Gridded ammonia emission fluxes in Japan

In order to fully understand the acidification of precipitation, it is essential to determine ammonia emissions. Detailed gridded emission fluxes of NH₃ have been compiled in Europe. In East Asia they have been determined on a national basis(Zhao and Wang, 1994). In Japan we have calculated NH₃ emission fluxes on a 1° latitude × 1° longitude basis for livestock and the application of fertilizer. Livestock emission factors developed by W.A.H. Asman(Asman, 1992) for Europe were used 23.04 and 5.36 kg NH₃/animal/yr. for cattle (dairy cows and beef), and pigs, respectively. Domestic animal population data was collected by prefecture and apportioned to grid cells based on the prefectural area in each grid cell. For fertilizer emissions, NH₃ emission were calculated assuming a 10% ammonium nitrogen evaporation rate for ammonium sulfate, urea, and other nitrogen-containing fertilizers. Since prefectural fertilizer data were not available, total fertilizer usage for Japan was distributed to prefectures based on cultivated area. The maximum calculated NH₃ emission fluxes for each of the three animal categories were as follows: Dairy cows, 4730 (Hokkaido), beef cattle, 4540 (Kyushu) and pigs, 3480 (Kanto) tonnes NH₃/grid/yr. The total NH₃ emissions due to livestock in Japan were 4.6, 6.0 and 4.4 × 10⁴ tonnes NH₃/yr. from dairy cows, beef cattle and pigs, respectively. The overall total NH₃ emission from livestock and the application of fertilizer was 2.0 × 10⁵ tonnes NH₃/yr. The NH₃ emission by Japan is small compared to those of most European countries.