Aerial photo of Leishui River in Leiyang city, Central China’s Hunan Province Photo: VCG

The Ecology and Environment Department of Hunan in Central China issued on Tuesday a notice on the emergency treatment of abnormal thallium concentrations in the Chenzhou-Leiyang section of the Leishui Basin. The source of the contamination has been identified and controlled, and the water quality at various downstream water plants remains unaffected. 

According to the notice, thallium levels in the Chenzhou-Leiyang section of the Leishui River measured 0.13 micrograms per liter on March 16, exceeding the limit of 0.1 microgram per liter set by the Environmental Quality Standards for Surface Water, China Central Television (CCTV) reported on Tuesday.

Guided by the Ministry of Ecology and Environment’s emergency office, the cities of Chenzhou and Hengyang in Hunan initiated emergency response measures. The pollution source has now been brought under control. 

Following the incident, the two cities have activated their emergency response for sudden environmental events, organizing sampling, monitoring, and source tracing across the entire Leishui River basin. 

On March 17, authorities confirmed that the source of the contamination was a cement factory in Chenzhou’s Suxian district. The primary cause was the recent demolition of an old production line kiln, during which thallium-containing dust inside the kiln was washed away by rainwater into the external water environment.

In recent emergency response efforts, Chenzhou has prioritized pollution source control by organizing the transportation of wastewater from the affected company to a heavy metal wastewater treatment plant for proper disposal. Additional measures included anti-seepage treatment, emergency pool construction, brick containment and concrete reinforcement of drainage channels to eliminate pollution risks.

For the affected river sections downstream of the company , Chenzhou and Hengyang  have implemented measures under the guidance of national and provincial technical experts, including pollution source interception and diversion, thallium-removing agent treatment, enhanced water flow regulation and monitoring of water quality indicators along the rivers to ensure the safety of residents’ drinking water. 

Since March 16, thallium levels in water discharged from downstream plants have remained below the limit of 0.1 microgram per liter set by national drinking water standards, monitoring data showed.

After the incident, emergency experts from the Ministry of Ecology and Environment rushed to the site to direct Chenzhou and Hengyang in their emergency response efforts. Current monitoring results show that the water quality at the Leiyang’s water plant meets the required standards, CCTV reported. 

Hunan’s Ecology and Environment Department launched an emergency monitoring plan, establishing 19 quality checkpoints and 21 treatment coordination points along the river.

Authorities have installed 40 water monitoring points across the Chenjiang River and Leishui River, including 37 manual monitoring spots and three automated monitoring stations. Additionally, emergency response teams from both cities have set up eight emergency chemical dosing sites at various monitoring spots.

Chenzhou and Leiyang, through which the Leishui River flows, have both set up emergency command centers to handle the water quality issue.

Authorities are dosing polluted sections with chemicals to lower thallium levels, while water plants along the river have stepped up purification to ensure safe output.

Thallium is a toxic heavy metal that exists as a colorless and odorless crystal.

According to Xiong Gaoli, an expert from the emergency response center of the Ecology and Environment Department of Hunan, the current purification method involves using potassium permanganate and sodium hydroxide to oxidize thallium. This process forms thallium hydroxide, which is insoluble and precipitates out of the water.

According to information provided by the Leiyang’s disease control and prevention department, the quality of the water output at all water plants in the city currently meets the required standards.

Wang Junneng, an engineer from the research institute of ecological environment emergency response of the Ministry of Ecology and Environment, said three districts and counties along the downstream from this section of the river are involved in the incident. Water plants there have upgraded treatment systems and stocked chemicals to ensure a stable supply. 

The Xiangjiang River is about 140 kilometers downstream from Leiyang. Its flow rate is about six times that of the Leishui River, meaning that even if the water enters Xiangjiang River with the current thallium level, it will not impact on the Xiangjiang River, Wang said. 

CCTV reported that nearby farmland, vegetation and aquatic life are under close monitoring, with emergency measures in place.

Global Times