Fibre-optic sensor arrays for testing of water contamination

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Contamination of the environment with heavy metals such as mercury is a continuing threat to human health and the ecosystem.  Coal-fired plants are the main source of mercury emissions, producing an estimated 350,000 lbs/year in the US.  Many of these plants have been in operation since 1960's and have absolutely no equipment to reduce emissions, but they produce 53% of the electricity in the US by a process that is among the world's cheapest.  Global emissions are at almost 12 million lbs/year, predicted to increase along with China and India's increasing electricity needs and aging infrastructure. Pollutants other than mercury can enter groundwater by a variety of pathways.  In order to prevent contamination, monitoring around industrial and military sites, waste management sites, and water conservation and intake areas is critical.  Regulations require testing of groundwater samples at 5 locations around a landfill, for 25 years after it has been closed.  However, the cost of the analysis (minimum $250 per sample per well) limits the frequency of the testing to only four times a year.  Such infrequent testing does not allow for fast intervention should leachate from a landfill enter the ground water supply. We plan to develop an inexpensive, portable, real-time sensor for a large variety of ground water contaminants.  The key part of the sensor is a fibre optic cable that is customized to allow a controlled loss of some of the light normally contained within the fibre core.  The amount of light lost is affected by the environment immediately outside the cable.  Loock and Brown have shown that polymers that selectively absorb organic contaminants such as aromatic hydrocarbons can be placed on the exterior of the cable, resulting in detection of toluene and other hydrocarbons.  The same measurement principle can be applied to the detection of metal ions.  Crudden, Loock and Brown are currently testing organic/inorganic composites, which contain a large proportion of thiol groups known to bind mercury.  Related composites are known to bind up to 0.7 grams of mercury per gram of material