Regional atmosphere hydrocarbons

Rudolph, J., and F. J. Johnen, Measurements of Light Atmospheric Hydrocarbons over the Atlantic in Regions of Low Biological Activity, . /. Geophys. Res., 95, 20583-20591 (1990). 

Compounds that have a carbonyl moiety (group), C=0, on an end carbon (aldehydes) or middle carbon (ketones) are often the first species formed, other than unstable reaction intermediates, in the photochemical oxidation of atmospheric hydrocarbons. Aldehydes are important in atmospheric chemistry because they are second only to NO2 as atmospheric sources of free radicals produced by the absorption of light. This is because the carbonyl group is a chromophore, a molecular group that readily absorbs light and it absorbs well in the near-ultraviolet region of the spectrum to produce active species that can take part in atmospheric chemical processes. 

Effect of Pressure. The effect of pressure in VPO has not been extensively studied but is informative. The NTC region and cool flame phenomena are associated with low pressures, usually not far from atmospheric. As pressure is increased, the production of olefins is suppressed and the NTC region disappears (96,97). The reaction rate also increases significantly and, therefore, essentially complete oxygen conversion can be attained at lower temperatures. The product distribution shifts toward oxygenated materials that retain the carbon skeleton of the parent hydrocarbon. 

A definition based upon the NMHC concentration might require nonmethane hydrocarbons to contribute insignificantly to atmospheric reactivity. Such a region might still contain very low concentrations of nonmethane hydrocarbons, so long as their sum total reactivity does not significantly contribute to that of methane and carbon monoxide. This is to say, in clean air... 

Area sources of either a selected chemical or a precursor present a common problem for modeling. In particular, the rich and complex patterns of hydrocarbon emissions from general urban and industrial sources either include or might produce through atmospheric photochemical reactions some of the species on the analysis list. The treatment of such species in photochemical airshed modeling is difficult (8, 9). The effort required for any one such exercise is substantial, and the effort required for a comprehensive analysis of all urban regions relevant to this program would be prohibitive. 

G. Mitri and co-workers calculated the minimum area of hydrocarbon lakes which would be necessary to preserve the relative methane humidity in the lower regions of the atmosphere. The result was surprising the calculations indicated that only between 0.002 and 0.2% of the total surface area of Titan would be required (Mitri et al., 2007). 

The methods of evacuation offshore are dependent on the ambient environmental conditions that may develop in the area and relative distance to the mainland. Regions that experience colder ambient conditions inhibit immersion opportunities and remote offshore locations retard onshore assistance capabilities. The preferred and most expedient evacuation means from an offshore installation is by helicopter. Because of the nature of fire and explosions to affect the vertical atmosphere surrounding an offshore installation, helicopter evacuation means cannot always be accommodated and should be considered of low probability where the accommodation quarters are located on the same structure as a hydrocarbon process. 

The main purpose of this chapter is to survi atmospheric concentrations of photochemical oxidants, with emphasis on surface concentrations and the distribution patterns associated with them. The reason for that em> phasis is that the photochemical oxidants that affect public health and welfare are largely concentrated in this region. The whole subject of stratospheric ozone (and its filtering of ultraviolet light and interactions with supersonic-transport exhaust products), nuclear weapon reaction products, and halogenated hydrocarbon decomposition pr ucts is not treated here. 

Though most of the oxygen in the atmosphere has been formed by photosynthesis in plants, some is produced by photolysis of water vapour in the vacuum ultraviolet region A <200 nm. Photolysis of N2, NO, N02, NHa, CO, 002 and small aliphatic hydrocarbons (alkanes) set up complex reactions in the upper atmosphere. 

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