Geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from Mt. Etna and Vulcano Island (Sicily, Italy)

[1] In this paper, fluid source(s) and processes controlling the chemical composition of volatile organic compounds (VOCs) in gas discharges from Mt. Etna and Vulcano Island (Sicily, Italy) were investigated. The main composition of the Etnean and Volcano gas emissions is produced by mixing, to various degrees, of magmatic and hydrothermal components. VOCs are dominated by alkanes, alkenes and aromatics, with minor, though significant, concentrations of O-, S- and Cl(F)-substituted compounds. The main mechanism for the production of alkanes is likely related to pyrolysis of organic-matter-bearing sediments that interact with the ascending magmatic fluids. Alkanes are then converted to alken…

Composition and distribution of volcanic gases inside the Lakki Caldera (Nisyros, Greece): preliminary results

Geosphere-biosphere interactions in bio-activity volcanic lakes: Evidences from Hule and Rìo Cuarto (Costa Rica)

Hule and R ́ıo Cuarto are maar lakes located 11 and 18 km N of Poa ́s volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemica…

Escalating CO2 degassing at the Pisciarelli fumarolic system, and implications for the ongoing Campi Flegrei unrest

Abstract This short communication aims at providing an updated report on degassing activity and ground deformation variations observed during the ongoing (2012–2019) Campi Flegrei caldera unrest, with a particular focus on Pisciarelli, currently its most active fumarolic field. We show that the CO2 flux from the main Pisciarelli fumarolic vent (referred as “Soffione”) has increased by a factor > 3 since 2012, reaching in 2018–2019 levels (>600 tons/day) that are comparable to those typical of a medium-sized erupting arc volcano. A substantial widening of the degassing vents and bubbling pools, and a further increase in CO2 concentrations in ambient air (up to 6000 ppm), have also been detec…

First simultaneous mercury and major volatiles characterization of atmospheric hydrothermal emissions at the Pisciarelli's fumarolic system (Campi Flegrei, Italy)

Abstract Hydrothermal systems with active surface expressions are important natural source of atmospheric mercury. Here we report on the first simultaneous assessment of gaseous elemental mercury (GEM) and major volatiles (H2S and CO2) fluxes from the fumarolic system of Pisciarelli, currently the most active at the Campi Flegrei caldera (CFc), Naples (Italy). This was achieved via a GPS-synchronized Lumex and MultiGAS survey which extends similar investigations reported elsewhere. GEM concentrations measured in the fumarolic emissions were consistently above background air level close to the degassing area (mean ~ 8 ± 3 ng m−3 on average) and ranged up to 12,000 ng m−3. Our data evidenced …

Hydrogen sulfide measurements in air by passive/diffusive samplers and high-frequency analyzer: A critical comparison

In this study, hydrogen sulfide (H2S) measurements in air carried out using (a) passive/diffusive samplers (Radiello® traps) and (b) a high-frequency (60 s) real-time analyzer (Thermo® 450i) were compared in order to evaluate advantages and limitations of the two techniques. Four different sites in urban environments (Florence, Italy) and two volcanic areas characterized by intense degassing of H2S-rich fluids (Campi Flegrei and Vulcano Island, Italy) were selected for such measurements. The concentrations of H2S generally varied over 5 orders of magnitude (from 101e103 mg/m3), the H2S values measured with the Radiello® traps (H2SR) being significantly higher than the average values measure…

The Hydrothermal System of the Campi Flegrei Caldera, Italy

In this chapter, we review the state-of-the-art of the Campi Flegrei caldera (Naples) hydrothermal system, and its behaviour during the last decades. The Campi Flegrei caldera has been undergoing unrest since 1950, as evidenced by recurrent bradyseismic episodes accompanied by manifest changes in the degassing budget, degassing patterns and in the composition of the fumarolic fluids. In-depth analysis of geochemical and geophysical datasets acquired over decades has allowed identification of the mechanisms driving volcanic unrest at the Campi Flegrei caldera. We propose a conceptual model of the hydrothermal system feeding Solfatara fumaroles, where geochemical information is integrated wit…