HR: 1330h
AN: A52A-0773    [PDF]
TI: Laboratory Studies of Stable Carbon Isotope Fractionation during The Formation of Secondary Particulate Organic Matter from Toluene-OH radical Initiated Reactions
AU: * Irei, S
EM: satoshi@yorku.ca
AF: Centre for Atmospheric Chemistry, York University, 4700 Keele St., Toronto, ON M3J 1P3 Canada
AU: Huang, L
EM: Lin.Huang@ec.gc.ca
AF: Meteorological Service of Canada, Environment Canada, 4905 Dufferin St., Toronto, ON M3H 5T4 Canada
AU: Zhang, W
AF: Meteorological Service of Canada, Environment Canada, 4905 Dufferin St., Toronto, ON M3H 5T4 Canada
AU: Collin, F
AF: Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Universit\'{e} Ren\'{e} Descartes, 45, rue des Saints P\'{e}res 75270, Paris, Cedex 06 France
AU: Hastie, D
AF: Centre for Atmospheric Chemistry, York University, 4700 Keele St., Toronto, ON M3J 1P3 Canada
AU: Rudolph, J
EM: jrudolph@yorku.ca
AF: Centre for Atmospheric Chemistry, York University, 4700 Keele St., Toronto, ON M3J 1P3 Canada
AB: Stable carbon isotope measurements have become useful in the atmospheric chemistry for organic compounds in the gas phase as well as in airborne particulate matter. Although a reasonable understanding is developing for the gas phase isotope fractionation process, little is known about the isotope fractionation associated with the formation of secondary particulate organic matter (POM). The isotope fractionation study has potential: to understand more detail of the reaction mechanisms to form the secondary POM; and to estimate the contribution of secondary POM to the airborne particulate matter. These are important to trace the stable carbon isotope budget in the atmosphere. Here, we present the results of laboratory measurements of stable isotope ratio for toluene, a precursor gas, and secondary POM formed by its OH radical initiated gas phase oxidation. The reaction of toluene at ppm levels with OH radicals was studied in a flow reactor with a residence time of 3.3 minutes. The OH radicals were produced by the photochemical reaction of isopropyl nitrite in the presence of oxygen and nitric oxide. The concentration was in the range of 10$^{8}$ radicals cm$^{-3}$. Approximately 15 percent of the toluene reacted with the OH radicals. The secondary POM formed in the reactor was collected on quartz fibre filters and analyzed for the stable carbon isotope ratios. For these experiments, the toluene and the collected POM showed -26.7 and -31.8 permil in VPDB scale, respectively. Compared to 6.1 permil that is the kinetic isotope effect of toluene reacting with OH radicals, the isotope fractionation of 5.1 permil is in good agreement. Although these results may only be valid for very specific reaction condition, they nevertheless strongly suggest that the stable carbon isotope ratios of secondary POM in the atmosphere will be significantly influenced by the kinetic isotope effects of the oxidation reactions of the precursor compounds.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting