Microscopic Characteristics And Source Of PM_2.5 In Tipical Acid-Rain Cities,guizhou

The Fine Particle(PM_2.5) is very bad for human health and the environment they lived in, and it is also the main reason for brown haze. Therefore, air pollution already becomes important environmental problems in China. Experts at home and abroad reveal that PM_2.5 can decreases visibility, deteriorates ecology and environment, and harms human health, so it is significant to study physicochemical properties and sources. Characteristic of atmospheric particulate matter pollution is closely related with its physical and chemical properties. Microscopic properties, the number of percentage, volume fraction and size distribution of different types of individual particles were investigated in six typical acid-rain cities, Guizhou. High resolution Field Emission Scanning Electron Microscopy（FESEM） and Image Analysis（IA）have been used. The results showed that,（1）soot and soot aggregates, irregular mineral particles, secondary mineral particles with regular shape and fly ash are the main components in PM_2.5 samples in different season. Unknown particle is found in several cities.（2）The maximum and minimum number percentage of soot and soot aggregates in spring are successively 93.34%, 62.03%.The number in summer are 91.51%,62.03%respectively. In autumn are 90.77%, 80.62 %, and in winter are 94.20, 88.18 %. These data indicate that fossil fuel combustion, in particular coal combustion and vehicle exhaust are the major sources of PM_2.5 in Guizhou.（3）In general, the number percentages of different cities reveal that the ratio of irregular mineral particles is higher than that of regular mineral particles, and the ratio of regular mineral particles is higher than fly ash.（4） The volume percentages of different cities universally are the same, soot and soot aggregates > irregular mineral particles > regular mineral particles> fly ash.（5）In the PM_2.5 samples, the size of soot and soot aggregates in four seasons are mainly around 0.1⁰.4μm.The size of fly ash are mainly around 0.1⁰.6μm. For mineral particles with regular shape in different season, the size are mainly around0.3⁰.7μm and 1.0².5μm.The size of mineral particles with irregular shape was around 0.3⁰.6μm, 0.7⁰.8μm, and 1.0².5μm.（6）The volume-size distribution of the main kinds particulates of PM_2.5 in study area indicate that the volume of four main particle are most distributing in 1.0².5μm and >2.5μm except for several particles in spring and summer. It is as a the result that the volume of particulates whose aerodynamic diameter are within 1.0².5μm and >2.5μm is bigger than small size particulates.