Monitoring of Airborne Mercury: Comparison of Different Techniques in the Monte Amiata District,Southern Tuscany, Italy

In the present study, mercury (Hg) concentrations were investigated in lichens (Flavoparmeliacaperata (L.) Hale, Parmelia saxatilis (L.) Ach., and Xanthoria parietina (L.) Th.Fr.) collected in thesurrounding of the dismissed Abbadia San Salvatore Hg mine (Monte Amiata district, Italy). Resultswere integrated with Hg concentrations in tree barks and literature data of gaseous Hg levelsdetermined by passive air samplers (PASs) in the same area. The ultimate goal was to compare resultsobtained by the three monitoring techniques to evaluate potential mismatches. Lichens displayed180-3600 ng/g Hg, and Hg concentrations decreased exponentially with distance from the mine.Mercury concentration was lower than in Pinus nigra barks at the same site. There was a moderatecorrelation between Hg in lichen and Hg in bark, suggesting similar mechanisms of Hg uptakeand residence times. However, correlation with published gaseous Hg concentrations (PASs) wasmoderate at best (Kendall Tau = 0.4-0.5, p > 0.05). The differences occurred because a) PASs collectedgaseous Hg, whereas lichens and barks also picked up particulate Hg, and b) lichens and bark had adynamic exchange with the atmosphere. Lichen, bark, and PAS outline different and complementaryaspects of airborne Hg content and efficient monitoring programs in contaminated areas wouldbenefit from the integration of data from different techniques.