Comprehensive analysis of PM10 in the metropolitan area of São Paulo – Part I: Chemical characterisation and source apportionment

Résumé fourni par la source

In this study, 126 PM 10 samples were collected in the Metropolitan Area of São Paulo (MASP), Brazil, with 24-h sampling performed every three days from July 2022 to July 2023, as part of the BIOMASP+ project. The reconstructed PM 10 concentrations ranged from 4.8 to 61.3 μg m -3 (annual mean of 17.2 ± 12.2 μg m -3 ), with levels during the dry season about twice as high as in the rainy season. Organic matter (OM) was the dominant component (49% of PM 10 mass), of which 17% was chemically resolved, with humic-like substances (HuLiS) accounting for 59% of the identified organic fraction. The inorganic fraction consisted mainly of SO 4 2- (16%), NO 3 - (8%), and elemental carbon (7%). Oxalate, malonic acid, methanesulfonic acid (MSA), and malic acid accounted for 81% of the quantified organic acid mass. Enrichment factors identified clear anthropogenic signatures for As, Cd, Cu, Pb, Rb, Sb, Se, Ti, and Zn. Despite lower levoglucosan concentrations (99.2 ± 153.2 ng m -3 ) than those reported in previous MASP studies, dry-season levels were approximately five times higher than those in the rainy season, confirming the influence of biomass burning on PM10 composition. Conversely, elevated arabitol and mannitol concentrations during the wet season reflected the contribution of biogenic sources. An 11-factor PMF solution identified contributions from mineral dust (20.4%), sulfate-rich (14.8%), biomass burning (12.0%), road dust (11.7%), primary biogenic (9.7%), aged sea salt (9.2%), traffic (7.0%), nitrate-rich (6.0%), industrial (3.3%), secondary biogenic oxidation (3.3%), and sea salt (2.7%). These findings provide a comprehensive knowledge on PM 10 chemical composition to improve the identification of emission sources in a region where air quality standards are frequently exceeded, emphasizing the importance of targeted mitigation strategies and sustained monitoring efforts.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.