Mercury-bearing material enters municipal landfills from a wide array of sources, including fluorescent lights, batteries, electrical switches, thermometers, and general waste; however, the fate of mercury (Hg) in landfills has not been widely studied. Using automated flux chambers and downwind atmospheric sampling, we quantified the primary pathways of Hg vapor releases to the atmosphere at six municipal landfill operations in Florida. These pathways included landfill gas (LFG) releases from active vent systems, passive emissions from landfill surface covers, and emissions from daily activities at each working face (WF). We spiked the WF at two sites with known Hg sources; these were readily detected downwind, and were used to test our emission modeling approaches. Gaseous elemental mercury (Hg 0 ) was released to the atmosphere at readily detectable rates from all sources measured; rates ranged from ϳ1-10 ng m Ϫ2 hr Ϫ1 over aged landfill cover, from ϳ8 -20 mg/hr from LFG flares (LFG included Hg 0 at g/m 3 concentrations), and from ϳ200 -400 mg/hr at the WF. These fluxes exceed our earlier published estimates. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg 0 , the entire waste mass acts as a source. We estimate that atmospheric Hg releases from municipal landfill operations in the state of Florida are on the order of 10 -50 kg/yr, substantially larger than our original estimates, but still a small fraction of current overall anthropogenic losses. INTRODUCTIONThe Florida Department of Environmental Protection (DEP) is quantifying the sources of mercury (Hg) within the state and its cycling between the atmosphere and aquatic ecosystems, especially the Everglades. While municipal incinerators are known to be important atmospheric sources, municipal landfills have not been widely studied. Hg occurs in important quantities in municipal waste; before 1994, Hg concentrations in waste were estimated to be ϳ4 mg/kg, with Ͼ80% originating from alkaline batteries. 1 Although Hg in waste is decreasing, those early wastes are, of course, still in landfills. The new five-year Research Strategy of the U.S. Environmental Protection Agency (EPA) places emphasis on noncombustion sources of Hg emissions to the environment, including landfill activities. In cooperation with the Florida DEP we quantified the primary sources of atmospheric Hg releases at two municipal landfills in south Florida in April 1997. 2 These pathways included landfill gas (LFG) releases from passive
The U.S. Department of Energy's Clean Coal Technology Demonstration Program (CCTDP) was funded by Congress to demonstrate more efficient, economically feasible, and environmentally acceptable coal technologies. Although the environmental focus at first was on sulfur dioxide (SO2) and nitrogen oxides (NOX) because of their relationship to acid precipitation, the CCTDP may also lead to reductions in carbon dioxide (CO2) emissions and in solid waste produced, relative to conventional technologies. Environmental benefits that maybe realized from clean coal technologies (CCTs) will depend upon the degree of acceptance in the marketplace achieved by each of the individual technologies. In general, technologies that replace a major portion of an existing facility (repowering technologies) show the most promise for achieving reductions in all four categories (SO2, NOX, CO2, and solid waste). Technologies that modify existing facilities by adding environmental control equipment or changing feedstocks (retrofit technologies), used singly or in combination, appear capable of achieving substantial reductions in SO2 and NOX, but in general have little effect on CO2, and only a few of these technologies appear capable of reducing solid waste. However, even if decreases in solid waste volume are not always achieved, much of the solid waste from CCTs would be dry and therefore easier to dispose of than scrubber sludge from conventional technologies.
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