Carbonaceous components and major ions in PM10 from the Amazonian Basin

Abstract

Air pollution mainly resulting from deforestation and agricultural activities has become one of the major concerns in the Amazonian Basin. A detailed analysis of the PM10 chemical composition is critical for devising pollution control measures and improving climate models. In this study, daily 24-h filter samples were collected and analyzed in different sites of the Amazon Basin between 2008 and 2016 (over 200 samples). The six sampling sites were classified into two groups, one in South Amazonia, a region with strong influence of land occupation, and another in a remote forest region to the North. The high mean concentrations of PM10 and the occurrences of extreme events at the Southern site denote air pollution episodes. High correlations between the temporal trends of PM10 and primary species linked to soil re-suspension and biomass burning highlight the contribution of these sources of air pollution in the region. Significant differences between PM10 in the South and North regions were observed, for which levels of 72.6 ± 66.5 μg m−3 and 8.9 ± 4.2 μg m−3, respectively. The average concentrations of organic carbon (OC) and elemental carbon (EC) in the aerosol were 5.81 ± 4.18 μg m−3, 2.43 ± 1.65 μg m−3 and 5.17 ± 5.54 μg m−3, 0.51 ± 0.41 μg m−3, respectively, for the Southern and Northern Amazonia sampling sites. The aerosol was largely composed of inorganic species in Southern Amazonia, whose carbonaceous matter accounted for 16% of the gravimetrically measured PM10. However, in the forest region, the contribution of carbonaceous species, mainly OC, accounted for >90% and remained more constant throughout the seasons. Na+ was the dominant water soluble ion in samples from the Southern region, followed by SO4−2, NO3−, Ca2+ and K+. High levels of carbonate (CC) were also observed for these samples. For the Northern region, SO4−2 was the dominant soluble ion, followed by K+ and NH4+. Some of these species exhibited a clear seasonal trend during the study period. This study provides a better understanding of the current state of air pollution in diversified Amazon basin sites.