HR: 17:25h
AN: A22G-06    [PDF]
TI: Hydroxyl and Peroxy Radical Chemistry in Rural Central Pennsylvania
AU: * Brune, W
EM: brune@ems.psu.edu
AF: Pennsylvania State Univeristy, 503 Walker Building, University Park, PA 16802 United States
AU: Ren, X
EM: xur1@psu.edu
AF: Pennsylvania State Univeristy, 503 Walker Building, University Park, PA 16802 United States
AU: Shirley, T
EM:
AF: Pennsylvania State Univeristy, 503 Walker Building, University Park, PA 16802 United States
AU: Metcalf, A
EM:
AF: Pennsylvania State Univeristy, 503 Walker Building, University Park, PA 16802 United States
AU: Oliger, A
EM:
AF: Pennsylvania State Univeristy, 503 Walker Building, University Park, PA 16802 United States
AU: Lesher, R
EM:
AF: Pennsylvania State Univeristy, 503 Walker Building, University Park, PA 16802 United States
AU: Edwards, G
EM:
AF: NCAR Atmospheric Chemistry Division, NCAR, Boulder, CO 80303 United States
AU: Cantrell, C
EM:
AF: NCAR Atmospheric Chemistry Division, NCAR, Boulder, CO 80303 United States
AB: Atmospheric OH reactivity and hydroxyl (OH), hydroperoxy (HO$_2$) and total peroxy radicals were measured at a rural agricultural site in central Pennsylvania during May and June, 2002. The total peroxyl radicals consist of HO$_2$ + organic RO$_2$. The results for about 40 days of measurements are presented. Diurnal cycles show that the daytime maximum mixing ratios were up to 0.6 pptv (1.4x10$^7$ cm$^{-3}$) for OH, 40 pptv (9x10$^8$ cm$^{-3}$) for HO$_2$, and 45 pptv (1x10$^9$ cm$^{-3}$) for HO$_2$+RO$_2$. A box model was constructed to predict the steady state OH, HO$_2$ and HO$_2$+RO$_2$. This model used the Regional Atmospheric Chemistry Mechanism (RACM) and was constrained to the measured OH reactivity and previously measured VOC distributions. The model calculations generally agree with the radical measurements. For OH, the model is able to match the measurements for day and night, with a measured-to-modeled ratio of 0.87 on average. Nighttime OH was reproduced surprisingly well, perhaps because the largest OH source was HO$_2$+NO. The measured-to-modeled ratio for HO$_2$ is 1.0 on average, although daytime HO$_2$ is under-predicted by about 3 pptv while nighttime HO2 is over-predicted by about 2 pptv. The average measured and modeled HO$_2$+RO$_2$ agree well during daytime, but the modeled value was twice the measured value during nighttime. Measured HO$_2$+RO$_2$ was about 1.5 times larger than measured HO$_2$ in daytime and 1.5-2.0 times larger at night, suggesting that RO$_2$ was 0.5 to 1 times HO$_2$. The production of HO$_x$ (HO$_x$=OH+HO$_2$) during daytime was dominated by the O$_3$ photolysis and O($^1$D) + H$_2$O, while nighttime HO$_x$ production was mainly from O$_3$ + alkenes. The maximum instantaneous O$_3$ production calculated from HO$_2$ and RO$_2$ reactions with about 10 ppb hr$^{-1}$ at midday; the total daily O$_3$ production was 53 ppbv d$^{-1}$ on average.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting