Black Carbon aerosols in Mediterranean urban areas

Urban areas represent a hot spots for the so called triple planetary crisis: climate change, air pollution, and biodiversity loss. The anthropogenically-emitted light absorbing aerosols, and in particular the Black Carbon (BC), play a crucial role in all the aspects of this planetary crisis. The very delicate and populated urban areas of the Mediterranean region make no exception.

This study aims at enhancing the understanding on the BC light absorbing aerosols properties in urban areas in the Mediterranean. In-situ observations have been continuously carried out in Rome downtown, at an urban background location, since 2020, by an Aethalometer at 7 wavelengths (from 370 to 950 nm). These were coupled to ancillary measurements (Elemental Carbon and micrometeorology).

We assessed the site-specific Mass Absorption Coefficient (MAC) and show evidence of its strong temporal variability in the urban area of Rome. Based on this, we provide a more accurate estimate of the BC mass concentration. We then explore MAC dependance on the absorption Ångström exponents (AAE), with a specific focus on the contribution from fossil fuels air pollution. Finally, we assess associations between BC light absorption, the urban radiative balance, and the Urban Heat Island (UHI) effect.

Findings may support studies aimed at characterizing BC in urban areas and developing new health-related air quality metrics, as well as at improving climate and air quality models estimates at urban scale in the Mediterranean. Findings may further serve at improving satellite-based observations of the light absorbing aerosols in urban areas, which are strongly needed in the future to improve BC spatial coverage at a planetary scale.

Acknowledgments: Project funded by both ARPA Lazio, and the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4 - Call for tender No. 3138 of 16 December 2021, rectified by Decree n.3175 of 18 December 2021 of Italian Ministry of University and Research funded by the European Union – NextGenerationEU; Award Number: Project code CN_00000033, Concession Decree No. 1034 of 17 June 2022 adopted by the Italian Ministry of University and Research, CUP F13C22000720007, Project title “National Biodiversity Future Center - NBFC”.