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Arsenic found to control uranium contamination

As reported by World Nuclear News, an international team led by the University of Sheffield has discovered that the toxic element arsenic prevents uranium from an abandoned mine in the UK migrating into rivers and groundwater.  The discovery could help in the remediation of former uranium mines and other radioactively contaminated areas around the world, the scientists believe.

The team of scientists – led by the Department of Materials Science and Engineering at the University of Sheffield – studied the uranium and arsenic in the topsoil at the abandoned South Terras uranium mine in Cornwall, England.

The researchers used some of the world’s brightest synchrotron X-ray microscopes – the Swiss Light Source and the USA’s National Synchrotron Light Source – 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 one-millionth of a metre in diameter.

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

Source: © Claire Corkhill
The abandoned South Terras mine in Cornwall where uranium was mined until 1930

According to the study – published on 14 December in Nature Materials Degradation – ore extraction processes and natural weathering of rock at the South Terras mine has led to the proliferation of other elements during degradation, particularly arsenic and beryllium, which were found in significant concentrations.  The arsenic and uranium were found to have formed the highly insoluble secondary mineral metazeunerite.

“Significantly, our data indicate that metazeunerite and metatorbernite were found to occur in solid solution, which has not been previously observed at other uranium-contaminated sites where uranyl-micas are present,” the study says.

Claire Corkhill, lead author of the study, said: “Locking up the uranium in this mineral structure means that it cannot migrate in the environment.”

The researchers concluded that this process at South Terras – which operated between 1873 and 1930, producing a total of 736 tonnes of uranium – is the result of a set of “rather unique” geological conditions.  “To identify this remediation mechanism at other sites, where arsenic and uranium are key co-contaminants, further detailed mineralogical assessments are required,” they said.  “These should be considered as an essential input to understand the ultimate environmental fate of degraded uranium ore.”

“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,” according to the scientists.  “It also shows the importance of local geology on uranium behavior, which can be applied to develop efficient clean-up strategies.”

Long Lake Gold Mine remediation project hits stumbling block

As reported by the CBC, the Long Lake Gold Mine Remediation Project near Sudbury, Ontario will not be getting started until 2019.

The Province on Ontario first announced its commitment to remediate the abandoned gold mine back in 2013.  The lake, located near a popular recreation area, had high levels of arsenic.

Long Lake Gold mine operated intermittently from 1908 to 1937 and produced approximately 200,000 tonnes of tailings.  The tailings were discharged directly to the environment without containment.  The tailings have since eroded into Luke Creek and Long Lake.  The tailings are acid generating and leach acidic water that is high in metal contamination, specifically arsenic.  The Ontario Ministry of Northern Development and Mines (MNMD) sampling in the south end of Long Lake identified arsenic contamination above the Ontario Drinking Water Standard.

Long Lake (Photo Credit: Markus Schwabe/CBC)

The MNDM initiated a review of remediation alternatives to clean up the tailings area and has selected a preferred method of relocating all fugitive tailings to a new containment facility that will be constructed on site.  The objective of remediation efforts is to reduce the arsenic concentration in Long Lake below the provincial drinking water limit, such that water quality in the south bay of Long Lake will recover to background conditions.

The latest delay in the remediation project is the result of the MNDM addressing some concerns of nearby residents who are concerned that the clean-up will result in increased truck traffic on the existing road to the lake.

The chair of the Long Lake Stewardship group says residents are aware of the notion “short term pain for long term gain” when it comes to the completion of the remediation project.

“But I think the concern I heard was the number of trucks that would be travelling on the road, day-in and day-out through the restoration phase,” Scott Darling said.

“Primarily what I heard in terms of the concerns were the traffic, the increased traffic that’s going to occur over the two-year period on Long Lake Road and Tilton Lake Road and South End Road — the wavy trail.”

Roads in the area will see 50 to 60 trucks a day hauling out contaminated material and bringing in clean fill.

The remediation project is expected to run between two and three years.

Darling says it could be closer to 2019 before the project gets started.

More information on the proposed clean-up of the Long Lake can be found in the MNMD environmental assessment document.