Mercury gas emissions from La Soufriere Volcano, Guadeloupe Island (Lesser Antilles)

Quantifying mercury (Hg) emissions from active volcanoes is of particular interest for better constraining the global cycle and environmental impact of this highly toxic element. Here we report on the abundance of total gaseous (TGM = Hg-(g)(0) + Hg-(g)(II)) and particulate (Hg-(p)) mercury in the summit gas emissions of La Soufriere andesitic volcano (Guadeloupe island, Lesser Antilles), where enhanced degassing of mixed hydrothermal-magmatic volatiles has been occurring since 1992 from the Southern summit crater. We demonstrate that Hg in volcanic plume occurs predominantly as gaseous mercury, with a mean TGM/Hg(p) mass ratio of similar to 63. Combining the mean TGM/H2S mass ratio of the volcanic plume (similar to 3.2x10(-6)), measured close to the source vent, with the H2S plume flux (similar to 0.7 t d(-1)), determined simultaneously, allows us to estimate a gaseous mercury emission rate of 0.8 kg yr(-1) from La Soufriere summit dome. Somewhat lower TGM/S-tot mass ratio in fumarolic gases from the source vent (4.4 x 10(-7)) suggests that plume chemical composition is not well represented by the emission source (fumaroles) due to chemical processes prior to (or upon) discharge. Current mercury emission from La Soufriere volcano represents a very small contribution to the estimated global volcanic budget for this element. (C) 2009 Elsevier B.V. All rights reserved.