tailings

The tailings dam at a Sino Metals copper mine failed in Feb.

The tailings facility is where waste from mining is stored.

"The tailings release and breach was promptly brought under control within hours of detection," the firm said in a statement on 3 September.

The spill happened when a tailings dam, used to store toxic waste and heavy metals, collapsed into the Kafue River, a key drinking water source, following heavy rain.

At much higher concentrations, which may be relevant for testing environmental contamination such as mine tailings, the accuracy is within 4 percent.