| There is an increasing attention on the study of black Carbon (BC) aerosol in climate change research. This paper introduce the theory of the Single Particle Soot Photometer(SP2), and present the observational results in two sites by using SP2. SP2 heats every BC particle and makes it burn using infrared laser beam continuously. Characteristics of each BC particle could be measured by the analysis of scattering signal and Laser Induced Incandescence(LII) signal. By the time delay between the two signals one can get the mixing state of BC particles. The method of SP2 is different from the traditional filter-based method, and it can provide more accurate information on single particle BC properties.SP2 had been used at Wuqing for a month in December 2009. The results shown that BC containing particles were 57.2% of the aerosol particles in the range of 50-500nm diameter. The average number concentration was 1504/cm~3, associated with ~8.2μg/m~3 mass concentration. BC was the main change of the concentration of aerosol particles, and 51.5% of BC were coated by thick material. In a case of windy day, the daily average number concentration was 215/cm~3,while the mass concentration was 1.2μg/m~3, and 40% of them were coated thickly. However in the case of serious polluted day, the daily average number concentration was 3169/cm~3,while the mass concentration was 17.2μg/m~3, and the ratio of BC thickly coated also increased to 79%. At the same time, there were more BC in the air than non-absorbing aerosol particles, and the change of number concentration become smaller.The results of observation at Zeppelin station in the Arctic during Aug and Sep in 2010 shown that BC particles were 5.5% of the aerosol particles in the range of 50-500 nm diameter. The average number concentration was 0.56/cm~3, while 84.3% of BC number concentrations were below 1/cm~3.The mass concentration was ~1.0 ng/m~3, and 71.1% of them were coated thickly.
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