A source apportionment study was performed for particulate matter in the small village of Roveredo, Switzerland, where more than 70% of the households use wood burning for heating purposes. A two-lane trans-Alpine highway passes through the village and contributes to the total aerosol burden in the area. The village is located in a steep Alpine valley characterized by strong and persistent temperature inversions during winter, especially from December to February. During two winter and one early spring campaigns, a seven-wavelength aethalometer, high volume (HIVOL) samplers, an Aerodyne quadrupole aerosol mass spectrometer (AMS), an optical particle counter (OPC), and a Sunset Laboratory OCEC analyzer were deployed to study the contribution of wood burning and traffic aerosols to particulate matter. A linear regression model of the carbonaceous particulate mass in the submicrometer size range CM(PM1) as a function of aerosol light absorption properties measured by the aethalometer is introduced to estimate the particulate mass from wood burning and traffic (PM(wb), PM(traffic)). This model was calibrated with analyses from the 14C method using HIVOL filter measurements. These results indicate that light absorption exponents of 1.1 for traffic and 1.8-1.9 for wood burning calculated from the light absorption at 470 and 950 nanometers should be used to obtain agreement of the two methods regarding the relative wood burning and traffic emission contributions to CM(PM1) and also to black carbon. The resulting PM(wb) and PM(traffic) values explain 86% of the variance of the CM(PM1) and contribute, on average, 88 and 12% to CM(PM1), respectively. The black carbon is estimated to be 51% due to wood burning and 49% due to traffic emissions. The average organic carbon/total carbon (OC/TC) values were estimated to be 0.52 for traffic and 0.88 for wood burning particulate emissions.

Throughout the winter months, the village of Roveredo, Switzerland, frequently experiences strong temperature inversions that contribute to elevated levels of particulate matter. Wood is used as fuel for 75% of the domestic heating installations in Roveredo, which makes it a suitable location to study wood burning emissions in the atmosphere in winter. An Aerodyne quadrupole aerosol mass spectrometer (Q-AMS) was used to characterize the composition of the submicrometer, non-refractory aerosol particles at this location during two field campaigns in March and December 2005. Wood burning was found to be a major source of aerosols at this location in winter. Organics dominated the composition of the aerosols from this source, contributing up to 85% of the total AMS measured mass during the afternoon and evening hours. Carbonaceous particle analysis showed that organic carbon composed up to 86% of the total carbon mass collected at evening times. Results from 14C isotope determination revealed that up to 94% of the organic mass came from non-fossil sources, which can be attributed mostlyto wood burning. The unique combination of off-line 14C isotope analysis and on-line aerosol mass spectrometry was used to identify periods during which organic mass was mainly from wood burning emissions and allowed for the identification of the AMS spectral signature of this source in the atmosphere. The identified ambient signature of wood burning was found to be very similar to the mass spectral signature obtained during the burning of chestnut wood samples in a small stove and also to the spectrum of levoglucosan. Particles from wood burning appeared to be composed of highly oxygenated organic compounds, and mass fragments 60, 73, and 137 have been suggested as marker fragments for wood burning aerosols. Mass fragment 44, which is used as a marker for oxygenated organic aerosols (OOA), contributed about 5% to the total organic signal from primary wood burning sources. The ratio of the organic mass emitted from wood burning to m/z 60 in Roveredo is 36. This ratio may be used to provide an estimate of the organic aerosol mass emitted from wood burning in other locations.

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