Atmospheric particle size distributions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs) and their implications for wet and dry deposition

Concurrent measurements of polychlorinated dibenzo-p-dioxins and dibenzofur ans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs) in different size fractions of atmospheric particulate matter are presented for a winter and a summer sampling period. The PCDD/Fs and PAHs were primarily associated w ith particles of < 1.35 mu m aerodynamic diameter. The particle size distri butions were similar for the compounds within each substance group and, sur prisingly, also between the PCDD/Fs and PAHs. Changes in the particle size distribution of particle mass were reflected in the particle size distribut ions of the PCDD/Fs and PAHs. The data were employed to identify those particle size fractions dominating the wet and dry particle bound deposition of PCDD/Fs and PAHs and, further more, to assess the relative contributions of wet and dry deposition to the total particle bound deposition fluxes. The calculations indicate that coa rse particles contribute most to the dry deposition while, in contrast, the wet deposition of the PCDD/Fs and PAHs is dominated by fine particles. Fur thermore, it is estimated that in Bayreuth wet deposition dominates the tot al particle bound deposition of PCDD/Fs and PAHs. (C) 1998 Elsevier Science Ltd. All rights reserved.