EU backs pollution sensors research

A layer of glass as full of holes as a Swiss cheese, a few chemicals, a computer and a piece of fibre optic cable. These are the unlikely components of a monitoring system that could help reduce the damage from serious water pollution.

Dublin City University's physics department has received EU research support worth £288,500 to develop water pollution sensors which use this collection of technologies. The devices, when built, will be sensitive enough to detect diluted chemicals down to 10 parts per billion, explained Dr Brian MacCraith, who is overseeing the work.

Water pollution is usually detected only after its damage is done; when dead fish are found floating in streams and rivers. The DCU equipment could provide an early-warning system, spotting the arrival of pollution and leaving time for emergency action or quick identification of the culprit.

The funding is for three separate projects, each involving a consortium of EU universities and one of which will be led by DCU. "We have developed a technology for all of these sensors based on a porous glass surface. They can be used for in situ or as disposable monitors," explained Dr MacCraith.

The first, funded by the EU's MAST programme, involves testing for heavy metal pollution in the marine environment, particularly off river estuaries. The second will provide a quick and reliable method for identifying nitrates and nitrites in fresh water. The third is to develop sensors that can identify hydrocarbon compounds in industrial effluent streams. "We are leaders in that project," said Dr MacCraith.

The key to these sensors, a thin film of porous glass, came originally from a research collaboration involving DCU and Trinity College Dublin. The DCU approach is to apply a microscopic film of the special glass to a surface attached to a fibre optic cable. The glass film is structured like a sponge; full of holes which penetrate the surface.

Chemical compounds that react only with specific pollutants are introduced into these holes and are trapped there. They either change colour or fluoresce if a specific pollutant is present in the water.

The glass film is difficult to achieve. It is very thin, one twothousandths of a millimetre thick. By comparison, a human hair is about half a millimetre thick.

One of the most advanced and potentially most commercial sensors being developed detects levels of dissolved oxygen in water. Fish kills usually occur when organic pollutants feed bacterial growth, causing a dramatic - and deadly - depletion of oxygen supplies. Such a sensor could detect minute changes in oxygen levels on a continual basis.