The chemical composition of rainwater was studied in two highly-industrialised areas in Sicily (southern Italy), between June 2018 and July 2019. The study areas were characterised by large oil refining plants and other industrial hubs whose processes contribute to the release of large amounts of gaseous species that can affect the chemical composition of atmospheric deposition As in most of the Mediterranean area, rainwater acidity (ranging in the study area between 3.9 and 8.3) was buffered by the dissolution of abundant geogenic carbonate aerosol. In particular, calcium and magnesium cations showed the highest pH-neutralizing factor, with ~92% of the acidity brought by SO₄²⁻ and NO₃⁻ neutralized by alkaline dust. The lowest pH values were observed in samples collected after abundant rain periods, characterised by a less significant dry deposition of alkaline materials. Electrical Conductivity (ranging between 7 µS cm⁻¹ and 396 µS cm⁻¹) was inversely correlated with the amount of rainfall measured in the two areas. Concentrations of major ionic species followed the sequence Cl⁻ > Na⁺ > SO₄²⁻ ≃ HCO₃⁻ > ≃ Ca²⁺ > NO₃⁻ > Mg²⁺ > K⁺ > F⁻. High loads of Na⁺ and Cl⁻ (with a calculated R² = 0.99) reflected proximity to the sea. Calcium, potassium, and non-sea-salt magnesium had a prevalent crustal origin. Non-sea salt sulphate, nitrate, and fluoride can be attributed mainly to anthropogenic sources. Mt. Etna, during eruptive periods, may be also considered, on a regional scale, a significant source for fluoride, non-sea salt sulphate, and even chloride.

Relationship between soil CO2 flux and tectonic structures in SW Sicily

Air permeability is a major physical factor affecting the advective transport of a gas through the soil, and variations in this parameter can strongly influence the emission of endogenous gases from the soil to the atmosphere. In this paper, we illustrated a new and simple method for measuring in situ air permeability based on the measurement of air pressure inside a special probe inserted into the soil. The method was designed and developed primarily to study the relationship between air permeability and the soil CO₂ flux in an active volcanic area. The method was used for continuous monitoring of the air permeability at two different locations on the island of Vulcano. At the same time, the values of the atmospheric pressure, temperature, rain, and volumetric water content of the soil were also acquired to investigate their effect on soil air permeability and soil CO₂ flux. The results showed that during the monitoring period, soil air permeability exhibited minor variations at each site, while larger variations in the soil CO₂ flux were recorded. The effect of soil air permeability on soil CO₂ flux was negligible at both sites, whereas a strong dependence of soil CO₂ flux on volumetric water content and on atmospheric pressure was found. Furthermore, the variation in air permeability recorded at both sites was much lower than that predicted using some well‐known predictive models, showing that the relationship among different soil transport parameters is more complex in real field conditions than would be expected by semiempirical models.