Assessment and modelling of groundwater quality data and evaluation of their corrosiveness and scaling potential using environmetric methods in Bangalore South Taluk, Karnataka state, India

Abstract

Study Area is located in the southwestern part of Bangalore South Taluk, Bangalore district, Karnataka state between 12°48′24.52″ to 12°53′59.85″ North latitude and 77°24′59.95″ to 77°30′6.72″ East Longitude. The major hydro-chemical facies that predominates in the study area is Ca2+-Mg2+-HCO 3 − type during both pre- and post-monsoon seasons of the year 2007, could be as a result of dissolution of carbonate minerals like calcite and dolomite prevailing in the study area. However, cation-exchange processes could be responsible for the formation of the Ca2+-Mg2+-Cl−-SO 4 2− water type (∼32%) from the CaSO4, MgCO3 and NaCl type that are formed due to the dissolution of anhydrite, gypsum, magnesite and halite. Besides, suitability of water for irrigation is evaluated based on sodium adsorption ratio, residual sodium carbonate, sodium percent, salinity hazard and USSL diagram. Hydrogeochemical speciation model calculations carried out using WATEQ4F program showed similar seasonal variation in the concentration of saturation indices of specific mineral phases, majority of the samples kinetically saturated with carbonate minerals (viz., aragonite, calcite and dolomite) indicating the influence of carbonate mineral phases on the chemistry of groundwater. On one hand, the samples were significantly oversaturated with Florapatite while on the other, they were undersaturated with respect to with anhydrite, gypsum and fluorite with halite being highly undersaturated. The Gibbs plots also gave an indication that there exists an interaction between rock and the percolating water into the subsurface by means of mineral dissolution. Factor analysis determined two factors mainly responsible for water quality during pre- and post-monsoon seasons, accounting to 52.84% and 51.09% of total variance respectively. Q-mode HCA Cluster analysis grouped the sampling stations into three clusters based on the similarity of water quality while R-mode HCA grouped analyzed parameters into two groups based on the effects of factors in the hydrochemistry.