Ferreira, António Luís Pimentel2026-02-062026-02-062025http://hdl.handle.net/10400.5/116899Tese de mestrado, Química (Química), 2025, Universidade de Lisboa, Faculdade de CiênciasIndoor air quality has significant impacts on human health, potentially during sleep periods. This study focused on the chemical characterization of PM2.5 in air samples collected during the night in 30 sleeping rooms in the Lisbon Metropolitan Area, with the objective of quantifying the content of watersoluble inorganic ions and doing source apportionment. Samples were collected overnight, both indoors and outdoors, and were subsequently analyzed by ion-exchange chromatography. The results showed that, on average, soluble inorganic ions and black carbon constituted 23.6% and 18.9% of the PM2.5 mass, respectively, leaving a large portion of the particle’s mass uncharacterized. The chemical profiles indoors and outdoors were similar, suggesting a strong influence from external sources. Principal component analysis (PCA) identified three main sources for particulate matter: marine aerosols, secondary sulfate aerosols, and road emissions (both indoors and outdoors). Chloride to sodium ion ratios measured in the exterior suggests aerosol aging. A significant difference (α = 5%) in oxidative potential was observed between the indoor and outdoor environments, which indicates the presence of other polluting sources not identified in this study. This highlights the need for future investigations to characterize the remaining mass of the particulate matter to identify other sources.application/pdfporPM2.5Indoor air qualitySource apportionmentIon-exchange chromatographyOvernight samplingmaster thesis204174473