Outgassing from

Radon gas is formed in the process of radioactive decay of uranium. The distribution of naturally occurring radon follows the distribution of uranium in geological formations. Elevated levels have been observed in certain granite-type minerals. Residences built in these areas have the potential for elevated indoor concentrations of radon from radon gas entering through cracks and crevices and from outgassing from well water. 

Figure 8.21 Arrhenius plot of the 37Ar outgassed from the lunar anorthosite 15415 (Turner, 1972). Only steps 1-5 are taken into account in calculating the least-square straight-line...

The modeling of Ar outgassing from K-feldspars assumed to have coexisting domains with different sizes has been recently carried out by Lovera et al. (1989). This method seems very promising for the reconstruction of thermal history and vertical movements in young mountain belts. 

Zonally integrated giobai sea-air exchange fluxes for CO2 (positive fluxes denote outgassing from the ocean), (a) Effects of the gas exchange pump and the biological pumps (preindustrial). 

V. CO2 VOLUME FLUXES OUTGASSING FROM CHAMPAGNE GLASSES IN TASTING CONDITIONS... 

Influence of each type of drinking vessel on CO2 volume fluxes outgassing from it... 

Liger-Belair, G., Villaume, S., Cilindre, C., and Jeandet, P. (2009b). Kinetics of CO2 fluxes outgassing from champagne glasses in tasting conditions The role of temperature. /. Agric. Food Chem. 57,1997-2003. 

Of all the metals in the periodic table, mercury, Hg (atomic number 80), is the only one to exist as a liquid at ambient temperatures. Mercury is also volatile, which means that uncontained mercury atoms evaporate into the atmosphere. Today, the atmosphere carries a load of about 5000 tons of mercury. Of this amount, about 2900 tons are from current human activities, such as the burning of coal, and 2100 tons appear to be from natural sources, such as outgassing from Earth s crust and oceans. Since the mid-igth century, however, humans have emitted an estimated 200,000 tons of mercury into the atmosphere, most of which has since subsided onto the land and sea. It is probable, therefore, that a large portion of the mercury emitted from "natural" sources is actually the re-emission of mercury originally put there by humans over the last 150 years. 

Areas of peaks tentatively identified as B8-531, B8-1414 + B8-1945, B8-806/809 and B8-2229 (peaks 5-8 Fig. 2) were normalized to peak B8-1414/1945 = 1 (Peak 6), and the resulting profiles are shown in Fig. 7 for Lake Superior air and water, air sampled above farm soil in the southern United States [30], and a toxaphene standard. The profiles in Lake Superior surface water and air appear more similar to the toxaphene that has outgassed from farm soil than to the technical toxaphene standard, but there are differences in the profiles that cannotbe explained. Chlorobornanes B8-531 and B8-806/809 weresignifi-... 

After 36 h pumping, the amount of outgassing from the walls of a clean chamber of this volume (S = 0.3 m2 for a spherical chamber) should be low compared to leakage (see Section 4.3). It is likely, therefore, that this pressure rise is due predominantly to air in-leakage. 

For metals, ceramics and glasses, this formula is applicable for times up to 100 h or more. With polymers (e.g. PTFE, Nylon, etc.), a single set of parameters for Equation (4.9) may be insufficient to fit the observed behaviour over a given time interval and the further use of Equation (4.9) with other parameters may be necessary. Values of a cover a range from 0.2 to 1.2 but a = 1 or 0.5 are frequently found. The former value is shown for metals, glasses and ceramics and indicates desorption predominantly from the surface of the material. The value of 0.5 is associated with plastics and elastomers and indicates diffusion-controlled outgassing from the bulk. 

To treat the diffusive outgassing process quantitatively but relatively simply, outgassing from a thin (thickness (= 2d) small compared to length and breadth) sheet of material, e.g. metal, can be considered. This is shown in Figure 6.3. 

The second application concerned aspects of UHV technology. In UHV systems at equilibrium, the predominant gas load arises from the outgassing of internal surfaces. The factors influencing outgassing, including adsorption/desorption, were discussed (Examples 6.10-6.12). Outgassing from the interior of materials (diffusive outgassing), which can arise with both metallic- and non-metallic materials exposed to vacuum, was quantified in Examples 6.13-6.15. 

Planetary nebula (formed by outgassing from a star)... 

Figure 3.18 Vacuum outgassing from a bulb for adsorption manometry (left) or from the sample container of an adsorption nucrobalance (right).

The erosion yield of a polymer is typically measured by two methods (1) recession and (2) mass loss. Recession measurements are made by masking an area of a sample surface from attack and measuring the step height difference between exposed and unexposed areas. The thickness loss divided by the exposure fluence is the erosion yield. Mass loss measurements are made either by weighing a sample before and after exposure or by monitoring the mass loss in situ of a material that was coated onto a quartz crystal microbalance. Care must be taken in mass loss measurements to ensure that outgassing from the material in the vacuum of the exposure environment does not affect the results. The calculation of the erosion yield from a mass loss measurement requires knowledge of the density of the material and the surface area exposed, as well as the exposure fluence. 

Richey J. E., Melack J. M., Aufdenkampe A. K., Ballester V. M., and Hess L. L. (2002) Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416, 617-620. 

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