Gases in atmosphere

REACTION WITH OH DETERMINES THE LIFETIME OF MOST GASES IN ATMOSPHERE EXAMPLES ... 

Ozima, M., Wada, N. (1993) Noble gases in atmospheres. Nature, 361, 693. 

More detailed analysis on the enhancement of CO2 transfer has been made by Emerson (1975) and Schwartz (1984) for the transfer of reactive gases in atmospheric water droplets. 

The pressure of gases, in atmospheres, is used in place of activities. If the hydrogen pressure is held at 1 atm, then, since for Equation 13.19 is de-... 

For gas flows found in conventional macroscale devices at atmospheric conditions, the flow characteristic length scale L in Eq. 1 can be orders of magnitude larger than the molecular mean free path, which is in the order of 10 m, and the Knudsen number approaches zero. For micro-and nanoscaled devices that operate with gases in atmospheric conditions, the scaling relation can be quite different. For example, for a microchannel that is one micron deep and one micron wide, the Knudsen number based on the cross-sectional dimension is then 10, which is four to five orders of magnitude larger than those typically found in macroscaled devices. 

Chemical Gas Detection. Spectral identification of gases in industrial processing and atmospheric contamination is becoming an important tool for process control and monitoring of air quaUty. The present optical method uses the ftir (Fourier transform infrared) interference spectrometer having high resolution (<1 cm ) capabiUty and excellent sensitivity (few ppb) with the use of cooled MCT (mercury—cadmium—teUuride) (2) detectors. 

Table 5. Values of the Diffusion Coefficient and of M-c/T Apc Various Gases in Air at 0°C and at Atmospheric Pressure ...

Based on gases at atmospheric pressure, 38°C, containing water vapor, air, CO2, and mist, using negative polarity electrical discharge. Recalculated from data reported in reference 176. 

A California statue requiring ha2ardous materials management was passed in 1985 (24), but guidance for compliance for industries covered by the act was not issued until 1988 (25). A revised standard, which became effective in January of 1994 (26), appHes to faciUties handling any of 128 toxic materials flammable Hquids and gases in quantities of 10,000 lb (4.54 t) or more, except where used as fuel or in atmospheric pressure, ambient temperature tanks and explosives. 

Solution of Gases in Liquids Certain gases will dissolve readily in hquids. In some cases in which the quantities are not large, this may be a practical storage procedure. Examples of gases that can be handled in this way are ammonia in water, acetylene in acetone, and hydrogen chloride in water. Whether or not this method is used depends mainly on whether the end use requires the anhydrous or the liquid state. Pressure may be either atmospheric or elevated. The... 

When a liquid or solid substance is emitted to the air as particulate matter, its properties and effects may be changed. As a substance is broken up into smaller and smaller particles, more of its surface area is exposed to the air. Under these circumstances, the substance, whatever its chemical composition, tends to combine physically or chemically with other particles or gases in the atmosphere. The resulting combinations are frequently unpredictable. Very small aerosol particles (from 0.001 to 0.1 Im) can act as condensation nuclei to facilitate the condensation of water vapor, thus promoting the formation of fog and ground mist. Particles less than 2 or 3 [Lm in size (about half by weight of the particles suspended in urban air) can penetrate the mucous membrane and attract and convey harmful chemicals such as sulfur dioxide. In order to address the special concerns related to the effects of very fine, iuhalable particulates, EPA replaced its ambient air standards for total suspended particulates (TSP) with standards for particlute matter less than 10 [Lm in size (PM, ). 

Figure 1 The solubility of the prineipal atmospherie gases in seawater, as a funetion of temperature. Units are millilitres of gas eontained in a litre of seawater of salinity 35 psu, assuming an overlying atmosphere purely of eaeh gas. Note that salinity is defined in terms of a eonduetivity ratio of seawater to a standard KCl solution and so is dimensionless. The term praetieal salinity unit , or psu, is often used to define salinity values, however. It is numerieally praetieally identieal to the old style unit of parts per thousand by weight...

Forests can act as sources of some of the trace gases in the atmosphere, such as hydrocarbons, hydrogen sulfide, NO, and NH3. Forests have been identified as emitters of terpene hydrocarbons. In 1960, Went (10) estimated that hydrocarbon releases to the atmosphere were on the order of 108 tons per year. Later work by Rasmussen (11) suggested that the release of terpenes from forest systems is 2 x 10 tons of reactive materials per year on a global basis. This is several times the anthropogenic input. Yet, it is important to remember that forest emissions are much more widely dispersed and less concentrated than anthropogenic emissions. Table 8-2 shows terpene emissions from different types of forest systems in the United States. 

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