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 F3+ 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.