Investigations on Soil Contamination by Toxic Metals within the Vicinities of Bodija Market in Ibadan, Nigeria

This study was carried out to investigate soil contamination with Pb, Cu, Zn, Ni, and Cd from Bodija market. Fifty-six soil samples were randomly collected from 7 sections of the market, namely: sawmill, foodstuff, refuse dumpsite, slaughterhouse, slabs, petrol station, railway quarters, and carpark, and 8 samples from a control site, making a total of 64 soil samples. The soils were collected at 0 – 15 cm and 15 – 30 cm depths, and the pH, organic matter, particle size, as well as the metal leaching were determined using standard methods. The metal levels were determined using atomic absorption spectrophotometry. The mean values of pH and organic matter were 6.87 and 3.24% for the study area and 4.93 and 2.54% for the control. The mean particle size analysis (%) in this study, with control in brackets, showed clay, silt, and sand as 6.84 (15.8), 7.83 (19.6), and 85.3 (64.6), respectively. Metal concentration (mg/kg) ranges with median in brackets were: Pb: 3.25 – 154 (68.1), Cu: BDL – 478 (13.6), Ni: 7 – 75.8 (19.6), Zn: 0.32 – 128 (43.9), and Cd: 0.25 – 4.40 (0.40). The higher pH and organic matter values suggest influence from carbonaceous and ammonium-containing waste in soils from the market. The metal levels for all metals were within the permissible limits set by FAO except Cu (478 mg/kg) and Cd (4.40 mg/kg) in samples collected from railway quarters and slaughterhouse slabs, respectively. The soils pose little or no harm to human health and the environment, but the need for periodic environmental monitoring of soils is important.