PARENT SESSION

TA6 Atmospheric Transport and Fate
202 Oregon Ballroom
8:00 AM - 12:00 PM, Tuesday

() On the role of black carbon for the long-range transport of PAHs.

Lohmann, R^{1, 2}, Lammel, G², Semeena, V², ¹ University of Bremen, Bremen, Germany² Max-Planck-Institute for Meteorology, Hamburg, Germany

ABSTRACT- By reviewing published gas-particle distributions of PAHs, we found evidence for both absorptive and adsorptive contributions. Based on results from laboratory and controlled field studies we suggest that on average, octanol-air partitioning (K_oa) is a good approximation for the organic matter (OM) absorption of PAHs. However, higher concentrations in particles than could be explained by OM absorption were found in selected gas-particle partitioning field studies, which were corrected for gaseous adsorption to the filter. We argue that adsorption onto black carbon (BC) is responsible for most of the additional sorption. Apparent adsorption coefficients to BC, K_BC-air, were derived from field studies and showed good agreement with those predicted by adsorption onto diesel soot. For atmospheric long-range transport models we used a dual OM absorption and BC adsorption model, with BC properties being approximated by diesel soot: K_p = 10^-12 (f_om x K_oa/ _oct + f_BC x K_BC-air/ _BC). Model simulations were performed with a general circulation model of the atmosphere (ECHAM 5) with a dynamic atmospheric aerosol (HAM) and chemistry (radicals, sulphur cycle) modules for the global dispersion of benzo[a]pyrene and phenanthrene. Model runs were performed comparing the effect of the Junge-Pankow adsorption model with our dual parameterisation for the long-range transport and final sinks of PAHs.

Key words: gas-particle partitioning, PAHs, black carbon, long-range transport