Electrical resistivity and hydrochemical indicators distinguishing chemical characteristics of subsurface pollution at Cuddalore coast,Tamil Nadu

Electrical resistivity methods are applied extensively for shallow sub-surface objectives but it has constraints in distinguishing the chemical characteristics of the medium. However, this complexity can be resolved by integrated investigations where geophysical anomaly would be validated with hydro-geochemical data. The present study highlights the notable importance of integrated geophysical and hydrogeological investigations in demarcating sub-surface pollution due to saline water intrusion and industrial effluents at Cuddalore coast in India. Geophysical scanning encompassing a total of 35 vertical electrical sounding (VES) were validated with drilling lithologs, water level and water quality parameters from a network of 125 observation wells at a test site of 17 km². To understand the spatial variation of sub-surface contamination, two profiles of apparent resistivity sections were generated covering VES points parallel to the coast. Results revealed that, the low order of resistivity range 3 to 10 Ω-m (up to 30–40 m depth) and total dissolved solids range 2000 to 10,000 mg/l of groundwater reflects sub-surface contamination but cannot distinguish kind of salinity which is further verified by chemical analysis of Ca²⁺ (1200–2041 mg/l), SO₄ ^2? (3000–9480 mg/l) which confirms the gypsum pollution and Na⁺ (750–1000 mg/l), Cl^? (1000–2000 mg/l) designate the marine water contamination. Further, static groundwater head measurements demarcate the study area into above mean sea level (MSL) and below MSL zones. This study has provided a rapid and comprehensive picture about spatial variations of groundwater contamination which can help in planning, protection and safe management of coastal aquifers in India and worldwide.     

Characterisation of groundwater chemistry in an eastern coastal area of Cuddalore district,Tamil Nadu

The groundwater quality detoriation due to various geochemical processes like saline water intrusion, evaporation and interaction of groundwater with brines is a serious problem in coastal environments. Understanding the geochemical evolution is important for sustainable development of water resources. A detailed investigation was carried out to evaluate the geochemical processes regulating groundwater quality in Cuddalore district of Tamilnadu, India. The area is entirely underlined by sedimentary formations, which include sandstone, clay, alluvium, and small patches of laterite soils of tertiary and quaternary age. Groundwater samples were collected from the study area and analyzed for major ions. The electrical conductivity (EC) value ranged from 962 to 11,824 μS/cm, with a mean of 2802 μS/cm. The hydrogeochemical evolution of groundwater in the study area starts from Mg-HCO₃ type to Na-Cl type indicating the cation exchange reaction along with seawater intrusion. The Br/Cl ratio indicates the evaporation source for the ion. The Na/Cl ratios indicate groundwater is probably controlled by water-rock interaction, most likely by derived from the weathering of calcium-magnesium silicates. The plot of (Ca+Mg) versus HCO₃ suggests ions derived from sediment weathering. The plot of Na+K over Cl reflects silicate weathering along with precipitation. Gibbs plot indicates the dominant control of rock weathering. Factor analysis indicates dominance of salt water intrusion, cation-exchange and anthropogenic phenomenon in the study.     

Aquifer characteristics and its modeling around an industrial complex,Tuticorin, Tamil Nadu,India: A case study

Anthropogenic pollution of shallow groundwater resources due to industrial activities is becoming a cause of concern in the east coastal belt of the state of Tamil Nadu, India. Integrated hydrogeological, geophysical and tracer studies were carried out in the coastal region encompassing an industrial complex. The objective has been to gain knowledge of aquifer characteristics, ascertaining groundwater movement and its flow direction, which would in turn reveal the possibility of contamination of groundwater regime and its better management. The results of multi-parameters and model study indicate that the velocity of groundwater flow ranges from 0.013 m/d to 0.22m/d in and around the industrial complex in upstream western part of the catchment and 0.026 m/d to 0.054m/d in the downstream eastern part, near the coast. These parameters are vital for the development of groundwater management scheme.     

Quality assessment and hydrogeochemical characteristics of groundwater in Agastheeswaram taluk,Kanyakumari district,Tamil Nadu,India

The present study investigates the hydrogeochemical characteristics of groundwater quality in Agas- theeswaram taluk of Kanyakumari district, Tamil Nadu, India. A total of 69 groundwater samples were collected during pre- and post-monsoon periods of 2011-2012. The groundwater quality assessment has been carried out by evaluating the physicochemical parameters such as pH, EC, TDS, HCO3, Cl, SO42-, Ca2＋, Mg2＋, Na＋ and K＋ for both the seasons. Based on these parameters, groundwater has been assessed in favor of its suitability for drinking and irrigation purpose. Dominant cations for both the seasons are in the order of Na＋〉 Ca2＋〉 Mg2＋ 〉 K＋ while the dominant anions for post monsoon and pre monsoon have the trends of CI 〉 HCO3 〉 SO42- and HCO3- 〉 CI 〉 SO42-, respectively. Analytical results observed from various indices reveal that the groundwater quality is fairly good in some places. Analytical results of few samples show that they are severely polluted and incidentally found to be near the coasts, estuaries and salt pans in the study area. The Gibbs plot indicates that the majority of groundwater samples fall in rock dominant region, which indicates rock water interaction in the study area. The United States salinity （USSL） diagram shows that the groundwater is free from sodium hazards but the salinity hazard varies from low to very high throughout the study area. This reveals that the groundwater is moderately suitable for agricultural activities. The observed chemical variations in pre-monsoon and post-monsoon seasons may be the effect to rock-water interactions, ion-exchange reactions, and runoff of fertilizers from the surrounding agricultural lands.     

A study of natural site formation processes in the Kortallayar Basin,Tamil Nadu,South India

This article presents the results of a study of natural processes influencing the formation of Palaeolithic sites, in a ferricrete landscape, in the Kortallayar basin, Tamil Nadu, South India. The principal points discussed here include the Quaternary geomorphology and Palaeolithic archaeology of the region and the methodology used for the study of site taphonomy. As a result of this research, Palaeolithic sites were categorized into several types based on their sedimentary context, artefact spatial distribution, and morphology and degree of integrity. This work is the first of its kind in establishing a methodology for the study of Palaeolithic sites in ferricrete landscapes in India. The results of this research may be relevant to understanding the study of formation processes at sites in similar contexts elsewhere in the Subcontinent. © 1999 John Wiley & Sons, Inc.     

Hydrogeochemistry and microbial contamination of groundwater from Lower Ponnaiyar Basin, Cuddalore District, Tamil Nadu, India

Groundwater is the major source of fresh water in regions where there is inadequate surface water resources. Forty-seven groundwater samples were collected from Lower Ponnaiyar basin, Cuddalore District, south India, during the premonsoon (PRM) and postmonsoon (POM) seasons of 2005. Out of 47 groundwater samples, 15 samples showing higher nitrate concentration were those collected during PRM 2005. Microbial analysis of these samples was carried out by employing 16S rRNA gene sequence tool. Detailed analysis was conducted to determine the hydrogeochemical processes and microbial contamination responsible for deterioration of quality. The abundance of the ions during PRM and POM are in the following order: Na?>?Ca?>?Mg?>?K?=?Cl?>?HCO₃?>?SO₄?>?CO₃. The dominant water types in PRM are in the order of NaCl?>?CaMgCl?>?mixed CaNaHCO₃, whereas during POM NaCl?>?CaMgCl?>?mixed CaNaHCO₃, and CaHCO₃. However, NaCl and CaMgCl are major water types in the study area. The quality of groundwater in the study area is mainly impaired by surface contamination sources, mineral dissolution, ion exchange and evaporation. Groundwater chemistry was used to assess quality to ensure its suitability for drinking and irrigation, based on BIS and WHO standards. Suitability for irrigation was determined on the basis of the diagram of US Salinity Laboratory (USSL), sodium absorption ratio (SAR), residual sodium carbonate (RSC), and Na%. According to SAR and USSL classification, 27.66% (PRM) and 40.43% (POM) of samples fall under C3S2 category, indicating high salinity and medium sodium hazard, which restrict its suitability for irrigation. Microbiological analysis and its effects on the water quality were also addressed. The 16S rRNA gene sequences of 11 bacterial contaminants exhibited five groups with 11 operational taxonomic units with aerobic and facultatively anaerobic organisms. The presence of aerobic organisms in the groundwater samples reflects the active conversion of ammonia to nitrite by Nitrosomonas sp. which is further converted to nitrates by other organisms. Further the presence of nitrate reducers could also play a role in the process of conversion of nitrate to ammonia and nitrate to molecular nitrogen.     

Assessment of surface water potential and groundwater recharge in ungauged watersheds: a case study in Tamil Nadu,India

Many of the states in India have been facing water scarcity for more than 2 decades due to increased demand, because of the increase in population and higher living standards. Consequently, many states have almost fully utilized the available surface water resources and are exploiting groundwater to augment water supplies. Investigations were carried out in the upper Thurinjalar watershed of Ponnaiyar basin in Tamil Nadu to determine the availability of surface water and to investigate the potential for enhancing groundwater recharge to support the water demand in the watershed. Increasing the water availability would also enable the community to convert the 46% of the land area in the watershed that is currently underutilised into productive uses. The surface water potential for the upper Thurinjalar watershed was assessed by applying the USDA–NRCS model with daily time steps. This modelling exercise indicated that the annual runoff from the 323 km² area of the watershed is 61 million m³. Groundwater recharge in the watershed was assessed by carrying out daily water balance method and indicated that about 43 million m³ of water from recharge is available on an annual basis or about 14% of annual rainfall. A simple regression model was developed to compute groundwater recharge from rainfall based on water balance computations and this was statistically verified. The modelling indicated that there is sufficient water available in the watershed to support current land uses and to increase the productivity of underutilised land in the area. The study also demonstrates that simple regression models can be used as an effective tool to compute groundwater recharge for ungauged basins with proper calibration.     

The Ghingee Granite, Tamil Nadu, South India: Geochemistry and Petrogenesis

The Palaeo-Proterozoic Ghingee granite is an anatectic granite formed in high grade granulite terrain by ultrametamorphism. The compositional variations both in major and trace elements observed in this granite (SiO₂ : 64.16-73.81; Fe₂O₃ : 0.12-2.19; FeO : 0.12-2.80; MgO : 0.10-2.19; CaO : 1.66-4.71; K₂O : 1.09-5.09; Ba: 223-1883 ppm; Cr : 4-60 ppm) are attributed to a) source rock heterogeneity and b) the tectonic disturbances that might have abruptly ended the anatectic melting process. The granite is compositionally similar to Perur, Closepet and Hyderabad granites and is formed during Archaean-Proterozoic transition by anatectic and crustal remelting processes.     

GIS model-based morphometric evaluation of Tamiraparani subbasin, Tirunelveli district, Tamil Nadu, India

A morphometric evaluation of Tamiraparani subbasin was carried out to determine the drainage characteristics using GIS model technique. Extraction of the subbasin and stream network model has been developed to quantify the drainage parameters in the study area. The input parameters required to run this model are: a pour point, a minimum upstream area in hectares, and a digital elevation model. After execution, the model provides a drainage basin with Strahler’s classified stream network supported by thematic layers like aspect, slope, relief, and drainage density. The developed model reveals that the drainage area of this subbasin is 2,055 km² and shows subdendritic to dendritic drainage pattern. The basin includes seventh order stream and mostly dominated by lower stream order. The slope of the study area varies from 0° in the east to 61° towards west. The presence of Western Ghats is the chief controlling factor for slope variation. Moreover, the slope variation is controlled by the local lithology and erosion cycles. The bifurcation ratio indicates that the geological structures have little influence on the drainage networks and the drainage density reveals that the nature of subsurface strata is permeable.     

Deformation style in the Granulite-charnockite province of South India: An example from the Kusulmalai area in Salem district,Tamil Nadu,India

A multiple-deformation sequence is established for different types of gneisses, mafic-paleosomes and banded magnetite quartzites (BMQ) exposed within the area. In gneisses, the basin-shaped map pattern represents the type-i interference structure formed due to the overprinting of F₃ folds with ENE striking axial planes on F₂ folds with axial planes striking NNW. The BMQ band occurring as an enclave within the gneissic country, represents a large scale F₁ fold with relatively smaller scale F₂ folds developed on its limbs. Mafic-paleosomes within the streaky-charnockitic-gneisses exhibit structures formed due to the interference of more than two phases of folding (F₁,F_la,F₂,F₃). It is shown that the deformation plan in these rocks is consistent with the generalized deformation scheme for Granite-greenstone belts. The difference in the map pattern of Granite-greenstone belts and Granulite-charnockite terrains is ascribed to the variance in Theological properties, layerthickness ratios and local displacement directions during different phases of folding. These differences apart, both the Granite-greenstone and Granulite-charnockite provinces in South India are deformed by an early isoclinal folding which is successively overprinted by folding on NNW and ENE striking axial planes.     

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, bicarbonate?+?chloride dominated the anions, with few representations for sulphate. Sodium?+?potassium 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.     

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.     

Relative effect-based landslide hazard zonation mapping in parts of Nilgiris, Tamil Nadu, South India

The Nilgiri massif, South India, is chronically prone to landslides due to deforestation and the resultant direct entry of rainwater and the final increases of pore pressure leading to landslides in the region. In order to understand such landslide causes, the relative effect method, a new technique, has been adopted for the study area. Among various methods, this is a statistical method developed within the framework of the Geographic Information System to map landslide hazard zones in a mountainous environment. To determine the relative effect (RE) of the factors influencing landslides, data layers of geology, land use/land cover, geomorphology, slope, lineament density, drainage density, and soil were analyzed by calculating the ratio of the unit portion in coverage and landslide, this function that is logarithmic. To quantify the magnitude of factors influencing each grid unit, REs were summed and classified into zones of low-, moderate-, and high-landslide hazard zones. It is also appropriate to follow suitable measures to prevent the landslides in the study area by involving all stockholders and with the active participation of local communities.     

Hydrochemical characteristics and groundwater quality assessment in Tirupur Region, Coimbatore District, Tamil Nadu, India

Groundwater samples from 62 locations have been collected from Tirupur region viz. Avinashi, Tirupur and Palladam taluks of Coimbatore District. The extensive agricultural industrial activities and urbanization resulted in the contamination of the aquifer. To study the contamination of groundwater, water samples were collected in an area of 180 km² and analysed for major cations and anions. Most of the locations are contaminated by higher concentration of EC, TDS, K and NO₃. Major hydro chemical facies were identified using Piper trilinear diagram. Based on US salinity diagram, most of the samples fall in the field of C3S1, indicating high salinity and low sodium water, which can be used for almost all types of soil with little danger of exchangeable sodium. Majority of the samples are not suitable for domestic purposes and far from drinking water standards. However, PI values indicates that groundwater is suitable for irrigation.     

A study on hydrochemical elucidation of coastal groundwater in and around Kalpakkam region, Southern India

The chemical composition of 29 bore well water samples throughout the Kalpakkam region, South India, was determined to identify the major hydrogeochemical processes and the suitability of groundwater for domestic and irrigation purposes. The hydrochemical data were analyzed with reference to World Health Organization (WHO) standards and their hydrochemical facies were determined. The Piper plot shows that most of the groundwater samples fall in the field of mixed calcium–sodium–bicarbonate type followed by sodium–chloride, calcium–bicarbonate and mixed calcium–magnesium–chloride water types. The concentration of total dissolved solids exceeds the desirable limit in about 14% of samples; alkalinity values exceed the desirable limit in about 34% of the samples. The concentration of sulphate is well within the desirable limit at all the locations. The dominance of various heavy metals in the groundwater followed the sequence: Zn > Fe > Mn > Cu > Ni > Pb > Cr > Cd. Among the metal ions, the concentration of chromium and cadmium are within the permissible limit. Data are plotted on the US Salinity Laboratory diagram, which illustrates that most of the samples fall in the field of high salinity and low sodium hazard, which can be used to irrigate salt tolerant and semi-tolerant crops under favorable drainage conditions. Based on the analytical results, chemical indices like sodium adsorption ratio and residual sodium carbonate were calculated which show that most of the samples are good for irrigation.     

Identification of groundwater contamination sources in Dindugal district of Tamil Nadu,India using GIS and multivariate statistical analyses

The purpose of this research is to evaluate the groundwater quality in Dindugal district of Tamil Nadu based on the water quality index by geographic information system (GIS) and statistical analysis. This area consists of 80 functional tanneries around Dindigul town with a capacity to process about 200 Mt of hides and skins as leather. In 13 villages, as many as 1090 houses were damaged by tannery contamination. A total of 66 groundwater samples were collected to identify the geochemical sources and contamination. The order of major cations is Na > Ca > Mg > K, while that of anions is Cl > SO₄ > HCO₃ > F > PO₄. CaCl₂, MgCl₂, and (CaHCO₃)₂ types suggested that the mixing of high-salinity water was caused by irrigation return flow, domestic wastewater, and septic tank effluents, with existing water followed by ion exchange reactions. Moreover, Gibbs plots indicated that groundwater contamination was derived from the weathering of granitic gneisses as well as the leaching of evaporated and crystallized ions from agricultural and industrial effluents. The water quality index (WQI) exhibited 8 % of the groundwater samples were not suitable for drinking purpose. The GIS maps showed that the poor water quality decreased toward the southern part of the study area. WQI of TDS, fluoride, sodium, potassium, and bicarbonate were high in groundwater. Multivariate statistical analyses (principal component analysis (PCA), factor analysis (FA)) suggested that the groundwater chemistry was changed by the weathering of source rocks ion exchange and leaching of inorganic components and addition from anthropogenic effluents. Finally, it is thought that the monitoring and assessment works are very useful to understand the degree and sources of groundwater contamination.     

A linear regression model (LRM) for groundwater chemistry in and around the Vaniyambadi industrial area, Tamil Nadu, India

A linear regression model in conjunction with cluster analysis was applied to the groundwater quality parameters for the Vaniyambadi industrial area, Tamil Nadu, India. These physico-chemical parameters were collected from 25 wells by intensive groundwater sampling conducted during January 2010. All the major ions, pH and electrical conductivity were analyzed. The abundances of cations were in the order of Na 相似文献