Characterization of atmospheric aerosol and its carbonaceous components at a central Mediterranean site: A multi-method approach using optical, physical, and isotopic techniques

Abstract

A new analytical approach combining aethalometer measurements, organic and elemental carbon (OC/EC) analysis, Scanning Electron Microscopy (SEM), Particle Induced X-ray Emission (PIXE), and Isotope Ratio Mass Spectrometry (IRMS) was used to characterize aerosol properties and its carbonaceous component in Lecce (Italy), located in the Central Mediterranean, during a monitoring campaign between May and June 2024. Both anthropogenic activities (e.g., vehicular traffic, industrial emissions) and natural events (e.g., wildfires, desert dust transport) were responsible for the high temporal variability of optical, physical, and chemical properties of atmospheric aerosol at the study site. In more detail, the measured Absorption Ångström Exponent (AAE) mean values (in the range 1.0–1.5) indicated a mixture of black carbon and organic or biogenic particles. Correlation analyses between aerosol absorption coefficients and PM mass concentrations highlighted a stronger relationship with EC compared to OC, highlighting the role of EC in the absorption properties of atmospheric aerosols. Chemical characterization through SEM and PIXE identified three aerosol source clusters: anthropogenic (high C concentrations, markers of combustion sources and industrial emissions), desert dust (crustal elements), and marine spray (Na and Cl). IRMS isotopic analysis further confirmed the distinction between anthropogenic and natural aerosol sources, with overlaps observed for marine aerosols influenced by both natural and anthropogenic activities. This work underlines the importance of multi-method procedures in understanding aerosol composition and dynamics, with potential associations for air quality monitoring, climate modeling, and health risk assessments.