Particulate pollutants in the Brazilian city of São Paulo: 1-year investigation for the chemical composition and source apportionment

摘要

São Paulo in Brazil has relatively relaxed regulations for ambient airpollution standards and often experiences high air pollution levels due toemissions of particulate pollutants from local sources and long-rangetransport of air masses impacted by biomass burning. In order to evaluate thesources of particulate air pollution and related health risks, a year-roundsampling was done at the University of São Paulo campus (20 m a.g.l.),a green area near an important expressway. The sampling was performed forPM ( ≤ 2. 5 µm) and PM ( ≤  10 µm) in2014 through intensive (everyday sampling in wintertime) and extensivecampaigns (once a week for the whole year) with 24 h of sampling. This yearwas characterized by having lower average precipitation compared tometeorological data, and high-pollution episodes were observed all yearround, with a significant increase in pollution level in the intensivecampaign, which was performed during wintertime. Different chemicalconstituents, such as carbonaceous species, polycyclic aromatic hydrocarbons(PAHs) and derivatives, water-soluble ions, and biomass burning tracers wereidentified in order to evaluate health risks and to apportion sources. Thespecies such as PAHs, inorganic and organic ions, and monosaccharides weredetermined using chromatographic techniques and carbonaceous species usingthermal-optical analysis. Trace elements were determined using inductivelycoupled plasma mass spectrometry. The risks associated with particulate matterexposure based on PAH concentrations were also assessed, along with indexessuch as the benzo[]pyrene equivalent (BaPE) and lung cancer risk (LCR). HighBaPE and LCR were observed in most of the samples, rising to critical valuesin the wintertime. Also, biomass burning tracers and PAHs were higher in thisseason, while secondarily formed ions presented low variation throughout theyear. Meanwhile, vehicular tracer species were also higher in the intensivecampaign, suggesting the influence of lower dispersion conditions in thatperiod. Source apportionment was performed using positive matrix factorization (PMF),which indicated five different factors: road dust, industrial emissions,vehicular exhaust, biomass burning and secondary processes. The resultshighlighted the contribution of vehicular emissions and the significant inputfrom biomass combustion in wintertime, suggesting that most of theparticulate matter is due to local sources, in addition to the influence ofpre-harvest sugarcane burning.