The behavior and long-term fate of metals in simulated landfill bioreactors under aerobic and anaerobic conditions.

The long-term behavior and fate of metals in leachate from four simulated bioreactor landfills were explored using lysimeters under both aerobic and anaerobic conditions for a maximum of 1650 days. Metal concentrations varied with time and stage of landfill activity. The behavior of selected metals (Al, As, Cr, Cu, Fe, Pb, and Zn) significantly differed between aerobic and anaerobic conditions. Leachate from the aerobic lysimeters contained greater concentrations of Al, Cu, and Pb compared to leachate derived from the anaerobic lysimeters (average concentrations of Al, Cu and Pb in the aerobic/anaerobic lysimeters were 8.47/0.78 mg/L, 1.61/0.04 mg/L and 0.10/0.03 mg/L, respectively). In the anaerobic lysimeters, As, Fe and Zn leached at greater concentrations (average concentrations of As, Fe and Zn in the aerobic/anaerobic lysimeters were 0.40/1.14 mg/L, 13.5/136 mg/L and 15.3/168 mg/L, respectively). Though no significant difference in overall Cr concentrations was observed in leachate samples from aerobic and anaerobic lysimeters, during the alkali and methane phases approximately 45% of Cr was presented as Cr(VI) under aerobic conditions, whereas no Cr(VI) was detected under anaerobic conditions.