Yields of β-Hydroxynitrates and Dihydroxynitrates in Aerosol Formed from OH Radical-Initiated Reactions of Linear Alkenes in the Presence of NOx
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- 作者：Aiko Matsunaga ; Paul J. Ziemann
- 刊名：Journal of Physical Chemistry A
- 出版年：2009
- 出版时间：January 22, 2009
- 年：2009
- 卷：113
- 期：3
- 页码：599-606
- 全文大小：190K
- 年卷期：v.113,no.3(January 22, 2009)
- ISSN：1520-5215
文摘
Yields of β-hydroxynitrates and dihydroxynitrates in aerosol formed from OH radical-initiated reactions of linear C8−C17 1-alkenes and C14−C17 internal alkenes in the presence of NOx were measured using a thermal desorption particle beam mass spectrometer coupled to a high-performance liquid chromatograph (HPLC) with UV−vis detector for identification and quantification. For 1-alkenes, total yields of β-hydroxynitrates normalized for OH radical addition to the CC double bond increased with carbon number, primarily because of enhanced gas-to-particle partitioning, to a plateau of 0.140 ± 0.009 in the C14−C17 range, with 1-hydroxy/2-hydroxy isomer fractions of 0.7:0.3. When combined with yields measured by O’Brien et al. ( O’Brien, J. M., Czuba, E., Hastie, D. R., Francisco, J. S., and Shepson, P. S. J. Phys. Chem. A 1998, 102, 8903) for reactions of smaller alkenes, the results for both 1-alkenes and internal alkenes indicate that the branching ratios for the formation of β-hydroxynitrates from the reactions of NO with β-hydroxyperoxy radicals (averaged over both isomers) increase from 0.009 for C2 up to 0.13−0.15 for C14 and larger and are approximately half the values determined by Arey et al. ( Arey, J., Aschmann, S. M., Kwok, E. S. C., and Atkinson, R. J. Phys. Chem. A 2001, 105, 1020) for the corresponding alkyl peroxy radicals. The range of branching ratios may be higher for individual isomers, but this could not be determined. It is estimated that for 1-alkenes, approximately 60−70% of OH radical addition occurred at the terminal carbon atom. Average yields of dihydroxynitrates normalized for OH radical addition were 0.039 ± 0.006 and 0.006 ± 0.002 for 1-alkenes and internal alkenes, with differences reflecting enhanced decomposition of β-hydroxyalkoxy radicals formed from internal alkenes. The addition of NH3 reduced yields significantly, apparently by altering hydrogen bonding between hydroxy and peroxy groups in hydroxyperoxy radical−NO complexes, whereas adding H2O had no obvious effect.