmili area is suggestive of their derivation from the later, whilst montmorillonite to palygorskite transformation is ascribed to the drastic changes in the humid to arid climate, where former served as a source of Al and some of the Si and Mg ions for the later. Jhilmili and Anjar clays represent similar charge occupancies at different sites, but later contains relatively higher amount of palygorskite, formed in the arid environment. Majority of the trace elemental data plots for Jhilmili clays lie within the upper and lower limits of infra (Lametas)-/inter-trappeans clays. The continuous release of Cu throughout the succession (mainly in the palygorskite dominated clays) indicates oxidizing conditions. PAAS normalized REE data plots for these clays show progressive enrichment in the HREE contents in the lower part, but, upper part of the succession is marked by positive cerium anomaly, reflecting oxidizing conditions prevailed at the later stage of the succession. These conditions continued, but, were not conducive to HREE enrichment as evidenced by their depletion in the upper part of the succession. The Ce anomaly observed in the middle part of the succession is similar to that form by continental weathering of the basalt, ascribed to Ce precipitation in the oxic environment, thus suggestive of drastic changes in the oxidizing conditions. Thermodynamic data-sets for Jhilmili clays show I/S mixed layer and celadonite compositions, whereas, Jabalpur infra-/inter-trappean clays correspond to Mg smectites and celadonite end members, thus, representing compositional commonality with those of the other clays derived from the continental weathering of basalt protolith. Jhilmili smectites and smectite-chlorite mixtures show compositional similarity with the dioctahedral and trioctahedral smectites and the smectites formed at 250°C, having compositions between trioctahedral smectite and chlorite, thus, assigning high temperatures for their formation, where the heat required for the formation of these clays was possibly derived from the hydrothermal fluids, associated with the Deccan volcanism.  相似文献   

Geochemistry of Proterozoic granitoids exposed between Dirang and Tawang, western Arunachal Himalaya, north-eastern India: petrogenetic and tectonic significance     

Rajesh K. Srivastava 《International Journal of Earth Sciences》2013,102(7):2043-2060

Major and trace element geochemistry of Proterozoic granitoids from the Dirang and Galensiniak Formations, of Lesser and Higher Himalayas, respectively, emplaced in and around Dirang and Tawang regions of the western Arunachal Himalaya, is discussed. In general, these granitoids are massive as well as foliated in nature and are characterized by granitic mineralogical compositions. Porphyritic and hypidiomorphic textures are common in massive type, whereas others show porphyroblastic and foliated textures. Augen structure is also observed in a number of samples. Geochemical and normative compositions together with petrographic features classify them as peraluminous granitoids. Major and trace element geochemistry of most of these granitoids shows granitic nature, while few samples also show monzonitic characteristics. Observed geochemical characters, such as their peraluminous and alkali-calcic/calcic-alkalic nature, crudely defined geochemical patterns, different multi-element and rare-earth element patterns, together with low Mg# (Mg number) of these granitoids suggest their derivation from lower crustal material rather than a mantle source. Multi-element and rare-earth element patterns corroborate their genesis from different crustal melts. It is difficult to explain variations observed in granitoid rocks by partial melting alone; definitely different other processes like migration of melts, magma mixing, assimilation and fractional crystallization also played important role in the genesis of these granitoids. These melts were likely generated at low temperature (730–760 °C) and low pressure (2–5 GPa). The chemical compositions suggest that most of these Paleoproterozoic granitoids are emplaced within the syn-collisional tectonic setting, while few granitoid samples also indicate their volcanic-arc nature. Probably, later group of granitoids are slightly younger to the syn-collisional type.  相似文献   

Temperature of interstellar warm ionized medium     

Sanjay K. Mishra  Mahendra Singh Sodha  Sweta Srivastava 《Astrophysics and Space Science》2013,344(1):193-203

This investigation on the temperature of the interstellar warm ionized medium (WIM) is characterized by the number and energy balance of the constituents of the WIM complex plasma viz. H plasma (electrons/ions/neutral atoms) and graphite dust, having a size distribution, characterized by the MRN (Mathis, Rumpl and Nordsieck) power law. Ionization of neutral atoms, electron–ion recombination, photoemission of electrons from and accretion on the dust and cooling through electron collisional excitation, followed by radiative decay of atoms has been included in the analysis. An appropriate expression for the rate of emission and mean energy of photoelectrons emitted from the surface of positively charged dust particles has been used which takes into account the dependence of absorption efficiency on wavelength of the radiation, radius of the particle and spectral irradiance distribution. The results of the parametric analysis have been displayed graphically. It is seen that the consensus values of temperature, surface potential on the dust particles and electron/ion/neutral atom densities, characteristic of interstellar warm ionized medium can be explained on the basis of plausible combinations of the dust particle density n _d and the parameter f _ex α _ex , where f _ex is the fraction of the energy of the neutral gas atoms which gets irradiated, α _ex n _e n _n is the number of the neutral atoms, which get excited per unit volume per unit time and n _e (n _n ) correspond to the density of electrons (neutral atoms).  相似文献   

Luminescence chronology of river adjustment and incision of Quaternary sediments in the alluvial plain of the Sabarmati River, north Gujarat, India   总被引：1，自引：0，他引：1  

Pradeep Srivastava  Navin Juyal  Ashok K. Singhvi  Robert J. Wasson  Mark D. Bateman 《Geomorphology》2001,36(3-4)

River adjustment and incision in the Sabarmati basin, Gujarat, India have been examined at a site near Mahudi. Towards this, the morphostratigraphy and depositional chronometry of the middle alluvial plains were investigated. The upper fluvial sequence, along with the overlying aeolian sand and riverbed scroll plains, provide clues to the evolution of the present Sabarmati River. Sedimentological analyses of the upper fluvial sequence indicate its deposition by a meandering river system during what is believed to be a persistent wetter phase. Luminescence chronology bracketed this sequence to between 54 and 30 ka, which corresponds to Oxygen Isotope Stage-3, during which the SW monsoon was enhanced. The overlying aeolian sand has been dated to 12 ka, indicating that dune accretion occurred simultaneously with the strengthening of the SW monsoon during the Early Holocene. Adjustment of the Sabarmati along a N–S transect is placed around 12 ka and the incision is bracketed between 12 and 4.5 ka. River adjustment could have been tectonic; however, the incision was facilitated by the availability of continuous flow in the river caused by the SW monsoon. The basin experienced two tectonic events at about 3 and 0.3 ka, as demonstrated by the morphology of the scroll plains.  相似文献   

The AD 1362 Öræfajökull eruption,S.E. Iceland: Physical volcanology and volatile release     

Kirti Sharma  Stephen Self  Stephen Blake  Thorvaldur Thordarson  Gudrun Larsen 《Journal of Volcanology and Geothermal Research》2008

The explosive rhyolitic eruption of Öræfajökull volcano, Iceland, in AD 1362 is described and interpreted based on the sequence of pyroclastic fall and flow deposits at 10 proximal locations around the south side of the volcano. Öræfajökull is an ice-clad stratovolcano in south central Iceland which has an ice-filled caldera (4–5 km diameter) of uncertain origin. The main phase of the eruption took place over a few days in June and proceeded in three main phases that produced widely dispersed fallout deposits and a pyroclastic flow deposit. An initial phase of phreatomagmatic eruptive activity produced a volumetrically minor, coarse ash fall deposit (unit A) with a bi-lobate dispersal. This was followed by a second phreatomagmatic, possibly phreatoplinian, phase that deposited more fine ash beds (unit B), dispersed to the SSE. Phases A and B were followed by an intense, climactic Plinian phase that lasted ∼ 8–12 h and produced unit C, a coarse-lapilli, pumice-clast-dominated fall deposit in the proximal region. At the end of Plinian activity, pyroclastic flows formed a poorly-sorted deposit, unit D, presently of very limited thickness and exposed distribution. Much of Eastern Iceland is covered with a very fine distal ash layer, dispersed to the NE. This was probably deposited from an umbrella cloud and is the distal representation of the Plinian fallout. A total bulk fall deposit volume of ∼ 2.3 km³ is calculated (∼ 1.2 km³ DRE). Pyroclastic flow deposit volumes have been crudely estimated to be < 0.1 km³. Maximum clast size data interpreted by 1-D models suggests an eruption column ∼ 30 km high and mass discharge rates of ∼ 10⁸ kg s^− 1. Ash fall may have taken place from heights around 15 km, above the local tropopause (∼ 10 km), with coarser clasts dispersed below that under a different wind regime. Analyses of glass inclusions and matrix glasses suggest that the syn-eruptive SO₂ release was only ∼ 1 Mt. This result is supported by published Greenland ice-core acidity peak data that also suggest very minor sulphate deposition and thus SO₂ release. The small sulphur release reflects the low sulphur solubility in the 1362 rhyolitic melt. The low tropopause over Iceland and the 30-km-high eruption column certainly led to stratospheric injection of gas and ash but little sulphate aerosol was generated. Moreover, pre-eruptive and degassed halogen concentrations (Cl, F) indicate that these volatiles were not efficiently released during the eruption. Besides the local pyroclastic flow (and related lahar) hazard, the impact of the Öræfajökull 1362 eruption was perhaps restricted to widespread ash fall across Eastern Iceland and parts of northern Europe.  相似文献   

Prediction of SST anomalies of east Pacific Ocean (Nino 3 region) using a statistical model     

A. K. Srivastava  K. C. Sinha Ray 《Theoretical and Applied Climatology》2000,66(3-4):131-138

Summary  Average SST anomalies of OCT-DEC months for Nino-3 region are predicted using the following parameters – (i) April rain over Himachal Pradesh, (ii) Darwin pressure change (January–April), (iii) Southern Oscillation Index (Tahiti–Darwin) and (iv) SST anomalies of Nino-3 region in the month of May. Principal component analysis is used to orthogonalise the predictors before using them in the regression equation. The first two principal components, which explain nearly 73% of the variance, are used to fit a regression line. The period 1951–1985 is used as the calibration period for the model and the period 1986–1997 as the verification period for the forecast. The Brier score with respect to a reference forecast (persistence) for the independent period is found to be 0.82 which is indicative of good forecast skill. Received April 1, 1999 Revised January 17, 2000  相似文献