| This paper took Huai An section of 205 National Road in Jiangsu Province as the object of study. The samples in the surface soil and tree leaves of 5m, 10m, 20m, 85m forest belts and the non-forest belt road section were collected from both sides of main roads, and the contents of As (Al), Cr, Cu, Fe, Ni and Pb in soils and leaves were analyzed for estimating characteristic and sources of the heavy metal pollution. The distribution of heavy metal content in leaves of different type of forest belt and changing tendency of heavy metal in soil along with distance were compared. Based on these investigations, following conclusions were achieved:①T he content of As in 5m, 10m (east) and the non-forest belt road section surface soil, content of Cu in 20m (west), 85m (east) and the non-forest belt(west), content of Ni in the non-forest belt(west) went beyond the scope of background value of soil element in Jiangsu Province. The contents of Pb, Cr and Fe were under the background value and did not obviously cause soil pollution.②The contents of As, Cr, Cu, Fe, Ni and Pb in soil of east side of non-forest belt were higher than those of west side. The contents of As, Cr, Cu, Fe and Pb in soil of east side of 5m forest belt were higher than those of west side, but the content of Ni in west side was higher. Each detected element in soil of east side of 10m forest belt was higher than those of west., the content of Cu in soil of west side of 20m forest belt was higher than those of east. Other elements were higher in east.③The relevant analysis indicated that the relationship between heavy metal and distance was non-simple linear relationship. The heavy metal factorial analysis indicated that the heavy metal of roadside soil mainly came from the road pollution. The origin of Pb was more complex. It possibly came from both road pollution and soil.④Based on a evaluation criteria which was established by using the national average background value of soil element pulsing a fold of standard deviation, the result of evaluation of soil synthesis pollution index indicated that the soil of west side of non-forest belt was moderately polluted; The soil of both sides of 5m forest belt and east side of non-forest belt were mildly polluted; The soil pollution of east side of 10m forest belt was in an alert level, other experimental areas were relatively clean. The evaluation of single item pollution index indicated that As pollution was serious, It was seriously or moderately polluted in soil of both 5m forest belt and non-forest belt. The other elements have not caused the obvious soil pollution.⑤The relationship between soil heavy metal synthesis pollution index of east side of non-forest belt and distance was positive. And the relationship between soil heavy metal synthesis pollution index of 5m, 10m (east), non-forest belt (west) and the distance was negative. The soil synthesis pollution index of 10m (west), 20m forest belt was obviously declined in the tree coverage area and It displayed the trend of escalation in the behind of forest belt. The soil synthesis pollution index of 85m forest belt was slightly changed, the maximum value was 0.675, the minimum value was 0.635.⑥The value of soil synthesis pollution index among different types of forest belt in east side from low to high were: 20m<85m<10m<5m |
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