A Method Estimating Dry Deposition for Assessment of Nitrogen Load on Forests in East Asia

We developed a method reasonably estimating nitrogen dry deposition (HNO 3 , NH 3 , and particulate NO 3 − and p-NH 4 + ), for assessing nitrogen load on forests in East Asia, in cooperation with the Acid Deposition Monitoring Network in East Asia (EANET). Although hourly meteorological data for the dry deposition velocity calculation is commonly requested, only monthly meteorological data has been released in virtually EANET sites. As a result, we developed the method calculating the deposition velocities based on publicly available monthly meteorological data. When considering monthly data, the calculation of the surface wetness period in a month, which has a large impact on the deposition velocities of nitrogen components, was especially considered. The developed method accurately recreated the calculated deposition velocities based on hourly meteorological data. A case study on calculating total (dry and wet) nitrogen deposition was carried out in 2019 at 22 sites in 7 countries in East Asia. The total nitrogen deposition amounts exceeded 10 kg N ha −1 year −1 in many sites in Japan and Southeast Asian sites. The risks of nitrogen load on the forest ecosystems were certainly high in mid-latitude and southeast areas in East Asia.