Abstract
Today in this country, we are concerned about the effect of acid precipitation on soil, and therefore some measure for quantitative future prediction is required. In this paper a numerical model to calculate historical change of chemical characteristics of soil at forested sites based on the assumption that acid precipitation is neutralized by cation exchange reaction and chemical weathering in soil is constructed, and the method to estimate chemical weathering rate by using the model is proposed. In this method, the assumption that acid precipitation was neutralized by only chemical weathering in the past when the effect of human activities on chemical species in rainwater and atmospheric trace materials were negligible, and the chemical weathering rate is estimated with the rule of trial and error by using the condition that the calculated chemical characteristics of soil coincide to the observed values. The application of the method to a bamboo forest in Osaka University Campus and the sensitive analysis of model parameters show that the method to estimate chemical weathering rate, proposed here, does not give remarkably different future predictions when model parameters are changed within their estimation errors with a few exceptions, and the method is considered to be a effective measure. In the application, chemical weathering was prevailing in acid neutralization in soil compared with cation exchange reaction, and the importance of the estimation of chemical weathering rate in future soil acidification prediction is suggested.
