Abstract
Sulfuric acid solution diffusions into horizontal allophanic soil column, including less than 2 mm aggregates, were measured to estimate the acid rain influences on this soil and to calculate pH diffusion coefficient. pH profile following sulfuric acid solution diffusion into this soil for 15 days was predicted by the method of mixing cell model which were combined with chemical equilibrium equations established in batch experiments. The results obtained were summarized as follows ;
1. pH profile following diffusion for 15 days was differ from smooth distributions such as water diffusion or thermal diffusion in homogenous medium. pH was changed sharply in the range of 0.3〜0.7 cm from acid solution reservoir.
2. The average soil pH diffusion coefficient obtained with sulfuric acid solution diffusion was 7×10-8cm2/s.
3. Effects on pH profile derived from proportion of soil that was concerned in reaction with acid solution and from degree of sulfuric ion adsorption expressed by Langmuir type adsorptive equation were analyzed. Sensitivity analysis with two parameters for pH profile gave suggestions that proportion of active soil had large influence on pH profile than that of sulfuric ion adsorption.
4. The results of simulations, with reduced proportion of active soil and sulfuric ion adsorption, for pH profile after 15 days had a sharp pH change similar to measured profile. Simulations were succeeded in error less than 土pH 0.1 compared with measured value.
5. Simulation results implied that advancement of pH diffusion was restricted by the formation of new and high pH boundary conditions in the neighborhood of acid solution reservoir.
