The dry deposition process of nitrogen compounds still has considerable uncertainty due to the complex compound behavior in the atmosphere. To enhance understanding of the nitric acid (HNO₃) dry deposition process that largely contributes to the total nitrogen deposition, we associate this process with the equilibrium shift of ammonium nitrate (NH₄NO₃) to HNO₃ and ammonia (NH₃) near the surface. We obtained the flux of HNO₃ and PM_2.5 components above a forest in suburban Tokyo using a relaxed eddy accumulation (REA) system incorporating the denuder/filter-pack sampling technique. We conducted continuous samplings on a weekly basis over a long-term period, from October 14, 2016 to October 3, 2018, including leafy and leafless conditions. The measured deposition velocities of fine NO₃⁻ particles were significantly (p < 0.05) larger than those of fine SO₄²⁻ particles and similar to those of HNO₃, regardless of the leafy and leafless periods. The larger deposition velocities of fine NO₃⁻ particles caused by the equilibrium shift of NH₄NO₃ were found to be similar to previous measurements at the same site. The measured deposition velocities of HNO₃ were low and included many emission cases compared to those of fine NO₃⁻ particles. The lower HNO₃ deposition velocities were associated with the equilibrium shift of NH₄NO₃ to the gas phase, causing the suppressed deposition and apparent emission of HNO₃, particularly during the leafless period. The emission of HNO₃ is possibly due to high HNO₃ concentration near the surface, which is attributed to a small removal of the leafless canopy. The turbulence enhanced both the upward and downward fluxes of HNO₃. These results will contribute to the better understanding for the dynamics of the nitrogen compounds in the atmosphere and the accurate assessment for the nitrogen deposition.

由于大气中复杂的化合物行为，氮化合物的干法沉积工艺仍具有相当大的不确定性。为了增强对硝酸盐（HNO ₃）干式沉积过程的理解，该过程对总氮沉积有很大贡献，我们将此过程与硝酸铵（NH ₄ NO ₃）到HNO ₃和氨（NH ₃）附近的平衡位移联系起来。表面。我们获得了HNO ₃和PM _2.5的通量使用放松的涡流累积（REA）系统并结合了剥蚀器/滤嘴组采样技术，在东京郊区的一片森林上方收集了一些组件。从2016年10月14日到2018年10月3日，我们在长期内每周进行连续采样，包括多叶和无叶情况。细NO的测量的沉积速度₃ ^-颗粒显著（p  <0.05）比细的SO较大_4个^2-颗粒和类似的HNO的₃，而不管多叶和无叶期间。细NO的更大的沉积速度₃ ^-引起的NH的平衡移位的颗粒₄ NO ₃被发现与以前在同一地点进行的测量相似。HNO的测量的沉积速度₃是低的，并与那些细NO的包括许多发射箱子₃ ^-颗粒。较低的HNO ₃沉积速度与NH ₄ NO ₃向气相的平衡转移有关，导致HNO _3的沉积和表观排放受到抑制，特别是在无叶期。HNO ₃的排放可能是由于表面附近的HNO ₃浓度高，这归因于无叶冠层的少量去除。湍流增强了HNO的向上和向下通量₃。这些结果将有助于更好地了解大气中氮化合物的动力学，并准确评估氮的沉积。