Speedy test for soil toxicity uses bioluminescent bacteria

Developed over seven years by scientists at the University of Aberdeen, and recently granted Millennium Product status, the biological sensor process means that diagnosis and cleanup can be carried out in a fraction of the time taken by conventional surveys.

“Because of the potential costs of cleaning up polluted sites – let alone the legal implications – no developer can afford to purchase or build on a site without knowing what is in the ground,” Ian George, managing director of Remedios told Industrial Environmental Management magazine. “There is a need for a quick, reliable and cost-effective test of soil toxicity. Our biosensor technology will satisfy that demand.”

The biosensors work using a phenomenon, familiar to seafarers, called bioluminescence. Disturbance of sea water acts to mix up naturally-occurring bacteria with oxygen, resulting in a luminescence in the water – the reason why sea water at the bow of a ship, or falling from oars, often glows at night. Scientists at the University of Aberdeen have taken the gene that causes this glow and inserted it into bacteria that thrive in soil.

When the bioluminescent bacteria are presented with a sample which has any toxicity which they can absorb (‘bioavailable toxicity’), the light output produced by the bioluminescence will decrease in direct proportion to the toxin level, giving a measure of the toxicity of the sample. The Remedios biosensor technology can reveal the presence of ten groups of toxic substances including:

• heavy metals
• soluble pesticides
• corrosive chemicals and explosives.

Such is the sensitivity of the biosensor that it can detect heavy metals in concentrations as low as 1ppm.

Traditionally, toxicity of contaminated soil is determined by selecting chemicals for testing on the basis of known history of the site. This entails taking a huge number of samples and analysing each one for individual chemical contaminants. If a particular chemical is not suspected, it is likely that the test for this will be omitted. There is, therefore, a danger of a toxin being missed. Such a process takes considerable time and provides only broad information on the total toxin content in soil or water.

As a result, clean-up proposals tend to centre on the removal of large volumes of potentially-contaminated material from the site and its replacement with clean material. In stark contrast, biosensor technology does not require any prior knowledge of contaminants likely to be present on a site. In addition to the benefits offered in terms of speed and testing the overall toxicity of a site, the Remedios technique also helps identify possible biological solutions for the clean-up of the land. Using this information, many sites can be remedied without the costly process of removing, disposing and replacing contaminated material.

The technology has already been successfully tested at a number of sites in the UK and Germany. At one of the UK sites – the former gas plant and chemical works which are now part of the Scotoil Group site in Aberdeen – the biosensor technology was piloted on an area which was already well documented using conventional soil sample analysis. Using the biosensor technology, Remedios produced their results in 12 days. The accuracy of the biosensors was shown by the fact that the results correlated with those taken over a number of years using conventional sampling techniques. The biosensors also revealed an unexpected chemical contamination that had not been identified in the traditional surveys.

Professor Duncan Rice, Principal of the University of Aberdeen – a shareholder in Remedios Ltd – said: “Remedios is a wonderful example of the enormous benefits which can result from industry and academic collaboration. It will provide environmental diagnostics services to industry and other users, and will speed up the process of diagnosis, risk assessment and solutions to contaminated land and, therefore, the decision making process on planning and development of such sites.”