plant pollution from lead produced by automobile exhaust system near 'certain high ways of iran

plants polluted with pb produced by automobiles along the roads and highways have extensively been reported all over the world. it is the most important source of pollution in the environment. this research was carried out to determine the polluting degree of plants along the highways such as: rasht-anzaly, kelachay-ramsar, tehran-karaj, and isfahan-tehran. at each arbitrary point, a transect 100 meters long perpendicular to the highway was selected for sampling. along each transect, plants were sampled at 15 em above the ground, in different distances from the highway. samples were transported to the laboratory and analyzed by a standard method. the average concentration of total pb determined in anzali, ramsar, karaj and delijan(east and west of the road) areas respectively were 114.5, 58.3, 260.2, 75.1 and 80.2 microgram per gram dry plant weight. total pb content in plants along the roads were high and exponentially decreasing with distance from the roadside . pb concentration in plants were higher than threshold of standard, so the risk of entraing of this poisonous element in nutrition system along the roads is very considerable the plants were polluted from medium degree up to a very high degree. the rate of pollution in plant samples is very high in karaj area, high in anzali area, and medium in ramsar and delijan areas. plant pollution was directly related to the traffic volume in road