SCIENTISTS at the University of Wales, Aberystwyth are developing a laser-based technology that can obtain a detailed record of pollution by unlocking secrets in the shells of molluscs.
Led by Dr Bill Perkins, the team of scientists are working on Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to analyse samples from the layers of calcium carbonate which make up the shells. Layers are added in regular cycles giving a similar effect to the rings created as trees grow.
As these layers are formed pollutants become incorporated or trapped into the shell, locking in a detailed record of activity in the seas.
Long living mollusc species, such as the Arctica islandica clam hold within their records stretching back over two centuries as it grows a new layer of shell every year.
Shorter living species such can provide the scientists with more detailed records. Dr Perkins said while long species leave a historical record dating back decades shorter living molluscs can give more detailed shorter-term information. For example, the cockle creates a very thin new layer with every tide cycle.
The technique has been developed at the University’s Centre for Research in Environment and Health at the Institute of Geography and Earth Sciences.
Dr Perkins said it involves firing a very fine and focused laser beam at the shell producing a hole measuring just a few microns in diameter. “As we fire the beam we can observe the sample through a microscope or camera system in real time.”
The scientists are able to analyse the chemical composition of the samples of shell within minutes. This analysis can include trace metals in very low concentrations, parts per million.
“The small particle is trapped in a stream of gas which we analyse in the mass spectrometer, which is particularly good at looking at trace element particles such a heavy metals.”
The Aberystwyth team’s work has important applications in the field of Environmental Forensics.
Dr Perkins explained that while scientists are able to monitor levels of pollution and long term changes in concentrations the new technique will soon be able to identify when a pollution incident took place and even identify the source.
He said that in the field of environmental forensics he could envisage that rather than scientists taking samples shellfish in containers could be deployed. As they are continuously active they could then be analysed at perhaps weekly or monthly intervals.
The team is currently investigating the effect of dumping of heavily contaminated water from disused mine workings on Parys Mountain, Anglesey, north Wales.
Once one of the world's largest copper-producing sites, it was abandoned in the late 18th century. But water has been building up behind plugs closing tunnels in the mine.
The Environment Agency allowed the release of 200,000 cubic metres of untreated water into the Irish Sea in the first half of 2003, following concerns of flooding with highly acidic waters.
A profile of the pollution and how it is affecting the marine environment is being built up by analysing samples from the shells collected before, during and following the dumping.
University of Wales, Aberystwyth (UWA) was one of the first UK universities to obtain a laser ablation system attached to an inductively coupled plasma mass spectrometer (ICP-MS).UWA has recently acquired a new ICP-MS system which will improve the measurement of isotope ratios.
Dr Bill Perkins, Institute of Geography and Earth Sciences, The University of Wales, Aberystwyth. +44 (0) 1970 622636.
Email: wwwp@aber.ac.uk
