Polycyclic aromatic hydrocarbons in PM2.5 in Guangzhou, southern China: spatiotemporal patterns and emission sources.

Fine particulate samples were simultaneously collected at six sites in Guangzhou in November-December 2009. Eighteen polycyclic aromatic hydrocarbons (PAHs) and tracers, i.e. hopanes, elemental carbon, picene and levoglucosan were measured. Three high level episodes were observed during the sampling period, likely due to accumulation effects. Back trajectory analysis revealed that the air masses for the three episodes were from eastern inland Pearl River Delta (PRD) region. There was no obvious concentration gradient for total and 5-6 ring PAHs such as benzo[g,h,i]perylene (BghiP) from urban to rural sites. However, 4-ring PAHs such as pyrene (Pyr) exhibited significantly higher levels at rural site than that at urban/suburban sites (p<0.01). BghiP correlated well with hopanes, elemental carbon and picene, indicating vehicular emissions and coal combustion were the sources of 5-6 ring PAHs, which were further confirmed by comparing the four tracers/BghiP ratios and IcdP/BghiP ratios in ambient samples with those from source profiles. Results indicated that vehicular emissions were no longer the dominant sources in winter season in Guangzhou.