【作者】 毛晖；

【导师】 曲东；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2005， 硕士

【摘要】 在我国的农业土壤中,水稻土占有重要地位。在水稻土中氧化铁的氧化还原过程是非常有意义的化学和生物化学过程。近年来开展的异化铁还原作用研究,使得土壤污染修复开辟了新的途径。异化铁还原是微生物利用外界Fe(III)作为电子受体,氧化体内的基质(电子供体),从而使Fe(III) 还原为Fe(II),而Fe(III) 转化为Fe(II)所释放出来的能量也被微生物捕获,用于满足生长发育的需要。因而,异化铁还原过程将有效的与土壤中有机质代谢、变价元素的形态转化过程相偶连,所以其具有重要的地学和环境意义。水稻土中异化铁还原过程又是一种复杂的微生物代谢形式,不同的电子供体和电子受体对铁还原有着深刻的影响。土壤中的Cr(VI)可以作为氧化铁还原的竞争电子物质,可能会改变微生物代谢过程中的电子流向。因此,深入研究Fe(III)——Cr(VI)体系在水稻土中的相互转化关系,探讨微生物铁还原与铬还原的机理,对于土壤污染防治与生物修复具有重要的理论和实际意义。通过厌氧恒温培养试验,研究了添加外源铁、葡萄糖和六价铬对水稻土中铁还原的影响。同时,测定了土壤中Cr(VI) 浓度的变化,探讨了Fe(III) 与Cr(VI) 还原之间的竞争关系。通过土壤中添加铬渣试验,对利用铁还原体系处理铬矿渣污染的方法进行了初步探索。试验获得以下主要结果: 1.添加碳源和氧化铁后,能有效的促进厌氧条件下水稻土中铁的异化还原过程,可显著减小土壤中Cr(VI)浓度。2.添加Cr(VI),将导致土壤中铁还原滞后,添加高浓度六价铬可显著的抑制氧化铁的还原过程。不同铬浓度对铁还原体系的影响是有所差异。其中影响差异的分界值为20mmol/L 六价铬浓度。在此浓度之上体系的铁还原被严重抑制甚至铁还原没有进行,在此浓度以内体系铁还原顺利进行但仍随铬浓度增加而抑制加强。3.铬还原的进行是否顺利与土壤中异化铁还原体系的建立有密切的关系。外源铁的加入及葡萄糖的加入促进异化铁还原,也为铬还原提供了条件。土壤中铬还原过程是参与到异化铁还原体系之中进行的。4.厌氧水稻土中Fe(III) 与Cr(VI)的竞争还原机制为:有机电子供体导致氧化铁发生微生物还原,产生的Fe(II)引起土壤中Cr(VI)的化学还原。5.加入水稻土中的含铬(VI)矿渣能够在厌氧培养条件下迅速发生还原转化,并随着体系中易还原氧化铁数量的增加,其还原速率加快。通过人为调节铁还原体系,可以促进铬矿渣中Cr(VI)的还原,为含铬矿渣的处置及Cr(VI)污染土壤的修复建立了一种新的方法体系。更多还原

【Abstract】 The paddy soil is very important in our agriculture soil. The process of iron oxide and reduce is a chemical and biochemical process which has important significance. In recent years, there has been found a new way to recover soil pollution through the dissimilatory Fe (III) reduction. The dissimilatory Fe (III) reduction is to reduce Fe (III) to Fe (II) by microbe with Fe (III) as electron acceptor to oxidate electron donor , while the microbe can grow up with energy got in this process. So the dissimilatory Fe (III) reduction has important geological and environmental significance because this process can relate with the organic metabolize and volatile element form translation. The dissimilatory Fe (III) reduction in paddy soil also is a microbe metabolize, different electron donor and acceptor can make effect on Fe (III) reduction. The flow of electron direction in this microbe metabolize process may be changed with Cr (VI) as the electron competitive in Fe (III) reduction. So, make deep research with the translated relation in Fe (III) and Cr (VI) system and discuss the mechanism of Fe (III) microbial reduction and Cr (VI) reduction have important theoritic and practical significance. Through the experiment of anaerobic constant temperature incubation, we study the effect of Fe (III) reduction through adding Fe (III)、glucose、Cr(VI). And detected the variant of Cr(VI) concentration in soil, discussed competitive relation in Fe (III) and Cr (VI) reduction. Research the way to dispose chrome slag in Fe (III) reduction system through using chrome slag as the form of adding Cr(VI) in soil. The main result we get in experiment is as follow: 1. The adding of iron oxide and carbon resource can promote Fe (III) reduction in the condition of anaerobic incubate in paddy soil and can reduce the Cr(VI) concentration in soil remarkably. 2. Adding Cr (VI) make Fe (III) reduction delay in soil. Adding high Cr (VI) concentration restrain Fe (III) reduction remarkably. Different Cr (VI) concentration have different effect on Fe (III) reduction system, found out the dividing level is 20mmol/L Cr (VI). Beyond this level Fe (III) reduction had been restrained seriously or Fe (III) reduction did not occurred; Below this level the Fe (III) reduction can occur easily but still be restrained with Cr (VI) concentration increasing. 3. Cr (VI) reduction can occur easily or not had relationship with the dissimilatory Fe (III) reduction system in paddy soil. Adding Fe (III) and glucose can promote Fe (III) reduction which offer the condition to Cr (VI) reduction. And Cr (VI) reduction in soil can take part in the dissimilatory Fe (III) reduction system. 4. The mechanism of competitive reduction in Fe (III) and Cr (VI) in the anaerobic paddy soil is:The organic electron donor make the microbia reduction and the Fe (II) that process produced make the chemical reduction of Cr (VI) in soil. 5. Adding the chrome slag can be reduced rapidly in paddy soil with anaerobic incubation and the rate of Cr (VI) reduction promote with adding Fe (III) in the system. Through the building of Fe (III) reduction system can promote the Cr (VI) reduction in chrome slag and built a new system to dispose the chrome slag and recover Cr (VI) polluted soil.更多还原