Autoradiography

Lichens are also able to pick up and store radioactive fall-out, especially caesium and strontium. The radioactivity harms particularly the cells which are part of the reproductive phase, such as the spores of the fungi. Exposing x-ray film to radioactive lichens will leave spots or even the outline of the lichen on the film, thereby revealing the history of their exposure to radioactivity. Perhaps your local hospital would make an x-ray film available for your use. Place the lichen on top of a black x-ray package and let it sit there for two weeks. Then develop the film.

Although it may seen utterly unlikely that you would find any radioactivity in your lichens, some schools may find "positive" results. After atomic testing both Alaskan Eskimos and Scandanavian Laplanders were found to have high levels of radioactive contamination, which they had absorbed from eating reindeer, which in turn ate lichens. The Chernobyl reactor accident brought similar dangers.

Some classes might find it an interesting exercise to sample with a geiger counter and begin to address some of the issues of radioactive waste disposal. An inexpensive geiger counter available for classrooms is one made by the Radalert Company of California. It runs about $225 as a kit and $300 assembled. Hand-sized, it can be left counting, and gives total counts.

Richard Borst's class in South Carolina did indeed find a higher radiation count in the lichen taken from the Savannah River Plant.

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