@article{ref1,
title="Validation of a novel Multi-Gas sensor for volcanic HCl alongside H<sub>2</sub>S and SO<sub>2</sub> at Mt. Etna",
journal="Bulletin of volcanology",
year="2017",
author="Roberts, T. J. and Lurton, T. and Giudice, G. and Liuzzo, M. and Aiuppa, A. and Coltelli, M. and Vignelles, D. and Salerno, G. and Couté, B. and Chartier, M. and Baron, R. and Saffell, J. R. and Scaillet, B.",
volume="79",
number="5",
pages="36-36",
abstract="Volcanic gas emission measurements inform predictions of hazard and atmospheric impacts. For these measurements, Multi-Gas sensors provide low-cost in situ monitoring of gas composition but to date have lacked the ability to detect halogens. Here, two Multi-Gas instruments characterized passive outgassing emissions from Mt. Etna's (Italy) three summit craters, Voragine (VOR), North-east Crater (NEC) and Bocca Nuova (BN) on 2 October 2013. Signal processing (Sensor Response Model, SRM) approaches are used to analyse H<sub>2</sub>S/SO<sub>2</sub> and HCl/SO<sub>2</sub> ratios. A new ability to monitor volcanic HCl using miniature electrochemical sensors is here demonstrated. A &quot;direct-exposure&quot; Multi-Gas instrument contained SO<sub>2</sub>, H<sub>2</sub>S and HCl sensors, whose sensitivities, cross-sensitivities and response times were characterized by laboratory calibration. SRM analysis of the field data yields H<sub>2</sub>S/SO<sub>2</sub> and HCl/SO<sub>2</sub> molar ratios, finding H<sub>2</sub>S/SO<sub>2</sub> = 0.02 (0.01-0.03), with distinct HCl/SO<sub>2</sub> for the VOR, NEC and BN crater emissions of 0.41 (0.38-0.43), 0.58 (0.54-0.60) and 0.20 (0.17-0.33). A second Multi-Gas instrument provided CO<sub>2</sub>/SO<sub>2</sub> and H<sub>2</sub>O/SO<sub>2</sub> and enabled cross-comparison of SO<sub>2</sub>. The Multi-Gas-measured SO<sub>2</sub>-HCl-H<sub>2</sub>S-CO<sub>2</sub>-H<sub>2</sub>O compositions provide insights into volcanic outgassing. H<sub>2</sub>S/SO<sub>2</sub> ratios indicate gas equilibration at slightly below magmatic temperatures, assuming that the magmatic redox state is preserved. Low SO<sub>2</sub>/HCl alongside low CO<sub>2</sub>/SO<sub>2</sub> indicates a partially outgassed magma source. We highlight the potential for low-cost HCl sensing of H<sub>2</sub>S-poor HCl-rich volcanic emissions elsewhere. Further tests are needed for H<sub>2</sub>S-rich plumes and for long-term monitoring. Our study brings two new advances to volcano hazard monitoring: real-time in situ measurement of HCl and improved Multi-Gas SRM measurements of gas ratios.<br><br>© The Author(s) 2017.<p /> <p>Language: en</p>",
language="en",
issn="0258-8900",
doi="10.1007/s00445-017-1114-z",
url="http://dx.doi.org/10.1007/s00445-017-1114-z"
}