Fig. 3: Profile of the urban tracers in submicron aerosols.

a Time series of the normalized mass concentration of phthalic acid and other dicarboxylic acids. The black line is for the phthalic acid while the other colors are for the other urban tracers. b Production pathway analysis of urban dicarboxylic acid based on their relationship with elemental carbon and phthalic acid, which are indicators for primary and secondary origins. The numbers in the legend are the mean mass concentration of the urban tracers.