渗滤液污染羽中沉积物氧化还原缓冲能力研究

通过土柱模拟实验研究含水层沉积物的氧化还原缓冲能力及其在不同氧化还原带中的变化.结果表明,随着污染的加重,沉积物的氧化容量(OXC)减小,而还原容量(RDC)升高.在未受污染的沉积物中,Fe³⁺是OXC的主要组成,约占OXC的70.5%;TOC是RDC的主要组成,约占RDC的98.7%.在厌氧环境中大部分无定型态和部分晶体态Fe³⁺被还原,还原产物主要以FeCO₃和FeS形式沉淀;在产甲烷带/硫酸盐还原带和铁还原带中,Fe²⁺的沉积使得可离子交换态Fe²⁺含量由原样中的0.5%分别升高至3%和1.84%.因此Fe³⁺是含水层中主要的氧化还原缓冲剂,Fe³⁺还原、Fe²⁺沉淀和Fe2+的离子交换等作用大大减小了厌氧渗滤液污染羽的扩展,对进入含水层的还原性污染物有重要的缓冲作用.

Study on Redox Buffering of Landfill Leachate Contaminated Aquifer Sediments

A soil column filled with sandy soil was constructed to investigate redox buffering capacity of aquifer sediments and its variation in different redox zones.Results indicated that with the aggravating of landfill leachate pollution,the oxidation capacity(OXC) of sediments was decrease,and the reduction capacity(RDC) of sediments was increase.In uncontaminated aquifer sediments,Fe³⁺ was a main component of OXC,and account for about 70.5% of OXC;TOC was a main component of RDC,and account for about 98.7% of RDC.In anaerobic environment,large fraction of amorphous Fe³⁺ and part of crystalline Fe³⁺ were reduced,and the reduced product was mainly precipitated as FeCO₃ and FeS.In methanogenic zone/sulfate reduction zone and iron reduction zone,deposit of Fe²⁺ led to ion-exchangeable Fe²⁺ content increased from 0.5% of uncontaminated aquifer sediments to 3% and 1.84% respectively.Therefore,sediment-bound iron may act as a very significant redox buffer in polluted aquifer,the reduction of Fe³⁺ and fowling precipitation and ion exchange onto the sediment of Fe²⁺ substantially reduces the size of the anaerobic leachate pollution plume,which may contribute substantially to the buffering of entering reduced species.