Plants used to weed out soil pollution

Chinese scientists have developed soil remediation technologies to prepare for large-scale applications.

The technologies focus on using plants to absorb heavy metal contaminants in soil.

The technologies were developed by the Center for Environmental Remediation of the Institute of Geographic Sciences and Resources Research under the Chinese Academy of Sciences, which began research 10 years ago.

Soil contamination is serious in China, with large areas of cropland polluted, said Lei Mei, a professor at the center.

Soil remediation technologies have been applied on 133 hectares of land in the Guangxi Zhuang autonomous region, Henan, Yunnan and Hunan provinces and Beijing on a trial basis, and Lei said she believes the technologies will have "good application prospects".

A report from the Ministry of Environmental Protection on Thursday showed that about 19.4 percent of farmland in China was polluted, according to Xinhua News Agency.

"The publication of the survey result is a milestone for soil remediation in China," Lei said.

Before the release of the survey results on Thursday, the latest official data available was released by the Ministry of Land and Resources in 2006. That report said that about 7 percent, or 10 million hectares, of arable land in China was contaminated by heavy metals.

By 2009, the country had 135.38 million hectares of arable land.

In 2005, scientists from the center proved in the laboratory that the plant Pteris vittata, or Chinese brake fern, had cleansing abilities when planted in soil polluted by heavy metals such as lead, zinc, sulfur and arsenic.

After the fern becomes saturated with heavy metals from the polluted soil, the aboveground part of the plant is cut off and burned. A new shoot grows from the root, and the process is repeated.

Field experiments since 2010 on 60 hectares of polluted land in Hechi, Guangxi Zhuang autonomous region, showed the plant can reduce heavy metals by 10 percent a year, which means it can help reduce pollutants to safe levels within three to five years.

The scientists have promoted planting of the fern among local farmers. The ferns are intercropped, or grown in the same fields, as cash crops such as flax.

Meanwhile, scientists are developing a new passivator, which is a coat with an oxide layer that protects against heavy metal contamination of the soil.

Liu Wenhua, chief engineer of the Guangdong province Research Center for Geoanalysis, recently developed a new passivator that could reduce cadmium, lead, copper and zinc in soil.