A High-resolution Simulation of the Transport of Gazeous Pollutants from a Severe Effusive Volcanic Eruption

Abstract:

The Reunion Island experienced its biggest eruption of Piton de la Fournaise volcano during April 2007. Known as “the eruption of the century”, this event degassed more than 230 KT of SO₂. Theses emissions led to important health issues, accompanied by environmental and infrastructure degradations. We want to show a modeling study uses the mesoscale chemical model MesoNH to simulate the transport of gazeous SO₂ between April 2nd and 7th, with a focus on the influence of heat fluxes from lava. Three domains are nested from 2km to 100m horizontal spacing grid, allow us to better represent the phenomenology of its eruption.
This modelling study have coupled on-line (i) the MesoNH mesoscale dynamics, (ii) a gas and aqueous chemical scheme, and (iii) a surface scheme that integrates a new sheme for the lava heat flux and its surface propagation. Thus, all flows (heat sensible and latent, vapor, SO₂, CO₂, CO) are triggered depending on its dynamic. Our simulations reproduce quite faithfully the surface field observation of SO₂. Various sensitivity analyzes exhibit that volcano sulfur distribution was mainly controlled by the lava heat flow.
Without heat flow parameterization, the surface concentrations are multiplied by a factor 30 compared to the reference simulation.Numerical modeling allows us to distinguish acid rain produced by the emission of water vapor and chloride when the lava flows into the seawater of those formed by the mixing of the volcanic SO₂ into the raindrops of convective clouds.