Mining Impacts · impact
Cyanide release
Water · During operation
- Category
- Water
- Timescale
- During operation
Mitigation
Lined ponds with freeboard for storm events, cyanide destruction circuits before discharge, and the industry's voluntary International Cyanide Management Code.
Case
Baia Mare, Romania, 30 January 2000: a dam at the Aurul plant released about 100,000 m³ of water carrying roughly 100 tonnes of cyanide into the Someș, then the Tisza and the Danube.
Mechanism
Gold is dissolved out of ore as a cyanide complex, so a working plant holds large volumes of cyanide-bearing solution in ponds and circuits. A wall failure, an overflow after heavy rain, or a pipeline break puts it into surface water, where it is acutely toxic to fish at very low concentrations.
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