Environmental Sciences Division Steve Lindberg Recent Research Projects

Airborne Organic Mercury Emissions from Municipal Solid Waste Landfills*

Mercury-bearing material has been placed in municipal landfills from a wide array of sources including fluorescent lights, batteries, electrical switches, thermometers, and general waste. Despite its known volatility, persistence, and toxicity in the environment, the fate of mercury in landfills has not been widely studied. The nature of landfills designed to reduce waste through generation of methane by anaerobic bacteria suggests the possibility that these systems might also serve as bioreactors for methylated mercury compounds. The toxicity of such species indicates the need to determine if they are emitted in municipal landfill gas (LFG). From 1997 to 2001, we conducted multiple field campaigns to measure Hg emissions from five Florida landfills. Mercury emissions were quantified using automated flux approaches using in-field near-real-time mercury analyses with a Tekran Mercury Analyzer 2537A. Mercury losses are occurring via two primary pathways; fugitive losses from the working face (Figure 1), and losses with landfill gas (LFG) emissions (Figure 2). We measured levels of total gaseous mercury (TGM) in LFG in the µg/m³ range in several Florida landfills, and proposed the possible existence of gaseous organic Hg compounds since monomethyl mercury (MMM) was identified in LFG condensate at elevated levels. Recently, we measured TGM, Hg°, and methylated mercury compounds directly in LFG from another Florida landfill. Again, TGM was in the µg/m³ range, MMM was found in condensate, and this time we positively identified dimethyl mercury (DMM) in the LGF in the ng/m³ range. Landfills represent the only identified anthropogenic source of DMM emissions to air, and may help explain the reports of MMM in continental rainfall.