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List of Abstracts 56Contact: a.ryan@lancaster.ac.ukBiogenic volatile organic compounds (BVOC) can undergo photo-oxidation reactions in the atmosphere.The products of these reactions may condense onto atmospheric particles, or nucleate in the absence of preexistingseed, to form secondary organic aerosol (SOA). The ability of BVOC to form SOA is particularlyimportant in remote tropical locations where almost half of all reactive BVOC are emitted. However, theease with which individual BVOC, or their products, partition into the particle phase is the subject of somedebate.This study characterised the BVOC emissions from three south-east Asian tropical plant species (Ficuscyathistipula, Ficus benjamina and Caryota millis) and, in a series of smog chamber experiments, examinedtheir ability to contribute to SOA formation under atmospherically relevant conditions. All three specieswere found to be high isoprene, low monoterpene and sesquiterpene emitters. Under simulated tropicalrainforest environmental conditions, we found that these predominantly isoprene emitting plants did notcontribute to the formation of SOA. However, analysis of gas phase GC-MS and PTR-MS data indicated thatisoprene epoxide and hydroxyhydroperoxide, both suggested to be isoprene gas phase aerosol precursors,were produced. In contrast, experiments under the same conditions using common silver birch (BetulaPendula), a high monoterpene and sesquiterpene, but low isoprene emitter, resulted in SOA formation viaboth fresh nucleation and condensation onto pre-existing seed. Under these experimental conditions, our datasuggest that isoprene may contribute only indirectly to the formation of SOA via reactions involving secondand third generation oxidation products.P-Interfaces.32 ID:4432 15:35The Photo-reduction of Oxidized Mercury Species with Selected Thiols at the Air/Water InterfacesLin Si, Parisa AriyaDepartment of Chemistry & Department of Atmospheric and Oceanic Sciences, McGill UniversityContact: lin.si@mail.mcgill.caMercury is an environmental contaminant of global concern. The reduction of oxidized mercury species(Hg(II)) to elemental mercury (Hg(0)) affects the global distribution of mercury and competes formethylation processes of mercury in aquatic environment. This study focused on the kinetics andmechanistic studies of the reduction of Hg(II) by thiols. The reaction kinetics was studied using cold vaporatomic fluorescence spectroscopy (CVAFS), the formation of Hg(II)-thiol complexes (Hg(SR)2) wereconfirmed by UV-visible spectrometry and Atmospheric Pressure Chemical Ionization-Mass Spectrometry(APCI-MS), and the reaction products were analyzed using Electron Impact-Mass Spectrometry (EI-MS)and Solid Phase Microextraction coupled with Gas Chromatography-Mass Spectrometry (SPME/GC-MS).The reaction rates were obtained for 1-propanethiol, 1-butanethiol, and 1-pentanethiol at environmentalrelevant conditions. The effects of light, pH, dissolved oxygen and chloride ion on reaction rates were alsoinvestigated. Our results indicated that the reaction intermediate, i.e. (Hg(SR)2), could absorb photons withwavelengths longer than 290 nm (the sunlight limit) and subsequently be photo-reduced to Hg(0). Theidentified products were Hg(0) and disulfides (R-S-S-R). The potential environmental implications areherein discussed.P-Interfaces.33 ID:4189 15:35Determination of Formaldehyde in Ambient Air Using Solid Phase Microextraction (SPME)Visahini Kanthasamy, Parisa AriyaMcGill UniversityiCACGP-IGAC 2010 12 July, 2010