For more than a decade the phytoremediation system which uses plants to help absorb pollutants has become a major part of clean-up programmes across the world.

By 1998, some 400 natural plants able to absorb materials, such as heavy metals, arsenic or fluoride, had been identified worldwide.

But none were indigenous to China.

Experts, however, now believe there are several native species that can be used to remove pollutants.

One particular ferny plant caught the attention of Chen Tongbin, a senior biologist with the Chinese Academy of Sciences (CAS), eight years ago.

Today the plant has become the centre of Chen's academic life.

Chen, a senior researcher at Beijing-based Institute of Geographical Sciences and Natural Resources Research of CAS, believes that the big-leaf wugongcao (pteris vittata) represents the future of environmental remedy in China.

Tests have already showed it can soak up high levels of cancer-causing arsenic materials in soil.

"The plant could even create a whole industry to come to the aid of fighting soil pollutions in China," Chen told China Daily.

His work is part of intensified efforts to use natural plants to fight pollutions, for which Chen is one of the co-ordinators.

Chemical analysis

Experts had tried fruitlessly for several years to find native plants that could help solve oil pollution problems in China.

"As a plant remediation researcher, I felt embarrassed," Chen recalled.

China has an urgent need to discover plants that can be used for the phytoremediation system.

With a sharp increase in industrialization, mining, and the overuse of chemical fertilizers, land pollution has become a major hazard to China's environment and to people's health.

Scientists had struggled to introduce foreign species to China, but many native plants withered and died shortly after being planted.

But Chen is adamant that native plants, such as wugongcao, already exist in the vast areas of China to fight environmental pollution.

"The basic principle of Darwinism is species adapt to their environment, so my eyes fell onto those places with heavy pollution," Chen said.

His belief was corroborated by initial field studies in Shimen County of Central China's Hunan Province, where the mining industry has existed for more than 1,500 years.

Chen himself noticed plants grew robustly in the area,

Chemical analysis of the soils and the plants revealed very high concentrations of arsenic, which became a serious problem in a number of areas in China and South Asia in the late 1990s.

High levels of arsenic in drinking water and food have caused bone diseases as well as cancers in people living in many rural villages.

Before Chen carried out the research, no plant in the world had been found able to hyper-accumulate arsenic to a concentration of more than 1,000 milligrams per kilogram.

Chen, however, still had many hurdles to overcome in analysing the dozens of plants to determine whether at least one was indeed the dream species he was looking for.

While the plants growing there might have been able to tolerate arsenic, there were doubts whether they would be able to absorb the toxin extensively from soil. Even if they could, he needed to learn whether they would retain and pass down the characteristic after they were planted in other areas containing arsenic.

He also had to discover whether plants could grow in large scales, or whether their biomass would be too small to be effectively planted for the removal of high amounts of pollutants.

But, above all, he needed funding to launch major field surveys, soil and plant testing and to screen various varieties of plants.

Chen applied for research grants from several State agencies and science foundations in China. Many evaluation experts, according to Chen, would not agree to his proposals, because of their unfamiliarity with the plant remedy theory.

"Mainstream scientists in the country at that time neglected such multidisciplinary areas as phytoremediation and the use of plants and trees to remove or neutralize contaminants in polluted soil or water," Chen explained.

Many people were doubtful as the idea covers a spectrum of bases, environmental science, biology, ecology, geochemistry, genetics, and traditional and modern seeding, Chen said.

Eventually, he managed to get a small grant from a special fund from the National Natural Science Foundation of China, which was set up to support innovative but debated proposals.

The work of Chen's team has been difficult, with members having to journey to far-flung places for research.

"Sometimes we were stranded in the middle of the wilderness and had to spend the night there," Chen said.

Eventually, Chen and his team pinpointed wugongcao in 1998 as being the most effective plant for phytoremediation.

"The plant not only lives in high arsenic environment, but also shows high arsenic contents in their bodies. In addition, the offshoots of wugongcao also shows robust growth in high-arsenic soil," Chen said.

In recent years, Chen and his colleagues have also identified the plant's biological properties so they can analyze its mechanism in absorbing and cleaning the arsenic pollutants.

Their latest research results have secured them more grants to support Chen in expanding his studies into finding other pollutant-fighting plants.

So far, Chen's team has identified a total of 16 native Chinese plants able to absorb arsenic, lead, copper, and other heavy metals from soil. In early November 2005, their research passed the evaluation of the Ministry of Science and Technology for the National High Technology Research and Development Programme.

Meanwhile, in collaboration with the Institute of High Energy and the Institute of Botany, Chen's team is exploring the genetic basis of wugongcao's mechanism of arsenic hyperaccumulation.

Practical tests

During their research, Chen and other scientists in his team never lost sight of the need to carry out practical studies of wugongcao.

Their chance came after seeing TV reports of the high arsenic pollution in Dengjiatang, a township in Hunan's Chenzhou, which was caused by an arsenic smeltery. As a result of heavy arsenic pollution, two people died and most grain harvested in the area was contaminated. Farmers gathered to protest and demanded the central government severely punish the polluter.

"To choose such a place to begin our demonstration of field application helped increase the role of the plant," Chen said.

He eventually persuaded local officials to open the area for him and his colleagues to carry out their experiments at Chenzhou.

But technical problems remain for the team.

The biggest is how to dispose of the wugongcao after it has absorbed pollutants. In the small-scale experiment in labs, this can be done through the infilling of ash of the burned plant into designated places. At practical levels, however, it is currently hard to do.

"Our multidisciplinary research team has helped me. One of my PhD students who originally worked in chemical industry has developed a chemical able to collect the arsenic during the incineration," said Chen.

"The accumulated arsenic will then become much easier to process."

By 2005, the trial programme in Chenzhou had achieved success..

According to Chen, the arsenic level in the heavily polluted soil has dramatically decreased by half.

The cost is at most one-tenth of the chemical cleaning methods of processing the polluted land, said Lei Mei, a researcher in Chen's team.

The results are encouraging. The Guangxi Zhuang Autonomous region has agreed to offer 100 mu (6.7 hectares) for trial plantations of wugongcao and a major State-owned company in Yunnan Province has decided to co-operate with the team to transfer the technology to Yunnan Province, Chen said.

A private company in Guangxi is also negotiating with Chen's team to invest tens of millions of yuan in industrializing the technology, according to Chen.