Nitrous oxide, tropospheric reaction with

Nitrous oxide (N2O) is an important greenhonse gas with a radiative forcing effect 310 times that of CO2 and a lifetime in the troposphere of approximately 120 years. Part of the N2O is converted to NO in the stratosphere, and so contributes to depletion of ozone. Nitric oxide (NO) is very reactive in the atmosphere and has a lifetime of only 1-10 days. It contribntes to acidification and to reactions leading to the formation of ozone in the troposphere, and so also to global warming. 

For the major atmospheric oxide of nitrogen—nitrous oxide—the source is biological activity at the surface, and the sink is transport into the stratosphere, where it is destroyed by photodissociation and reaction with 0( D). There are no important photochemical reactions for nitrous oxide in the troposphere. 

Nitrous oxide is inert in the troposphere its major atmospheric sink is photodissociation in the stratosphere (about 90%) and reaction with excited oxygen atoms, 0(1D) (about 10%). Oxidation of N20 by 0(1D) yields NO, providing the major input of NO to the stratosphere. We will return to this process in Chapter 5. Sources of N20 exceed estimated sinks by 3.8Tg(N)yr 1. 

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