Hydrocarbon concentration and source appraisal in atmospheric particulate matter (PM₂.₅) of an urban tropical area

Polycyclic aromatic (46 PAHs) and aliphatic hydrocarbons (C12-C40) were studied in atmospheric particulate matter sampled in Rio de Janeiro Metropolitan Area (RJMA). In total, 236 samples from six different sites were collected simultaneously and weekly over 1 year (January-December 2011) allowing a robust atmospheric characterization of fine particulate matter (PM2.5). Hydrocarbon concentration was in general low compared to previous studies in the area (PAHs range 0.25-19.3 ng m(-3)), possibly due to changes in fuel composition over time. Precipitation is the main meteorological parameter that rules particulate and hydrocarbon concentration, modifying PAH typology by scavenging. Aliphatic and aromatic diagnostic ratios gave indications conflicting with combustion features. However, ratios showed differences among sites. Principal component analysis (PCA) associated to multiple linear regressions (MLR) allowed quantitative estimate of sources and effectively indicated vehicular emission as the main hydrocarbon source in the atmospheric particulate matter.