Concentrations, profiles and gas-particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans in the ambient air of Beijing, China

Polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs) were monitored in the ambient air of Beijing, China, from February to December 2006 to evaluate their concentrations, congener profiles and gas-particle partitioning. The PCDD/F concentrations for three different districts ranged from 275 to 10,780 fg m^-3, with an average of 4355 fg m^-3. The I-TEQs were 18-644 fg I-TEQ m^-3, with an average of 268 fg I-TEQ m^-3, which was comparable or slightly higher than other urban locations around the world. Severe dust event occurred during the sampling period, on 17-19 April 2006. The levels of PCDD/Fs did not increase during the dust event (average 2489 fg m^-3) compared to non-dust events (average 3671 fg m^-3) although the total suspended particulates (1109 μg m^-3) presented a 2.8-fold increase compared to non-dust events (392 μg m^-3). The PCDD/Fs were found exclusively in the particle phase. Significant linear correlations for PCDD/Fs were observed (R²: 0.57-0.64) between the gas-particle partition coefficient (K_p) and the subcooled liquid vapor pressure (P_L⁰). The Junge-Pankow model and the K_oa absorption model were employed to predict the gas-particle partitioning of PCDD/F congeners. The K_oa absorption model fitted well with the measurement results. However, the Junge-Pankow model slightly underestimated the particulate sorption of PCDD/Fs, which was contradicted with previous studies reported in the literature.