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

摘要

We describe measurements of total peroxy nitrates (ΣPNs), NO₂,O₃ and several aldehydes at Granite Bay, California, during theChemistry and Transport of the Sacramento Urban Plume-2001 (CATSUP 2001)campaign, from 19 July–16 September 2001. We observed a strong photochemicallydriven variation of ΣPNs during the day with the median of 1.2 ppbat noon. Acetaldehyde, pentanal, hexanal and methacrolein had medianabundances in the daytime of 1.2 ppb, 0.093 ppb, 0.14 ppb, and 0.27 ppb,respectively. We compare steady state and time dependent calculations of thedependence of ΣPNs on aldehydes, OH, NO and NO₂ showing thatthe steady state calculations are accurate to ±30% between 10:00 and18:00 h. We use the steady state calculation to investigate the compositionof ΣPNs and the concentration of OH at Granite Bay. We find that PNmolecules that have never been observed before make up an unreasonably largefraction of the ΣPNs unless we assume that there exists a PAN sourcethat is much larger than the acetaldehyde source. We calculate that OH atthe site varied between 2 and 7×106 molecule cm−3 atnoon during the 8 weeks of the experiment.