Airborne Emissions of Mercury from Municipal Landfill Operations: A Short-Term Measurement Study in Florida

Large quantities of mercury (Hg) have 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 this Hg has not been widely studied. Using automated flux chambers and atmospheric sampling, we quantified the primary pathways of Hg vapor releases to the atmosphere at two municipal landfill operations in south Florida for eight days in April 1997. These pathways included landfill gas (LFG) releases from passive and active vent systems, passive emissions from landfill surface covers of different ages (including CH₄ "hot spots"), and emissions from daily activities at a working face (WF). Hg vapor was released to the atmosphere at readily detectable rates from all sources measured. Emission rates ranged from ~1 to 20 ng m^-2 hr^-1 over aged surface covers (generally comparable to background soils), from ~6 to 2400 ng/hr from LFG vents and flares, and from ~5 to 60 mg/hr at the WF. In general the fluxes increased from older to newer landfills, from fresh to aged cover, and from passive to active venting systems. Limited data suggest that methyl- and other organo-mercury compounds may also be emitted from these sites, suggesting an important area for future research. We estimate that atmospheric Hg releases from municipal landfill operations in the state of Florida are on the order of 10 kg/yr, or <1% of the estimated total anthropogenic Hg releases to air in this region.