Contribution of wood combustion to PAH and PCDD/F concentration in two urban sites in Northern Italy

The use of residential wood combustion represents an important renewable energy source, but it contributes in a considerable way to atmospheric particulate matter (PM) concentration in urban as well as in rural sites. Moreover, recent studies pointed out wood burning as an important source of PAH. In the present work, the contribution of wood combustion to benzo(a)pyrene (B[a]P) and polychlorodibenzo-p-dioxins and polychlorodibenzofurans (PCDD/F) concentrations was investigated, using levoglucosan as a marker. PM10 samples were collected daily for six months in two sites located in Piemonte (Northern Italy): Torino and Susa. Composite monthly samples were chemically characterized, analyzing the concentrations of levoglucosan, B[a]P, PCDD/Fs, organic carbon (OC), elemental carbon, major anions and cations, metals. PM and OC concentrations were almost twice in Torino with respect to Susa, while levoglucosan and B[a]P concentrations were almost comparable in the two sites. Therefore, wood combustion affects more Susa than Torino. Concentrations of B[a]P and levoglucosan were highly correlated in both sites. Using the macro tracer method and the emission factors reported in literature, the wood combustion percentage contribution to B[a]P concentration was estimated and resulted as the main source in both sites. The levoglucosan : soluble potassium ratio was higher in Torino with respect to Susa, indicating that combustion plants with different efficiency are used in the two sites. PCDD/F concentrations were higher in Torino than in Susa.