Mass spectrometry for in-situ volcanic gas monitoring

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The principle behind volcanic gas monitoring is that changes in the rate and the composition of the gaseous emissions are associated with major subsurface movement of magma. There has been increased attention directed towards measurements of volcanic gaseous emissions in order to gain a better comprehension of the precursor signals of eruptive activity. There is also a new appreciation of the hazards that gaseous emissions from volcanic sites pose to their immediate surrounding as well as their effects on the atmosphere and global climate. In-situ mass-spectrometer measurements of volcanic gaseous emissions were conducted at several fumarolic sites using a commercial quadrupole mass spectrometer (QMS-300, from SRS Inc) and demonstrated the usefulness of this analytical technique for real-time continuous volcanic gas monitoring applications. The gas concentrations obtained by the MS were in agreement with the values obtained using gas chromatography (GC) at the Hawaiian Volcano Observatory. In addition, the C/S ratios measured by the MS, using both traditional bottle sampling and in-situ sampling, were found to be very similar. Other gases, such as helium, which it is not possible to monitor with any other continuous technique currently available to volcanologists, were easily detected by the mass spectrometer. The field measurements also provided instrument-performance parameters for an ideal field-deployable mass spectrometer. This is the first of a series of articles aiming at the development of a network of mass spectrometers connected via the Internet for real-time, continuous volcanic gaseous emissions monitoring.