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Abstract: Fluorine adsorption experiments were performed on 28 samples of the first 5cm of topsoil collected on the flanks of Mt. Etna. The soil samples were equilibrated with F-rich rainwater (3.25mg/L) at a soil/water weight ratio of 1/25. Aliquots of the supernatant were collected after 1, 7, 72, 720 and 5640h and analysed for F content. The soil samples could be subdivided into three groups based on their F-adsorption behaviours after 1h and at the end of the experiment: (1) negative adsorption (F released from the soil to the solution) after 1h and negative or moderately positive adsorption at the end, (2) from negative after 1h to strongly positive adsorption at the end, and (3) always strong positive adsorption. The adsorption capacity of the soils was positively correlated with the soil pH, the contents of finer granulometric fractions (clay and silt) and the weathering stage (as quantified by the chemical alteration index). The most F adsorbing soils are found at the periphery of the volcano where aquifers are more vulnerable to contamination due to the shallower depth of the water table. This study further evidences the importance of the Etnean soils in protecting groundwater from an excessive magmatic F input. [Copyright &y& Elsevier]

Abstract: The sustained and uninterrupted plume degassing at Mount Etna volcano, Southern Italy, represents the troposphere''s most prominent natural source of fluorine. Of the ∼200 Mg of fluorine (as HFg) emitted daily by the volcano, 1.6±2.7 Mg are deposited by wet and dry deposition. Fluorine-deposition via volcanic ash, here characterised for the first time, can be quite significant during volcanic eruptions (i.e. 60 Mg of fluorine were deposited during the 2001 eruption through volcanic ash, corresponding to ∼85% of the total fluorine deposition). Despite the fact that these depositions are huge, the fate of the deposited fluorine and its impact on the environment are poorly understood. We herein present original data on fluorine abundance in vegetation (Castanea Sativa and Pinus Nigra) and andosoils from the volcano''s flank, in the attempt to reveal the potential impact of volcanogenic fluorine emissions. Fluorine contents in chestnut leaves and pine needles are in the range 1.8–35 μg/g and 2.1–74 μg/g respectively; they exceed the typical background concentrations in plants growing in rural areas, but fall within the lower range of typical concentrations in plants growing near high fluorine anthropogenic emission sources. The rare plume fumigations on the lower flanks of Mt Etna (distance>4 km from summit craters) are probably the cause of the “undisturbed” nature of Etnean vegetation: climatic conditions, which limit the growth of vegetation on the upper regione deserta, are a natural limit to the development of more severe impacts. High fluorine contents, associated with visible symptoms, were only measured in pine needles at three sites, located near recently-active (2001 to 2003) lateral eruptive fractures. Total fluorine contents (F TOT) in the Etnean soils have a range of 112–341 μg/g, and fall within the typical range of undisturbed soils; fluorine extracted with distilled water (F H2O) have a range of 5.1 to 61 μg/g and accounts for 2–40% of F TOT. F H2O is higher in topsoils from the eastern flank (downwind), while it decreases with depth in soil profiles and on increasing soil grain size (thereby testifying to its association with clay–mineral-rich, fine soil fractions). The fluorine adsorption capacity of the andosoils acts as a natural barrier that protects the groundwater system. [Copyright &y& Elsevier]

Abstract: Travertine deposits outcropping in the lower SW flank of Mt. Etna were studied for their mapping, as well as for their chemical, mineralogical and isotopic compositions. These deposits are dated to about 24 to 5 ka in the Adrano area, located at the western limit of the study area. In this area travertines show high Mg contents and are composed mostly of dolomite, thus apparently ruling out any primary deposition in favour of a diagenetic origin. Travertines outcropping near Paternò, in the east part of the study area, should be younger than 18 ka. Those located to the SSW of Paternò (Paternò–Diga) show high Sr contents and aragonite as dominant mineralogical phase, thus suggesting primary deposition. Those located to the W of Paternò (Paternò Simeto–Stazione) are instead poor both in Mg and in Sr and show calcite as dominant phase. Carbon isotope composition of travertines indicates a magmatic origin of CO2 that formed them. Based on the estimated volume of travertines, between 10 and 20 Gg/a of CO2 were involved in their formation. The time-span of travertine formation coincided with the eruptive cycles of Ellittico and the first part of Mongibello, which were probably characterised by a greater amount of CO2 transported through groundwater circulation. Widespread travertine deposition probably ceased after the opening of the Valle del Bove depression that modified the volcanologic and hydrologic conditions in the summit crater area. [Copyright &y& Elsevier]