Trabalho apresentado em European Aerosol Conference - EAC2023, 3-8 setembro 2023, Málaga, EspanhaN/

Almeida, S. M.

Alves, Célia

Borges, Sónia

Canha, Nuno

Gamelas ou Carla A. Gamelas, Carla

Kertesz, Z.

Silva, Anabela

Vicente, Ana

English

Repositório Comum

  Source apportionment of PM2.5 in the pre-pandemic versus pandemic period in an area near Lisbon: Lessons for air quality management  C.A. Gamelas1,2, N. Canha1, Ana Vicente3, Anabela Silva4, Sónia Borges4, Célia Alves3, Z. Kertesz5, S.M. Almeida1 1Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Portugal  2Instituto Politécnico de Setúbal, Escola Superior de Tecnologia de Setúbal, CINEA, Portugal 3CESAM—Centre for Environmental and Marine Studies, University of Aveiro, Portugal 4Câmara Municipal do Seixal, Divisão de Desenvolvimento Estratégico, Seixal, Portugal 5Laboratory for Heritage Science, Institute for Nuclear Research, Debrecen, Hungary Keywords: Particulate matter, PIXE, SARS-CoV-2, confinement, Positive Matrix Factorisation. Associated conference topics: 2.9, 2.11, 2.8 Presenting author email: carla.gamelas@estsetubal.ips.pt; carla.gamelas@ctn.tecnico.ulisboa.pt  The lockdowns held due to the COVID-19 pandemic caused changes in air quality worldwide, allowing important lessons to be drawn on how to abate pollution (Querol et al., 2021). Seixal, a densely populated area near Lisbon, comprising heavy industry (e.g. steelworks) and highways with intense commuting traffic, has suffered from poor air quality in the last decades. The present study aims to address this problem, by identifying PM2.5 emission sources and determining their contribution. PM2.5 samples were collected in 128 days, in winter (December 2019-March 2020), summer (June-August 2020) and autumn (September-November 2020), spanning from pre-pandemic to pandemic context. The composition of PM2.5 was assessed for 24 elements (by Particle Induced X-Ray Emission, PIXE), secondary inorganic ions (by ion chromatography) and black carbon (BC, by multi-wavelength absorption). The Positive Matrix Factorization receptor model PMF 5.0 was used to perform source apportionment (Gamelas et al., 2023). The PM2.5 and PM10 mean concentrations were 1311 g.m-3 and 2413 g.m-3, respectively, bellow the annual limits of Directive 2008/50/EC, but above the WHO annual guideline values (WHO, 2021). The daily WHO guideline values for PM2.5 and for PM10, not to be exceeded more than 3-4 days per year, have been exceeded 33 and 8 times, respectively, in the 128 days. The most abundant species in PM2.5 were BC (19.9%), SO42- (15.4%), NO3- (11.6%) (with mean concentrations 1 g.m-3) and NH4+, Na, Cl, K, Ca, Si and Fe (100 ng.m-3). From the pre- to the post-confinement, there was a reduction of 46.1 % in PM2.5, and a significant reduction (p<0.050) of all the PM2.5 components, except for Al, Ba, Ca, Si and SO42-. PMF identified seven sources, whose contributions at the receptor were greatly influenced by the restrictions imposed by the COVID-19 pandemic (Figure 1). Fuel-oil combustion and vehicle exhaust factors were significantly higher in the pre- than in the post-confinement (p<0.050), with vehicle exhaust presenting the most pronounced decrease (80.1%). These results confirm the relevance of traffic and  Figure 1. Source contributions for PM2.5 mass, for the selected PMF solution.  associated secondary aerosol in PM2.5 in the study area and reveal that the decrease in the PM2.5 concentrations was due, to a large extent, to the reduction of vehicle traffic, caused by the COVID-19 confinement. On the other hand, secondary sulphate was the main contributor in post-confinement (Figure 1), due to increased photochemical activity in summer; followed by industry, since the steelworks did not stop to operate during the confinement and due to increased resuspension in the dry season. Besides the restrictions imposed by COVID-19 and the seasonality, the source contributions at the receptor were also affected by the types of air mass trajectories.  In conclusion, the pandemic confinement created a unique opportunity for assessing the effect of anthropogenic activities on air pollutants in the study area and targeted mitigation measures to improve air quality are presented based on this assessment.  FCT/MCTES is acknowledged for funding. CAG acknowledges IPS for RAADRI grant.   Gamelas et al. (2023) Urban Clim., 49, 101446.  Querol et al. (2021) Sci. Total Environ., 779.  WHO (2021) WHO global air quality guidelines.   

Source apportionment of PM2.5 in the pre-pandemic versus pandemic period in an area near Lisbon: lessons for air quality management

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Source apportionment of PM2.5 in the pre-pandemic versus pandemic period in an area near Lisbon: lessons for air quality management

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