氧化还原和微生物作用对沉积物中重金属迁移转化的影响

EFFECT OF REDOX CONDITION AND MICROBIAL ACTION ON HEAVY METALS TRANSFORMATION IN RESERVOIR SEDIMENTS

为探明沉积物-水界面间重金属的迁移转化机制,以西北某水库的表层沉积物为研究对象,通过控制溶解氧含量,设计了对该水库沉积物抑菌、加碳源的室内培养实验。结果表明:好氧培养28 d后,上覆水体中6种重金属浓度降低了46.3%~100%,沉积物中重金属总量均增加,其中活性态含量下降,残渣态含量上升,尤其是Cd和Pb的残渣态含量占总量比值(R/T)分别增加了33.32%和16.11%;厌氧条件下浓度变化的趋势则相反,上覆水体中Pb的浓度比初始浓度增加2.36倍。微生物作用下(加碳源),上覆水体中6种重金属浓度均低于高温灭菌处理,而沉积物中重金属总量相对增加,同时,加碳源后6种重金属的(R/T)值高于灭菌处理。说明微生物活动可使上覆水体中重金属迁移至沉积物中,且将活性态转化为风险低的残渣态,从而降低重金属对人体的危害。因此,提高水库溶解氧含量和微生物数量,对于降低沉积物中重金属活性,富集、固定重金属具有重要作用。

In order to explore the migration and transformation mechanism of heavy metals between sediment and water interface,we took the surface sediment of a reservoir in Northwest China as the research object.By controlling redox conditions,an indoor simulation experiment was designed including heat sterilization and adding carbon sources to the sediments.It was found that after 28 days of aerobic cultivation,the concentration of six heavy metals in the overlying water decreased by 46.3%~100%,and the total content of heavy metals in the sediment all increased;the content of active form of the six heavy metals decreased,and the content of residual form increased,especially the ratio of residual form content to total amount of Cd and Pb(R/T)increased by 33.32%and 16.11%respectively,compared with the original sample;under anaerobic condition,the trend of concentration change was opposite,and the concentration of Pb in the overlying water was 2.36 times higher than the initial one.Under the action of microorganisms,the concentration of six heavy metals in the overlying water was lower than that of the high-temperature sterilization treatment,while the total amount of heavy metals in the sediment was increased.At the same time,the R/T values of six heavy metals,after adding carbon source,were higher than those of sterilization treatment.This indicated that microbial activity can immobilize heavy metals,causing them to migrate from overlying water to sediments,and converting active states into low-risk residual states,thereby reducing the toxicity of heavy metals to human health.Therefore,increasing the dissolved oxygen content and microbial population in reservoirs played an important role in reducing the activity of heavy metals in sediments,enriching and fixing heavy metals.