Accumulation Of Heavy Metals In Azadiractha Indica From Akungba-Akoko, Nigeria

Heavy metals from automobile sources in environments with dense road traffic may pose serious toxicological risks to human health. As a preliminary step towards risk assessment, the impact of traffic density on the accumulation of heavy metals in Azadiractha indica from Akungba-Akoko, a University town in South West, Nigeria, was investigated. Samples of soil and the vegetative parts (root, stem, leaf) of A. Indica were collected at different sites with varying traffic densities. The samples were digested in acids and analyzed for Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn, using a flame atomic absorption spectrometer. Results obtained show distinct variations in metal concentrations across the sites and accumulation was highest in the soil and lowest in the stem. The relatively higher concentrations of Cd, Cu, Pb, and Zn exhibited by samples collected within the vicinity of the highway suggest an important anthropogenic source. Conversely, the roughly similar contents of Co, Cr, Fe, and Mn in the investigated samples at all sites, regardless of the traffic density or distance from the roadside, are apparent of a natural origin. Despite the fact that the levels of heavy metals (more importantly Cd and Pb) in the vegetative parts were generally within normal literature values, the stem having the lowest accumulation of metals would probably pose less health hazards to the consumers. Given the results of this work and similar ones, it is imperative to monitor regularly the trace/heavy metal contents of roadside ecosystems in high-traffic areas.