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

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 + SO 4 ) accounts of about 90% of cations and anions. The contribution of (Ca + Mg) and (Na + K) to total cations and HCO 3 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 HCO 3 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 SO 4 + HCO 3 . The plot of Na − Cl to Ca + Mg − HCO 3 − SO 4 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.

Use of Hydrochemistry and Stable Isotopes as Tools for Groundwater Evolution and Contamination Investigations

“…The chloride in groundwater ranges from 79.7 to 1453.5 mg/l, with average value of 437.7 mg/l. Due to the absence of chloride bearing minerals in the study area anomalous high Cl might have been derived from anthropogenic sources (Srinivasamoorthy et al, 2008). The bicarbonate ion ranges from 183.0 to 854.2 mg/l with an average value of 403.3 mg/l.…”

Evaluation of Groundwater Quality and Its Suitability for Domestic and Irrigation Use in Parts of the Chandauli-Varanasi Region, Uttar Pradesh, India

“…WQI calculation has been done by assigning weights (w i ) according to relative importance of each chemical parameter for drinking purposes ( Table 4). The parameters like chloride, nitrate, total dissolved solids, fluoride, iron and sulfate has been assigned maximum weight 5 because of the major importance in water quality assessment [27]. Bicarbonate and phosphate is given the minimum weight of 1 as it plays an insignificant role in the water quality.…”

Importance of Rocks and Their Weathering Products on Groundwater Quality in Central-East Cameroon

“…Moreover, the dispersion of points around the 1:1 line on the (Ca 2+ + Mg 2+ ) versus (HCO 3 − + SO 4 2− ) plot (Figure 6b) indicates that Ca 2+ and Mg 2+ enrichment in waters does not originate from the dissolution of carbonate minerals [28,51]; this statement result confirms that the weathering of silicates is the main source of the alkaline earth metals in waters. The (Na + K)/total cations ratios range from 0.25 to 0.61, with 83% of the values less than 0.5, suggesting that weathering of silicate minerals is the source of major cations in groundwater in the study area [52]. The Na/Cl ratio is equal to one in the groundwater when these two ions derive from the dissolution of halite in salt horizons [53].…”