HEAVY METAL POLLUTION OF SOILS ALONGSIDE ROADS OF CHONGMING ISLAND OF SHANGHAI CITY
WANG Chu CHEN Zhen-lou WANG Jing ZHOU Nai-sheng XU Shi-yuan (Department of Geography, East China Normal University, Shanghai 200062, China)
To assess heavy metal contamination induced by traffic at the vicinity of roads,a study of heavy metal levels in the soils and road dusts was carried out alongside two roads of different traffic intensity. 273 roadside soil and road dust samples were collected along the Chenhai road and Beiyan road of Chongming Island and the concentrations of heavy metals (Pb,Cd,Cu,Zn and Cr) were measured by atomic absorption spectrophotometry. The results showed that the average value of total soil Pb,Cd,Cu,Zn and Cr concentra- tions were 27.7,0. 279,25.8,91.8 and 77.6 mg/kg,respectively. Roadside soils were seriously polluted by Cd. The average value of total dust Pb, Cd, Cu, Zn and Cr concentrations were 51.2,0.49,48.9,209 and 97.0 mg/kg,respectively. Heavy metal concentrations of road dust were 2～4 times higher than the back- ground values of Shanghai soils. It is indicated that road dust was a potential source of heavy metal contam- ination in the roadside environment. And protection forest of the roads played an important role in heavy metal distribution in the cross section. All measured heavy metal concentrations in roadside soils of Beiyan road,which had sparse protection forest,decreased exponentially with the increase of distance from the road; the maximum heavy metal value appeared within the distance of 15 m from Beiyan road. However, heavy metal concentrations of roadside soils within the distance of 15 m from Chenhai road, which had dense protection forest,were rather low in the cross section. Heavy polluted roadside soils alongside Chen- hai road appeared in the distance between 20 m and 50 m from the road.