ABSTRACT
The mining of Kolar Gold Fields (KGF), Karnataka, carried out for more than a century, has largely impacted the groundwater aquifers. In addition to the water logged sulfide-rich gold (Au) minerals, the leaching of mine tailing dumps had introduced hazardous elements and cyanide into the aquifer system. A detailed survey covering a radius of 10 km of the Kolar Gold Field, with samples from 53 borewells were collected during pre and post-monsoon seasons of 2018, and different parameters were assessed. Contradicting the previous reports, the mineral dissolution and contaminant transport was found to be the function of pH. Almost 80% of the water samples exceeded the regulatory limits of potable water criteria with excess arsenic (12-127 µg/L), fluoride (>1.5 mg/L), dissolved salts (>500 mg/L) and total hardness (>382–1027 mg/L). Additionally the nitrate and sulphates are also above the regulatory limits. A multiple regression model was developed to predict Water Quality Index (WQI) of groundwater from each borewell for the different seasons. From the hydrogeochemical facies, it can be concluded that the dissolution of sulfide bearing Au-rich minerals, releasing H3AsO+ at low pH is transported through, facilitating rock weathering, results in groundwater composition of Ca–HCO3 type and Ca–Na–HCO3 or Ca–Mg–Cl type.
