Volatile organic compound concentration patterns at the New Hendersonville monitoring site in the 1995 Southern Oxidants Study in the Nashville, Tennessee, area

Abstract

Abstract. Ambient gaseous organic compounds were monitored on an hourly basis with an automated gas chromatograph from June 15 to 27, 1995, at the New Hendersonville site near Nashville, Tennessee, as part of the Southern Oxidants Study (SOS). These compounds and their estimated average contributions to the total were as follows: isoprene (2.1 ppbC), methyl vinyl ketone (1.1 ppbC), methacrolein (0.6 ppbC), c•-pinene plus/3-pinene (1.3 ppbC), and those nonmethane hydrocarbons, minus isoprene, monitored routinely in the Photochemical Assessment Monitoring Stations (44.6 ppbC). The sum of n-aldehydes from butanal through nonanal averaged 12.6 ppbC, where a conservative estimate of artifact n-aldehydes has been subtracted. Strong diurnal variations in the concentrations of n-aldehydes and the apparent influence of wind shifts on concentration support the existence of n-aldehydes at significant levels in the ambient air. The empirical fit to data as developed by Jobson et al. Because of the sample conditioning required to prepare air samples for gas chromatographic separation, the specific design of an autoGC is critical to preserving sample integrity of many VOCs. The sample conditioning involves several features, including (1) transport of VOCs through a manifold, (2) filtering of particulate matter, (3) ozone scrubbing to prevent reactions of ozone with cocollected VOCs, or system components leading to artifact formation, (4) water management, and (5) the method of concentrating VOCs. The transport manifold is usually heated to prevent water vapor condensation and to reduce adsorption of target gases, and various types of inlet filters are used to exclude particulate matter from entering the main air manifold. Different approaches to the use and type of ozone scrubbers is a topic area that has recently been reviewed [Helmig, 1997], although one of the conclusions is that exper-22,509

Hydrogen peroxide, organic peroxides, carbonyl compounds, and organic acids measured at Pabstthum during BERLIOZ

“…Higher aldehydes including n ‐hexanal, n ‐nonanal, n ‐decanal and have been observed in air and in emissions of various plants species [ Kotzias et al , 1997; Owen et al , 1997]. Similar concentration distributions of longer chain aldehydes can be found elsewhere [ McClenny et al , 1998; Ciccioli et al , 1993], together with the interesting detail that aldehydes higher than n ‐decanal show a much lower mixing ratio. The reason for this atmospheric phenomenon is still unknown.…”

Quantification of diesel exhaust gas phase organics by a thermal desorption proton transfer reaction mass spectrometer

“…The 143 mass signal intensity follows the daily variation of the photoproducts NO z (NO y -NO x ) and HCHO with distinct daytime maxima and early morning minima as shown in the figure. This ion may be due to nonanal which could be created through ozone reactions with organics adsorbed onto inlet line surfaces (McClenny et al, 1998). We note that aldehydes such as heptanal and octanal may yield fragment ions at m/z 97 and 111 and perhaps produce the diel pattern evident in Fig.…”

Variability-lifetime relationship of VOCs observed at the Sonnblick Observatory 1999—estimation of HO-densities

“…The origin of these normal-chain aldehydes (naldehydes) in ambient air is uncertain. Several investigators have detected a series of n-aldehydes in air at remote and rural sites (Yokouchi et al, 1990;Ciccioli et al, 1993;McClenny et al, 1998;Wedel et al, 1998), and suggest that they are derived from biogenic sources. Some of these aldehydes may be artifacts of analysis, arising from reactions of organics with ozone in the sampling stream (Pires and Carvalho, 1998), or from organic aerosols collected during sampling VOCs (Greenberg et al, 1996).…”