Radionuclides and sulfur content in Mount Etna plume in 1983–1995: new constraints on the magma feeding system

International audienc

Volcanic emission of radionuclides and magma dynamics

International audienc

Long-lived radon decay products in Mount St. Helens emissions: An estimation of the magma reservoir volume

International audienc

Fractionation of metals in volcanic emissions

International audienc

Origin of fumarolic fluids emitted from a nonerupting volcano: Radionuclide constraints at Vulcano (Aeolian Islands, Italy)

International audienc

Relationship Between Gases and Volcanic Activity of Mount Etna in 1986

International audienceThe long-lived 222Rn decay products 210pb, 210Bi and 210po have been monitored in the plumes of several vents at Mount Etna (Sicily) from May to October 1986. The results show that the four main craters of this volcano emit gases whose compositions are different from each other. The 210Bi/210pb ratios for the plumes have similar mean values, (close to 25), which correspond to a degassing time of 1.5 to 2.7 days, according to the model of Lambert et al. (1985/86). In contrast, 210po/210pb ratios have very different mean values in each plume: 35 at the Voragine crater, 20 ax the Bocca Nuova crater, and 14 at the South East crater. These figures enable us to calculate proportions of deep magma of 50%, 29% and 19% in the degassing cells of these craters respectively. Moreover, the SE crater appears to be a secondary degassing vent• not directly related to the main magma reservoir. The evolution of these ratios has been related to variations in volcanic activity

Origins of 210Po in the atmosphere at lamto, ivory coast: Biomass burning and saharan dusts

International audienc

Methane, carbon monoxide and light non-methane hydrocarbon emissions from African savanna burnings during the FOS/DECAFE experiment

Atmospheric samples from savanna burnings were collected in the Ivory Coast during two campaigns in January 1989 and January 1991. About 30 nonmethane hydrocarbons from C2 to C6, carbon monoxide, carbon dioxide and methane were measured from the background and also at various distances from the burning. Concentrations in the fire plume reached ppmv levels for C2-C4 hydrocarbons, and 5300, 500 and 93 ppmv for CO2, CO and CH4 respectively. The excess in the mixing ratios of these gases above their background level is used to derive emission factors relative to CO and CO2. For the samples collected immediately in the fire plume, a differentiation between high and low combustion efficiency conditions is made by considering the CO/CO2 ratio. Ethene (C2H4), acetylene (C2H2), ethane (C2H6) and propene (C3H6) are the major NMHC produced in the flaming stage, whereas a different pattern with an increasing contribution of alkanes is observed in samples typical of post flaming processes. A strong correlation between methane and carbon monoxide suggests that these compounds are produced during the same stage of the combustion. In samples collected at a distance from the fire and integrated over a period of 30 minutes, the composition is very similar to that of flaming. NMHC/CO2 is of the order of 0.7%, CH4/CO2 of the order of 0.4% and CO/CO2 of the order of 6.3%. From this study, a global production by African savanna fires is derived: 65 Tg of CO-C, 4.2 Tg of CH4-C and 6.7 Tg of NMHC-C. Whereas acetylene can be used as a conservative tracer of the fire plumes, only ethene, propene and butenes can be considered in terms of their direct photochemical impact

Radioactive isotopes and trace elements in gaseous emissions from White Island, New Zealand

International audienc