Lead-Polluted Soil along Some Iranian Highways

Soil as the third major component of our environment is exposed to different kinds of pollution. Lead has been recognized as a factor in environmental pollution. Pollution of soil and plants along the highways and roads by Pb from automobile exhaust gases has extensively been reported as the most important pollutant source in the environment. This research was carried out to determine the degree of soil pollution along the following highways: Rasht-Anzaly (Anzaly area), Kelachay-Ramsar (Ramsar area), Tehran-Karaj (Karaj area) and Isfahan-Tehran (Delijan area). In each location a transect of 100 meters long, perpendicular to the highway axis, was selected for sampling. Soil samples at different depths were taken from different distances from the highway and analysed for some physical and chemical characteristics and total Ph content by 5M HNO3 extraction. Results indicated that the total Pb content of soil decreased exponentially with distance from the roadside. Total Pb content of soil decreased sharply with depth in all highways except in one area indicating that Pb was retained in the surface soil and that its movement down to the deep soil was slow. Total Pb content of soils was highly and directly related to the traffic volume.