Full scale evaluation of atmospheric mercury budget from persistent volcanic degassing

Abstract

In the recent years, there has been an increase in environmental concerns related to the pollution of many trace metals emitted from volcanic degassing because of their toxicity and long residence times in the earth’s ecosystems. Among volcanogenic trace elements, mercury (Hg) is one of the most environmentally-significant in light of its potential harmful effects on biological systems. At present, however, the global Hg flux from volcanic sources is still poorly known. We report on Hg levels in volcanic plumes and fumaroles that, in combination with sulphur analyses and SO2 flux data, lead to global Hg estimates. We found that mercury transport in the plume is mainly in the gas-phase, as Hg0(g). Our data show that current Hg emissions from close-conduit volcanoes in a solfatara stage of activity, represent a trivial contribution to the global atmospheric Hg budget: their estimated Hg flux is considerably lower than that measured from open conduit active basaltic volcanoes which, instead, account for about 10-30% of the global yearly total Hg emissions from passive degassing volcanoes at global scale (~75 t y-1). The work also synthesizes the literature on volcanic Hg fluxes and compares different volcanoes in terms of their gaseous Hg/Stot mass ratios