Particle size distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans in the ambient air of an electric-arc furnace-dust treatment plant

Atmospheric particle size distributions of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) between 0.166 and 100μm in aerodynamic diameter (D_p) were measured at two sampling sites. The two sites (OR and SG) were approximately 100m from the fugitive emission areas inside an electric-arc furnace-dust treatment plant (hereinafter to referred as the TSU plant) and were 6.5 and 1.5m above ground level, respectively. Size-segregated atmospheric particles were collected through means of a micro-orifice uniform deposit impactor (MOUDI) and a Noll rotary impactor (NRI) when the sampling sites were downwind (April, 2007) and upwind (May, 2007) from the fugitive emission area of the TSU plant. Experimental results indicate that PCDD/Fs were associated with the full size range of atmospheric particles. For fugitive sources in TSU plant, although less than 49% of total PCDD/Fs and toxic equivalents (TEQs) were found to be associated with fine particles, more than 54% of total PCDD/Fs and TEQs were correlated with fine particles from outside-plant emission sources. Particle size distributions of total PCDD/Fs and TEQs were shifted to larger particles with a decreasing altitude. Notably, PCDFs distributed extensively among aerosol size fractions based on their chlorination level during all sampling periods. Overall mass median diameter (MMD_o) of total-PCDD/F-TEQs for fugitive areas in the TSU plant were higher than those from outside-plant emission sources.