Characterization of PM2.5- and PM10-Bound Polycyclic Aromatic Hydrocarbons in Urban and Rural Areas in Beijing during the Winter

Abstract

Polycyclic aromatic hydrocarbons (PAHs) were here investigated in airborne particulate matter (PM2.5 and PM10) samples collected in urban (including residential, commercial, industrial, and traffic zones) and rural areas in and around Beijing from December 2005 to January 2006. Sixteen polycyclic aromatic hydrocarbons adsorbed onto fine- (PM2.5) and coarse- (PM10) grained samples were analyzed by gas chromatography-mass spectrometry (GC-MS). The mean total PAH concentrations were 30.1 and 80.1 ng/m3 in PM2.5, and 44.1 and 99.8 ng/m3 in PM10 in urban and rural areas, respectively. PAHs were mostly adsorbed on small inhalable particles (>50%) with four to six rings, which dominated both fractions. Strong correlations between PM-associated extractable organic matter (EOM) and particulate PAHs were found, especially in PM2.5, indicating that PM-PAHs concentrations were strongly influenced by PM-associated EOM. Of the different functional areas studied, the total PAH concentrations in both fractions were highest in industrial and rural areas and lowest in traffic zones. This may have been the result of the different emission sources and more efficient energy structures that occur during the winter. Distribution profiles and diagnostic ratios revealed that coal combustion was the major source of PM2.5- and PM10- associated PAHs. Additional sources of PAHs may include vehicle emissions, natural gas combustion and wood burning. BaP-based toxic equivalence factor (BaPeq), BaP-equivalent carcinogenic power (BaPE) and a sum of five carcinogenic PAHs showed that the industrial and rural areas were the most vulnerable to PAHs.