The examination for pollution of the soils due to highways and traffic

In the developing provinces of our country, the traffic jam and the number of vehicles gradually increased over day, which is related to the population growth. this situation could be identified as the socio-economic development. however, it led to negative effects on soil-water-air. highways are important and necessary engineering structures in the cities, which connect different cities and have an important effect on the socio-economic development and other areas. today, because of increasing highway transport, the rapid urbanization and higher number of vehicles, heavy metal pollution of traffic become an important issue. for that reason, in these places soil pollution level is an important environmental problem, as it is difficult to remove heavy metals from the soil. soils are close to the highways, leading to higher level of pollution due to heavy metals. this study examines previous researches on the pollution of lands, sources and distribution of pollutants which are located close to the highways.