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- Hussein, T., et al.
(author)
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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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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9:14, s. 4699-4716
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Journal article (peer-reviewed)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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| 2. |
- Kristensson, Adam
(author)
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Aerosol Particle Sources Affecting the Swedish Air Quality at Urban and Rural Level.
- 2005
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Doctoral thesis (other academic/artistic)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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| 3. |
- Kristensson, Adam, et al.
(author)
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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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In: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:3, s. 330-344
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Journal article (peer-reviewed)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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