Identification of concentrations and sources of PM2.5-bound PAHs in North China during haze episodes in 2013

An analysis of 12 polycyclic aromatic hydrocarbons (PAHs) in PM2.5 (particulate matter with a diameter smaller than 2.5 microns) samples collected at Yucheng, Shandong, in June 2013 was conducted to determine the concentrations, composition, sources, and associated cancer risk. The results revealed that the average PAH concentration was higher during haze episodes (28.28 +/- 8.35 ng m(-3)) when compared to non-haze episodes (23.68 +/- 4.17 ng m(-3)), and diagnostic ratio and principal component analyses indicate that the predominant sources of PAHs were from fossil fuel and coal combustion, likely from vehicle emissions and industrial sources and biomass burning. Coal combustion and biomass burning contributed significantly more during haze episodes, whereas liquid fossil fuel combustion (e.g. petroleum) was the dominant contributor during the non-haze periods. In addition, back-trajectory calculations revealed that the long-distance transport of air masses from regions with industrial pollution and biomass burning contributed significantly to the concentrations of PAHs in the region. The concentration of high molecular weight PAHs (HMW-PAHs) increased from 62.3 % under non-haze conditions to 67.9 % during the haze periods. The benzo[a]pyrene-equivalent carcinogenic potency value during haze episodes was higher (7.09 ng m(-3)) than that during non-haze (5.64 ng m(-3)) periods and adults over 30 years old in the Shandong province are at an increased risk of cancer from PAHs.