| 1. |
- Ahlberg, Erik, et al.
(författare)
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Measurement report : Black carbon properties and concentrations in southern Sweden urban and rural air-the importance of long-range transport
- 2023
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 23:5, s. 3051-3064
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Tidskriftsartikel (refereegranskat)abstract
- Soot, or black carbon (BC), aerosol is a major climate forcer with severe health effects. The impacts depend strongly on particle number concentration, size and mixing state. This work reports on two field campaigns at nearby urban and rural sites, 65gkm apart, in southern Sweden during late summer 2018. BC was measured using a single-particle soot photometer (SP2) and Aethalometers (AE33). Differences in BC concentrations between the sites are driven primarily by local traffic emissions. Equivalent and refractory BC mass concentrations at the urban site were on average a factor 2.2 and 2.5, with peaks during rush hour up to a factor g1/44, higher than the rural background levels. The number fraction of particles containing a soot core was significantly higher in the city. BC particles at the urban site were on average smaller by mass and had less coating owing to fresh traffic emissions. The organic components of the fresh traffic plumes were similar in mass spectral signature to hydrocarbon-like organic aerosol (HOA), commonly associated with traffic. Despite the intense local traffic (g1/4g30g000 vehicles passing per day), PM1, including organic aerosol, was dominated by aged continental air masses even at the curbside site. The fraction of thickly coated particles at the urban site was highly correlated with the mass concentrations of all measured chemical species of PM1, consistent with aged, internally mixed aerosol. Trajectory analysis for the whole year showed that air masses arriving at the rural site from eastern Europe contained approximately double the amount of BC compared to air masses from western Europe. Furthermore, the largest regional emissions of BC transported to the rural site, from the Malmö-Copenhagen urban area, are discernible above background levels only when precipitation events are excluded. We show that continental Europe and not the Malmö-Copenhagen region is the major contributor to the background BC mass concentrations in southern Sweden.
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| 2. |
- Ahlberg, Erik, et al.
(författare)
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No particle mass enhancement from induced atmospheric ageing at a rural site in northern Europe
- 2019
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- A large portion of atmospheric aerosol particles consists of secondary material produced by oxidation reactions. The relative importance of secondary organic aerosol (SOA) can increase with improved emission regulations. A relatively simple way to study potential particle formation in the atmosphere is by using oxidation flow reactors (OFRs) which simulate atmospheric ageing. Here we report on the first ambient OFR ageing experiment in Europe, coupled with scanning mobility particle sizer (SMPS), aerosol mass spectrometer (AMS) and proton transfer reaction (PTR)-MS measurements. We found that the simulated ageing did not produce any measurable increases in particle mass or number concentrations during the two months of the campaign due to low concentrations of precursors. Losses in the reactor increased with hydroxyl radical (OH) exposure and with increasing difference between ambient and reactor temperatures, indicating fragmentation and evaporation of semivolatile material.
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| 3. |
- Ahlberg, Erik, et al.
(författare)
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Secondary organic aerosol from VOC mixtures in an oxidation flow reactor
- 2017
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 161, s. 210-220
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Tidskriftsartikel (refereegranskat)abstract
- The atmospheric organic aerosol is a tremendously complex system in terms of chemical content. Models generally treat the mixtures as ideal, something which has been questioned owing to model-measurement discrepancies. We used an oxidation flow reactor to produce secondary organic aerosol (SOA) mixtures containing oxidation products of biogenic (α-pinene, myrcene and isoprene) and anthropogenic (m-xylene) volatile organic compounds (VOCs). The resulting volume concentration and chemical composition was measured using a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), respectively. The SOA mass yield of the mixtures was compared to a partitioning model constructed from single VOC experiments. The single VOC SOA mass yields with no wall-loss correction applied are comparable to previous experiments. In the mixtures containing myrcene a higher yield than expected was produced. We attribute this to an increased condensation sink, arising from myrcene producing a significantly higher number of nucleation particles compared to the other precursors. Isoprene did not produce much mass in single VOC experiments but contributed to the mass of the mixtures. The effect of high concentrations of isoprene on the OH exposure was found to be small, even at OH reactivities that previously have been reported to significantly suppress OH exposures in oxidation flow reactors. Furthermore, isoprene shifted the particle size distribution of mixtures towards larger sizes, which could be due to a change in oxidant dynamics inside the reactor.
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| 4. |
- Ahlberg, Erik, et al.
(författare)
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"Vi klimatforskare stödjer Greta och skolungdomarna"
- 2019
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Ingår i: Dagens nyheter (DN debatt). - 1101-2447.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
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| 5. |
- Appavoo, Danielle, et al.
(författare)
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New method to quantify contribution to aerosol particles from new particle formation : Comparison with traditional method at Vavihill background field station in Sweden
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Aerosol particles exist in the atmosphere in large concentrations and have significant global climate effects. New particle formation is an aerosol particle source and, to date, its contribution to the total aerosol concentration in the atmosphere is not fully understood. This study focuses on the extension of new particle formation events that begin in Lille Valby, Denmark and travel over 70 km to Vavihill, Sweden. Data over a five year period (2005, 2006, 2008, 2009 and 2010) was analyzed. Dates selected for analysis had to have a new particle formation event in Lille Valby and be either undefined, have an unclear event, or have a non-event in Vavihill as defined by traditional methods from Dal Maso et al. (2005). The growth rate, particle size distributions, and wind trajectories at the time of the event were considered when analyzing each event case. 7 out of 1480 days met all of the criteria to be classified as new particle formation extended from Lille Valby. If the result is extrapolated to all wind directions and sources, it is likely that a much higher percentage of the days would meet the criteria. The average percentage of particles in Vavihill that can be attributed to new particle formation from Lille Valby on reclassified days at event times over the five year period considered is 64.18%.
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| 6. |
- Asmi, A., et al.
(författare)
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Aerosol decadal trends - Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations
- 2013
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 13:2, s. 895-916
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Tidskriftsartikel (refereegranskat)abstract
- We have analysed the trends of total aerosol particle number concentrations (N) measured at long-term measurement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarctica, and on Pacific Ocean islands. The majority of the sites showed clear decreasing trends both in the full-length time series, and in the intra-site comparison period of 2001-2010, especially during the winter months. Several potential driving processes for the observed trends were studied, and even though there are some similarities between N trends and air temperature changes, the most likely cause of many northern hemisphere trends was found to be decreases in the anthropogenic emissions of primary particles, SO2 or some co-emitted species. We could not find a consistent agreement between the trends of N and particle optical properties in the few stations with long time series of all of these properties. The trends of N and the proxies for cloud condensation nuclei (CCN) were generally consistent in the few European stations where the measurements were available. This work provides a useful comparison analysis for modelling studies of trends in aerosol number concentrations.
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| 7. |
- Asmi, A., et al.
(författare)
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Number size distributions and seasonality of submicron particles in = rope 2008-2009
- 2011
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:11, s. 5505-5538
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Tidskriftsartikel (refereegranskat)abstract
- Two years of harmonized aerosol number size distribution data from 24 = ropean field monitoring sites have been analysed. The results give a = mprehensive overview of the European near surface aerosol particle = mber concentrations and number size distributions between 30 and 500 = of dry particle diameter. Spatial and temporal distribution of = rosols in the particle sizes most important for climate applications = e presented. We also analyse the annual, weekly and diurnal cycles of = e aerosol number concentrations, provide log-normal fitting parameters = r median number size distributions, and give guidance notes for data = ers. Emphasis is placed on the usability of results within the aerosol = delling community.
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| 8. |
- Ausmeel, Stina, et al.
(författare)
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Methods for identifying aged ship plumes and estimating contribution to aerosol exposure downwind of shipping lanes
- 2019
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 12:8, s. 4479-4493
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Tidskriftsartikel (refereegranskat)abstract
- Ship traffic is a major source of aerosol particles, particularly near shipping lanes and harbours. In order to estimate the contribution to exposure downwind of a shipping lane, it is important to be able to measure the ship emission contribution at various distances from the source. We report on measurements of atmospheric particles 7-20 km downwind of a shipping lane in the Baltic Sea Sulfur Emission Control Area (SECA) at a coastal location in southern Sweden during a winter and a summer campaign. Each ship plume was linked to individual ship passages using a novel method based on wind field data and automatic ship identification system data (AIS), where varying wind speeds and directions were applied to calculate a plume trajectory. In a situation where AIS data are not matching measured plumes well or if AIS data are missing, we provide an alternative method with particle number concentration data. The shipping lane contribution to the particle number concentration in Falsterbo was estimated by subtracting background concentrations from the ship plume concentrations, and more than 150 plumes were analysed. We have also extrapolated the contribution to seasonal averages and provide recommendations for future similar measurements. Averaged over a season, the contribution to particle number concentration was about 18 % during the winter and 10 % during the summer, including those periods with wind directions when the shipping lane was not affecting the station. The corresponding contribution to equivalent black carbon was 1.4 %..
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| 9. |
- Ausmeel, Stina, et al.
(författare)
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Ship plumes in the Baltic Sea Sulfur Emission Control Area: chemical characterization and contribution to coastal aerosol concentrations
- 2020
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 20:15, s. 9135-9151
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Tidskriftsartikel (refereegranskat)abstract
- In coastal areas, there is increased concern aboutemissions from shipping activities and the associated impacton air quality. We have assessed the ship aerosol propertiesand the contribution to coastal particulate matter (PM) andnitrogen dioxide (NO2) levels by measuring ship plumes inambient conditions at a site in southern Sweden, within a SulfurEmission Control Area. Measurements took place duringa summer and a winter campaign, 10 km downwind ofa major shipping lane. Individual ships showed large variabilityin contribution to total particle mass, organics, sulfate,and NO2. The average emission contribution of theshipping lane was 2913 and 3720 ngm?3 to PM0:5,188 and 3419 ngm?3 to PM0:15, and 1:210:57 and1:110:61 μgm?3 to NO2, during winter and summer, respectively.Sulfate and organics dominated the particle massand most plumes contained undetectable amounts of equivalentblack carbon (eBC). The average eBC contribution was3:51:7 ngm?3 and the absorption Ångström exponent wasclose to 1. Simulated ageing of the ship aerosols using anoxidation flow reactor showed that on a few occasions, therewas an increase in sulfate and organic mass after photochemicalprocessing of the plumes. However, most plumes did notproduce measurable amounts of secondary PM upon simulatedageing.
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| 10. |
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| 11. |
- Böö, Sebastian, 1979-
(författare)
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Transport of mineral dust into the Arctic : Evaluation of two reanalysis datasets of atmospheric composition
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main purpose of this thesis is to examine the mineral dust aerosol transport into the Arctic. Two three-dimensional reanalysis datasets of atmospheric composition, the Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA) and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), are analyzed with regard to dust transport into the Arctic. The reanalyses agree on that the largest mass transport of dust into the Arctic occurs across western Russia during spring and early summer, although large dust transport events can occur across other geographical areas during all seasons. In several aspects, the reanalyses show substantial differences. The transport in CAMSRA is considerably smaller, more concentrated and occurs at lower altitudes. Furthermore, the transport in CAMSRA is to a larger extent than MERRA-2 driven by well-defined events of dust transport in space and time.The reanalysis data are compared with surface measurements of dust in the Arctic and dust extinction satellite retrievals from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The comparison indicates that CAMSRA underestimates the dust transport into the Arctic and that MERRA- 2 likely overestimates it. The discrepancy between CAMSRA and MERRA-2 can in part be explained by the assimilation process where too little dust is assimilated in CAMSRA while MERRA-2 overestimates the production of light particles, causing an excessive transport, and the assimilation process further increases the dust concentration in remote areas. Despite the clear differences between the reanalyses, this study provides new insights into the spatio-temporal distribution of the dust transport into the Arctic and the transported mass is estimated to be within the range 1.5–31 Tg yr-1.The thesis also briefly examines the aerosol transport of all five aerosol species carried by the reanalyses, that in addition to dust are black carbon, organic matter, sea-salt and sulfate. The annual aerosol mass transport to the Arctic in CAMSRA and MERRA-2 are 24 Tg and 50 Tg respectively. The reanalyses show substantial differences regarding the proportions of the different aerosol types — emphasizing that it is crucial that the aerosol module manages to simulate the correct aerosol mass fractions, as the assimilation of AOD alone cannot change the proportions between the aerosols.
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| 12. |
- Fors, Erik, et al.
(författare)
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Hygroscopic properties of the ambient aerosol in southern Sweden - a two year study
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 11:16, s. 8343-8361
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Tidskriftsartikel (refereegranskat)abstract
- The hygroscopic growth of the atmospheric aerosol is a critical parameter for quantifying the anthropogenic radiative forcing. Until now, there has been a lack of long term measurements due to limitations in instrumental techniques. In this work, for the first time the seasonal variation of the hygroscopic properties of a continental background aerosol has been described, based on more than two years of continuous measurements. In addition to this, the diurnal variation of the hygroscopic growth has been investigated, as well as the seasonal variation in CCN concentration. These physical properties of the aerosol have been measured with a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA), a Differential Mobility Particle Sizer (DMPS), and a Cloud Condensation Nuclei Counter (CCNC). The results show that smaller particles are generally less hygroscopic than larger ones, and that there is a clear difference in the hygroscopic properties between the Aitken and the accumulation mode. A seasonal cycle was found for all particle sizes. In general, the average hygroscopic growth is lower during wintertime, due to an increase in the relative abundance of less hygroscopic or barely hygroscopic particles. Monthly averages showed that the hygroscopic growth factors of the two dominating hygroscopic modes (one barely hygroscopic and one more hygroscopic) were relatively stable. The hygroscopic growth additionally showed a diurnal cycle, with higher growth factors during day time. CCN predictions based on H-TDMA data underpredicted the activated CCN number concentration with 7% for a 1% water supersaturation ratio. The underprediction increases with decreasing s, most likely due to a combination of measurement and modeling uncertainties. It was found that although the aerosol is often externally mixed, recalculating to an internal mixture with respect to hygroscopicity did not change the CCN concentration as a function of supersaturation significantly.
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| 13. |
- Gidhagen, L, et al.
(författare)
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Model simulation of ultrafine particles inside a road tunnel
- 2003
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Ingår i: Atmospheric Environment. - 1352-2310. ; 37:15, s. 2023-2036
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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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| 14. |
- Hamburger, T., et al.
(författare)
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Overview of the synoptic and pollution situation over Europe during the EUCAARI-LONGREX field campaign
- 2011
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:3, s. 1065-1082
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Tidskriftsartikel (refereegranskat)abstract
- In May 2008 the EUCAARI-LONGREX aircraft field campaign was conducted within the EUCAARI intensive observational period. The campaign aimed at studying the distribution and evolution of air mass properties on a continental scale. Airborne aerosol and trace gas measurements were performed aboard the German DLR Falcon 20 and the British FAAM BAe-146 aircraft. This paper outlines the meteorological situation over Europe during May 2008 and the temporal and spatial evolution of predominantly anthropogenic particulate pollution inside the boundary layer and the free troposphere. Time series data of six selected ground stations are used to discuss continuous measurements besides the single flights. The observations encompass total and accumulation mode particle number concentration (0.1–0.8 μm) and black carbon mass concentration as well as several meteorological parameters. Vertical profiles of total aerosol number concentration up to 10 km are compared to vertical profiles probed during previous studies.During the first half of May 2008 an anticyclonic blocking event dominated the weather over Central Europe. It led to increased pollutant concentrations within the centre of the high pressure inside the boundary layer. Due to long-range transport the accumulated pollution was partly advected towards Western and Northern Europe. The measured aerosol number concentrations over Central Europe showed in the boundary layer high values up to 14 000 cm−3 for particles in diameter larger 10 nm and 2300 cm−3 for accumulation mode particles during the high pressure period, whereas the middle free troposphere showed rather low concentrations of particulates. Thus a strong negative gradient of aerosol concentrations between the well mixed boundary layer and the clean middle troposphere occurred.
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| 15. |
- Hedberg, E, et al.
(författare)
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Chemical and physical characterization of emissions from birch wood combustion in a wood stove
- 2002
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Ingår i: Atmospheric Environment. - 1352-2310. ; 36:30, s. 4823-4837
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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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| 16. |
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| 17. |
- Hussein, T., et al.
(författare)
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Time span and spatial scale of regional new particle formation events over Finland and Southern Sweden
- 2009
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9:14, s. 4699-4716
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the time span and spatial scale of regional new particle formation (NPF) events in Finland and Southern Sweden using measured particle number size distributions at five background stations. We define the time span of a NPF event as the time period from the first moment when the newly formed mode of aerosol particles is observable below 25 nm until the newly formed mode is not any more distinguishable from other background modes of aerosol particles after growing to bigger sizes. We identify the spatial scale of regional NPF events based on two independent approaches. The first approach is based on the observation within a network of stationary measurement stations and the second approach is based on the time span and the history of air masses back-trajectories. According to the second approach, about 60% and 28% of the events can be traced to distances longer than 220 km upwind from where the events were observed in Southern Finland (Hyytiälä) and Northern Finland (Värriö), respectively. The analysis also showed that the observed regional NPF events started over the continents but not over the Atlantic Ocean. The first approach showed that although large spatial scale NPF events are frequently observed at several locations simultaneously, they are rarely identical (similar characteristics and temporal variations) due to differences in the initial meteorological and geographical conditions between the stations. The growth of the newly formed particles during large spatial scale events can be followed for more than 30 h where the newly formed aerosol particles end up in the Aitken mode (diameter 25–100 nm) and accumulation mode size ranges (diameter 0.1–1 μm). This study showed clear evidence that regional NPF events can pose a significant source for accumulation mode particles over the Scandinavian continent provided that these findings can be generalized to many of the air masses traveling over the European continent.
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| 18. |
- Kecorius, Simonas, et al.
(författare)
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Significant increase of aerosol number concentrations in air masses crossing a densely trafficked sea area
- 2016
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Ingår i: Oceanologia. - : Elsevier BV. - 0078-3234. ; 58:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we evaluated 10 months data (September 2009 to June 2010) of atmospheric aerosol particle number size distribution at three atmospheric observation stations along the Baltic Sea coast: Vavihill (upwind, Sweden), Uto (upwind, Finland), and Preila (downwind, Lithuania). Differences in aerosol particle number size distributions between the upwind and downwind stations during situations of connected atmospheric flow, when the air passed each station, were used to assess the contribution of ship emissions to the aerosol number concentration (diameter interval 50-400 nm) in the Lithuanian background coastal environment. A clear increase in particle number concentration could be noticed, by a factor of 1.9 from Uto to Preila (the average total number concentration at Uto was 791 cm(-3)), and by a factor of 1.6 from Vavihill to Preila (the average total number concentration at Vavihill was 998 cm(-3)). The simultaneous measurements of absorption Angstrom exponents close to unity at Preila supported our conclusion that ship emissions in the Baltic Sea contributed to the increase in particle number concentration at Preila. (C) 2015 Institute of Oceanology of the Polish Academy of Sciences.
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| 19. |
- Ketzel, M, et al.
(författare)
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Particle size distribution and particle mass measurements at urban, near-city and rural level in the Copenhagen area and Southern Sweden
- 2004
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Ingår i: Atmospheric Chemistry and Physics. - 1680-7324. ; 4, s. 281-292
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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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| 20. |
- Kivekäs, Niku, et al.
(författare)
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Contribution of ship traffic to aerosol particle concentrations downwind of a major shipping lane
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:16, s. 8255-8267
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Tidskriftsartikel (refereegranskat)abstract
- Particles in the atmosphere are of concern due to their toxic properties and effects on climate. In coastal areas, ship emissions can be a significant anthropogenic source. In this study we investigated the contribution from ship emissions to the total particle number and mass concentrations at a remote location. We studied the particle number concentration (12 to 490 nm in diameter), the mass concentration (12 to 150 nm in diameter) and number and volume size distribution of aerosol particles in ship plumes for a period of 4.5 months at Hovsore, a coastal site on the western coast of Jutland in Denmark. During episodes of western winds, the site is about 50 km downwind of a major shipping lane and the plumes are approximately 1 hour old when they arrive at the site. We have used a sliding percentile-based method for separating the plumes from the measured background values and to calculate the ship plume contribution to the total particle number and PM0.15 mass concentration (mass of particles below 150 nm in diameter, converted from volume assuming sphericity) at the site. The method is not limited to particle number or volume concentration, but can also be used for different chemical species in both particle and gas phase. The total number of analyzed ship plumes was 726, covering on average 19% of the time when air masses were arriving at the site over the shipping lane. During the periods when plumes were present, the particle concentration exceeded the background values on average by 790 cm(-3) by number and 0.10 gm(-3) by mass. The corresponding daily average values were 170 cm-3 and 0.023 gm-3, respectively. This means that the ship plumes contributed between 11 and 19% to the particle number concentration and between 9 and 18% to PM0.15 during days when air was arriving over the shipping lane. The estimated annual contribution from ship plumes, where all wind directions were included, was in the range of 5-8% in particle number concentration and 4-8% in PM0.15.
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| 21. |
- Kivekäs, Niku, et al.
(författare)
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Coupling an aerosol box model with one-dimensional flow : A tool for understanding observations of new particle formation events
- 2016
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 1600-0889 .- 0280-6509. ; 68:1
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Tidskriftsartikel (refereegranskat)abstract
- Field observations of new particle formation and the subsequent particle growth are typically only possible at a fixed measurement location, and hence do not follow the temporal evolution of an air parcel in a Lagrangian sense. Standard analysis for determining formation and growth rates requires that the time-dependent formation rate and growth rate of the particles are spatially invariant; air parcel advection means that the observed temporal evolution of the particle size distribution at a fixed measurement location may not represent the true evolution if there are spatial variations in the formation and growth rates. Here we present a zerodimensional aerosol box model coupled with one-dimensional atmospheric flow to describe the impact of advection on the evolution of simulated new particle formation events. Wind speed, particle formation rates and growth rates are input parameters that can vary as a function of time and location, using wind speed to connect location to time. The output simulates measurements at a fixed location; formation and growth rates of the particle mode can then be calculated from the simulated observations at a stationary point for different scenarios and be compared with the 'true' input parameters. Hence, we can investigate how spatial variations in the formation and growth rates of new particles would appear in observations of particle number size distributions at a fixed measurement site. We show that the particle size distribution and growth rate at a fixed location is dependent on the formation and growth parameters upwind, even if local conditions do not vary. We also show that different input parameters used may result in very similar simulated measurements. Erroneous interpretation of observations in terms of particle formation and growth rates, and the time span and areal extent of new particle formation, is possible if the spatial effects are not accounted for.
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| 22. |
- Kristensson, Adam
(författare)
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Aerosol Particle Sources Affecting the Swedish Air Quality at Urban and Rural Level.
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last decades anthropogenic aerosol particles have attracted much attention due to their adverse health effects and their influence of climate change, and in Sweden, there are mainly three aerosol sources that affect the air quality; domestic wood combustion, traffic, and long distance transport, which includes new particle formation. This work concerns the characterization of these sources and an estimate of how much they contribute to the aerosol particle number (ToN) and mass concentrations (PM) in Swedish cities and at background locations. The aims have been achieved with the help of extensive measurement campaigns, characterizing emissions from the sources and with measurements and modelling at receptor points, where people are exposed to the particle pollution. The most important outcomes of these studies show that, in urban areas both traffic and domestic wood combustion are very important sources of high levels of ToN and PM. It is especially during cold days in northern Sweden that domestic wood combustion is an important source of particles. Both trucks and personal cars are contributing significantly to the particle emissions of ToN and PM. However, exhaust particles mainly affect ToN, whereas most of the PM2.5 and PM10 (total particle mass below 2.5 and 10 ?m diameter respectively) emissions come from road dust generated by the moving vehicles. At locations in large cities, in southern Scandinavia further away from the traffic (urban background), the long distance transported fraction is beginning to dominate contributions to PM10, and it has both natural and anthropogenic sources. The exhaust emissions from traffic can on the other hand make a significant contribution to increased levels of ToN even at distances about 50 km away from the urban area. New particle formation, which is observed more than 1/3 of the days in southern Sweden, can both come from clean as well as more polluted air masses. However, the formation in polluted air has half the impact on ToN that cleaner air has.
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| 23. |
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| 24. |
- Kristensson, Adam, et al.
(författare)
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Characterization of New Particle Formation Events at a Background Site in Southern Sweden: Relation to Air Mass History
- 2008
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:3, s. 330-344
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Tidskriftsartikel (refereegranskat)abstract
- Particle formation events were analysed from aerosol number size distribution data collected at a background station in southern Sweden between February 2001 and May 2004. Events occurred on about 36% of all days and were favoured by high global radiation values. The clearest events (class I, 20% of all days) were observed when the formation rate of activated hypothetical clusters around 1 nm diameter, J(1) was higher than 10((180*CondS-0.60)), where CondS is the condensation sink (in s(-1)). The median condensable vapour concentration, observed formation rate at 3 nm, and growth rate during class I events were 3.0 x 10(7) cm(-3), 1.1 cm(-3) s(-1) and 2.1 nm h(-1), respectively. On 7% of all days, it was possible to observe growth of the newly formed particles exceeding 30 nm geometric mean diameter during event days in the evening, which is important for the regional particle population, and thereby the climate. A trajectory analysis revealed that cleaner air masses were relatively more important for the contribution of Aitken mode particles than polluted ones. Class I events were registered on 36% of all days when trajectories had passed over the open sea, indicating that ship traffic can contribute to particle formation and growth.
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| 25. |
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