Wednesday, 1 April 2020

Failure of mine tailings dam contaminates Yijimi River in Heilongjiang Province, China.

Emergency water supplies have had to be arranged for about 200 000 people whose water usually derives from the Yijimi River in Heilongjiang Province, China, following a leak from a tailings dam on Saturday 28 March 2020. The leak occurred at a Molybdenum mine operated by Yichun Luming Mining, and is thought to have released about 2.53 million cubic metres (1 530 million litres) of contaminated water into the river, with raised Molybdenum levels being detected 110 kilometres down stream to date, although local authorities are more concerned about the toxic effects of the oil added to the water as a flotation agent (to help separate the metal from the ground ore), which is potentially toxic to both wildlife and humans.

Water contaminated with tailings from a Molybdenum mine flows into the Yijimi River in Heilongjiang Province, China, on Saturday 28 March 2020. Xinhua.

Tailings ponds are used to store sediment-laden waters from mines; such waters typically contain a high proportion of fine silt and clay particles, which take time to settle out of the water. The resulting water may be fairly clean, or may contain other pollutants (typically acids, either generated by the local geology or used in the mining process), and need further treatment. In some instances acid is added to such pools in order to dissolve the product, which is then released from the resultant chemical slurry by further treatment.

The practice is currently widespread in China, however, the Chinese Ministry of Emergency Management has announced plans to introduce strict new controls on such dams, with future dams having to adhere to much tighter safety regulations, and to close older dams which cannot comply with these. The Yichun mine tailings dam had already been flagged as problematic, with the operating company fined for safety breaches associated with the dam twice in 2018.

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