4Cao J J, Lee S C, Ho K L et aL Characteristics of carbonaceous aerosol in Pearl River Delta Region, China during 2001 winter period[J]. Atmos Environ, 2003, 37(11): 1451-1450.
5Wang Y, Zhuang G S, Tang A H, et al. The ion chemistry and the source of PM2.5 aerosol in Beijing[J]. Atmos Environ, 2005, 39(21): 3771-3784.