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291.
Heavy metal pollution assessment through comparison of different indices in sewage-fed fishery pond sediments at East Kolkata Wetland,India 总被引:3,自引:0,他引:3
Subhasis Sarkar Phani Bhusan Ghosh Alok Kumar Sil Tapan Saha 《Environmental Earth Sciences》2011,63(5):915-924
The sediments of the raw sewage-fed fishpond system at East Kolkata Wetland (EKW) were analyzed for heavy metal content in
a comprehensive way. Various indices of contamination like enrichment factor (EF), geo-chemical index (I
geo), modified degree of contamination (mDC), and pollution load index (PLI) were assessed. In all cases, instead of literature values, the metal concentrations of less
contaminated sites, separated by the statistical approach of the hierarchical cluster analysis, were used as baseline values.
In the present study, about 70% of the pond sediments are found uncontaminated, 5% display low degree of contamination and
25% are designated as moderate degree of contamination. Both the EF and I
geo indices highlighted that the metals lead (Pb), cadmium (Cd), and chromium (Cr) are responsible for the contamination while
there is little anthropogenic input in cases of Cu, Zn, and Ni. Most of the ponds situated near the main sewage flowing canals
as well as the main traffic highway and close to the solid waste dumping areas recorded higher degree of metal contamination
as evident from spatial variation of mDC and PLI indices in the study area. Indices comparison study clearly indicates that although these are calculated using different
methods, these may or may not produce the same indices values and hence the values should neither be compared nor be averaged.
But all the above indices are directly related to a common term contamination factor (CF). Classification of contamination
levels based on these CF values is found to be similar and this classification is only valid up to the level of high degree
of contamination. Thus, the use of any one of these indices is sufficient to classify the degree of contamination of an area.
However, to evaluate the contamination per metal, both I
geo and EF are effective while, to assess the composite effect of all the metals, PLI is preferable to mDC. 相似文献
292.
Ecological consideration of trace element contamination in sediment cores from Sundarban wetland,India 总被引:2,自引:1,他引:1
E. V. Silva Filho M. P. Jonathan M. Chatterjee S. K. Sarkar S. M. Sella A. Bhattacharya K. K. Satpathy 《Environmental Earth Sciences》2011,63(6):1213-1225
This article reports on the concentration of selected trace elements (Mn, Zn, Cr, Cu, Ba, As, B, V, and Hg) and major elements
(Fe and Al) from the intertidal sediment cores from Sundarban wetland, India. This is a typical meso-macrotidal estuarine
area affected by domestic and industrial activities located upstream. The overall concentrations range is low to moderate,
indicating the environmental conditions in the outfall zone (grain size, hydrodynamic regime, and confinement), which favors
the in situ accumulation of pollutants. The extent of contamination from trace elements in Sundarban core sediments is evaluated
through a two-pronged approach: (i) by determining the metal enrichment in the sediments through the calculation of Pollution
Load Index (PLI), Enrichment Factor (EF) and Index of Geoaccumulation (I
geo), and (ii) by defining a potential level of biological risk by the use of quality criteria such as Threshold Effect Level
(TEL) and Effects Range-Low (ERL) benchmarks. On the basis of the calculated indices, sediments are particularly enriched
with Cr, Cu, B, V, and As. Those enrichments seem to be due to the fine granulometry of the regions with Fe and Mn oxi-hydroxides
being the main metal carriers. Trace Elements input to the Sundarban wetland need to be kept under strict control in future
specially with reference to As since, according to TEL and ERL benchmarks, it already appears to be associated with a potential
biological risk. 相似文献
293.
294.
Kui-Chitraseni Shear Zone of the Precambrian Aravalli Mountain, NW India is marked by a nearly 400 m-wide NE-SW trending belt of cataclasites developed on the granites and metasediments of the Delhi Supergroup. The cataclasites are criss crossed by pseudotachylite and fissure-veins. While the pseudotachylites are aphanitic to microlitic, the fissure veins are characterized by syntaxial-bitaxial as well as unitaxial growth of elongate quartz grains. Textural study of the fissure veins suggests crystallization of quartz grains in a dilational environment in hydrous condition. Contrarily the pseudotachylites bear the evidence of frictional melting of rocks under anhydrous conditions. Since in many instances it is observed that the fissure veins have replaced the pseudotachylites following the crack seal mechanism, the formation of fissure veins is considered to be latekinematic to pseudotachylites. Hence it is interpreted that the pseudotachylites and fissure veins were formed in two distinct tectonic events. While pseudotachylites were formed in a compressional setting resulted from thrusting along the shear zone, the fissure veins have been formed in an extensional setting during a late stage normal faulting. In light of this tectonic rejuvenation along the Kui-Chitraseni Shear Zone, various lineaments present within the Aravalli Mountains need further study for understanding the evolution of the region. 相似文献
295.
The southwestern part of south Shillong plateau (Meghalaya, N-E India), designated as Sylhet Limestone Group is sub-divided into three lithounits i.e., Lakadong, Umlatdoh and Prang formations in ascending order. The Prang Formation is the youngest lithostratigraphic unit of the Sylhet Limestone Group and has been dated as Middle to early Upper Eocene based on the benthic foraminifera studies. Thin section analysis of carbonate rocks from Prang Formation, exposed in the Bholaganj limestone quarry yielded a rich assemblage of calcareous algae. The coralline algal assemblage comprises both non-geniculate and geniculate forms. The green algae are represented by species of Halimeda belonging to the family Halimedaceae. Palaeoecological interpretation based on diversity, growth-form analysis and taphonomic aspects of the algal assemblage indicate that in all probabilities the deposition of Prang Formation occurred in shallow, warm, shelf environment of normal salinity within the transgressive phase. 相似文献
296.
Olatz Zuloaga Ailette Prieto Kawser Ahmed Santosh Kumar Sarkar Asokkumar Bhattacharya Mousumi Chatterjee Bhaskar Deb Bhattacharya Kamala Kanta Satpathy 《Environmental Earth Sciences》2013,68(2):355-367
The present work is the first attempt to compare the data of a comprehensive study of the origin and distribution of 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) in surface sediments (<63 μm) from 18 sampling stations, 9 from Sundarban of Bangladesh and 9 from Indian counterpart. Σ19PAHs concentration in sediments showed wide variations from 208.3 to 12,993.1 ng g?1 dry weight in Indian Sundarban, whereas 208.4 to 4,687.9 ng g?1 in the case of Bangladesh. Fluoranthene, pyrene, benzo(b)fluoranthene, benzo(a)pyrene and dibenzo(a,h)anthracene were predominant species for both the countries. The PAH diagnostic ratios indicated that the PAHs in sediments from both the countries were of mixed source of hydrocarbons of both petrogenic and pyrolytic origin. According to the numerical effect-based sediment quality guidelines, the levels of PAHs in the Sundarban wetland of Bangladesh and India should not exert adverse biological effects. The TEQ values calculated for samples from the Bangladesh and Indian Sundarban varied from 13.68 to 1,014.75 and 1.31 to 2,451 ng g?1 d.w. with an average of 221.02 and 358.63 ng g?1, respectively. The overall contamination status of PAH was higher in India than Bangladesh. 相似文献
297.
Shailesh Agrawal Prasanta Sanyal Anindya Sarkar Manoj Kumar Jaiswal Koushik Dutta 《Quaternary Research》2012,77(1):159-170
Oxygen and carbon isotope ratios of soil carbonate and carbon isotope ratios of soil organic matter (SOM) separated from three cores, Kalpi, IITK and Firozpur, of the Ganga Plain, India are used to reconstruct past rainfall variations and their effect on ambient vegetation. The δ18O values of soil carbonate (δ18OSC) analyzed from the cores range from ? 8.2 to ? 4.1‰. Using these variations in δ18OSC values we are able, for the first time, to show periodic change in rainfall amount between 100 and 18 ka with three peaks of higher monsoon at about 100, 40 and 25 ka. The estimation of rainfall variations using δ18O value of rainwater-amount effect suggests maximum decrease in rainfall intensity (~ 20%) during the last glacial maximum. The δ13C values of soil carbonate (δ13CSC) and SOM (δ13CSOM) range from ? 6.3 to + 1.6‰ and ? 28.9 to ? 19.4‰, respectively, implying varying proportions of C3 and C4 vegetations over the Ganga Plain during the last 100 ka. The comparison between monsoonal rainfall and atmospheric CO2 with vegetation for the time period 84 to 18 ka indicate that relative abundances of C3 and C4 vegetations were mainly driven by variations in monsoonal rainfall. 相似文献
298.
Studies on the variations of heavy metals in the marine sediments off Kalpakkam,East Coast of India 总被引:1,自引:1,他引:0
K. K. Satpathy A. K. Mohanty M. V. R. Prasad Usha Natesan S. K. Sarkar 《Environmental Earth Sciences》2012,65(1):89-101
During the last two decades, the coastal environment of southeast India has experienced intense developments in industry,
urbanization and aquaculture. Moreover, the 2004 mega tsunami has devastated this coast, thus affecting the coastal sediment
characteristics. These two phenomena prompted a study to characterize the sediment, to understand the mechanisms influencing
the distribution of heavy metals and to create baseline data for future impact assessment. Results showed that the coastal
sediment was carpeted with a mosaic of sand and silty sand with a minor amount of clay. Heavy metal values showed maximum
variation for Fe and minimum for Cd. Their average values showed the following decreasing trend: Fe > Cu > Zn > Pb > Cr > Ni > Cd.
This study shows that the major source of metals at Kalpakkam coast are land-based anthropogenic ones, such as, discharge
from industrial waste, agricultural waste, urban, municipal and slum sewage into the Buckingham canal, which in turn discharges
into the sea through backwaters, particularly during northeast monsoon period. A clear signature of the role of backwater
discharge increasing the concentration of a few metals in the coastal sediments during monsoon period was observed. Assessments
of the degree of pollution, concentration factor (CF), geoaccumulation index (I
geo) and pollution load index (PLI) have been calculated. CF values and I
geo indicated that the coastal sediment is moderately polluted by Cu and Cd. Increase in Cu, Pb and Zn concentration during the
monsoon period (October–January) compared to the rest of the year was noticed. Factor analysis and correlation among the heavy
metals concluded that Cr, Ni, Cd and Fe are of crustal origin, whereas, Cu, Pb and Zn are from anthropogenic sources. Organic
carbon content in the sediment increased during monsoon period, pointing to the role of land runoff and backwater discharge
in enhancing its content. The study also elucidates the impact of the recent tsunami in depleting metal content in the coastal
sediment as compared to the pre-tsunami period. 相似文献
299.
Spatial distributions of vegetation cover are closely related to topographical characters like slope, steepness, soil types, elevations, etc. In seismo-tectonic regions fault lines or tectonic lineaments are the most prominent surface signatures that can be reflected by vegetation distribution as tectonic displacement causes the change of topographical parameters. In the present study a part of northern Baromura hill (between 23º 42′ N to 23º49 N latitudes and 91º30 E to 91º36 E longitudes), which is considered as an active seismo-tectonic region of Tripura as well as northeast India, was selected for assessing the relationship between spatial variation of plant cover and topography. Geologically, Baromura hill is a north–south extended fold belt and formed by late Tertiary to Quaternary depositions. Evidences show that tectonic events played very important role in landform evolution of this area during the geological past. In this research an extensive fieldwork was conducted in the study area to understand the geomorphic and vegetation signatures and their environmental relationships. Various spectral resolutions of Landsat ETM+ were used for digital analysis. To analyse the vegetation character of this area digital operation was done within the spectral range 0.63–1.75 μm. Band 4 and band 3 were used for NDVI operation. Band 5 or mid-wave infrared band was classified in unsupervised mode to understand the range of plant water in the study area. Overlay operation with those operated images shows the spatial distribution pattern of vegetation cover indicates the landform condition. Three clear tectonic lineaments (faults) were detected from the digital study in on the northern part Baromura hill. Structural conditions of those fault lines were verified by geo-electrical survey during fieldwork. GPS tool was used for fixing the ground control points. Resistivity characters of the study area assessed from VES profile strongly supports that vegetation cover analysis from remotely sensed data within 0.63–1.75 μm spectral ranges can be a very useful tool for detecting surface tectonic signatures of the landform. 相似文献
300.
Shraban Sarkar Archana K. Roy Tapas R. Martha 《International journal of geographical information science》2013,27(12):2436-2454
Soil formation depends upon several factors such as parent material, soil biota, topography and climate. It is difficult to use conventional soil survey methods for mapping the depth of soil in complex mountainous terrains. In this context, the present study aimed to estimate the soil depth for a large area (330.35 km2) using different geo-environmental factors through a soil-landscape regression kriging (RK) model in the Darjeeling Himalayas. RK with seven predictor variables such as elevation, slope, aspect, general curvature, topographic wetness index, distance from the streams and land use, was used to estimate the soil depth. While topographic parameters were derived from an 8-m resolution digital elevation model, the ortho-rectified Cartosat-1 satellite image was used to prepare the land use map. Soil depth measured at 148 sites within the study area was used to calibrate and validate the RK model. The result showed that the RK model with the seven predictors could explain 67% spatial variability of soil depth with a prediction variance between 0.23 and 0.42 m at the test site. In the regression analysis, land use (0.133) and slope (–0.016) were identified as significant determinants of soil depth. The prediction map showed higher soil depth in south-facing slopes and near valleys in comparison to other areas. Mean, mean absolute and root mean-square errors were used to access the reliability of the prediction, which indicated a goodness-of-fit of the RK model. 相似文献