Integrated assessment of heavy metal (Pb, Zn, Cd) highway pollution: bioaccumulation in soil, Graminaceae and land snails

To assess the contamination induced by traffic at the vicinity of a highway (A31, France), several complementary studies were carried out on two sites, with different profiles and traffic intensity. Concentrations of zinc, lead and cadmium were measured by atomic absorption spectrophotometry in deposits, roadside soil and autochthonous plants (Graminaceae) gathered at the vicinity of the highway (1-320 m), and in the viscera of snails Helix aspersa, transferred as sentinel in the sites. According to the results obtained for different compartments, the highway induces a contamination on the surrounding environment, up to 320 m, but with the maximum contamination observed between 5 and 20 m: the concentrations measured in plants at the vicinity of the highway were 2.1 mg Pb kg(-1) DW, 0.06 mg Cd kg(-1) DW, 62 mg Zn kg(-1) DW and the concentrations measured in snails were 21.3 mg Pb kg(-1) DW, 5.7 mg Cd kg(-1) DW, 510.8 mg Zn kg(-1) DW. The levels measured decreased with increasing distance from the highway. Results of the three metals studied indicated that lead seems to be the best metal to evaluate road transport contamination.