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Sowing hungry ferns to purify the polluted farm land
By Guo Likun |
May 27, 2009, Wednesday
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EIGHT years after his arable land was polluted by heavy metals, Zhou Xiaobing finally saw hope of a harvest.
"I don't know what magic they used, but the land is covered with plants again," said the 37-year-old farmer in south China's Huanjiang County, Guangxi Zhuang Autonomous Region.
In 2001, flooding from the Huanjiang River carried mineral processing industrial wastes from the tailings and dams of three major mining companies on the upper reaches to lower watercourses. This caused infertility in around 333 hectares of arable land, including Zhou's 0.6 mu (0.06 hectare).
"This place didn't even grow a blade of grass at that time," Zhou said, standing in his land that, he claimed, used to yield 500 kilograms of grains a year.
Now it is part of a 30-mu soil recovery base set up by one of China's leading soil cleaning experts Chen Tongbin and his team in 2005.
Chen uses plants, such as a domestic fern, to "suck up" heavy metals like arsenic, copper and zinc, from contaminated soil.
The 40-member team is undertaking soil recovery projects in Guangxi, Hunan and Yunnan provinces, and in Guangdong and Beijing, altogether covering around 13 hectares.
The base set up in Chenzhou, Hunan Province, in 2001 was the world's first arsenic-polluted soil recovery base.
"Unlike the first base that only use the fern to rehabilitate the land, we tried intercropping in this base," said Chen, principal investigator at the Center for Environmental Remediation of the Chinese Academy of Sciences (CAS) Institute of Geographical Sciences and Natural Resources research.
They planted fern and cash crops, including maize, sugar cane, and mulberry, in alternate rows.
"We can rehabilitate the land and have yields at the same time," he said. "It could help to increase farmer's income."
Last year, the maize in the base grew so well that villagers flocked to harvest them - they had to be prevented as the grain was still toxic, said Chen.
After three years of rehabilitation, the soil's PH value returned to normal, the amount of arsenic was cut by 12 percent, the yield and quality of mulberry leaves had not been affected, and the heavy metal contained in silk and silkworm pupa did not exceed the national level, according to the Center for Environmental Remediation.
Compared to water and air, soil contamination is the most dangerous because it is hidden and can only be reversed by human intervention as nature cannot do it, Chen said. "It'll take at least three to five years for even the moderately polluted land to recover."
Arsenic and many of its compounds are especially potent poisons and commonly used as pesticides, herbicides, and insecticides.
"Long-time exposure to arsenic might induce cancer, and high-dose arsenic could lead to death," he said. "In arsenic-polluted areas, the amount of arsenic in people's hair was several times higher than the normal level."
Arsenic poisoning caused a spate of tragedies in China last year.
A high concentration of arsenic was found in water from Yangzonghai Lake in Yunnan Province last June, caused by leakage in a sub-standard waste water pool at a nearby factory.
Last September, 26 local officials involved in the case were given administrative punishment, including warning, demotion and firing. Twelve officials were sacked.
In a separate case last October, 450 people were sickened after drinking contaminated water in Hechi city in Guangxi, including four with arsenic poisoning.
City authorities said a typhoon triggered torrential rains in September and waste water containing arsenic overflowed from a company's premises and polluted nearby ponds and wells.
A global leader in technology for collecting arsenic from soil, Chen's team discovered Chinese brake fern, Pteris vittata L, which had a strong capacity to extract arsenic from soil in 1999.
Besides the brake fern, the researchers found and cultivated a dozen more such pollution-extracting plants, called by scientists "hyper-accumulators."
China has the largest proven reserves of arsenic with about 70 percent world share, while around 62 percent of the arsenic is concentrated in Guangxi, Yunnan and Hunan, according to the Center for Environmental Remediation.
"Mine exploration usually leads to soil pollution," the 46-year-old scientist said.
He said there was no "clear picture" of soil pollution in China, though some experts estimated one-fifth, or about 20 million hectares, of China's arable land had been polluted.
(The author is a Xinhua writer.)
"I don't know what magic they used, but the land is covered with plants again," said the 37-year-old farmer in south China's Huanjiang County, Guangxi Zhuang Autonomous Region.
In 2001, flooding from the Huanjiang River carried mineral processing industrial wastes from the tailings and dams of three major mining companies on the upper reaches to lower watercourses. This caused infertility in around 333 hectares of arable land, including Zhou's 0.6 mu (0.06 hectare).
"This place didn't even grow a blade of grass at that time," Zhou said, standing in his land that, he claimed, used to yield 500 kilograms of grains a year.
Now it is part of a 30-mu soil recovery base set up by one of China's leading soil cleaning experts Chen Tongbin and his team in 2005.
Chen uses plants, such as a domestic fern, to "suck up" heavy metals like arsenic, copper and zinc, from contaminated soil.
The 40-member team is undertaking soil recovery projects in Guangxi, Hunan and Yunnan provinces, and in Guangdong and Beijing, altogether covering around 13 hectares.
The base set up in Chenzhou, Hunan Province, in 2001 was the world's first arsenic-polluted soil recovery base.
"Unlike the first base that only use the fern to rehabilitate the land, we tried intercropping in this base," said Chen, principal investigator at the Center for Environmental Remediation of the Chinese Academy of Sciences (CAS) Institute of Geographical Sciences and Natural Resources research.
They planted fern and cash crops, including maize, sugar cane, and mulberry, in alternate rows.
"We can rehabilitate the land and have yields at the same time," he said. "It could help to increase farmer's income."
Last year, the maize in the base grew so well that villagers flocked to harvest them - they had to be prevented as the grain was still toxic, said Chen.
After three years of rehabilitation, the soil's PH value returned to normal, the amount of arsenic was cut by 12 percent, the yield and quality of mulberry leaves had not been affected, and the heavy metal contained in silk and silkworm pupa did not exceed the national level, according to the Center for Environmental Remediation.
Compared to water and air, soil contamination is the most dangerous because it is hidden and can only be reversed by human intervention as nature cannot do it, Chen said. "It'll take at least three to five years for even the moderately polluted land to recover."
Arsenic and many of its compounds are especially potent poisons and commonly used as pesticides, herbicides, and insecticides.
"Long-time exposure to arsenic might induce cancer, and high-dose arsenic could lead to death," he said. "In arsenic-polluted areas, the amount of arsenic in people's hair was several times higher than the normal level."
Arsenic poisoning caused a spate of tragedies in China last year.
A high concentration of arsenic was found in water from Yangzonghai Lake in Yunnan Province last June, caused by leakage in a sub-standard waste water pool at a nearby factory.
Last September, 26 local officials involved in the case were given administrative punishment, including warning, demotion and firing. Twelve officials were sacked.
In a separate case last October, 450 people were sickened after drinking contaminated water in Hechi city in Guangxi, including four with arsenic poisoning.
City authorities said a typhoon triggered torrential rains in September and waste water containing arsenic overflowed from a company's premises and polluted nearby ponds and wells.
A global leader in technology for collecting arsenic from soil, Chen's team discovered Chinese brake fern, Pteris vittata L, which had a strong capacity to extract arsenic from soil in 1999.
Besides the brake fern, the researchers found and cultivated a dozen more such pollution-extracting plants, called by scientists "hyper-accumulators."
China has the largest proven reserves of arsenic with about 70 percent world share, while around 62 percent of the arsenic is concentrated in Guangxi, Yunnan and Hunan, according to the Center for Environmental Remediation.
"Mine exploration usually leads to soil pollution," the 46-year-old scientist said.
He said there was no "clear picture" of soil pollution in China, though some experts estimated one-fifth, or about 20 million hectares, of China's arable land had been polluted.
(The author is a Xinhua writer.)
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