Chinese scientists are improving the technology to "suck up" poisonous elements, mostly heavy metals like arsenic, copper and zinc, from polluted soil to repair contaminated lands.

In some parts of China, scientists have grown poison-accumulating plants, widely regarded as a "hyperaccumulators" in academic circles, in poisonous soil to accumulate heavy metals, which are to be recycled and further processed into useful industrial materials, said Chen Tongbin, a senior researcher with the Geographic Science and Resources Institute of the Chinese Academy of Sciences (CAS), in an exclusive interview with Xinhua on Tuesday.

 

Chen's research team has begun to renovate more than 5,000 mu (about 333.3 hectares) of arsenic polluted fields in south China's Huanjiang County, Hechi City of Guangxi Zhuang Autonomous Region.

 

Chen said when floods occur in south China's Yunnan and Guangxi, water containing minerals at the upper reaches of rivers always pollute lower watercourses, causing crop losses or even infertility in large area of lower-reach fields.

 

"The 5,000-mu soil pollution in Guangxi is serious. Soil contamination is the most dangerous because it is hidden, slow and fundamental," said Chen.

 

Chen is leading the research on soil recovery technology, which is funded by the state high technology advancement plan and was initiated in March 1986 and is known as the 863 Program.

 

A global leader in technology for collecting arsenic from soil, Chen's team proved that a brake fern widely found in southern China, with the scientific name of Pteris vittata L., has a strong ability to draw arsenic from the soil.

 

Arsenic density in the mature plant's leaves averages 0.8 percent, a far cry from organic nutrients of nitrogen and phosphorous," said Chen who started a search for the poison-accumulating plant in 1997 throughout the country.

 

"The plant could survive a heavily polluted environment with arsenic density of three percent," said Chen, citing that it must be very useful for soil recovery in China's high arsenic concentration areas like Chenzhou in central China's Hunan Province, as well as southwest China's Guizhou Province and north China's Inner Mongolia Autonomous Region, where a large area of arsenic pollution.

 

Since the 1980s, global scientists have blazed a new way in cleaning polluted soil with hyperaccumulators. Decontamination by plants and recycling technologies will make heavy industries less environmentally damaging.

 

It is estimated that soil recovery technologies through plants might have a market worth US$2 billion. "It's proven that the hyperaccumulators are the best possible choice for soil recovery," Chen said.

 

His team has zeroed in on 16 such hyperaccumulators which were all found in China, by means of a field survey and greenhouse cultivation. Meanwhile, they have developed several additives which might strengthen their poison collecting abilities, Chen said.

 

According to Chen's research, poisonous arsenic accumulated by the plant can be stored in a safe place within the brake fern's body which exerts little influence on the overall growth of the plant.

 

His team leads the world by using techniques and equipment like simultaneous-radiation and ESEM, an electron microscope, to analyze directly on live plants why hyperaccumulators can sustain huge densities of poisonous elements.

 

Chen has called for intensified government effort to alert the public to the danger of soil contamination and promote legislation in this regard.

 

Currently, the Law on Prevention of Soil Contamination drafted by China's State Council and aimed at legally binding on practices causing soil contamination, is about to be submitted to the National People's Congress, China's top legislature, for deliberation.

 

(Xinhua News Agency February 22, 2006)