Distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in different sizes of airborne particles

The concentration of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and particle mass distribution were measured in size-segregated airborne particulate matter using a six-stage high-volume cascade impactor in urban and suburban areas in the summer and fall. The distribution of particle concentration and PCDD/Fs concentration with respect to particle size was presented by using various methods. More than 50% of particles were in the <1.4 μm size class and the particles showed the bimodal size-distribution pattern characteristic of urban particles. More than 60% of the PCDD/Fs were associated with particles of dae<0.41 μm, and 90% of the PCDD/Fs were found on the particles dae<2.1 μm in both sites. The distribution of PCDD/Fs varied over the particle size range 1.4–2.1 μm, regardless of sampling site. The less-chlorinated dioxin/furans (tetra-, penta-CDD/Fs) were mainly distributed among large particles (dae>2.1 μm), whereas high-chlorinated dioxin/furans (hexa-, hepta-, octa-CDD/Fs) were mainly found among fine particles (dae<2.1 μm). The fraction of less-chlorinated dioxin/furans increased with increasing particle size; however, the opposite was true for high-chlorinated dioxin/furans. These results are similar to the findings for polyaromatic hydrocarbons in previous reports.