Each month we highlight one of our Scoping Studies, each funded through our Collaboration Building Workshops. This month we welcome a blog post from Dr Dan Peters and the team using RAL Space’s expertise in sensor development to expand our knowledge of air quality in volcanic plumes.

Volcanic hazards are varied in nature, and among these, issues relating to volcanic gas and particulates can be investigated from the perspective of air quality research.

Volcanic ash poses a threat on a range of scales, ranging from ashfall in local communities to regional risks to aviation. Volcanic gases pose a further threat to the surrounding area, stemming largely from emissions of sulphur dioxide. For example, “vog” – volcanic smog – is a recurring issue in Hawaii, formed as volcanic SO2 interacts with the surrounding atmosphere to produce sulphuric acid aerosols.

Small eruptions of the kind common at volcanoes such as Stromboli (Italy) and Kilauea (Hawaii) produce plumes reaching up to hundreds of metres in the atmosphere, which drift in the direction of the prevailing wind (Figure 1). Whilst plume dispersion models can predict the direction of travel of plumes, local measurements are needed to constrain the volume of pollutants present and verify the predictions of models.

Figure 1. Plumes of gas and ash during an eruption of Stromboli in September 2019. Image: Jean-François Smekens

Although many active volcanoes have established monitoring networks, a network of ground-based sensors is unlikely to be sufficiently dense to fully monitor the development of a moving plume; and monitoring networks may not be present at all around newly active volcanoes. Additionally, it is desirable to be able to measure pollutants at altitude within the plume and along its dispersal axis, as these may later affect communities further downwind.

To address these challenges Jean-François Smekens [1] joined the SAQN Collaboration Building Workshop, where the consortium expertise in volcanology, UAVs, aerosol and gas sampling were brought together. The consortium are aiming to develop a new instrument for monitoring particulates and sulphur dioxide in volcanic plumes, as well as carbon dioxide, another important measurement in volcanological studies. Our aim is to build an instrument utilising commercial off the shelf components suitable for mounting on a small Unmanned Aerial Vehicle (UAV). We will utilise the STFC RAL Space UAV facility [2], expertise in payload design and operation [3], and STFC’s expertise in aerosol and gas handling [4]. The instrumented UAV will be available to other researchers via STFC for air quality studies.

Whilst a number of published studies have been conducted using UAVs to monitor volcanic emissions, a remaining challenge is to combine unbiased sampling of particulates with simultaneous measurements of gas concentrations. Such co-located measurements are necessary to understand the interactions between gas and particles during transport, and to more accurately model the dispersal of both. To support this aim, our instrument is designed to be mounted on a fixed-wing UAV, which not only enables longer range than multirotor UAVs but also permits a relatively stable airflow across the airfoil. Using modelling and simulations capabilities from the Computational Engineering Group in the Scientific Computing Department [5] at STFC, we aim to configure an instrument for isokinetic sampling to enable us to simultaneously carry out gas measurements and unbiased sampling of particulates.

[1] https://www.earth.ox.ac.uk/people/jean-francois-smekens, http://www.jfsmekens.com/about/

[2] https://www.ralspace.stfc.ac.uk/Pages/Autonomous-Systems-Facilities.aspx

[3] https://www.lboro.ac.uk/departments/aae/staff/cunjia-liu/

[4] https://www.ukspacefacilities.stfc.ac.uk/Pages/RAL-Space-Molecular-Spectroscopy-Facility.aspx

[5] https://www.scd.stfc.ac.uk/Pages/Computational-Engineering.aspx