A TOXIC rain of mercury falls on the Arctic every spring, a study by researchers in Canada suggests. They say chemical reactions similar to those that destroy ozone are turning mercury vapour in the atmosphere into particles that fall to Earth.
Mercury, alone among major heavy-metal pollutants, has a boiling point low enough for it to be blown around the world as a gas. Mercury vapour is widespread in the atmosphere especially at the poles, and concentrations are believed to have more than tripled in the past two centuries. Most of it comes from coal burning, waste incineration and other types of combustion.
Bill Schroeder of the government research agency Environment Canada has been measuring concentrations of gaseous mercury in the air at Alert, the atmospheric monitoring station on Ellesmere Island, Canada's most northerly island. He started in the summer of 1994, taking measurements every five minutes. Levels remained boringly ...
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