Sources, distribution and variability of hydrocarbons in total atmospheric suspended particulates of two Brazilian areas influenced by sugarcane burning

Polycyclic aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons (AHs), such as n-alkanes, hopanes and steranes, were studied in relation to total atmospheric suspended particulates (TSP). Two representative Brazilian cities affected by sugarcane monoculture practices, with their rural surroundings, were chosen for the study. The cities chosen were Maceió (state of Alagoas, NE-Brazil) and Campos dos Goytacazes (state of Rio de Janeiro, SE-Brazil). Samples were collected during the harvesting period, when sugarcane burning occurs, and during the non-harvesting period. The aliphatic hydrocarbon fingerprints suggest a marked contribution of biogenic inputs and a slight contamination by aliphatics in areas far from the urban regions. In the urban areas, some petroleum contributions were observed, marked by the presence of hopanes (m/z 191) and steranes (m/z 217) in the mass chromatographic profiles. A marked increase in PAH concentrations was detected during the sugarcane burning periods, mainly at Campos dos Goytacazes. In a similar approach, n-alkane concentrations and BaP/nC₂₄ ratios were higher during the sugarcane burning periods. These increases were mainly associated with PAH production by the pyrogenic process in relation to aliphatic hydrocarbons with the same carbon numbers. The PAH isomeric ratios and the mixture of petrogenic and pyrogenic compounds of the TSP suggest atmospheric contamination for all regions as a whole, but the more elevated pyrogenic contribution during the sugarcane burning period implies that the impact of this activity is relevant.