Troposphere biological cycle

Photoreactions are often complex reactions that not only control the fate of many chemicals in air and water, but often produce products with chemical, physical, and biological properties quite different from those of their parent compounds more water soluble, less volatile, and less likely to be taken up by biota. Photooxidation removes many potentially harmful chemicals from the environment, although occasionally more toxic products form in oil slicks and from pesticides (Larson et al., 1977). Biogeochemical cycling of organic sulfur compounds in marine systems involves photooxidation on a grand scale in surface waters, as well as in the troposphere (Brimblecombe and Shooter, 1986). 

Approximately 90% of the ozone in the atmosphere is found in the stratosphere (15-50 km), with only —10% in the troposphere (0-15 km). Stratospheric ozone is very important because it absorbs ultraviolet radiation (200-300 nm) from the Sun and shields the surface from this biologically lethal radiation. Stratospheric ozone is destroyed via a series of chemical reactions involving NO, OH, Cl, and Br. These species destroy stratospheric ozone through the following catalytic cycle where X may be any of the following NO, OH, Cl, or Br (Wayne, 1991)... 

Bioinorganic Chemistry Carbon Cycle Climatology Greenhouse Eeeect and Climate Data Nitrogen Cycle, Biological Ozone Measurements AND Trends Planetary Atmospheres Transport and Fate oe Chemicals in the Environment Tropospheric Chemistry... 

It is now recognized that this cycle is the principal means by which ozone is limited in the natural stratosphere [48]. Also, whereas ozone is an undesirable pollutant in the troposphere, in the stratosphere ozone performs the necessary function of shielding the earth s surface from biologically damaging ultraviolet radiation. 

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