Uptake and Transformation in Atmosphere Ammonia enters the atmosphere as a result of both natural and artificial processes on the Earth's surface; there is no known photochemical reaction by which ammonia could be produced in the atmosphere (NRC, 1979).
Thermal reactions involving anhydrous ammonia and sulfur dioxide may, via heteromolecular nucleation, also result in the formation of ammonium sulfate aerosols.
Oral exposure (a) Non-protein nitrogen additives Urea and various ammonium salts have been used for several years as non-protein nitrogen sources in ruminant nutrition.
In wells drilled for research purposes and not supplying drinking-water, levels of ammonia-nitrogen in shallow (3 m) wells beneath wood and crop land usually averaged less than 2 mg/litre (Gilliam et al., 1974).
High levels of ammonia and high pH, which may occur, for example, in waste waters or fertilized fields, may inhibit nitrification and cause persistance or accumulation of ammonia and/or nitrite.
Thus, any natural or industrial process that concentrates and makes nitrogen-containing organic matter available for decomposition represents a potential source of high local concentrations of ammonia in water, air, and soil.
Ammonium compounds Ammonium compounds comprise a large number of salts, many of which are of industrial importance; ammonium chloride, ammonium nitrate, and ammonium sulfate are produced on a large scale.
The estimated ammonia contribution from the fertilizer industry was based on 1978 production figures for ammonia, ammonium nitrate, urea solutions, and urea solids, and on BPT guideline limits.
Watershed studies from pristine forests (Fisher et al., 1968), rural wood and pasture lands (Taylor et al., 1971), and heavily fertilized crop lands (Schuman & Burwell, 1974) have all shown that rainfall nitrogen, including ammonia-nitrogen, accounts for a substantial proportion (50 - 100%) of nitrogen in surface runoff.
The products of combustion are mainly nitrogen and water, but small traces of ammonium nitrate (NH4NO3) and nitrogen dioxide (NO2) are also formed.
ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION Ammonia in the environment is a part of the total biotic and abiotic nitrogen balance as represented by the nitrogen cycle.
Thermal reactions of ammonia with ozone result in the formation of ammonium nitrate, but the importance of this mechanism in the production of atmospheric ammonium nitrate aerosols is not known (NRC, 1979).
In addition to the formation of ammonium sulfate and nitrate, various ammonium surface complexes may be formed by the heterogeneous reaction of atmospheric ammonia with nitric oxide-soot surfaces in the atmosphere (NRC, 1979).
Therefore, at pH 8, and at a temperature of 25 °C, the above equation shows that 3.31% of the total ammonia in sea water exists in the non-ionized form.
Comparison of the findings of Robinson & Robbins (1971) and Söderlund & Svensson (1976) on global nitrogen balances for ammonia reveals differences and it is difficult to evaluate which is the more accurate.
In particular, the conversion of ammonium to nitrate appears to be important in the acidification of soil and water in carbonate-poor environments (Roelofs, in press; Schuurkes, in press).