Details

Autor(en) / Beteiligte

• Venturi, S.
• Tassi, F.
• Magi, F.
• Cabassi, J.
• Ricci, A.
• Capecchiacci, F.
• Caponi, C.
• Nisi, B.
• Vaselli, O.

Titel

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

Ist Teil von

• The Science of the total environment, 2019-03, Vol.655, p.887-898

Ort / Verlag

Netherlands: Elsevier B.V

Erscheinungsjahr

2019

Quelle

ScienceDirect

Beschreibungen/Notizen

• Volcanic and hydrothermal areas largely contribute to the natural emission of greenhouse gases to the atmosphere, although large uncertainties in estimating their global output still remain. Nevertheless, CO2 and CH4 discharged from hydrothermal fluid reservoirs may support active soil microbial communities. Such secondary processes can control and reduce the flux of these gases to the atmosphere. In order to evaluate the effects deriving from the presence of microbial activity, chemical and carbon (in CO2 and CH4) isotopic composition of interstitial soil gases, as well as diffuse CO2 fluxes, of three hydrothermal systems from Italy were investigated, i.e. (i) Solfatara crater (Campi Flegrei), (ii) Monterotondo Marittimo (Larderello geothermal field) and (iii) Baia di Levante in Vulcano Island (Aeolian Archipelago), where soil CO2 fluxes up to 2400, 1920 and 346 g m−2 day−1 were measured, respectively. Despite the large supply of hydrothermal fluids, 13CO2 enrichments were observed in interstitial soil gases with respect to the fumarolic gas discharges, pointing to the occurrence of autotrophic CO2 fixation processes during the migration of deep-sourced fluids towards the soil-air interface. On the other hand, (i) the δ13C-CH4 values (up to ~48‰ vs. V-PDB higher than those measured at the fumarolic emissions) of the interstitial soil gases and (ii) the comparison of the CO2/CH4 ratios between soil gases and fumarolic emissions suggested that the deep-sourced CH4 was partly consumed by methanotrophic activity, as supported by isotope fractionation modeling. These findings confirmed the key role that methanotrophs play in mitigating the release of geogenic greenhouse gases from volcanic and hydrothermal environments. [Display omitted] •Greenhouse gases are released from hydrothermal systems through diffuse degassing.•Carbon in CO2 from soil gases is isotopically heavier than that from fumaroles.•CO2/CH4 ratios in soil gases are higher than those measured in fumarolic emissions.•Autotrophs and methanotrophs mitigate the release of geogenic greenhouse gases.•Microbes contribute to regulate CH4 (and CO2) emissions from hydrothermal areas.