VOA慢速英语2015 撒哈拉沙漠的尘土吹到亚马逊雨林（在线收听）

AS IT IS 2015-03-15 Saharan Dust Feeds Amazon Rainforest 撒哈拉沙漠的尘土吹到亚马逊雨林

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

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

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

In the 1970s, Joseph Prospero found that a large amount of dust can blow all the 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 research shows 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 found that an average of 28 million metric tons falls in South America's Amazon River basin each year.

"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 of Saharan dust each year. He says the dust is an important provider of fertilizer.

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

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

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

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 and grow

fertilizer – n. a substance that helps plants grow