Extreme Saharan dust outbreak: Air quality crisis in NW Spain (March 2022)

This is the authors' abstract. We don't add key points for this paper.

The Iberian Peninsula is highly susceptible to Saharan dust intrusions, which have become increasingly frequent and intense in recent years. In March 2022, an exceptional winter dust outbreak affected north-western Spain, producing record PM 10 levels across several locations. This study characterises the chemical, optical, and morphological properties of aerosols associated with the event that impacted León (NW Spain) between 14 and 16 March 2022. A month-long sampling campaign (1 – 31 March) was conducted downtown, and PM 10 samples were analysed for water-soluble inorganic ions, trace elements, and organic and elemental carbon. Aerosol light absorption and column-integrated optical properties were also evaluated, and selected samples were examined using SEM-EDS. During the intrusion, PM 10 reached 370 μg m -3 , far exceeding the WHO 24-hour guideline. Average concentrations increased from 16 ± 7.7 μg m -3 under non-dust conditions to 89 ± 115 μg m -3 during the outbreak. Organic carbon rose markedly, reaching 11 μg m -3 compared with 2.2 ± 0.9 μg m -3 in background air. Strong enhancements in crustal elements (Si, Ca, Al, Fe, K, Mg) and major ions (SO 4 2- , Ca 2+ , NO 3 - ) were consistent with intense mineral dust transport. Aethalometer-derived iron concentrations confirmed substantial dust loading, while an increase in the Ångström Absorption Exponent indicated enhanced UV–visible absorption by dust particles. These results demonstrate severe air-quality deterioration during winter Saharan intrusions and highlight the value of integrating chemical, optical, and morphological analyses to characterise extreme dust events affecting south-western Europe.