“…Much higher 'eve1s of organic compounds have been reported for aerosols co1'ected off the coast of Africa. Simoneit (1980) found up to '0 n':J/m3 of n-a'kanes, fatty acids and fatty a'coho1s; while ¡¡larty and Sa' iot ('982) found 6-13 n~/m3 of n-a1 kanes alone. In both cases, the organi c materi a1 in these aerosol s was dani nated by waxes of …”
Section: Numbersmentioning
confidence: 99%
“…Characterization of trace amounts of oryanic compounds in "c1ean air" is a problem distinctly different frOlri the Other naturally deri ved 1 ipi d-type compound cl asses found i n back~round aerosol s are: fatty ac i ds (ßar~er and Garrett, 1970 Simoneit, 1977Simoneit, , 1979Simoneit, , 1980Eichmann et al, 1979, 19dU; lV\arty et ill., Sampl i n~ ofabilospheri c parti cul ate matter for organi c compound analysis has been done primarily throu~h the use of hi-vol air sarilp1ers with lass fiber filters. Simoneit (1977Simoneit ( ,1979 has also used nylon nets to salilple large () 211m) particles in the eastern tropical Atlantic near the 1983; Schneider and Ga::osian, 1984J in order to deteriiine the particle size distribution of the organic coiapounds and whether they were associdted wi th the 1 arge sea-sal t parti cl es (mari ne source), or wi th the we report here a description of the sdmplin~ equipment, sampliii:: pro- …”
“…Much higher 'eve1s of organic compounds have been reported for aerosols co1'ected off the coast of Africa. Simoneit (1980) found up to '0 n':J/m3 of n-a'kanes, fatty acids and fatty a'coho1s; while ¡¡larty and Sa' iot ('982) found 6-13 n~/m3 of n-a1 kanes alone. In both cases, the organi c materi a1 in these aerosol s was dani nated by waxes of …”
Section: Numbersmentioning
confidence: 99%
“…Characterization of trace amounts of oryanic compounds in "c1ean air" is a problem distinctly different frOlri the Other naturally deri ved 1 ipi d-type compound cl asses found i n back~round aerosol s are: fatty ac i ds (ßar~er and Garrett, 1970 Simoneit, 1977Simoneit, , 1979Simoneit, , 1980Eichmann et al, 1979, 19dU; lV\arty et ill., Sampl i n~ ofabilospheri c parti cul ate matter for organi c compound analysis has been done primarily throu~h the use of hi-vol air sarilp1ers with lass fiber filters. Simoneit (1977Simoneit ( ,1979 has also used nylon nets to salilple large () 211m) particles in the eastern tropical Atlantic near the 1983; Schneider and Ga::osian, 1984J in order to deteriiine the particle size distribution of the organic coiapounds and whether they were associdted wi th the 1 arge sea-sal t parti cl es (mari ne source), or wi th the we report here a description of the sdmplin~ equipment, sampliii:: pro- …”
“…In contrast to inorganic aerosol, carbonaceous compounds do not retain their molecular identity as they are transported from a source to a receptor. Frequently only a small fraction (about 5%) can be identified on a molecular basis (Lamb et al, 1980). As a result, carbonaceous aerosols are empirically characterized by their solubility in various solvents, their volatility as a function of temperature, and their functional groups as determined by infrared or mass (Schuetzle et al, 1975) spectroscopy.…”
“…9), but nearly all of them were designed with measurements in polluted areas in mind and are not sufficiently sensitive for measurements in clean air. Very few procedures sensitive enough for the analysis of light hydrocarbons in unpolluted air are reported (e.g., refs.…”
SUMMARYBy far the most abundant hydrocarbon in unpolluted air is methane (mixing ratio ca. 1.6 ppm). The mixing ratios of other hydrocarbons are typically in the low parts per 10 9 (ppb) and parts per 10 12 (ppt) ranges. Although methane is several orders of magnitude more abundant in clean air, it is conceivable that other hydrocarbons are still of considerable importance to clean air photochemistry, because their reaction with hydroxyl radicals proceeds much faster than that of methane.Owing to this high reactivity of many of the light non-methane hydrocarbons (NMHC), mixing ratios of NMHC as low as a few ppb or several ppt can have a considerable influence on the photochemistry of unpolluted air. For this reason a gas chromatographic method has been developed that permits the determination of several C 2 -C S hydrocarbons with detection limits of a few ppt from grab samples of 0.5-2 dm 3 (STP).The samples are collected in evacuated 2-1 stainless-steel containers with metal bellows-sealed stainless-steel valves. These sample collection and storage cans are specially pre-treated and cleaned to avoid changes in sample composition during transport of the samples to the laboratory. In the laboratory the samples are analysed by enrichment of the hydrocarbons on a packed pre-column at sub-ambient temperatures (ca. -35°C) and subsequent separation on a 7 m x O.8mm LO. packed column (Spherosil XOB 075). A flame-ionization detector is used. This method allowed survey measurements on a global scale of C 2 -C S hydrocarbons. which gave an estimate of the contributions of light hydrocarbons to atmospheric photochemical reactions.
INTRODUCTIONWith a mixing ratio of about 1.6 ppm, methane is by far the most abundant hydrocarbon in unpolluted air. The mixing ratios of other hydrocarbons are several orders of magnitude lower at a few parts per 10 9 (ppb) or fractions of I ppb 1 • However. this does not necessarily mean that the non-methane hydrocarbons (NMHC) are of no importance to the chemistry of the unpolluted atmosphere. The importance of an atmospheric trace component to atmospheric photochemistry is determined not only by its abundance but also by its participation in photochemical reaction chains and cycles. According to current understanding of atmospheric chem-
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