POLLUTION LOAD INDEX AND ENRICHMENT OF HEAVY METALS IN SOIL WITHIN THE VICINITY OF OSOGBO POWER STATION

Abstract

The extent of contamination of soil within the vicinity of Oshogbo electric power station with heavy metal (Zn, Co, Cd, Fe, Cr and Pb) was evaluated. Composite soil samples were collected in four clusters from thirteen different sampling points and analysis of heavy metal concentrations were performed on the soil samples using Atomic Absorption Spectrophotometer (AAS). Results of analysis revealed a wide variation in the concentrations of different heavy metals at various sampling stations. The maximum mean concentration of Zn, Co, Cd, Fe, Cr and Pb were 110.55 ± 0.70 mg/kg, 9.32 ± 0.28 mg/kg, 9.84 ± 0.35 mg/kg, 208.2 ± 0.35 mg/kg and 11.39 ± 0.22 mg/kg respectively, and obtained from soil samples from immediate vicinity of the power station. The mean heavy metal concentrations obtained from soil samples 400 meters from power station were far lower than those obtained at the immediate vicinity of power station. Pollution load index (PLI) ranged from 1.15 to 2.19, indicating high pollution status of the sampling stations. The range of calculated geo-accumulation (Igeo) index for Co, and Cd, were -1.69 to 2.26, and -1.37 to 5.12, indicating that the soils from most of the studied stations were extremely contaminated with both Co and Cd respectively. High calculated enrichment factor (EF) for Cd, Cr and Pb confirmed that soil contamination was as a result of anthropogenic source mainly from the power plant. Keywords: Enrichment factor, geoaccumulation index, pollution index, concentration, contamination factor.