Quantifying vehicular heavy metal deposits on roadside soil and vegetation along Akure-Ilesa express road, South-Western Nigeria

Vehicular emission is one of the major sources of heavy metal deposition on roadside vegetation and soil. This is influence by the degree of traffic congestions on the road. The heavy metals can affect plants negatively with health hazards to humans and animals in the food chain. This study investigated the quantity of vehicular heavy metal deposits on vegetation and soil along Akure-Ilesa road. Plant and soil samples were collected at 10 km intervals along Akure-Ilesa road, digested using Aqua regia methods and metals; Cd, Pb, Cr, Zn and Cu contents determined with Atomic Absorption Spectrophotometer (AAS). Data were analysed with ANOVA and t-test and differences tested at p≤0.05. The study revealed that; 0.021 – 0.320, 0.110 – 0.301, 0.092 – 0.170, 0.055 – 0.113 and 0.061 – 1.280 mg/kg; and 0.068 – 0.421, 0.110 – 0.410, 0.100 – 0.181, 0.008 – 0.141, and 0.267 – 0.411 mg/kg of Pb, Cr, Cd, Cu, and Zn were found in plants and soils respectively. It was concluded that vehicular emissions contributed to the heavy metal load of the roadside vegetation and soil.