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Significance of hydrous iron oxides in enhancing P sorption of soils with the addition of sodium hydrosulfite (Na 2 S 2 O 4 )

2004; Taylor & Francis; Volume: 50; Issue: 8 Linguagem: Inglês

10.1080/00380768.2004.10408611

1747-0765

Ikuko Akahane, Masami Nanzyo, Tadashi Takahashi,

Mine drainage and remediation techniques

Abstract Phosphorus sorption (Psor) of soils is affected by redox conditions. It has been shown that Psor of lowland soils at a pH value of about 4.3 increases when a small amount of sodium hydrosulfite (Na2S2O4) is added and decreases when an excess amount of (Na2S2O4) is added to the mixture of a soil and P solution. Hydrous Fe-Al oxides, manganese dioxide (MnO2) exchangeable Ca, models of reactive components with P in soils, were examined to identify the factors responsible for the increase of Psor in lowland soils when a small amount of Na2S2O4 was added. For clarifying the contribution of the hydrous Fe-Al oxides, goethite and 7 hydrous Fe-Al oxides (Fe/Al atomic ratio: 1/0, 5/1, 2/1, 1/1, 1/2, 1/5, and 0/1) were used. The Psor of all these materials increased when they were treated with a small amount of Na2S2O4 although the increase was the smallest for the hydrous Al oxide among the 7 oxides. Thus, the hydrous Fe oxides, and Al oxide to a smaller extent, play an important role in the increase in Psor of the lowland soils treated with a small amount of Na2S2O4 The Psor of the hydrous Fe oxides was not appreciably affected by the addition of MnO2. The increase in Psor of the Ca-saturated Hachirogata soil was almost the same as that of the Nasaturated Hachirogata soil, indicating that exchangeable Ca did not affect appreciably the increase of Psor in reduced soils at a pH value of about 4.3.