Hydrogeochemical processes and impact of tanning industries on groundwater quality in Ambur, Vellore district, Tamil Nadu, India.

The present study was carried out to determine the hydrogeochemical processes and the impact of tanning industries on groundwater in Ambur, Vellore district, Tamil Nadu, India. Thirty groundwater samples were collected during pre monsoon (July 2015) and post monsoon (January 2016) from the open and shallow wells around this region and were analyzed for major ions and chromium. The major ion concentration follows the order of Na+ > Ca2+ > Mg2+ > K+ (cations) and Cl- > HCO3- > SO42- > NO3- (anions) for both seasons. The high concentrations of Na+, Cl-, and Cr around the tannery regions indicate the impact of effluent discharged from tannery units. In general, the groundwater of this study area is of Na+-Cl- type, which is due to the mixing of tannery effluent and cation exchange process. Ionic ratio indicates that the silicate weathering influences the groundwater chemistry. The permissible limit of chromium in the groundwater exceeds in over 50 % of the sampling wells. The factor analysis reveals that the dominant source for ionic contents is due to tannery effluents and cation exchange processes. To overcome this situation, it is essential to improve the performance of the effluent treatment plants so as to remove the salinity of wastewater and to plan for rainfall recharge structures for improving the groundwater recharge.