抄録
The prediction method of soil solution concentration of volcanic ash soil upon repetitive addition of acid solutions that differ in equivalent ratios of nitrate to sulfate was examined in this study. The method for prediction was composed of chemical equilibrium equation, electrical balance and conservation of mass in soil solutions. The results were summarized in the following.
1) There was a tendency of aluminum concentration upon addition of HNO3 solution > upon addition of acid mixed solution including NO3_ and SO42->upon addition of H2SO4 solution with equal soil solution pH.
2) The model adequately described accumulative release of basic cations. This shows it is ability to estimate acid buffering capacity of cation exchange and mineral weathering.
3) Concentration of monovalent anions was much higher than that of SO42- upon addition of acid solutions. It was considered that monovalent anions that remain in soil solution greatly affected decreasing process of pH and concentration change of basic cations. Therefore, it seemed that NO3-, which are difficult to be adsorbed in soil, are affected the release of basic cations and pH decreasing in soil when acid rain including NO3- and SO42- deposited to volcanic ash soil.
4) The simulation results agreed well with the measured values of pH and accumulative release of basic cations. These represent the most serious effects of the acid deposition on the soil. Therefore, parameters used in this simulation model are useful for predicting the main effects of the acid deposition on the Kanto loam subsoil.
