Search

Residential wood combustion (RWC) is a significant source of gaseous and particulate emissions causing adverse health and environmental effects. Several factors affect emissions, but the effects of the fuel wood species on emissions are currently not well understood. In this study, the Nordic wood species (named BirchA, BirchB, Spruce, SpruceDry, Pine and Alder) were combusted in a modern stove, and the emissions were studied. The lowest emissions were obtained from the combustion of BirchA and the highest from Spruce and Alder. The fine particle mass (PM2.5) was mainly composed of elemental carbon (50–70% of PM2.5), which is typical in modern appliances. The lowest PAH concentrations were measured from BirchA (total PAH 107 µg/m3) and Pine (250 µg/m3). In the ignition batch, the PAH concentration was about 4-fold (416 µg/m3). The PAHs did not correlate with other organic compounds, and thus, volatile organic compounds (VOCs) or organic carbon (OC) concentrations cannot be used as an indicator of PAH emissions. Two birch species from different origins with a similar chemical composition but different density produced partially different emission profiles. This study indicates that emission differences may be due more to the physical properties of the wood and the combustion conditions than to the wood species themselves. [ABSTRACT FROM AUTHOR]

Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon (BrC) to the total particulate light absorption in the wavelength range of 370–950 nm (BrC 370–950) and the particulate absorption Ångström exponents (AAE 470/950) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC 370–950 was estimated to be from 1 % to 21 % for wood log stoves and 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC / EC) and BrC 370–950 indicated that a one-unit increase in OC / EC corresponded to approximately a 14 % increase in BrC 370–950. Additionally, BrC 370–950 was clearly influenced by the fuel moisture content and the combustion efficiency, while the effect of the combustion appliance type was less prominent. AAE 470/950 of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE 470/950 and OC / EC, an AAE 470/950 close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE 470/950 of 1.02, with BrC contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC from residential wood combustion with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for northern European wood stove emissions with relatively high OC / EC ratios. [ABSTRACT FROM AUTHOR]

Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the Earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon to the total particulate light absorption in the wavelength range of 370 to 950 nm (BrC370-950)and the particulate absorption Ångström exponents (AAE470/950) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC370-950 was estimated to be from 1 % to 21 % for wood log stoves and was primarily influenced by fuel moisture content and minimally affected by combustion appliance type. The BrC370-950 contribution was 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC/EC) and BrC indicated that a one unit increase in OC/EC corresponded to approximately a 14 % increase in BrC370-950. Additionally, BrC370-950 increased with decreasing combustion efficiency. AAE470/950 of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE470/950 and OC/EC, an AAE470/950 close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE470/950 of 1.02, with BrC370-950 contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC370-950 of RWC emissions with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for Northern European wood stove emissions with relatively high OC/EC ratios. [ABSTRACT FROM AUTHOR]

Residential wood combustion (RWC) emits large amounts of gaseous and particulate organic aerosol (OA). In the atmosphere, the emission is transformed via oxidative reactions, which are under daylight conditions driven mainly by hydroxyl radicals. This continuing oxidative aging produces secondary OA and may change the health- and climate-related properties of the emission. In this work, emissions from two modern residential logwood combustion appliances were photochemically aged in an oxidation flow reactor with various OH exposure levels, reaching up to 6 × 1011 s cm-3 (equivalent to one week in the atmosphere). Gaseous organic compounds were analysed by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS), while particulate OA was analysed online by an aerosol mass spectrometer (AMS) and offline by thermal-optical analysis and thermal desorption-gas chromatography mass spectrometry. Photochemical reactions increased the mass of particulate organic carbon by a factor of 1.3-3.9. The increase in mass took place during the first atmospheric equivalent day of aging, after which the enhancement was independent of the extent of photochemical exposure. However, aging increased the oxidation state of the particulate OA linearly throughout the assessed range, with ΔH:C/ΔO:C slopes between -0.17 and -0.49 in van Krevelen space. Aging led to an increase in acidic fragmentation products in both phases. For the volatile organic compounds measured by PTR-ToF-MS, the formation of small carbonylic compounds combined with the rapid degradation of primary volatile organic compounds such as aromatic compounds led to a continuous increase in both the O:C and H:C ratios. Overall, the share of polycyclic aromatic compounds (PACs) in particles degraded rapidly during aging, although some oxygen-substituted PACs, most notably naphthaldehydic acid, increased, in particular during relatively short exposures. Similarly, the concentrations of particulate nitrophenols rose extensively during the first atmospheric equivalent day. During continuous photochemical aging, the dominant reaction mechanisms shifted from the initial gas phase functionalisation/condensation to the transformation of the particulate OA by further oxidation reactions and fragmentation. The observed continuous transformation of OA composition throughout a broad range of OH exposures indicates that the entire atmospheric lifetime of the emission, from fresh to shortly aged to long-term aged emission (representative of long-range transported pollutants), needs to be explored to fully assess the potential climate and health effects of OA emissions. [ABSTRACT FROM AUTHOR]

In vitro, direct aerosol nanoparticle exposure of cells cultured at the air-liquid interface (ALI) has shown great potential over the conventional submerged cell exposure methods due to exposure relevancy and more accurate dose determination. Here, we present a design of an ALI cell exposure device, the thermocollector, which applies thermophoresis to deposit aerosol particles onto the cells. Computational numerical simulations were used to estimate the deposition flux and how it depended on particle properties. The deposition flux was approximately 250 particles/m2s for particles smaller than 100 nm, corresponding to an aerosol concentration of 1 #/cm3. This was also confirmed with experimental studies. For larger particles, the deposition rate depended more on particle properties; however, for fractal combustion derived soot particles, the deposition rate is practically size independent at the size range studied here. Finally, epithelial cells were exposed with wood combustion aerosol, and the toxicologic responses were investigated. The cell viability decrease and DNA damage were detected after the exposure. These effects were not detected in cells after the exposure to clean air in this cell exposure system. Copyright © 2019 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]