Epilithic lichen - Atmospheric deposition monitors of trace elements and organohalogens?

Epilithic lichen (Xanthoria elegans in Canada, Lecanora muralis in Germany) were gathered from 17 locations in Ontario, Canada (from Lake Ontario to J ames Bay) and 43 locations in Germany (from the Alps to the North Sea and f rom the Baltic Sea to the Erzgebirge). Sample aliquots were digested in nit ric acid and trace elements were analyzed by inductively coupled plasma-mas s spectrometry techniques. The organohalogens were determined as absorbable organic halogens (AOXs) by coulometry. Concentration ranges from Germany f or trace element samples and AOXs were determined. The lichen showed high s patial resolution in their element enrichment patterns. This allowed for di fferentiation between natural and anthropogenic dominance in ambient air co ncentrations. This biomonitoring method has proven to be very sensitive, fa st, and reliable. No clear relationship could be found between trace elemen t and AOX concentrations. The AOX values may reflect individual metabolic r ates of the fungal partner in lichen symbionts.