The Physicochemical Characteristics And Fractal Analysis Of PM10 And PM2.5 In The Atmosphere Around The Campus Of Beijing Forestry University

At present, the serious pollution of Inhalable particulates, especially fine particulates in the atmosphere of Beijing have becoming the bottle-neck of sustainable improvement of air environmental quality. In this study, PM10 and PM2.5 samples were collected in five sampling positions of Beijing Forestry University in 2007 and 2008. Morphology and chemical compositions of individual particles were analyzed with high resolution Scanning Electron Microscopy, images analysis and Energy Dispersive X-ray Spectrometry. Soot aggregates, mineral particles, biologic particles and coal fly ash were found in the PM10 and PM2.5 samples of Beijing Forestry University. Soot aggregates, coal fly ash and mineral particles were the main component of PM10 and PM2.5 samples collected in Beijing Forestry University. This indicated that the resources of PM10 and PM2.5were vehicle, coal dust, raising dust and cement dust. X-ray energy spectrum showed that the composition of mineral particles was mainly Si, Al, Ca, Fe and other elements. Cluster and triangle plot analysis showed that many mineral particles were internally mixtures of clay and other mineral such as CaCO3. The result of cluster analysis showed that mineral particulate mainly consists of silicate, but it also contains a lot of calcium salts and oxides. The frequency-size distributions of soot aggregates, coal fly ash particles and mineral particles revealed by the image analysis peak at 0.30~0.50μm, 0.20~0.40μm, 0.40~0.60μm in PM10 and 0.20~0.50μm, 0.20~0.30μm,0.40~0.60μm in PM2.5 respectively. Morphology of FESEM images and fractal dimension calculation indicated that coal fly ash is not fractal, but soot aggregates and mineral particles are fractals. The 1-D fractal dimensions of mineral particles are less than those of soot aggregates, which shows that the boundary of soot aggregates is more irregular. However, the much less 2-D fractal dimensions for soot aggregates than mineral particles reveal their loose structure. The sources analysis of PM10 and PM2.5 showed that the pollution of open-air barbecue, coal combustion in winter and motor vehicle exhaust emission should be controlled in Beijing Forestry University at present.