Mechanisms controlling groundwater chemistry and assessment of potential health risk: A case study from South India

Abstract

Protection and management of groundwater resources depends on full understanding of the processes controlling the groundwater chemistry and associated health risks. In view of this, the rural part of Wanaparthy district, Telangana State, India was chosen for the present study and the groundwater samples collected from there were chemically analyzed. Quality of groundwater is of alkaline nature and mostly fresh water type. According to Trilinear Diagram, the change of groundwater quality from Ca2+- HCO3− type to Na+- Cl− type through mixed water type suggests the gradual influence of anthropogenic activities on the aquifer system. Gibbs Diagrams demonstrate that the chemistry of groundwater is mainly controlled by rock-water interactions and the rest by evaporation due to impact of anthropogenic sources. Bivariate Diagrams (Na+vsCl−, Ca2++Mg2+vsSO42−+ HCO3− and Ca2++Mg2+- SO42−- HCO3−vs Na+- Cl−) clearly specify that the processes of weathering and dissolution of minerals, and ion exchange are the dominant controlling factors of groundwater chemistry. Hierarchical R-type Cluster Analysis illustrates that Group I (Cl−- Na+ and HCO3−) is considered natural contribution, Group 2 (SO42−- Mg2+- Ca2+) is natural or anthropogenic source and Group 3 (NO3−- K2+ - F−) is anthropogenic influence. As per the estimation of sources of ions in the groundwater body by Unmix Model, the Source 1 (NO3−, Cl−, SO42− and Na+) is related to the anthropogenic activities; Source II (Ca2+, HCO3−, Na+, SO42−, Mg2+ and Cl−) to the weathering of silicate minerals, dissolution of chloride and sulfate minerals; and Source III (K+, F−, Ca2+, HCO3− and Mg2+) to the weathering of fluoride, calcium, magnesium and potassium bearing minerals or the application of chemical compounds of potassium and fluoride ions. These sources lead to groundwater contamination in some locations, thereby causing unfit for drinking purpose. Health Risk Assessment with respect to NO3− and F− ions suggests that the Total Hazard Index of non-carcinogenic risk (> 1.0) is observed from 26.67%, 26.67% and 43.33% of the total groundwater samples and the threat is to children compared to men and women due to their smaller body weights. Therefore, the health risk reduction measures are recommended to improve the groundwater quality in the study region.