冻融对黑土中氧化铁形态及其活性的影响

Effect of Freeze/Thawing Cycling on Form of Iron Oxide and Its Activity in Black Soil

以东北地区典型黑土为研究对象,通过人工控温,室内模拟方法(-30℃冻结24 h、20℃融化24 h,作为一个周期,共0、1、3、6、9,5个冻融交替梯度,含水量分别为田间持水量的10%、40%、70%、100%、120%)对比研究了冻融交替下土壤中不同形态氧化铁的含量及其活性变化。结果表明:冻融次数对游离氧化铁、无定形氧化铁和晶质氧化铁含量的影响均达到极显著水平(P<0.01)。随着冻融次数的增加,游离氧化铁和晶质氧化铁含量的变化趋势相似,均表现出先降低后上升的趋势,无定形氧化铁含量呈波动式的变化趋势。黑土氧化铁中无定形氧化铁含量对冻融处理最为敏感,可以作为冻融处理对土壤氧化铁影响大小的一个较好的指标。冻融显著影响黑土氧化铁的活化度和晶胶比,随着冻融次数的增加,活化度和晶胶比均表现为波动式的变化趋势。

The effect of freeze/thawing cycling on the soil iron oxide and its activity were analyzed through artificially controlling temperature and indoor simulation. The black soil of various water contents （10%, 40%, 70%, 100% and 120% of the field capacity） collected from the northeast China, was frozen at -30℃ for 24 h, then thawed at 20℃ for 24 h, which is one freeze/thawing cycle, and the soil samples were subsequently refrozen and thawed for 0, 1, 3, 6, 9 times. The results showed that freeze/thawing cycling affected the soil free iron oxide （Fef）, amorphous iron oxide （Fen） and the crystal iron oxide （Fef-Fea） significantly at 0.01 level. With the freeze/thawing cycling increasing, the content of the Fef and the Fef-Fea decreased firstly, than increased, the content of the Fea presented fluctuant change. The amorphous iron oxide was a good indicator of the iron oxide under different freeze/thawing cycling for its stronger sensitivity. The effect of the freeze/thawing cycling on the iron oxide activity and （Fef-Fea）/ Fen was significantly, and the iron oxide and （Fef-Fea）/ Fea presented fluctuant change with the freeze/thawing cycling.