Hydrogeochemical characterization of groundwater of peninsular Indian region using multivariate statistical techniques

Abstract

Groundwater quality of Chennai, Tamil Nadu (India) has been assessed during different seasons of year 2012. Three physical (pH, EC, and TDS) and four chemical parameters (Ca2+, Cl−, TH, Mg2+ and SO42−) from 18 bore wells were assessed. The results showed that pH of majority of groundwater samples indicates a slightly basic condition (7.99post-monsoon and 8.35pre-monsoon). TH was slightly hard [322.11 mg/lpre-monsoon, 299.37 mg/lpost-monsoon but lies under World Health Organization (WHO) upper limit]. EC, TDS, Ca2+ and Mg2+ concentrations were under WHO permissible limit during post-monsoon (1503.42 μS/cm, 1009.37, 66.58 and 32.42 mg/l respectively) and pre-monsoon (1371.58 μS/cm, 946.84, 71.79 and 34.79 mg/l, respectively). EC shows a good correlation with SO42− (R2 = 0.59pre-monsoon, 0.77post-monsoon) which indicates that SO42− plays a major role in EC of ground water of bore wells. SO42− has also showed positive correlations with TDS (R2 = 0.84pre-monsoon, 0.95post-monsoon) and TH (R2 = 0.70pre-monsoon, 0.75post-monsoon). The principal component analysis (PCA)/factor analysis (FA) was carried out; Factor1 explains 59.154 and 69.278 % of the total variance during pre- and post-monsoon, respectively, with a strong positive loading on Ca2+, Mg2+, SO42−, TDS and a negative loading on pH. Factor2 accounts for 13.94 and 14.22 % of the total variance during pre- and post-monsoon, respectively, and was characterized by strong positive loading of only pH and poor/negative loading of EC, Ca2+, Mg2+, SO42−, TDS and TH during pre- and post-monsoon. We recommend routine monitoring and thorough treatment before consumption. Further, this study has demonstrated the effectiveness of PCA/FA to assess the hydrogeochemical processes governing the groundwater chemistry in the area.