Lead, cadmium, nickel and zinc concentrations in soil and vegetation associated with highways of different traffic densities
Soil and vegetation was collected along four highways of different traffic volumes, at varying distances from the road, and at two control areas. Four sampling periods were conducted throughout the course of a year from August, 1976 to June, 1977. Soil and vegetation samples were tested for concentrations of lead, cadmium, nickel, and zinc. There were general declines in the concentrations of lead, cadmium, nickel, and zinc as proximity to the highway decreased. These declines were significant (P < 0.05) along the highways of greater traffic density. Lead and zinc levels in roadside soil and vegetation exhibited a general decrease with decreasing traffic density. There was not a strong relationship between the levels of cadmium and nickel in soil and vegetation and traffic volume. There was a seasonal pattern to the levels of lead, nickel, and zinc in roadside vegetation, with plants from Period 3 (Feb/Mar) exhibiting the highest levels.