Particle Size Distributions of PCDD/Fs and PBDD/Fs in Ambient Air in a Suburban Area in Beijing, China

Abstract

The particle size distributions of polychlorinated and polybrominated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs and PBDD/Fs, respectively; together labeled PXDD/Fs) in ambient air in a suburban area in Beijing, China, were determined. The sums of the concentrations of the 17 2,3,7,8-PCDD/Fs and the sums of the concentrations of the 13 2,3,7,8-PBDD/Fs that were analyzed were 1499-2799 fg m(-3) (95.4-175.4 fg I-TEQ m(-3)) and 1171-2424 fg m(-3) (42.2-109.3 fg TEQ m(-3)), respectively. The PXDD/Fs were mainly (similar to 90%) in the particulate phase. Significant linear correlations were found between the gas/particle partition coefficients (K-p) and subcooled liquid vapor pressures (P-L(0)) of the PXDD/Fs. The regression coefficients indicated that the PCDD/Fs were mainly adsorbed to the particles and that the PBDD/Fs were mainly absorbed by the particles. The concentrations of the PXDD/Fs increased as the particle size decreased. The highest PXDD/F concentrations were found in the d(ae) < 1.0 mu m particles and more than 80% of the PXDD/Fs were found to be in the dae < 2.5 mu m particles. Similar regression coefficients were found for the K-P against P-L(0) for the different particle size fractions in the air. The PXDD/F distribution profiles in particles of different sizes were also studied. The lower chlorinated PCDD/Fs were found at higher concentrations in the coarser particles, and the higher chlorinated PCDD/Fs were mainly found in the finer particles. Polybrominated dibenzofurans, particularly the higher brominated dibenzofurans, were the dominant PBDD/F congeners. The contributions of the higher brominated dibenzofurans to the total PBDD/F concentrations decreased as the particle size increased, but that was not the case for the polybrominated dibenzo-p-dioxins.