微生物铁还原作用对蒙脱石保存有机物的影响:以硫酸盐还原菌为例

Effects of Microbial Iron Reduction by A Sulfate-Reducing Bacterium on the Preservation of Organic Matter in Nontronite

本文研究了微生物的铁还原作用对黏土矿物有机质保存的影响。将一种有机化合物(十二氨基十二酸)插层到一种富铁的蒙脱石(绿脱石)中,利用硫酸盐还原菌(Desulfovibrio vulgaris)分别对插层前后的绿脱石进行作用,以研究该菌对绿脱石结构中Fe3+的还原作用以及层间有机物的影响。结果发现,1Desulfovibrio vulgaris能够还原这2种绿脱石结构中的Fe3+,且电子穿梭体AQDS(蒽醌-2,6-二磺酸)能够增强还原速率和程度;2硫酸盐的存在能够增加还原速率和程度,表明还原过程中生成的硫化物与绿脱石结构中的Fe3+发生了化学还原作用;3通过X射线衍射、红外光谱、总有机碳分析表明,还原后的绿脱石,其结构层内仍有大量有机物,具有一定的稳定性和保存层间有机质的能力。

Clay minerals have ability to adsorb organic matter due to their layered structures and large surface area.However,the role of microbial reduction of structural Fe（Ⅲ） in clay minerals in organic matter preservation remains unclear.In this study,we studied the effect of microbial iron reduction on the organic matter preservation in an iron-rich clay mineral nontronite.We first intercalated an organic compound （12-Aminolauric acid,ALA） into the interlayer of an iron-rich smectite （nontronite）,and then used a sulfate-reducing bacterium Desulfovibrio vulgaris to reduce structural Fe（Ⅲ） in the ALA-intercalated nontronite （ALA-NAu-2）.Our results demonstrated that：1.Desulfovibrio vulgaris was able to reduce structural Fe（Ⅲ） in NAu-2 and ALA-NAu-2,and AQDS enhanced the reduction rate and the reduction extent.2.The presence of sulfate increased the reduction rate and extent,suggesting that sulfide produced during sulfate reduction abitically reduced structural Fe（Ⅲ） in NAu-2 and ALA-NAu-2.3.The results of X-ray diffraction,Fourier transform infrared spectroscopy （FTIR）,and total organic carbon （TOC） confirmed that a large amount of ALA was still preserved in the interlayer of nontronite,implying that nontronite has the ability to preserve organic matter.