Unexpectedly high PCDD/F loadings on coarse particle in municipal solid waste incineration flue gas

Emission of polychlorinated dibenzodioxins and furans (PCDD/Fs) from municipal solid waste incineration (MSWI) poses a considerable public health risk, and characterization of PCDD/Fs' size distribution in flue gas is essential for understanding their formation, removal, atmospheric transport, and inhalation risks. Here, we conducted a detailed investigation on the gaseous and size-resolved PCDD/Fs in the stack gas of an MSWI plant using a thermal aerosol diluter coupled with a 14-stage sampler, covering particles of 10 nm-18 μm. The total emitted concentration of the PCDD/Fs was 1872.3 pg/m³, corresponding to 28.8 pg TEQ /m³. While particle mass concentration predominantly concentrated in the coarse mode, the size distribution of PCDD/Fs and their TEQ presented a bimodal pattern, with a major peak in the coarse mode and a secondary peak in the ultrafine mode. Heavier PCDD/Fs were abundant in coarse mode, whereas lighter PCDD/Fs were evenly associated with all size range particles. The gas particle partitioning processes via adsorption effectively explained the size distribution and homolog pattern of PCDD/Fs. The abnormal coarse mode abundance of particles after fabric filter was possibly in-stack generated by the continuous abrasion between acidic flue gas and the steel structure. PCDD/Fs from upstream of stack repartition onto the generated coarse particles, reshaping their overall size distribution. Our findings indicate that the in-stack process plays important role in PCDD/Fs emission from MSWI plants.