Abstract
We evaluated distribution of soil thickness and soil chemistry in the western part of Tanzawa Mountains. This area is located about 50 km west of Yokohama and has been receiving atmospheric pollution and related strong acid deposition. The soil core samples (30 to 280 cm length) were collected from 89 sites within the Oomuroyama watershed (~25 km2)(elevation 525~1600 m). The bedrock of this watershed is mainly composed of Miocene tonalitic rock. Soil derived from tonalitic parent material (tonalitic soil) covers over 95% of the study area and a rest of area is blanketed by loam soil derived from the Kanto loam ejected form Mt. Fuji. The tonalitic soils show a wide range of chemical variation from bottom to topsoil layer. From C- to A0-layer, SiO2, Al2O3, CaO, K2O and Na2O systematically decrease, while higher TiO2 and P2O5 were noted at the topsoil layer. The elemental abundances of soil (normalized by Ti) suggest that up to 70 wt.% of SiO2 and 60 wt.% of Al2O3 of the parental material has leached out by chemical weathering. The GIS analysis was conducted to evaluate spatial variation of topsoil composition in the study area. The GIS data indicate that the soil developed at lower elevation has experienced higher degree of elemental leaching into surface water. This may be due to climate effect.
