微生物驱动硝酸盐还原耦合亚铁氧化成矿过程的锌胁迫

Effect of Zn on Fe(II) oxidation and nitrate reduction by a denitrifying bacterium, Pseudomonas stutzeri LS-2

摘要:

[目的] 探究中性厌氧条件下，金属锌影响下硝酸盐依赖型铁氧化菌Pseudomonas stutzeri LS-2驱动的硝酸盐还原耦合亚铁氧化成矿过程机制，对深入理解中性厌氧环境中微生物亚铁氧化驱动的反硝化作用及重金属固定机制具有重要意义。[方法] 以不同Zn（II）浓度构建LS-2驱动的亚铁氧化成矿体系，分析不同体系中亚铁氧化速率、硝酸盐还原速率以及形成矿物的结构变化规律。[结果] LS-2驱动的硝酸盐还原耦合亚铁氧化成矿过程中，共存Zn（II）降低该过程中硝酸盐的还原速率和亚铁氧化速率。同时，随着Zn（II）浓度提高，抑制作用增强。微生物亚铁氧化形成的矿物通过吸附、共沉淀和离子置换等过程固定Zn（II），降低Zn（II）活性。Zn（II）浓度对形成的矿物结构有较大的影响：低浓度Zn（II）体系中，形成的矿物为纤铁矿；随着Zn（II）浓度的提高，矿物结构与结晶度都有一定程度的变化，当Zn（II）达到4 mmol/L时，形成的矿物主要为铁锌尖晶石。[结论] 明确了重金属锌对LS-2菌株反硝化及亚铁氧化过程的抑制规律，同时阐明了Zn（II）浓度对形成矿物结构的影响。研究结果有助于深入认识中性厌氧环境中重金属与微生物驱动的铁循环和反硝化过程的耦合作用，为土壤重金属污染防治提供理论支撑。

Abstract:

[Objective] The aim of this study was to investigate the effect of Zn on the Fe(II)-driven denitrification and mineralization by a denitrifying bacterium, Pseudomonas stutzeri LS-2 under neutral anaerobic conditions. The result will extend our knowledge of microbial Fe(II)-driven denitrification and its environmental behavior under anaerobic conditions. [Methods] We designed the microbial driven Fe(II) oxidation with a series of Zn(II) concentration, detected the rates of Fe(II) oxidation and nitrate reduction, and characterized the mineralogy under different conditions.[Results] The activity of the Fe(II)-oxidizing denitrifying culture was affected by the presence of Zn. The results showed that the presence of Zn inhibited the rates of nitrate reduction and Fe(II) oxidation. A low inhibition was observed at initial concentrations of Zn(II) from 0.15 to 2 mmol/L. When Zn(II) was supplemented up to 4 mmol/L, the higher inhibition was observed. In addition, the minerals during nitrate-reducing Fe(II) oxidation can efficiently remove the supplemented Zn(II), including co-precipitation, sorption and isomorphous substitution. The nitrate-reducing Fe(II) oxidation resulted in the formation of a mixture of Fe(III) minerals in the presence of different Zn(II) concentrations. The use of low Zn(II) concentration cultures enhanced the formation of lepidocrocite, while the higher concentration resulted in the formation of franklinite. [Conclusion] The results clarified the effect of Zn on the nitrate-reducing Fe(II) oxidation process, including the rates of nitrate reduction and Fe(II) oxidation, and the mineral structure. These findings increase the understanding of the relationship between the heavy metals and the bacteria-driven Fe(II) oxidation and denitrification and provide scientific support for remediation of contaminated soils by heavy metals.