Residential wood combustion (RWC) emits high amounts of volatile organic compounds (VOCs) into ambient air, leading to formation of secondary organic aerosol (SOA), and various health and climate effects. In this study, the emission factors of VOCs from a logwood-fired modern masonry heater were measured using a Proton-Transfer-Reactor Time-of-Flight Mass Spectrometer. Next, the VOCs were aged in a 29 m Teflon chamber equipped with UV black lights, where dark and photochemical atmospheric conditions were simulated. The main constituents of the VOC emissions were carbonyls and aromatic compounds, which accounted for 50%-52% and 30%-46% of the detected VOC emission, respectively. Emissions were highly susceptible to different combustion conditions, which caused a 2.4-fold variation in emission factors. The overall VOC concentrations declined considerably during both dark and photochemical aging, with simultaneous increase in particulate organic aerosol mass. Especially furanoic and phenolic compounds decreased, and they are suggested to be the major precursors of RWC-originated SOA in all aging conditions. On the other hand, dark aging produced relatively high amounts of nitrogen-containing organic compounds in both gas and particulate phase, while photochemical aging increased especially the concentrations of certain gaseous carbonyls, particularly acid anhydrides.

Abstract. The Puijo aerosol-cloud observation station is a unique measurement site for its location in the mixed region between the boreal forestland and the municipality of Kuopio, Finland. A measurement campaign was carried out at the station during fall 2010. An Aerodyne high-resolution timeof-flight aerosol mass spectrometer (HR-Tof-AMS) was deployed to characterize the atmospheric submicron aerosols. Positive matrix factorization (PMF) was applied to the unified high-resolution mass spectra organic species with NO + and NO + 2 ions to discover the intrinsic relationships between the organic and inorganic species and their daily cycles. On average, the submicron aerosols in this study were dominated by organic and sulfate species, composing 48.2 and 28.7 % of total observed aerosol mass, respectively, with smaller contributions from ammonium (9.3 %), nitrate (4.9 %), chloride (0.8 %) and BC (8.1 %). The sources of these species included the primary emissions originating from the city area, secondary formation from both natural and anthropogenic emissions and regional transport. The PMF analysis succeeded in separating the mixed organic and inorganic spectra into three distinct organic and one inorganic factors. For organic factors, the semi-volatile oxygenated organic aerosol (SVOOA) and low-volatility oxygenated OA (LVOOA) accounted for 54.8 and 36.3 % of total organic masses, respectively, while the hydrocarbon-like organic aerosol (HOA) accounted for 8.9 % of total organics, with its main source from urban emissions. The inorganic factor is identified as NH 4 NO 3 , comprising 6.9 % of the fitted aerosol mass by PMF. Based on the PMF results, the nitrate species were separated into organic and inorganic components, with the organic nitrates contributing one-third of the total nitrate mass. The results highlight both anthropogenic and biogenic emissions as important atmospheric aerosol sources in a foresturban mixed region.

Diesel exhaust particles are the major constituent of urban carbonaceous aerosol being linked to a large range of adverse environmental and health effects. In this work, the effects of fuel reformulation, oxidation catalyst, engine type, and engine operation parameters on diesel particle emission characteristics were investigated. Particle emissions from an indirect injection (IDI) and a direct injection (DI) engine car operating under steady-state conditions with a reformulated low-sulfur, low-aromatic fuel and a standard-grade fuel were analyzed. Organic (OC) and elemental (EC) carbon fractions of the particles were quantified by a thermal-optical transmission analysis method and particle size distributions measured with a scanning mobility particle sizer (SMPS). The particle volatility characteristics were studied with a configuration that consisted of a thermal desorption unit and an SMPS. In addition, the volatility of size-selected particles was determined with a tandem differential mobility analyzer technique. The reformulated fuel was found to produce 10-40% less particulate carbon mass compared to the standard fuel. On the basis of the carbon analysis, the organic carbon contributed 27-61% to the carbon mass of the IDI engine particle emissions, depending on the fuel and engine operation parameters. The fuel reformulation reduced the particulate organic carbon emissions by 10-55%. In the particles of the DI engine, the organic carbon contributed 14-26% to the total carbon emissions, the advanced engine technology, and the oxidation catalyst, thus reducing the OC/EC ratio of particles considerably. A relatively good consistency between the particulate organic fraction quantified with the thermal optical method and the volatile fraction measured with the thermal desorption unit and SMPS was found.

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