急需牛津英语八年级（下）第二章课文“Pollution fighters”全文！

This is Steve Ember with the VOA Special English Agriculture Report.

Poplar trees can be cut down and used for wood or paper. Or they can be left to stand and also used for different purposes. Poplar trees are often used to guard against water pollution. They are planted as barriers to keep waste from entering groundwater and rivers.

Their large root systems trap waste, like nitrogen-based fertilizer, and help reduce the loss of soil. Now, poplar trees may become important tools for cleaning the environment. Some scientists think poplars can be a valuable resource to remove poisonous substances from the soil.

The poplar tree is found in many places in the northern half of the world. It is a fast growing tree that requires a lot of water. Different kinds of poplar trees are native to Asia, Europe and North America. In the United States, poplars are also known as cottonwood trees.

For years, Professor Richard Meagher of the University of