Mercury emissions and stable isotopic compositions at Vulcano Island (Italy)

Sampling and analyses methods for determining the stable isotopic compositions of Hg in an active volcanic system were tested and optimized at the volcanic complex of Vulcano (Aeolian Islands, Italy). Condensed gaseous fumarole Hg-(fum)(T), plume gaseous elemental He-(g)(0) and plume particulate Hg-(p)(II) were obtained at fumaroles F0, F5, F11, and FA. The average total Hg emissions, based on Hg-T/SO2 in condensed fumarolic gases and plumes, range from 2.5 to 10.1 kg y(-1), in agreement with published values [Ferrara, R., Mazzolai, B., Lanzillotta, E., Nucaro, E., Pirrone, N., 2000. Volcanoes as emission sources of atmospheric mercury in the Mediterranean Basin. Sci. Total Environ. 259(1-3),115-121; Aiuppa, A.. Bagnato. E.. Witt, M.L.I., Mather. T.A., Parello, F., Pyle, D.M., Martin, R.S., 2007. Real-time simultaneous detection of volcanic Hg and SO2 at La Fossa Crater, Vulcano (Aeolian Islands, Sicily). Geophys. Res. Lett. 34(L21307).]. Plume Hg(p)(II) increases with distance from the fumarole vent, at the expense of Hg-(g)(0) and indicates significant in-plume oxidation and condensation of fumarole Hg-(fum)(T). Relative to the NIST SRM 3133 Hg standard, the stable isotopic compositions of Hg are delta Hg-202((fum))T =-0.74 parts per thousand +/- 0.18 (2SD, n=4) for condensed gaseous fumarole Hg-(fum)(T). delta Hg-202((g))0 =-1.74 parts per thousand +/- 0.36 (2SD, n=1) for plume gaseous elemental Hg-(g)(0) at the F0 fumarole, and delta Hg-202((p))II=-0.11 parts per thousand +/- 0.18 (2SD, n=4) for plume particulate Hg-(p)(II). The enrichment of Hg-(p)(II) in the heavy isotopes and He(,) in the light isotopes relative to the total condensed fumarolic Hg((fum))(T)gas complements the speciation data and demonstrates a gas-particle fractionation occurring after the gas expulsion in ambient T degrees atmosphere. A first order Rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor alpha(cond-gas) of 1.00135 +/- 0.00058. (C) 2008 Elsevier B.V. All rights reserved.