探討數種台灣土壤正磷酸鹽與環己六醇磷脂之競爭吸附

Abstract

本篇研究探討十二種台灣耕地表土之正磷酸鹽與環己六醇磷脂之吸附特性和兩者之間的競爭性吸附。 正磷酸鹽的吸附經過震盪50小時後幾近平衡，接下來的吸附將以此為平衡時間。正磷酸鹽的吸附曲線適合以Langmuir方程式來描述。以Langmuir 方程式所求出土壤對正磷酸鹽之最大吸附量會與pH值、CBD萃取鐵鋁、草酸銨鋁呈現顯著相關。當土壤溶液pH值介於4~10時，酸性土壤之正磷酸鹽吸附量會隨著pH值升高而下降。然而，當土壤溶液pH值介於5~7時，石灰質土壤的正磷酸鹽吸附量會隨著pH值升高而下降，但pH值高於7時，正磷酸鹽吸附量會隨著pH值升高而升高。 IHP在中性與鹼性土壤中的吸附量極高，可能與IHP與鈣發生沉澱有關。經由過氯酸鈉置換處理後的土壤，其等溫吸附曲線亦適合以Langmuir方程式來描述。而以Langmuir方程式求出之最大吸附量僅與CBD萃取鐵、草酸銨鋁有顯著相關。土壤對IHP最大吸附量比正磷酸鹽還大。而在pH值部份，對IHP之影響相似於正磷酸鹽。 IHP會對正磷酸鹽的吸附造成影響。而這兩種磷在土壤的吸附位置明顯的相同。這種有意義的現象需再做更進一步的探討。

The sorption of inorganic orthophosphate (Pi) and inositol hexaphosphate (IHP) on twelve surface soils from arable land in Taiwan was studied in this thesis. Emphasis was laid on the competitive sorption between these two phosphates. The sorption of Pi on most of soils was nearly complete after 50 hours and the subsequent sorption experiments were done in this period. Sorption isotherms for Pi in soils could be well described by the Langmuir equation. The sorption maxima obtained by nonlinear curve fitting to Langmuir equation were shown to correlate significantly with the soil pH, CBD-extractable iron and aluminum, and oxalate extractable aluminum. The sorption of Pi on acid soils was shown to decrease with the increase of solution pH in the ranges of pH 4 to pH 10. However, the sorption of Pi on calcareous soils was shown to decrease with the increase of solution pH from pH 5 to pH 7 and then to increase with the increase of solution pH above pH 7. The sorption amounts of IHP on neutral and alkaline soils were extremely high and might involve the precipitation of calcium-IHP. Sorption isotherms for IHP in soils after displacing with sodium perchlorate solution could be described fairly well by the Langmuir equation and the obtained sorption maxima were shown to correlate significantly only with the CBD-extractable iron and oxalate extractable aluminum. The sorption maxima of IHP on soils were generally higher than those of Pi. The effect of pH on the sorption of IHP on soils was similar to those of Pi. The IHP depressed the sorption of Pi. The sorption sites were apparently the same for the two phosphates. The significance of this phenomenon still need further studies.