N. S. Magesh

Hydrogeochemical study of shallow carbonate aquifers, Rameswaram Island, India.

Groundwater quality assessment has been carried out based on physicochemical parameters (pH, EC, TDS, CO3, HCO3, Cl, SO4, PO4, NO2, Ca+2, Mg+2, Na+ and K+) and metal concentration in the Rameswaram Island from 25 bore wells. The Langelier Saturation Index of the groundwater shows positive values (63% samples) with a tendency to deposit the CaCO3 in the majority of water samples. Scatter plot (Ca + Mg/HCO3) suggests carbonate weathering process, which is the main contributor of Ca2+, Mg2+ and HCO3 ions to the water. Gibbs diagram suggests rock–water interaction dominance and evaporation dominance which are responsible for the change in the quality of water in the study area. NaCl and mixed CaNaHCO3 facies are two main hydrogeochemical facies of groundwater. Mathematical calculations and graphical plots of geochemical data reveal that the groundwater of Rameswaram Island is influenced by natural weathering of rocks, anthropogenic activities and seawater intrusion due to over exploitation. Weathering and dissolution of carbonate and gypsum minerals also control the concentration of major ions (Ca+2, Mg+2, Na+ and K+) in the groundwater. The nutrient concentration of groundwater is controlled to a large extent by the fertilizers used in agricultural lands and aquaforms. Comparison of geochemical data shows that majority of the groundwater samples are suitable for drinking water and irrigation purposes.

Trace element contamination in the estuarine sediments along Tuticorin coast--Gulf of Mannar, southeast coast of India.

Sediment samples were collected from Kallar, Korampallam creek and Punnakayal estuaries of Tuticorin coast for assessing the level of contamination by trace elements in these estuarine sediments. The trace element concentration, calcium carbonate, organic carbon and mercury level were analyzed by Inductively Coupled Plasma Atomic Emission Spectrophotometer, Titrimetric method and SnCl2 reduction method. The results reveals that the enrichment factor, metal pollution index and geo-accumulation index of these estuarine sediments were predominantly polluted by Cd, As, Zn, Hg and Pb. The factor analysis revealed the source of trace element accumulation in the estuarine sediments particularly Mn and Fe are from riverine inputs and As and Hg from untreated industrial effluents. Among the selected estuaries, Korampallam creek was found to be highly contaminated by trace elements due to the discharge of effluents from thermal power plant, Tuticorin alkali chemicals, copper smelting, Petrochemical industries and shipping activities.

Hydro-geochemistry and application of water quality index (WQI) for groundwater quality assessment, Anna Nagar, part of Chennai City, Tamil Nadu, India

In the present study, the geochemical characteristics of groundwater and drinking water quality has been studied. 24 groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, carbonate, bicarbonate, chloride, sulphate, nitrate, calcium, magnesium, sodium, potassium and total hardness. The results were evaluated and compared with WHO and BIS water quality standards. The studied results reveal that the groundwater is fresh to brackish and moderately high to hard in nature. Na and Cl are dominant ions among cations and anions. Chloride, calcium and magnesium ions are within the allowable limit except few samples. According to Gibbs diagram, the predominant samples fall in the rock–water interaction dominance and evaporation dominance field. The piper trilinear diagram shows that groundwater samples are Na–Cl and mixed CaMgCl type. Based on the WQI results majority of the samples are falling under excellent to good category and suitable for drinking water purposes.

Groundwater quality assessment using WQI and GIS techniques, Dindigul district, Tamil Nadu, India

The quality of groundwater was assessed by determining the physicochemical parameters (pH, EC, TDS and TH) and major ions concentration (HCO3, Cl, FSO4, Ca, Mg, Na and K) around Dindigul district, Tamil Nadu, India. The groundwater samples were collected from 59 bore wells covering the entire study area and analyzed using standard methods. The GIS mapping technique were adopted to highlight the spatial distribution pattern of physicochemical parameters and major ion concentration in the groundwater. Gibbs diagram reveals that the source of major ions is predominantly derived from rock–water interaction and evaporation dominance process. The salt combinations of the aquifers are dominated by CaHCO3, mixed CaMgCl, mixed CaMgHCO3 and CaCl facies type due to leaching and dissolution process of weathered rocks. The Canadian Council of Ministers of Environment Water Quality Index (CCMEWQI) suggests that most of the groundwater quality falls under good to marginal category. The statistical analysis indicates that the presence of major ions and physicochemical parameters are chiefly controlled by rock–water interaction and residence time of the groundwater. However, the major nutrient like nitrite in the groundwater probably comes from anthropogenic process. Based on the groundwater quality standards, majority of the samples are suitable for drinking purposes except few in the study area.

Evaluation of spatial variations in groundwater quality by WQI and GIS technique: a case study of Virudunagar District, Tamil Nadu, India

Groundwater plays a major life support to mankind. It is the major source to meet the domestic, irrigation and industrial water demands. The depletion of groundwater through excessive consumption and less recharge in the study area has detoriated the quality of groundwater. The present study has analyzed the pre- and post-monsoon physicochemical data of groundwater samples from 49 different bore wells in Virudunagar district. Spatial distribution maps were prepared for various physicochemical parameters using geographic information system. These maps are further classified according to highest desirable, maximum permissible and not permissible prescribed by the World Health Organization. Furthermore, a water quality index (WQI) map was also generated to understand the groundwater quality in the study area. It was observed that the groundwater in the area is hard and alkaline in nature and the WQI reveals that most part of the study area fall under fair water quality class. Also, the effect of recharge during monsoon period has diluted the geochemistry of the groundwater. The application of GIS and WQI in the study area is a promising tool to understand the spatial pattern of groundwater quality and its management.

Deciphering of groundwater potential zones in Tuticorin, Tamil Nadu, using remote sensing and GIS techniques

The present study was carried out to decipher the groundwater potential zones in the coastal terrain of Tuticorin using Indian remote sensing satellite IRS-1C, LlSS-III data on a 1:50,000 scale and Survey of India (SOI) toposheets. The thematic layers such as lithology, slope, land-use, lineament, drainage, soil and rainfall were generated and integrated to prepare the groundwater prospect and recharge map of the study area. These layers were transformed to raster data using feature to raster converter tool in Arc GIS 9.2 software. Subjective weights are assigned to the respective thematic layers and overlaid in GIS platform for the identification of potential groundwater zones within the area. These potential zones were categorized as ‘high’, ‘moderate’, and ‘low’ zones with respect to the assigned weightage of different thematic layers. The resultant map shows that 10% of the area has highest recharge potentials, this is due to the percolation of precipitated water into the sub-surface rocks, followed by 65% of the area with moderate groundwater recharge potentiality, and rest of the area has low recharge potential. The study highlights that the total average annual precipitated water (877 mm) is responsible for natural recharge of the aquifers in the Tuticorin area.

Trace element concentration in surface sediments of Palk Strait, southeast coast of Tamil Nadu, India

The present work was carried to decipher the trace element accumulation in surface sediments of Palk Strait, southeast coast of Tamil Nadu, India. The elemental concentration and correlation results suggest that fine fractions with CaCO3 content followed by organic matter (OM) of the surface sediments control the trace element accumulation in the study area. In addition, Fe and Mn concentration is chiefly contributed from riverine process and controlled by the mangrove ecosystem. The other elements are derived into marine environment through confluence of untreated industrial pollutants into the river system. The EF result shows that the studied marine sediments are enriched by Ni, Mn, Cu, Pb, Cd, Cr, followed by Zn. The order of the pollution intensity with respect to geo-accumulation index suggests the following ascending order: Ni>Mn>Fe>Cu>Pb>Cd>Cr>Zn. Pollution Load Index (PLI) values reveal that all the samples are falling under moderately to unpolluted category.

Assessment of trace element accumulation in surface sediments off Chennai coast after a major flood event

The present study was conducted to assess the trace element concentration in marine surface sediments after major flood event of Chennai metropolis, India. Thirty surface samples were collected from off Chennai coast. Trace elements, organic matter, CaCO3, sand-silt-clay and C/N ratios were studied to understand the accumulation dynamics on sediments. The elemental concentration, calcium carbonate and OM distribution suggest that they are derived from urban runoff and transported through Adyar and Cooum Rivers. The enrichment factor reveals that the sediments are enriched by Pb, Cu, Zn, Cr, Co, Ni followed by Fe. The observed Igeo value shows that the samples are contaminated by Pb, Cu and Zn. The elemental concentration of the surface sediments is low when compared to other coastal region except Pb. The elevated level of Pb in the surface sediments is probably due to migration of contaminated urban soil from industrial and transportation sectors into marine environment.

Spatial risk assessment and trace element concentration in reef associated sediments of Van Island, southern part of the Gulf of Mannar, India.

Forty eight surface sediment samples were collected from the vicinity of Van Island in order to assess the sediment pollution level and potential ecological risk on coral reef ecosystem. The analytical and correlation results indicate a distribution of elements is chiefly controlled by the CaCO3 and OM. The enrichment factor and geoaccumulation index show the elevated level of Pb in the surface sediments is due to application of lead petrol and coal incinerating power plants. The sediment pollution index reveals that majority of the sediments falling under highly polluted sediment category (35.4%) followed by moderately polluted (25%) and dangerous sediment category (14.58%). The potential ecological risk suggests that nearly 66.6% of the samples falling under the low risk category, moderate risk category (20.8%) followed by considerable risk category (8.33%) and very high risk category (4.1%). The accumulation level of trace elements clearly suggests that the coral reef ecosystem is under low risk.

Metal concentrations in the growth bands of Porites sp.: A baseline record on the history of marine pollution in the Gulf of Mannar, India.

The present study was carried out on the Porites coral growth bands (1979 to 2014) to measure the metal accumulation for assessing the environmental pollution status. The concentrations of studied metals are compared with similar global studies, which indicate that the metals are probably derived from natural sources. The identical peaks of Fe and Mn are perfectly matched with Cu, Cr and Ni concentrations. However, the metal profile trend is slightly depressed from a regular trend in Zn, Cd and Pb peaks. The metal accumulation affinity of the reef skeleton is ranked in the following order Cr>Cd>Pb>Fe>Mn>Cu>Ni>Zn. The distribution of metal constituents in coral growth bands is primarily controlled by Fe and Mn in the reef skeleton. Other reef associated metals such as Pb and Cd are derived from other sources like coastal developments and anthropogenic sources.