By using the appropriate value of specific attenuation cross section proportional to Black Carbon mass concentration [Petzold et al., 1997], the black carbon content of aerosol deposit on the filter can be determined at each time base cycle using the initial and final attenuations. Before the campaign, the attenuation cross section used in the Aethalometer was adjusted to get the greatest accuracy required for the Tongyu site using the method of comparison between Aethalometer Black Carbon data and thermal optical analysis elemental carbon (EC) data, which was described in detail by Cheng et al. [2006].