Physicochemical characterization and quality assessment of groundwater around the Twangiza gold mine (Eastern D.R. Congo)

The present study focuses on groundwater around the Twangiza gold mine, which serve as a source of drinking water for the local population, with the aim of characterizing it based on its physicochemical properties. A total of 13 water samples were collected for analysis of physicochemical characteristics (pH, TDS, EC, TSS, major cations and anions), using conventional analytical methods. The results indicated acidic to neutral and ranged from 4.5 to 7.1, with 76.9 % acidic (pH 4–6.5), below WHO and EU permissible limits. The hydrochemical facies of groundwater revealed Mg-Ca-SO₄ water types in the vicinities of the mine, indicating sulphate imprint related to the dissolution of gold bearing sulphides, and Ca-Mg-HCO₃ types downstream the mine, more associated with carbonate minerals. Multivariate statistical analysis grouped groundwater based on similarities of physicochemical parameters and indicated the parts of geogenic process and anthropogenic activities in the mineralization. Water-rock interactions involved mainly silicate weathering and indicated the role of sulphide dissolution in the surrounding areas close to the mine. The sodium adsorption rate classified the water as excellent to good, with an overall low alkalizing power, which makes the water suitable for irrigation. The Water Quality Index (WQI) indicated that local groundwater quality ranged from excellent to good across most stations, with the exception of one station within the active mine classified as poor. These findings are helpful for the understanding of groundwater mineralization processes and would assist in the sustainable use of groundwater.