Abstract:

Heavy metals pollution of automobile particle matter is more and more serious with the development of vehicles industry and highway construction. And the forest belts along the road have been greatly emphasized on their functions of decreasing pollution. This article summarized the ecological influence of pollution of automobile particle matter, scope of heavy metal dispersion, screen effect of highway greenbelt and the use strategy of land along the highways. Three highways (Beijing-Shijiazhuang highway, Beijing-Tianjin-Tanggu highway, Airport highway) were used to study the characteristic of heavy metal dispersion and the relationship between traffic flows and heavy metal content. And the traffic flows of three highways are respectively 100 000, 59 000 and 80 000. The contents of Pb、Cd、Cu、Cr in soil and organs of trees(Populus tomentosa)along the highway were measured. The results showed that Pb was the main source of traffic tail gas pollution and its content decreased in different soil layers and tree organs with extends of the distance away from the highway. The content of Cu was also related with the distance away from the highway, but it was greatly influenced by the characteristic of the road and vehicles. There was little correlation between the contents and distributiong of Cd、Cr and forest belt width. The range of heavy metals dispersion was mainly within 80 m apart from the highway. And the heavy metal pollution made by tail gas of vehicles on the highway (50 000<average traffic flow per day<80 000) could be effectively decreased by 40～60 m poplar forest belt (height≥10 m). In addition, the arrangement strategy and width of protective forest along the highways were also comprehensively studied in this paper. According to the pollution grades of road and spatial differentiation of land near the road, the different managing strategy with different disturbance degree were carried out for different reach of the road. And the utilization strategy should be classified and aimed at maintain zone, natural zone and buffer zone respectively with the distance away from the highway. Some scientific suggestions on highway design and construction, pattern of agricultural production along highway and highway environmental protection were also provided.

Key words: highway, forest belt, tail gas of vehicles, heavy metals pollution, pollution controlling, arrangement strategy