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Pollutants Often Invade Even Pristine Peaks

THE NATION

June 09, 2002|ANDREW BRIDGES | ASSOCIATED PRESS WRITER

There, Cahill jokes, you can tell it's a sunny day if the sky is bright brown. If it's rainy, it's still brown, just a darker shade.

"You're living in a sepia world," he said.

The tiny particles make for spectacular sunsets, but they also pose a serious health hazard, as they can lodge deep in the lungs, contributing to shortened life spans.

Aerosols also might harm agriculture by blocking portions of the spectrum of light from the sun, starving crops such as wheat and rice of the energy they need to grow.

The biggest worry, and the one least understood, is the effect aerosols have on weather and climate.

Some aerosols can cool the planet by shading it from the sun. Others can warm it by absorbing and trapping the sun's heat.

"[Aerosols] are clearly right at the center of some important climatic issues," Huebert said.

Aerosols also might have the ability to aid in the formation of clouds, while retarding their rainfall, scientists reported in December in a study in the journal Science.

Drops of water will coalesce around aerosols in clouds but not clump together to form the larger drops that gravity pulls from the sky as rain.

"We humans may be pushing precipitation away from populated regions," said NASA's Kaufman.

The dust is not all bad news, though; the wafting plumes also carry nutrients to regions that depend on them. On Hawaii, plant life relies on Asian phosphorus and calcium to grow. Phytoplankton--those bottom feeders of the food chain--in the waters off the Alaskan coast crave Asian iron, which blows eastward literally by the millions of tons.

Still, scientists believe it's important to trace the origin of the pollutants, and they say they can do that by using the unique chemistry of aerosols as a fingerprint.

Rahn, the oceanography professor, has developed a roster of about 150 compounds, each with its own signature. With some work, scientists can distinguish between soot from a power plant burning low-sulfur coal from Paonia, Colo., and from a forest fire raging in the Brazilian rain forest.

"Once the scientists say these particles are coming from here, here and here, at that point it's finger-pointing," says Ramanathan, who has proposed a national effort to study aerosols. "That's something we have to leave to the politicians to figure out."

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