Gaseous Nitrogen Compound Pollutants from Urban and Natural Sources

Major aspects of the circulation through the atmospheric environment of a number of gaseous nitrogen pollutants have been estimated, including source magnitudes, residual atmospheric concentrations, and scavenging processes. The compounds considered include the major nitrogen oxide pollutants, as well as ammonia and nitrous oxide. Background concentrations of the various nitrogen compounds have been estimated. In the global atmospheric nitrogen cycle, pollutant emissions of NO2 play only a minor role relative to the natural sources. The atmospheric nitrogen cycle is apparently dominated by natural emissions of ammonia, nitric oxide, and nitrous oxide. Scavenging mechanisms for removing nitrogen compounds from the atmosphere include surface reactions, the formation of nitrate and ammonium aerosols, and the biological reduction of nitrous oxide. Photochemical processes in the stratosphere are well known in the nitrous oxide cycle, but they appear to be less important than biological processes.