Dry deposition washoff and dew on the surfaces of pine foliage on the urban- and mountain-facing sides of Mt. Gokurakuji, western Japan

Dry deposition and dew components on pine foliage were measured from 1998 to 2000 on the urban- and mountain-facing sides of Mt. Gokurakuji in order to estimate the effect of anthropogenic activities to dry deposition and dew concentration on the surfaces of pine foliage. A leaf wash experiment was employed to determine the dry deposition rates on the pine foliage. The NO3− and SO42− dry deposition rates per unit surface area of pine foliage were 1.47 and 0.28 μmol m−2 h−1 respectively on the urban-facing side and 0.32 and 0.09 μmol m−2 h−1 on the mountain-facing side. Dry deposition fluxes of N (NO3−+NH4+) and S (SO42−) to the forest floors were 8.4 kg N ha−1 yr−1 and 2.8 kg S ha−1 yr−1 on the urban-facing, and 3.3 kg N ha−1 yr−1 and 1.8 kg S ha−1 yr−1 on the mountain-facing side, respectively. The higher dry deposition fluxes of N and S on the urban-facing side could be attributed to its proximity to traffic roads and the urban area. The concentrations of most ions in the dew were higher on the urban-facing side (U130) than on the mountain-facing side (M430). NO3− and SO42− concentrations in dew at U130 were 802 and 428 μeq l−1, respectively, while at M430 they were 199 and 222 μeq l−1, respectively, suggesting that higher dry deposition rates on the urban-facing side enhanced their concentrations in the dew on this side. The role of dry deposits and subsequently dissolved ones in dew on the needle surfaces is discussed in terms of pine tree damage by atmospheric depositions.