Abstract
Groundwater contamination by nitrate-nitrogen has become one of the most serious environmental problems in the Gunma Prefecture of Japan. This study examined the effects of atmospheric nitrogen deposition on groundwater contamination. To estimate the amount of dry deposition of nitrogen compounds, we determined the concentrations of atmospheric nitrogen compounds at four sites in areas of different land use. By using the inferential method, we estimated the amount of dry deposition of nitrogen compounds to be 0.46 t-N/km2/yr, with nitric acid (HNO3-N) and ammonia (NH3-N) accounting for 47% and 21%, respectively. We previously estimated the amount of wet deposition of nitrogen compounds to be 1.68 t-N/km2/yr. Consequently, the total amount of atmospheric nitrogen deposition was estimated to be 2.14 t-N/km2/yr. This accounts for 24% of the total nitrogen load (including agriculture, livestock, industry sewage, and domestic sewage) in the groundwater.
