Wu et al. [2009] measured the mean BC concentration 8.4 mgm−3 for 2004–2007 in Guangzhou, which was decreasing by 1.0 mgm−3 per year. Lou et al. [2005] measured the mean Black Carbon concentration 8.8 mgm−3 in summer and 11.4 mgm−3 in winter in Beijing. Deng et al. [2008] has found that the absorbing aerosol particles (Black Carbon) played an important role in the reduction of visibility in the Pearl River Delta, about 20% of the aerosol extinction, and developed an adaptive function of visibility versus aerosol extinction coefficient.