HR: 1340h
AN: A33D-1547    [Abstracts]
TI: In-Situ (MC/IC) and Remote (Long-Path DOAS) Measurements of HONO During TRAMP.
AU: Whitlow, S I
EM: sallie.whitlow@unh.edu
AF: CCRC/EOS/UNH, Morse Hall 39 College Road, Durham, NH 03824, United States
AU: Anderson, C H
EM: caseyhanderson@yahoo.com
AF: CCRC/EOS/UNH, Morse Hall 39 College Road, Durham, NH 03824, United States
AU: * Dibb, J E
EM: jack.dibb@unh.edu
AF: CCRC/EOS/UNH, Morse Hall 39 College Road, Durham, NH 03824, United States
AU: Oh, H
EM: HoonJu@atmos.ucla.edu
AF: Dept. Atmospheric and Oceanic Sciences, UCLA, 7127 Math Sciences, Los Angeles, CA 90095, United States
AU: Stutz, J
EM: jochen@atmos.ucla.edu
AF: Dept. Atmospheric and Oceanic Sciences, UCLA, 7127 Math Sciences, Los Angeles, CA 90095, United States
AB: Nitrous acid is an important component of night-time N-oxide chemistry, and provides a significant source of both OH and NO in polluted urban airmasses shortly after sunrise. Several recent studies have called for new sources of HONO to account for daytime levels much higher than are consistent with current understanding. However, measurement of HONO is problematic, with most in-situ techniques reporting higher values than simultaneous optical measurements by long-path DOAS, especially during daytime. The discrepancy has been attributed to: positive interference in the in-situ techniques, negative interference in DOAS retrievals, the difficulty of comparing the different airmasses sampled by the methods, or combinations of these. During August and September, 2006, HONO mixing ratios from collocated long-path DOAS and automated mistchamber-ion chromatograph (MC/IC) systems ranged from several ppbv during morning rush hour to daytime minima near 100 pptv. Agreement between the two techniques was excellent across this entire range during many days, giving us confidence that both instruments accurately measured HONO during this campaign. Discrepancies that were observed during some nights can be explained by vertical mixing of HONO. Daytime discrepancies during several days in late August/early September are more difficult to explain, but perhaps informative. It should be noted that in previous campaigns at South Pole (summertime) and central Greenland (springtime) HONO mixing ratios in the 10-30 pptv range from the MC/IC were suggested to be too high (compared to NO_x and OH) due to unknown interferants. The results from Houston suggest that the polar interferants either do not scale with NO_x in urban air, or are thermally labile, hence too-short lived in Houston to be significant.
DE: 0322 Constituent sources and sinks
DE: 0330 Geochemical cycles (1030)
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting