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(15-38) Experimental Study of the Reactions of OH radicals with Polycyclic Aromatic Hydrocarbons Adsorbed on Graphite Particles . BUDZINSKI, Hélène*,1, ESTEVE, Williams1,2, PERRAUDIN, Emilie1,2, VILLENAVE, Eric2, 1 LPTC-UNIVERSITE BORDEAUX I, TALENCE, FRANCE, FRANCE2 LPCM-UNIVERSITE BORDEAUX I, TALENCE, FRANCE, FRANCE ABSTRACT- Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants, present in every compartments of the environment : soils and sediments, marine and continental waters, atmospheric phase and biota. In order to improve our knowledge of their biogeochemical cycles, the study of each compartment appears essential. More precisely, the study of the atmospheric phase is of primary importance to elucidate their long-range transport and their photochemical reactivity. Due to their physico-chemical properties and their major way of formation (pyrolytic one), PAHs are mostly present in the atmospheric phase adsorbed on fine particles that form the respirable part of the atmospheric aerosol. In the atmospheric phase, adsorbed PAHs are subjected to various degradation processes which can modify their structures and their physico-chemical properties. The most important process is the photo-oxydation, with various atmospheric oxydants (OH and NOx radicals, ozone). As the corresponding oxydation products may be much more toxic than the parent PAHs, their determination and the elucidation of photo-oxydation mechanisms are essential. Few information on the chemical and photochemical degradation of adsorbed PAHs is available. The purpose of the present work is to present the first results obtained on a new experimental apparatus developped in Bordeaux to study the photo-oxydation of PAHs in the heterogeneous phase (at the gas-particle interface). A discharge-flow reactor, coupled with laser induced fluorescence detector, has been developped and tested with different PAHs, like phenanthrene, anthracene, benzo[e]pyrene and fluoranthene. The work has dealt firstly with the study of their reactions with OH radicals, graphite being chosen in a first part as a model of atmospheric particles. Photo-oxydation products have been tentitatively identified by HPLC and GC/MS. Key words: PAH, OXYDATION, CONDENSED PHASE, OH RADICAL |
