Spatial Variation of Nitrogen Deposition to Experimental Forests and its Wet and Dry Deposition

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The temporal and spatial variations of wet deposition of nitrate and ammonium ions were explored together with corresponding variables at three close stations, Tama, Fussa, and Hinohara, of Tokyo Metropolitan Government network. No significant temporal variations were discernible for nitrate or ammonium concentration. Volume-weighted monthly mean concentrations, however, were 42.8 and 38.2μ mol L-1 for nitrate and ammonium, respectively, which were significantly higher than those of Tokyo results by factors of 1.6 to 1.9 and 1.5 to 2.1. Particularly nitrate concentration is surely higher than that at Tama station. A recent intensive field measurement of nitrogen oxides and ozone in this experimental station shows that nitrogen oxide, NO, reached zero during night time, which might enhance nitrate species formation from N205 because ozone reacts with NO2 to form NO3 radical. Wet deposition of nitrate and ammonium ions at Tama was in the top 30% of the deposition in Japan. An observational tower was intended to construct for the dry deposition studies. Although the studies with the use of the experimental tower were delayed because of some needed improvements, preliminary studies have developed into some routine measurements with the improved tower.