biostudies-literatureUnknown49Gamelas CAThe lockdowns held due to the COVID-19 pandemic conducted to changes in air quality. This study aimed to understand the variability of PM_2.5 levels and composition in an urban-industrial area of the Lisbon Metropolitan Area and to identify the contribution of the different sources. The composition of PM_2.5 was assessed for 24 elements (by PIXE), secondary inorganic ions and black carbon. The PM_2.5 mean concentration for the period (December 2019 to November 2020) was 13 ± 11 μg.m^-3. The most abundant species in PM_2.5 were BC (19.9%), SO₄ ^2- (15.4%), NO₃ ^- (11.6%) and NH₄ ⁺ (5.3%). The impact of the restrictions imposed by the COVID-19 pandemic on the PM levels was found Urban climate101446https://www.ebi.ac.uk/biostudies/studies/S-EPMC9932663biostudies-literatureSource apportionment of PM_2.5 before and after COVID-19 lockdown in an urban-industrial area of the Lisbon metropolitan area, Portugal.PMC9932663Canha NAlves CAlmeida SMVicente ABorges SSilva AGamelas CAKertesz ZfalseSource apportionment of PM_2.5 before and after COVID-19 lockdown in an urban-industrial area of the Lisbon metropolitan area, Portugal.The lockdowns held due to the COVID-19 pandemic conducted to changes in air quality. This study aimed to understand the variability of PM_2.5 levels and composition in an urban-industrial area of the Lisbon Metropolitan Area and to identify the contribution of the different sources. The composition of PM_2.5 was assessed for 24 elements (by PIXE), secondary inorganic ions and black carbon. The PM_2.5 mean concentration for the period (December 2019 to November 2020) was 13 ± 11 μg.m^-3. The most abundant species in PM_2.5 were BC (19.9%), SO₄ ^2- (15.4%), NO₃ ^- (11.6%) and NH₄ ⁺ (5.3%). The impact of the restrictions imposed by the COVID-19 pandemic on the PM levels was found 2023-01-01T00:00:00Z2023 May2025-05-29T19:43:34.838Z2025-04-05T18:34:36.484ZS-EPMC99326633682027310.1016/j.uclim.2023.101446