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Thilagavathi R.,Annamalai University | Chidambaram S.,Annamalai University | Prasanna M.V.,Curtin University | Pethaperumal S.,State Groundwater Unit and Soil Conservation
Arabian Journal of Geosciences | Year: 2013

Geophysical logs provide a strong mechanism for interpretation and determination of the depositional environments, facies and also help in interpretations of hydrogeologic units. Spontaneous potential (SP) and resistivity logs can be used as an indicator of textural parameters. Pondicherry region has a complicated geology and with formation of different ages. The boreholes (BH) of this region are examined for litholog, SP and resistivity from four different BH locations, viz, Ariyankuppam, Chinnaverampattinam, Thavalakuppam and Nallavadu. These locations were studied and interpreted by using the shapes of the curves to identify the depositional environments, and this was later compared with the vertical litholog profile. Comparing the variation of these logs, the lateral variation of sedimentary facies was also attempted. The average resistivity values of Ariyankuppam, Chinnaverampattinam, Thavalakuppam and Nallavadu are 42.4, 30.4, 50.4 and 28.3 Ωm, respectively. Majority of the resistivity values corresponds from fine- to medium-grained sand, clayey pebbles, fine to very coarse sand and clayey sand with lignite. Frequency of resistivity values in each BH were identified for determining the dominant representative grain size. The study has pointed out the lithological variation of the system laterally and vertically using geophysical well logs. © 2013 Saudi Society for Geosciences. Source


Thilagavathi R.,Annamalai University | Chidambaram S.,Annamalai University | Thivya C.,Annamalai University | Prasanna M.V.,Curtin University Australia | And 2 more authors.
International Journal of Earth Sciences and Engineering | Year: 2015

Organic carbon concentrations can vary considerably, both spatially and temporally, so a large number of analyses are frequently required to produce a representative estimate of concentrations. Natural organic carbon is mainly derived from decomposing vegetation and other organic matter in the soil zone. In this scenario, a baseline attempt was made to study the behaviour of organic carbon content in groundwater by collecting samples from the layered aquifer sequence of Pondicherry. The samples were collected from Recent Alluvium (30), Upper Cuddalore (13), Lower Cuddalore (13), Other Tertiary formation (7), mixed aquifer (5) and Cretaceous formations (24). The analysis of these samples show that higher concentration of Dissolved Organic Carbon (DOC) was noted in the alluvial formation and the average concentration was higher in Upper Cuddalore Formation. The samples of these formations were compared with pH, Ionic strength, and log pCO2 and bicarbonate concentration. The alluvial aquifer shows that pH governed dissolution along the coastal tracts and in Upper Cuddalore formation it’s based on interaction between aquifer matrix and groundwater. © 2014 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved. Source


Thilagavathi R.,Annamalai University | Chidambaram S.,Annamalai University | Pethaperumal S.,State Groundwater Unit and Soil Conservation | Thivya C.,Annamalai University | And 4 more authors.
Environmental Earth Sciences | Year: 2016

Groundwaters of the coastal region are significant and serve as a fragile ecosystem in the sedimentary terrain. The Pondicherry region is characterized by different geological formations of distinct geological epochs Cretaceous, Tertiary and Quaternary. Ninety-three samples were collected from specific aquifers with respect to spatial distribution [Alluvium (31), Upper Cuddalore (13), Lower Cuddalore (13), Other Tertiary (7), Cretaceous (24) and Mixed—multiple completion aquifer (5)]. The collected samples were analyzed for major ions Ca2+, Mg2+, Na+, K+, HCO3 −, Cl−, PO4 2−, SO4 2−, F and DOC. Stables isotopes of δ18O, δD and δ 13C were also analyzed along with heavy metals like Al, Ba, Fe, Sr, Cd and Zn. The δ18O ranges between −6.85 and −2.15 ‰, and δD ranges between −43.94 and −19.41 ‰. The distribution of these environmental isotopes in groundwater of this layered aquifer sequence was also attempted. A comparison of the isotopic data with the rainfall, Local Meteoric Water Line with a equation of δD = 7.398 * δ18O + 5.067, Indian Meteoric Water Line and Global Meteoric Water Line was performed. The δ13C values for groundwater ranges from −5.3 to −18.1 ‰. The result indicates that the groundwater in the study area is mainly meteoric in origin, and few samples show evidence of evaporation. The dissolved organic carbon (DOC) is a very important component in biogeochemical cycling of elements characterized by high susceptibility to leaching. The range of the DOC in the study area is 0–16 mg/L. Factor analysis was applied to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry. The Alluvium aquifers show a complex hydrogeochemistry than the older aquifers. The major factor influencing the hydrogeochemistry of the region is rock–water interaction and anthropogenic processes. Hence, metal mobility of the groundwater shows the correlation of metal bonding and DOC. The relation between the DOC and heavy metal concentration in the aquifers was also identified. © 2015, Springer-Verlag Berlin Heidelberg. Source


Thilagavathi R.,Annamalai University | Chidambaram S.,Annamalai University | Thivya C.,Annamalai University | Prasanna M.V.,Curtin University Australia | And 3 more authors.
Proceedings of the National Academy of Sciences India Section A - Physical Sciences | Year: 2014

Groundwater is the source for many activities in urban regions and the quality plays a significant role in determination of its usage. In coastal regions the situation becomes more complex due to the interplay of complex chemical processes like natural weathering, anthropogenic activities and sea water intrusion. Hence an attempt has been made in this study to delineate these processes and to identify the regions dominated by them. In this regard, 92 groundwater samples were collected and analysed for major cations and anions. Among the analysed parameters the ratios of the cations like Ca/Mg, (Ca + Mg)*/HCO3:(Na + K)*/HCO3 were used to identify the process of weathering. Moreover, the ternary plots of cations and selected anions were also used to identify the weathering and the anthropogenic processes. HCO3 - and SiO2 in groundwater were used to unravel the nature of weathering, supported by pH and pCO2 observations. HCO3 --derived by the carbonate dissolution and silicate weathering were calculated from the total HCO3 - and it was found that HCO3 - derived from the carbonate rock dissolution is dominant in alluvium, tertiary and cretaceous formations due to the presence of kankar, calcareous sandstone and limestone. The (HCO3 + SiO2)/(Cl + NO3) ratios were used to demarcate the regions of weathering and anthropogenic activities and it was found that the central and north eastern part of the study area is dominated by the anthropogenic activities. © The National Academy of Sciences, India 2014. Source


Thilagavathi R.,Annamalai University | Chidambaram S.,Annamalai University | Thivya C.,Annamalai University | Prasanna M.V.,Curtin University Australia | And 2 more authors.
International Journal of Earth Sciences and Engineering | Year: 2014

Organic carbon concentrations can vary considerably, both spatially and temporally, so a large number of analyses are frequently required to produce a representative estimate of concentrations. Natural organic carbon is mainly derived from decomposing vegetation and other organic matter in the soil zone. In this scenario, a baseline attempt was made to study the behaviour of organic carbon content in groundwater by collecting samples from the layered aquifer sequence of Pondicherry. The samples were collected from Recent Alluvium (30), Upper Cuddalore (13), Lower Cuddalore (13), Other Tertiary formation (7), Mixed aquifer (5) and Cretaceous formations (24). The analysis of these samples show that higher concentration of Dissolved Organic Carbon (DOC) was noted in the Alluvial formation and the average concentration was higher in Upper Cuddalore Formation. The samples of these formations were compared with pH, Ionic strength, and log pCO2 and bicarbonate concentration. The alluvial aquifer shows that pH governed dissolution along the coastal tracts and in Upper Cuddalore formation it’s based on interaction between aquifer matrix and groundwater. © 2014 CAFET-INNOVA TECHNICAL SOCIETY. Source

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