Research article

Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO₂ and H₂O concentration and soil degassing at Vulcano (Aeolian islands: Italy)

Maurizio De Rosa¹ , Gianluca Gagliardi¹ , Alessandra Rocco¹ , Renato Somma² , Paolo De Natale¹ and Giuseppe De Natale²

¹CNR, Istituto Nazionale di Ottica Applicata, Sezione di Napoli, Via Campi Flegrei 34, I-80078 Pozzuoli (NA), Italy

²INGV, Osservatorio Vesuviano, Via Diocleziano 328, I-80124 Napoli, Italy

author email corresponding author email

Geochemical Transactions 2007, 8:5doi:10.1186/1467-4866-8-5

Published:	20 April 2007

Abstract

We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO₂ and H₂O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-μm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO₂ and H₂O concentrations, and CO₂ soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater – FOG- and Valley of Palizzi, PAL). CO₂/H₂O values, measured on the ground, are very similar (around 0.019 (± 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS – Baia Levante beach) obtaid during the 1977–1993 heating phase of the crater fumaroles.

In this work much more homogeneous values are found in different points of the three sites investigated. The field work, although carried out in a limited time window (25th–28th August 2004), pointed out the new apparatus is suitable for continuous gas monitoring of the two species and their ratios, which are important geochemical indicators of volcanic activity, for which other reliable continuous monitoring systems are not yet available.