Determination of n-alkanes, PAHs and nitro-PAHs in PM2.5 and PM1 sampled in the surroundings of a municipal waste incinerator

This work investigates n-alkanes in the range C14-C32, polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (nitro-PAHs) composition of PM2.5 and PM1 collected in the surroundings of a municipal waste incinerator close to Bologna (Northern Italy). The particulate matter was sampled in eight stations: one of these was located inside the urban area of Bologna, while the others were placed in a domain of 8 × 9 km2 around the incinerator plant. Two monitoring campaigns were carried out, in summer 2008 and in winter 2009. In each campaign, two stations were placed in zones of maximum impact of plant emissions and other two ones as their controls. The study of n-alkanes in atmospheric particulate was performed to understand the contribution of anthropogenic and biogenic sources, PAHs and nitro-PAHs were selected to investigate PM composition near an incinerator plant. Higher concentrations of PAHs and, to a less extent, of n-alkanes were measured in the cold season. This can be due to several reasons, namely, an increased combustion of fossil fuel during wintertime, stagnant atmospheric conditions and lower temperatures that not only favour gas-to-particles partitioning but also reduce atmospheric reactivity. The impact of combustion in the cold season was also confirmed by the higher percentage content of PAHs in PM1 than in PM2.5. On the contrary, higher amount of nitro-derivatives were measured in summer than in winter, suggesting that the contribution of secondary aerosol is not negligible in the hot season. The most abundant n-alkanes were the long-chain homologues (>C27) deriving from anthropogenic sources as indicated by the Carbon Preference Indexes. In both seasons, the sites chosen as controls were characterized by higher concentrations of PAHs than the respective maxima suggesting that extra-incinerator sources, especially vehicles emissions, are the main responsible for PAHs in PM2.5. On the contrary, in winter, PM1 was enriched in PAHs in the site close to the incinerator with respect to its control.