Large gold-mining companies operating to the west of South Africa's commercial centre, Johannesburg, stand accused of contaminating a number of water sources with radioactive pollutants.

One case involves the Wonderfontein Spruit ("water course", in Afrikaans): a stream that runs 90 kilometres from the outskirts of Johannesburg to the south-west past the towns of Krugersdorp, Bekkersdal, Carletonville and Khutsong, before flowing into the Mooi River near Potchefstroom.

Mariette Liefferink, an environmental activist, blames the mines for the high concentrations of heavy metals such as arsenic, cadmium, copper cobalt and zinc in the waters of the spruit. She is particularly troubled by the levels of uranium, which gives off radioactive by-products such as polonium and lead.

"The Wonderfontein Spruit is of major concern to us because every year the gold mines discharge 50 tonnes of uranium into the receiving water course. The Water Research Commission (a parastatal research body) has found that there are approximately 1,100 milligrammes per kilogramme of uranium in the upper Wonderfontein Spruit, and 900 milligrammes per kilogramme in the lower Wonderfontein Spruit area."

Heavy metal concentrations are higher in the upper reaches of the river because a large percentage of the pollutants sink into the sediments as water flows downstream. This means that under normal circumstances water tests in lower areas do not cause great concern, and users may feel that they are not under threat from heavy metal contaminants. If, however, the sediments are in any way disturbed -- by cattle, or children playing in the river, for example -- the uranium can easily be dislodged from the sediments and reabsorbed into the water.


Subscribe to IEMA's newsletters to receive timely articles, expert opinions, event announcements, and much more, directly in your inbox.