Real-time simultaneous detection of volcanic Hg and SO2 at La Fossa Crater, Vulcano (Aeolian Islands, Sicily)

Measuring Hg/SO₂ ratios in volcanic emissions is essential for better apportioning the volcanic contribution to the global Hg atmospheric cycle. Here, we report the first real-time simultaneous measurement of Hg and SO₂ in a volcanic plume, based on Lumex and MultiGAS techniques, respectively. We demonstrate that the use of these novel techniques allows the measurements of Hg/SO₂ ratios with a far better time resolution than possible with more conventional methods. The Hg/SO₂ ratio in the plume of F0 fumarole on La Fossa Crater, Vulcano Island spanned an order of magnitude over a 30 minute monitoring period, but was on average in qualitative agreement with the Hg/SO₂ ratio directly measured in the fumarole (mean plume and fumarole ratios being 1.09 × 10^-6 and 2.9 × 10^-6, respectively). The factor 2 difference between plume and fumarole compositions provides evidence for fast Hg chemical processing the plume.