VOA慢速英語(yǔ): 撒哈拉沙漠的塵土是怎樣滋養(yǎng)亞馬遜雨林的

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Large clouds of dust blowing off the Sahara desert caneasily be seen from space.

Joseph Prospero is with the University of Miami in the United States. He hasstudied African dust for many years.

"Atmospheric dust African dust is one of the most prominent atmosphericfeatures, second only to clouds."

In the 1970s, Joseph Prospero found that a large amount of dust can blow allthe way across the Atlantic Ocean. He spoke to VOA by Skype.

"We knew there was a lot of dust. I mean it's obvious there's a lot of dust.When it rains in Barbados or even here in Miami during the summer months,you actually get a layer of mud in the bottom of a bucket."

African dust storms can harm air quality across the ocean. But new researchshows the storms also can do some good.

Scientists observed Saharan dust by satellite as it blew across the Atlantic.

Hongbin Yu is an atmospheric scientist at the University of Maryland. He foundthat an average of 28 million metric tons falls in South America's AmazonRiver basin each year.

The world’s largest desert and the world’s largest rainforest are linked by a transoceanic stream of dust.

"Yes, it's surprising because of the huge amount of dust and phosphorous."

Phosphorous is a nutrient that plants need to grow.

Hongbin Yu found that the Amazon receives about 22 thousand metric tons ofSaharan dust each year. He says the dust is an important provider offertilizer.

"The soil has limited phosphorous and it also can be washed out by rain andflooding."

In fact, the phosphorous falling from the sky is about the same as the amountthat rivers carry out each year.

The thick rainforest and the desert dust are joined together on one smallplanet.

I’m Marsha James.

Steve Baragona reported this story for VOA. Marsha James adapted it forLearning English. George Grow was the editor.

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Words in This Story

dust - n. pieces of matter so small that they can float in the air

nutrient – n. a substance that plants, animals, and people need to live andgrow

fertilizer – n. a substance that helps plants grow