K. Srinivasamoorthy

Hydrochemistry of groundwater in a coastal region of Cuddalore district, Tamilnadu, India: implication for quality assessment

A hydrogeochemical investigation was conducted in a coastal region of Cuddalore district to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. The geology of the study area comprises of sandstone, clay, alluvium, and laterite soils of Tertiary and Quaternary age. A total of 18 groundwater samples were analyzed for 14 different water quality parameters and the result indicates higher concentrations of ions like Cl (3,509xa0mg/l), Na (3,123xa0mg/l), and HCO3 (998xa0mg/l) when compared with WHO, BIS, and ISI standards. A positive correlation (r2u2009=u20090.82) was observed between Na and Cl, indicating its sources from salt water intrusion. Three factors were extracted with a total variance of 64% which indicates the sources of salinization, cation exchange, and anthropogenic impact to the groundwater. The Piper trilinear diagram indicates both Na–Cl and mixed Na–HCO3–Cl-type, indicating that groundwater was strongly affected by anthropogenic activities. The plot of (Cau2009+u2009Mg)/(Ku2009+u2009Na) indicates evidences of cation exchange and salt water intrusion. The (Ca–0.33*HCO3)/ SO4 plot indicates salt water intrusion for elevated SO4 levels rather than gypsum dissolution. The spatial distribution of total dissolved solid indicates the saline water encroachment along the SW part of the study area. As per sodium adsorption ratio (SAR), 50% of the samples with <10 SAR are suitable for irrigation and >10 SAR indicates that water is unsuitable for irrigation purposes. The residual sodium carbonate classification indicates that 50% of the samples fall in safe and 50% of the samples fall in bad zones and prolonged usage of this water will affect the crop yield. The Chloro Alkaline Index of water indicates disequilibrium due to a higher ratio of Clu2009>u2009Na–K, indicating the influence of salt water intrusion. The Permeability Index of the groundwater indicates that the groundwater from the study area is moderate to good for irrigation purposes.

Identification of groundwater contamination zones and its sources by using multivariate statistical approach in Thirumanimuthar sub-basin, Tamil Nadu, India

Hydrogeochemical studies have been made in the study area by using multivariate statistical analysis, which is mainly helpful for interpretation of complex data matrices to better understand the geochemical evolution of the area and it allows identifying the possible factors/sources that influence water systems. The spatial distribution of electrical conductivity reveals that an untreated industrial effluents, landfill and anthropogenic activities affecting their groundwater quality in its vicinity and the surrounding area. The dominance of ions was in the order of Na+xa0>xa0Ca2+xa0>xa0Mg2+xa0>xa0K+xa0=xa0Cl−xa0>xa0HCO3−xa0>xa0SO42−xa0>xa0NO3− and Ca2+xa0>xa0Mg2+xa0>xa0Na+xa0>xa0K+xa0=xa0HCO3−xa0>xa0Cl−xa0>xa0NO3−xa0>xa0SO42− during pre monsoon (PRM) and post monsoon (POM), respectively. The statistical results reveals that the groundwater chemistry gets altered by silicate weathering, ion exchange, leaching, anthropogenic input from agricultural return flow and longer distance of migrating groundwater. The hydrogeochemical regimes are distributed along the upstream side, northwestern, western and eastern parts of the study area. The study highlights the descriptive capabilities of conventional and multivariate techniques as effective tools in groundwater evaluation.

Major ion chemistry and identification of hydrogeochemical processes controlling groundwater in and around Neyveli Lignite Mines, Tamil Nadu, South India

Groundwater geochemistry was studied in and around the Neyveli lignite mining region of Tamil Nadu, India. Representative groundwater samples (168) were collected from bore wells during June 2004, October 2004, January 2005, and March 2005 to broadly cover seasonal variation. Higher electrical conductivity values were observed in the southeastern and southwestern part of the study area. During the southwest monsoon (June) and postmonsoon (January) seasons, bicarbonateu2009+u2009chloride dominated the anions, with few representations for sulphate. Sodiumu2009+u2009potassium were the dominant cations in all the seasons except in summer (March). The data reveals that the region is a complex hydrogeochemical system with proportional interplay of ions from leaching of ions, ion exchange, agricultural return flow, and stagnant waters. The influence of mine waters and weathering of minerals varies according to the season and spatial distribution of the sources. The water quality can be used for drinking and irrigation, except in a few locations.

Modeling saline water intrusion in Nagapattinam coastal aquifers, Tamilnadu, India

Unexpected mistreatment of groundwater from coastal aquifers may possibly cause salt water intrusion in coastal aquifers. Coastal areas are mostly overpopulated with productive agricultural lands and expanded irrigated farming actions. Field and modeling studies were started to consider the special effects of possible seawater intrusion into the coastal aquifers. Groundwater levels were measured at 61 locations in Nagapattinam and Karaikal coastal region, identified flow direction pointing toward the coast with no major change in groundwater table. Groundwater samples were collected and analyzed for major ionic parameters, represented higher concentration of conductivity, total dissolved solids, sodium and chloride along the coastal parts of the study area. A computer package for the simulation of dimensional variable density groundwater flow, SEAWAT, has been used to model the seawater intrusion in the coastal aquifers of the study area. The model was stimulated to predict the amount of seawater incursion in the study area for a period of 50xa0years. The simulation results signify saline water intrusion mainly due to up coning of saline water owing to over drafting of groundwater.

A Study on Assessment of Credible Sources of Heavy Metal Pollution Vulnerability in Groundwater of Thoothukudi Districts, Tamilnadu, India

The study investigates the Heavy Metal Pollution vulnerability of the groundwater in the coastal aquifers of Thoothukudi District, Tamilnadu, India. A total of 80 groundwater samples were collected throughout the entire district. Integrated approach includes pollution evaluation indices, principal component analysis (PCA), and correlation matrix (CM) to evaluate the intensity and source of pollution in groundwater. The average abundance order of heavy metal contents in groundwater samples are: Crxa0>xa0Cuxa0>xa0Pbxa0>xa0Fexa0>xa0Znxa0>xa0Nixa0>xa0Mnxa0>xa0Cd. These values were calculated for heavy metal pollution index (HPI), heavy metal evaluation index (HEI), and degree of contamination (Cd). Spatial distribution map of HPI, HEI, Cd indicates that higher indices are observed in the north eastern part of Industrial area (SIPCOT). The Factor score maps suggest that the activities of industries and landfill leachate are pervasive processes. Correlation matrix of heavy metal elements clearly indicates that the groundwater has assimilated with various contaminants from the processes of chemical industries, landfill leachate, and municipal sewage systems in the study area. This study has provided the evidence of effluents discharged from the tannery and auxiliary industries and landfill leachate are the main sources of heavy metal pollution in the groundwater. The current distribution level of heavy metal in the groundwater is of environmental and health concerns and requires attention.

Hydrogeochemical Modelling for Groundwater in Neyveli Aquifer, Tamil Nadu, India, Using PHREEQC: A Case Study

Sophisticated geochemical models have been used to describe and predict the chemical behaviour of complex natural waters and also to protect the groundwater resources from future contamination. One such model is used to study the hydrogeochemical complexity in a mine area. Extraction of groundwater from the coastal aquifer has been in progress for decades to mine lignite in Neyveli. This extraction has developed a cone of depression around the mine site. This cone of depression is well established by the geochemical nature of groundwater in the region. 42 groundwater samples were collected in a definite pattern and they were analysed for major cations, anions and trace elements. The saturation index (SI) of the groundwater for carbonate, sulphate and silica minerals was studied and it has been correlated with the recharge and the discharge regions. The SI of alumino silicates has been used to decipher the stage of weathering. The SIGibbsitexa0−xa0SIK-feldspar has been spatially distributed and the regions of discharge and recharge were identified. Then two flow paths A1 and A2 were identified and inverse modelling using PHREEQC were carried out to delineate the geochemical process that has taken place from recharge to discharge. The initial and final solutions in both the flow paths were correlated with the thermodynamic silicate stability diagrams of groundwater and it was found that the state of thermodynamic stability of the end solutions along the flow path were approaching similar states of equilibrium at the discharge.

Geochemical evolution of groundwater along flow path in Upper Vellar sub basin, Tamilnadu, India: an integrated approach using hydrochemistry, modeling and statistical techniques

Hydrochemical, multivariate statistical, geochemical inverse and flow modeling techniques were attempted to examine groundwater recharge, flow and hydro chemical evolution along groundwater flow path in upper vellar hard rock aquifers. A total of 74 groundwater samples were collected and analyzed for different chemical constituents. Results revealed that three types of water facies were isolated as young, intermediate and matured type. Both hydrochemical and multivariate statistical analyses indicate groundwater in higher elevation observed with lower ionic ratios, plain and low lying areas with medium and higher ionic ratios respectively. Inverse geochemical modeling signify silicate minerals as precipitating and gypsum anhydride and NaCl species tend to dissolve due to limited availability of ions. Hydrochemical alteration seems to be influenced by rock water interaction, ion exchange and anthropogenic processes. .

Geophysical investigations for groundwater in a hard rock terrain, Salem district, Tamil Nadu, India

The main aim of a geophysical investigation in a hard rock region is to solve different hydrogeological problems like depth of water table, basement rock, thickness of weathered zone/formation, structural and stratigraphic conditions relevant to groundwater conditions, and permeability of aquifers. A total of 54 vertical electrode soundings were carried out by Schlumberger electrode arrangement to signify complete lithology of the study area and interpretation was carried out by using curve matching techniques. From the study, 65xa0% of area is dominated by ‘A’ type curve indicating increasing resistivity with depth and 17xa0% by ‘K’ type representing a high-resistivity layer sandwiched between two low-resistivity layers. Four layer cases were also noted in 12xa0% of the study area indicating gradation between the weathered and fractured layers as a semi-weathered zone. Greater thickness has been identified in the weathered zone at the contact of peninsular gneiss and charnockite regions. The maximum, minimum, mean, and arithmetic mean were plotted and identified higher background resistivity values in charnockite. The overlay of maximum and minimum curves for different layers signifies variation of weathering intensity with depth or the presence of weaker zones. In general, lithology plays a significant control over weathering of rocks and groundwater potential.

Assessment of hydrogeochemical status of groundwater in a coastal region of Southeast coast of India

A study was conducted in a coastal region of Cuddalore district of Tamil Nadu, India, to identify the hydrogeochemical processes controlling the groundwater chemistry. The major geological units of the study area are sandstone, clay, alluvium, and laterite soils of Tertiary and Quaternary age. A total of 64 groundwater samples were measured for major ions and stable isotopes. Higher electrical conductivity values indicate the poor quality groundwater along the coastal region. Saline water intrusion mainly affects the hydrochemical composition of the aquifer water reflected by Na–Cl-type waters. Cl−/(Cl−xa0+xa0HCO3−) ratio also indicates the mixing of fresh groundwater with saline water. The results of δD and δ18O analyses show that isotopic compositions of groundwater ranges from −xa07.7 to −xa02.1‰ for δ18O and from −xa055.6 to −xa018.5‰ for δD. Correlation and factor analysis were carried out to find the association of ions and to determine the major factors controlling the groundwater chemistry of the region. The study indicates that ion exchange, weathering, salt water intrusion along the coast, and anthropogenic impacts are the major controlling factors for the groundwater chemistry of the region.

Measurement of submarine groundwater discharge using diverse methods in Coleroon Estuary, Tamil Nadu, India

Submarine groundwater discharge (SGD) is described as submarine inflow of fresh and brackish groundwater from land into the sea. The release of sewages from point and non-point source pollutants from industries, agricultural and domestic activities gets discharged through groundwater to ocean creating natural disparity like decreasing flora fauna and phytoplankton blooms. Hence, to quantify fluxes of SGD in coastal regions is important. Quantification of SGD was attempted in Coleroon estuary, India, using three dissimilar methods like water budget, Darcy law and manual seepage meter. Three seepage meters were installed at two prominent litho units (alluvium and fluvio marine) at a distance of (0–14.7xa0km) away from Bay of Bengal. The water budget and Darcy law-quantified submarine seepage at a rate of 6.9xa0×xa0106 and 3.2xa0×xa0103 to 308.3xa0×xa0103xa0m3xa0year−1, respectively, and the seepage meter quantified seepage rate of 0.7024xa0mxa0h−1 at an average. Larger seepage variations were isolated from three different techniques and the seepage rates were found to be influenced by hydrogeological characteristics of the litho units and distance from the coast.