Abstract
We present here a new estimated of volcanic CO2 flux from Japanese volcanoes as an example of regional CO2 flux estimate from subduction zones. We can estimate the volcanic CO2 flux by comparing the volcanic gas composition data and regional SO2 flux. The CO2/SO2 mole ratios of the gases emitted from these persistent degassing volcanoes range from 0.4 to 2 with an average of 1.1, and the CO2 flux from Japan arcs is estimated as 4500 ton/d (or 37 Tmol/y). The CO2/SO2 mole ratio of 1.1 is much smaller than previous estimated of 2.2-6.5 obtained for Japan arcs and also smaller than the estimates for global subduction emission. The present estimate is obtained directly from the measured compositions of the major sources; therefore is believed to be more reliable. Since the present estimate is just for Japanese volcanoes and does not necessarily represent composition from other subduction zones for which we need further studies.
