Contents
| AIR HYGIENE REPORT no. 10 | |
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Contents |
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Plants have the ability to indicate the presence of elements and their concentration gradients. Mosses and lichens are particularly effective biomonitors of aerial heavy metal contamination because of their bioaccumulative properties. These plant groups are amenable to biomonitoring because they are widespread, easy to handle and they lack a cuticle and root system thus reflecting directly aerial heavy metal deposition. Most surveys use passive monitoring and active monitoring is used infrequently. Analysis of indigenous mosses are currently used in international and national monitoring programmes, particularly in Europe. Techniques are applied as a practical tool in establishing and characterising deposition sources. Such long-term, larger scale monitoring is extremely useful and also enables transboundary ameliorative action to be taken. Both lichens and moss techniques have been applied to measure heavy metal levels and trends within and around urban and industrial areas. These studies can analyse temporal and/or spatial trends in heavy metal deposition and results are generally expressed as pollution gradients. Within the gradient, metal levels in the local moss populations are seen to decrease with increasing distance from the suspected source.
The use of fungi in the monitoring of heavy metal pollution is limited but some fungal groups are better bioaccumulators than others.
Higher plants have appeal as indicators in air pollution monitoring in highly polluted areas where lichens and mosses are often absent. They are primarily used as bioaccumulators. The use of higher plants in the assessment of aerial heavy metal contamination is hampered by their inherent ability to absorb metals from the soil. Interpretation of results should therefore be handled with caution. However, metal accumulation in plants does reflect the relative extent of the pollution burden and its dispersal. Analysis of leaves and needles are common techniques but tree bark has also been used in heavy metal biomonitoring. It is often useful to include analysis of plant roots as a means of assessing pollution contributions from soil.
The use of physiological and biochemical parameters in the bioindication of heavy metal contamination is not routinely practised. Some responses of higher plants to heavy metal contamination have potential. Very few examples of using species distribution and mapping methods in the assessment of heavy metal pollution exist.
It is important during metal biomonitoring programmes that background concentrations are established. The design of a monitoring programme will involve the selection of appropriate species, sampling locations, sample collection, sampling frequency, metals to be analysed, chemical technique and data analysis. References
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