title: Comparison and implications of PM₂.₅ carbon fractions in different environments.
abstract: The concentrations of PM₂.₅ carbon fractions in rural, urban, tunnel and remote environments were measured using the IMPROVE thermal optical reflectance (TOR) method. The highest OC1 and EC1 concentrations were found for tunnel samples, while the highest OC2, OC3, and OC4 concentrations were observed for urban winter samples, respectively. The lowest levels of most carbon fractions were found for remote samples. The percentage contributions of carbon fractions to total carbon (TC) were characterized by one peak (at rural and remote sites) and two peaks (at urban and tunnel sites) with different carbon fractions, respectively. The abundance of char in tunnel and urban environments was observed, which might partly be due to traffic-related tire-wear. Various percentages of optically scattering OC and absorbing EC fractions to TC were found in the four different environments. In addition, the contribution of heating carbon fractions (char and soot) indicated various warming effects per unit mass of TC. The ratios of OC/EC and char/soot at the sites were shown to be source indicators. The investigation of carbon fractions at different sites may provide some information for improving model parameters in estimating their radiative effects.
authors.affiliation: Key Lab of Aerosol Science & Technology, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China. Electronic address: chongshu@ieecas.cn.
authors.forename: Chong-Shu
authors.initials: CS
authors.lastname: Zhu
authors.forename: Jun-Ji
authors.initials: JJ
authors.lastname: Cao
authors.forename: Chuen-Jinn
authors.initials: CJ
authors.lastname: Tsai
authors.forename: Zhen-Xing
authors.initials: ZX
authors.lastname: Shen
authors.forename: Yong-Ming
authors.initials: YM
authors.lastname: Han
authors.forename: Sui-Xin
authors.initials: SX
authors.lastname: Liu
authors.forename: Zhu-Zi
authors.initials: ZZ
authors.lastname: Zhao
keywords: Char/soot; Elemental carbon; OC/EC; Organic carbon; PM(2.5)