CHENGDU, June 24 -- Biologists have found a strain of duckweed that can effectively purify polluted water and transform nitric oxide into biological fertilizer, a researcher told Xinhua on Wednesday.

A research team lead by Zhao Hai, with the Chengdu Institute of Biology under the Chinese Academy of Sciences, identified the duckweed species from more than 800 samples collected across the world in nine years.

Should this duckweed be planted in just 1 percent of China's lakes and ponds, it could generate 1.72 million tons of ethanol annually, worth 10.3 billion yuan (1.68 billion U.S. dollars). Meanwhile, it can reduce emissions of carbon dioxide by 10 million tons, said Zhao.

More than 70 percent of China's rivers and lakes are polluted and reducing aquatic nitric oxide content would go some way to addressing this, he said.

Duckweed, the smallest aquatic flowering plant in the world, absorbs a high level of nitric and phosphide and is quite effective in dealing with heavy metal pollution, said Zhao.

After six days of duckweed treatment, wastewater passes the top level pollutant discharge standard, he said.

The team has applied for a national invention patent for the duckweed system.