A team of scientists from the Universities of Leeds and Manchester have joined forces with experts in nuclear medicine at Manchester Royal Infirmary, using medical gamma-ray cameras to track radioactive isotopes in soil samples from a US civil nuclear site.

This is the first time the technique, which is used in hospitals for heart, bone and kidney scanning, has been used to study the environmental behaviour of nuclear waste - and its success could help scientists find new ways of using bacteria to control the spread of radioactivity.

Radioactive isotopes of the element technetium (Tc) are produced in bulk by nuclear facilities, while a specific isotope of Tc with a very short life is routinely used as a medical tracer in human bodies.

Nuclear fission of Uranium has released tonnes of Tc from nuclear facilities over the past decades, with the element remaining radioactive for thousands of years.

But although the short lived medical isotope is chemically indistinguishable from that in long lived waste, it can be used safely in tests.

In the study, Manchester researchers took soil samples from the Oak Ridge nuclear facility in the United States and successfully tracked the movement of medical Tc through the soil.

Scientists at the University of Leeds, led by Dr Ian Burke, were then asked to verify the observations using a special microscope technique called Transmission electron microscopy (TEM).

With the help of DNA analysis the researchers confirmed that certain microbes - and particularly some that use ferric iron for energy - can fix Tc in place in soils.

They also found that nearly all the Tc remained fixed when ferric iron was present with these 'iron-reducing' bacteria.

This finding itself is not new - Professor Jon Lloyd, from the University of Manchester and his colleagues had previously reported that microbes in laboratory cultures could perform this role in fixing Tc.

But the researchers' success in using the gamma camera could see the technique being used to probe how Tc and ferric iron move together in far more complex soil systems more representative of the 'real world' - helping develop future remediation techniques. 

Prof Lloyd said: "Using this medical scanning technique we were able to explore, in real time, the mobility of one of the most problematic and mobile radionuclides in sediments."

Dr Burke added: "Leeds scientists established the protocols necessary to apply high resolution electron microscopy techniques to samples radioactively contaminated with Tc. This produced very novel insights into the way this contaminant metal binds in sediments and will help to predict how easily it will spread in the environment."

Notes to editors

Prof Lloyd is available for comment by arrangement. For more information please contact Alex Waddington, Media Relations Officer, UoM, Tel 0161 275 8387 / 07717 881569.

Alternatively, contact the University of Leeds press office on 0113 343 4031 or email pressoffice@leeds.ac.uk.

The research was published in a special edition of the American Chemical Society journal Environmental Science and Technology. A copy of the paper, 'Probing the Biogeochemical Behaviour of Technetium Using a Novel Nuclear Imaging Approach' is available on request.

Dr Burke of the University of Leeds School of Earth and Environment is also a co-author on the paper, 'Fate of technetium in reduced sediments: comparison of direct and indirect analysis,' which is published in this month's Applied Geochemistry.