硫酸盐还原菌作用下磁性铁氧化物的分解及磁性变化

The decompositions and magnetic variations of magnetic iron oxides with the mediation of sulfate-reducing bacteria

研究了硫酸盐还原菌作用下磁性铁氧化物分解的过程及对体系磁性的影响.实验主要考查了有/无菌及有菌+有/无硫酸盐条件下体系中物相组合、磁化率、形貌等随时间的变化.结果表明,研究使用的细菌具有以磁性铁氧化物为电子受体进行生长的能力;无硫酸盐条件下,细菌作用导致多孔磁性铁氧化物还原分解并产生超顺磁纳米微粒,相应提高体系磁化率;有硫酸盐条件下,SRB及代谢产物S2-还原分解磁性铁氧化物,生成无定形铁硫化物附着于矿物表面,体系磁化率降低.SRB—磁性铁氧化物交互作用过程中,磁化率变化受硫酸盐、矿物种类和性质的共同制约.

This study focused on the decompositions and associated magnetic variations of magnetite and maghemite with the mediations of sulfate-reducing bacterium （SRB） and its metabolites. Experiments of non-biotic, SRB without sulfate and SRB with sulfate were designed. During the experiments magnetic susceptibilities were monitored. While after the experiments solids were determined for phase assemblages and micromorphologies. The results showed that SRB applied in this study can growth using magnetic iron oxides as electron acceptors. Under sulfate-lacked condition, SRB decomposed magnetite and maghemite directly and generated some superparamagnetic particles, which increased the magnetic susceptibility of the experimental system. Under sulfate-added condition, the metabolite S2- acted as the dominant electron donor for the reductive decompositions of magnetite and maghemite. Besides, S2- also reacted with Fe2＋ to form amorphous iron sulfides, which precipitated on the surface of both bacteria and minerals. Magnetic susceptibility in such experiment was decreased rapidly. It is concluded that during the process of SRB-magnetic iron oxide interaction, the variation of magnetic susceptibility is constrained mainly by sulfate and the type and property of mineral.