Soil contamination beneath asphalt roads by polynuclear aromatic hydrocarbons, zinc, lead and cadmium

Abstract

The contamination of soil by 16 PAH and heavy metals beneath and alongside six asphalt roads in the city of Dortmund (FRG) was the object of a comprehensive investigation. Beside the roads concentrations of 6.6–9.8 ppm polycyclic aromatic hydrocarbons (PAH), 0.26–0.45 ppm benzo[ a]pyrene, 58–330 ppm zinc, 48–130 ppm lead and 0.6–1.4 ppm cadmium were found. These concentrations are equal to the ‘natural’ background of elements availability in the city of Dortmund. Soil contamination by PAH and benzo[ a]pyrene beneath the road surface is only equal to 26% and 30% of the contamination beside the road at the same soil depth. The soil contamination by zinc, lead and cadmium beneath the road surface is only equal to 36%, 43% and 78%, respectively, of the soil contamination beside the road. It is recommended to block, demolish and renaturate roads for the restoration of relatively less contaminated biotops in nature reserves.