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In [[atmospheric chemistry]], the '''Leighton relationship''' is an equation that determines the concentration of [[tropospheric ozone]] in areas [[Pollution|polluted]] by the presence of [[nitrogen oxides]]. [[Ozone]] in the [[troposphere]] is primarily produced through the [[photolysis]] of [[nitrogen dioxide]] at wavelengths (λ) less than 430 [[nanometre|nm]], which are able to reach the lowest levels of the [[atmosphere]], through the following mechanism:<ref>{{Cite book|author=John Roger Barker|title=Progress And Problems In Atmospheric Chemistry|publisher=World Scientific|year=1995|isbn=9789810221133|page=22}}</ref> | |||
: [[nitrogen dioxide|NO<sub>2</sub>]] + [[photons|hν]] ([[wavelength|λ]] < 240 nm) → NO + [[O(3P)|O (<sup>3</sup>P)]] (J<sub>1</sub>)<br> | |||
: O (<sup>3</sup>P) + O<sub>2</sub> + M → [[ozone|O<sub>3</sub>]] + M (k<sub>2</sub>)<br> | |||
: [[nitrogen oxide|NO]] + O<sub>3</sub> → NO<sub>2</sub> + O<sub>2</sub> (k<sub>3</sub>) | |||
Since O (<sup>3</sup>P) is very reactive it can be assumed to be in [[Steady state (chemistry)|steady state]], and thus an equation linking the [[concentration]]s of the species involved can be derived: | |||
: <math>[O_3]=J_1[NO_2]/k_3[NO]</math> | |||
The Leighton relationship above shows how production of ozone is directly related to the solar intensity and hence to the [[zenith angle]]. The yield of this molecule will therefore be a maximum during the day, especially at noon and in the [[summer]] season; it also demonstrates how high concentrations of both ozone and [[nitric oxide]] are unfeasible.<ref>{{Cite book|author=James Pfafflin|coauthor=Edward Ziegler|title=Encyclopedia of Environmental Science And Engineering|volume=1|year=2006|publisher=CRC Press|page=122|isbn=9780849398438}}</ref> However, NO can react with [[Peroxide|peroxyl radicals]] to give back NO<sub>2</sub> without loss of ozone: | |||
: RO<sub>2</sub> + NO → NO<sub>2</sub> + RO | |||
providing another pathway to allow the buildup of [[ozone|O<sub>3</sub>]]. | |||
This relationship is named after Philip Leighton, who wrote a significant book in 1961 describing air pollution, as recognition of his contributions in the understanding of [[troposhere|tropospheric]] chemistry.<ref>{{Cite book|author=Barbara J. Finlayson-Pitts|coauthor=James N. Pitts|title=Chemistry of the Upper and Lower Atmosphere: Theory, Experiments, and Applications|publisher=Academic Press|year=2000|isbn=9780122570605|page=266}}</ref> | |||
== References== | |||
<references/> | |||
[[Category:Atmospheric chemistry]] |
Revision as of 06:37, 2 June 2013
In atmospheric chemistry, the Leighton relationship is an equation that determines the concentration of tropospheric ozone in areas polluted by the presence of nitrogen oxides. Ozone in the troposphere is primarily produced through the photolysis of nitrogen dioxide at wavelengths (λ) less than 430 nm, which are able to reach the lowest levels of the atmosphere, through the following mechanism:[1]
- O (3P) + O2 + M → O3 + M (k2)
- NO + O3 → NO2 + O2 (k3)
Since O (3P) is very reactive it can be assumed to be in steady state, and thus an equation linking the concentrations of the species involved can be derived:
The Leighton relationship above shows how production of ozone is directly related to the solar intensity and hence to the zenith angle. The yield of this molecule will therefore be a maximum during the day, especially at noon and in the summer season; it also demonstrates how high concentrations of both ozone and nitric oxide are unfeasible.[2] However, NO can react with peroxyl radicals to give back NO2 without loss of ozone:
- RO2 + NO → NO2 + RO
providing another pathway to allow the buildup of O3.
This relationship is named after Philip Leighton, who wrote a significant book in 1961 describing air pollution, as recognition of his contributions in the understanding of tropospheric chemistry.[3]
References
- ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534