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Träfflista för sökning "WFRF:(Swietlicki Erik) srt2:(2000-2004)"

Sökning: WFRF:(Swietlicki Erik) > (2000-2004)

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  • Gidhagen, L, et al. (författare)
  • Model simulation of ultrafine particles inside a road tunnel
  • 2003
  • Ingår i: Atmospheric Environment. - 1352-2310. ; 37:15, s. 2023-2036
  • Tidskriftsartikel (refereegranskat)abstract
    • A monodispersive aerosol dynamic model, coupled to a 3D hydrodynamical grid model, has been used to study the dynamics of ultrafine particles inside a road tunnel in Stockholm, Sweden. The model results were compared to measured data of particle number concentrations, traffic intensity and tunnel ventilation rate. Coagulation and depositional losses to the tunnel walls were shown to be important processes during traffic peak hours, together contributing to losses of 77% of the particles smaller than 10nm and 41% of the particles of size 10-29nm. Particle growth due to water uptake or the presence of a micron-sized, resuspended particle fraction did not have any significant effect on the number of particles lost due to coagulation. Model simulation of particle number concentration response to temporal variations in traffic flow showed that constant emission factors could be used to reproduce the concentration variations of the particles larger than 29nm, while vehicle-speed-dependent factors are suggested to reproduce the variation of the smallest fractions. The emission factors for particle number concentrations estimated from the model simulation are in general higher and show a larger contribution from light-duty vehicles than what has been reported from a tunnel in California. The model study shows that combined measurements and model simulations in road tunnels can be used to improve the determinations of vehicle emission factors for ultrafine particles under realistic driving conditions. (C) 2003 Elsevier Science Ltd. All rights reserved.
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  • Hedberg, E, et al. (författare)
  • Chemical and physical characterization of emissions from birch wood combustion in a wood stove
  • 2002
  • Ingår i: Atmospheric Environment. - 1352-2310. ; 36:30, s. 4823-4837
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of this study was to characterize the emissions of a large number of chemical compounds emitted from birch wood combustion in a wood stove. Birch wood is widely used as fuel in Swedish household appliances. The fuel load was held constant during six experiments. Particles < 2.5 mum diameter were collected and the size distribution of the particles was measured. The results were compared to the size distribution in road traffic emissions. It could be seen that the number distribution differed between the sources. In traffic exhaust, the number of particles maximized at 20 nm, while the number distribution from wood burning ranged from 20 to 300 nm. The ratio K/Ca on particles was found. to be significantly different in wood burning compared to road dust, range 30-330 for the former and 0.8+/-0.15 for the latter. The source profile of common elements emitted from wood-burning differed from that found on particles at a street-level site or in long-distance transported particles. The ratio toluene/benzene in this study was found to be in the range 0.2-0.7, which is much lower than the ratio 3.6+/-0.5 in traffic exhaust emissions. Formaldehyde and acetone were the most abundant compounds among the volatile ketones and aldehydes. The emission factor varied between 180-710mg/kg wood for formaldehyde and 5-1300mg/kg wood for acetone. Of the organic acids analyzed (3,4,5)-trimethoxy benzoic acid was the most abundant compound. Of the PAHs reported, fluorene, phenanthrene, anthracene, fluoranthene and pyrene contribute to more than 70% of the mass of PAH. Of the elements analyzed, K and Si were the most abundant elements, having emission factors of 27 and 9mg/kg wood, respectively. Although fluoranthene has a toxic equivalence factor of 5% of benzo(a)pyrene (B(a)P), it can be seen that the toxic potency of fluoranthene in wood burning emissions is of the same size as B(a)P. This indicates that the relative carcinogenic potency contribution of fluoranthene in wood smoke would be about 40% of B(a)P. (C) 2002 Elsevier Science Ltd. All rights reserved.
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  • Ketzel, M, et al. (författare)
  • Particle size distribution and particle mass measurements at urban, near-city and rural level in the Copenhagen area and Southern Sweden
  • 2004
  • Ingår i: Atmospheric Chemistry and Physics. - 1680-7324. ; 4, s. 281-292
  • Tidskriftsartikel (refereegranskat)abstract
    • Particle size distribution (size-range 3-900 nm) and PM10 was measured simultaneously at an urban background station in Copenhagen, a near-city background and a rural location during a period in September-November 2002. The study investigates the contribution from urban versus regional sources of particle number and mass concentration. The total particle number (ToN) and NOx are well correlated at the urban and near-city level and show a distinct diurnal variation, indicating the common traffic source. The average ToN at the three stations differs by a factor of 3. The observed concentrations are 2500# cm(-3), 4500# cm(-3) and 7700# cm(-3) at rural, near-city and urban level, respectively. PM10 and total particle volume (ToV) are well correlated between the three different stations and show similar concentration levels, in average within 30% relative difference, indicating a common source from long-range transport that dominates the concentrations at all locations. Measures to reduce the local urban emissions of NOx and ToN are likely to affect both the street level and urban background concentrations, while for PM10 and ToV only measurable effects at the street level are probable. Taking into account the supposed stronger health effects of ultrafine particles reduction measures should address particle number emissions. The traffic source contributes strongest in the 10-200 nm particle size range. The maximum of the size distribution shifts from about 20-30 nm at kerbside to 50-60 nm at rural level. Particle formation events were observed in the 3-20 nm size range at rural location in the afternoon hours, mainly under conditions with low concentrations of preexisting aerosol particles. The maximum in the size distribution of the "traffic contribution" seems to be shifted to about 28 nm in the urban location compared to 22 nm at kerbside. Assuming NOx as an inert tracer on urban scale allows to estimate that ToN at urban level is reduced by 15-30% compared to kerbside. Particle removal processes, e. g. deposition and coagulation, which are most efficient for smallest particle sizes (<20 nm) and condensational growth are likely mechanisms for the loss of particle number and the shift in particle size.
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  • Kristensson, Adam, et al. (författare)
  • Real-world traffic emission factors of gases and particles measured in a road tunnel in Stockholm, Sweden
  • 2004
  • Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:5, s. 657-673
  • Tidskriftsartikel (refereegranskat)abstract
    • Measurements in a road tunnel in Stockholm, Sweden give the real-world traffic emission factors for a number of gaseous and particle pollutants. These include 49 different polycyclic aromatic hydrocarbons (PAH), CO, NOX, benzene, toluene, xylenes, aldehydes, elements and inorganic/organic carbon contained in particles, the sub-micrometer aerosol number size distribution, PM2.5 and PM10. The exhaust pipe emission factors are divided with the help of automated traffic counts into the two pollutant sources, the heavy-duty vehicles (HDV) and light-duty vehicles (LDV). The LDV fleet contains 95% petrol cars and the total fleet contains about 5% HDV. When data permitted, the emission factors were further calculated at different vehicle speeds. The current work shows that average CO, NOX and benzene emission factors amounted to 5.3, 1.4 and 0.017 g veh(-1) km(-1), respectively. Since the mid-90s CO and benzene decreased by about 15%, carbonyls by about a factor 2, whereas NOX did not change much. PAR emission factors were 2-15 times higher than found during dynamometer tests. Most particles are distributed around 20 nm diameter and the LDV fleet contributes to about 65% of both PM and particle number. In general, the gaseous emissions are higher in Sweden than in USA and Switzerland, foremost due to the lower fraction catalytic converters in Sweden. The PM and number emissions of particles are also slightly higher in the Swedish tunnel. (C) 2003 Elsevier Ltd. All rights reserved.
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9.
  • Leck, C, et al. (författare)
  • Can Marine Micro-organisms Influence Melting of the Arctic Pack Ice?
  • 2004
  • Ingår i: EOS, TRANSACTIONS AMERICAN GEOPHYSICAL UNION. ; 85:3, s. 25-25
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic Ocean Expedition of 2001 (AOE-2001) to the central Arctic mostly north of latitude 85°N was conducted to study marine life forms and their products in water and ice, how their products may get into the air, the evolution of the particles produced, and their growth up to sizes large enough for activation into clouds. The expedition also investigated whether these naturally generated particles and clouds constitute a positive or negative climate feedback upon temperature forcing, as schematically shown in Figure 1. Indeed, biological activity of the open lead surface micro-layer was found to strongly influence particle production over the pack ice region, and this would influence cloud properties there. Similar processes transferring particulates from the surface micro-layer to the air—bubble bursting—should be operative over the world's oceans. So, can marine micro-organisms influence the melting of the Arctic pack ice? The answer must be yes, but to determine whether that influence is significant or not, we have to contend with many unknown factors. For example, will biological activity and airborne particle production increase or decrease with melting of the pack ice, and will resultant changes in warmer oceans oppose or reinforce the Arctic changes? Will cloud cover and the feeble mixing between surface and higher air remain unchanged? To have identified a possible influence on climate change is important, but assessing the extent of that influence will be a far harder problem.
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  • Lillieblad, Lena, et al. (författare)
  • Boiler operation influence on the emissions of submicrometer-sized particles and polycyclic aromatic hydrocarbons from biomass-fired grate boilers
  • 2004
  • Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 18:2, s. 410-417
  • Tidskriftsartikel (refereegranskat)abstract
    • The emissions of particles, and gaseous compounds, into the ambient air from biomass-fired moving grate boilers were characterized under different boiler operation conditions. The boilers had a thermal capacity of similar to1 MW. The flue gas cleaning systems consisted of multicyclones for the removal of coarse particles. Dry wood fuel that consisted of shavings, wood chips, and sawdust from a local wood industry and wood pellets were fired at two plants. The influence of boiler load on the emissions was characterized. An electrical low-pressure impactor (ELPI) was used to determine the particle number concentration with high time resolution. A low-pressure cascade impactor (LPI) was utilized for the mass size distribution and the size-differentiated chemical composition. Elemental analysis of the fly ash collected on impactor substrates was made by particle-induced X-ray emission (PIXE) analysis. The concentration of elemental carbon under different load conditions was also measured. In addition, emissions of polycyclic aromatic hydrocarbons (PAHs) from the boiler that was operating on dry wood fuel were compared with PAH emissions from two different biomass-fired boilers (one was operating on forest residues and the other on pellets). The boiler load had little influence on the particle mass concentration of submicrometer-sized particles, which was in the range of 50-75 mg/m(3) (0 degreesC, 101.3 kPa, dry gas, 13% CO2). The total particle number concentration increased and the particle size decreased as the boiler load increased. The elemental analysis revealed that potassium and sulfur were the dominating components in the submicrometer size range, whereas potassium and calcium were major components in the coarse fraction. The PAH emissions between the three boilers varied by almost 3 orders of magnitude.
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