Polycyclic aromatic hydrocarbons in PM2.5 and PM2.5-10 in Urumqi, China: Temporal variations, health risk, and sources

Abstract

PM2.5 and PM2.5-10 samples were simultaneously collected in Urumqi from January to December 2011, and 14 priority polycyclic aromatic hydrocarbons (PAHs) were determined. The mean concentrations of total PAHs in PM2.5 and PM2.5-10 were 20.90~844.22 ngm-3 and 19.65~176.5 ng m-3 respectively, with the highest in winter and the lowest in summer. Above 80% of PAHs were enriched in PM2.5, which showed remarkable seasonal variations compared to coarse particles. High molecular weight (HMW) PAHs were predominant in PM2.5 (46.61~85.13%), whereas the proportions of lower molecular weight (LMW) and HMW PAHs in PM2.5-10 showed a decreasing and an increasing trend, respectively, from spring to winter. The estimated concentrations of benzo[a]pyrene equivalent carcinogenic potency (BaPeq) in PM2.5 (10.49~84.52 ng m-3) were higher than that of in PM2.5-10 (1.15~13.33 ng m-3) except in summer. The estimated value of inhalation cancer risk in PM2.5 and PM2.5-10 were 1.63 × 10-4~7.35 × 10-3 and 9.94 × 10-5~1.16 × 10-3, respectively, far exceeding the health-based guideline level of 10-4. Diagnostic ratios and positive matrix factorization results demonstrated that PAHs in PM2.5 and PM2.5-10 were from similar sources, such as coal combustion, biomass burning, coking, and petroleum combustion, respectively. Coal combustion was the most important source for PAHs both in PM2.5 and PM2.5-10, accounting for 54.20% and 50.29%, respectively.