Lichens as Bioindicators of Air Quality
Nash III, Thomas H. , Riddell, Jennifer .
Historical Perspectives and New Opportunities in the Use of Lichens as Air Pollutant Monitors.
BECAUSE lichens are differentially sensitive to several different air pollutants, they are widely used as biomonitors of air quality, although their responses may be quite complex. This introductory presentation briefly covers the historical evidence supporting their use in such investigations. For example, both increasing and more recently decreasing SO2 concentrations have markedly affected lichen distributions. Major impoverishment of lichen floras has also occurred around point sources, such as ones emitting HF. Furthermore, in areas with very high levels of oxidant air pollutants (O3, PAN, etc.), differential sensitivity of lichen species has also been observed, and as documented in this symposium lichen responses to oxidants at lower concentrations is now becoming demonstrable as well. New evidence also presented hereafter is documenting how lichens are also responding to NH3 and NH4+ deposition in both in Europe and California. Potentially HNO3 and HNO2 (both gas phase) may be important as well in the latter area. Because lichens are primarily dependent on atmospheric sources of nutrients, they have developed efficient accumulation mechanisms and consequently can be used as surrogate receptors for heavy metal deposition, as is reviewed in another paper. Lastly two case studies are presented, one for the Pacific Northwest in North America and the other emphasizing the boreal forests of Eurasia.
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1 - Arizona State University, School of Life Sciences, P.O. Box 874501, Tempe, Arizona, 85287-4501, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Tuesday, August 1st, 2006
Time: 8:15 AM