Mystery Ingredient Cleaning Earth's Atmosphere

Christine Dell'Amore
National Geographic News
June 4, 2009

Mother Nature has a previously unknown cleaning agent that scrubs away toxic air pollution, scientists have discovered.

What's more, the existence of the still mysterious substance has shaken up decades-long assumptions about our atmosphere's self-cleaning process.

Many studies have shown that trace gases and pollutants in the lowest level of our atmosphere break down naturally, thanks to molecules called hydroxyl (OH) radicals.

But the breakdown spews out ozone, itself a toxic pollutant and a greenhouse gas. (Get global warming facts.)

Not so in China's heavily polluted Pearl River Delta, where experts were stumped to find lots of OH radicals but relatively small amounts of resulting ozone.

(Related: "China's Olympic Pollution Efforts Paid Off, Expert Says.")

"It was a complete surprise to us [that], after such a long time of scientific research, such a big gap has been found," said study co-author Franz Rohrer, of the Institute of Chemistry and Dynamics of the Geosphere in Jülich, Germany.

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Highly reactive OH radicals are continually recycled in the atmosphere through reactions with water vapor and nitric oxide, both naturally present in the air.

Part of nature's self-cleaning mechanism, the reactions break down trace amounts of pollutants, Rohrer said.

But when the radicals are recycled by nitric oxide, ozone is created.

In the Pearl River region, about 37 miles (60 kilometers) northwest of Guangzhou (Canton), OH radicals were more concentrated than in any other place measured by the team worldwide, Rohrer said.

Continued on Next Page >>


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