Comparison of the trace element content in transplants of the lichen Evernia prunastri and in bulk atmospheric deposition: a case study from a low polluted environment (C Italy)

This study investigated whether lichen samples transplanted and retrieved monthly for six months reflect bulk deposition under conditions of relatively low air pollution. The study investigated also whether samples exposed for six months provide data consistent with the one-month transplants. The lichen Evernia prunastri was collected from a remote site and exposed at a study site (the Botanical Garden of the University of Siena, Italy), along with an atmospheric bulk deposition collector. Lichens and bulk deposition were analysed by ICP-MS for the content of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Ti and Zn. The results showed significant correlations between lichen content and bulk deposition for Al, As, Cu, Fe, Hg, Sb and Ti, suggesting that in one month the equilibrium is reached for these elements between the lichen and the atmosphere. The above elements (but Sb) in lichen and bulk deposition are related to soil-particulates, while traffic is the source for Sb deposition. In addition, samples exposed for 6 months showed results consistent with the one-month transplants for As, Cu and Hg, suggesting that for these elements in the study site the equilibrium is maintained also for longer periods.