| 1. |
- Watne, Ågot, 1983, et al.
(författare)
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Ozone and OH-induced oxidation of monoterpenes: Changes in the thermal properties of secondary organic aerosol (SOA)
- 2017
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 114, s. 31-41
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Tidskriftsartikel (refereegranskat)abstract
- The behaviour of secondary organic aerosols (SOA) in the atmosphere is highly dependent on their thermal properties. Here we investigate the volatility of SOA formed from α-pinene, β-pinene and limonene upon ozone- and OH-induced oxidation, and the effect of OH-induced ageing on the initially produced SOA. For all three terpenes, the ozone-induced SOA was less volatile than the OH-induced SOA. The thermal properties of the SOA were described using three parameters extracted from the volatility measurements: the temperature at which 50% of the volume has evaporated (TVFR0.5), which is used as a general volatility indicator; a slope factor (SVFR), which describes the volatility distribution; and TVFR0.1, which measures the volatility of the least volatile particle fraction. Limonene-derived SOA generally had higher TVFR0.5 values and shallower slopes than SOA derived from α- and β-pinene. This was especially true for the ozone-induced SOA, partially because the ozonolysis of limonene has a strong tendency to cause SOA formation and to produce extremely low volatility VOCs (ELVOCs). Ageing by OH exposure did not reduce TVFR0.5 for any of the studied terpenes but did increase the breadth of the volatility distribution by increasing the aerosols’ heterogeneity and contents of substances with different vapour pressures, also leading to increases in TVFR0.1. This stands in contrast to previously reported results from smog chamber experiments, in which TVFR0.5 always increased with ageing. These results demonstrate that there are two opposing processes that influence the evolution of SOAs’ thermal properties as they age, and that results from both flow reactors and static chambers are needed to fully understand the temporal evolution of atmospheric SOA’ thermal properties. © 2017 The Authors
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| 2. |
- Hallquist, Åsa Marita, et al.
(författare)
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On-board Measurements of Nanoparticles from a SCR-Equipped Marine Diesel Engine
- 2013
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Ingår i: Environmental Science & Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 47:2, s. 773-780
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Tidskriftsartikel (refereegranskat)abstract
- In this study nanoparticle emissions have been characterised on-board a ship with focus on number, size and volatility. Measurements were conducted on one of the ship’s four main 12 600 kW medium–speed diesel engines which use low sulphur marine residual fuel and have a Selective Catalytic Reduction (SCR) system for NOX abatement. The particles were measured after the SCR with an engine exhaust particle sizer spectrometer (EEPS), giving particle number and mass distributions in the size range of 5.6-560 nm. The thermal characteristics of the particles were analysed using a volatility tandem DMA system (VTDMA). A dilution ratio of 450-520 was used which is similar to the initial real-world dilution. At a stable engine load of 75% of the maximum rated power, and after dilution and cooling of the exhaust gas, there was a bimodal number size distribution, with a major peak at ~10 nm and a smaller peak at around 30-40 nm. The mass distribution peaked around 20 nm and at 50-60 nm. The emission factor for particle number, EFPN, for an engine load of 75% in the open-sea was found to be 10.4 ± 1.6 × 1016 (kg fuel)-1 and about 50% of the particles by number were found to have a non-volatile core at 250 °C. Additionally, 20 nm particles consist of ~40% of non-volatile material by volume (evaporative temperature 250 °C) while the particles with a particle diameter <10 nm evaporate completely at a temperature of 130-150 °C. Emission factors for NOX, CO and CO2 for an engine load of 75% in the open-sea were determined to 4.06 ± 0.3 g (kg fuel)-1, 2.15 ± 0.06 g (kg fuel)-1 and 3.23 ± 0.08 kg (kg fuel)-1, respectively. This work contributes to an improved understanding of particle emissions from shipping using modern pollution reduction measures such as SCR and fuel with low sulphur content.
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| 3. |
- Hallquist, Åsa M., et al.
(författare)
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Particle and gaseous emissions from individual diesel and CNG buses
- 2013
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 13:10, s. 5337-5350
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Tidskriftsartikel (refereegranskat)abstract
- In this study size-resolved particle and gaseous emissions from 28 individual diesel-fuelled and 7 compressed natural gas (CNG)-fuelled buses, selected from an in-use bus fleet, were characterised for real-world dilution scenarios. The method used was based on using CO2 as a tracer of exhaust gas dilution. The particles were sampled by using an extractive sampling method and analysed with high time resolution instrumentation EEPS (10 Hz) and CO2 with a non-dispersive infrared gas analyser (LI-840, LI-COR Inc. 1 Hz). The gaseous constituents (CO, HC and NO) were measured by using a remote sensing device (AccuScan RSD 3000, Environmental System Products Inc.). Nitrogen oxides, NOx, were estimated from NO by using default NO2/NOx ratios from the road vehicle emission model HBEFA3.1. The buses studied were diesel-fuelled Euro III–V and CNG-fuelled Enhanced Environmentally Friendly Vehicles (EEVs) with different after-treatment, including selective catalytic reduction (SCR), exhaust gas recirculation (EGR) and with and without diesel particulate filter (DPF). The primary driving mode applied in this study was accelerating mode. However, regarding the particle emissions also a constant speed mode was analysed. The investigated CNG buses emitted on average a higher number of particles but less mass compared to the diesel-fuelled buses. Emission factors for number of particles (EFPN) were EFPN, DPF = 4.4 ± 3.5 × 1014, EFPN, no DPF = 2.1 ± 1.0 × 1015 and EFPN, CNG = 7.8 ± 5.7 ×1015 kg fuel−1. In the accelerating mode, size-resolved emission factors (EFs) showed unimodal number size distributions with peak diameters of 70–90 nm and 10 nm for diesel and CNG buses, respectively. For the constant speed mode, bimodal average number size distributions were obtained for the diesel buses with peak modes of ~10 nm and ~60 nm. Emission factors for NOx expressed as NO2 equivalents for the diesel buses were on average 27 ± 7 g (kg fuel)−1 and for the CNG buses 41 ± 26 g (kg fuel)−1. An anti-relationship between EFNOx and EFPM was observed especially for buses with no DPF, and there was a positive relationship between EFPM and EFCO.
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| 4. |
- Jonsson, Åsa M., 1976, et al.
(författare)
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Size‐resolved particle emission factors for individual ships
- 2011
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- In these experiments size‐resolved emission factors for particle number (EFPN) and mass (EFPM) have been determined for 734 individual ship passages for real‐world dilution. The method used is an extractive sampling method of the passing ship plumes where particle number/mass and CO2 were measured with high time resolution (1 Hz). The measurements were conducted on a small island located in the entrance to the port of Gothenburg (N57.6849, E11.838), the largest harbor in Scandinavia. This is an emission control area (ECA) and in close vicinity to populated areas. The average EFPN and EFPM were 2.55 ± 0.11 × 1016 (kg fuel)−1 and 2050 ± 110 mg (kg fuel)−1, respectively. The determined EF for ships with multiple passages showed a great reproducibility. Size‐resolved EFPN were peaking at small particle sizes ∼35 nm. Smaller particle sizes and hence less mass were observed by a gas turbine equipped ship compared to diesel engine equipped ships. On average 36 to 46% of the emitted particles by number were non‐volatile and 24% by mass (EFPN 1.16 ± 0.19 × 1016 [kg fuel]−1 and EFPM 488 ± 73 mg [kg fuel]−1, respectively). This study shows a great potential to gain large data‐sets regarding ship emission determining parameters that can improve current dispersion modeling for health assessments on local and regional scales. The global contributions of total and non‐volatile particle mass from shipping using this extensive data‐set from an ECA were estimated to be at least 0.80 Tgy−1 and 0.19 Tgy−1.
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| 5. |
- Salo, Kent, 1967, et al.
(författare)
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Thermal characterization of aminium nitrate nanoparticles.
- 2011
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Ingår i: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1520-5215 .- 1089-5639. ; 115:42, s. 11671-7
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Tidskriftsartikel (refereegranskat)abstract
- Amines are widely used and originate from both anthropogenic and natural sources. Recently, there is, in addition, a raised concern about emissions of small amines formed as degradation products of the more complex amines used in CO(2) capture and storage systems. Amines are bases and can readily contribute to aerosol mass and number concentration via acid-base reactions but are also subject to gas phase oxidation forming secondary organic aerosols. To provide more insight into the atmospheric fate of the amines, this paper addresses the volatility properties of aminium nitrates suggested to be produced in the atmosphere from acid-base reactions of amines with nitric acid. The enthalpy of vaporization has been determined for the aminium nitrates of mono-, di-, trimethylamine, ethylamine, and monoethanolamine. The enthalpy of vaporization was determined from volatility measurements of laboratory generated aerosol nanoparticles using a volatility tandem differential mobility analyzer set up. The determined enthalpy of vaporization for aminium nitrates range from 54 up to 74 kJ mol(-1), and the calculated vapor pressures at 298 K are around 10(-4) Pa. These values indicate that aminium nitrates can take part in gas-to-particle partitioning at ambient conditions and have the potential to nucleate under high NO(x) conditions, e.g., in combustion plumes.
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| 6. |
- Westerlund, Jonathan, 1983, et al.
(författare)
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Characterization of fleet emissions from ships through multi-individual determination of size-resolved particle emissions in a coastal area
- 2015
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 112, s. 159-166
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Tidskriftsartikel (refereegranskat)abstract
- Shipping is becoming a major source of particulate air pollution in coastal cities. Here we describe the use of a stationary measurement site to characterize nanoparticle emissions (5.6-560 nm) from a large ship fleet (154 ships) in a harbor region of an emission control area (ECA) under real-world dilution conditions. Emission factors (EFs) are described with respect to particle number (PN), mass (PM), size and volatility. Automatic Identification System data were used to obtain information on ship class, direction, speed and acceleration. Cargo and passenger ships had similar average EFs: 2.79 +/- 0.19 vs. 2.35 +/- 0.20 x 10(16) # (kg fuel)(-1) and 2550 +/- 170 vs. 2200 +/- 130 mg (kg fuel)(-1) respectively. The number size distributions for cargo and passenger ships were unimodal, peaking at similar to 40 nm. Tug-boats and pilots emitted smaller particles with lower EFPN and EFPM. For emissions of non-volatile particles from cargo and passenger ships EFPM increased with decreasing speed and acceleration while the EFPN decreased. The size distributions of the non-volatile particles for all ships contained a large mode at similar to 10 nm. This peak is believed to be formed during plume aging. A detailed understanding of size-resolved particle emissions from individual ships will be important in designing appropriate emission regulations for coastal areas. (C) 2015 Elsevier Ltd. All rights reserved.
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