动水条件下沉积物-水界面微生物与铬的相互作用机理

Interaction Mechanism Between Microorganism and Cr at Sediment-water Interface under Hydrodynamic Conditions

通过沉积物-水相互作用的室内水槽模拟实验,在上覆水Cr(Ⅵ)不断更新条件下,分析了沉积物中Cr(Ⅵ)的吸附还原能力和微生物的生长特征,探讨了微生物作用下沉积物-水界面重金属铬的迁移转化机理。结果表明,在上覆水Cr(Ⅵ)浓度不断增加条件下,沉积物微生物菌落经历了初步适应期、快速增长期、竞争生长期和稳定期4个阶段。在高铬(Cr(Ⅵ)>0.1 mg·L−1)条件下,沉积物表层微生物群落主要是蜡状芽孢杆菌(Bacillus cereus)、环状芽孢杆菌(Bacillus annularis)和枯草芽孢杆菌(Bacillus subtilison)。在微生物作用下,Cr(Ⅵ)还原率稳定于47.56%左右;由于微生物作用,沉积物对铬的吸附率明显升高,可达53.63%。微生物蜡状芽孢杆菌和枯草芽孢杆菌释放的还原性酶和还原性离子将沉积物-水界面的六价铬不断还原为三价铬,在弱碱性环境中形成Cr(OH)3沉淀和络合沉淀,增大了表层沉积物中铬的含量,降低了水环境中铬的含量。研究成果对河流铬污染自净起到了理论指导和科学支撑作用。

Through the indoor flume simulation experiment of sediment-water interaction, the adsorption and reduction capacity of Cr(Ⅵ) and the growth characteristics of microorganism in sediment were investigated. Especially, the migration and transformation mechanism of Cr in sediment-water interface was discussed. The results showed that the sediment microbial colonies went through four stages: initial adaptation stage, rapid growth stage, competitive growth stage and stable stage for the increasing concentration of Cr(Ⅵ) in overlying water. Under the high concentration of Cr(Ⅵ)(>0.1 mg·L-1), the microbial communities were mainly Bacillus cereus, Bacillus annularis and Bacillus subtilison on the surface of sediment. Under the action of microorganism, the reduction rate of Cr(Ⅵ) was about 47.56%, and the adsorption rate of Cr on the sediment increased significantly, with the maximum of 53.63%. The reductive enzymes and ions released by Bacillus cereus and Bacillus subtilis reduced Cr(Ⅵ) to Cr(Ⅲ) continuously in the sediment-water interface. Then, Cr(OH)3 precipitation and complexation precipitation was formed in the weak alkaline environment, which increased Cr content in the surface sediment while reduced the content of chromium in the water environment. This study could provide a theoretical guidance and scientific support for the pollution and self purification of chromium in rivers.