2-dimensional mapping of sulfur dioxide and bromine oxide at the sakurajima volcano with a ground based scanning imaging spectrograph system

A scanning imaging spectrograph system was used in this study to retrieve readings of the 2-D distribution of SO₂ and BrO around the crater of the Sakurajima volcano in Japan. The measurement was carried out during the daytime on November 2, 2005. Measurements were made at the surface of the site, located 5 km from the Sakurajima crater. One hundred horizontal scans were performed. Each column scanned by the system consists of 64 vertical pixels in order to retrieve the spatial distributions of BrO and SO₂ in the plume in terms of slant column densities (SCDs). Measured spectra were analyzed to identify and quantify SO₂ and BrO in the volcanic plume utilizing the plume's specific absorption features in the ultra violet region. Two-dimensional BrO and SO₂ distributions in SCD were retrieved horizontally covering the upwind, crater and downwind areas, and vertically, including the plume in the center of the scanned image. Both horizontal and vertical dispersions of SO₂ SCD from the crater were successfully measured to be from 10¹⁷ to 4.5 × 10¹⁸ molecules cm^-2. However, BrO was measured below 10¹⁵ molecules cm^-2, which is considered its background level.