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  • 1. Gagne, S.
    et al.
    Nieminen, T.
    Kurten, T.
    Manninen, H. E.
    Petaja, T.
    Laakso, L.
    Kerminen, V. -M
    Boy, M.
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Factors influencing the contribution of ion-induced nucleation in a boreal forest, Finland2010In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, no 8, p. 3743-3757Article in journal (Refereed)
    Abstract [en]

    We present the longest series of measurements so far (2 years and 7 months) made with an Ion-DMPS at the SMEAR II measurement station in Hyytiala, Southern Finland. We show that the classification into overcharged (implying some participation of ion-induced nucleation) and undercharged (implying no or very little participation of ion-induced nucleation) days, based on Ion-DMPS measurements, agrees with the fraction of ion-induced nucleation based on NAIS measurements. Those classes are based on the ratio of ambient charged particle to steady-state charged particle concentration, known as the charging state. We analyzed the influence of different parameters on the contribution of ion-induced nucleation to the total particle formation rate. We found that the fraction of ion-induced nucleation is typically higher on warmer, drier and sunnier days compared to colder days with less solar radiation and a higher relative humidity. Also, we observed that bigger concentrations of new particles were produced on days with a smaller fraction of ion-induced nucleation. Moreover, sulfuric acid saturation ratios were smaller for days with a bigger fraction of ion-induced nucleation. Finally, we propose explanations on how these different parameters could influence neutral and ion-induced nucleation, and show that the different mechanisms seem to take place at the same time during an event. For example, we propose that these observed differences could be due to high temperature and low vapors' saturation ratios (water and sulfuric acid) increasing the height of the energy barrier a particle has to reach before it can grow and thus limiting neutral nucleation.

  • 2. Jimenez, J. L.
    et al.
    Canagaratna, M. R.
    Donahue, N. M.
    Prevot, A. S. H.
    Zhang, Q.
    Kroll, J. H.
    DeCarlo, P. F.
    Allan, J. D.
    Coe, H.
    Ng, N. L.
    Aiken, A. C.
    Docherty, K. S.
    Ulbrich, I. M.
    Grieshop, A. P.
    Robinson, A. L.
    Duplissy, J.
    Smith, J. D.
    Wilson, K. R.
    Lanz, V. A.
    Hueglin, C.
    Sun, Y. L.
    Tian, J.
    Laaksonen, A.
    Raatikainen, T.
    Rautiainen, J.
    Vaattovaara, P.
    Ehn, M.
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Tomlinson, J. M.
    Collins, D. R.
    Cubison, M. J.
    Dunlea, E. J.
    Huffman, J. A.
    Onasch, T. B.
    Alfarra, M. R.
    Williams, P. I.
    Bower, K.
    Kondo, Y.
    Schneider, J.
    Drewnick, F.
    Borrmann, S.
    Weimer, S.
    Demerjian, K.
    Salcedo, D.
    Cottrell, L.
    Griffin, R.
    Takami, A.
    Miyoshi, T.
    Hatakeyama, S.
    Shimono, A.
    Sun, J. Y.
    Zhang, Y. M.
    Dzepina, K.
    Kimmel, J. R.
    Sueper, D.
    Jayne, J. T.
    Herndon, S. C.
    Trimborn, A. M.
    Williams, L. R.
    Wood, E. C.
    Middlebrook, A. M.
    Kolb, C. E.
    Baltensperger, U.
    Worsnop, D. R.
    Evolution of Organic Aerosols in the Atmosphere2009In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 326, no 5959, p. 1525-1529Article in journal (Refereed)
    Abstract [en]

    Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high-time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models.

  • 3. Manninen, H. E.
    et al.
    Nieminen, T.
    Asmi, E.
    Gagne, S.
    Hakkinen, S.
    Lehtipalo, K.
    Aalto, P.
    Vana, M.
    Mirme, A.
    Mirme, S.
    Horrak, U.
    Plass-Duelmer, C.
    Stange, G.
    Kiss, G.
    Hoffer, A.
    Toeroe, N.
    Moerman, M.
    Henzing, B.
    de Leeuw, G.
    Brinkenberg, M.
    Kouvarakis, G. N.
    Bougiatioti, A.
    Mihalopoulos, N.
    O'Dowd, C.
    Ceburnis, D.
    Arneth, A.
    Svenningsson, B.
    Swietlicki, E.
    Tarozzi, L.
    Decesari, S.
    Facchini, M. C.
    Birmili, W.
    Sonntag, A.
    Wiedensohler, A.
    Boulon, J.
    Sellegri, K.
    Laj, P.
    Gysel, M.
    Bukowiecki, N.
    Weingartner, E.
    Wehrle, G.
    Laaksonen, A.
    Hamed, A.
    Joutsensaari, J.
    Petaja, T.
    Kerminen, V. -M
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    EUCAARI ion spectrometer measurements at 12 European sites - analysis of new particle formation events2010In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, no 16, p. 7907-7927Article in journal (Refereed)
    Abstract [en]

    We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range similar to 1-42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1-30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.

  • 4. Nieminen, T.
    et al.
    Paasonen, P.
    Manninen, H. E.
    Sellegri, K.
    Kerminen, V. -M
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Parameterization of ion-induced nucleation rates based on ambient = servations2011In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, no 7, p. 3393-3402Article in journal (Refereed)
    Abstract [en]

    Atmospheric ions participate in the formation of new atmospheric aerosol particles, yet their exact role in this process has remained unclear. Here we derive a new simple parameterization for ion-induced nucleation or, more precisely, for the formation rate of charged 2-nm particles. The parameterization is semi-empirical in the sense that it is based on comprehensive results of one-year-long atmospheric cluster and particle measurements in the size range similar to 1-42 nm within the EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions) project. Data from 12 field sites across Europe measured with different types of air ion and cluster mobility spectrometers were used in our analysis, with more in-depth analysis made using data from four stations with concomitant sulphuric acid measurements. The parameterization is given in two slightly different forms: a more accurate one that requires information on sulfuric acid and nucleating organic vapor concentrations, and a simpler one in which this information is replaced with the global radiation intensity. These new parameterizations are applicable to all large-scale atmospheric models containing size-resolved aerosol microphysics, and a scheme to calculate concentrations of sulphuric acid, condensing organic vapours and cluster ions.

  • 5. Petaja, Tuukka
    et al.
    Dal Maso, Miikka
    Sipila, Mikko
    Riipinen, Ilona
    University of Helsinki.
    Kerminen, Veli-Matti
    Kulmala, Markku
    University of Helsinki.
    Formation and Growth of Atmospheric Aerosol Particles2012In: NATURE'S NANOSTRUCTURES, SINGAPORE: PAN STANFORD PUBLISHING PTE LTD , 2012, p. 399-440Chapter in book (Refereed)
  • 6. Pikridas, Michael
    et al.
    Riipinen, Ilona
    University of Patras.
    Hildebrandt, Lea
    Kostenidou, Evangelia
    Manninen, Hanna
    Mihalopoulos, Nikos
    Kalivitis, Nikos
    Burkhart, John F.
    Stohl, Andreas
    Kulmala, Markku
    University of Helsinki.
    Pandis, Spyros N.
    New particle formation at a remote site in the eastern Mediterranean2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, p. D12205-Article in journal (Refereed)
    Abstract [en]

    A year (6-April-2008 to 14-April-2009) of particulate monitoring was conducted at a remote coastal station on the island of Crete, Greece in the eastern Mediterranean. Fifty-eight regional new particle formation events were observed with an Air Ion Spectrometer (AIS), half of which occurred during the coldest months of the year (December-March). Particle formation was favored by air masses arriving from the west that crossed Crete or southern Greece prior to reaching the site and also by lower-than-average condensational sinks (CS). Aerosol composition data, which were acquired during month-long campaigns in the summer and winter, suggest that nucleation events occurred only when particles were neutral. This is consistent with the hypothesis that a lack of NH3, during periods when particles are acidic, may limit nucleation in sulfate-rich environments. Nucleation was not limited by the availability of SO2 alone, as nucleation events often did not take place during periods with high SO2 or H2SO4 concentrations. The above results support the hypothesis that an additional reactant (other than H2SO4) plays an important role in the formation and/or growth of new particles. Our results are consistent with NH3 being this missing reactant.

  • 7. Sipila, Mikko
    et al.
    Berndt, Torsten
    Petaja, Tuukka
    Brus, David
    Vanhanen, Joonas
    Stratmann, Frank
    Patokoski, Johanna
    Mauldin, Roy L., III
    Hyvarinen, Antti-Pekka
    Lihavainen, Heikki
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    The Role of Sulfuric Acid in Atmospheric Nucleation2010In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 327, no 5970, p. 1243-1246Article in journal (Refereed)
    Abstract [en]

    Nucleation is a fundamental step in atmospheric new-particle formation. However, laboratory experiments on nucleation have systematically failed to demonstrate sulfuric acid particle formation rates as high as those necessary to account for ambient atmospheric concentrations, and the role of sulfuric acid in atmospheric nucleation has remained a mystery. Here, we report measurements of new particles ( with diameters of approximately 1.5 nanometers) observed immediately after their formation at atmospherically relevant sulfuric acid concentrations. Furthermore, we show that correlations between measured nucleation rates and sulfuric acid concentrations suggest that freshly formed particles contain one to two sulfuric acid molecules, a number consistent with assumptions that are based on atmospheric observations. Incorporation of these findings into global models should improve the understanding of the impact of secondary particle formation on climate.

  • 8.
    Tunved, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Korhonen, Hannele
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Lehtinen, Kari
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    A pseudo-Lagrangian model study of the size distribution properties over Scandinavia: Transport from Aspvreten to Värriö2004In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, no 4, p. 7757-7794Article in journal (Refereed)
    Abstract [en]

    The evolution of the aerosol size distribution during transport between Aspvreten (58.8° N, 17.4° E) and Värriö (67.46° N, 29.35° E) was studied using a pseudo-Lagrangian approach. Aerosol dynamic processes were studied and interpreted utilizing a state-of-the-art aerosol dynamic box model UHMA (University of Helsinki Multicomponent Aerosol model) complemented with OH, NO3, O3 and terpene chemistry. In the model simulations, the growth and formation of aerosol particles was controlled by sulphuric acid, ammonia, water and an unidentified low volatile organic compound. This organic compound was assumed to be a product of terpene oxidation with a yield of 13% in the base case conditions. Changes of aerosol size distribution properties during transport between the stations were examined in twelve clear sky cases. On average, the modelled number agreed fairly well with observations. Mass concentration was overestimated by 10%. Apart from dilution, the only removal mechanism for aerosol mass is dry deposition. A series of sensitivity tests performed revealed that the absolute magnitude of dry deposition effects on the aerosol size distribution is slow overall. Furthermore, nucleation does not leave a significant contribution to aerosol number in the selected cases. The sensitivity of the modelled size distribution to concentration of precursor gases and oxidants is, however, obvious. In order to explain observed mass increase during transport we conclude that a yield of low volatile products from oxidation of terpenes of 10–15% is required to explain observed growth rates. Coagulation is acknowledged to be highly important in modelled cases.

  • 9. Virtanen, Annele
    et al.
    Joutsensaari, Jorma
    Koop, Thomas
    Kannosto, Jonna
    Yli-Pirila, Pasi
    Leskinen, Jani
    Makela, Jyrki M.
    Holopainen, Jarmo K.
    Poeschl, Ulrich
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Worsnop, Douglas R.
    Laaksonen, Ari
    An amorphous solid state of biogenic secondary organic aerosol particles2010In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 467, no 7317, p. 824-827Article in journal (Refereed)
    Abstract [en]

    Secondary organic aerosol (SOA) particles are formed in the atmosphere from condensable oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs)(1-7). On a global scale, biogenic VOCs account for about 90% of VOC emissions(1,8) and of SOA formation (90 billion kilograms of carbon per year)(1-4). SOA particles can scatter radiation and act as cloud condensation or ice nuclei, and thereby influence the Earth's radiation balance and climate(1,2,5,9,10). They consist of a myriad of different compounds with varying physicochemical properties, and little information is available on the phase state of SOA particles. Gas-particle partitioning models usually assume that SOA particles are liquid(1,5,11), but here we present experimental evidence that they can be solid under ambient conditions. We investigated biogenic SOA particles formed from oxidation products of VOCs in plant chamber experiments and in boreal forests within a few hours after atmospheric nucleation events. On the basis of observed particle bouncing in an aerosol impactor and of electron microscopy we conclude that biogenic SOA particles can adopt an amorphous solid-most probably glassy-state. This amorphous solid state should provoke a rethinking of SOA processes because it may influence the partitioning of semi-volatile compounds, reduce the rate of heterogeneous chemical reactions, affect the particles' ability to accommodate water and act as cloud condensation or ice nuclei, and change the atmospheric lifetime of the particles(12-15). Thus, the results of this study challenge traditional views of the kinetics and thermodynamics of SOA formation and transformation in the atmosphere and their implications for air quality and climate.

  • 10. Vuollekoski, H.
    et al.
    Boy, M.
    Kerminen, V. -M
    Lehtinen, K. E. J.
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    MECCO: A method to estimate concentrations of condensing organics-Description and evaluation of a Markov chain Monte Carlo application2010In: Journal of Aerosol Science, ISSN 0021-8502, E-ISSN 1879-1964, Vol. 41, no 12, p. 1080-1089Article in journal (Refereed)
    Abstract [en]

    The development of a new method to estimate concentrations of condensing organics (MECCO) is described. A Markov chain Monte Carlo method is applied, and by using measured particle size distribution and random vapor concentrations as input, the predicted changes in particle population by an aerosol dynamics model are utilized. The method provides the ambient vapor concentrations required for the observed particle growth in particle number size distribution data, assuming all growth can be attributed to net condensation of super-saturated vapors. In this paper, MECCO was coupled with the UHMA box-model to provide aerosol dynamics. With few changes, MECCO could be applied to study other input parameters, and coupled with other dynamics models as well. Evaluation of the method was carried out with simulated output from the UHMA model using the assumption of three organic vapors, and MECCO-UHMA was able to estimate their concentrations with great accuracy. However, the condensation of vapors is currently considered irreversible, since the used particle size distribution data do not provide information on the composition of particles. The distinguishing between the vapors is based on few vapor parameters, which limits the possibilities of identifying actual vapors. An example of atmospheric application is also presented. This revealed the importance of quality control of the input particle concentrations: instrumental noise and changes in the observed air mass pose challenges for the presented method. Data need to be smoothed in a reasonable way so that the point-like measurements can be utilized, but also so that the important information on particle growth is conserved. MECCO is a useful tool to approximate vapor concentrations and may be applied to estimate vapor properties as well. However, a computationally efficient and physically accurate aerosol dynamics model is essential for MECCO's performance.

  • 11. Vuollekoski, H.
    et al.
    Sihto, S. -L.
    Kerminen, V. -M.
    Kulmala, Markku
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). University of Helsinki, Finland.
    Lehtinen, K. E. J.
    A numerical comparison of different methods for determining the particle formation rate2012In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 5, p. 2289-2295Article in journal (Refereed)
    Abstract [en]

    Different methods of determining formation rates of 3 nm particles are compared, basing on analysis of simulated data, but the results are valid for analyses of experimental particle size distribution data as well, at least within the accuracy of the applied model. The study shows that the method of determining formation rates indirectly from measured number concentration data of 3-6 nm particles is generally in good agreement with the theoretical calculation with a systematic error of 0-20%. While this accuracy is often enough, a simple modification to the approximative equation for the formation rate is recommended. A brief study on real atmospheric data implied that in some cases the accuracy gain may be significant.

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