Ammonia in the atmosphere

Abstract

Ammonia in the atmosphere has been measured in order to study the source of atmospheric ammonia and the circulation of ammonia through the atmosphere and the hydrosphere. Concentration of the atmospheric ammonia over the ocean is 0.2 μg-at/m³ STP. On the other hand, over land ammonia is concentrated, which is 1.25 μg-at/m³ in August and 5.0 μg-at/m³ in February. In calm night, ammonia in the air near land surface increases with time. Thus, atmospheric ammonia is supposed to be supplied mainly from the land surface. Ammonia of anthropogenic origin is predominant in surface air over land in winter. The residence time of ammonia in the atmosphere is estimated to be about 30 days, and is rather short among most of atmospheric gases. The residence time is still too long for most of the atmospheric ammonia to be regarded as being supplied by evaporation from the ocean. In the ocean, the sink of nitrogen compounds must be the biological denitrification, which, as the result, may raise nitrogen content of aerobic sea water by only 0.03 ml/l.