Sulfur dioxide fluxes from the volcanoes of Hokkaido, Japan

We report here the first measurements of SO2 emission rates for three volcanoes in Hokkaido. Observations were made by scattered light ultraviolet (UV) spectroscopy using miniature spectrometers carried in vehicles or on foot, or attached to scanners, with data processing following variants on differential optical absorption spectroscopy. The following mean fluxes were calculated for measurements in 2003 (and 2004): 0.032 (0.14), 0.24 (0.28) and 2.4 kg s− 1 for Meakan-dake, Tarumae, and Tokachi-dake, respectively. These are thought to be the only sites of high temperature volcanic degassing on Hokkaido at present, and thus the modest combined flux of 2.7 kg s− 1 represents, to first order, the total volcanic emission rate of SO2 for the island. This represents only a small fraction of the SO2 output of about 80 kg s− 1 for Miyakejima volcano in 2003. The apparently low sulfur emission from Hokkaido volcanoes may reflect the scrubbing efficiency of their hydrothermal systems though H2S emissions remain unquantified. The ability to measure comparatively weak fumarole emissions (e.g., at Meakan-dake and Tarumae) emphasizes the value of walking traverse UV spectroscopy.