Project at a Glance

Title: Lifetimes and fates of toxic chemicals in California's atmosphere

Principal Investigator / Author(s): Winer, Arthur M

Contractor: Statewide Air Pollution Research Center, University of California, Riverside

Contract Number: A5-104-32

Research Program Area: Atmospheric Processes

Topic Areas: Chemistry & Reactivity


The atmospheric chemistry of sixteen organic compounds, all directly relevant to the California Air Resources Board's responsibilities for assessing and regulating toxic air contaminants, has been experimentally investigated using the Statewide Air Pollution Research Center's environmental chamber facilities. Specifically, we determined the kinetics and / or the products of the gas-phase reactions of hydroxyl (OH) radicals, ozone (O3) and nitrate (NO3) radicals with ethylene oxide, vinyl chloride, 1,1-dichloroethene, cis- and trans-1, 2-dichloroethene, trichloroethene, tetrachloroethene, acrolein, allyl chloride, benzyl chloride, o-, m- and p-cresol, naphthalene, 1,4-benzodioxan and 2,3-dihydrobenzofuran.

These kinetic data were used to calculate corresponding atmospheric lifetimes for each compound, for the three possible reaction pathways. Except for the three cresol isomers and 2, 3-dihydrobenzofuran, which also react rapidly with NO3 radicals, the dominant reaction pathway for the compounds studied is by reaction with the OH radical. None of the compounds investigated react sufficiently fast with O3 under atmospheric conditions for this process to represent a significant atmospheric removal pathway. Based on their atmospheric lifetimes of - five min. to ten hrs., the cresols, 1, 4-benzodioxan and 2, 3-dihydrobenzofuran are expected to have a local range of influence. Vinyl chloride, 1, 1-dichloroethene, acrolein, allyl chloride and naphthalene, with lifetimes between ~1 and ~5 days, will be regionally distributed while benzyl chloride cis- and trans-dichloroethene, trichloroethene and ethylene oxide, with lifetimes from one week to one year, can be globally distributed, as well as having more local effects.

Where feasible, product studies were conducted, principally using in situ Fourier transform infrared spectroscopy and gas chromatography, to determine the atmospheric reaction products produced from the parent compounds investigated. These product studies provided valuable mechanistic data, especially for the reactions of the chloroethenes, allyl chloride and acrolein with the OH radical.

The OH radical rate constant data obtained in this program were combined with available literature data in order to further develop appropriate structure-reactivity relationships. Such relationships permit cost-effective estimation of the atmospheric lifetimes for additional organic compounds whose low volatility or chemical complexity make direct experimental investigation difficult or impossible.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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