Study On The Source Apportionment And Physicochemical Characteristics Of Foliar Dust On Urban Plants

Urban plants play an important role in reducing particulate pollution, and have a good purification effect to airborne particulate matter. The dust removal ability and the ecological effect were appraised, based on the determination the quantity of the removal dust, but the research on the basic physicochemical characteristics of foliar dust were quite lack, and was rarely reported in China. In this article the content, temporal and spatial variance and potential ecological risk of trace metals in the foliar dust of urban plants in Xinzhuang cloverleaf junction,Chalukou,Fibre new village,Gulou center square and Mingxiao mausoleum were studied, the sources of the dust were discussed by factor analyses. These results can indicate the atmospheric dust pollution condition. The distribution character and temporal variance of foliar dust are mainly studied by Rise2002 laser particle size analyzer, the results could provide a more scientific basis for the city dust contamination control as well as the selection and protection of the urban trees, but also provide a new approaches to the research on the relationship on city plant and the environmental pollution, which has significantly realistic and scientific meaning. The main conclusions of this study can be summed up as follows:(1)The element analysis of foliar dust indicated that, the contents of Pb and Cu in foliar dust between Photinia davidoniae, Fatsia japonica, Lorpetalum chinense, Buxus microphylla, Ligustrun quihoui have significantly difference, but there is no significantly difference on other element. Element content of each month analysis indicated that, the content of element in foliar dust are changed greatly in September and October, which is generally higher in September, but in October relative is lower. Besides Pb, the content of other element increases from April to in June. The heavy metal contents in Town center Gulou square and Xinzhuang cloverleaf junction are higher, Pb and Cu pollution is most serious. Mingxiao mausoleum taken as most important scenery traveling area in Nanjing, also has caused the partial heavy metals element pollution, due to development operation.(2)The Index of Geoaccumulation indicated that, the foliar dust on urban plants in typical area of Nanjing is generally polluted in different degree by As, Cr, Cu, Pb, Zn, Ti, Pb and Zn pollution is most serious, which has already achieved the moderate pollution level. Potential ecological risk assessment indicated that, the potential ecological risks of foliar dust on urban plant in five typical regions have all reached the average risk lever, the social various departments should take particular consideration.(3)The grain size distribution of the foliar dust obeys the normal distribution with single-apices. The conifer mainly removals the fine particles, and the broad-leaf tree primarily removals the fine particles, but also removal large particles. The size of foliar dust mainly concentrates in 10~50μm, the majority achieves above 70%. The grain size characteristic of the dust deposited on Photinia davidoniae shows no significant changes in each month, but the Fatsia japonica changes quite obviously in each month, which is similar with the heavy metal change of foliar dust.(4)The traffic dust and the city building materials dust is main source of the foliar dust on the urban plants nearby the Xinzhuang cloverleaf junction, the contribution rates of these two kind of dust source has achieved 46.122%. The contribution rate of the natural soil dust source to total source is 21.237%. The industry dust is smallest. The traffic dust pollution has become "the main source" of the city air pollution.