Heavy metal pollution around the island city of Bombay, India. Part I: quantification of heavy metal pollution of aquatic sediments and recognition of environmental discriminants

The island city of Bombay is surrounded by Thane Creek in the east and the Ulhas River to the north. These two aquatic regimes act as receptacles of industrial and sewerage discharges from the city and also lithogenic fluxes from the adjacent basaltic terrain.

Two consecutive sets of pre-monsoon and post-monsoon samples of water, suspended solids and sediments were collected from nineteen stations along the intertidal zone of Thane Creek and from eleven stations along the Ulhas River course. Toxic heavy metals such as Fe, Mn, Ni, Co, Pb, Zn, Cu, Cr, Hg and Cd have been analysed in the samples and the degree of metal contamination has been brought out by comparison with local background as well as global standards. Thane Creek is relatively stagnant and dominated by a marine environment, while the Ulhas River is more dynamic and fluvio-estuarine in nature. The two environmental settings have been recognised in discriminant analysis of the heavy metal data.     

Phase relations in three charnockites from Pallavaram-Tambaram

Chemical data on eight ferromagnesian silicates from a syenitic and two tonalitic charnockites from the type area near Madras show remarkably regular cation fractionation patterns. The distribution coefficients for magnesium-iron point to equilibration under granulite facies metamorphism. Orthopyroxene-garnet-biotite subsystem has been found to be of a near invariant nature, while the compositions of orthopyroxene and biotite in the nongarnetiferous tonalite are different. Analysis of phase equilibrium by Thompson type AFM projection strongly indicates that pressure, temperature and the chemical potential of water were constant for assemblages separated by large distances.     

Hydrochemical framework of the aquifer in and around East Kolkata Wetlands,West Bengal,India

The area lies between Hugli river in the northwest and Bidyadhari river in the east and includes the East Kolkata Wetlands. The East Kolkata Wetlands is included in the List of Wetlands of International Importance (“Ramsar List”), as per the Convention on Wetlands signed in Ramsar, Iran, in 1971. This wetland has been declared as a Ramsar site on the 19th August 2002 (Ramsar site no. 1208) and therefore has acquired an international status. The area is a part of the lower deltaic plain of the Bhagirathi–Ganga river system and is generally flat in nature. The sub-surface geology of the area is completely blanketed by the Quaternary fluviatile sediments comprising a succession of clay, silty clay, sand and sand mixed with occasional gravel. The Quaternary aquifer is sandwiched between two clay sequences. The confined aquifer is made up of moderately well sorted sand and reflects fluviatile environment of deposition. The regional groundwater flow direction is from east to west. Detailed geochemical investigations of 40 groundwater samples along with statistical analysis (for example, correlation and principal component analysis) on these chemical data reveal: (i) four types of groundwater quality, for example, good, poor, very poor and water unsuitable for drinking purpose, (ii) four hydrochemical facies which may be assigned to three broad types such as “fresh”, “blended”, and “brackish” waters, (iii) the evolution of the “blended” water is possibly due to hydraulic mixing of “fresh” and “brackish” waters within the aquifer matrix and/or in well mixing, and (iv) absence of Na–Cl facies indicates continuous flushing of the aquifer.     

Palaeo-path investigation of the lower Ajay River (India) using archaeological evidence and applied remote sensing

Numerous palaeochannels, oxbow lakes and elongated sediment fills in Eastern India, particularly along the lower Ajay River, provide a record of channel shifting during the Late Quaternary. Proper characterization of these features is useful for discussing the dynamic evolution of the river system in the Ajay-Damodar Interfluve region. Remote sensing data, archaeological evidence and sedimentology aid in reconstructing the geomorphic history of the lower Ajay River. Archaeological studies help in calculating the rate and direction of channel migration. The channel migration rate varies from 0.32 to 3.41 m/year in the study area. Bouguer gravity anomalies suggest that the rate of channel migration may be controlled by the density variations of the basement rocks. Furthermore, neotectonics activity played a significant role in the migration of Ajay River towards north-east direction.     

The role of fluid inclusions in mineral exploration—An attempt on the Bihar Mica Belt of India

Fluid inclusions and melt inclusions have been considered as possible guides for mineral exploration by many researchers. However, the minuteness of the fluid inclusions and the multiplicity of generations within the same deposit have always posed serious problems in the proper utilization of fluid-inclusion data in prospecting.Fluid inclusions preserve a valid and comprehensive record of the fluids coexisting with host minerals at the time of crystallization. A careful comparison of fluid-inclusion parameters and deposit characteristics enables one to distinguish between economically significant and insignificant zones of pegmatites.A systematic study of different pegmatites in an area of about 100 km² in the central part of the Bihar Mica Belt, India, was made. Mineralogical, fluid-inclusion, and melt-inclusion data of the principal mineral constituents like quartz, beryl, and apatite were collected. Thirty-three occurrences were chosen for the study. Pegmatites were grouped into economically significant (commercial) and barren (noncommercial) types. The fluid-inclusion parameters used in this study are size, population, presence of liquid carbon dioxide, salinity, and temperature of homogenization.Economically significant pegmatites and barren pegmatites have distinctly different populations of fluid inclusions. Economic pegmatites show a preponderance of highly saline, polyphase fluid inclusions, commonly with liquid carbon dioxide; these fluid inclusions homogenize over a wide range of temperature. Their size ranges from 50 m to 10 m. On the other hand, quartz of barren pegmatites is characterized by the preponderance of vapor-rich biphase inclusions, which homogenize at a relatively narrower but higher range of temperature. Fluid inclusions that contain halite daughter crystals are rare. The average size of the fluid inclusions in barren pegmatites is smaller (5 m to 20 m). Melt inclusions are more abundant in the barren pegmatites.     

Assessment of groundwater potential of Gandhinagar region,Gujarat

With burgeoning population, the groundwater demands of any area increased by many fold and therefore, it is essential to assess the groundwater potential to choose suitable sites for further groundwater development. Present study determines the groundwater potential of different parts of Gandhinagar region located at Gandhinagar district, Gujarat, India. Here, excluding city dwellers, all villagers are mostly dependent on groundwater for drinking and domestic purposes. With increasing population, there is a rise in daily human consumption and hence reduction in groundwater quantity.Various types of industries of Gandhinagar such as textile industries, food processing industries, ceramic industries etc. also require groundwater. Industrial discharges deteriorate the water quality of this region. Therefore, water level monitoring and quality assessment of groundwater in regular intervals is essential. The groundwater potential zoning is an indicator, which gives the overall idea about the groundwater condition. Overlay analysis in GIS using multiple criteria such as WQI, hydraulic conductivity, groundwater velocity, and depth to piezometric surface discloses that there are five groundwater potential zones in Gandhinagar region. This study reveals that majority of the study area is covered with medium potential zone. Different management plans such as treated surface water supply, reduction in tubewell operation time, development of rooftop rainwater harvesting system and artificial recharge system etc. are recommended for different potential zones for sustainable development of groundwater of Gandhinagar region.     

Evaluation of the Effect of Fault on the Stability of Underground Workings of Coal Mine through DEM and Statistical Analysis

The rock mass around an excavation is generally traversed by different geological discontinuities such as faults, folds, slips, joints, etc. Fault is one of the major geological discontinuities which creates lot of difficulties during underground winning of coal. Entire stress regime and ground conditions in the formation are altered in and around the faults. Faults also impose detrimental effects by introducing impurities, including clay and various forms of mineral matter into the coal seams; opening of pathways for the influx of water and gas into the underground workings; displacing the coal seams upward/downwards making the coal seams difficult or sometimes impractical to mine. Appropriate evaluation of the effect of the fault on the stability of the underground workings is a requisite for safe design of the underground mining structures. In this paper, a study has been carried out to assess the effect of the fault on the stability of underground coal mines by numerical simulation with distinct element method (DEM). On the calibrated DEM model, parametric study has been performed by varying the selected parameters, the dip and the friction angles of the fault. The analysis of variance (ANOVA) shows that both the factors have statistically significant effect on the strength of the coal pillar. Similarly, the displacement of the immediate roof and the height of the disturbed strata are evaluated by the DEM modelling and statistical analysis when the fault passes through the middle of the gallery. The results of ANOVA for both cases indicate that the both factors have significant effect on the displacement of the immediate roof and the height of the disturbed strata. It is obtained from the study that the low angle fault causes high instability in the immediate roof. The paper has been supplemented with the field observations where instability in underground roadways of a coal mine in India is caused by the fault. It was observed in VK-7 incline mine of Singareni Collieries Company Limited, India that there was sudden failure of immediate roof of a roadway where a low angle fault crosses the middle of the roadway. The findings of the paper help to understand the behaviour of the coal pillar and the surrounding rock mass in the presence of the fault. The study would also help to take appropriate decisions about the unstable regions of the working safeguarding safety in underground coal mines.     

Bioindicator role of tintinnid (Protozoa: Ciliophora) for water quality monitoring in Kalpakkam,Tamil Nadu,south east coast of India

The feasibility of a potential bioindicator based on functional groups of microzooplankton tintinnids for bioassessments of water quality status was studied during southwest monsoon (June to September) along the coastal waters of Kalpakkam, India during 2012–2015. The work highlights the following features (1) tintinnid community composed of 28 species belonging to 11 genera and 9 families, revealed significant differences among the four study sites (2) maximum numerical abundance (2224 ± 90 ind. l^? 1) and species diversity (H′ = 2.66) of tintinnid were recorded towards Bay of Bengal whereas minimum abundance (720 ± 35 ind. l^? 1) and diversity (H′ = 1.74) were encountered in the backwater sites, (3) multivariate analyses [RELATE, Biota-environment (BIOENV) and canonical analysis of principal coordinates (CAP)] reveal that chl a, nitrate and phosphate were the potential causative factors for tintinnid distribution. Based on the results, we suggest that tintinnids may be used as a potential bioindicator of water quality status in marine ecosystem.