Heavy Metal Contents of Soils and Plants as Influenced By Leached Ash Refuse From Black Soap-Making at Ikere-Ekiti, Nigeria

The effects of ash refuse pile from a black soap-making facility were studied on the surface (0-15 cm) layer of soils and commonest plants at Ori-Ebu, Afao Quarter, Ikere-Ekiti in Nigeria. Soil and plant samples were collected at 0, 15, 30, 60, 75, 105 and 150 m from the ash refuse pile and analyzed for cadmium (Cd), cobalt (Co), chromium (Cr), lead (Pb) and nickel (Ni). The prominent plant species were Physalis angulatus at 0 m, Starchytapheta jamaicensisat 15 m, Starchytapheta cayenensis at 30 m, Asystasia gagentica at 60, 75 and 105 m and Sida scrabida at 150 m. Co, Cd, Pb and Ni contents were lower in the site than the control. Co, Pb and Cd increased with distance from the ash refuse pile while Cr showed an accumulation at 60 m. Heavy metal concentration in plants exceeded the control except Ni and Co at 150 m. Accumulative factors used to access the level of pollution were contamination factor, pollution load index and transfer factor. Co, Cd, Pb and Ni contamination was low (CF<1) while the site has been moderately contaminated with Cr CF=1.53-3.10). The pollution load index was low (PLI= 0.43-0.96) such that the site was not contaminated by the heavy metals. The transfer factors at 1.02, 1.1, 1.14, 2.54 and 29.59 for Cd, Pb, Ni, Co and Cr, respectively indicate high levels of heavy metal bio-accumulation which can have implications for livestock and human health through the food chain.