A Geochemical Equilibrium Modeling Approach to Assessing Soil Acidification Impacts Due to Depositions of Industrial Air Emissions

Soil acidification impacts arising from depositions of industrial air emissions may become a serious environmental concern. Currently, in the literature quantitative mechanistic modeling and the experimental acid neutralizing capacity (ANC) approach and a qualitative evaluation approach classifying soils into various levels of sensitivity to acid additions have been reported to assess the long-term soil acidification impacts due to industrial air emissions. Another alternative quantitative approach proposed by this study is the geochemical modeling approach that can be used to similate an ANC curve based on relevant soil chemistry data by calculating the equilibrium distributions of chemical species in the soil solution according to the specified geochemical processes. The purpose of this syudy was essentially to illustrate the potential applications and practical utility of the proposed geochemical modeling approach to assessing soil acidification impacts due to industrial air emissions. The application of the geochemical modeling apprach was illustrated by comparisons of the experimental and simulated ANC curves for a calcareous and a noncalcareous soil representing insensitive and sensitive soil cases, respectively. Results obtained from these comparisons reveal that, in terms of producing the ANC curve for the soil solution, the geochemical modeling approach seems to perform well and produce more reliable results for calcareous soil than for noncalcareous soil. However, the approach can also be used for noncalcareous soils when the air emission rates are low and may need further testing with additional measured data for a wide range of soils other than those presented in this study.