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 mum 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 d(ae) < 0.41 mum, and 90% of the PCDD/Fs were found on the particles d(ae) < 2.1 mum in both sites. The distribution of PCDD/Fs varied over the particle size range 1.4-2.1 mum, regardless of sampling site. The less-chlorinated dioxin/furans (tetra-, penta-CDD/Fs) were mainly distributed among large particles (d(ae) > 2.1 mum), whereas high-chlorinated dioxin/furans (hexa-, hepta-, octa-CDD/Fs) were mainly found among fine particles (d(ae) < 2.1 mum). 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. (C) 2002 Published by Elsevier Science Ltd.