Identification of major sources controlling groundwater chemistry from a hard rock terrain — A case study from Mettur taluk, Salem district, Tamil Nadu, India

Journal of Earth System Science (Impact Factor: 1.04). 02/2008; 117(1):49-58. DOI: 10.1007/s12040-008-0012-3

ABSTRACT The study area Mettur forms an important industrial town situated NW of Salem district. The geology of the area is mainly
composed of Archean crystalline metamorphic complexes. To identify the major process activated for controlling the groundwater
chemistry an attempt has been made by collecting a total of 46 groundwater samples for two different seasons, viz., pre-monsoon
and post-monsoon. The groundwater chemistry is dominated by silicate weathering and (Na + Mg) and (Cl + SO4) accounts of about 90% of cations and anions. The contribution of (Ca + Mg) and (Na + K) to total cations and HCO3 indicates the domination of silicate weathering as major sources for cations. The plot for Na to Cl indicates higher Cl in
both seasons, derived from Anthropogenic (human) sources from fertilizer, road salt, human and animal waste, and industrial
applications, minor representations of Na also indicates source from weathering of silicate-bearing minerals. The plot for
Na/Cl to EC indicates Na released from silicate weathering process which is also supported by higher HCO3 values in both the seasons. Ion exchange process is also activated in the study area which is indicated by shifting to right
in plot for Ca + Mg to SO4 + HCO3. The plot of Na-Cl to Ca + Mg-HCO3-SO4 confirms that Ca, Mg and Na concentrations in groundwater are derived from aquifer materials. Thermodynamic plot indicates
that groundwater is in equilibrium with kaolinite, muscovite and chlorite minerals. Saturation index of silicate and carbonate
minerals indicate oversaturation during pre-monsoon and undersaturation during post-monsoon, conforming dissolution and dilution
process. In general, water chemistry is guided by complex weathering process, ion exchange along with influence of Cl ions
from anthropogenic impact.

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Available from: Chidambaram Sabarathinam, Dec 22, 2013
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    • "The plot of Ca 2+ +Mg 2+ versus SO 2− 4 +HCO − 3 is used to determine the ion exchange process (Srinivasamoorthy et al. 2008). Points will be close to the 1:1 line (Fig. 6b), if the dissolution of calcite, dolomite, and gypsum will be dominant process in the system. "
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    ABSTRACT: The advent of green revolution, increase of industrialization, and fast pace of urbanization and population explosion have induced unplanned abstraction of groundwater for more than 5 decades causing decline in water table. Groundwater is being depleted at a mean rate of \(4.0\pm 1.0\) cm/year over the Indian states of Rajasthan, Punjab, and Haryana (including Delhi). Groundwater quality is vulnerable to anthropogenic and geogenic sources. Hydrogeochemical processes occurring in an area are generally governed by climatic factors, soil and rock–water interaction, internal mixing, other geochemical processes, and the landuse and landcover practices. The impacts of these processes on groundwater quality can be deciphered using conventional graphical plots, water facies, and saturation indices (estimated using PHREEQC). Several water quality indices were also evaluated to characterize the suitability of water for drinking and irrigation purpose. It was observed that the climatic conditions coupled with rock–water interaction, weathering, and ion exchange are controlling the geochemistry of groundwater in this region. The water table is rising in some regions due to seepages from canal, thus imparting brackish/saline character to groundwater quality and therefore making it unfit for drinking, domestic use, and irrigation. The saturation indices indicate the undersaturation of minerals such as fluorite and gypsum, leading to augmentation of fluoride in groundwater. It is imperative to pay particular attention to practices in areas where aquifers are highly vulnerable to reduce pollution and its impact on public health. This means that proper landuse planning and agricultural practices have to be enforced in the most sensitive areas.
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    • "The hard rock aquifers have groundwater accumulated in cracks and interconnected joints; the movement of groundwater is very slow which indirectly enhances the dissolution of the aquifer matrix. The increase of the residence time in hard rock aquifers is generally reflected in the higher Electrical conductivity (EC) (Chidambaram 2000; Srinivasamoorthy et al. 2008). Having a short half-life, 222 Rn in groundwater attains a secular equilibrium with 226 Ra in the aquifer matrix in the regions with low velocity or with increased residence time. "
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    ABSTRACT: Measurement of dissolved radon (222Rn) activity concentration in groundwater samples from private and public hand pumps, and in bore wells located at Madurai district of Tamilnadu, India, are presented. The study attempts to identify the background value of 222Rn in groundwater of hard rock terrain and the main aquifer contributing 222Rn, and to determine if any correlation exists with observed field parameters. Measured parameters included pH, TDS, Temperature and Rn in 42 samples for two seasons (South West Monsoon [SWM] and North East Monsoon [NEM]). The results show that the 222 Rn activity concentration of the samples ranged from 0.049 to 59.952 Bq/L in South west monsoon and 0.12 to 211.60 Bq/L in North east monsoon. The higher activity was noted in NEM and the highest Rn concentrations were observed in granitic terrains in both seasons. The average values of the parameters studied shows that there is a general decrease of TDS and Temperature, but an increase in 222 Rn and pH during NEM. The spatial representation of the activity shows that maximum values are in the north eastern part of the study area. Further, correlations between the measured parameters show that temperature has a negative correlation to the samples of charnockite formation during both seasons; pH and TDS also show negative relationships to 222Rn during SWM.
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    • "); Jaipur city, Rajasthan (Tatawat and Chandel 2008); Malda district of West Bengal (Pukrait and Mukharjee 2008); Industrial area of Mettur taluk, Salem district, Tamil Nadu (Srinivasamoorthy et al. 2008); Manimuktha River basin, Tamil Nadu (Kumar et al. 2009); Bhavanagar region, Gujurat (Mishra et al. 2009); Erode district, Tamilnadu (Karthikeyan et al. 2010); Parts of Nalgonda District, Andhra Pradesh (Brindha and Elango 2010); Tirupur Region, Tamil Nadu (Karuppapillai and Krishnan 2010); Chithar River basin, Tamil Nadu (Brindha and Elango 2010). Chemical classification reveals the concentration of various predominant cations, anions and their interrelationship . "
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    ABSTRACT: A hydro-environmental assessment has been performed for Hirakud command area (India) in terms of quantity and physicochemical quality analysis of groundwater. Quantity analysis has been performed in terms of water level variation and groundwater potential zone identification. Groundwater table fluctuation analysis reveals that water level is declining rapidly due to insufficient recharge owing to frequent recession of monsoon and excessive pumping of groundwater. Inefficient distribution of canal water especially in the tail end of the Hirakud command is accentuating the high dependency on ground water. The groundwater potential zone index map is generated using analytic hierarchy process along with different influencing features, e.g., land use/cover, soil type, geology. Three zones have been identified for Hirakud command area (poor: 21.15 %, moderate: 46.32 %, and good: 32.53 %). Physical and chemical parameters of groundwater, e.g., electrical conductivity, pH, total dissolved solids, total hardness, nitrate, iron, sodium, potassium, calcium, magnesium, chlorine, bicarbonate and fluoride are analyzed for the study area. Piper analysis is used to identify dominant hydrochemical facies. United States Salinity Laboratory and Wilcox Diagram are used to determine the irrigation water quality. Principal component analysis is utilized to find out key groundwater quality parameters. The chemical analysis shows that values of all parameters are within permissible limit. However, nitrate, iron and fluoride are found above permissible limit in some areas. The assessment reveals the state of the aquifer in terms of quantity and quality.
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