Strengths & Weaknesses

  • There is a broad need of closer research connections between volcanologists and atmospheric scientists to accurately assess the origin, transport and impacts of volcanic plumes. As highlighted by recent Icelandic eruptions (e.g. Eyjafjallajokull 2010) limited knowledge of gas-particle emissions at the source (compositions, mass flows, load and size of particles, etc) make it difficult to interpret measurements of the downwind plume, or correctly initialize models of plume dispersion and atmospheric impacts.

  • Challenges to characterize volcanic emissions and near-source plume processing include the harsh acidic conditions and their remote and poorly accessible location. The atmospheric community has developed sophisticated ground-based instruments for atmospheric measurements but these are often high-power and heavy so cannot so easily be used near-to-source. The volcanology community, instead, has developed/applied dedicated instruments for both remote sensing (FTIR, UV) and in-situ measurements of volcanic gas-particle emissions (see details below). However, some instrumental limits or/and uncertainties in interpreting processes still have to be overcome. Interactions and exchange of expertise between volcanologists and atmospheric scientists offer an opportunity to further improve existing methods and develop new approaches to better characterize the “effective emission source”.

  • Regarding observations there is a need for

    • (i) longer-term installed instruments as part of eruption monitoring,

    • (ii) techniques that can be rapidly and repeatedly deployed to complete the observation suite and/or in case of an eruption, and

    • (iii) planned coordinated field-campaigns that focus in more detail on aspects of plume process or instrument development. All three approaches are currently used but can be further developed with common objectives.

  • At Piton de la Fournaise volcano (La Réunion, Indian Ocean) – one of the project’s targets – different instruments have been either installed for permanent monitoring (e.g. DOAS, Multi-GaS) or deployed during eruptions (OP-FTIR, filter-packs), following previous testing on mid-latitude volcanoes (e.g. Mt Etna). However, further development to properly deploy/analyse under tropical conditions is needed due to both issues related to instrument deployment/operations and for the different atmospheric processes under these contrasting atmospheric conditions.

  • To date, modeling of the high-temperature chemistry of volcanic gases emissions at the source mostly relied on thermodynamic models and equilibrium assumptions. Clearly, these models cannot fully represent near-source processes upon entering the atmosphere, where chemical processes may be kinetics-limited and involve fast oxidation or heterogeneous gas-particle reactions in the air-dominated medium. Up to now few laboratory experiments exist on these near-source reactions in volcanic plumes, while these could bring important new insights.

  • The approach described in the following paragraphs is best suited to characterize and model the convective regime. However, secondary sources (lavas, pyroclastic currents and their interaction with volatile sources like surface water, sea water and vegetation) can represent a major and still poorly constrained source of mass, energy and momentum (e.g. Di Muro et al., 2004; Durand et al., 2014). Future researches should permit better to take into account their contribution.

  • Building reliable inventories of gases and aerosols emissions from volcanoes, including both passive emissions and eruptions, from the local scale in the vicinity of volcanoes to the regional and global scales spanning up to several decades is still challenging. Such inventories are needed as inputs for impact studies on atmospheric composition and climate. To date, there is a global inventory for SO2 emissions (e.g. Diehl, 2009; Fioletov et al., 2016; McLinden et al., 2016) available for the atmospheric community but there is room for improvements (in the field/satellite/model approaches used, spatial and temporal coverage, extrapolation to estimate global emissions). Also there is a need to extend to other gases (e.g. halogens) and to aerosols.