Tree-lined mass spectrometry
Trees provide environmental scientists with a living detector system for tracking pollutants, according to Cameron McLeod, speaking at the RSC's Annual Conference 2000 recently.
McLeod, Director of the Centre of Analytical Sciences at the University of Sheffield, says there is no truly effective way of measuring the levels of air-borne pollutants such as arsenic, lead, chromium, mercury and radionuclides such as uranium, over long periods of time. Understanding long-term trends in such species is crucial in visualising the impact of human activity on the environment and the air we breathe.
He believes, however, that the bark of a tree can act as a passive atmospheric sampler. As a tree grows, it's bark takes in pollutants from the air. In time, this bark is incorporated within the trunk of the tree, forming a so-called "bark pocket". He and his colleagues are tapping into this natural database to look closely at the history of air pollution in the UK. Obviously, the technique would be equally applicable from Albania to Zanzibar.
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| UK researchers are finding trees can simply sense pollution |
By using laser ablation-ICP mass spectrometry, the Sheffield scientists can determine the nature and level of pollutants within each "bark pocket". They can then utilise standard tree-dating techniques and correlate the period in time at which each bark pocket was formed and so deduce what the air around a tree was like at a very precise point in history.
The presence of particular pollutants, McLeod explains, can then be traced to specific sources such as coal burning, waste incineration, vehicle exhaust or steel production. The technique will, he adds, for the first time, provide a way to monitor the levels of airborne pollutants and help us learn about the long-term environmental impact of
industrial processes.
