Thousands of landfills around the nation may be serving as bioreactors, turning inorganic mercury into methylated - or organic - mercury, according to a study by researchers at ORNL. An unknown but likely significant amount of methylated mercury, which is far more toxic than inorganic mercury, is being produced in landfills as they reduce waste by generating methane. The methylated mercury is then emitted to the atmosphere along with untreated methane in the form of dimethylmercury, which can be deposited to the environment. Researchers believe this could help explain the elevated levels of methylmercury detected in rain at remote lakes in the upper midwest. Mercury, a metal that becomes more concentrated as it travels through the food chain, is dumped in landfills from an array of sources, including fluorescent bulbs, pre-1990 batteries, electrical switches, thermometers and construction waste. The research will soon be published in the journal Atmospheric Environment.
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