Ozone global sources

Prospero J. M., Ginoux P., Torres O., Nicholson S. E., and Gill T. E. (2002) Environmental characterization of global sources of atmospheric soil dust identified with the Nimbus 7 total ozone mapping spectrometer (TOMS) absorbing aerosol product. Rev. Geophys. 40, article no. 1002. 

The HS radical reacts with either oxygen or ozone, the latter giving the HSO radical. The oxidation processes ultimately yield SO2. The typical lifetime for atmospheric H2S is 3d. Global sources and sinks of H2S are estimated as 7.72 1.25 Tg a and 8.50 2.80 Tg a respectively, with an imbalance that was indefinable (Watts, 2000). 

Recent estimates indicate that the level of carbon dioxide in the atmosphere has increased by a third since the beginning of the industrial age, and that it contributes significantly to global warming. Other major contributors include methane, tropospheric ozone, and nitrous oxide. Methane is the principal component of natural gas, but it is also produced by other sources such as rice paddies and farm animals. Tropospheric ozone is generated naturally and by the sunlight-... 

On a global scale the air layers within a few kilometers of the earth s surface are rapidly mixed by wind action. This region is called the troposphere. Natural and manmade sources of chemicals such as CH4 and other hydrocarbons, CO, SO, NO, ozone, and chlorine are emitted into the troposphere. Most of these are removed or reacted away to form harmless products by dissolving in rain, adsorption on solids, and chemical reactions. 

Furthermore, because these reactions result in the effective removal of NOx from ozone production, by removing N02, the model also predicts that O, concentrations will decrease. Figure 7.17, for example, shows the model results for the ratio of O, (R0i) with the heterogeneous removal of N03 and N2Os included to that without these aerosol reactions. In some locations, the 03 concentrations are predicted to be as much as 30% lower than they would have been in the absence of the heterogeneous reactions. Because 03 is also the major OH source on a global scale, via its photolysis to electronically excited oxygen atoms, O( D), which react in part with gas-phase water, this also decreases the predicted OH levels. 

It is important to note that there are also some sources of O, other than emissions in populated areas. For example, episodes of increased 03 due to stratospheric intrusion do occur (e.g., see Logan, 1989). In addition, there has been a well-documented (see Chapter 14) increase in global tropospheric ozone levels on top of which the local and regional sources are superimposed. 

A few comments on nitrous oxide Nitrous oxide (NzO) is a gas produced mainly through natural sources. However, generally, motor vehicles and combustion processes contribute to its formation in urban areas. Unfortunately, it is involved adversely in the two global environmental problems it contributes to the greenhouse effect and penetrates into the stratosphere, destroying the ozone layer. 

Nitrous oxide contributes severely to global warming and the depletion of ozone in the stratosphere (Crutzen 1981, Bouwman 1996). Almost 90% of the global atmospheric N2O is formed during the microbial transformation of nitrate (NO ) and ammonia (NH ) in soils and water. In OECD countries the agricultural contribution to N2O emissions is estimated at 58% (IPCC 2001). Soils fertilised with inorganic fertilisers and manure stores are seen as the largest sources (Chadwick et al. 1999, Brown ef al. 2002). 

Fig. 1 Continental source attribution of the ozone observed on each day of 2008 at the EMEP rural monitoring station GB0049R at Weyboume on the North Norfolk coast of eastern England using ozone labelling techniques in a global and a regional photochemical model. Key regional refers to the ozone advected directly over the local- and regional-scales to the location North America to that formed over that continent and over the North Atlantic and east Pacific Asia to that formed over that continent and over the western Pacific Europe-interc to that advected intercontinentally around latitude circles and back into Europe Tropical to that from the southern hemisphere and tropics...

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