Environmental experts say the toxic metal contamination of a tributary of the Pearl River in Guangxi may evolve into the mainland's worst chemical spill in decades.
Local officials have been accused of lax management and secrecy in dealing with the contamination.
As much as 20 tonnes of cadmium, one of the most toxic of metals, may have been discharged into the Longjiang River early last month, according to a member of an emergency task force set up by Guangxi authorities to handle the spill, China News Service reported yesterday.
Xu Zhencheng, a leading member of the task force and a researcher affiliated with the Ministry of Environmental Protection, said at a closed government meeting on Sunday that while seven tonnes of cadmium had already been neutralised by the dumping of hundreds of tonnes of chemical powder, there were still 13 tonnes of the heavy metal pollutant left undissolved in the river more than two weeks after the spill was first spotted.
By comparison, the country's total discharge of carcinogenic cadmium in 2010 was about 30 tonnes, according to the annual environmental statistics report published by the ministry in December.
In 2005, an illegal release of 6.3 tonnes of cadmium caused a massive spill on the Beijiang, or North River - a major tributary of the Pearl - choking freshwater supplies for at least 100,000 people in northern Guangdong and sparking a pollution scare in major cities along the river, including Guangzhou.
In the latest disaster, metal-pollution experts were appalled by the first official estimate of the scale of the spill, decrying local authorities for what they said was routine sloppiness and lax management of toxic-metal smelters, as well as secrecy in dealing with the contamination.