The fate and transformation of mercury in municipal solid waste landfills

Mercury is conveyed into landfills primarily via batteries and a variety of other mercury-containing devices and lamps. Mercury has not been the focal point of metals research in landfills, but the first Phase of this study showed that mercury exists in the Alachua County Landfill at concentrations ranging from 32.8 ng Hg/g to greater than 16,800 ng Hg/g. However, over half of the samples had concentrations of 150 ng/g or less. While Hg concentrations in the landfill samples as well as compost samples (1:1 yard waste to biosolids) from Palm Beach County were generally above background levels for surface soils in Florida, they were two to three orders of magnitude lower than clean-up goals currently used by the Florida Department of Environmental Protection and federal regulations governing land application of sewage sludge as described in 40 CFR Part 503.;Phase II of this study investigated the fate of mercury in simulated landfills and found that the bulk of the Hg added was found in the solid waste. Sixteen out of 18 leachate samples did not have detectable levels of Hg. The percentage of Hg volatilized during anaerobic digestion ranged from over 30% at the lowest Hg level (100 ng Hg per 60 g solid waste) to about 3% at the highest Hg level (2000ng Hg per 60 g solid waste). Evidence was obtained that forms of Hg other than elemental or divalent Hg were volatilized. These other forms were thought to be organic Hg compounds, quite possibly including dimethylmercury.;Sulfur-impregnated, activated charcoal was used to trap Hg volatilized during anaerobic digestion. A modification of EPA Method 7471 successfully recovered ;This study has implicated landfills as a potential source of mercury to the atmosphere. Further research should focus on quantifying the amount of mercury being emitted into the atmosphere from landfills and identifying those stages during anaerobic digestion of MSW that Hg is most likely to volatilize.