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1.
Hemant Kumar Singh Aswathi Thankappan Poonam Mohite Satish Kumar Sinha Dornadula Chandrasekharam Trupti Chandrasekhar 《Arabian Journal of Geosciences》2018,11(6):137
Tulsishyam thermal springs are located in the Saurashtra region of Gujarat, India with discharge temperatures varying from 39 to 42 °C. The pH of these thermal springs varies from 7.1 to 7.4, indicating neutral character. Though these thermal springs propagate through the near surface layer of Deccan basalt, detailed geochemical analysis of the thermal waters using Piper diagram suggests that the water is interacting with the granitic basement rock. Silica and cation geothermometry estimates have reservoir temperature in the range of 138 to 207 °C categorizing it into a low to moderate enthalpy geothermal system. Furthermore, the area has high heat flow values of 53–90 mW/m2 because of shallow Moho depth. The prevailing conditions suggest that the geothermal energy can potentially be exploited through an enhanced geothermal system (EGS). The study also indicates different mineral phases that may precipitate out of water during exploitation of geothermal energy and it should be taken into account while designing an EGS for the area. 相似文献
2.
Gloria Eneke Takem Dornadula Chandrasekharam Samuel N. Ayonghe P. Thambidurai 《Environmental Earth Sciences》2010,61(2):287-298
Alluvial groundwater from springs and bore wells, used as the major source of water for drinking and other domestic purposes
in the semi-urban informal settlements of Douala, Cameroon, has been studied. Six representative springs, four bore wells
and two hand dug wells, situated in the Phanerozoic basin were selected, from which a total of 72 water samples were analyzed
for chemical characteristics and indicators of bacterial contamination. The results showed anthropogenic pollution, evident
from high concentrations of organic (up to 94.3 mg NO3/l nitrate) fecal coliform and fecal streptococcus detected in the springs and bore wells (with values of 2,311 and 1,500 cfu/100 ml,
respectively). The pH ranged from 3.4–6.5, which is lower than the guidelines for drinking water. Groundwater samples from
background upstream inland natural areas W1 and W2 had low electrical conductivity (54.2 and 74.8 μs/cm, respectively) and
major ions, which increased downstream in the valleys, peaking in the more densely settled areas. An acceptable concentration
of solutes was observed for the bore wells except for a single sample from B4. The bore-well sample B4 registered the highest
microbial content (2,130 cfu/100 ml) and nitrate level(26 mg/l), which could be due to the bottom of this well lying just
at or close to the zone of mixing between sewage and groundwater. The absence of a direct correlation between nitrate and
fecal matter suggests multiple sources of contamination. The shallow alluvial aquifer consists of unconsolidated deposits
of gravel, sand, silt and clay. The springs, therefore, receive direct recharge from the ground surface with limited contaminant
attenuation, which leads to water quality deterioration, especially during the rainy season. This shows the urgent need to
put basic service infrastructures in place. The local population should be sensitized to the importance of chlorinating and
boiling drinking water to prevent health hazards. 相似文献
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4.
A. Minissale D. Chandrasekharam O. Vaselli G. Magro F. Tassi G. L. Pansini A. Bhramhabut 《Journal of Volcanology and Geothermal Research》2003,127(1-2):19-32
Most thermal spring discharges of Rajasthan and Gujarat in northwestern India have been sampled and analysed for major and trace elements in both the liquid and associated gas phase, and for 18O/16O, D/H (in water), 3He/4He and 13C/12C in CO2 (in gas) isotopic ratios. Most thermal springs in Rajasthan are tightly associated to the several regional NE–SW strike-slip faults bordering NE–SW ridges formed by Archaean rocks at the contact with Quaternary alluvial and aeolian sedimentary deposits of the Rajasthan desert. Their Ca–HCO3 immature character and isotopic composition reveals: (1) meteoric origin, (2) relatively shallow circulation inside the crystalline Archaean formations, (3) very fast rise along faults, and (4) deep storage temperatures of the same order of magnitude as discharging temperatures (50–90°C). Thermal spring discharges in Gujarat are spread over a larger area than in Rajasthan and are associated both with the NNW–SSE fault systems bordering the Cambay basin and the ENE–WSW strike-slip fault systems in the Saurashtra province, west of the Cambay basin. Chemical and isotopic compositions of springs in both areas suggest a meteoric origin of deep thermal waters. They mix with fresh or fossil seawater entering the thermal paths of the spring systems through both the fault systems bordering the Cambay basin, as well as faults and fractures occurring inside the permeable Deccan Basalt Trap in the Saurashtra province. The associated gas phase, at all sampled sites, shows similar features: (1) it is dominated by the presence of atmospheric components (N2 and Ar), (2) it has high crustal 4He enrichment, (3) it shows crustal 3He/4He signature, (4) it has low CO2 concentration, and (5) the only analysed sample for 13C/12C isotopic ratio in CO2 suggests that CO2 has a strong, isotopically light organic imprint. All these features and chemical geothermometer estimates of spring waters suggest that any active deep hydrothermal system at the base of the Cambay basin (about 2000–3000 m) has low-to-medium enthalpy characteristics, with maximum deep temperature in the storage zone of about 150°C. In a regional overview, both thermal emergences of Rajasthan and Gujarat could be controlled by the counter-clockwise rotation of India. 相似文献
5.
Determination of the Concentration of Carbonic Species in Natural Waters: Results from a World‐Wide Proficiency Test 下载免费PDF全文
Mahendra P. Verma Enrique Portugal Sophie Gangloff María Aurora Armienta Dornadula Chandrasekharam Mayela Sanchez Roberto E. Renderos Miguel Juanco Robert van Geldern 《Geostandards and Geoanalytical Research》2015,39(2):233-255
The results of an international interlaboratory proficiency test for the determination of carbonic species are presented. Eight laboratories analysed twelve water samples (four synthetic waters, one lake water, four geothermal waters, one seawater and two petroleum waters) by two methods: (a) individual laboratory analytical procedure and (b) acid–base titration curves in tabular form following a standardised protocol. In case (b), the concentrations of carbonic species were calculated by the organiser using the (1) Hydrologists' method, (2) Geochemists' method and/or (3) initial pH and total alkalinity method. For synthetic waters, the averaged % trueness and precision of measurement of the two methods were (trueness = 7.6, precision = 9.4) and (9.0, 3.4) for total alkalinity, and (6.6, 31.0) and (7.8, 6.1) for carbonic alkalinity, respectively. This indicates that the total alkalinity calculation procedure is in general correct in the individual laboratory method, but the carbonic alkalinity calculation procedure has serious problems. The measurements of total alkalinity for lake and seawaters were in agreement in both the methods; however, the individual laboratory measurement method for geothermal and petroleum waters was conceptually incorrect. Thus, the analytical procedures for the determination of carbonic species were reviewed. To apply the Hydrologists' and/or Geochemists' methods, the location of NaHCO3EP and H2CO3EP is necessary, even for samples with pH lower than that of NaHCO3EP, and a backward titration curve after complete removal of CO2 must be performed. The initial pH and total alkalinity method is appropriate where a complete analysis of species that contribute to the alkalinity is known. 相似文献
6.
Syed Hilal Farooq Pintu Prusty Raj Kumar Singh Subhajit Sen Dornadula Chandrasekharam 《Arabian Journal of Geosciences》2018,11(22):709
The contamination of aquifers by fluoride and arsenic is a major cause of concern in several parts of India. A study has thus been conducted to evaluate the extent and severity of fluoride contamination and also its seasonal variability. Two blocks (Purulia-1 and Purulia-2) were considered for this purpose. Twenty groundwater samples (in each season) were collected from tube wells during the pre-monsoon and post-monsoon seasons. In addition to fluoride, groundwater samples were also analyzed for major cations, anions, and other trace elements. The concentration of fluoride shows significant seasonal variation and ranges between 0.94–2.52 and 0.25–1.43 mg/l during the pre-monsoon and post-monsoon seasons, respectively. In pre-monsoon season, more than 40% of the water samples show fluoride concentrations higher than the WHO limit. However, during the post-monsoon season, none of the groundwater sample shows fluoride concentrations higher than the WHO limit. Lesser concentration during the post-monsoon season is attributed to the dilution effect by the percolating rainwater, which has also been reflected in the form of a decrease in concentrations of other elements. The petrographic studies of the rock samples collected from the study area show that the rocks are mainly composed of plagioclase, orthoclase, and quartz with abundant biotite. The weathering and dissolution of biotite plays an important role in controlling the fluoride concentrations in the groundwater of the study area. 相似文献
7.
S.H. Farooq D. Chandrasekharam G. Abbt-Braun Z. Berner S. Norra D. Stüben 《Applied Geochemistry》2012
Dissolved organic C (DOC) plays an important role in the mobilization of As from sediments. In West Bengal, the widely used technique for obtaining jute fiber involves retting of the jute plant in ponds (hereafter such ponds are termed jute decomposing ponds) for several weeks, which produces significant amounts of DOC in the ponds. These ponds thus act as point sources of DOC and supply huge quantities of organic C to the Bengal Delta sediments. This study has been carried out to investigate the role of such DOC in enriching the groundwater with As in the Bengal Delta. Data clearly show that due to the effect of DOC, As is mobilized from the upper 2.6 m of the sediment profile, and is fixed between 2.6 and 6.1 m, while the lower part (6.1–9 m) largely remains unaffected. The reducing conditions mainly developed due to the decay of the percolating DOC seem to help the mobilization and transportation of As and other redox sensitive elements (Fe, Mn), as well as elements (Cu, Zn) attached to oxy-hydroxides of those redox-sensitive elements. Experiments also indicate that if the DOC production at the surface continues for a longer period of time, the zone of As fixation (2.6–6.1 m) may get shifted further downwards and ultimately intercept the water table resulting in As enrichment of groundwater. 相似文献
8.
Temporal variations in arsenic concentration in the groundwater of Murshidabad District,West Bengal,India 总被引:1,自引:0,他引:1
S. H. Farooq D. Chandrasekharam S. Norra Z. Berner E. Eiche P. Thambidurai D. Stüben 《Environmental Earth Sciences》2011,62(2):223-232
Systematic investigations on seasonal variations in arsenic (As) concentrations in groundwater in both space and time are
scarce for most parts of West Bengal (India). Hence, this study has been undertaken to investigate the extent of As pollution
and its temporal variability in parts of Murshidabad district (West Bengal, India). Water samples from 35 wells were collected
during pre-monsoon, monsoon and post-monsoon seasons and analyzed for various elements. Based on the Indian permissible limit
for As (50 μg/L) in the drinking water, water samples were classified into contaminated and uncontaminated category. 18 wells
were reported as uncontaminated (on average 12 μg/L As) and 12 wells were found contaminated (129 μg/L As) throughout the
year, while 5 wells could be classified as either contaminated or uncontaminated depending on when they were sampled. Although
the number of wells that alternate between the contaminated and uncontaminated classification is relatively small (14%), distinct
seasonal variation in As concentrations occur in all wells. This suggests that investigations conducted within the study area
for the purpose of assessing the health risk posed by As in groundwater should not rely on a single round of water samples.
In comparison to other areas, As is mainly released to the groundwater due to reductive dissolution of Fe-oxyhydroxides, a
process, which is probably enhanced by anthropogenic input of organic carbon. The seasonal variation in As concentrations
appear to be caused mainly by dilution effects during monsoon and post-monsoon. The relatively high concentrations of Mn (mean
0.9 mg/L), well above the WHO limit (0.4 mg/L), also cause great concern and necessitate further investigations. 相似文献
9.
Banerjee, D. [2009. Thermoluminescence and optically stimulated luminescence signals from volcanic ash: History of volcanism in Barren Island, Andaman Sea, Quaternary Geochronology, doi:10.1016/j.quageo.2009.01.011] aimed at determining the history of volcanism and evolution of Barren Island by dating a single ash sample using thermoluminescence and optically stimulated luminescence signals. An attempt to date the volcanic episodes and decipher the history of the volcano with just one sample, the stratigraphic position of which is not known (or at least specified in the paper), does not make any sense, at least in the context of history of volcanism on Barren Island. The title of the paper is a misnomer, as it does not in fact address the reconstruction of the history of volcanism on the Barren Island, but discusses the methods and problem of age underestimation using this technique instead. 相似文献
10.
Pooja?V.?Kshirsagar Hetu?C.?ShethEmail author Sheila?J.?Seaman Badrealam?Shaikh Poonam?Mohite Trupti?Gurav D.?Chandrasekharam 《Bulletin of Volcanology》2012,74(2):559-577
Spherulites and thundereggs are rounded, typically spherical, polycrystalline objects found in glassy silicic rocks. Spherulites
are dominantly made up of radiating microscopic fibers of alkali feldspar and a silica mineral (commonly quartz). They form
due to heterogeneous nucleation in highly supercooled rhyolitic melts or by devitrification of glass. Associated features
are lithophysae (“stone bubbles”), which have an exterior (sometimes concentric shells) of fine quartz and feldspar, and internal
cavities left by escaping gas; when filled by secondary silica, these are termed thundereggs. Here, we describe four distinct
occurrences of spherulites and thundereggs, in pitchstones (mostly rhyolitic, some trachytic) of the Deccan Traps, India.
The thundereggs at one locality were previously misidentified as rhyolitic lava bombs and products of pyroclastic extrusive
activity. We have characterized the thundereggs petrographically and geochemically and have determined low contents of magmatic
water (0.21–0.38 wt.%) in them using Fourier transform infrared spectroscopy. We consider that the spherulite-bearing outcrops
at one of the localities are of lava flows, but the other three represent subvolcanic intrusions. Based on the structural
disposition of the Deccan sheet intrusions studied here and considerations of regional geology, we suggest that they are cone
sheets emplaced from a plutonic center now submerged beneath the Arabian Sea. 相似文献