Assessing highway-related metal pollution using surface soil and tree bark as indicators

Abstract Nigerian highway-related metal pollution was assessed using surface soil and tree bark as indicators. Metal concentrations were analyzed using an energy dispersive X-ray fluorescence spectrophotometer. The concentrations of potentially toxic metals (Co, Ni, Cu, Zn, and As) were approximately 1–2 orders of magnitude lower in the tree bark relative to surface soil, and cross-plot analysis (R 2 = 0.419) confirmed that tree bark had limited uptake for all the detected elements, suggesting that the observed concentrations in the tree bark may mostly reflect aerial pollution. Contamination factor, geo-accumulation, and other indices confirmed Ti, V, Mn, Ni, Cu, Zn, Rb, and Sr impacts to surface soil; high traffic volume and common use of poorly maintained second-hand vehicles are likely sources. Exposure to the metals via ingestion, inhalation, or dermal contact might pose health threats. Possible remediation schemes should be adopted to clean up these metals in order to ensure a sustainable environment.