Source apportionment of fine particulate matter by positive matrix factorization in the metropolitan area of São Paulo, Brazil

Abstract

Aerosols are generated by a wide variety of sources, have different compositions, and have effects on climate, as well as on human health. Therefore, the analysis of aerosols in urban atmospheres has become increasingly more important. In this study, the sources of fine particulate matter (PM2.5) were analyzed by complementary analytical techniques over a one-year period (November 2014–November 2015) in an area characterized by vehicle and industrial emissions, in the eastern part of the Metropolitan Area of São Paulo, Brazil. The study area is near the largest airport in South America in number of flights. Concentrations of trace elements, ionic species, and black carbon were studied. The annual mean concentration was 22.1 ± 13.2 μg m−3 for PM2.5 and 1.87 ± 1.28 μg m−3 for black carbon. During the study period, the São Paulo State 24-h standard for PM2.5 (60 μg m−3) was exceeded five times. Seasonal variations in PM mass and composition reflected the influence of meteorological conditions and heavy-duty vehicle traffic. A stable atmosphere and a lack of rain are the main meteorological factors contributing to higher concentrations in the winter months. Elemental analysis identified Na, Al, Si, S, Cl, K, Ca, Fe, Zn, nitrate, sulfate, and ammonium as the main components, related to vehicle emissions and resuspension of soil and pavement dust. A Positive Matrix Factorization model revealed 4 p.m.2.5 sources (and their contributions): heavy-duty vehicles (52%), soil dust (26%), light-duty vehicles (18%), and other (probably industrial processes, 4%). Our results suggest a link between PM2.5 concentrations and local emissions, given that the study site is surrounded by major highways. Traffic was found to be the most important source of PM, and more attention should be given to its contribution to PM2.5 concentrations.