Assessment of Impact and Safety Status of Remediation of Lead Contaminated Soil using Excavation Method: A Case Study of Olodo, Ibadan, Southwestern Nigeria

Abstract

This study aimed to assess the impact and safety status of the excavated waste site of a lead-acid accumulator factory. Soil samples (3 each) were collected from the five pits of depth 1 m each at four angles and one at the centre of the site at interval of 0.5 m. Five soil samples were also collected from five different locations outside the site as a control. All the samples were analysed after pulverisation and digestion using AAS analytical instrument for major, trace and heavy metals such as, Ca, Mg, K, Na, Mn, Cu, Fe, Zn, Co, Cr, Cd, Pb and Ni. Ten water samples were collected, four from shallow hand dug well and six from surface water around the site, and analysed for major ions and trace metals. Using Hakanson (1980) approach, contamination factor of Mn, Zn, Cr and Ni showed low to considerable contamination in A and C-horizon but low contamination factor in B-horizon. This is probably due to the fact that B-horizon could be more porous which served as medium for leaching into C-horizon. Fe, Cu, Cd, Co and Pb revealed considerable contamination factor to very high contamination factor which increase from A-horizon (surface soil) through B to C-horizon (subsurface soil). Degree of contamination show the soil is highly contaminated from top soil through B to C-horizon. Surface water revealed higher concentration of Pb, Cd and Fe in samples from the downstream of the dumpsite which could be due to wash-off by erosion into the rivers.