A comparative assessment of Lead (Pb) concentration and physicochemical parameters in groundwater from the Kabwe mine and Lusaka non-mine sites, Zambia

Abstract

This study addresses the comparative influence of physicochemical parameters on the dissolution of Pb and its levels in the groundwater of former Pb mining areas in Kabwe and non-mining areas in Lusaka, Zambia. This cross-sectional study analyzed 61 groundwater samples from hand pump boreholes using atomic absorption spectrometry. Physicochemical parameters were measured, including electrical conductivity (EC), temperature, total dissolved solids (TDS), and pH. Statistical analysis involved the Wilcoxon test, Spearman’s correlation, robust linear regression, Principal component analysis (PCA), and generalized additive models. Pb concentrations were particularly higher (p = 0.029; median = 0.131 mg/L) in mining areas compared to non-mining areas (median = 0.071 mg/L). The EC in the mining areas (median = 585 µS/cm) was significantly (p = 0.001) lower than those in the non-mining area (median = 1100 µS/cm). Likewise, TDS levels revealed a significant (p = 0.001) difference between the mining area (median = 303 ppm) and the non-mining area (median = 601 ppm). The median pH values for groundwater samples in the mining and non-mining areas were 6.96 and 7.27, respectively. Spearman’s rank correlation revealed a significant (rho = − 0.405; p = 0.036) inverse relationship between Pb concentrations and pH in non-mining areas. Robust linear regression and generalized additive models underscored a significant (p = 0.016) non-linear relationship between temperature and Pb across all areas, with the non-mining area demonstrating a significant (p = 0.003) non-linear relationship between temperature and pH concerning Pb. The study associates mining activities with increased Pb concentrations, underscoring it as a principal contamination source. In contrast, elemental dissolutions from the basement limestone with dolomite might increase Pb concentration in the non-mining areas. The observed positive relationship between temperature and pH in non-mining areas highlights its positive interactions with Pb mobility while temperature greatly influences Pb dissolutions in mining areas.