A miniaturised ultraviolet spectrometer for remote sensing of SO 2 fluxes: a new tool for volcano surveillance

Abstract

For 30 years, the correlation spectrometer (COSPEC) has been the principal tool for remote monitoring of volcanic SO 2 fluxes. During this time, the instrument has played a prominent role in volcanic hazard assessment. COSPEC data also underpin estimates of the global volcanic SO 2 flux to the atmosphere. Though innovative for its time, COSPEC is now outdated in several respects. Here we report the first measurements with a potential replacement, using a low cost, miniature, ultraviolet fibre-optic differential optical absorption spectrometer (mini-DOAS). Field experiments were conducted at Masaya Volcano (Nicaragua) and Soufrière Hills Volcano (Montserrat). The mini-DOAS was operated from a road vehicle and helicopter, and from a fixed position on the ground, indicating fluxes of ∼4 and 1 kg s −1 at Masaya Volcano and Soufrière Hills Volcano, respectively. Side-by-side observations with a COSPEC on Montserrat indicate a comparable sensitivity but the mini-DOAS offers several advantages, including the collection of broadband ultraviolet spectra. It has immense potential for geochemical surveillance at volcanoes worldwide.