Volatile organic compounds (VOCs) in soil gases from Solfatara crater (Campi Flegrei, southern Italy): Geogenic source(s) vs. biogeochemical processes

Carbon isotopic signature of interstitial soil gases reveals the potential role of ecosystems in mitigating geogenic greenhouse gas emissions: Case studies from hydrothermal systems in Italy

“…Fumarolic gases were collected by inserting a Titanium tube into the fumarolic vent and then, connected to a sampling line consisting of a series of dewared glass tubes (Vaselli et al, 2006), which conveyed the gas into (i) a pre-evacuated 60 mL glass flask, equipped with a Thorion® valve, containing a 4 M NaOH and 0.15 M Cd(OH) 2 suspension (Montegrossi et al, 2001), or (ii) a Graham type condenser connected, through a PTFE three-way valve, to a 12 mL Labco Exetainer® glass vial for the sampling of the dry gas fraction (Tassi et al, 2015a).…”

Biodegradation of CO2, CH4 and volatile organic compounds (VOCs) in soil gas from the Vicano–Cimino hydrothermal system (central Italy)

“…Assuming that Ar concentration depended on AF, which is a reliable hypothesis since Ar is a noble gas, the trends can only be explained by the occurrence of oxidation processes related to (i) microbial activity and/or (ii) chemical reactions involving reduced gas compounds. CH 4 degradation in soil, as well as H 2 S consumption (Smith et al, 1973;Sørensen, 1982;Cihacek and Bremner, 1993), is particularly efficient under aerobic conditions (Potter et al, 1996;Otter and Scholes, 2000;Lerner et al, 2000;Castaldi and Fierro, 2005;Capaccioni et al, 2015), as commonly observed at both municipal waste disposal sites (Barlaz et al, 2004;Stern et al, 2007;Tassi et al, 2011) and volcanic areas (Castaldi and Tedesco, 2005;Tassi et al, 2015). Oxidation of CH 4 gives MeOH that is subsequently transformed to HCHO and then to HCO 2 H. The latter can be converted to CO 2 , or assimilated via biosynthesis for multicarbon compounds by either the ribulose monophosphate pathway or the serine pathway, depending on the microorganism involved (Leberman and Rosenzweig, 2004).…”

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

“…Although the abundances of these gases are commonly considered negligible, they may affect the H 2 S measurements in areas characterized by a specific contaminant source. For example, the bubbling gas exhalations at the Levante beach (Vulcano Island) showed CS 2 concentrations ranging from 2.8 to 8.9 nmol/mol (Tassi et al, 2012), whereas those measured in the Solfatara fumarolic gases were from 156 to 368 nmol/mol (Tassi et al, 2015). However, the corresponding H 2 S contents were remarkably higher (0.42e2.02 and 5.3e15 mmol/ mol, respectively; Tassi et al, 2012Tassi et al, , 2015, therefore the influence of CS 2 on the Radiello ® H 2 S measurements (interference rate: 0.026 mg/m 3 H 2 S per mg/m 3 of CS 2 ; http://www.sigmaaldrich.com/ analytical-chromatography/air-monitoring/radiello/faq.html) was likely negligible.…”