Atmospheric deposition of acidifying components to a Japanese cedar forest

One-year field measurements were conducted in a Japanese cedar (Cryptomeria japonica) forest, located in Gunma Prefecture, Japan. On the basis of them meteorological and atmospheric concentration data, the dry deposition of SO2, HNO3, NO2 and HCl was estimated using the inferential method. The annual dry deposition of H+ was estimated at 721 eq ha(-1)yr(-1), which was 40% larger than the measured annual wet deposition of H+ (514 eq ha(-1)yr(-1)). Therefore, dry deposition is an important pathway for the atmospheric input of H+ to the forest in the study site. The contribution of each gas to the dry deposition of H+ was as follows: SO2, 25%; HNO3, 32%; NO2, 10%; and HCl, 33%. The extremely high contribution of HCl appeared to be caused by the high emission intensity of HCl due to waste incineration in the site region. The differences between estimated deposition and throughfall and stemflow measurements indicated that about 80% of the total deposition of H+ was taken up by the canopy.