Observations of total peroxy nitrates and aldehydes: measurement interpretation and inference of OH radical concentrations

P. A. Cleary (1) , P. J. Wooldridge (1) , D. B. Millet (2) , R. C. Cohen (2) , M. Mckay (2, 3) , A. H. Goldstein (1, 3, 4)

1 Dept. of Chemistry
2 Dept. of Environmental Science
3 Energy and Environment Technologies Division [LBNL Berkeley]
4 EPS - Department of Earth and Planetary Science [UC Berkeley]

We describe measurements of total peroxy nitrates (?PNs), NO₂, O₃ and several aldehydes at Granite Bay, California, during the Chemistry and Transport of the Sacramento Urban Plume (CATSUP) campaign, from 19 July?16 September 2001. We observed a strong photochemically driven variation of ?PNs during the day with the median of 1.2 ppb at noon. Acetaldehyde, pentanal, hexanal and methacrolein had median abundances in the daytime of 1.2 ppb, 0.093 ppb, 0.14 ppb, and 0.27 ppb, respectively. We compare a steady state and a time dependent calculations of the dependence of ?PNs on aldehydes, OH, NO and NO₂ showing that the steady state calculations of are be accurate to ±30% between 10:00 a.m. and 06:00. We use the steady state calculation to investigate the composition of ?PNs and the concentration of OH at Granite Bay. We find that PN molecules that have never been observed before make up an unreasonably large fraction of the ?PNs unless we assume that there exists a PAN source that is much larger than the acetaldehyde source. We calculate that OH at the site varied between 1 and 6×10⁶ molecules cm^?3 at noon during the 8 weeks of the experiment.

Domaines: Océan, Atmosphère

P. A. Cleary, P. J. Wooldridge, D. B. Millet, R. C. Cohen, M. Mckay, et al.. Observations of total peroxy nitrates and aldehydes: measurement interpretation and inference of OH radical concentrations. Atmospheric Chemistry and Physics Discussions, 2006, 6 (6), pp.12929-12965. ⟨hal-00302356⟩