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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 Georgia has done research on genetically engineered plants. He is now testing a poplar tree that has been genetically engineered to take in mercury through its roots. The tree then slowly releases the mercury into the air through its leaves.

Mercury is a highly poisonous metal. It is a waste product of many industries. Mercury builds up in fish and other living things. It is especially dangerous to the development of children. This is why women who might get pregnant are warned to be careful about mercury levels in the food they eat.

Professor Meagher is testing his genetically engineered poplars on some land in Danforth, Connecticut. The ground is polluted with mercury from a factory once there. The scientist has planted one hundred sixty poplars to remove the pollution.

Not everyone likes the idea to use genetically engineered trees to collect mercury. Critics say these could reproduce with wild trees or displace them. Another criticism is that the poplars only spread mercury rather than remove it from the environment. The professor says it is better to spread the mercury than have it all in one place where it could be more of a health risk.

Still, there is great interest in using plants to process and control harmful substances. And poplar trees are among the most studied.

But using poplars as a natural barrier against water pollution is not a new idea. The Chinese have used them this way for thousands of years.

This VOA Special English Agriculture Report was written by Mario Ritter. This is Steve Ember.