A biomonitoring study using endemic plants for the evaluation of volcanogenic deposition on Mt. Etna (Italy)

8. A biomonitoring survey using leaves of tree (Betulla aethnensis, Pinus nigra and Populus tremula) and two endemic species (Senecio aethnensis and Rumex aethnensis) above treeline level, was performed on Mt. Etna, in order to evaluate the dispersion and the impact of volcanic emissions. Samples of leaves were collected in summer 2008 from 30 sites in the upper part of the volcano (800-3000 m a.s.l). Acid digestion of samples was carried out with a microwave oven, and 44 elements were analyzed by using plasma spectrometry (ICP-MS and ICP-OES). The highest concentrations of all investigated elements were found in the samples collected closest to the degassing craters, and in the downwind sector, confirming that the eastern flank of Mt. Etna is the most impacted by volcanic emissions. Leaves collected along two radial transects from the active vents on the eastern flank, highlight that the levels of metals decrease one or two orders of magnitude with the distance from the source. This variability is higher for volatile elements (As, Bi, Cd, Cs, Pb, Sb, Tl) than for more refractory elements (Al, Ba, Sc, Si, Sr, Th, U). The different species of plants show significant differences in the bioaccumulation of most of the analyzed elements, in particular lanthanides, which are systematically enriched in Rumex leaves. The high concentrations of many toxic elements in the two endemic species allow us to consider these plants as highly tolerant species to the volcanic emissions, and suitable for biomonitoring researches.