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 (~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 µm particles and more than 80% of the PXDD/Fs were found to be in the d ae < 2.5 µm 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.

A comparison of the levels and particle size distribution of lower chlorinated dioxin/furans (mono- to tri-chlorinated homologues) with those of tetra- to octa-chlorinated homologues in atmospheric samples

“…Most previous studies on ambient air have focused on the levels and distribution patterns of tetra-to octa-CDD/Fs (Li et al, 2008b;Wang et al, 2010;Zhang et al, 2012Zhang et al, , 2015. To our knowledge, there are no studies on the particle size distribution of lower chlorinated homologues and no comparisons of their distribution with that of higher chlorinated homologues in ambient air.…”

“…SCl 1e3 DD/Fs were abundant in the gas phase, accounting for 95% of SCl 1e8 DD/Fs; SCl 1e3 DFs were particularly prevalent, accounting for >96% of SCl 1e8 DFs. SCl 1e3 DD/Fs were the main PCDD/F homologues in the gas phase, while SCl 4e8 DD/Fs were the dominant homologues in the particulate phase, accounting for 73% of SCl 1e8 DD/Fs (Zhang et al, 2015).…”

“…The concentrations of 2,8-DiCDF and 2,4,8-TrCDF were lower than those of 3-MoCDF. Our previous research demonstrated that 1,2,3,4,6,7, were the most abundant congeners of 17 2,3,7,8-PCDD/Fs, accounting for only 4.4% and 4.2% of 3-MoCDF, respectively (Zhang et al, 2015). The concentrations of SCl 1e3 DD/Fs in these samples are higher than those of SCl 4e8 DD/Fs, and the associated environmental and health risks of SCl 1e3 DD/Fs in the atmosphere should not be ignored.…”

“…Five air sample groups, including gas phase, and particle phase with aerodynamic diameters (d ae s) of four size classes: >10 mm, 2.5e10 mm, 1.0e2.5 mm, and <1.0 mm were collected. Detailed information about the sampling sites and techniques are provided in our previous study (Zhang et al, 2015). Data on homologue and congener profiles, and particle size distribution of tetra-to octa-CDD/Fs in the atmosphere investigated in that study will be used to compare with data on mono-to tri-chlorinated homologues measured in this study.…”

“…We collected the samples for this study from this site, and used previously collected data to ensure data stability and comparability (Zhang et al, 2015). Five air sample groups, including gas phase, and particle phase with aerodynamic diameters (d ae s) of four size classes: >10 mm, 2.5e10 mm, 1.0e2.5 mm, and <1.0 mm were collected.…”