Redox zones of a landfill leachate pollution plume (Vejen, Denmark)

Downgradient from an old municipal landfill allowing leachate, rich in dissolved organic carbon, to enter a shallow sandy aerobic aquifer, a sequence of redox zones is identified from groundwater chemical analysis. Below the landfill, methanogenic conditions prevail, followed by sulfidogenic, ferrogenic, nitrate-reducing and aerobic environments over a distance of 370 m. This redox zone sequence is consistent with thermodynamical principles and is closely matched by the leachate plume determined by the chloride plume distribution. The redox zone sequence is believed to be key in controlling the fate of reactive pollutants leached from the landfill.