Airborne Emissions of Mercury from Municipal Solid Waste. I: New Measurements from Six Operating Landfills in Florida

Abstract

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

Emissions of air-borne mercury from five municipal solid waste landfills in Guiyang and Wuhan, China

“…For the uncovered waste, our results obtained in winter 2006 (57.5-84.5 ng m −2 h −1 ) were similar to those measured in an American landfill (70±62 ng m −2 h −1 , Lindberg et al, 2005b). When compared with the mercury emission rate at local and global background sites (typically less than 30 ng m −2 h −1 ; Wang et al, 2004;Poissant and Casimir, 1998), Hg emitted from the landfill soil cover was the same or several times higher, while the uncovered waste was up to several hundreds times higher.…”

“…The emission factors for D-S, J-K and G-Y landfill were 0.04, 0.63, 6.81 mg Hg t −1 MSW disposed, respectively. These results were consistent with those from 7 American landfills (0.7-6.6 mg t −1 ; Lindberg and Price, 1999;Lindberg et al, 2005b). Hg emission factors indicated that 0.07‰-3.78‰Hg in MSW was released into ambient air through the working faces, with an average loss rate of 1.63‰.…”

“…Compared with other studies, Hg emissions from soil covers were higher than those from several landfills in Florida, USA, which ranged from 1-20 ng m −2 h −1 (Lindberg and Price, 1999; Lindberg et al, 2005b), but lower compared to a large closed landfill in Seoul, Korea, which averaged 254±224 ng m −2 h −1 (Kim et al, 2001). For the uncovered waste, our results obtained in winter 2006 (57.5-84.5 ng m −2 h −1 ) were similar to those measured in an American landfill (70±62 ng m −2 h −1 , Lindberg et al, 2005b).…”

“…3b) at different sites ranging from 8.5 to 155.7 ng m −3 . The highest TGM concentrations occurred at the working face and the downwind area for all three landfills (G-Y, J-K and D-S), where TGM was sensitive and proportional to the activities of MSW treating at the working face, as observed at operational landfills in Florida, USA (Lindberg et al, 2005b). Lowest TGM was measured at the closed landfill of X-R-J, where the whole landfill was planted with grass and trees, and this value was close to average TGM concentrations in ambient air in Guiyang (8.4 ng m −3 , from Feng et al, 2004b).…”

Release of Mercury from Broken Fluorescent Bulbs

“…5 An industry report states that only about 1% of the mercury in the bulbs is released during disposal and recycling operations. 6 Release of a much higher percentage of the mercury in discarded bulbs has been suggested by a study for Oak Ridge National Laboratory by Lindberg et al 7,8 These researchers have indicated that mercury emissions from broken fluorescent bulbs persist for at least a week and may represent 20 -80% of the mercury in the bulbs.…”