Alkyl nitrate measurements during STERAO 1996 and NARE 1997: Intercomparison and survey of results

Citation
Ca. Stroud et al., Alkyl nitrate measurements during STERAO 1996 and NARE 1997: Intercomparison and survey of results, J GEO RES-A, 106(D19), 2001, pp. 23043-23053
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Volume
106
Issue
D19
Year of publication
2001
Pages
23043 - 23053
Database
ISI
SICI code
Abstract
Alkyl nitrates were measured over the northeastern plains of Colorado durin g the Stratospheric Tropospheric Exchange: Radiation, Aerosols and Ozone (S TERAO) 1996 campaign and over the North Atlantic during the North Atlantic Regional Experiment (NARE) 1997. Alkyl nitrate measurements were performed by two different laboratories enabling an intercomparison of analytical tec hniques. A weighted bivariate linear regression analysis of comparable samp les (National Oceanic and Atmospheric Administration versus National Center for Atmospheric Research) for the four alkyl nitrates measured by both tec hniques (2-propyl nitrate, 1-propyl nitrate, 2-butyl nitrate, and 3-pentyl nitrate) suggests there is neither a significant calibration difference nor a systematic offset. The precision of the measurements is indicated by the scatter in the correlations. Good precision is observed for the 2-butyl ni trate measurements (square of the correlation coefficient, R-2=0.90). Howev er, relatively small values of R-2 and relatively large uncertainties in th e determination of the slopes and intercepts (2 sigma confidence intervals) for 2-propyl nitrate, 1-propyl nitrate, and 3-pentyl nitrate suggest signi ficant imprecision when compared to ambient mixing ratios for at least one of the measurement techniques. Vertical profiles during NARE 1997 show high levels of alkyl nitrates in well-defined photochemical pollution layers of continental origin. A comparison of alkyl nitrate to hydrocarbon ratios wi th a sequential reaction scheme model suggests our understanding Of C-4-C-5 alkyl nitrate photochemistry is adequate to reproduce the observations. Ai r masses with larger ratios of alkyl nitrate to hydrocarbons were observed during NARE 1997 than STERAO 1996, consistent with the NARE 1997 measuremen ts being in the more remote North Atlantic. These results suggest that info rmation related to the photochemical age of an air mass can be derived from alkyl nitrate to hydrocarbon ratios.