Major and trace elements characterization of atmospheric deposition in volcanic, urban, and industrial areas of Sicily (Italy): preliminary results

Abstract

The source of chemical elements dissolved in rainwater can be both natural and anthropogenic. A group of trace elements has been recently brought to attention for their possible environmental impacts, the Technology-critical elements (TCEs). The current knowledge about the geochemical cycle of TCEs is still scarce, nevertheless recent studies [e.g. Brugnone et al., 2020] evidenced a contribution from the volcanic activity for some of them (Te, Tl, and REE). Our research aims to produce a geochemical database on major and trace element depositions in different areas of Sicily: a volcanic area (Etna), two urban areas (Palermo, Catania), two industrial areas (Milazzo, Priolo), and a rural monitoring site (Cesarò). The samples are collected monthly through a network of 15 bulk collectors. Here we report about the chemical composition of rainwater from the first five sampling campaigns. The pH was between 5.5 and 7.8, with an average value of 7.0. EC showed values ranging from 8 to 184 μS/cm, with an average of 72 μS/cm. The most abundant major elements were Cl- and SO42- for anions, Ca+ and Na+ for cations. Regarding trace elements, the highest volume-weighted mean (VWM) concentrations were generally measured in the areas affected by volcanic emissions, especially for TCEs, such as Te and Tl, which show VWM concentrations of 4.5 ng/L and 50.8 ng/L, respectively, higher than the VWM values detected in samples far from the volcanic source (0.8 ng/L and 2.5 ng/L, respectively). Exceptions are Zn and Br with the highest VWM concentration found in the Priolo area, Cr and Fe in Palermo. The contribution of the various sources, including the volcanic one, can therefore be well evidenced through the characterization of the chemical composition of the atmospheric deposition.