Characteristics of atmospheric polycyclic aromatic hydrocarbons (PAHs) in gas and particle phase in April and July 2011 in Beijing, China

摘要

Presence of atmospheric PAHs in urban and suburban region (Beijing, China) was studied in April and July 2011. Forty-four pairs of gas and particle (TSP) phase samples were collected every six day by high volume (Hi-Vol) air samplers at four sampling sites, and determined separately by GC/MS based on USEPA Method TO-13A. Average total concentration (gas + particles) of PAHs (T-PAHs) was 135.1±49.0 ng/m~3 and 181.2±40.9 ng/m~3 in April and July, respectively. Gas phase PAHs (G-PAHs) was the major fraction, comprising 63-92% of T-PAHs. Lighter (2-, 3-, 4-ring) and heavier (5-, 6-ring) PAHs were found predominantly in gas and particle phase, respectively. 2- to 6-ring PAHs contributed 10%, 53%, 26%, 7% and 4% of T-PAHs, respectively. Five major PAHs, naphthalene (NAP), fluorene (FLU), PHE, fluoranthene (FLA), and pyrene (PYR) contributed 70 - 90% of T-PAHs. G-PAHs increased significantly while PAHs in particle phase (P-PAHs) decreased from April to July. Volatilization from soil and more emission from power generation increase might explain the increase of G-PAHs, and the washout of P-PAHs along with particles might explain the decrease of P-PAHs. Given particulate organic carbon (OC) and elemental carbon (EC) being well correlated, P-PAHs was moderately correlated with OC and EC, suggesting that there were other mechanisms contributing to P-PAHs different from those of OC/EC. Significant correlation between P-PAHs with SO_2 and NO_2 suggested coal combustion and automobile exhaust to be contamination contributors.