Heavy metals occurrence, assessment and distribution in water resources of the lead–zinc mining areas of Abakaliki, Southeastern Nigeria

The assessment, occurrence and distribution of heavy metals in water resources of the lead–zinc mining areas of Abakaliki, Southeastern Nigeria, were carried out. Major communities including Enyigba, Mkpuma Akpatakpa, Ameka, Amorie, Amanchara and Alibaruhu where active and abandoned mines are located were assessed. This study compared the prevalence of these metals in the different mining communities. One hundred and six water samples were analyzed in two seasons using Atomic Absorption Spectrophotometer and Ultra-Violet/Visible Spectroscopy. Results were compared with World Health Organization Standard (WHO) for drinking water. Result indicates high concentrations with ranges: Mn 2+ (63.45 mg/L), Pb 2+ (11.42 mg/L), Cr 3+ (14.60 mg/L), Ni 2+ (1.260), Cd 2+ (15.67 mg/L), Ag + (6.06 mg/L), Hg 2+ (2.60 mg/L), As (4.13 mg/L), Se 2+ (2.68 mg/L), Zn 2+ (10.53 mg/L), Co 2+ (0.9 mg/L). These are above the WHO recommended standard for drinking water. Only Cu 2+ and Se 2+ recorded safe concentrations in 100% samples analyzed in both surface and groundwater in the rainy season. Percentage contamination shows Pb 2+ > Hg 2+ > As 2+ > Cd 2+ > Mn 2+ > Ag 2+ > Se 2+ > Ni 2+ > Cr 2+ >Cu 2+ especially in areas close to the active mines. Surface water resources recorded higher contamination. However, Pb 2+ , As, Hg 2+ , Se 2+ and Cd 2+ showed high percentage of contamination in groundwater samples. The Ameka and Mkpuma Akpatakpa mining areas recorded higher concentrations of the hydrogeochemical constituents than the Enyigba, Ameka and Amorie mining regions. Seasonal analysis shows a decreased concentration of chemical constituents in the rainy season relative to the dry season.