Stratospheric significance

Chou, C.C., W.S. Smith, H. Vera Ruiz, K. Moe, G. Crescentini, J.J. Molinar, and F.S. Rowland, The temperature dependence of the ultraviolet absorption cross sections of CCI2F2 and CCI3F, and their stratospheric significance. J Phys Chem 81, 1977. 

Spencer, J.E., and F.S. Rowland, Bromine nitrate and its stratospheric significance. J Phys Chem 82, 7, 1978. 

Stratospheric Significance of the Sulfuric Acid/Water Surface... 

Acidified water surfaces degree of surface sensitivity, 111 experimental description, 107-109 stratospheric significance, 107 sulfuric acid, 109-111 surface composition, 111-113 surface vs. bulk composition, 113-114 Adsorption... 

Typical precautions with trichloroethylene are summarized in Table 5.52. An important factor is that the vapours are much heavier than air they will therefore spread and may accumulate at low levels, particularly in undisturbed areas. Because of its volatility, releases to the environment usually reach the atmosphere. Here it reacts with hydroxyl or other radicals (estimated half-life for reaction with hydroxyl radicals is less than a week) and is not therefore expected to diffuse to the stratosphere to any significant extent. There is some evidence for both aerobic and anaerobic biodegradation of trichloroethylene. 

The stratosphere contains, however, only small amounts--a few tenths of a ppb-of chlorine free radicals of natural origin. They are produced by the decomposition of methyl chloride, CH3Q. The nitrogen oxides (NO and NO2) are more abundant and are produced in the stratosphere by the decomposition of nitrous oxide, N2O. Both CH3CI and N2O are of biological origin these compounds, released at the Earth s surface, are sufficiently stable to reach the stratosphere in significant amounts. 

In summary, biomass burning is a major source of many trace gasses, especially the emissions of CO2, CH4, NMHC, NO,, HCN, CH3 CN, and CH3 Cl (73). In the tropics, these emissions lead to local increases in the production of O3. Biomass burning may also be responsible for as much as one-third of the total ozone produced in the troposphere (74). However, CH3 Cl from biomass burning is a significant source for active Cl in the stratosphere and plays a significant role in stratospheric ozone depletion (73). 

Release of N2O to atmosphere by variety of sources no significant sinks of N2O in the troposphere have been discovered stratospheric loss estimated by model calculations. 

Nitrogen oxides also play a significant role in regulating the chemistry of the stratosphere. In the stratosphere, ozone is formed by the same reaction as in the troposphere, the reaction of O2 with an oxygen atom. However, since the concentration of O atoms in the stratosphere is much higher (O is produced from photolysis of O2 at wavelengths less than 242 nm), the concentration of O3 in the stratosphere is much higher. 

As mentioned previously, N2O plays an important role in stratospheric chemistry by providing the dominant source of NO in the stratosphere (see Section 12.5). What is more difficult to predict is how stratospheric chemistry will change as a result of continued increases in the concentration of atmospheric N2O. Early research suggested that increased N2O would lead to significant reductions in stratospheric O3. However, more current reports suggest that stratospheric NO plays a key role in "protecting" stratospheric O3 from more significant... 

The concentration of NO determines the relative importance of reaction 3, and the formation of NO2 is particularly significant since this is readily photolyzed to produce 0( P) that reacts with oxygen to produce ozone. This alkane-NO reaction may produce O3 at the troposphere-stratosphere interface ... 

Recently, there have also been some concerns over possible problems related to hydrogen gas leakage as the molecular hydrogen leaks from most containment vessels. It has been hypothesized that if significant amounts of H2 escape to stratosphere, FT free radicals can be formed due to ultraviolet radiation, which in turn can enhance the ozone depletion. However, the effect of these leakage problems may not be significant as the amount of hydrogen that leaks presently is much lower (by a factor of 10-100) than the hypothesized 10-20%. 

Another example of gas-phase catalysis is the destruction of ozone (03) in the stratosphere, catalyzed by Cl atoms. Ultraviolet light in the upper atmosphere causes the dissociation of molecular oxygen, which maintains a significant concentration of ozone ... 

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