Uranium Waste From This Aussie Mine Was Safely Locked Away, But Microbes Had Other Plans

In 1944, rocks from the Mount Painter mine in the heart of Australia were sent to the US for experiments as part of the Manhattan Project.

The repercussions of those actions left deep scars across the world.

At Mount Painter, though, scientists believed the mine's uranium and rare earth elements were more or less safely locked away in the dry waste piles (a.k.a. tailings).

The site was eventually closed in 1965 and later incorporated into Arkaroola Wilderness Sanctuary.

But recent samples taken from the surface of tailings at Mount Painter's Number 6 Workings suggest the site may not be as safe as we thought.

These tailings have supposedly lain undisturbed for more than 80 years.

But something has been moving potentially dangerous minerals to the surface of the waste piles, where they have accumulated at unexpectedly high concentrations.

In a study recently published in the Journal of Hazardous Materials, researchers suggest that microbes in the rubble are transporting these toxic substances to the top 10cm of the waste, in the form of polymetallic nanoparticles.

"We have traditionally assumed that these toxic metals were securely locked away by nature in these arid environments, but these tiny organisms are proving us wrong," says geoscientist Joël Brugger.

"They are essentially acting as microscopic factories, breaking down stable minerals and mobilizing elements like uranium into the surrounding ecosystem."

Further studies will be needed to confirm that the microbes are actually responsible for the changes seen in these tailings.

But for now, it's the scientists' best guess, as there aren't many other good explanations.

In other parts of the world, researchers have also documented radiation-resistant microbes interacting with uranium waste.

The biggest concern is that these microbes appear to be converting the minerals from insoluble phosphates into colloidal forms that can easily travel through the environment.

Rain is rare in semi-arid Arkaroola, arriving in the form of sudden summer thunderstorms. Converted into colloids, minerals like uranium are readily suspended in rainwater, which could carry them much further from the mine site, especially during the flash flooding that sometimes occurs in Arkaroola.

Toxic and radioactive minerals like uranium and rare earth elements are not what you want sprinkled throughout the soil and waterways.

Uranium is highly radioactive, and exposure to it – for instance, by drinking contaminated water or inhaling tiny particles – can cause serious damage to humans and other living things.

The paper calls for a serious rethink of how we deal with mining waste.

While Arkaroola is protected from further mining, its radioactive legacy is clearly not over yet.

Mount Painter's Number 6 Workings is just one of many mines left abandoned after the proliferation of nuclear weapons during the 20th century.

But uranium production continues across the world. And there's never been such a great demand for metals and minerals.

"As a result of continuing global development, the transformation of the world's energy infrastructure away from fossil fuels, and the electrification of transport infrastructure, demand for base metals such as copper, critical minerals such as rare earth elements, and energy minerals such as uranium is increasing," Brugger and team write.

The volume of mining waste is expected to increase rapidly, especially as ore grades decrease. Even when uranium isn't the goal of a mine, many rare earth element deposits are tied up with uranium and thorium that go on to enter the mine's waste stream.

"As we rapidly scale up operations to meet the unprecedented demand for critical minerals, the volume of mining waste generated globally is going to rise significantly," says environmental microbiologist Santonu Sanyal.

"Understanding exactly how these native microbes interact with waste materials is absolutely vital if we want to prevent unseen, long-term environmental contamination and develop the sustainable mine of the future."

The research has been published in Journal of Hazardous Materials.