Size distribution of particle-bound polychlorinated dibenzo-p-dioxins and dibenzofurans in the ambient air of a municipal incinerator

The atmospheric particle size distributions of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) between 0.056 and 100μm in aerodynamic diameter (Dp) were measured at two sampling sites during January 2002. These sites were 1.1 and 2.1km downwind from a municipal incinerator in central Taiwan, respectively. Size-segregated atmospheric particles were simultaneously collected by means of a cascade impactor and a rotary impactor. The results showed that PCDD/Fs were associated with the full size range of atmospheric particles. More than 80% of the ΣPCDD/Fs and toxic equivalents (TEQs) were found to be associated with fine particles of aerodynamic diameter, Dp<2.0μm. Generally a smaller particle had a higher ΣPCDD/Fs content. The particle size distributions of ΣPCDD/Fs and TEQs were shifted to larger particles with increasing time and distance. It is noteworthy that PCDFs were found to distribute significantly among aerosol size fractions based on their chlorination level at both sampling sites. There was an increase in the proportion of the less chlorinated PCDFs in the coarse particles (D p>2.0μm). As for PCDDs, however, a relative enrichment of the less chlorinated congeners on coarse particles was found only at the farther sampling site (2.1km).