Major chemical forms of inorganic phosphate in Japanese farmland soils are phosphates sorbed by ac-tive Al and Fe under oxidizing conditions. Young volcanic ash soils and granitic soils contain apatite. The apatite re-acts with active Al in young volcanic ash soils after grad-ual formation of active Al. Dividing the Japanese farm-land soils into Andosols and lowland soils, phosphate is mainly sorbed by active Al in Andosols whereas by ac-tive Fe in lowland soils. A crystalline precipitate of phos-phate, vivianite, is formed under reducing conditions in the submerged lowland paddy field soils although Vivian-ite dissolves and the phosphate is sorbed by active Fe af-ter drainage. Other crystalline phosphates may be formed only under somewhat special conditions.
The term “adsorption” represents the accumu-lation of dissolved species on mineral surfaces or the re-moval of dissolved species on existing minerals. When the minerals are added to the solutions with trace elements,certain amounts of trace elements are removed by the min-erals while rests of trace elements are remained in the so-lutions. Researchers, who are interested in the adsorption of trace metals on minerals, desire to understand and pre-dict the adsorption behavior, quantitatively. In this paper, I review the methodologies to model the adsorption behav-iors.
In this paper, pH buffering reaction by soil com-ponents is explained to renew soil scientist’s and engineer’s awareness of importance for chemical reaction in soil and role of minerals to the reaction. This paper also contains an overview of engineering importance for understanding of pH buffering reaction in soils to realize availability of geo-chemical modeling. One of case studies in applied geo-chemical modeling by the authors is also introduced to
show how to determine a pH buffering reaction capacity of soil.