Nonmethane hydrocarbons source

At levels of nonmethane hydrocarbons where their reaction rates with HO are a significant fraction of the reaction rate of HO with CO and methane, it may happen that the clean-air HO concentration remains unchanged. This would result if the increase in HO removal by NMHC s is compensated by increasing HO sources such as aldehyde or ketone photolysis and reactions such as R21. These considerations are examined below. 

Rockmann, T C. A. M. Brenninkmeijer, P. Neeb, and P. J. Crutzen, Ozonolysis of Nonmethane Hydrocarbons as a Source of the Observed Mass Independent Oxygen Isotope Enrichment in Tropospheric CO, J. Geophys. Res., 103, 1463-1470 (1998). 

Mass Spectrometry. The use of a quadrupole mass spectrometer as a GC detector for nonmethane hydrocarbon analysis has come of age in recent years. Development of capillary columns with low carrier gas flows has greatly facilitated the interfacing of the GC and mass spectrometer (MS). The entire capillary column effluent can be dumped directly into the MS ion source to maximize system sensitivity. GC-MS detection limits are compound-specific but in most cases are similar to those of the flame ionization detector. Quantitation with a mass spectrometer as detector requires individual species calibration curves. However, the NMOC response pattern as represented by a GC-MS total ion chromatogram is usually very similar to the equivalent FID chromatogram. Consequently, the MS detector can... 

Swinnerton, Linnebom and Cheek (239) and Seiler and Junge (226) reported that the ocean, which they found to be supersaturated with CO, might be an important source. It is also possible that the oxidation of nonmethane hydrocarbons, particularly those whose production occurs over land, may be another huge source. Since, as we will see later, methane is thought to have a uniform distribution throughout the troposphere, some... 

Table 6-4. Hydrocarbon Emissions from Anthropogenic Sources (a) In the United States, Including Methane (Environmental Protection Agency, 1976 Mann, 1981) (b) On a Global Scale, Nonmethane Hydrocarbons Only (Ehhalt et al., 1986) (c) Source Apportionment in Sidney, Australia (Nelson et al., 1983)...

Table 6-6. Summary of Global Emission Rates of Nonmethane Hydrocarbons from Various Sources...

The global sources and sinks of CO are given in Table 2.14. Methane oxidation (by OH) is a major source of CO, as are technological processes (combustion and industrial processes), biomass burning, and the oxidation of nonmethane hydrocarbons. Uncertainties in each of these estimated sources are large. It is estimated that about two-thirds... 

Catalytic oxidation of trace contaminants in air also has been used in analytical chemistry. One process to date has been developed to analyze for total nonmethane hydrocarbons emissions from stationary sources (EPA Method 25). This technique involves drawing a gas sample containing hydrocarbons over a catalyst and oxidizing the hydrocarbons to CO, which is then measured. The best catalysts for this process were found to be Pt or Pd on alumina. ... 

Ketones are emitted directly to the atmosphere, and their sources were discussed in detail in chapter I. In the U.K. acetone and butanone comprise about 1% and 5%, respectively, of the total anthropogenic emissions of oxygenated compounds, and 1.6% and 1.1%, respectively, of the total anthropogenic emissions of nonmethane volatile organic compounds. Ketone emissions from solvents (both industrial and personal) are substantial emissions from both gasoline- and diesel-fueled vehicles also contribute. Ketones are also formed extensively in the atmosphere in the oxidation of other compounds. Acetone, for example is formed in the OH-initiated oxidation of propane, iio-butane, iso-pentane, and neopentane and from a number of higher hydrocarbons. It is also formed in the oxidation of terpenes. The distribution, sources, and sinks of acetone in the atmosphere have been analyzed by Simpson et al. (1994). Methyl vinyl ketone is an important first generation product in the OH-initiated oxidation of isoprene. 

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