Arsenic to the rescue: Controlling radioactive contamination in abandoned uranium mine

  • Scientists from the University of Sheffield discover that arsenic can prevent uranium from being transported to rivers and groundwater in the environment.
  • This is believed to be the first example of arsenic controlling uranium migration in the environment.
  • This discovery has far-reaching implications for safety and environmental issues faced with abandoned uranium mines around the world as well as for nuclear accident sites and historical nuclear weapons testing sites.

Arsenic Detected usine SynchrotronScientists from the University of Sheffield have unearthed a new mechanism to control radioactive contamination at South Terras, Britain’s abandoned uranium production mine, using the toxic element arsenic.

Arsenic, more commonly associated with its use in grisly murders, has emerged as the unlikely hero in a study into the containment of uranium at the UK’s only production facility for uranium ore.

South Terras Mine, near St Austell in Cornwall, is now abandoned, so finding a way of preventing any uranium that remains in the spoil heaps from migrating to the surrounding environment is essential.

The study, carried out by an international team and led by the Department of Materials Science and Engineering at the University of Sheffield, found that uranium combined with arsenic to form a complex mineral, known as meta-zeunerite, which was found in the topsoil at the mine.

Dr. Claire Corkhill, the lead author of the study, published in Nature Materials Degradation, said “The location of the South Terras mine, and the surrounding area, is well known for mining of arsenic-bearing minerals. Natural weathering of arsenic and uranium minerals in the spoil heaps and soils of South Terras, has released both arsenic and uranium, which form the highly insoluble secondary mineral meta-zeunerite. Locking up the uranium in this mineral structure means that it cannot migrate in the environment”.

The team used some of the world’s brightest synchrotron X-ray microscopes, the Swiss Light Source and the National Synchrotron Light Source (USA), to unearth what is believed to be the first example of arsenic controlling uranium migration in the environment. These microscopes use intense X-ray beams to focus on a spot just a millionth of a metre in diameter.

Co-author of the study, Prof. Neil Hyatt, said, “We can use synchrotron X-rays to identify and isolate the microscopic uranium particles within the soils and determine their chemical composition and mineral species. It’s like being able to find tiny uranium needles in a soil haystack with a very sensitive metal detector”.

The study has far reaching implications, from the remediation of abandoned uranium mines across the world, to the environmental clean-up of nuclear accidents and historic nuclear weapons test sites. It also shows the importance of local geology on uranium behaviour, which can be applied to develop efficient clean-up strategies.

The full study can be found in npj Materials Degradation.