Assessment of Automobile-Derived Heavy Metal Contamination in Roadside Soils Along Major Highways in Benin City, Nigeria.

This study assessed automobile-derived heavy metal contamination in roadside soils along major highways in Benin City to determine the concentration, spatial distribution, and environmental implications of selected heavy metals associated with vehicular activities. Twenty-one roadside soil samples were collected from seven major road corridors: Benin-Auchi Road, Benin-Lagos Road, Benin-Asaba Road, Benin Bypass Road, Benin-Warri Road, Boundary Road, and Etete Road during morning, afternoon, and evening periods. Laboratory analyses were carried out using Atomic Absorption Spectrophotometry (AAS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to determine concentrations of vanadium (V), lead (Pb), nickel (Ni), cadmium (Cd), zinc (Zn), manganese (Mn), iron (Fe), and chromium (Cr). Results showed that vanadium recorded the lowest concentration, ranging from 0.187–0.365 mg/kg, while zinc had the highest concentration, ranging from 308.6–636.5 mg/kg. Lead concentrations ranged from 20.68–40.59 mg/kg and exceeded the permissible limit of 10 mg/kg in all sampled locations. Cadmium and chromium concentrations also exceeded recommended environmental standards across the study area. Benin-Asaba Road recorded the highest concentrations of most heavy metals, especially during the evening period, indicating the influence of traffic density and vehicular emissions. Heavy Metal Pollution Index analysis revealed severe contamination levels, with cadmium and lead contributing the highest pollution values. The study concludes that roadside soils in Benin City are significantly contaminated by traffic-related heavy metals, posing ecological and public health risks. Regular environmental monitoring and stricter vehicular emission control measures are recommended.