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Article

Assessment of the COVID-19 Lockdown Effects on Spectral Aerosol Scattering and Absorption Properties in Athens, Greece

1
Institute for Environmental Research and Sustainable Development, National Observatory of Athens, 15236 Athens, Greece
2
Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, 70013 Heraklion, Greece
3
Aryabhatta Research Institute of Observational Sciences, Nainital 263001, India
*
Authors to whom correspondence should be addressed.
Academic Editor: Gunnar W. Schade
Atmosphere 2021, 12(2), 231; https://doi.org/10.3390/atmos12020231
Received: 3 January 2021 / Revised: 31 January 2021 / Accepted: 3 February 2021 / Published: 8 February 2021
(This article belongs to the Special Issue Coronavirus Pandemic Shutdown Effects on Urban Air Quality)
COVID-19 is evolving into one of the worst pandemics in recent history, claiming a death toll of over 1.5 million as of December 2020. In an attempt to limit the expansion of the pandemic in its initial phase, nearly all countries imposed restriction measures, which resulted in an unprecedented reduction of air pollution. This study aims to assess the impact of the lockdown effects due to COVID-19 on in situ measured aerosol properties, namely spectral-scattering (bsca) and absorption (babs) coefficients, black carbon (BC) concentrations, single-scattering albedo (SSA), scattering and absorption Ångström exponents (SAE, AAE) in Athens, Greece. Moreover, a comparison is performed with the regional background site of Finokalia, Crete, for a better assessment of the urban impact on observed differences. The study examines pre-lockdown (1–22 March 2020), lockdown (23 March–3 May 2020) and post-lockdown (4–31 May 2020) periods, while the aerosol properties are also compared with a 3–4 year preceding period (2016/2017–2019). Comparison of meteorological parameters in Athens, between the lockdown period and respective days in previous years, showed only marginal variation, which is not deemed sufficient in order to justify the notable changes in aerosol concentrations and optical properties. The largest reduction during the lockdown period was observed for babs compared to the pre-lockdown (−39%) and to the same period in previous years (−36%). This was intensified during the morning traffic hours (−60%), reflecting the large decrease in vehicular emissions. Furthermore, AAE increased during the lockdown period due to reduced emissions from fossil-fuel combustion, while a smaller (−21%) decrease was observed for bsca along with slight increases (6%) in SAE and SSA values, indicating that scattering aerosol properties were less affected by the decrease in vehicular emissions, as they are more dependent on regional sources and atmospheric processing. Nighttime BC emissions related to residential wood-burning were slightly increased during the lockdown period, with respect to previous-year means. On the contrary, aerosol and pollution changes during the lockdown period at Finokalia were low and highly sensitive to natural sources and processes. View Full-Text
Keywords: COVID-19; traffic; aerosol scattering; absorption; SSA; Greece COVID-19; traffic; aerosol scattering; absorption; SSA; Greece
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MDPI and ACS Style

Kaskaoutis, D.G.; Grivas, G.; Liakakou, E.; Kalivitis, N.; Kouvarakis, G.; Stavroulas, I.; Kalkavouras, P.; Zarmpas, P.; Dumka, U.C.; Gerasopoulos, E.; Mihalopoulos, N. Assessment of the COVID-19 Lockdown Effects on Spectral Aerosol Scattering and Absorption Properties in Athens, Greece. Atmosphere 2021, 12, 231. https://doi.org/10.3390/atmos12020231

AMA Style

Kaskaoutis DG, Grivas G, Liakakou E, Kalivitis N, Kouvarakis G, Stavroulas I, Kalkavouras P, Zarmpas P, Dumka UC, Gerasopoulos E, Mihalopoulos N. Assessment of the COVID-19 Lockdown Effects on Spectral Aerosol Scattering and Absorption Properties in Athens, Greece. Atmosphere. 2021; 12(2):231. https://doi.org/10.3390/atmos12020231

Chicago/Turabian Style

Kaskaoutis, Dimitris G., Georgios Grivas, Eleni Liakakou, Nikos Kalivitis, Giorgos Kouvarakis, Iasonas Stavroulas, Panayiotis Kalkavouras, Pavlos Zarmpas, Umesh C. Dumka, Evangelos Gerasopoulos, and Nikolaos Mihalopoulos. 2021. "Assessment of the COVID-19 Lockdown Effects on Spectral Aerosol Scattering and Absorption Properties in Athens, Greece" Atmosphere 12, no. 2: 231. https://doi.org/10.3390/atmos12020231

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