土壌および Al- スメクタイトの交換性 Al とリン酸イオンの反応

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There are known contradictory reports with regard to the reactivity of phosphate with exchangeable Al. When 10 mgP/l of KH_2PO_4 was added to soils, no significant correlation was obtained between the exchangeable Al contents and the decrease in phosphate sorption due to removal of exchangeable Al. On the other hand, almost one to one relationship was obtained between exchangeable Al contents and the decrease in phosphate sorption due to removal of exchangeable Al when 0.189 M of ammonium phosphate of pH7.0 was used. The objective of this study is therefore to elucidate the reactivity of Na_2HPO_4 and NaH_2PO_4 with exchangeable Al in soils. using 2 soils with different clay mineral composition and an Al^<3+>-saturated smectite, the following conclusions were obtained. (1) Na_2HPO_4 selectively reacted with the exchangeable Al under the coexistence of active Al and Fe such as Al-humus and hydrous Fe oxides. (2) Low concentration of NaH_2PO_4 (i.e. 5mM or less) hardly reacted with exchangeable Al and mostly sorbed by active Al and Fe. (3) A decrease in the exchangeable Al of Al^<3+>-saturated smectite was much smaller than those for 2 soils, appearing that the exchangeable Al scarcely reacted with NaH_2PO_4. On the other had, the decrease in H_2PO^-_4 sorption after removal of Al^<3+> indicated that some of the exchangeable Al reacted with NaH_2PO_4. These results were possible due to the formation of ion pair like AlH_2PO^<2+>_4 in the interlayer of smectite. Thus, the above-mentioned contradictory reports can be explained by the fact that the reactivity of exchangeable Al with phosphate is strongly dependent on ionic species of phosphate.
日本粘土学会の論文
1995-07-28

土壌および Al- スメクタイトの交換性 Al とリン酸イオンの反応

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