The annual volcanic gas input into the atmosphere, in particular into the stratosphere: a global data set for the past 100 years

We compiled a global data set of volcanic degassing during both explosive and quiescent volcanic events. The data set comprises estimates of gas emissions of volcanoes from Europe (e.g. Etna), Asia (e.g. Merapi), the Americas (e.g. Fuego), Africa (e.g. Erta Ale) and ocean islands (e.g. Kilauea) over the past 100 yr. The set includes 50 monitored volcanoes and similar to310 extrapolated explosively erupting volcanoes. Among the similar to360 volcanoes, 75% are located in the Northern and 25% in the Southern Hemisphere. We have estimated the total annual global volcanic sulfur emission into the atmosphere to be on the order of 7.5-10.5 X 10(12) g/yr S (here as SO2), amounting to 10-15% of the annual anthropogenic sulfur output (similar to70 X 10(12) g/yr S during the decade 1981-1990) and 7.5-10.5% of the total global sulfur emission (e.g. biomass burning, anthropogenic, dimethylsulfide) with similar to 100 X 10(12) g/yr S. The estimates of other volcanic gases emitted (e.g. H2S, HCl) are based on the assumption that the different gas components emitted by a volcano are in equilibrium with each other. Accordingly, the molar ratios of the gas species in high-temperature fumaroles are similar to molar ratios equilibrated at depth where the gas separates from the magma. Thus, we can use the directly measured SO2 fluxes and known molar ratios (e.g. H2S/SO2) for a semi-quantitative estimate of other gas components emitted (e.g. H2S). The total annual emission of HCl is 1.2-170X10(12) g/yr, that of H2S 1.5-37.1 X 10(12) g/yr, of HF 0.7-8.6 x 10(12) g/yr, of HBr 2.6-43.2 x 10(9) g/yr, and of OCS 9.4 X 10(7)-3.2 X 10(11) g/yr. We estimate an emission of 1.3 X 10(7)-4.4 x 10(11) g/yr for CS2. (C) 2002 Elsevier Science B.V. All rights reserved.