Conclusion
Heavy metals contamination by mining activities at Enyigba Pb mine area was investigated. Heavy metals concentration in the water samples signifies some degree of contamination. Pb, Cr, and Fe exceeded accepted limit for drinking water standard. Soil samples in the in the surrounding areas also showed higher concentration of heavy metals (Se,Cd,Cu,Zn,Hg and Pb) in comparison to the control sample. The soil pH is acidic and is one of the major factors affecting mobility/solubility of metals in soil environment. The soils have the potential to retain further additional heavy metals loads in such pH conditions. This heavy metals have tendency to bio-magnify and induce long-term adverse impact on the ecosystem in terms of biochemical and toxicological effect on human being.
The lead-zinc mining activities in Enyigba are contaminating the surrounding environment by increasing the acidity and heavy metals content of soils, sediments and surface and ground water bodies. The greatest threat posed by mining in Enyigba is the uncontrolled release of acid mine drainage from abandoned waste rocks and mine-pits.
During operation of the mines, sub-surface areas were kept dry by pumping out ground water that was constantly seeping in. After mining stopped, the mine-pits flooded and overflowed, The seepage from these mine pits is acidic and contains hazardous substances .once such water with high concentration of sulphuric acid and dissolved metals migrates away from the mining area, they can contaminate surface and ground water resources . If the acid water runs into a natural lake significant damage may result because the acid water is extremely toxic to plants and animals.
