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Heavy metals in freshly deposited sediments of the river Subernarekha, India: an example of lithogenic and anthropogenic effects 总被引：1，自引：0，他引：1
A. K. Upadhyay K. K. Gupta J. K. Sircar M. K. Deb G. L. Mundhara 《Environmental Geology》2006,50(3):397-403
Heavy metal distribution patterns in river sediments aid in understanding the exogenic cycling of elements as well as in assessing the effect of anthropogenic influences. In India, the Subernarekha river flows over the Precambrian terrain of the Singhbhum craton in eastern India. The rocks are of an iron ore series and the primary rock types are schist and quartzite. One main tributary, the Kharkhai, flows through granite rocks and subsequently flows through the schist and quartzite layers. The Subernarekha flows through the East Singhbhum district, which is one of India’s industrialised areas known for ore mining, steel production, power generation, cement production and other related activities. Freshly deposited river sediments were collected upstream and downstream the industrial zone. Samples were collected from four locations and analysed in <63-μm sediment fraction for heavy metals including Zn, Pb, Cd and Cu by anodic stripping voltammetry. Enrichment of these elements over and above the local natural concentration level has been calculated and reported. Sediments of the present study are classified by Muller’s geo-accumulation index (I
geo) and vary from element to element and with climatic seasons. During pre-monsoon period the maximum I
geo value for Zn is moderately to highly polluted and for Cu and Pb is moderately polluted, respectively, based on the Muller’s standard. Anthropogenic, lithogenic or cumulative effects of both components are the main reasons for such variations in I
geo values. The basic igneous rock layer through which the river flows or a seasonal rivulet that joins with the main river may be the primary source for lithogenic components. 相似文献
2.
Highly heterogeneous Precambrian basement under the central Deccan Traps, India: Direct evidence from xenoliths in dykes 总被引：1，自引：0，他引：1
Ranjini Ray Anil D. Shukla Hetu C. Sheth Jyotiranjan S. Ray Raymond A. Duraiswami Loyc Vanderkluysen Chandramohan S. Rautela Jyotirmoy Mallik 《Gondwana Research》2008,13(3):375-385
Crustal or mantle xenoliths are not common in evolved, tholeiitic flood basalts that cover huge areas of the Precambrian shields. Yet, the occasional occurrences provide the most direct and unequivocal evidence on basement composition. Few xenolith occurrences are known from the Deccan Traps, India, and inferences about the Deccan basement have necessarily depended on geophysical studies and geochemistry of Deccan lavas and intrusions. Here, we report two basalt dykes (Rajmane and Talwade dykes) from the central Deccan Traps that are extremely rich in crustal xenoliths of great lithological variety (gneisses, quartzites, granite mylonite, felsic granulite, carbonate rock, tuff). Because the dykes are parallel and only 4 km apart, and only a few kilometres long, the xenoliths provide clear evidence for high small-scale lithological heterogeneity and strong tectonic deformation in the Precambrian Indian crust beneath. Measured 87Sr/86Sr ratios in the xenoliths range from 0.70935 (carbonate) to 0.78479 (granite mylonite). The Rajmane dyke sampled away from any of the xenoliths shows a present-day 87Sr/86Sr ratio of 0.70465 and initial (at 66 Ma) ratio of 0.70445. The dyke is subalkalic and fairly evolved (Mg No. = 44.1) and broadly similar in its Sr-isotopic and elemental composition to some of the lavas of the Mahabaleshwar Formation. The xenoliths are comparable lithologically and geochemically to basement rocks from the Archaean Dharwar craton forming much of southern India. As several lines of evidence suggest, the Dharwar craton may extend at least 350–400 km north under the Deccan lava cover. This is significant for Precambrian crustal evolution of India besides continental reconstructions. 相似文献
3.
Flood basalts, such as the Deccan Traps of India, represent huge, typically fissure-fed volcanic provinces. We discuss the
structural attributes and emplacement mechanics of a large, linear, tholeiitic dyke swarm exposed in the Nandurbar–Dhule area
of the Deccan province. The swarm contains 210 dykes of dolerite and basalt >1 km in length, exposed over an area of 14,500 km2. The dykes intrude an exclusively basaltic lava pile, largely composed of highly weathered and zeolitized compound pahoehoe
flows. The dykes range in length from <1 km to 79 km, and in thickness from 3 to 62 m. Almost all dykes are vertical, with
the others nearly so. They show a strong preferred orientation, with a mean strike of N88°. Because they are not emplaced
along faults or fractures, they indicate the regional minimum horizontal compressive stress (σ
3) to have been aligned ~N–S during swarm emplacement. The dykes have a negative power law length distribution but an irregular
thickness distribution; the latter is uncommon among the other dyke swarms described worldwide. Dyke length is not correlated
with dyke width. Using the aspect ratios (length/thickness) of several dykes, we calculate magmatic overpressures required
for dyke emplacement, and depths to source magma chambers that are consistent with results of previous petrological and gravity
modelling. The anomalously high source depths calculated for a few dykes may be an artifact of underestimated aspect ratios
due to incomplete along-strike exposure. However, thermal erosion is a mechanism that can also explain this. Whereas several
of the Nandurbar–Dhule dykes may be vertically injected dykes from shallow magma chambers, others, particularly the long ones,
must have been formed by lateral injection from such chambers. The larger dykes could well have fed substantial (≥1,000 km3) and quickly emplaced (a few years) flood basalt lava flows. This work highlights some interesting and significant similarities,
and contrasts, between the Nandurbar–Dhule dyke swarm and regional tholeiitic dyke swarms in Iceland, Sudan, and elsewhere.
Editorial responsibility: J. White 相似文献
4.
A. K. Upadhyay K. K. Gupta J. K. Sircar M. K. Deb G. L. Mundhara 《Environmental Geology》2007,51(8):1447-1453
The importance of study of heavy metal distribution in river sediments is a component in understanding the exogenic cycling
as well as in assessing the effect of anthropogenic influences of the elements. In India, the river Subernarekha flows over
Precambrian terrain of Singhbhum craton in the eastern India. The geological succession in this part of India is through (1)
iron ore series, (2) ultrabasic igneous rocks, (3) diorite, (4) granite, (5) newer dolerites, (6) newer tertiary and (7) alluvium.
The first four groups belong to the Archaean era, and the representative is the iron ore series consisting of iron ore, manganese
and chromite which are abundantly present. The primary rock types are schist and quartzite layers. One main tributary, the
Kharkhai flow through granite and schist and quartzite layers. Two important creeks are Gurma and Garra, respectively. The
former after originating in basic igneous area travels through schist quartzite, while the later one originates in granite
area where some functional but old gold mines are located. Freshly deposited sediments of river were collected upstream and
downstream the industrial zone (East Singhbhum district). Samples were collected from four locations and analysed in <63 μm
sediment fraction for heavy metals like Ni, Co and Cr by adsorption stripping voltammetry on hanging mercury drop electrode
and Hg by anodic stripping voltammetry using polished rotating gold disk electrode. Enrichment of these metals over and above
the local natural concentration level (NCL) has been calculated and applied to determine metal-pollution index (MPI) proposed
by Goncalves et al. and also geo-accumulation index (I
geo) by Muller. Based on Muller’s classification, Ni, Cr and Hg have been classified from unpolluted to moderately polluted range
in pre-monsoon period but for metals Ni and Cr, during the post-monsoon period the values have reached moderately polluted
level while Hg has been classified under unpolluted to moderately polluted level except at the monitoring station situated
upstream to Gurma Creek where it was found at unpolluted level. Presence of natural resources of the minerals is primarily
the reason for their detection in river sediments (lithogenic) but some anthropogenic sources are also contributing for their
presence at some sampling stations. Hg is considered to be chalcophilic in nature and is detected wherever known sulphidic
ores of copper or nickel are present. 相似文献
5.
‘Census Towns’ in India and what it means to be ‘urban’: Competing epistemologies and potential new approaches 
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下载免费PDF全文 Srilata Sircar 《Singapore journal of tropical geography》2017,38(2):229-244
The classification of 2 532 new settlements in the Census of India 2011 as ‘urban’, and specifically as ‘Census Towns’, has brought small and emerging urban centres back into the purview of urban studies and urban development in India. Taking this to be a point of entry, this article seeks to explore how the urban has been framed and approached from different and competing epistemological standpoints in the Indian context. First, it attempts to outline the different epistemologies of the urban in India, which may be seen as competing traditions because of the unequal stakes they have claimed so far in public and policy discourse. Then, it presents two brief case studies of Census Towns from the state of West Bengal to put forth new questions in this regard. The case studies illustrate significant gaps and discrepancies between the lived experience of the urban and its representation in dominant epistemological frameworks such as the official census. I argue that the historical development of various settlement systems, which constitutes the core narrative of urbanization in India, cannot be understood in all its complexity through mere census extracts or aerial images, but requires engagement with rich, embedded epistemologies that have taken shape within these settlements. 相似文献
6.
Jyotirmoy Mallik George Mathew Thomas Angerer Reinhard O. Greiling 《Journal of Geodynamics》2008,45(4-5):234-245
The Kachchh basin in the western India is known for its recent high seismicity. This study presents an application of the geogenic Electromagnetic Radiation (EMR) technique for deciphering the directions of principal horizontal stress in the eastern Kachchh. The principal direction of horizontal stress obtained from EMR differs from those obtained from earthquake focal plane solutions. The major horizontal principal stress based on the EMR study shows an azimuth of N60°E ± 10°. The principal directions of EMR emissions are parallel to the acute bisector of conjugate microcracks. The azimuthal distribution of EMR signal and dimension of microcracks suggest that the EM emissions are transversely polarized.The study also deals with the first application of electromagnetic radiation emissions to identify active fracture planes in sandstones that could become potential active faults later, which might be seismogenic or nonseimogenic. This study is based on linear profiling at six different places across two major faults, the Kachchh Mainland Fault (KMF) and the South Wagad Fault (SWF) in the eastern Kachchh. Anomalously, high EMR emissions are observed in the eastern part of the KMF, indicating active surface deformation. 相似文献
7.
Shah Manan Sircar Anirbid Shaikh Nahid Patel Karan Sharma Darshan Vaidya Dwijen 《中国地球化学学报》2019,38(1):145-158
Acta Geochimica - The knowledge of water temperature produced from a geothermal reservoir and its composition is of utmost importance in designing utilization strategies, the surface production... 相似文献
8.
Loss ratio, which is the ratio of the repair cost to the total replacement cost, is an effective parameter for representing structural and nonstructural damage caused by earthquakes. A probabilistic loss estimation framework is first presented that directly relates hazard to response and hence to losses. A key feature of the loss estimation approach is the determination of losses without need for customary fragility curves. Relationships between intensity measures and engineering demand parameters are used to define the demand model. An empirically calibrated loss model in the form of a power curve with upper and lower cut‐offs is used in conjunction with the demand model to estimate loss ratios. Loss ratios for each of the damage states take into account epistemic uncertainty and an effect on price surge following a major hazardous event. The loss model is calibrated and validated for bridges designed based on the prevailing Caltrans, Japan, and New Zealand standards. The loss model is then transformed to provide a composite seismic hazard–loss relationship that is used to estimate the expected annual loss for structures. The closed‐form four‐step stochastic loss estimation model is applied to the bridges designed for ductility. Results of these ductile designs are compared to a bridge detailed to an emerging damage avoidance design philosophy. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
9.
We present diagrams depicting the expected inter-dependences of two key kinematical parameters of radio knots in the parsec-scale
jets of blazars, deduced from VLBI observations. The two parameters are the apparent speed (υ
app = cβ
app) and the effective Doppler boosting factor (δ
eff) of the relativistically moving radio knot. A novel aspect of these analytical computations of β-δ diagrams is that they are made for parsec-scale jets having a conical shape, with modest opening angles (ω up to 10°), in accord with the VLBI observations of the nuclei of the nearest radio galaxies. Another motivating factor is
the recent finding that consideration of a conical geometry can have important implications for the interpretation of a variety
of radio observations of blazar jets. In addition to uniform jet flows (i.e., those having a uniform bulk Lorentz factor,
Γ), computational results are also presented for stratified jets where an ultra-relativistic central spine along the jet axis
is surrounded by a slower moving sheath, possibly arising from a velocity shear. 相似文献
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