Articles | Volume 11, issue 1
Research article
15 Jan 2018
Research article |  | 15 Jan 2018

Diode laser-based gas analyser for the simultaneous measurement of CO2 and HF in volcanic plumes

Antonio Chiarugi, Silvia Viciani, Francesco D'Amato, and Mike Burton

Abstract. A portable analyser is described for simultaneous detection of CO2 and HF emitted by volcanoes and fumaroles. The system is based on two fibre-coupled distributed feedback lasers and only one multipass cell, and provides the absolute concentration values of the two gases, without requiring a calibration procedure, at a maximum rate of 4 Hz. The spectrometer can operate both in a closed-cell configuration and in an open-cell set-up, with the latter mitigating problems associated with chemisorption of the HF molecule. The concept, practical realization and laboratory performance of the device are presented, together with results from a first test campaign measuring volcanic gases emitted from the crater of Vulcano, Italy. We obtained an in-field sensitivity of 320 ppb for CO2 and 20 ppb for HF at 2 s integration time.

Short summary
Assessing emissions of volcanos has a three-fold importance: providing input for climate evolution models (CO2 is one of the major constituents of emissions), quantifying pollutant emissions (HCl, HF and SO2 are released in hundreds of tons/day) and monitoring the status of the magmatic chambers. For these purposes we realized gas analysers based on spectroscopic techniques, which must be sensitive, light and resistant to the emitted gases. This paper reports on the measurement of CO2 and HF.