Analysis of Ammonia Behavior in the Kanto region

Abstract

The concentration of ammonia in the lower atmosphere was observed at four selected sites, Komae, Kagurazaka, Abiko, and Akagi in the Kanto region during the period from January to December 2000. Concentrations of gaseous ammonia, ammonium salt with diameter larger than 2.5μm (coarse particulate), and ammonium salt with diameter smaller than 2.5μm (fine particulate) were measured separately by means of a diffusion denuder sampler. The seasonal variation and horizontal distribution of concentration of ammonia were analyzed on the basis of the data obtained. Emission sources, formation of fine particles, and long-range transport of ammonia in this region were also discussed.
The concentration of gaseous ammonia showed large variations among each site, and was higher in the summer season and lower in the winter season. These seasonal variations were closely connected with the changes in temperature and ensuing emission rate of ammonia from various sources. It was suggested that the atmospheric concentration of ammonia for urban sites such as Kagurazaka was affected by the emission from anthropogenic sources, and that for rural sites such as Akagi, by the emission from agricultural and livestock sources. The concentration of ammonium salt which existed as coarse particulate was higher in the winter season and lower in the summer season. The behavior of ammonium salt which existed as coarse particulate was suggested to be similar to that of soil particles such as calcium and sea salt particles such as sodium. The concentration of ammonium salt which existed as fine particulate showed no clear pattern of seasonal variation at any sites. It was confirmed that ammonium in fine particles was combined with sulfate, nitrate, and chloride. The concentration levels of gaseous ammonia and ammonium salt were almost the same, and ammonium salt mainly existed as fine particles. A high concentration of ammonium salt which existed as fine particulate was observed over the Kanto region following the eruption of Miyake-jima volcano on August 2000. It was suggested that ammonium sulfate, a reaction product of gaseous ammonia and volcanic sulfur, was transported to the Kanto region.