Pollution And Environmental Risk Of Heavy Metals In Surface Dust Of Taiyuan

This paper took the industrial city in northern-Taiyuan as the study area,33surface dusts in seven functional zones (Industrial zone, Commercial area, Economic development zone, Main road, Residential area, Campus, Park) were collected. The concentration of Cr, Cu, Ni, Pb, Mn was measured by AAS, then the spatial distribution and reasons were discussed, combined with statistical analysis methods, the possible sources of heavy metals in surface dust of Taiyuan were analyzed. On this basis, the pollution levels, potential ecological risk, human health risk assessment of heavy metals in surface dust were evaluated. Tessier five-step sequential extraction was used to extract the chemical forms of heavy metals, and the mobility of heavy metals was estimated. The human bioavailability for heavy metals was studied by SBET. The main conclusions were as follows:The content of Cr, Cu, Ni, Pb, Mn in surface dust of Taiyuan exceed the soil background value of Shanxi, a different degree of accumulation is presented. The spatial variability of heavy metals in different functional zones is obvious, the maximum value of Cr, Ni, Mn occur in the industrial zone, are1731.85,251.83,1238.53mg/Kg, respectively. The most polluted area of Cu is the economic development zone, the maximum value is684.24mg/Kg. Pearson correlation analysis combined with principal component analysis show that industrial emission is the main source of heavy metals in Taiyuan.The chemical form of Cr, Cu, Ni, Pb, Mn in surface dust of Taiyuan show that:the residual fraction of Cr, Ni, Mn have the highest percentage in the five forms, the organic fraction of Cu and the Fe-Mn oxidation of Pb are slightly higher than the relative residual proportion. The mobility for heavy metals in surface dust of Taiyuan is in order of: Pb>Mn>Ni>Cu>Cr. The biological activity of Pb is the largest, which has the strongest mobility. Geoaccumulaition pollution index was used to estimate the pollution level of heavy metals in surface dust from Taiyuan. The surface dust are polluted in a certain degree by the heavy metals except Mn and Ni in the seven functional zones. The queue of pollution level is:Cu>Pb>Cr>Ni>Mn. All the five metals cause a certain level pollution for the dust is found by the potential ecological risk index, the result of the pollution sequence is the same as the geoaccumulation pollution index.All the five metals in surface dust of Taiyuan cause a certain level ecological risk. Thereinto, Cu and Pb exist the highest ecological risk, Mn is the lowest. And all the functional zones reach a potential ecological risk level of middle-up.The results of health risk assessment are as follows:The non-carcinogenic risk of heavy metals is in the order of Cr>Pb>Mn>Cu;:=Ni, and the non-carcinogenic risk for the children is higher than the adults. The integrated index (HI) indicate that the non-carcinogenic risk is existed for the children in economic development zone and industrial zone. The carcinogenic risk of Cr, Ni are below the threshold, no carcinogenic risk is existed.The human bioavailability of the five heavy metals in surface dust of Taiyuan are all below50%, the order is:Pb>Mn>Cu>Ni>Cr. Mn and Ni have the lowest bioavailability in industrial zone, and other heavy metals are in economic development zone. The daily absorbed dose of heavy metals via intaking surface dust was analyzed. Mn has the highest daily absorbed dose, which is more than10times than other metals. And the daily absorbed dose of other metals is lower than10μg/d.