Nitrous oxide stratospheric role

Globally, the oxides of nitrogen, NO (nitric oxide), NO2 (nitrogen oxide), and N2O (nitrous oxide), are key species involved in the chemistry of the troposphere and stratosphere. NO and N2O are produced mostly by microbial soil activity, whereas biomass burning is also an important source of NO. Nitric oxide is a species involved in the photochemical production of ozone in the troposphere, is involved in the chemical produaion of nitric acid, and is an important component of acid precipitation. Nitrous oxide plays a key role in stratospheric ozone depletion and is an important greenhouse gas, with a global warming potential more than 200 times that of CO2. 

The speed at which things go in this business means that those of us who are on the fringes of it are always out of date, because by the time you have mastered the chemistry of 1979, you have replaced it widi the chemistry of 1983. So let me ask this question. There has been a great deal of emphasis here on CIO and on the role of chlorine in the ozone depletion but years ago from Paul Crutzen I learned the lesson that it was the nitrous oxide of the stratosphere and not Sherry Rowland s halocarbons that really held die control of the thing. Joking aside, the upfluxing molecules that do the damage — or do the necessary control, — what are they They are water vapor, they are methane, clearly they are synthetic halocarbons, but what is left of the statement that I had learned a few years ago that perhaps the major control is that due to N2O on its way up ... 

Nitrous oxide (N2O) is a potent greenhouse gas (approximately 200 times more effective than CO2 on a molar basis) that has also been implicated in stratospheric ozone depletion (Kim and Craig, 1990 Yoshida et al., 1989) (see Bange, Chapter 2, this volume). Currendy, N2O accounts for about 5.5% of the enhanced radiative forcing attributed to all gases in the atmosphere (IPCC, 2007). Furthermore, while the atmospheric inventory of N2O is increasing, its sources are not well understood causing a renewed interest in the role of marine ecosystems as a potential source for N2O. 

The process of dissimilatory dentrification occurs anaerobically and is mediated by bacteria that use nitrate in place of oxygen as an acceptor of electrons during respiration. The result is the formation of molecular nitrogen and nitrous oxide. The nitrous oxide plays a role in the chemistry of stratospheric ozone and is, therefore, extremely important bio-geochemically. These bacteria are heterotrophic and derive energy from the anaerobic oxidation of organic compounds. 

There are no sinks for nitrous oxide in the troposphere. Instead, all of it rises eventually in the stratosphere where each molecule absorbs UV light and decomposes, usually to N2 and atomic oxygen (90%) or reacts with atomic oxygen (10%). More details about the role of N2O as ozone-depleting species are contained in Chapter 6. 

ROLE OF NITROUS OXIDE IN STRATOSPHERE OZONE DEPLETION... 

Discuss the role of nitrous oxides in stratospheric chemistry of ozone. Discuss the relative importance of this species in ozone destruction. 

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