Study On The Heavy Metal Pollution In Urban Street Dust Of Shanghai

Interest in the levels of heavy metal contaminants associated with Urban Street Dust has risen in recent ten years. Compared with urban soil and atmospheric particles, urban street dust is characterized as an environmental medium composed of complex substance and originating from multi-sources. Influenced by the human activities including traffic transportation, industrial production and city construction et al., urban street dust itself has accumulated a large amount of heavy metals and has been identified as a significant pollution source in urban environment. Just as what has been found in many studies throughout the world, urban street dust not only holds a threat to human health due to its elevated heavy metal concentration, but also provides considerable loadings of heavy metals to the water bodies of urban rivers by storm water runoff. It has significantly realistic and scientific meaning to study heavy metal pollution in urban street dust.This dissertation is supported by the National Nature Science Key Foundation: Environmental Evolution of Water & Land Resources and Its Control in Changjiang Delta (No. 49831070) and Biogeochemical Cycling of Pollutants in Complex Environments of Tidal Flats in the Yangtze Estuary (No. 40131020) respectively. Based on the sampling of 394 street dust samples and the analysis of 3646 effective data, the content and distribution character of heavy metals as well as their speciation and bioavailability in urban street dust of Shanghai are mainly studied, the pollution sources of the heavy metals are also discussed. These results can not only fill up the blank in the research of heavy metal pollution in urban street dust of Shanghai, but also provide reliable and scientific basis for the urban environmental pollution control, environmental quality assessment and city planning of Shanghai.The main conclusions of this study can be summed up as follows.1. The physical and chemical characteristic of the urban street dust in Shanghai is unique: the average pH is 9.52 with the range between 7.86 and 12.45; the average content of organic matter is 6.3%, with the range between 1.3% and 14.7%; the average and median grain size of the urban street dust are 163.7um and 136.3um respectively, mostly with double-apices or multi-apices non-normal distribution.2. The average content of Cr, Cu, Ni, Pb and Zn in street dust of urban area is 105, 152, 65, 196 and 584 mg/kg respectively, which is 1.4, 5.4, 2.1, 7.9 and 6.9 times of the soil background values. The average content of Cr, Cu, Ni, Pb and Zn instreet dust of the suburban towns' centers is 110, 253, 100, 237, 721 mg/kg respectively, which is 1.5, 8.9, 3.1, 9.3 and 8.4 times of the soil background values.3. The spatial distribution of each heavy metal in urban street dust of Shanghai has much difference and the partial pollution is serious. Heavy metal pollution of Cu, Pb and Zn are serious in the urban area especially within the inner ring, and the pollution centers locate mainly in the commercial area and major roads; the heavy metal pollution of Cr and Ni are relatively less serious with the pollution centers situated mainly near the outer ring and the Lu Jia-zui financial and commercial area (near the inner ring). As for the suburban towns, the heavy metal content in the street dust of commercial or residential area in town's center are obviously higher than that in town-grade (highway) road; the heavy metal content in rural area of suburban towns are lowest.4. The content of Cd, Cu, Pb, Zn, Fe and Mn in street dust of suburban towns shows no significant seasonal changes, and only the seasonal changes of Cr and Ni are obvious, showing higher concentration in summer and lower concentration in spring. The content of Cr in summer is 1.9-3.4 times of that in spring, and the content of Ni in summer is 1.9-3.8 times of that in spring.5. Through the methods of the correlative analysis and principal component analysis of the heavy metals and organic matter in urban street dust of Shanghai, the pollution sources of the heavy metal are analyzed pr...