Halogenated trace compounds in fumarolic gases of the Nicaraguan subduction zone volcanoes: variation patterns, budgets and impact on the Earth's atmosphere
Halogenated compounds are important constituents of the Earth's atmosphere, because they may have strong influence on its physical and chemical properties. The most abundant halogenated hydrocarbons in volcanic gas samples from fumaroles of the quiescently degassing Nicaraguan subduction zone volcanoes Momotombo, Cerro Negro and Mombacho, collected during four field campaigns between July 2001 and July 2003, were CH3Cl, CH3Br, CH3I, CH2Cl2, CHCl3, CCl4, C2H5Cl, C2H5Br, C2H5I and C2H3Cl. The variability in concentrations at different time-scales (minutes to years) is less than two orders of magnitude for the single volcanoes. Estimations of gas fluxes at Momotombo indicate that the contribution of quiescently degassing volcanoes to the global halo(hydro)carbon inventory is very low. Assuming that the investigated volcanoes are representative, the question of a significant volcanic contribution of stable halogenated compounds (CFCs, HFCs, HCFCs, Halons, CF4, NF3 and SF6) to the atmospheric budget can be negated. Furthermore a new sampling setup for fumarolic trace gases is presented.
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