DETERMINING THE EFFECT OF TREE CANOPY AND LICHEN SPECIES ON SORPTION CAPABILITIES OF LICHENS

Lichens have been proposed as passive, air-quality biomonitors because they are ubiquitous, cheap, and highly sorptive. However, their sorption mechanisms are still poorly understood, leaving some questions about atmospheric deposition data obtained from lichens. Previous studies have not examined the effects of canopy type (deciduous or coniferous) and lichen species (H. physodes or F. caperata) when analyzing pollutant concentrations sorbed to lichens. The results of leaching experiments on lichens from Binghamton, NY were compared with atmospheric deposition samples and lichens collected from the Athabasca Oil Sands Region (AOSR), Alberta, Canada in order to decipher the potential effects of both canopy type and lichen species. Differences in ion concentrations revealed greater inputs from deciduous canopies than coniferous canopies. Lichen species also affects pollutant sorption, as H. physodes presented higher concentrations of minor elements while F. caperata contained higher concentrations of major elements. Results from leaching experiments provided insights into which metals were adsorbed to the surfaces of lichens and which were absorbed into the lichens themselves. These results help clarify sorption mechanisms of lichens and increase confidence in interpreting previous, as well as future, uses of lichens as inexpensive, air-quality biomonitors.