| Interest in the levels of heavy metal contaminants associated with urban dust has risen in recent ten years. Urban dust includes street dust, regional dust, atmospheric dust. In this paper, the study targets are street dust and atmospheric dust. Street dust and atmospheric dust are 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., street dust and atmospheric dust themselves have accumulated a large amount of metals and have been identified as a significant pollution source in urban environment. Just as what has been found in many studies throughout the world, urban 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.Foreign scholars study more on heavy metals of urban dust, they have more systematic research on heavy metals in different functional areas, different forms and different sizes. By contrast, domestic scholars focus mainly on the research of contribution rate of dust to atmospheric dust particles and measures to prevent dust. A preliminary study on heavy metals in the street dust just begin in China, such as Xian and Shanghai, but still a blank in the northeastern region. Shenyang City is a typical old industrial base in northeast of China, also major nonferrous metal smelting and industrial processing base in China. It is significative to study the spatial distribution of metals on the typical characteristics of Shenyang City.Based on the sampling of 61 street dust, 54 atmospheric dust samples and the analysis of 2811 effective data, the paper studys the content and distribution character of Cd, Cu, Pb, Zn, Ca, Na, K and Mg in different sizes as well as the metal content difference of atmospheric dust in different functional areas and different time. These results can not only fill up the blank in the research of metal pollution in urban dust of Shenyang, but also provide reliable and scientific basis for the urban environmental pollution control, environmental quality assessment and city planning of Shenyang. The main conclusions of this study can be summed up as follows.(1) The average pH of street dust in Shenyang is 8.71 with the range between 7.92 and 10.02, street dust has obvious alkaline. Street dust particles are mainly below the size of 0.152 mm, this part is 42.59 percent of the total dust.(2) The average content of Cd, Cu, Pb, Zn, Ca, Na, K and Mg in street dust is 4.35 mg·kg-1, 81.33 mg·kg-1, 106.26 mg·kg-1, 334.47 mg·kg-1, 50755.00 mg·kg-1, 24415.78 mg·kg-1, 18711.02 mg·kg-1 and 16875.69 mg·kg-1 respectively, with the range between 2.29 and 15.04 mg·kg-1, 46.96 and 204.29 mg·kg-1, 62.76 and 509.48 mg·kg-1, 277.41 and 422.89 mg·kg-1, 30125.16 and 115677.60 mg·kg-1, 16000.54 and 34728.37 mg·kg-1, 14197.07 and 24691.76 mg·kg-1, 12498.90 and 19462.95 mg·kg-1, which is 127.18, 3.31, 4.80 and 5.67 times of the soil back ground values, 2.25, 2.87, 2.35 and 2.36 times of control. By using the method of geoaccumulation index to assess the heavy metal pollution in urban street dust of Shenyang, the results show: the range of Cd, Cu, Pb and Zn's geoaccumulation index is 3.25～5.97, 0.35～2.47, 0.92～3.94 and 1.65～2.26 respectively. The average value is 4.18, 1.14, 1.68 and 1.92. Cu, Pb and Zn are all above low to middle pollution level. Only Cd is at heavy pollution level.(3) The spatial distribution of each heavy metal in urban street dust of Shenyang has much difference and the partial pollution isserious. Especially Pb and Cu content values in Tiexi district are higher than others, the average value is 152.66 mg·kg-1 and 98.32 mg·kg-1 respectively. The values of heavy metal contents in Tiexi district is higher than those in other districts. It's associated with Tiexi district's industrial area characteristics. Although the industrial area has been relocated, there are also a large number of residues in this area. The Cd content in Dadong district is highest in five districts, and this should be related to automobile industry characteristics of eastern part. Zn and Mg distribute equably. Overall, Cu, Pb and Zn pollution levels in the west are higher than those in the east, while Cd, Ca, Na, K and Mg content values in the east are higher than those in the west in Shenyang City.(4) There are prominent correlation between Cd and Zn, Cu and Pb, Cu and Zn, Pb and Zn, Ca and Na, Ca and Mg, Na and K. In most of samples, these metals also increased synchronously. It shows that the probability of these metals from same sources of pollution is large.(5) There are three particle sizes in the experiment analysis, 125～100μm, 100～63μm and <63μm. The results show that: metal contents in these three particle sizes are close to each other. With the decrease of street dust's particle size, metal contents are higher and higher. This is because small particles have greater surface area, it is easier to adsorb metals.(6) The average content of Cd, Cu, Pb, Zn, Ca, Na, K and Mg in atmospheric dust is 3.36 mg·kg-1, 105.78 mg·kg-1, 138.72 mg·kg-1, 224.31 mg·kg-1, 74285.42 mg·kg-1, 18381.34 mg·kg-1, 27587.89 mg·kg-1, 18295.83 mg·kg-1 respectively, with the range between 1.80 and 6.65 mg·kg-1, 28.35 and 300.50 mg·kg-1, 44.55 and 767.00 mg·kg-1, 141.85 and 308.77 mg·kg-1, 10524.62 and 167537.50 mg·kg-1, 11707.50 and 25580.00 mg·kg-1, 11345.00 and 50010.00 mg·kg-1, 10152.50 and 22940.00 mg·kg-1, which is 127.18, 3.31, 4.80 and 5.67 times of the soil back ground values.By comparing dust's metal contents in different functional areas and different periods, We conclude the following results: the order of metal contents is industrial area> commercial area> street> cultural and educational area> park. most of metal contents in the heating period are higher than those in the non-heating period especially Pb and Ca. High contents of heavy metals in the heating period are closely related to burning of coal in winter in the northeastern region, and Ca, Na, K, Mg's high contents are because of using deicing chloride salts in winter. By using the method of geoaccumulation index to assess the heavy metal pollution in atmospheric dust of Shenyang, the results show: Cd, Cu, Pb and Zn's geoaccumulation index is 3.81, 1.52, 2.06 and 1.34 respectively. Cd is at low to heavy pollution level. Pb is at middle pollution level. Cu and Zn are at low to middle pollution level. Heavy metals'pollution level in street dust are close to those in atmospheric dust, and Cd's pollution level is still most heavy, so we should focus on Cd pollution in Shenyang City.
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