Work

Source apportionment of processes contributing to volcanic PM10 aerosols during the 2021 eruption of Tajogaite

Year: 2025

Type: article

Abstract: The 2021-eruption of Tajogaite (La Palma, Canary Islands) was associated with the formation of large amounts of respirable PM 10 aerosols (smaller than 10 μm) that triggered air quality crisis and lockdowns for ∼35,000 persons. This study aims to quantify the contribution of the aerosol formation mechanisms to the volcanic PM 10 concentrations. During the eruption and post-eruption, we monitored trace gases (SO 2 , HF, HCl and NO 2 ), and the size distribution and chemical composition of falling-tephra and PM 10 aerosols. We also applied a stoichiometric apportionment methodology to investigate the atmospheric chemistry involved in the formation of secondary aerosols. During tephra-fallouts, giant particles (mm-to-cm size) settled rapidly, while gas-phase species condensed onto smaller particles. This resulted in the formation of (i) primary volcanic aerosols composed of micron-sized quenched lava fragments (volcanic-glass and rock-forming minerals) with low compositional variability in Si (18 wt%), Al (6.7 %), Fe (6.75 %), Ca (6 %), Na (4 %) and Mg (3 %), and (ii) secondary aerosols (gas-phase condensation/reaction) associated with sulphate, chloride and fluoride volcanic salts. These include Na 2 SO 4 (33 % of total SO 4 2− ), NH 4 HSO 4 (16 %), K 2 SO 4 (11 %), MgSO 4 (6 %), (NH 4 ) 2 SO 4 (2.2 %), and 30 % as excess SO 4 = relative to measured cations. Na 2 SO 4 and MgSO 4 were formed via quick interactions between SO 2 and volcanic-glass in the eruption plume, while NH 4 HSO 4 and excess sulphate persisted during post-eruption degassing. Cl − occurred predominantly as NaCl (98 %), and F − as CaF 2 (94 %). Lava flows enhanced ammonia emissions from agricultural-soils; as result, 87 % of nitrate was present as NH 4 NO 3 , stabilized by the NH 4 + –NO 3 − chemical bond under the high humidity linked to volcanic water emissions. Primary and secondary aerosols accounted for 61 % and 26 % of PM 10 as average during the eruption, respectively. These results highlight the importance of atmospheric chemistry after the fresh volcanic emissions, that may even result in the interactions between volcanic and non-volcanic species.

Source: The Science of The Total Environment

DOI: 10.1016/j.scitotenv.2025.180321