• PCDD/F particle size distributions on haze days and normal days were determined.• Higher concentrations of airborne PCDD/Fs were detected during all haze days.• 95% of PCDD/Fs were absorbed in the d ae b 2.5 μm particles on haze days.• Harner-Bidleman model predicted the particulate fractions of PCDD/F congeners well.
G R A P H I C A L A B S T R A C TThe following figure is presented as the graphical abstract.a b s t r a c t a r t i c l e i n f o Little information is available on the distributions of airborne polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) during haze days. In this study, PCDD/F concentrations, particle size distributions, and gas-particle partitioning in a Beijing suburban area during haze days and normal days were investigated. High PCDD/F concentrations, 3979-74,702 fg m −3 (173-3885 fg I-TEQ m −3), were found during haze days and~98% of the PCDD/Fs were associated with particles. Most PCDD/F congeners (N 90%) were associated with particles. PCDD/ F concentrations increased as particle sizes decreased and 95% of the particle-bound PCDD/Fs were associated with inhalable fine particles with aerodynamic diameters b 2.5 μm. PCDD/Fs were mainly absorbed in the particles and the Harner-Bidleman model predicted the particulate fractions of the PCDD/F congeners in the air samples well. The investigated PCDD/F concentrations and particle-bound distributions were different during normal days than during haze days. Temporal airborne PCDD/F trends in a suburban area during haze conditions could support better understanding of the exposure risk posed by toxic PCDD/Fs associated with fine particles.