DETERMINATION OF THE PHYSICOCHEMICAL PROPERTIES AND SOME HEAVY METALS IN SOILS AROUND SELECTED AUTOMOBILE WORKSHOPS IN MINNA, NIGERIA

Abstract

Automobile workshops generate wastes containing hazardous chemicals. Heavy metals present in these workshops are the major pollutants capable of seeping into the soil and further spreading to other nearby environments during floods. Three different sampling points (A, B and C) were mapped out at a distance of 20 meters apart around each automobile workshop: Railway station (RW), Sabon Gari (SBG) and Mypa School (MY). The soil samples were pretreated and digested with HNO3 and HClO4 (3:1). The heavy metals (Zn, Mn, Pb, Cd and Cu) concentrations were determined using the multiple plasma atomic emission spectrophotometer (MP AES). The physicochemical properties (pH, electrical conductivity, organic carbon (OC), organic matter (OM), exchangeable cations, soil texture, cation exchange capacity (CEC), total exchangeable bases (TEB) and percentage clay, silt and sand) were determined using standard methods of analysis. The concentrations of Pb at points A, B and C of MY (2.10±0.01, 9.50±0.05 and 2.90±0.03 mg/kg) were lower than 35.10±0.20, 37.20±0.21 and 46.50±0.54 mg/kg at RW and 25.80±0.29, 64.80±0.75 and 75.60±0.87 mg/kg at SBG. Zinc concentration was in the order MY < RW < SBG. Cadmium concentrations were 3.20±0.20, 3.70±0.02 and 3.40±0.02 mg/kg at points A, B and C in RW, 3.90±0.02, 2.80±0.05 and 3.50±0.02 mg/kg in MY soil. The high concentrations of cadmium in soils at RW and MY are indication of considerable contamination and the soils at MY and RW are not suitable for planting crops but require remediation action.