Proton-beam Analysis of Lichens

Dr. Lawrence Rees
Department of Physics and Astronomy
Brigham Young University

We are primarily familiar with lichens as the crusty growths on rocks or tree bark, but they come in a variety of growth forms and can be found just about anywhere on the earth. Because of their relatively simple structure and their sensitivity to pollutants, lichens have been considered to be useful as long-term monitors of environmental quality.

Over the past several years, we have conducted an extensive study of lichens using such accelerator-based techniques as particle-induced x-ray emission (PIXE) spectroscopy, microbeam PIXE, and accelerator mass spectroscopy (AMS). Our principal aim has been to establish baselines of trace element concentrations in a variety of lichens indigenous to western North America.  In the process, we have discovered some interesting things about the structure, growth, and chemistry of lichens.