Size-segregated aerosol chemical composition from an agro-industrial region of Sao Paulo state, Brazil

Abstract

The main objective of this research included a detailed inorganic and organic characterisation of atmospheric aerosols, to understand the changes in their composition as a result of the implementation of the Sugar and Ethanol Industry Green Protocol, in the southeastern region of Brazil. A set of 10 samples segregated into PM2.5, PM2.5-10 and PM>10 fractions were collected in May and July of 2014, covering the beginning of the sugarcane harvest period. The analytical methods included gravimetric determination, water-soluble ions by ion chromatography, major elements by inductively coupled plasma mass spectrometry, carbonaceous content by a thermal-optical system and organic speciation by gas chromatography-mass spectrometry. A substantially higher mean concentration (57 +/- 36 mu g m(-3)) was obtained for PM2.5 in comparison with PM2.5-10 (15 +/- 6.2 mu g m(-3)) and PM>10 (8.5 +/- 13 mu g m(-3)). The carbonaceous content represented, on average, approximately 18 and 21 % of the particulate matter of the PM2.5 and PM2.5-10 fractions, respectively. On average, water-soluble ions accounted for 12 and 7.7 % of the PM2.5 and PM2.5-10 mass, respectively. With the implementation of the Green Protocol, a decrease of biomass burning ion tracers would be expected, however, this trend was not observed. With regard to major elements, aerosols from both fractions were dominated by K, Ca, Na and Al. Concentrations of the major elements were lower than those observed in earlier studies. Organic compounds were present at higher levels in the fine than in the coarse fraction. n-Alkanes, n-alkanoic acids and polycyclic aromatic hydrocarbons related to biomass combustion showed lower concentrations than previously reported.