Abstracts

Kazuhide Matsuda¹, Takaaki Honjo¹, Mao Xu¹, Taiichi Sakamoto¹

¹ Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan,

Email kmatsuda@cc.tuat.ac.jp (K. Matsuda)

Abstract

Synthesized measurements of vertical profiles and exchange fluxes of reactive nitrogen and relevant species, which are fine (PM_2.5) and course aerosol components (NO₃^– , NH₄⁺ SO₄^2-) and gas components (HNO₃, NH₃, SO₂), were carried out in a deciduous forest, suburban Tokyo.  Average vertical profiles in daytime and nighttime during the experiment showed the down ward fluxes (depositions). Differences of decreasing rates among the components were approximately in accordance with theoretical deposition velocities, except NO₃^– in PM_2.5. Decreasing ratio of NO₃^– in PM_2.5 from upper to lower canopy was significantly larger than that of SO₄^2- in PM_2.5 or NO₃^– in coarse aerosols. From the measurements by relaxed eddy accumulation, deposition velocities of NO₃^– in PM_2.5 were larger than those of SO₄^2- in PM_2.5. The large deposition velocity was possibly caused by an effect of shifts in equilibrium between aerosol phase (NH₄NO₃) and gas phase (HNO₃, NH₃) near surfaces. It was indicated that NH₄NO₃ could be quickly removed as well as HNO₃ in some conditions.