| ECOLOGY |
Organic Mercury From Landfills Bacteria in the sediments of aquatic ecosystems are not the only producers of toxic methylated mercury compounds. A recent study shows that anaerobic bacteria in landfills also produce methylated mercury species, which are released into the air. Mercury in landfills comes from many sources, including fluorescent bulbs, alkaline batteries, electrical switches, thermometers, and construction waste. Although the Environmental Protection Agency has set standards for mercury emissions from waste incinerators and combusters, no standards exist for landfill emissions. What happens to the mercury in landfills has not been widely studied. Authors show that landfills could be a source of organic mercury emissions to the atmosphere. Their measurements show dimethylmercury present in nanogram-per-cubic-meter levels in gas from two Florida municipal landfills. Dimethylmercury is toxic, volatile, and directly absorbable through the skin. In air, it quickly breaks down to monomethylmercury--CH3Hg+--which is the organic mercury species that accumulates in fish and is commonly referred to as methylmercury. Methylmercury is highly water soluble and could deposit locally and regionally by wet or dry processes. "These are the first measurements showing the atmospheric emission of anything other than inorganic mercury from any waste source as far as I know author says. "Landfills are certainly bioreactors. And it has been speculated, but never demonstrated until now, that methylated mercury species could be formed in them. As much as 50% of the landfill gas in the U.S. is not treated in any way, so any dimethylmercury produced would be emitted." The studies also provide a possible explanation for methylated mercury species that appear to originate in rain. Methylated species from landfill gas are "a reasonable source, the first ever demonstrated |
| UPDATE | 09.01 |
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