Mercury emissions in volcanic gases from Mt. Etna, Italy.

Reykjavík, Iceland

Ministry for Foreign Affairs, Iceland
Samorka – Icelandic Energy and Utilities
University of Iceland
The Icelandic Institute of Natural History
Icelandic Road Administration
Icelandic Meteorological Office
Iceland GeoSurvey
Viðlagatrygging Íslands
Soil Conservation Service of Iceland
Ministry for the Environment
Ministry of Education, Science and Culture

Mercury is a global pollutant that can be found in different forms and different ecosystems. Special attention has
recently been devoted to mercury due to its high chemical reactivity, its global spreading, its biogeochemical cycling,
its transformations in the environment, its ability for biomagnification and its high toxicity. Beside anthropogenic
sources, mercury can also be of natural origin. Among natural Hg sources, volcanoes can be important. Volcanic
gas emissions may be rich in elemental gaseous mercury (Hg0), reactive gaseous mercury (HgII) and other mercury
forms. Mt. Etna (Sicily, Italy) is one of the most active volcanoes in the world and one of the largest contributors of
magmatic volatiles to the environment; consequently, we tried to estimate its contribution to regional and global Hg
budgets and tested the eligibility of Hg as a tool for volcano monitoring. Mercury concentrations have been
measured on Mt. Etna during several campaigns carried out between 2004 and 2007 in fumaroles, mofettes and
diffuse degassing areas, as well as in the air inside and across the volcanic plume. In addition, Hg fluxes have been
measured by flux chamber technique. Mercury concentrations measured in air below the volcanic plume in
November 2004 ranged between 4 and 30 ng m-3 at low altitude, and between 65 and 132 ng m-3 close to the
summit craters. A profile of Hg in the air below the volcanic plume carried out on helicopter on November 2006
showed Hg concentrations up to 60 ng m-3. Hg contents in fumarole gases reached 64,200 ng m-3, and soil gas Hg
showed temporal variations that reached the highest values (up to 240 ng m-3) in fall 2005. The highest Hg fluxes
were measured in bubbling gas from mud volcanoes at the SW foot of Etna, reaching 1300 ng m-2 h-1. Mercury
contents were found highly correlated both with water/mud temperature at mud volcanoes and with concurrent soil
CO2 effluxes. In the latter case, hydrothermal gases showed higher values and a higher correlation than
“cold”gases. Our results, therefore, look promising for the use of mercury in geochemical monitoring of volcanic
activity.