The Hindu : National : U.S. power plants emit more mercury: study

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Sunday, Jul 02, 2006

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U.S. power plants emit more mercury: study

Special Correspondent

New technique helps in measuring emission more accurately

CHENNAI: Scientists using a new technique have now more accurately measured the amount of mercury emitted into the atmosphere by power plants in north-east United States.

Power plants in the U.S., according to U.S. Environmental Protection Agency, are one of the main emitters of mercury — 48 tonnes a year.

The study, undertaken by researchers at the Yale School of Forestry and Environmental Studies and published in the Journal of Geophysical Research-Atmospheres, was based on actual measurement of mercury present in the atmosphere and tracing the mercury to its source of emission using carbon dioxide as a tracer and finally calculating the emission rate.

The study found that during 2000-02, the mercury emission rate decreased by half but increased between 50 and 75 per cent in the next two years. The overall emissions during the study period were found have reduced by 20 per cent.

The overall reduction in mercury emission, according to a Yale University press release, can be attributed more to mild winters and, hence, a corresponding reduction in the need to produce more power than by other factors.

The study serves to underline the strong correlation between power plants and mercury emission.

The study was undertaken in winter as carbon dioxide, which is emitted along with mercury, would not be distorted by photosynthesis, the release said.

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