Inorganic and Organic Acids in the Atmosphere of the Urban Area of the City of Salvador, Brazil

Different fuels are used in Brazil and there is little knowledge about the presence of organic and inorganic acids in the atmosphere of the Brazilian cities. HNO3, HCl, HCOOH and CH3COOH were sampled in the gas phase using passive samplers and thermodiffusion system, in which the H2SO4 particulate was also sampled, in five sites of Salvador. Ion chromatography analyses showed that the organic and inorganic acids measured contributed on average with 89 and 11%, respectively, to the acidity of the city’s atmosphere. The strong correlations between HCOOH, CH3COOH and HCl with CO and NO2 indicated a common source for these compounds, predominantly from vehicular emissions. H2SO4 showed strong correlations with PM10 (particulate matter 10 µm or less in diameter) and with its precursor SO2; and HNO3 with NO2 and NO precursors. Most of the compounds presented negative correlations with meteorological parameters. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) confirmed these observations. The ratios [HCOOH] / [CH3COOH] varied between 0.69-1.9, typical of urban areas.