Analysis of atmospheric ammonia budget for the Kanto region, Japan

The atmospheric ammonia budget using a simple box model was discussed for the Kanto region, the most densely populated area of Japan, based on the monitoring results during the second half of the 1990s. The estimation of annual (anthropogenic+agricultural) emission of NH3 in the Kanto region was 69.2 Gg N a−1; and the emission amount during the warm season (from April to September) was about 70% of the total, and during the cold season (from October to March) was about 30% of the total. The estimation of annual deposition of NHX (wet+dry) in the Kanto region was 60.8 Gg N a−1; the deposition amount during the warm season was about 70% of the total, and during the cold season was about 30% of the total. Total emission of NH3 was apparently balanced with total deposition of NHX in the Kanto region, with an area of about 40,000 km2, and the balance was confirmed in winter when a long-range transport was expected in Asia as well as in summer when a large emission of NH3 was expected. These findings suggested that emissions of NH3 from the Kanto region had a significant influence on the air quality and acidification of the environment in this area.