Characterization of atmospheric aerosols in the Po valley during the supersito campaigns - Part 3: Contribution of wood combustion to wintertime atmospheric aerosols in Emilia Romagna region (Northern Italy)

This paper investigates the influence of wood combustion on PM in fall/winter that are the most favorable seasonal periods with presumed intense biomass burning for residential heating due to low temperatures. As a part of the Supersito project, nearly 650 PM2.5samples were daily collected at urban and rural sites in Emilia Romagna (Northern Italy) infive intensive experimental campaigns throughout the years from 2011 to 2014. From specific compounds related to wood combustion a set of 58 organic compounds was determined, such as anhydrosugars, primary biological sugars, low-molecular-weight carboxylic acids, methoxylated phenols, PAHs and carbonaceous components (EC/OC). Levoglucosan was by far the most dominant anhydrosugar, both on a relative and an absolute basis (35 e1043 ng m 3), followed by mannosan (7e121 ng m 3) and galactosan (4e52 ng m 3), indicating that wood burning for domestic heating is a diffuse regional source during the seasons studied. Different diagnostic ratios between anhydrosugars and methoxylated phenols were computed to discriminate the prevalent contribution of hardwood as combustion fuel. The investigated 19 high molecular weight PAHs were more abundant at the urban than at the rural site, with mean total value of 4.3 and 3.2 ng m 3 at MS and SP, respectively. The strong contribution of wood combustion to atmospheric PAHs was indicated by the positive correlation between levoglucosan and the most abundant PAHs (R 2 ¼0.71÷0.79) and individually with benzo(a)pyrene (R 2 ¼0.79). By using this correlation, it was estimated that wood burning contributed nearly 77% to BaP concentration in the winter months. Based on the ratio between levoglucosan and OC data, it could be concluded that the wood burning contributed about 35% to OC during the cold NovembereFebruary periods and the contribution was similar at both sampling sites.