Atmospheric Deposition Of Volcanogenic Major And Trace Elements On Mt. Etna (Italy)

There are a variety of natural and anthropogenic sources of trace elements into the environment, and human activity has drastically changed the biogeochemical cycles and balance of several elements. In the last twenty years many efforts have been spent by the scientific community to better outline the levels of pollutants in the environment on a long-term basis, and to evaluate global large-scale changes. It is generally accepted that volcanic emissions are an important source of gases and particles to the atmosphere, contributing significantly to the natural geochemical cycles of all elements (Nriagu, 1989; Hinkley et al., 1999; Oppenheimer, 2003). Many studies have been carried out on the main volcanic emitters of the world, to estimate and characterise their emissions (Gauthier and Le Cloarec, 1998; Hinkley et al., 1999; Cheynet et al., 2000; Allard et al., 2000 Aiuppa et al., 2003; Bagnato et al., 2007). By contrast, the atmospheric deposition of trace elements around active volcanoes is poorly constrained. From a literature review, we have recognized the scarcity of investigations on trace element deposition in the surroundings of active volcanoes. Although active volcanoes are widely distributed in the world and their emissions plays a key role on the global geochemical cycles of many elements, only Hawaiian, Japanese, Italian and a few central American volcanoes have been studied from the point of view of major species atmospheric deposition. This research focuses on the relevant question of the fate of trace metals emitted by an active volcano such as Mount Etna (Italy), and attempts to answer this question by reviewing and interpreting the results of an unprecedented set of trace elements analyses in Etna’s precipitation, collected over two years of periodic sampling. The first part of this work is aimed at updating earlier estimates of elemental fluxes released from the volcano, by using classical methodologies. Original data on aerosols chemistry and fluxes, among with the previous estimates, were essential to quantify the volcanic source. The second section, focuses on the characterization of atmospheric bulk deposition around the volcano. The obtained large dataset on major, and trace elements concentrations in atmospheric precipitation was used to estimate the deposition rates of the same suite of elements. Finally, in the last part of the thesis, the results for volcanic emissions are compared with atmospheric deposition to highlight the effects of the volcano at local and regional scale.