EVALUATION OF THE PHYSICO-CHEMICAL COMPOSITION OF SOIL AT ELECTRONICS REPAIR WORKSHOPS IN BENIN, NIGERIA.

Abstract

Soil samples were collected using grid method from several electronic repair workshops in Benin City, a control (TS) which was from a site with no electronic repair activity and a DTS thirty meters away from the workshops at a depth of 0-15cm. The physiochemical properties were carried out using standard methods. Heavy metals were determined using the Atomic Absorption Spectrophotometer (AAS), while the sequential extraction was carried out using the European community Bureau of Reference (BCR) method. The results of the physiochemical properties are as follows; 5.9 to 6.5 for pH, 150±0.71 to 342±1.34 µs/cm for EC, 2.1±0.29 to 6.9±0.87 for O.M, 6.3±0.35 to 14.2±0.35 mg/kg for TOC, 157.6±0.44 to 217.9±0.45 mg/kg for CEC, 08.3±0.50 to 13.3±1.93 mg/kg for SO42-, 08.5±1.30 to 16.1±2.00 mg/kg for NO3-, and 7.7±1.41 - 14.7±2.10 mg/kg for PO43-. The concentration for Fe, Pb, Cd, Ni, Zn and Cu are respectively; 321.3 to 514.3 mg/kg, 1.78 to 6.17 mg/kg, 0.59 to 1.05 mg/kg, 6.4 to 23.12 mg/kg, 35.81 to 41.38 mg/kg and 28.88 to 44.35 mg/kg. From the results, the metals concentrations were higher in soils from the electronic repair work shops (TS) compared to those soil samples that were 30m away from the workshops (DTS). The results of the fractionation revealed that Fe, Zn, Cd and Ni were mainly in residual and Fe-Mn oxide fraction while Cu and Pb were in residual and organic bound fraction. The enrichment factors of metals in all the sites range from no enrichment to very severe enrichment. Mobility factor in all the sites were low ranging from 3.13-16.48, indicating generally low availability as well as mobility. Environmental risk factors showed that these metals pose potential threat to the environment. Contamination factor of all metals except Cd, in all the sites, exceeded unity indicating that the soils are clearly contaminated with these metals. Continuous monitoring is essential as these sites are potential sources of these metals.