HE-3 AND CO2 FLUXES FROM SUBAERIAL VOLCANOS ESTIMATED FROM PO-210 EMISSIONS

The volcanic flux of Po-210, a radiogenic and radioactive isotope belonging to the decay chain of U-238, has been quantified from its concentration in volcanic plumes and its mean residence time in the troposphere (Lambert et al., 1982). Measurements of He-3, CO2 and Po-210 in the high-temperature gases of a few volcanoes allow estimates of He-3 and CO2 subaerial fluxes to be made. Several factors affecting the Po-210/He-3 ratio in volcanic gases are discussed. The He-3 flux from subaerial volcanoes, (1.0 +/- 0.5) X 10(2) mol/yr, is one order of magnitude lower than the MOR flux. The volcanic flux of CO2 into the atmosphere, (2 +/- 0.5) X 10(12) mol/yr, is comparable to the carbon flux from the mantle at mid-ocean ridges. We propose that most of carbon involved in subaerial volcanism is derived from the mobilisation of carbon present at the surface of the Earth.