Is there a threat to animal health and the human food chain after more than a century of gold mining pollution on the West Rand and far West Rand?
Researcher David Hamman, of the North West University’s Potchefstroom Campus, is probing this and has detected “significant” levels of radioactive uranium and heavy metals in soil, water and cattle tissue samples in one of the richest gold mining areas in the world – the Wonderfonteinspruit catchment area.
This blighted river system runs between Krugersdorp and Potchefstroom and flows for about 90km through a region with the richest gold deposits in the world.
“It’s… been exposed to the related pollution for more than a century,” writes Hamman in his dissertation, “A Holistic View on the Impact of Gold and Uranium Mining on the Wonderfonteinspruit”.
Hamman collected sediment, water, soil, grass and cattle tissue samples to determine the extent of mining-related pollution in the Wonderfonteinspruit. He used the Mooi River as a control subject.
“The cobalt concentration (in) sediment samples was found to be 16.37 times higher in the Wonderfonteinspruit, the nickel concentration was 30.4 times higher, |the zinc concentration was |103.49 times higher, the selenium concentration was 7.14 times higher, the cadmium concentration was 17.88 times higher, the lead concentration was 1.32 times higher and the uranium concentration was 375.78 times higher.
“All these elements are by-products of non-ferrous mining activities. The elevated concentrations of these elements, which were found in the streambed sediment of a site in the Lower Wonderfonteinspruit, suggest they could have resulted due to upstream gold mining activities.”
Radioactive and heavy metal contamination is from mine wastes leaching into surface and groundwater, and from fugitive dust emissions and tailings dams.
“The normal uranium concentration found in irrigated or natural grasses could not be found in an extensive search. All the sites in the experimental group, including the control site, drastically exceeded these concentrations, which may suggest that the grasses have been exposed to elevated uranium concentrations.”
The water samples were shown to exceed the cobalt, nickel, copper, zinc, selenium and cadmium concentration ranges normally found in natural waters.
“In addition… the maximum values for both uranium and lead exceeded the average concentrations found in the natural waters.
“While there are very few farms in the catchment that still irrigate from the Wonderfonteinspruit, almost all farmers with property along the Wonderfonteinspruit use it for livestock watering purposes. Informal settlements along the Wonderfonteinspruit use the water to irrigate vegetables and to water livestock.”
Hamman’s research also showed how cobalt concentrations in the liver and meat samples of cattle from both groups exceeded normal ranges, and the cobalt, copper, selenium and uranium concentrations found in the kidney samples from the Wonderfonteinspruit exceeded the normal range.
The uranium concentration in the cattle samples from the experimental group was 126.75 times higher in the liver, 4 350 times in the kidney, 47.75 times higher in the spleen, 31.6 times higher in the muscle tissue, 60 times higher in the bone and 129 times higher in the hair than in the cattle samples from the control group.
“The uranium did not only accumulate in the predicted tissue samples (bone, liver and kidney), but also in the muscle tissue samples.
“The study revealed that the major route of ingestion for all the elements of interest, excluding nickel and cobalt – which happens via soil ingestion – was through the ingestion of grass.”
A human health risk assessment was performed, which showed that “no toxic risk exists for both groups (Mooi River and the Wonderfonteinspruit catchment area) if an intake rate of 0.13kg a day is assumed”.
Mariette Liefferink, an environmental activist, called on the Department of Water Affairs to report urgently on Hamman’s findings and the interventions he has proposed.