Characterising downwind particulate and sulfur dioxide air pollution from volcanic emissions

One of the hazards of volcanic eruptions is the emission of gas and aerosol into the atmosphere, which can cause damage to the environment and human health as well as impacting climate. Emissions from effusive volcanic eruptions and passively degassing volcanoes typically remain in the troposphere where they are advected by the wind and can cause deterioration to air quality across a downwind region. Of the emitted gases, sulfur dioxide (SO2) is often highly concentrated with respect to the background atmosphere and has important air quality and environmental consequences. Over time after emission from the volcanic source, SO2 may be converted to sulfate aerosols through atmospheric processes, leading to additional air quality concerns with an increase in fine particulate matter (PM). This thesis aims to characterise the SO2 and PM air quality in regions downwind of tropospheric volcanic emissions. Three study sites are examined; Kılauea volcano on the Island of Hawai‘i, Masaya volcano in Nicaragua and Fagradalsfjall volcano in Iceland. The SO2 and PM concentrations in the downwind regions are monitored using highly accurate reference-grade air quality instruments, and a variety of lower-cost miniaturised sensors. Low-cost sensors are increasingly used for air quality measurements, and in this thesis I investigate their effectiveness for monitoring in volcanic environments. Low-cost sensors are used at Masaya volcano as a first-attempt to establish an air quality monitoring network. At Kılauea volcano, a long time-series of SO2 and PM data is examined to determine air quality deterioration during a period of extremely heightened volcanic activity. At Fagradalsfjall volcano, the impact of a small eruption in proximity to densely-populated areas is examined and the population exposure to volcanic SO2 is estimated using a plume dispersion model. These studies increase the knowledge of SO2 and aerosol dispersal from volcanic sources, especially for those communities in the affected areas