Impact of heavy metals dispersion on water supplies around Oshiri and Ishiagu mine districts of Southern Benue Trough, Nigeria

Abstract

The study area is underlain by igneous intrusives and shales of the Asu River Group (Albian) in the southern Benue Trough, Nigeria. The massive mining operations in the Oshiri–Ishiagu mining axis have necessitated investigation of effects of mining works on water resources in the adjoining areas. Assessment of water resources around the study area was carried out to ascertain concentrations of trace elements/heavy metals using atomic absorption spectrophotometer. Results revealed some chemical pollutants with ranges of the concentration values (in mg/l) as thus: Cd (0.18–4.37), Pb (0.06–10.11), Zn (0.13–7.11), Ni (0.02–1.21), Mn (0.04–1.16), Fe (0.03–2.04) and Cr (0.02–0.48) in surface water regime, as well as Cd (0.02–2.00), Pb (0.16–3.18), Zn (0.13–5.16), Ni (0.01–1.54), Mn (0.01–2.17), Fe (0.01–2.50) and Cr (0.01–0.28) in groundwater system. Except Mn and Ni which showed higher contamination in groundwater than in the surface water representative samples, other pollutants exhibited higher amount of contamination and metal pollution indices in surface water resources. Principal component analysis showed that pollution of water resources is controlled by mining of Pb–Zn loads as indicated in principal component (PC1) through loading of Pb, Zn and Fe as eigen values. Excess loading of SO42− in PC2 and PC3 signified that ions were released by dissolution process via breaking down (weathering) of the sulfide-associated ore. Dispersion of the ionic plumes was meteorologically aided, possibly by run-off and leaching; hence, the eigen of HCO3 at − 0.49 in PC4. Strong association of these elements in Pearson correlation confirmed the anthropogenic-induced dissolutions and geogenic-aggravated dispersions. So, deterioration of water resources by mine drainage hampers potable water supply across the studied areas and may have affected the adjacent regions.