| 1. |
- Nosko, Oleksii, 1983-, et al.
(författare)
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Effective density of airborne wear particles from car brake materials
- 2017
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Ingår i: Journal of Aerosol Science. - : Elsevier. - 0021-8502 .- 1879-1964. ; 107, s. 94-106
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Tidskriftsartikel (refereegranskat)abstract
- People living in urban environments are subject to high health risks due to various anthropogenicsources of airborne particulate matter, including wear of transport vehicle brakes. Studies ofairborne particles often require an estimate of the effective particle density, a property thatallows correct matching of mass and size characteristics measured by different aerosolinstruments. In this study we investigated the effective density of airborne wear particles emittedfrom car brake materials. The particles were generated by a pin-on-disc machine located in asealed chamber. Two methods were used to determine the effective density. The first method isbased on measurements of PM10 and particle size distribution. The second method involvesmeasurements and subsequent fitting of the mobility size distribution and aerodynamic sizedistribution. Results from the two methods showed good agreement. It was found that theeffective density is 0.75±0.2 g/cm3. The particle emission, size distribution and effectivedensity are sensitive to temperature variations. An intensive emission of ultrafine particles isinitiated at the disc temperature of 185±16 °C. The effective density decreases with thetemperature in the interval 110–360 °C. There is a large difference between the effective densityand the density of the particle material, which suggests that the particles are porous.
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| 2. |
- Nosko, Oleksii, et al.
(författare)
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Porosity and shape of airborne wear microparticles generated by sliding contact between a low-metallic friction material and a cast iron
- 2017
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Ingår i: Journal of Aerosol Science. - : Elsevier. - 0021-8502 .- 1879-1964. ; 113, s. 130-140
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Tidskriftsartikel (refereegranskat)abstract
- The wear of brakes in transport vehicles is one of the main anthropogenic sources of airborne particulate matter in urban environments. The present study deals with the characterisation of airborne wear microparticles from a low-metallic friction material / cast iron pair used in car brakes. Particles were generated by a pin-on-disc machine in a sealed chamber at sliding velocity of 1.3 m/s and contact pressure of 1.5 MPa. They were collected on filters in an electrical low pressure impactor, and an investigation was conducted to quantify their shape and porosity. Scanning electron microscopy revealed that most of the 0.1−0.9 µm particles are flakes and have a breadth-to-length aspect ratio of 0.7 ± 0.2. Particle porosity was determined by milling particles with a focused ion beam and subsequent analysis of the exposed particle cross-sections. Most of the 0.3–6.2 µm particles were revealed to have porosity of 9 ± 6%. Analysis of the relationship between effective particle density, particle material density, dynamic shape factor and porosity showed that the shape factor has a stronger influence on the effective density of airborne wear particles than the porosity factor. The obtained results are useful for accurate prediction of particle behaviour in the atmosphere and in the human respiratory system.
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| 3. |
- Shaltout, Abdallah, et al.
(författare)
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Spectroscopic investigation of PM2.5 collected at industrial, residential and traffic sites in Taif, Saudi Arabia
- 2015
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 79, s. 97-108
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Tidskriftsartikel (refereegranskat)abstract
- The present work aims at detecting and characterizing the semiquione free radicals and inorganic composition of atmospheric aerosol particles, PM2.5, collected at three different sites (industrial, residential, and traffic dominated) in Taif city, Saudi Arabia, during 2011/2012. PM2.5 particles have been collected on polycarbonate filters in a collection cartridge in a cyclone. The duration of the collection was 24 h at an air flow of 3 L min−1. The average PM2.5 mass concentration was 37±22 μg/m3, 57±22 μg/m3 and 50±31 μg/m3 at the residential, industrial and traffic sites, respectively. These values are higher than the target value for air quality standards of European Union (25 μg/m3). Energy dispersive X-ray fluorescence (EDXRF) and electron paramagnetic resonance (EPR) spectroscopic techniques were chosen for sample analysis. Fourteen elements were quantified by EDXRF: Si, S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Rb, Sr and Pb. The measured concentrations of the potentially hazardous trace elements As, Cu, Sb, Cr, Mn, Ni and Pb were either below the detection limit or below the limits defined by international guidelines and national standards of ambient air quality. Furthermore, electron paramagnetic resonance (EPR) technique was used for testing and identifying paramagnetic species in the PM2.5 particles. The EPR spectra of PM2.5 from the three sites have a g-value in the range from 2.0033 to 2.235 which is characteristic for semiquinone radicals. The PM2.5 samples showed three EPR signals indicate the presence of semiquinone radical anion.
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| 4. |
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| 5. |
- Svensson, Christian, et al.
(författare)
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Characteristics of airborne gold aggregates generated by spark discharge and high temperature evaporation furnace: Mass-mobility relationship and surface area
- 2015
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 87, s. 38-52
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Tidskriftsartikel (refereegranskat)abstract
- The properties of gas-borne aggregates are important in nano-technology and for potential health effects. Gold aggregates from three generators (one commercial and one custom built spark discharge generator and one high-temperature furnace) have been characterized. The aggregate surface areas were determined using five approaches - based on aggregation theory and/or measured aggregate properties. The characterization included mass-mobility relationships, effective densities (assessed by an Aerosol Particles Mass analyzer), primary particle analysis (based on Transmission Electron Microscopy), as well as total mass and number concentration outputs. The relationships between mass and mobility are well described by power-law functions with exponents of 2.18-2.35. For all generators, the primary particles of the aggregates were fused together by a bridge with a diameter typically similar to 60-70% of the primary particle diameter (5-10 nm). The total mass outputs were 6.1-48.1 mg/m3 and the predicted surface area outputs in the range 0.9 x 10(-3)-17 x 10(-3) cm(2)/cm(3). The aggregate effective densities differed considerably between generators. The difference could partly be explained by the differences in primary particle diameter, but not fully. This in turn may be explained either by a varying primary particle size with aggregate size, or by that there are slight differences in the morphology of the aggregates from the generators. (C) 2015 The Authors. Published by Elsevier Ltd.
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| 6. |
- 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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