Chemist finds 'cool' way to fish for contaminants  Holger Hintelmann has all but abandoned the "hot" way to trace mercury pollution in the environment for a safer, more accurate one. He is using stable, rather than radioactive, isotopes as his tracers -- largely because they are now commercially available. And because Trent has the equipment and expertise to do it. Analytical chemists like Hintelmann who are interested in the environmental fate of metals have had little choice but to use radioisotopes to trace the fate of metals such as mercury, cadmium, copper, zinc, nickel and lead in soils, water and air. Up to now, scientists have depended on radioisotopes to study the behavior of the heavy metals in the environment because they are easier to distinguish from the naturally occurring non-radioactive mercury. This "enriched" mercury isotope is easily traceable in controlled experiments to measure metal uptake in environment. In lab tests to determine mercury contamination in fish, for instance, it is introduced to the water in which the fish live and the food they eat. It works the same way, say, as a tag attached to a bird's leg. Critical mass of brains Five years ago, stable (non-radioactive) tracer isotopes that worked just as well as radioisotopes became commercially available. But to analyze samples using the stable isotopes required expensive state-of-the-art spectrometers. By happy coincidence, Trent has two of these inductively coupled plasma mass spectrometers (ICP/MS) as well as the "critical mass of brains" -- environmental chemists, geologists and biologists -- to experiment with the new technique. "For us it was an obvious thing to do," says Hintelmann, who has forged new ground in the past two years by using stable mercury isotopes to analyze the uptake of metals in aquatic organisms. "We saw problems in other studies where they used radioactive metals and there weren't really answers to the questions we needed." With this new method, Hintelmann has begun to gather data on the path and levels of mercury contamination in algae, zooplankton and fish. Eventually he hopes to determine how, as well as how much of, a metal is absorbed and accumulated in aquatic organisms from the water and from their diet. "It's rather easy to measure total metal concentration in a river" by analyzing the sediment or the water, says Hintelmann. Now "the challenge is to figure out which fraction of this metal is available for uptake by fish" and other organisms. "In five years from now, we will probably see a lot more studies with this kind of technique and it has the potential to replace the techniques and studies using radioactive metals." Hintelmann has just been appointed junior research chair of environmental modelling to expand the work of senior research chair Don Mackay. Where Mackay has been developing mathematical models for predicting the fate of organic chemical pollutants like PCBs and chlorines in the environment, Hintelmann will concentrate on heavy metals like mercury, copper, zinc, cadmium and lead. |
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Last updated: September 26, 1997