Ozone 4 - The Chapman cycle Key features of the Chapman...

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The Chapman cycle
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Key features of the Chapman cycle Naturally occurring reactions for ozone formation and destruction in the stratosphere. Formation reactions O 2 + h ν→ 2 Ο Ο + Ο 2 →Ο 3 Destruction reactions O 3 + h ν →Ο 2 + Ο Ο 3 + Ο →2 Ο 2
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Key features of the Chapman cycle The steady-state concentration of ozone is determined by the O 2 concentration and the relative intensity of UVB and UVC radiation at a given altitude. A given ozone molecule “lives” anywhere from days to years, depending upon conditions. 3 x 10 8 tons of O 3 are created and destroyed each day.
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Limitations of the Chapman cycle The Chapman cycle over estimates the concentration of stratospheric ozone. Other natural pathways for ozone destruction exist. H 2 O + h ν H + OH (free radicals) 2 NO + O 3 → N 2 + 2 O 2 (NO from N 2 O from soil) When all natural sources are properly taken into account, however, observed ozone concentrations are much lower than predicted.
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Stratospheric ozone has been mapped over the globe for 80 years: weather balloons and satellites. Ozone concentrations tend to increase towards the poles (except for the Antarctic “hole”). Seasonal variations and sunspot activity also influence UV intensity and ozone production. Natural and man-made gases deplete ozone.
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Ozone 4 - The Chapman cycle Key features of the Chapman...

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