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Cleaning mercury pollution from gold mines

- Wits University

Postdoc helps mining industry to remediate high levels of mercury in the Wits mining basin.

Dr Julien Lusilao, an environmental and analytical chemist at Wits University, is helping the mining industry to clean up high levels of mercury pollution that has been created by a century of gold mining in Gauteng.

Lusilao, a citizen of the Democratic Republic of the Congo, completed his PhD in Environmental and Analytical Chemistry at Wits in 2012 and for the last four years specialised in understanding mercury.

Mercury, a heavy metal, is highly toxic – especially in its organic form as methyl mercury.  It is widely used in the gold mining industry to extract gold from ore. The sludge is put into tailings dumps, which have been polluting the Witwatersrand for decades.

Up until recently nothing was done to rehabilitate these dumps but Lusilao’s work is the start of a remedial project that may be implemented at some of the largest gold mines in the area.

The research project was initiated by one of the largest gold mining corporations in the country, with the aim of remediating the high levels of mercury in the Wits mining basin. Lusilao’s research involves establishing the levels of mercury, while the Wits School of Animal, Plant and Environmental Sciences has been tasked with the remedial work.

“If you want to remedy the situation you need to find out how it works,” says Lusilao.

Methyl mercury is extremely volatile and Lusilao had to develop methodologies on how to take samples safely in the field and how to analyse them in the laboratory.

“We came up with all sorts of analytical formulae to identify mercury in all its different forms, which are liquids, gases and solids,” he explains. Unacceptably high levels of mercury occur in the soil, air and water systems in and around Gauteng, adding to the effect of Acid Mine Drainage.

“The situation is critical,” he says.

While the large mining corporations are taking the problem seriously and have implemented remedial actions, the challenge lays in the rehabilitation of old, abandoned mines and tailings dumps, as well as artisanal “illegal” mining.

“The artisanal miners dump a lot of mercury in the environment and just leave it there. It is difficult to reason and to talk to them,” he says.  “This situation may be worse than that of big mining.”