Ammonia, tropospheric source

We can thus conclude that the spring maximum cannot be explained either by the annual variation of source intensity at the Earth s surface or by the variation of the quantity of precipitation. It has been postulated (E. Meszaros, 1974a) that this maximum is due to the oxidation effects of tropospheric ozone, the concentration of which also has a maximum during the spring (see Fig. 13). Ozone oxidizes S02 and N02 in atmospheric liquid water (see Subsection 5.3.2) which leads to the lowering of the pH. The increase in the concentration of hydrogen ions promotes the absorption of ammonia gas from the air, as well as the transformation of insoluble mineral components (e.g. calcium carbonate) into water-soluble materials. If this speculation is correct, this process provides a non-negligible ozone sink in the... 

Table 9-3. Estimates for the Strengths of the Sources and Sinks of Ammonia (TgN/yr) in the Troposphere According to Various Authors... 

Tables 9-8 summarizes the budget of N20 in the troposphere. In addition to emanations from soils and seawater, N20 is released from polluted rivers and estuaries, as a product in the burning of agricultural wastes and biomass, and in the combustion of fossil fuels. Yet another source process of uncertain magnitude is the reaction NH2+N02— N20 + H20 associated with the oxidation of ammonia by OH radicals.

The photolysis rate of atmospheric NO2 has been measured, and its dependences upon parameters such as the solar zenith angle and the amount of cloud cover have been evaluated.The photochemistry of small molecules containing sulphur, and its implications for the atmospheric S cycle have been discussed, as has the role of stratospheric reactive nitrogen as a source for species such as NO and HNO3 in the unpolluted troposphere. Ammonia concentrations have been calculated in the atmospheres of both Earth and Saturn the far-u.v. photolysis of mixtures of NH3 with methane results in the formation of amines and nitriles, and the relevance of these results to the evolution of primitive atmospheres has been discussed. ... 

Ammonia is the primary basic gas in the atmosphere and, after N2 and N20, is the most abundant nitrogen-containing compound in the atmosphere. The significant sources of NH3 are animal waste, ammonification of humus followed by emission from soils, losses of NH3-based fertilizers from soils, and industrial emissions (Table 2.8). The ammonium (NH ) ion is an important component of the continental tropospheric aerosol. Because NH3 is readily absorbed by surfaces such as water and soil, its residence time in the lower atmosphere is estimated to be quite short, about 10 days. Wet and dry deposition of NH3 are the main atmospheric removal mechanisms for NH3. In fact, deposition of atmospheric NH3 and NH4" may represent an important nutrient to the biosphere in some areas. Atmospheric concentrations of NH3 are quite variable, depending on proximity to a source-rich region. NH3 mixing ratios over continents range typically between 0.1 and lOppb. 

The lifetime of NH3 under solar radiation is very short (2[Pg.233]

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