THE UPTAKE OF METAL IONS BY LICHENS: A MODIFIED ION‐EXCHANGE PROCESS

SUMMARY Heavy metal ions were absorbed by lichens to different degrees in laboratory experiments. The relative capacities for uptake from solutions containing a single metal ion were Fe, Cu>Ni>Pb>Co>Zn. Competitive uptake studies revealed the selectivity sequence Fe>Pb>Cu>Ni, Zn>Co. The sequences are in accord with a cation uptake mechanism involving ion exchange modified by metal‐complex formation. Correlations between laboratory studies and the metal content of lichens growing in the vicinity of a smelter are discussed.