| 1. |
- Beddows, D. C. S., et al.
(author)
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Variations in tropospheric submicron particle size distributions across the European continent 2008-2009
- 2014
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:8, s. 4327-4348
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Journal article (peer-reviewed)abstract
- Cluster analysis of particle number size distributions from background sites across Europe is presented. This generated a total of nine clusters of particle size distributions which could be further combined into two main groups, namely: a south-to-north category (four clusters) and a west-to-east category (five clusters). The first group was identified as most frequently being detected inside and around northern Germany and neighbouring countries, showing clear evidence of local afternoon nucleation and growth events that could be linked to movement of air masses from south to north arriving ultimately at the Arctic contributing to Arctic haze. The second group of particle size spectra proved to have narrower size distributions and collectively showed a dependence of modal diameter upon the longitude of the site (west to east) at which they were most frequently detected. These clusters indicated regional nucleation (at the coastal sites) growing to larger modes further inland. The apparent growth rate of the modal diameter was around 0.6-0.9 nm h(-1). Four specific air mass back-trajectories were successively taken as case studies to examine in real time the evolution of aerosol size distributions across Europe. While aerosol growth processes can be observed as aerosol traverses Europe, the processes are often obscured by the addition of aerosol by emissions en route. This study revealed that some of the 24 stations exhibit more complex behaviour than others, especially when impacted by local sources or a variety of different air masses. Overall, the aerosol size distribution clustering analysis greatly simplifies the complex data set and allows a description of aerosol aging processes, which reflects the longer-term average development of particle number size distributions as air masses advect across Europe.
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| 2. |
- Kecorius, Simonas, et al.
(author)
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Significant increase of aerosol number concentrations in air masses crossing a densely trafficked sea area
- 2016
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In: Oceanologia. - : Elsevier BV. - 0078-3234. ; 58:1, s. 1-12
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Journal article (peer-reviewed)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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| 3. |
- Kivekäs, Niku, et al.
(author)
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Contribution of ship traffic to aerosol particle concentrations downwind of a major shipping lane
- 2014
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:16, s. 8255-8267
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Journal article (peer-reviewed)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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| 4. |
- Kristensson, Adam, et al.
(author)
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NanoMap: Geographical mapping of atmospheric new-particle formation through analysis of particle number size distribution and trajectory data
- 2014
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In: Boreal Environment Research: An International Interdisciplinary Journal. - 1239-6095. ; 19, s. 329-342
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Journal article (peer-reviewed)abstract
- Particle number size distributions at various field sites are used to identify atmospheric new-particle formation (NPF) event days. However, the spatial distribution of regionally extensive events is unknown. To remedy this situation, the NanoMap method has been developed to enable the estimation of where NPF occurs within 500 km from any field station using as input size distribution and meteorological trajectories only. Also, the horizontal extension of NPF can be determined. An open-source program to run NanoMap is available on the internet. NanoMap has been developed using as an example the Finnish field site at Hyytiala. It shows that there are frequent NPF events over the Baltic Sea, but not as frequent as over Finland for certain wind directions; hence NanoMap is able to pinpoint areas with a low or high occurrence of NPF events. The method should be applicable to almost any field site.
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| 5. |
- Leinonen, Ville, et al.
(author)
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Comparison of particle number size distribution trends in ground measurements and climate models
- 2022
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:19, s. 12873-12905
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Journal article (peer-reviewed)abstract
- Despite a large number of studies, out of all drivers of radiative forcing, the effect of aerosols has the largest uncertainty in global climate model radiative forcing estimates. There have been studies of aerosol optical properties in climate models, but the effects of particle number size distribution need a more thorough inspection. We investigated the trends and seasonality of particle number concentrations in nucleation, Aitken, and accumulation modes at 21 measurement sites in Europe and the Arctic. For 13 of those sites, with longer measurement time series, we compared the field observations with the results from five climate models, namely EC-Earth3, ECHAM-M7, ECHAM-SALSA, NorESM1.2, and UKESM1. This is the first extensive comparison of detailed aerosol size distribution trends between in situ observations from Europe and five earth system models (ESMs). We found that the trends of particle number concentrations were mostly consistent and decreasing in both measurements and models. However, for many sites, climate models showed weaker decreasing trends than the measurements. Seasonal variability in measured number concentrations, quantified by the ratio between maximum and minimum monthly number concentration, was typically stronger at northern measurement sites compared to other locations. Models had large differences in their seasonal representation, and they can be roughly divided into two categories: for EC-Earth and NorESM, the seasonal cycle was relatively similar for all sites, and for other models the pattern of seasonality varied between northern and southern sites. In addition, the variability in concentrations across sites varied between models, some having relatively similar concentrations for all sites, whereas others showed clear differences in concentrations between remote and urban sites. To conclude, although all of the model simulations had identical input data to describe anthropogenic mass emissions, trends in differently sized particles vary among the models due to assumptions in emission sizes and differences in how models treat size-dependent aerosol processes. The inter-model variability was largest in the accumulation mode, i.e. sizes which have implications for aerosol–cloud interactions. Our analysis also indicates that between models there is a large variation in efficiency of long-range transportation of aerosols to remote locations. The differences in model results are most likely due to the more complex effect of different processes instead of one specific feature (e.g. the representation of aerosol or emission size distributions). Hence, a more detailed characterization of microphysical processes and deposition processes affecting the long-range transport is needed to understand the model variability.
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| 6. |
- Nieminen, Tuomo, et al.
(author)
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Global analysis of continental boundary layer new particle formation based on long-term measurements
- 2018
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:19, s. 14737-14756
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Journal article (peer-reviewed)abstract
- Atmospheric new particle formation (NPF) is an important phenomenon in terms of global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles, and growth rates in the size range of 10-25 nm using at least 1 year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability. At the measurement sites analyzed in this study, NPF occurs most frequently in March-May (on about 30 % of the days) and least frequently in December-February (about 10 % of the days). The median formation rate of 10 nm particles varies by about 3 orders of magnitude (0.01-10 cm(-3) s(-1)) and the growth rate by about an order of magnitude (1-10 nm h(-1)). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate among the different measurement sites, as well as among the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in North America, Asia, and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans.
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| 7. |
- Öström, Emilie, et al.
(author)
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Biogenic SOA formation through gas-phase oxidation and gas-to-particle partitioning-a comparison between process models of varying complexity
- 2014
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 14:21, s. 11853-11869
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Journal article (peer-reviewed)abstract
- Biogenic volatile organic compounds (BVOCs) emitted by vegetation play an important role for aerosol mass loadings since the oxidation products of these compounds can take part in the formation and growth of secondary organic aerosols (SOA). The concentrations and properties of BVOCs and their oxidation products in the atmosphere are poorly characterized, which leads to high uncertainties in modeled SOA mass and properties. In this study, the formation of SOA has been modeled along an air-mass trajectory over northern European boreal forest using two aerosol dynamics box models where the prediction of the condensable organics from the gas-phase oxidation of BVOC is handled with schemes of varying complexity. The use of box model simulations along an air-mass trajectory allows us to compare, under atmospheric relevant conditions, different model parameterizations and their effect on SOA formation. The result of the study shows that the modeled mass concentration of SOA is highly dependent on the organic oxidation scheme used to predict oxidation products. A near-explicit treatment of organic gas-phase oxidation (Master Chemical Mechanism version 3.2) was compared to oxidation schemes that use the volatility basis set (VBS) approach. The resulting SOA mass modeled with different VBS schemes varies by a factor of about 7 depending on how the first-generation oxidation products are parameterized and how they subsequently age (e.g., how fast the gas-phase oxidation products react with the OH radical, how they respond to temperature changes, and if they are allowed to fragment during the aging process). Since the VBS approach is frequently used in regional and global climate models due to its relatively simple treatment of the oxidation products compared to near-explicit oxidation schemes, a better understanding of the above-mentioned processes is needed. Based on the results of this study, fragmentation should be included in order to obtain a realistic SOA formation. Furthermore, compared to the most commonly used VBS schemes, the near-explicit method produces less-but more oxidized-SOA.
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| 8. |
- Öström, Emilie, et al.
(author)
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Modeling the role of highly oxidized multifunctional organic molecules for the growth of new particles over the boreal forest region
- 2017
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:14, s. 8887-8901
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Journal article (peer-reviewed)abstract
- In this study, the processes behind observed new particle formation (NPF) events and subsequent organic-dominated particle growth at the Pallas Atmosphere-Ecosystem Supersite in Northern Finland are explored with the one-dimensional column trajectory model ADCHEM. The modeled sub-micron particle mass is up to ∼75 % composed of SOA formed from highly oxidized multifunctional organic molecules (HOMs) with low or extremely low volatility. In the model the newly formed particles with an initial diameter of 1.5 nm reach a diameter of 7 nm about 2 h earlier than what is typically observed at the station. This is an indication that the model tends to overestimate the initial particle growth. In contrast, the modeled particle growth to CCN size ranges (> 50 nm in diameter) seems to be underestimated because the increase in the concentration of particles above 50 nm in diameter typically occurs several hours later compared to the observations. Due to the high fraction of HOMs in the modeled particles, the oxygen-to-carbon (O : C) atomic ratio of the SOA is nearly 1. This unusually high O : C and the discrepancy between the modeled and observed particle growth might be explained by the fact that the model does not consider any particle-phase reactions involving semi-volatile organic compounds with relatively low O : C. In the model simulations where condensation of low-volatility and extremely low-volatility HOMs explain most of the SOA formation, the phase state of the SOA (assumed either liquid or amorphous solid) has an insignificant impact on the evolution of the particle number size distributions. However, the modeled particle growth rates are sensitive to the method used to estimate the vapor pressures of the HOMs. Future studies should evaluate how heterogeneous reactions involving semi-volatility HOMs and other less-oxidized organic compounds can influence the SOA composition- and size-dependent particle growth.
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