| 1. |
- Nielsen, Ingeborg E., et al.
(författare)
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Time-resolved analysis of particle emissions from residential biomass combustion – Emissions of refractory black carbon, PAHs and organic tracers
- 2017
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 165, s. 179-190
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved particle emissions from a conventional wood stove were investigated with aerosol mass spectrometry to provide links between combustion conditions, emission factors, mixing state of refractory black carbon and implications for organic tracer methods. The addition of a new batch of fuel results in low temperature pyrolysis as the fuel heats up, resulting in strong, short-lived, variable emission peaks of organic aerosol-containing markers of anhydrous sugars, such as levoglucosan (fragment at m/z 60). Flaming combustion results in emissions dominated by refractory black carbon co-emitted with minor fractions of organic aerosol and markers of anhydrous sugars. Full cycle emissions are an external mixture of larger organic aerosol-dominated and smaller thinly coated refractory black carbon particles. A very high burn rate results in increased full cycle mass emission factors of 66, 2.7, 2.8 and 1.3 for particulate polycyclic aromatic hydrocarbons, refractory black carbon, total organic aerosol and m/z 60, respectively, compared to nominal burn rate. Polycyclic aromatic hydrocarbons are primarily associated with refractory black carbon-containing particles. We hypothesize that at very high burn rates, the central parts of the combustion zone become air starved, leading to a locally reduced combustion temperature that reduces the conversion rates from polycyclic aromatic hydrocarbons to refractory black carbon. This facilitates a strong increase of polycyclic aromatic hydrocarbons emissions. At nominal burn rates, full cycle emissions based on m/z 60 correlate well with organic aerosol, refractory black carbon and particulate matter. However, at higher burn rates, m/z 60 does not correlate with increased emissions of polycyclic aromatic hydrocarbons, refractory black carbon and organic aerosol in the flaming phase. The new knowledge can be used to advance source apportionment studies, reduce emissions of genotoxic compounds and model the climate impacts of refractory black carbon, such as absorption enhancement by lensing.
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| 2. |
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| 3. |
- Malmborg, Vilhelm, et al.
(författare)
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Biomass burning emissions and influence of combustion variables in the cone-calorimeter
- 2022
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Ingår i: ; , s. 170-170
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Konferensbidrag (refereegranskat)abstract
- Emissions from biomass burning are highly variable and depend on combustion conditions as well as fuel properties. Simultaneous emissions from pyrolysis, smouldering, and combustion of the biomass material(s) burning leads to uncertainties in how these processes contribute to emissions of individual or groups of compounds as well as to total particle emissions. These uncertainties are difficult to constrain when analysing real-world emissions but also when performing laboratory studies of e.g., cook-stove emissions in more controlled environments. This study was designed to reduce some of this variability by enabling highly reproducible conditions by controlling combustion via adjustment of a few key factors. The aim of this study was to identify how these factors influenced emissions, and how different pyrolysis and burn conditions in turn contributed to the particle emissions.In this study, we used a controlled atmosphere cone calorimeter according to ISO 5660‐5. We controlled fuel moisture content, the air flow to the combustion and O2 available for combustion, and the total heat flux (HF) to the fuel to study the independent effect of combustion variables on the aerosol emissions. In each experiment a small 10x10x1 cm piece of Birch-wood was put in a sample holder and combusted under controlled conditions. We conducted over 40 experiments, varying HF and flow conditions while monitoring fuel mass loss to quantify emission yields. An Aerosol Mass Spectrometer (AMS, Aerodyne Billerica, USA), a multi‐wavelength aethalometer (AE33, Magee Sci., USA) and a particle size spectrometer (DMS5000, Cambustion, UK) measured time‐resolved evolution in particle properties during burns. Our results showed that pyrolysis conditions in the absence of O2 resulted in organic aerosol (OA) emissions with mass yields (g/g fuel) from a few percent at the lowest HF and up to ten percent at the highest HF. During combustion in air, equivalent black carbon (eBC) emissions were found to moderately increase with increasing HF. eBC was also found to increase when the O2 availability or combustion was reduced (O2 deficient combustion). Polycyclic aromatic hydrocarbon (PAH) was here defined separately from OA in the AMS analysis. PAH emissions were low for pyrolysis and combustion at high air flows (excessive O2 availability). In contrast, O2 deficient combustion conditions resulted in dramatically increased PAH emissions, with yields as high as to 0.5% (g/g fuel). The relationship between PAH emissions and availability of air and O2 during combustion is illustrated in Figure 1. Future analyses include a more detailed PAH analysis including off-line GC-MS, thermal-optical carbon analysis, UV-VIS absorption of MeOH soluble OA. We will parameterize emissions based on the initial conditions such as HF, moisture content, air flow rate (cooling) and O2 availability. A mechanistic understanding of relationships between combustion variables and emissions can aid the development of cleaner biomass combustion technologies and will improve fire emission models.
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| 5. |
- Lutic, Doina, et al.
(författare)
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Detection of Soot Using a Resistivity Sensor Device Employing Thermophoretic Particle Deposition
- 2010
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Ingår i: Journal of Sensors. - : Hindawi. - 1687-725X .- 1687-7268. ; 2010:421072
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Tidskriftsartikel (refereegranskat)abstract
- Results are reported for thermophoretic deposition of soot particles on resistivity sensors as a monitoring technique for diesel exhaust particles with the potential of improved detection limit and sensitivity. Soot with similar characteristics as from diesel exhausts was generated by a propane flame and diluted in stages. The soot in a gas flow at 240–270C∘ was collected on an interdigitated electrode structure held at a considerably lower temperature, 105–125C∘. The time delay for reaching measurable resistance values, the subsequent rate, and magnitude of resistance decrease were a function of the distance between the fingers in the electrodes and the degree of dilution of the soot containing flow. Soot deposition and subsequent removal by heating the sensor support was also performed in a real diesel exhaust. Good similarities between the behavior in our laboratory system and the real diesel exhaust were noticed.
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| 6. |
- Novakovic, Maja, et al.
(författare)
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Analysis of Exhaust PM Composition Emitted from Non-Sooting Volatile Alcohols
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The combustion engine, a well-known source of aerosols, has seen remarkable improvements regarding efficiency and emissions. A drawback of the conventional compression ignition (CI) engine is its requirement for a high cetane number fuel, i.e. diesel which contains long carbon chains forming particulate matter (PM) when combusted in the conventional diesel combustion (CDC) process. A previous study of PM from partially premixed combustion (PPC) and CDC utilizing ethanol and methanol in a Scania D13 engine without emission after treatment systems (EATS) showed that the particle sizes from the alcohol combustion never exceeded 30 nm in diameter. Until now, the characteristics (origin, formation and constituents) of these nano-sized particles formed in the PPC and CDC process were unknown. It has been hypothesized that they originate from lubrication oil and engine wear.
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| 7. |
- Pagels, Joakim, et al.
(författare)
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Chemical composition and mass emission factors of candle smoke particles
- 2009
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 40:3, s. 193-208
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to investigate the physical and chemical properties of particle emissions from candle burning in indoor air. Two representative types of tapered candies were studied during steady burn, sooting burn and smouldering (upon extinction) under controlled conditions in a walk-in stainless steel chamber. Steady burn emits relatively high number emissions of ultrafine particles dominated by either phosphates or alkali nitrates. The likely source of these particles is flame retardant additives to the wick. Sooting burn in addition emits larger particles mainly consisting of agglomerated elemental carbon. This burning mode is associated with the highest mass emission factors. Particles emitted during smouldering upon extinction are dominated by organic matter. A mass closure was illustrated for the total mass concentration, the summed mass concentration from chemical analysis and the size-integrated mass concentration assessed from number distribution measurements using empirically determined effective densities for the three particle types. (C) 2008 Published by Elsevier Ltd.
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| 8. |
- Rissler, Jenny, et al.
(författare)
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Experimental determination of deposition of diesel exhaust particles in the human respiratory tract
- 2012
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 48, s. 18-33
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Tidskriftsartikel (refereegranskat)abstract
- Diesel emissions are a major contributor to combustion-generated airborne ambient particles. To understand the role of diesel particulate emissions on health effects, it is important to predict the actual particulate dose deposited in the human respiratory tract, with respect to number, surface area and mass. This is complicated by the agglomerate nature of some of these particles. In this study the respiratory tract deposition fraction in the size range 10-500 nm, was determined for 10 healthy volunteers during both idling and transient engine running conditions of a heavy duty diesel engine. The aerosol was characterized with respect to both chemical and physical properties including size resolved particle effective density. The dominating part of the emitted particles had an agglomerate structure. For those formed during transient running conditions, the relationship between particle mass and mobility diameter could be described by a power law function. This was not the case during idling, most likely because of volatile compounds condensing on the agglomerates. The respiratory tract particle deposition revealed large intra-subject variability with some subjects receiving a dose that was twice as high as that of others, when exposed to the same particle concentration. Associations were found between total deposited fractions (TDF), and breathing pattern. There was a difference between the idling and transient cycle with TDF being higher with respect to number during idling. The measured size-dependent deposition fraction of the agglomerated exhaust particles from both running conditions was nearly identical and closely resembled that of spherical hydrophobic particles, if plotted as a function of mobility diameter. Thus, for the size range covered, the mobility diameter could well describe the diameter-dependent particle respiratory tract deposition probability, regardless of the agglomeration state of the particles. Whilst mobility diameter well describes the deposition fraction, more information about particle characteristics is needed to convert this to volume equivalent diameter or estimate dose with respect to surface area or mass. A methodology is presented and applied to calculate deposited dose by surface area and mass of agglomerated particles. The methodology may be useful in similar studies estimating dose to the lung, deposition onto cell cultures and in animal studies. (C) 2012 Elsevier Ltd. All rights reserved.
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| 9. |
- Martinsson, Johan, et al.
(författare)
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Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol
- 2015
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:24, s. 14663-14671
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Angstrom exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.
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