硫酸盐还原菌修复污染土壤过程中镉的地球化学形态分布变化

Changes of cadmium geochemical speciation in the process of soil bioremediation by Sulfate-Reducing Bacteria

利用Tessier五步连续提取法作为分析手段,研究了硫酸盐还原菌对不同污染程度土壤中镉的地球化学形态分布的影响.研究结果表明,在受镉污染的土壤中,可交换态是镉存在的主要形态.土壤中镉在硫酸盐还原菌的作用下,总量没有发生变化,但地球化学形态发生显著变化,从不稳定的可交换态转化为更加稳定的铁锰氧化物结合态,可交换态的去除率可达60%～80%;镉形态的变化使土壤中镉的生物可利用性发生了明显的变化,易利用态的比例明显下降,达到了修复效果.在修复过程中,镉对硫酸盐还原菌活性的抑制作用不同.利用硫酸盐还原菌修复重金属污染的土壤,具有修复效率相对较高、技术简便的优点,是一种有广阔应用前景的修复方法.

The five-step Tessier sequential extraction method was used to investigate the changes of Cd distribution in different geochemical phases in the process of bioremediation by Sulfate-Reducing Bacteria（SRB）.We found that the exchangeable phase is the dominant pool of Cd in contaminated soils（45%-60% of the total Cd）.In the process of bioremediation,the SRB removed 60%-80% of Cd in the exchangeable phase,but had little effect on the total Cd concentrations in the soils.At the same time,the distribution of Cd in different geochemical phases changed remarkably,being mainly transformed from the exchangeable phase to the Fe-Mn oxides phase,in which Cd was more refractory.The change of Cd speciation led to a decrease of Cd toxicity and bioavailability due to the decreased distribution of Cd in the more bioavailable phase.In addition,the sulfate reduction rate was negatively correlated with Cd concentrations in soils while the extent of Cd removal from the exchangeable phase was positively correlated with Cd concen The five-step Tessier sequential extraction method was used to investigate the changes of Cd distribution in different geochemical phases in the process of bioremediation by Sulfate-Reducing Bacteria（SRB）.We found that the exchangeable phase is the dominant pool of Cd in contaminated soils（45%-60% of the total Cd）.In the process of bioremediation,the SRB removed 60%-80% of Cd in the exchangeable phase,but had little effect on the total Cd concentrations in the soils.At the same time,the distribution of Cd in different geochemical phases changed remarkably,being mainly transformed from the exchangeable phase to the Fe-Mn oxides phase,in which Cd was more refractory.The change of Cd speciation led to a decrease of Cd toxicity and bioavailability due to the decreased distribution of Cd in the more bioavailable phase.In addition,the sulfate reduction rate was negatively correlated with Cd concentrations in soils while the extent of Cd removal from the exchangeable phase was positively correlated with Cd concentrations.This study provides mechanistic information about the changing of Cd geochemical speciation by SRB,and at the same time highlights the advantages of using SRB in soil bioremediation,considering their high efficiency and simple manipulation.