Identification of hydrogeochemical processes controlling groundwater quality in Tripura, Northeast India using evaluation indices, GIS, and multivariate statistical methods

Tripura is a water-rich administrative state in the Northeastern part of India. Though groundwater is the main source of drinking water, groundwater monitoring and historical data on the groundwater quality of this state is relatively scarce. This study aims to identify the sources and processes controlling the hydrochemical evolution of groundwater in Hezamara block in Tripura. Interpretation of measured parameters using geochemical plots, analysis of ionic ratios, multivariate statistical techniques, and spatial interpolation methods indicated both natural and anthropogenic sources. Results show that precipitation is the dominant process controlling the groundwater quality followed by rock–water interaction. Carbonate dissolution and silicate weathering were the major geochemical processes. The findings showed that the concentration of few heavy metals (iron, manganese, and lead) exceeded the drinking water quality standards. Evaluation of the results through various heavy-metal indices showed that several locations exceeded the limits and pose a risk to humans. Potential non-carcinogenic risk through the drinking water pathway was also identified. Pollution mapping indicates that only less than 1 km2 of the study area is suitable for drinking use. This study recommends installation of public drinking water supply in this area to reduce the impact of heavy-metal contamination on human health. Moreover, the water should be treated before supplying for public use.