铁铝氧化物对BaCl_2-TEA法测定土壤交换性酸的影响

Effect of Fe/Al Oxides on Measurement of Soil Exchangeable Acidity by BaCl_2-TEA Extraction Method

【目的】本文探讨了铁铝氧化物对BaCl_2-TEA提取法测定土壤交换性酸结果准确性的影响。【方法】采用BaCl_2-TEA法测定了添加6种不同铁铝氧化物(无定型铁、α-Fe_2O_3、针铁矿、无定型铝、γ-Al_2O_3和三水铝石)后酸性紫色土的交换性酸含量。【结果】相比于α-Fe_2O_3、三水铝石、γ-Al_2O_3和针铁矿,化学活性较高的无定型铁和无定型铝具有较低的pH值和存在大量的Fe3+或Al3+溶出,酸性环境和Fe3+或Al3+的存在会消耗更多的TEA,造成计算得到的土壤交换性酸含量偏高。【结论】由于Al3+是致酸离子而Fe3+是干扰离子,因此不宜采用BaCl_2-TEA法测定无定型铁或Fe3+含量较高的酸性土壤的交换性酸含量。此外,对无定型铝存在的潜在酸化风险也应引起重视。

[ Objective] This paper aimed to study the effect of Fe/Al oxides on the measurement of soil exchangeable acidity by BaCl2-TEA extraction method. [ Method ] Six kinds of Fe/Al oxides （ Amorphous Fe （OH） 3, α-Fe2O3, Goethite, Amorphous Al （OH） 3, γ-Al2O3 and Gibbsite） were added into the acid pmple soil, and the corresponding soil exchangeable acidity by BaCl2-TEA extraction method was measured. [ Result] Compared to α-Fe2O3, Gibbsite, γ-Al2O3 and Goethite, the addition of Amorphous Fe （OH）3 and Amorphous Al （OH）3 increased the testing result of soil exchangeable acidity significantly, the pH values of Amorphous Fe（OH） 3 and Ammphous AI（OH） 3 suspensions were low and the content of Fe3 ＋ and Al3 ＋ in Amophous Fe（OH） 3 and Amorphous AI（OH）3 minerals because the high chemical activity of amophous mineral was high, which induced the excessive consumption of TEA, and the calculated content of soil exchangeable a- cidity was higher than the reality. [ Conclusion] The Al3 ＋ increased the content of soil exchangeable acidity, but the Fe3 ＋ disturbed the measurement of soil exchangeable acidity. It was unreasonable to measure the soil exchangeable acidity by BaC12-TEA extraction method ff the soil had the high content of Fe3 ＋ or Amorphous Fe（OH）3- In addi60n, there was higher potential acidified risk ff soil had the high con- tent of Amorphous AI（OH） 3.