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  • 1.
    Acosta Navarro, Juan C.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Pausata, Francesco S. R.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Lewinschal, Anna
    Stockholm University, Faculty of Science, Department of Meteorology .
    Varma, Vidya
    Seland, Øyvind
    Gauss, Michael
    Iversen, Trond
    Kirkevåg, Alf
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Hansson, Hans Christen
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Future response of temperature and precipitation to reduced aerosol emissions as compared with increased greenhouse gas concentrations2017In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 30, no 3, p. 939-954Article in journal (Refereed)
    Abstract [en]

    Experiments with a climate model (NorESM1) were performed to isolate the effects of aerosol particles and greenhouse gases on surface temperature and precipitation in simulations of future climate. The simulations show that by 2025-2049, a reduction of aerosol emissions from fossil fuels following a maximum technically feasible reduction (MFR) scenario could lead to a global and Arctic warming of 0.26 K and 0.84 K, respectively; as compared with a simulation with fixed aerosol emissions at the level of 2005. If fossil fuel emissions of aerosols follow a current legislation emissions (CLE) scenario, the NorESM1 model simulations yield a non-significant change in global and Arctic average surface temperature as compared with aerosol emissions fixed at year 2005. The corresponding greenhouse gas effect following the RCP4.5 emission scenario leads to a global and Arctic warming of 0.35 K and 0.94 K, respectively.

    The model yields a marked annual average northward shift in the inter-tropical convergence zone with decreasing aerosol emissions and subsequent warming of the northern hemisphere. The shift is most pronounced in the MFR scenario but also visible in the CLE scenario. The modeled temperature response to a change in greenhouse gas concentrations is relatively symmetric between the hemispheres and there is no marked shift in the annual average position of the inter-tropical convergence zone. The strong reduction in aerosol emissions in MFR also leads to a net southward cross-hemispheric energy transport anomaly both in the atmosphere and ocean, and enhanced monsoon circulation in Southeast and East Asia causing an increase in precipitation over a large part of this region.

  • 2.
    Acosta Navarro, Juan Camilo
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Smolander, S.
    Struthers, H.
    Zorita, E.
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Kaplan, J. O.
    Guenther, A.
    Arneth, A.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Global emissions of terpenoid VOCs from terrestrial vegetation in the last millennium2014In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 119, no 11, p. 6867-6885Article in journal (Refereed)
    Abstract [en]

    We investigated the millennial variability (1000 A.D.-2000 A.D.) of global biogenic volatile organic compound (BVOC) emissions by using two independent numerical models: The Model of Emissions of Gases and Aerosols from Nature (MEGAN), for isoprene, monoterpene, and sesquiterpene, and Lund-Potsdam-Jena-General Ecosystem Simulator (LPJ-GUESS), for isoprene and monoterpenes. We found the millennial trends of global isoprene emissions to be mostly affected by land cover and atmospheric carbon dioxide changes, whereas monoterpene and sesquiterpene emission trends were dominated by temperature change. Isoprene emissions declined substantially in regions with large and rapid land cover change. In addition, isoprene emission sensitivity to drought proved to have significant short-term global effects. By the end of the past millennium MEGAN isoprene emissions were 634 TgC yr-1 (13% and 19% less than during 1750-1850 and 1000-1200, respectively), and LPJ-GUESS emissions were 323 TgC yr-1(15% and 20% less than during 1750-1850 and 1000-1200, respectively). Monoterpene emissions were 89 TgC yr-1(10% and 6% higher than during 1750-1850 and 1000-1200, respectively) in MEGAN, and 24 TgC yr-1 (2% higher and 5% less than during 1750-1850 and 1000-1200, respectively) in LPJ-GUESS. MEGAN sesquiterpene emissions were 36 TgC yr-1(10% and 4% higher than during 1750-1850 and 1000-1200, respectively). Although both models capture similar emission trends, the magnitude of the emissions are different. This highlights the importance of building better constraints on VOC emissions from terrestrial vegetation.

  • 3.
    Acosta Navarro, Juan Camilo
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Varma, Vidya
    Stockholm University, Faculty of Science, Department of Meteorology .
    Riipinen, Irina
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Seland, O.
    Kirkevag, A.
    Struthers, Hamish
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Linköping University, Sweden.
    Iversen, T.
    Hansson, Hans-Christen
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Amplification of Arctic warming by past air pollution reductions in Europe2016In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 9, no 4, p. 277-+Article in journal (Refereed)
    Abstract [en]

    The Arctic region is warming considerably faster than the rest of the globe(1), with important consequences for the ecosystems(2) and human exploration of the region(3). However, the reasons behind this Arctic amplification are not entirely clear(4). As a result of measures to enhance air quality, anthropogenic emissions of particulate matter and its precursors have drastically decreased in parts of the Northern Hemisphere over the past three decades(5). Here we present simulations with an Earth system model with comprehensive aerosol physics and chemistry that show that the sulfate aerosol reductions in Europe since 1980 can potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic region receives an additional 0.3Wm(-2) of energy, and warms by 0.5 degrees C on annual average in simulations with declining European sulfur emissions in line with historical observations, compared with a model simulation with fixed European emissions at 1980 levels. Arctic warming is amplified mainly in fall and winter, but the warming is initiated in summer by an increase in incoming solar radiation as well as an enhanced poleward oceanic and atmospheric heat transport. The simulated summertime energy surplus reduces sea-ice cover, which leads to a transfer of heat from the Arctic Ocean to the atmosphere. We conclude that air quality regulations in the Northern Hemisphere, the ocean and atmospheric circulation, and Arctic climate are inherently linked.

  • 4.
    Ahlm, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Julin, Jan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Fountoukis, C.
    Pandis, S. N.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Particle number concentrations over Europe in 2030: the role of emissions and new particle formation2013In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 13, no 20, p. 10271-10283Article in journal (Refereed)
    Abstract [en]

    The aerosol particle number concentration is a key parameter when estimating impacts of aerosol particles on climate and human health. We use a three-dimensional chemical transport model with detailed microphysics, PMCAMx-UF, to simulate particle number concentrations over Europe in the year 2030, by applying emission scenarios for trace gases and primary aerosols. The scenarios are based on expected changes in anthropogenic emissions of sulfur dioxide, ammonia, nitrogen oxides, and primary aerosol particles with a diameter less than 2.5 mu m (PM2.5) focusing on a photochemically active period, and the implications for other seasons are discussed. For the baseline scenario, which represents a best estimate of the evolution of anthropogenic emissions in Europe, PMCAMx-UF predicts that the total particle number concentration (N-tot) will decrease by 30-70% between 2008 and 2030. The number concentration of particles larger than 100 nm (N-100), a proxy for cloud condensation nuclei (CCN) concentration, is predicted to decrease by 40-70% during the same period. The predicted decrease in N-tot is mainly a result of reduced new particle formation due to the expected reduction in SO2 emissions, whereas the predicted decrease in N-100 is a result of both decreasing condensational growth and reduced primary aerosol emissions. For larger emission reductions, PMCAMx-UF predicts reductions of 60-80% in both N-tot and N-100 over Europe. Sensitivity tests reveal that a reduction in SO2 emissions is far more efficient than any other emission reduction investigated, in reducing N-tot. For N-100, emission reductions of both SO2 and PM2.5 contribute significantly to the reduced concentration, even though SO2 plays the dominant role once more. The impact of SO2 for both new particle formation and growth over Europe may be expected to be somewhat higher during the simulated period with high photochemical activity than during times of the year with less incoming solar radiation. The predicted reductions in both N-tot and N-100 between 2008 and 2030 in this study will likely reduce both the aerosol direct and indirect effects, and limit the damaging effects of aerosol particles on human health in Europe

  • 5. Almeida, Joao
    et al.
    Schobesberger, Siegfried
    Kuerten, Andreas
    Ortega, Ismael K.
    Kupiainen-Maatta, Oona
    Praplan, Arnaud P.
    Adamov, Alexey
    Amorim, Antonio
    Bianchi, Federico
    Breitenlechner, Martin
    David, Andre
    Dommen, Josef
    Donahue, Neil M.
    Downard, Andrew
    Dunne, Eimear
    Duplissy, Jonathan
    Ehrhart, Sebastian
    Flagan, Richard C.
    Franchin, Alessandro
    Guida, Roberto
    Hakala, Jani
    Hansel, Armin
    Heinritzi, Martin
    Henschel, Henning
    Jokinen, Tuija
    Junninen, Heikki
    Kajos, Maija
    Kangasluoma, Juha
    Keskinen, Helmi
    Kupc, Agnieszka
    Kurten, Theo
    Kvashin, Alexander N.
    Laaksonen, Ari
    Lehtipalo, Katrianne
    Leiminger, Markus
    Leppa, Johannes
    Loukonen, Ville
    Makhmutov, Vladimir
    Mathot, Serge
    McGrath, Matthew J.
    Nieminen, Tuomo
    Olenius, Tinja
    Onnela, Antti
    Petaja, Tuukka
    Riccobono, Francesco
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Rissanen, Matti
    Rondo, Linda
    Ruuskanen, Taina
    Santos, Filipe D.
    Sarnela, Nina
    Schallhart, Simon
    Schnitzhofer, Ralf
    Seinfeld, John H.
    Simon, Mario
    Sipila, Mikko
    Stozhkov, Yuri
    Stratmann, Frank
    Tome, Antonio
    Troestl, Jasmin
    Tsagkogeorgas, Georgios
    Vaattovaara, Petri
    Viisanen, Yrjo
    Virtanen, Annele
    Vrtala, Aron
    Wagner, Paul E.
    Weingartner, Ernest
    Wex, Heike
    Williamson, Christina
    Wimmer, Daniela
    Ye, Penglin
    Yli-Juuti, Taina
    Carslaw, Kenneth S.
    Kulmala, Markku
    Curtius, Joachim
    Baltensperger, Urs
    Worsnop, Douglas R.
    Vehkamaki, Hanna
    Kirkby, Jasper
    Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 502, no 7471, p. 359-+Article in journal (Refereed)
    Abstract [en]

    Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes(2). Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases(2). However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere(3). It is thought that amines may enhance nucleation(4-16), but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.

  • 6. Bannan, Thomas J.
    et al.
    Booth, A. Murray
    Jones, Benjamin T.
    O'Meara, Simon
    Barley, Mark H.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Percival, Carl J.
    Topping, David
    Measured Saturation Vapor Pressures of Phenolic and Nitro-aromatic Compounds2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 7, p. 3922-3928Article in journal (Refereed)
    Abstract [en]

    Phenolic and nitro-aromatic compounds are extremely toxic components of atmospheric aerosol that are currently not well understood. In this Article, solid and subcooled-liquid-state saturation vapor pressures of phenolic and nitro-aromatic compounds are measured using Knudsen Effusion Mass Spectrometry (KEMS) over a range of temperatures (298-318 K). Vapor pressure estimation methods, assessed in this study, do not replicate the observed dependency on the relative positions of functional groups. With a few exceptions, the estimates are biased toward predicting saturation vapor pressures that are too high, by 5-6 orders of magnitude in some cases. Basic partitioning theory comparisons indicate that overestimation of vapor pressures in such cases would cause us to expect these compounds to be present in the gas state, whereas measurements in this study suggest these phenolic and nitro-aromatic will partition into the condensed state for a wide range of ambient conditions if absorptive partitioning plays a dominant role. While these techniques might have both structural and parametric uncertainties, the new data presented here should support studies trying to ascertain the role of nitrogen containing organics on aerosol growth and human health impacts.

  • 7. Baranizadeh, Elham
    et al.
    Murphy, Benjamin N.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Julin, Jan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Eastern Finland, Finland.
    Falahat, Saeed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Reddington, Carly L.
    Arola, Antti
    Ahlm, Lars
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mikkonen, Santtu
    Fountoukis, Christos
    Patoulias, David
    Minikin, Andreas
    Hamburger, Thomas
    Laaksonen, Ari
    Pandis, Spyros N.
    Vehkamäki, Hanna
    Lehtinen, Kari E. J.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Implementation of state-of-the-art ternary new-particle formation scheme to the regional chemical transport model PMCAMx-UF in Europe2016In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 9, no 8, p. 2741-2754Article in journal (Refereed)
    Abstract [en]

    The particle formation scheme within PMCAMx-UF, a three-dimensional chemical transport model, was updated with particle formation rates for the ternary H2SO4-NH3-H2O pathway simulated by the Atmospheric Cluster Dynamics Code (ACDC) using quantum chemical input data. The model was applied over Europe for May 2008, during which the EUCAARI-LONGREX (European Aerosol Cloud Climate and Air Quality Interactions-Long-Range Experiment) campaign was carried out, providing aircraft vertical profiles of aerosol number concentrations. The updated model reproduces the observed number concentrations of particles larger than 4 nm within 1 order of magnitude throughout the atmospheric column. This agreement is encouraging considering the fact that no semi-empirical fitting was needed to obtain realistic particle formation rates. The cloud adjustment scheme for modifying the photolysis rate profiles within PMCAMx-UF was also updated with the TUV (Tropospheric Ultraviolet and Visible) radiative-transfer model. Results show that, although the effect of the new cloud adjustment scheme on total number concentrations is small, enhanced new-particle formation is predicted near cloudy regions. This is due to the enhanced radiation above and in the vicinity of the clouds, which in turn leads to higher production of sulfuric acid. The sensitivity of the results to including emissions from natural sources is also discussed.

  • 8. Bilde, Merete
    et al.
    Barsanti, Kelley
    Booth, Murray
    Cappa, Christopher D.
    Donahue, Neil M.
    Emanuelsson, Eva U.
    McFiggans, Gordon
    Krieger, Ulrich K.
    Marcolli, Claudia
    Tropping, David
    Ziemann, Paul
    Barley, Mark
    Clegg, Simon
    Dennis-Smither, Benjamin
    Hallquist, Mattias
    Hallquist, Asa M.
    Khlystov, Andrey
    Kulmala, Markku
    Mogensen, Ditte
    Percival, Carl J.
    Pope, Francis
    Reid, Jonathan P.
    da Silva, M. A. V. Ribeiro
    Rosenoern, Thomas
    Salo, Kent
    Soonsin, Vacharapom Pia
    Yli-Juuti, Taina
    Prisle, Nonne L.
    Pagels, Joakim
    Rarey, Juergen
    Zardini, Alessandro A.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures2015In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 115, no 10, p. 4115-4156Article, review/survey (Refereed)
  • 9. Booth, A. Murray
    et al.
    Murphy, Ben
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Faculty of Science, Department of Meteorology .
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Percival, Carl J.
    Topping, David O.
    Connecting Bulk Viscosity Measurements to Kinetic Limitations on Attaining Equilibrium for a Model Aerosol Composition2014In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 16, p. 9298-9305Article in journal (Refereed)
    Abstract [en]

    The growth, composition, and evolution of secondary organic aerosol (SOA) are governed by properties of individual compounds and ensemble mixtures that affect partitioning between the vapor and condensed phase. There has been considerable recent interest in the idea that SOA can form highly viscous particles where the diffusion of either water or semivolatile organics within the particle is sufficiently hindered to affect evaporation and growth. Despite numerous indirect inferences of viscous behavior from SOA evaporation or bounce within aerosol instruments, there have been no bulk measurements of the viscosity of well-constrained model aerosol systems of atmospheric significance. Here the viscous behavior of a well-defined model system of 9 dicarboxylic acids is investigated directly with complementary measurements and model predictions used to infer phase state. Results not only allow us to discuss the atmospheric implications for SOA formation through this representative mixture, but also the potential impact of current methodologies used for probing this affect in both the laboratory and from a modeling perspective. We show, quantitatively, that the physical state transformation from liquid-like to amorphous semisolid can substantially increase the importance of mass transfer limitations within particles by 7 orders of magnitude for 100 nm diameter particles. Recommendations for future research directions are given.

  • 10.
    Bourgeois, Quentin
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Renard, Jean-Baptiste
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Devasthale, Abhay
    Bender, Frida A. -M.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Berthet, Gwenaël
    Tackett, Jason L.
    How much of the global aerosol optical depth is found in the boundary layer and free troposphere?2018In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 18, no 10, p. 7709-7720Article in journal (Refereed)
    Abstract [en]

    The global aerosol extinction from the CALIOP space lidar was used to compute aerosol optical depth (AOD) over a 9-year period (2007-2015) and partitioned between the boundary layer (BL) and the free troposphere (FT) using BL heights obtained from the ERA-Interim archive. The results show that the vertical distribution of AOD does not follow the diurnal cycle of the BL but remains similar between day and night highlighting the presence of a residual layer during night. The BL and FT contribute 69 and 31 %, respectively, to the global tropospheric AOD during daytime in line with observations obtained in Aire sur l'Adour (France) using the Light Optical Aerosol Counter (LOAC) instrument. The FT AOD contribution is larger in the tropics than at mid-latitudes which indicates that convective transport largely controls the vertical profile of aerosols. Over oceans, the FT AOD contribution is mainly governed by long-range transport of aerosols from emission sources located within neighboring continents. According to the CALIOP aerosol classification, dust and smoke particles are the main aerosol types transported into the FT. Overall, the study shows that the fraction of AOD in the FT - and thus potentially located above low-level clouds - is substantial and deserves more attention when evaluating the radiative effect of aerosols in climate models. More generally, the results have implications for processes determining the overall budgets, sources, sinks and transport of aerosol particles and their description in atmospheric models.

  • 11.
    Crljenica, Ivica
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Yli-Juuti, Taina
    Zardini, Alessandro A.
    Julin, Jan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bilde, Merete
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Center for Atmospheric Particle Studies, Carnegie Mellon University.
    Determining the saturation vapour pressures of keto-dicarboxylic acids in aqueous solutions2013In: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, p. 468-471Conference paper (Refereed)
    Abstract [en]

    A two-compartment binary mass transport model with group contribution methods parametrizations for the physical properties of the organic acids (UNIFAC Dortmund method for activity coefficients, GCVOL-OL-60 method for the pure liquid acid density, GC-MG method for the pure acid surface tension at room temperature, Fuller et al. method for the diffusion coefficients) was used to interpret the evaporation experiments of 100 nm sized keto-dicarboxylic acid aqueous solutions droplets at ambient temperature. The determined values for the saturation vapour pressure of liquid 2-keto-glutaric acid are in the order of 10(-5) Pa.

  • 12.
    Dalirian, Maryam
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Keskinen, H.
    Ahlm, Lars
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ylisirniö, A.
    Romakkaniemi, S.
    Laaksonen, A.
    Virtanen, A.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    CCN activation of fumed silica aerosols mixed with soluble pollutants2015In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, no 7, p. 3815-3829Article in journal (Refereed)
    Abstract [en]

    Particle-water interactions of completely soluble or insoluble particles are fairly well understood but less is known of aerosols consisting of mixtures of soluble and insoluble components. In this study, laboratory measurements were performed to investigate cloud condensation nuclei (CCN) activity of silica particles mixed with ammonium sulfate (a salt), sucrose (a sugar) and bovine serum albumin known as BSA (a protein). The agglomerated structure of the silica particles was investigated using measurements with a differential mobility analyser (DMA) and an aerosol particle mass analyser (APM). Based on these data, the particles were assumed to be compact agglomerates when studying their CCN activation capabilities. Furthermore, the critical super-saturations of particles consisting of pure and mixed soluble and insoluble compounds were explored using existing theoretical frameworks. These results showed that the CCN activation of single-component particles was in good agreement with Kohler- and adsorption theory based models when the agglomerated structure was accounted for. For mixed particles the CCN activation was governed by the soluble components, and the soluble fraction varied considerably with particle size for our wet-generated aerosols. Our results confirm the hypothesis that knowing the soluble fraction is the key parameter needed for describing the CCN activation of mixed aerosols, and highlight the importance of controlled coating techniques for acquiring a detailed understanding of the CCN activation of atmospheric insoluble particles mixed with soluble pollutants.

  • 13.
    Dalirian, Maryam
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ylisirniö, Arttu
    Buchholz, Angela
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Virtanen, Annele
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Cloud droplet activation of black carbon particles coated with organic compounds of varying solubility2018In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 18, no 16, p. 12477-12489Article in journal (Refereed)
    Abstract [en]

    Atmospheric black carbon (BC) particles are a concern due to their impact on air quality and climate. Their net climate effect 15 is, however, still uncertain. This uncertainty is partly related to the contribution of coated BC-particles to the global CCN budgets. In this study, laboratory measurements were performed to investigate cloud condensation nuclei (CCN) activity of BC (Regal black) particles, in pure state or coated through evaporating and subsequent condensation of glutaric acid, levoglucosan (both water-soluble organics) or oleic acid (an organic compound with low solubility). A combination of Soot Particle Aerosol Mass Spectrometer (SP-AMS) measurements and size distribution measurements with Scanning Mobility 20 Particle Sizer (SMPS) showed that the studied BC particles were nearly spherical agglomerates with a fractal dimension of 2.79 and that they were coated evenly by the organic species. The CCN activity of BC particles increased after coating with all the studied compounds and was governed by the fraction of organic material. The CCN activation of the BC particles coated by glutaric acid and levoglucosan were in good agreement with the theoretical calculations using shell-and-core model, which is based on a combination of the CCN activities of the pure compounds. The oleic acid coating enhanced the CCN 25 activity of the BC particles, even though the pure oleic acid particles were CCN inactive. The surprising effect of oleic acid might be related to the arrangement of the oleic acid molecules on the surface of the BC cores or other surface phenomena facilitating water condensation onto the coated particles. Our results show potential in accurately predicting the CCN activity of atmospheric BC coated with organic species by present theories, given that the identities and amount of the coating species are known. Furthermore, our results suggest that even relatively thin soluble coatings (around 2 nm for the compounds studied here) are enough to make the insoluble BC particles CCN active at typical atmospheric supersaturations and thus be efficiently taken up by cloud droplets. This highlights the need of an accurate description of the composition of atmospheric particles containing BC to unravel their net impact on climate.

  • 14. D’Andrea, S. D. D.
    et al.
    Acosta Navarro, Juan Camilo
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Farina, S. C.
    Scott, C. E.
    Rap, A.
    Farmer, D. K.
    Spracklen, D. V.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Carnegie Mellon University, USA.
    Pierce, J. R.
    Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation2015In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, p. 2247-2268Article in journal (Refereed)
    Abstract [en]

    Emissions of biogenic volatile organic compounds (BVOCs) have changed in the past millennium due to changes in land use, temperature, and CO2 concentrations. Recent reconstructions of BVOC emissions have predicted that global isoprene emissions have decreased, while monoterpene and sesquiterpene emissions have increased; however, all three show regional variability due to competition between the various influencing factors. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on secondary organic aerosol (SOA) formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS (Goddard Earth Observing System; TwO-Moment Aerosol Sectional) global aerosol microphysics model. With anthropogenic emissions (e.g., SO2, NOx, primary aerosols) turned off and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp > 80 nm (N80) of > 25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in the combined aerosol radiative effect (direct and indirect) of > 0.5 W m−2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields, and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m−2 and the global mean cloud-albedo aerosol indirect effect of between −0.008 and −0.056 W m−2. This change in aerosols, and the associated radiative forcing, could be a largely overlooked and important anthropogenic aerosol effect on regional climates.

  • 15. D'Andrea, S. D.
    et al.
    Hakkinen, S. A. K.
    Westervelt, D. M.
    Kuang, C.
    Levin, E. J. T.
    Kanawade, V. P.
    Leaitch, W. R.
    Spracklen, D. V.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pierce, J. R.
    Understanding global secondary organic aerosol amount and size-resolved condensational behavior2013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 22, p. 11519-11534Article in journal (Refereed)
    Abstract [en]

    Recent research has shown that secondary organic aerosols (SOA) are major contributors to ultrafine particle growth to climatically relevant sizes, increasing global cloud condensation nuclei (CCN) concentrations within the continental boundary layer (BL). However, there are three recent developments regarding the condensation of SOA that lead to uncertainties in the contribution of SOA to particle growth and CCN concentrations: (1) while many global models contain only biogenic sources of SOA (with annual production rates generally 10-30 Tg yr(-1)), recent studies have shown that an additional source of SOA around 100 Tg yr(-1) correlated with anthropogenic carbon monoxide (CO) emissions may be required to match measurements. (2) Many models treat SOA solely as semi-volatile, which leads to condensation of SOA proportional to the aerosol mass distribution; however, recent closure studies with field measurements show nucleation mode growth can be captured only if it is assumed that a significant fraction of SOA condenses proportional to the Fuchs-corrected aerosol surface area. This suggests a very low volatility of the condensing vapors. (3) Other recent studies of particle growth show that SOA con-densation at sizes smaller than 10 nm and that size-dependent growth rate parameterizations (GRP) are needed to match measurements. We explore the significance of these three findings using GEOS-Chem-TOMAS global aerosol microphysics model and observations of aerosol size distributions around the globe. The change in the concentration of particles of size D-p > 40 nm (N40) within the BL assuming surface-area condensation compared to mass-distribution net condensation yielded a global increase of 11% but exceeded 100% in biogenically active regions. The percent change in N40 within the BL with the inclusion of the additional 100 Tg SOAyr(-1) compared to the base simulation solely with biogenic SOA emissions (19 Tg yr-1) both using surface area condensation yielded a global increase of 13.7 %, but exceeded 50% in regions with large CO emissions. The inclusion of two different GRPs in the additional-SOA case both yielded a global increase in N40 of < 1 %, however exceeded 5% in some locations in the most extreme case. All of the model simulations were compared to measured data obtained from diverse locations around the globe and the results confirmed a decrease in the model-measurement bias and improved slope for comparing modeled to measured CCN number concentration when non-volatile SOA was assumed and the extra SOA was included.

  • 16. D'Andrea, S. D.
    et al.
    Hakkinen, S. A. K.
    Westervelt, D. M.
    Kuang, C.
    Spracklen, D. V.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pierce, J. R.
    Effect of Secondary Organic Aerosol Amount and Condensational Behavior on Global Aerosol Size Distributions2013In: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, p. 667-670Conference paper (Refereed)
    Abstract [en]

    Recent research has shown that secondary organic aerosols (SOA) are major contributors to ultrafine particle growth to climatically relevant sizes, increasing global cloud condensation nuclei (CCN) concentrations within the continental boundary layer. Many models treat SOA solely as semivolatile, which leads to condensation of SOA proportional to the aerosol mass distribution; however, recent closure studies with field measurements show that a significant fraction of SOA condenses proportional to the aerosol surface area, which suggests a very low volatility. Additionally, while many global models contain only biogenic sources of SOA (with emissions generally 10-30 Tg yr(-1)), recent studies have shown a need for an additional source of SOA around 100 Tg yr(-1) correlated with anthropogenic carbon monoxide (CO) emissions is required to match measurements. Here, we explore the significance of these two findings using the GEOS-Chem-TOMAS global aerosol microphysics model. The percent change in the number of particles of size D-p > 40 nm (N40) within the continental boundary layer between the surface-area-and mass-distribution condensation schemes, both with the base biogenic SOA only, yielded a global increase of 8% but exceeds 100% in biogenically active regions. The percent change in N40 within the continental boundary layer between the base simulation (19 Tg yr(-1)) and the additional SOA (100 Tg yr(-1)) both using the surface area condensation scheme (very low volatility) yielded a global increase of 14%, and a global decrease in the number of particles of size D-p > 10 nm (N10) of 32%. These model simulations were compared to measured data from Hyytiala, Finland and other global locations and confirmed a decrease in the model-measurement bias. Thus, treating SOA as very low volatile as well as including additional SOA correlated with anthropogenic CO emissions causes a significant global increase in the number of climatically relevant sized particles, and therefore we must continue to refine our SOA treatments in aerosol microphysics models.

  • 17. Donahue, Neil M.
    et al.
    Ortega, Ismael K.
    Chuang, Wayne
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Riccobono, Francesco
    Schobesberger, Siegfried
    Dommen, Josef
    Baltensperger, Urs
    Kulmala, Markku
    Worsnop, Douglas R.
    Vehkamäki, Hanna
    How do organic vapors contribute to new-particle formation?2013In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 165, p. 91-104Article in journal (Refereed)
    Abstract [en]

    Highly oxidised organic vapors can effectively stabilize sulphuric acid in heteronuclear clusters and drive new-particle formation. We present quantum chemical calculations of cluster stability, showing that multifunctional species can stabilize sulphuric acid and also present additional polar functional groups for subsequent cluster growth. We also model the multi-generation oxidation of vapors associated with secondary organic aerosol formation using a two-dimensional volatility basis set. The steady-state saturation ratios and absolute concentrations of extremely low volatility products are sufficient to drive new-particle formation with sulphuric acid at atmospherically relevant rates.

  • 18. Donahue, Neil M.
    et al.
    Robinson, Allen L.
    Trump, Erica R.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kroll, Jesse H.
    Volatility and Aging of Atmospheric Organic Aerosol2014In: Atmospheric and aerosol chemistry, Springer, 2014, p. 97-143Chapter in book (Refereed)
    Abstract [en]

    Organic-aerosol phase partitioning (volatility) and oxidative aging are inextricably linked in the atmosphere because partitioning largely controls the rates and mechanisms of aging reactions as well as the actual amount of organic aerosol. Here we discuss those linkages, describing the basic theory of partitioning thermodynamics as well as the dynamics that may limit the approach to equilibrium under some conditions. We then discuss oxidative aging in three forms: homogeneous gas-phase oxidation, heterogeneous oxidation via uptake of gas-phase oxidants, and aqueous-phase oxidation. We present general scaling arguments to constrain the relative importance of these processes in the atmosphere, compared to each other and compared to the characteristic residence time of particles in the atmosphere.

  • 19. Fountoukis, C.
    et al.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    van der Gon, H. A. C. Denier
    Charalampidis, P. E.
    Pilinis, C.
    Wiedensohler, A.
    O'Dowd, C.
    Putaud, J. P.
    Moerman, M.
    Pandis, S. N.
    Simulating ultrafine particle formation in Europe using a regional ctm: contribution of primary emissions versus secondary formation to aerosol number concentrations2012In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 18, p. 8663-8677Article in journal (Refereed)
    Abstract [en]

    A three-dimensional regional chemical transport model (CTM) with detailed aerosol microphysics, PMCAMx-UF, was applied to the European domain to simulate the contribution of direct emissions and secondary formation to total particle number concentrations during May 2008. PMCAMx-UF uses the Dynamic Model for Aerosol Nucleation and the Two-Moment Aerosol Sectional (TOMAS) algorithm to track both aerosol number and mass concentration using a sectional approach. The model predicts nucleation events that occur over scales of hundreds up to thousands of kilometers especially over the Balkans and Southeast Europe. The model predictions were compared against measurements from 7 sites across Europe. The model reproduces more than 70% of the hourly concentrations of particles larger than 10 nm (N-10) within a factor of 2. About half of these particles are predicted to originate from nucleation in the lower troposphere. Regional nucleation is predicted to increase the total particle number concentration by approximately a factor of 3. For particles larger than 100 nm the effect varies from an increase of 20% in the eastern Mediterranean to a decrease of 20% in southern Spain and Portugal resulting in a small average increase of around 1% over the whole domain. Nucleation has a significant effect in the predicted N-50 levels (up to a factor of 2 increase) mainly in areas where there are condensable vapors to grow the particles to larger sizes. A semi-empirical ternary sulfuric acid-ammonia-water parameterization performs better than the activation or the kinetic parameterizations in reproducing the observations. Reducing emissions of ammonia and sulfur dioxide affects certain parts of the number size distribution.

  • 20. Fuzzi, S.
    et al.
    Baltensperger, U.
    Carslaw, K.
    Decesari, S.
    van der Gon, H. Denier
    Facchini, M. C.
    Fowler, D.
    Koren, I.
    Langford, B.
    Lohmann, U.
    Nemitz, E.
    Pandis, S.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Rudich, Y.
    Schaap, M.
    Slowik, J. G.
    Spracklen, D. V.
    Vignati, E.
    Wild, M.
    Williams, M.
    Gilardoni, S.
    Particulate matter, air quality and climate: lessons learned and future needs2015In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, no 14, p. 8217-8299Article in journal (Refereed)
    Abstract [en]

    The literature on atmospheric particulate matter (PM), or atmospheric aerosol, has increased enormously over the last 2 decades and amounts now to some 1500-2000 papers per year in the refereed literature. This is in part due to the enormous advances in measurement technologies, which have allowed for an increasingly accurate understanding of the chemical composition and of the physical properties of atmospheric particles and of their processes in the atmosphere. The growing scientific interest in atmospheric aerosol particles is due to their high importance for environmental policy. In fact, particulate matter constitutes one of the most challenging problems both for air quality and for climate change policies. In this context, this paper reviews the most recent results within the atmospheric aerosol sciences and the policy needs, which have driven much of the increase in monitoring and mechanistic research over the last 2 decades. The synthesis reveals many new processes and developments in the science underpinning climate-aerosol interactions and effects of PM on human health and the environment. However, while airborne particulate matter is responsible for globally important influences on premature human mortality, we still do not know the relative importance of the different chemical components of PM for these effects. Likewise, the magnitude of the overall effects of PM on climate remains highly uncertain. Despite the uncertainty there are many things that could be done to mitigate local and global problems of atmospheric PM. Recent analyses have shown that reducing black carbon (BC) emissions, using known control measures, would reduce global warming and delay the time when anthropogenic effects on global temperature would exceed 2 degrees C. Likewise, cost-effective control measures on ammonia, an important agricultural precursor gas for secondary inorganic aerosols (SIA), would reduce regional eutrophication and PM concentrations in large areas of Europe, China and the USA. Thus, there is much that could be done to reduce the effects of atmospheric PM on the climate and the health of the environment and the human population. A prioritized list of actions to mitigate the full range of effects of PM is currently undeliverable due to shortcomings in the knowledge of aerosol science; among the shortcomings, the roles of PM in global climate and the relative roles of different PM precursor sources and their response to climate and land use change over the remaining decades of this century are prominent. In any case, the evidence from this paper strongly advocates for an integrated approach to air quality and climate policies.

  • 21. Hakkinen, S. A. K.
    et al.
    Aijala, M.
    Lehtipalo, K.
    Junninen, H.
    Backman, J.
    Virkkula, A.
    Nieminen, T.
    Vestenius, M.
    Hakola, H.
    Ehn, M.
    Worsnop, D. R.
    Kulmala, M.
    Petaja, T.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Long-term volatility measurements of submicron atmospheric aerosol in Hyytiala, Finland2012In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 22, p. 10771-10786Article in journal (Refereed)
    Abstract [en]

    The volatility of submicron atmospheric aerosol particles was investigated at a boreal forest site in Hyytiala, Finland from January 2008 to May 2010. These long-term observations allowed for studying the seasonal behavior of aerosol evaporation with a special focus on compounds that remained in the aerosol phase at 280 degrees C. The temperature-response of evaporation was also studied by heating the aerosol sample step-wise to six temperatures ranging from 80 degrees C to 280 degrees C. The mass fraction remaining after heating (MFR) was determined from the measured particle number size distributions before and after heating assuming a constant particle density (1.6 g cm(-3)). On average 19% of the total aerosol mass remained in the particulate phase at 280 degrees C. The particles evaporated less at low ambient temperatures during winter as compared with the warmer months. Black carbon (BC) fraction of aerosol mass correlated positively with the MFR at 280 degrees C, but could not explain it completely: most of the time a notable fraction of this nonvolatile residual was something other than BC. Using additional information on ambient meteorological conditions and results from an Aerodyne aerosol mass spectrometer (AMS), the chemical composition of MFR at 280 degrees C and its seasonal behavior was further examined. Correlation analysis with ambient temperature and mass fractions of polycyclic aromatic hydrocarbons (PAHs) indicated that MFR at 280 degrees C is probably affected by anthropogenic emissions. On the other hand, results from the AMS analysis suggested that there may be very low-volatile organics, possibly organonitrates, in the non-volatile (at 280 degrees C) fraction of aerosol mass.

  • 22. Hakkinen, S. A. K.
    et al.
    Manninen, H. E.
    Yli-Juuti, T.
    Merikanto, J.
    Kajos, M. K.
    Nieminen, T.
    D'Andrea, S. D.
    Asmi, A.
    Pierce, J. R.
    Kulmala, M.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Semi-empirical parameterization of size-dependent atmospheric nanoparticle growth in continental environments2013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 15, p. 7665-7682Article in journal (Refereed)
    Abstract [en]

    The capability to accurately yet efficiently represent atmospheric nanoparticle growth by biogenic and anthropogenic secondary organics is a challenge for current atmospheric large-scale models. It is, however, crucial to predict nanoparticle growth accurately in order to reliably estimate the atmospheric cloud condensation nuclei (CCN) concentrations. In this work we introduce a simple semi-empirical parameterization for sub-20 nm particle growth that distributes secondary organics to the nanoparticles according to their size and is therefore able to reproduce particle growth observed in the atmosphere. The parameterization includes particle growth by sulfuric acid, secondary organics from monoterpene oxidation (SORG(MT)) and an additional condensable vapor of non-monoterpene organics (background). The performance of the proposed parameterization was investigated using ambient data on particle growth rates in three diameter ranges (1.5-3 nm, 3-7 nm and 7-20 nm). The growth rate data were acquired from particle / air ion number size distribution measurements at six continental sites over Europe. The longest time series of 7 yr (2003-2009) was obtained from a boreal forest site in Hyytiala, Finland, while about one year of data (2008-2009) was used for the other stations. The extensive ambient measurements made it possible to test how well the parameterization captures the seasonal cycle observed in sub-20 nm particle growth and to determine the weighing factors for distributing the SORG(MT) for different sized particles as well as the background mass flux (concentration). Besides the monoterpene oxidation products, background organics with a concentration comparable to SORGMT, around 6x10(7) cm(-3) (consistent with an additional global SOA yield of 100 Tg yr(-1)) was needed to reproduce the observed nanoparticle growth. Simulations with global models suggest that the background could be linked to secondary biogenic organics that are formed in the presence of anthropogenic pollution.

  • 23. Hakkinen, Silja A. K.
    et al.
    McNeill, V. Faye
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). University of Helsinki, Finland.
    Effect of Inorganic Salts on the Volatility of Organic Acids2014In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 23, p. 13718-13726Article in journal (Refereed)
    Abstract [en]

    Particulate phase reactions between organic and inorganic compounds may significantly alter aerosol chemical properties, for example, by suppressing particle volatility. Here, chemical processing upon drying of aerosols comprised of organic (acetic, oxalic, succinic, or citric) acid/monovalent inorganic salt mixtures was assessed by measuring the evaporation of the organic acid molecules from the mixture using a novel approach combining a chemical ionization mass spectrometer coupled with a heated flow tube inlet (TPD-CIMS) with kinetic model calculations. For reference, the volatility, i.e. saturation vapor pressure and vaporization enthalpy, of the pure succinic and oxalic acids was also determined and found to be in agreement with previous literature. Comparison between the kinetic model and experimental data suggests significant particle phase processing forming low-volatility material such as organic salts. The results were similar for both ammonium sulfate and sodium chloride mixtures, and relatively more processing was observed with low initial aerosol organic molar fractions. The magnitude of low-volatility organic material formation at an atmospherically relevant pH range indicates that the observed phenomenon is not only significant in laboratory conditions but is also of direct atmospheric relevance.

  • 24. Hennigan, Christopher J.
    et al.
    Westervelt, Daniel M.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Engelhart, Gabriella J.
    Lee, Taehyoung
    Collett, Jeffrey L., Jr.
    Pandis, Spyros N.
    Adams, Peter J.
    Robinson, Allen L.
    New particle formation and growth in biomass burning plumes: An important source of cloud condensation nuclei2012In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 39, p. L09805-Article in journal (Refereed)
    Abstract [en]

    Experiments were performed in an environmental chamber to characterize the effects of photo-chemical aging on biomass burning emissions. Photo-oxidation of dilute exhaust from combustion of 12 different North American fuels induced significant new particle formation that increased the particle number concentration by a factor of four (median value). The production of secondary organic aerosol caused these new particles to grow rapidly, significantly enhancing cloud condensation nuclei (CCN) concentrations. Using inputs derived from these new data, global model simulations predict that nucleation in photo-chemically aging fire plumes produces dramatically higher CCN concentrations over widespread areas of the southern hemisphere during the dry, burning season (Sept.-Oct.), improving model predictions of surface CCN concentrations. The annual indirect forcing from CCN resulting from nucleation and growth in biomass burning plumes is predicted to be -0.2 W m(-2), demonstrating that this effect has a significant impact on climate that has not been previously considered. Citation: Hennigan, C. J., D. M. Westervelt, I. Riipinen, G. J. Engelhart, T. Lee, J. L. Collett Jr., S. N. Pandis, P. J. Adams, and A. L. Robinson (2012), New particle formation and growth in biomass burning plumes: An important source of cloud condensation nuclei, Geophys. Res. Lett., 39, L09805, doi: 10.1029/2012GL050930.

  • 25. Henschel, Henning
    et al.
    Acosta Navarro, Juan Camilo
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Yli-Juuti, Taina
    Kupiainen-Määttä, Oona
    Olenius, Tinja
    Ortega, Ismael K.
    Clegg, Simon L.
    Kurtén, Theo
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Vehkamäki, Hanna
    Hydration of Atmospherically Relevant Molecular Clusters: Computational Chemistry and Classical Thermodynamics2014In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 118, no 14, p. 2599-2611Article in journal (Refereed)
    Abstract [en]

    Formation of new particles through clustering of molecules from condensable vapors is a significant source for atmospheric aerosols. The smallest clusters formed in the very first steps of the condensation process are, however, not directly observable by experimental means. We present here a comprehensive series of electronic structure calculations on the hydrates of clusters formed by up to four molecules of sulfuric acid, and up to two molecules of ammonia or dimethylamine. Though clusters containing ammonia, and certainly dimethylamine, generally exhibit lower average hydration than the pure acid clusters, populations of individual hydrates vary widely. Furthermore, we explore the predictions obtained using a thermodynamic model for the description of these hydrates. The similar magnitude and trends of hydrate formation predicted by both methods illustrate the potential of combining them to obtain more comprehensive models. The stabilization of some clusters relative to others due to their hydration is highly likely to have significant effects on the overall processes that lead to formation of new particles in the atmosphere.

  • 26. Hong, J.
    et al.
    Hakkinen, S. A. K.
    Paramonov, M.
    Aijala, M.
    Hakala, J.
    Nieminen, T.
    Mikkila, J.
    Prisle, N. L.
    Kulmala, M.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bilde, M.
    Kerminen, V. -M
    Petaja, T.
    Hygroscopicity, CCN and volatility properties of submicron atmospheric aerosol in a boreal forest environment during the summer of 20102014In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 14, no 9, p. 4733-4748Article in journal (Refereed)
    Abstract [en]

    A Volatility-Hygroscopicity Tandem Differential Mobility Analyzer (VH-TDMA) was applied to study the hygroscopicity and volatility properties of submicron atmospheric aerosol particles in a boreal forest environment in Hyytiala, Finland during the summer of 2010. Aitken and accumulation mode internally mixed particles (50 nm, 75 nm and 110 nm in diameter) were investigated. Hygroscopicity was found to increase with particle size. The relative mass fraction of organics and SO42- is probably the major contributor to the fluctuation of the hygroscopicity for all particle sizes. The Cloud Condensation Nuclei Counter (CCNC)-derived hygroscopicity parameter kappa was observed to be slightly higher than kappa calculated from VH-TDMA data under sub-saturated conditions, potential reasons for this behavior are discussed shortly. Also, the size-resolved volatility properties of particles were investigated. Upon heating, more small particles evaporated compared to large particles. There was a significant amount of aerosol volume (non-volatile material) left, even at heating temperatures of 280 degrees C. Using size resolved volatility-hygroscopicity analysis, we concluded that there was always hygroscopic material remaining in the particles at different heating temperatures, even at 280 degrees C. This indicates that the observed non-volatile aerosol material did not consist solely of black carbon.

  • 27. Hong, Juan
    et al.
    Äijälä, Mikko
    Häme, Silja A. K.
    Hao, Liqing
    Duplissy, Jonathan
    Heikkinen, Liine M.
    Nie, Wei
    Mikkilä, Jyri
    Kulmala, Markku
    Prisle, Nonne L.
    Virtanen, Annele
    Ehn, Mikael
    Paasonen, Pauli
    Worsnop, Douglas R.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Petäjä, Tuukka
    Kerminen, Veli-Matti
    Estimates of the organic aerosol volatility in a boreal forest using two independent methods2017In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 6, p. 4387-4399Article in journal (Refereed)
    Abstract [en]

    The volatility distribution of secondary organic aerosols that formed and had undergone aging - i. e., the particle mass fractions of semi-volatile, low-volatility and extremely low volatility organic compounds in the particle phase - was characterized in a boreal forest environment of Hyytiala, southern Finland. This was done by interpreting field measurements using a volatility tandem differential mobility analyzer (VTDMA) with a kinetic evaporation model. The field measurements were performed during April and May 2014. On average, 40% of the organics in particles were semi-volatile, 34% were low-volatility organics and 26% were extremely low volatility organics. The model was, however, very sensitive to the vaporization enthalpies assumed for the organics (Delta H-VAP). The best agreement between the observed and modeled temperature dependence of the evaporation was obtained when effective vaporization enthalpy values of 80 kJ mol(-1) were assumed. There are several potential reasons for the low effective enthalpy value, including molecular decomposition or dissociation that might occur in the particle phase upon heating, mixture effects and compound-dependent uncertainties in the mass accommodation coefficient. In addition to the VTDMA-based analysis, semi-volatile and low-volatility organic mass fractions were independently determined by applying positive matrix factorization (PMF) to high-resolution aerosol mass spectrometer (HR-AMS) data. The factor separation was based on the oxygenation levels of organics, specifically the relative abundance of mass ions at m/z 43 (f43) and m/z 44 (f44). The mass fractions of these two organic groups were compared against the VTDMA-based results. In general, the best agreement between the VTDMA results and the PMF-derived mass fractions of organics was obtained when Delta H-VAP D 80 kJ mol(-1) was set for all organic groups in the model, with a linear correlation coefficient of around 0.4. However, this still indicates that only about 16% (R-2)of the variation can be explained by the linear regression between the results from these two methods. The prospect of determining of extremely low volatility organic aerosols (ELVOAs) from AMS data using the PMF analysis should be assessed in future studies.

  • 28.
    Julin, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Eastern Finland, Finland.
    Murphy, Benjamin N.
    Patoulias, David
    Fountoukis, Christos
    Olenius, Tinja
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Pandis, Spyros N.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Impacts of Future European Emission Reductions on Aerosol Particle Number Concentrations Accounting for Effects of Ammonia, Amines, and Organic Species2018In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 52, no 2, p. 692-700Article in journal (Refereed)
    Abstract [en]

    Although they are currently unregulated, atmospheric ultrafine particles (<100 nm) pose health risks because of, e.g., their capability to penetrate deep into the respiratory system. Ultrafine particles, often minor contributors to atmospheric particulate mass, typically dominate aerosol particle number concentrations. We simulated the response of particle number concentrations over Europe to recent estimates of future emission reductions of aerosol particles and their precursors. We used the chemical transport model PMCAMx-UF, with novel updates including state-of-the-art descriptions of ammonia and dimethylamine new particle formation (NPF) pathways and the condensation of organic compounds onto particles. These processes had notable impacts on atmospheric particle number concentrations. All three emission scenarios (current legislation, optimized emissions, and maximum technically feasible reductions) resulted in substantial (10-50%) decreases in median particle number concentrations over Europe. Consistent reductions were predicted in Central Europe, while Northern Europe exhibited smaller reductions or even increased concentrations. Motivated by the improved NPF descriptions for ammonia and methylamines, we placed special focus on the potential to improve air quality by reducing agricultural emissions,, which are a major source of these species. Agricultural emission controls showed promise in reducing ultrafine particle number concentrations, although the change is nonlinear with particle size.

  • 29.
    Julin, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Molecular Dynamics Simulations of Mass Accommodation and Evaporation on Surfaces of Atmospheric Interest2013In: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, p. 437-440Conference paper (Refereed)
    Abstract [en]

    The mass accommodation of condensable gaseous species on to the surfaces of atmospheric aerosols controls the growth of submicron-sized particles to atmospherically relevant sizes. In this work we present results from molecular dynamics simulations of mass accommodation of water and organic molecules on surfaces consisting of the same molecular species.

  • 30.
    Julin, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Shiraiwa, Manabu
    Miles, Rachael E. H.
    Reid, Jonathan P.
    Poschl, Ulrich
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mass Accommodation of Water: Bridging the Gap Between Molecular Dynamics Simulations and Kinetic Condensation Models2013In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, no 2, p. 410-420Article in journal (Refereed)
    Abstract [en]

    The condensational growth of submicrometer aerosol particles to climate relevant sizes is sensitive to their ability to accommodate vapor molecules, which is described by the mass accommodation coefficient. However, the underlying processes are not yet fully understood. We have simulated the mass accommodation and evaporation processes of water using molecular dynamics, and the results are compared to the condensation equations derived from the kinetic gas theory to shed light on the compatibility of the two. Molecular dynamics simulations were performed for a planar TIP4P-Ew water surface at four temperatures in the range 268-300 K as well as two droplets, with radii of 1.92 and 4.14 nm at T = 273.15 K. The evaporation flux from molecular dynamics was found to be in good qualitative agreement with that predicted by the simple kinetic condensation equations. Water droplet growth was also modeled with the kinetic multilayer model KM-GAP of Shiraiwa et al. [Atmos. Chem. Phys. 2012, 12, 2777]. It was found that, due to the fast transport across the interface, the growth of a pure water droplet is controlled by gas phase diffusion. These facts indicate that the simple kinetic treatment is sufficient in describing pure water condensation and evaporation. The droplet size was found to have minimal effect on the value of the mass accommodation coefficient. The mass accommodation coefficient was found to be unity (within 0.004) for all studied surfaces, which is in agreement with previous simulation work. Additionally, the simulated evaporation fluxes imply that the evaporation coefficient is also unity. Comparing the evaporation rates of the mass accommodation and evaporation simulations indicated that the high collision flux, corresponding to high supersaturation, present in typical molecular dynamics mass accommodation simulations can under certain conditions lead to an increase in the evaporation rate. Consequently, in such situations the mass accommodation coefficient can be overestimated, but in the present cases the corrected values were still close to unity with the lowest value at approximate to 10.99.

  • 31.
    Julin, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Winkler, Paul M.
    Donahue, Neil M.
    Wagner, Paul E.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Carnegie Mellon University, USA.
    Near-Unity Mass Accommodation Coefficient of Organic Molecules of Varying Structure2014In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 20, p. 12083-12089Article in journal (Refereed)
    Abstract [en]

    Atmospheric aerosol particles have a significant effect on global climate, air quality, and consequently human health. Condensation of organic vapors is a key process in the growth of nanometer-sized particles to climate relevant sizes. This growth is very sensitive to the mass accommodation coefficient a, a quantity describing the vapor uptake ability of the particles, but knowledge on a of atmospheric organics is lacking. In this work, we have determined a for four organic molecules with diverse structural properties: adipic acid, succinic acid, naphthalene, and nonane. The coefficients are studied using molecular dynamics simulations, complemented with expansion chamber measurements. Our results are consistent with alpha = 1 (indicating nearly perfect accommodation), regardless of the molecular structural properties, the phase state of the bulk condensed phase, or surface curvature. The results highlight the need for experimental techniques capable of resolving the internal structure of nanoparticles to better constrain the accommodation of atmospheric organics.

  • 32. Karnezi, E.
    et al.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pandis, S. N.
    Measuring the atmospheric organic aerosol volatility distribution: a theoretical analysis2014In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, no 9, p. 2953-2965Article in journal (Refereed)
    Abstract [en]

    Organic compounds represent a significant fraction of submicrometer atmospheric aerosol mass. Even if most of these compounds are semi-volatile in atmospheric concentrations, the ambient organic aerosol volatility is quite uncertain. The most common volatility measurement method relies on the use of a thermodenuder (TD). The aerosol passes through a heated tube where its more volatile components evaporate, leaving the less volatile components behind in the particulate phase. The typical result of a thermodenuder measurement is the mass fraction remaining (MFR), which depends, among other factors, on the organic aerosol (OA) vaporization enthalpy and the accommodation coefficient. We use a new method combining forward modeling, introduction of experimental error, and inverse modeling with error minimization for the interpretation of TD measurements. The OA volatility distribution, its effective vaporization enthalpy, the mass accommodation coefficient and the corresponding uncertainty ranges are calculated. Our results indicate that existing TD-based approaches quite often cannot estimate reliably the OA volatility distribution, leading to large uncertainties, since there are many different combinations of the three properties that can lead to similar thermograms. We propose an improved experimental approach combining TD and isothermal dilution measurements. We evaluate this experimental approach using the same model, and show that it is suitable for studies of OA volatility in the lab and the field.

  • 33. Kerminen, V-M
    et al.
    Paramonov, M.
    Anttila, T.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Fountoukis, C.
    Korhonen, H.
    Asmi, E.
    Laakso, L.
    Lihavainen, H.
    Swietlicki, E.
    Svenningsson, B.
    Asmi, A.
    Pandis, S. N.
    Kulmala, M.
    Petaja, T.
    Cloud condensation nuclei production associated with atmospheric nucleation: a synthesis based on existing literature and new results2012In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 24, p. 12037-12059Article in journal (Refereed)
    Abstract [en]

    This paper synthesizes the available scientific information connecting atmospheric nucleation with subsequent cloud condensation nuclei (CCN) formation. We review both observations and model studies related to this topic, and discuss the potential climatic implications. We conclude that CCN production associated with atmospheric nucleation is both frequent and widespread phenomenon in many types of continental boundary layers, and probably also over a large fraction of the free troposphere. The contribution of nucleation to the global CCN budget spans a relatively large uncertainty range, which, together with our poor understanding of aerosol-cloud interactions, results in major uncertainties in the radiative forcing by atmospheric aerosols. In order to better quantify the role of atmospheric nucleation in CCN formation and Earth System behavior, more information is needed on (i) the factors controlling atmospheric CCN production and (ii) the properties of both primary and secondary CCN and their interconnections. In future investigations, more emphasis should be put on combining field measurements with regional and large-scale model studies.

  • 34. Keskinen, H.
    et al.
    Virtanen, A.
    Joutsensaari, J.
    Tsagkogeorgas, G.
    Duplissy, J.
    Schobesberger, S.
    Gysel, M.
    Riccobono, F.
    Slowik, J. G.
    Bianchi, F.
    Yli-Juuti, T.
    Lehtipalo, K.
    Rondo, L.
    Breitenlechner, M.
    Kupc, A.
    Almeida, J.
    Amorim, A.
    Dunne, E. M.
    Downard, A. J.
    Ehrhart, S.
    Franchin, A.
    Kajos, M. K.
    Kirkby, J.
    Kuerten, A.
    Nieminen, T.
    Makhmutov, V.
    Mathot, S.
    Miettinen, P.
    Onnela, A.
    Petaja, T.
    Prapland, A.
    Santos, F. D.
    Schallhart, S.
    Sipila, M.
    Stozhkov, Y.
    Tome, A.
    Vaattovaara, P.
    Wimmer, D.
    Prevot, A.
    Dommen, J.
    Donahue, N. M.
    Flagan, R. C.
    Weingartner, E.
    Viisanen, Y.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hansel, A.
    Curtius, J.
    Kulmala, M.
    Worsnop, D. R.
    Baltensperger, U.
    Wex, H.
    Stratmann, F.
    Laaksonen, A.
    Evolution of Nanoparticle Composition in CLOUD in Presence of Sulphuric Acid, Ammonia and Organics2013In: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, p. 291-294Conference paper (Refereed)
    Abstract [en]

    In this study, we investigate the composition of nucleated nanoparticles formed from sulphuric acid, ammonia, amines, and oxidised organics in the CLOUD chamber experiments at CERN. The investigation is carried out via analysis of the particle hygroscopicity (size range of 15-63 nm), ethanol affinity (15-50nm), oxidation state (<50 nm), and ion composition (few nanometers). The organic volume fraction of particles increased with an increase in particle diameter in presence of the sulphuric acid, ammonia and organics. Vice versa, the sulphuric acid volume fraction decreased when the particle diameter increased. The results provide information on the size-dependent composition of nucleated aerosol particles.

  • 35. Keskinen, H.
    et al.
    Virtanen, A.
    Viisanen, Y.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Laaksonen, A.
    Evolution of particle composition in CLOUD nucleation experiments2013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 11, p. 5587-5600Article in journal (Refereed)
    Abstract [en]

    Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed from these compounds in the CLOUD (Cosmics Leaving Outdoor Droplets) chamber experiments at CERN (Centre europeen pour la recherche nucleaire). The investigation was carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during their growth from sizes of a few nanometers to tens of nanometers was derived from measured hygroscopicity assuming the Zdanovskii-Stokes-Robinson relationship, and compared to values gained from the spectrometers. The ZSR-relationship was also applied to obtain the measured ethanol affinities during the particle growth, which were used to derive the volume fractions of sulphuric acid and the other inorganics (e. g. ammonium salts). In the presence of sulphuric acid and ammonia, particles with a mobility diameter of 150 nm were chemically neutralised to ammonium sulphate. In the presence of oxidation products of pinanediol, the organic volume fraction of freshly nucleated particles increased from 0.4 to similar to 0.9, with an increase in diameter from 2 to 63 nm. Conversely, the sulphuric acid volume fraction decreased from 0.6 to 0.1 when the particle diameter increased from 2 to 50 nm. The results provide information on the composition of nucleated aerosol particles during their growth in the presence of various combinations of sulphuric acid, ammonia, dimethylamine and organic oxidation products.

  • 36. Kim, J.
    et al.
    Ahlm, Lars
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Yli-Juuti, T.
    Lawler, M.
    Keskinen, H.
    Tröstl, J.
    Schobesberger, S.
    Duplissy, J.
    Amorim, A.
    Bianchi, F.
    Donahue, N. M.
    Flagan, R. C.
    Hakala, J.
    Heinritzi, M.
    Jokinen, T.
    Kürten, A.
    Laaksonen, A.
    Lehtipalo, K.
    Miettinen, P.
    Petäjä, T.
    Rissanen, M. P.
    Rondo, L.
    Sengupta, K.
    Simon, M.
    Tomé, A.
    Williamson, C.
    Wimmer, D.
    Winkler, P. M.
    Ehrhart, S.
    Ye, P.
    Kirkby, J.
    Curtius, J.
    Baltensperger, U.
    Kulmala, M.
    Lehtinen, K. E. J.
    Smith, J. N.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Virtanen, A.
    Hygroscopicity of nanoparticles produced from homogeneous nucleation in the CLOUD experiments2016In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 16, no 1, p. 293-304Article in journal (Refereed)
    Abstract [en]

    Sulfuric acid, amines and oxidized organics have been found to be important compounds in the nucleation and initial growth of atmospheric particles. Because of the challenges involved in determining the chemical composition of objects with very small mass, however, the properties of the freshly nucleated particles and the detailed pathways of their formation processes are still not clear. In this study,we focus on a challenging size range, i.e., particles that have grown to diameters of 10 and 15 nm following nucleation, and measure their water uptake. Water uptake is useful information for indirectly obtaining chemical composition of aerosol particles. We use a nanometer-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) at sub-saturated conditions (ca. 90% relative humidity at 293 K) to measure the hygroscopicity of particles during the seventh Cosmics Leaving OUtdoor Droplets (CLOUD7) campaign performed at CERN in 2012. In CLOUD7, the hygroscopicity of nucleated nanoparticles was measured in the presence of sulfuric acid, sulfuric acid-dimethylamine, and sulfuric acid-organics derived from alpha-pinene oxidation. The hygroscopicity parameter kappa decreased with increasing particle size, indicating decreasing acidity of particles. No clear effect of the sulfuric acid concentration on the hygroscopicity of 10 nm particles produced from sulfuric acid and dimethylamine was observed, whereas the hygroscopicity of 15 nm particles sharply decreased with decreasing sulfuric acid concentrations. In particular, when the concentration of sulfuric acid was 5.1 x 10(6) molecules cm(-3) in the gas phase, and the dimethylamine mixing ratio was 11.8 ppt, the measured kappa of 15 nm particles was 0.31 +/- 0.01: close to the value reported for dimethylaminium sulfate (DMAS) (kappa(DMAS) similar to 0.28). Furthermore, the difference in kappa between sulfuric acid and sulfuric acid-dimethylamine experiments increased with increasing particle size. The kappa values of particles in the presence of sulfuric acid and organics were much smaller than those of particles in the presence of sulfuric acid and dimethylamine. This suggests that the organics produced from alpha-pinene ozonolysis play a significant role in particle growth even at 10 nm sizes.

  • 37. Kirkby, Jasper
    et al.
    Duplissy, Jonathan
    Sengupta, Kamalika
    Frege, Carla
    Gordon, Hamish
    Williamson, Christina
    Heinritzi, Martin
    Simon, Mario
    Yan, Chao
    Almeida, João
    Tröstl, Jasmin
    Nieminen, Tuomo
    Ortega, Ismael K.
    Wagner, Robert
    Adamov, Alexey
    Amorim, Antonio
    Bernhammer, Anne-Kathrin
    Bianchi, Federico
    Breitenlechner, Martin
    Brilke, Sophia
    Chen, Xuemeng
    Craven, Jill
    Dias, Antonio
    Ehrhart, Sebastian
    Flagan, Richard C.
    Franchin, Alessandro
    Fuchs, Claudia
    Guida, Roberto
    Hakala, Jani
    Hoyle, Christopher R.
    Jokinen, Tuija
    Junninen, Heikki
    Kangasluoma, Juha
    Kim, Jaeseok
    Krapf, Manuel
    Kürten, Andreas
    Laaksonen, Ari
    Lehtipalo, Katrianne
    Makhmutov, Vladimir
    Mathot, Serge
    Molteni, Ugo
    Onnela, Antti
    Peräkylä, Otso
    Piel, Felix
    Petäjä, Tuukka
    Praplan, Arnaud P.
    Pringle, Kirsty
    Rap, Alexandru
    Richards, Nigel A. D.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Rissanen, Matti P.
    Rondo, Linda
    Sarnela, Nina
    Schobesberger, Siegfried
    Scott, Catherine E.
    Seinfeld, John H.
    Sipilä, Mikko
    Steiner, Gerhard
    Stozhkov, Yuri
    Stratmann, Frank
    Tomé, Antonio
    Virtanen, Annele
    Vogel, Alexander L.
    Wagner, Andrea C.
    Wagner, Paul E.
    Weingartner, Ernest
    Wimmer, Daniela
    Winkler, Paul M.
    Ye, Penglin
    Zhang, Xuan
    Hansel, Armin
    Dommen, Josef
    Donahue, Neil M.
    Worsnop, Douglas R.
    Baltensperger, Urs
    Kulmala, Markku
    Carslaw, Kenneth S.
    Curtius, Joachim
    Ion-induced nucleation of pure biogenic particles2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 533, no 7604, p. 521-526Article in journal (Refereed)
    Abstract [en]

    Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood(1). Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours(2). It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere(3,4), and that ions have a relatively minor role(5). Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded(6,7). Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of a-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.

  • 38. Krieger, Ulrich K.
    et al.
    Siegrist, Franziska
    Marcolli, Claudia
    Emanuelsson, Eva U.
    Gøbel, Freya M.
    Bilde, Merete
    Marsh, Aleksandra
    Reid, Jonathan P.
    Huisman, Andrew J.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Hyttinen, Noora
    Myllys, Nanna
    Kurtén, Theo
    Bannan, Thomas
    Percival, Carl J.
    Topping, David
    A reference data set for validating vapor pressure measurement techniques: homologous series of polyethylene glycols2018In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 11, no 1, p. 49-63Article in journal (Refereed)
    Abstract [en]

    To predict atmospheric partitioning of organic compounds between gas and aerosol particle phase based on explicit models for gas phase chemistry, saturation vapor pressures of the compounds need to be estimated. Estimation methods based on functional group contributions require training sets of compounds with well-established saturation vapor pressures. However, vapor pressures of semivolatile and low-volatility organic molecules at atmospheric temperatures reported in the literature often differ by several orders of magnitude between measurement techniques. These discrepancies exceed the stated uncertainty of each technique which is generally reported to be smaller than a factor of 2. At present, there is no general reference technique for measuring saturation vapor pressures of atmospherically relevant compounds with low vapor pressures at atmospheric temperatures. To address this problem, we measured vapor pressures with different techniques over a wide temperature range for intercomparison and to establish a reliable training set. We determined saturation vapor pressures for the homologous series of polyethylene glycols (H-(O-CH2-CH2)(n)-OH) for n = 3 to n = 8 ranging in vapor pressure at 298 K from 10(-7) to 5 x 10(-2) Pa and compare them with quantum chemistry calculations. Such a homologous series provides a reference set that covers several orders of magnitude in saturation vapor pressure, allowing a critical assessment of the lower limits of detection of vapor pressures for the different techniques as well as permitting the identification of potential sources of systematic error. Also, internal consistency within the series allows outlying data to be rejected more easily. Most of the measured vapor pressures agreed within the stated uncertainty range. Deviations mostly occurred for vapor pressure values approaching the lower detection limit of a technique. The good agreement between the measurement techniques (some of which are sensitive to the mass accommodation coefficient and some not) suggests that the mass accommodation coefficients of the studied compounds are close to unity. The quantum chemistry calculations were about 1 order of magnitude higher than the measurements. We find that extrapolation of vapor pressures from elevated to atmospheric temperatures is permissible over a range of about 100 K for these compounds, suggesting that measurements should be performed best at temperatures yielding the highest-accuracy data, allowing subsequent extrapolation to atmospheric temperatures.

  • 39. Kulmala, Markku
    et al.
    Kontkanen, Jenni
    Junninen, Heikki
    Lehtipalo, Katrianne
    Manninen, Hanna E.
    Nieminen, Tuomo
    Petäjä, Tuukka
    Sipilä, Mikko
    Schobesberger, Siegfried
    Rantala, Pekka
    Franchin, Alessandro
    Jokinen, Tuija
    Järvinen, Emma
    Äijälä, Mikko
    Kangasluoma, Juha
    Hakala, Jani
    Aalto, Pasi P.
    Paasonen, Pauli
    Mikkilä, Jyri
    Vanhanen, Joonas
    Aalto, Juho
    Hakola, Hannele
    Makkonen, Ulla
    Ruuskanen, Taina
    Mauldin, Roy L., III
    Duplissy, Jonathan
    Vehkamäki, Hanna
    Bäck, Jaana
    Kortelainen, Aki
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kurtén, Theo
    Johnston, Murray V.
    Smith, James N.
    Ehn, Mikael
    Mentel, Thomas F.
    Lehtinen, Kari E. J.
    Laaksonen, Ari
    Kerminen, Veli-Matti
    Worsnop, Douglas R.
    Direct Observations of Atmospheric Aerosol Nucleation2013In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 339, no 6122, p. 943-946Article in journal (Refereed)
    Abstract [en]

    Atmospheric nucleation is the dominant source of aerosol particles in the global atmosphere and an important player in aerosol climatic effects. The key steps of this process occur in the sub-2-nanometer (nm) size range, in which direct size-segregated observations have not been possible until very recently. Here, we present detailed observations of atmospheric nanoparticles and clusters down to 1-nm mobility diameter. We identified three separate size regimes below 2-nm diameter that build up a physically, chemically, and dynamically consistent framework on atmospheric nucleation-more specifically, aerosol formation via neutral pathways. Our findings emphasize the important role of organic compounds in atmospheric aerosol formation, subsequent aerosol growth, radiative forcing and associated feedbacks between biogenic emissions, clouds, and climate.

  • 40. Kulmala, Markku
    et al.
    Petaja, Tuukka
    Nieminen, Tuomo
    Sipila, Mikko
    Manninen, Hanna E.
    Lehtipalo, Katrianne
    Dal Maso, Miikka
    Aalto, Pasi P.
    Junninen, Heikki
    Paasonen, Pauli
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Lehtinen, Kari E. J.
    Laaksonen, Ari
    Kerminen, Veli-Matti
    Measurement of the nucleation of atmospheric aerosol particles2012In: Nature Protocols, ISSN 1754-2189, E-ISSN 1750-2799, Vol. 7, no 9, p. 1651-1667Article in journal (Refereed)
    Abstract [en]

    The formation of new atmospheric aerosol particles and their subsequent growth have been observed frequently at various locations all over the world. The atmospheric nucleation rate (or formation rate) and growth rate (GR) are key parameters to characterize the phenomenon. Recent progress in measurement techniques enables us to measure atmospheric nucleation at the size (mobility diameter) of 1.5 (+/- 0.4) nm. The detection limit has decreased from 3 to 1 nm within the past 10 years. In this protocol, we describe the procedures for identifying new-particle-formation (NPF) events, and for determining the nucleation, formation and growth rates during such events under atmospheric conditions. We describe the present instrumentation, best practices and other tools used to investigate atmospheric nucleation and NPF at a certain mobility diameter (1.5, 2.0 or 3.0 nm). The key instruments comprise devices capable of measuring the number concentration of the formed nanoparticles and their size, such as a suite of modern condensation particle counters (CPCs) and air ion spectrometers, and devices for characterizing the pre-existing particle number concentration distribution, such as a differential mobility particle sizer (DMPS). We also discuss the reliability of the methods used and requirements for proper measurements and data analysis. The time scale for realizing this procedure is 1 year.

  • 41. Kyro, E. -M
    et al.
    Vaananen, R.
    Kerminen, V. -M
    Virkkula, A.
    Petaja, T.
    Asmi, A.
    Dal Maso, M.
    Nieminen, T.
    Juhola, S.
    Shcherbinin, A.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Lehtipalo, K.
    Keronen, P.
    Aalto, P. P.
    Hari, P.
    Kulmala, M.
    Trends in new particle formation in eastern Lapland, Finland: effect of decreasing sulfur emissions from Kola Peninsula2014In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 14, no 9, p. 4383-4396Article in journal (Refereed)
    Abstract [en]

    The smelter industry in Kola Peninsula is the largest source of anthropogenic SO2 in the Arctic part of Europe and one of the largest within the Arctic domain. Due to socio-economic changes in Russia, the emissions have been decreasing especially since the late 1990s resulting in decreased SO2 concentrations close to Kola in eastern Lapland, Finland. At the same time, the frequency of new particle formation days has been decreasing distinctively at SMEAR I station in eastern Lapland, especially during spring and autumn. We show that sulfur species, namely sulfur dioxide and sulfuric acid, have an important role in both new particle formation and subsequent growth and that the decrease in new particle formation days is a result of the reduction of sulfur emissions originating from Kola Peninsula. In addition to sulfur species, there are many other quantities, such as formation rate of aerosol particles, condensation sink and nucleation mode particle number concentration, which are related to the number of observed new particle formation (NPF) days and need to be addressed when linking sulfur emissions and NPF. We show that while most of these quantities exhibit statistically significant trends, the reduction in Kola sulfur emissions is the most obvious reason for the rapid decline in NPF days. Sulfuric acid explains approximately 20-50% of the aerosol condensational growth observed at SMEAR I, and there is a large seasonal variation with highest values obtained during spring and autumn. We found that (i) particles form earlier after sunrise during late winter and early spring due to high concentrations of SO2 and H2SO4; (ii) several events occurred during the absence of light, and they were connected to higher than average concentrations of SO2; and (iii) high SO2 concentrations could advance the onset of nucleation by several hours. Moreover, air masses coming over Kola Peninsula seemed to favour new particle formation.

  • 42. Kyro, Ella-Maria
    et al.
    Vaananen, Riikka
    Dal Maso, Miikka
    Kerminen, Veli-Matti
    Virkkula, Aki
    Nieminen, Tuomo
    Petaja, Tuukka
    Aalto, Pasi P.
    Keronen, Petri
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hari, Pertti
    Kulmala, Markku
    Long-term Aerosol and Trace Gas Measurements in Eastern Lapland, Finland: The Impact of Kola Air Pollution to New Particle Formation2013In: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, p. 409-412Conference paper (Refereed)
    Abstract [en]

    Sulfur emissions from the Kola Peninsula smelter industry have been decreasing over the past two decades. We investigated the effect of this to new particle formation at SMEAR I station in Eastern Lapland, Finland, using long-term measurements of trace gases and aerosol size distributions. We show that the number of events per year has decreased and can be linked with the decreasing sulfur emissions from Kola.

  • 43. Lawler, Michael J.
    et al.
    Winkler, Paul M.
    Kim, Jaeseok
    Ahlm, Lars
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Trostl, Jasmin
    Praplan, Arnaud P.
    Schobesberger, Siegfried
    Kuerten, Andreas
    Kirkby, Jasper
    Bianchi, Federico
    Duplissy, Jonathan
    Hansel, Armin
    Jokinen, Tuija
    Keskinen, Helmi
    Lehtipalo, Katrianne
    Leiminger, Markus
    Petaja, Tuukka
    Rissanen, Matti
    Rondo, Linda
    Simon, Mario
    Sipila, Mikko
    Williamson, Christina
    Wimmer, Daniela
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Virtanen, Annele
    Smith, James N.
    Unexpectedly acidic nanoparticles formed in dimethylamine-ammonia-sulfuric-acid nucleation experiments at CLOUD2016In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 16, no 21, p. 13601-13618Article in journal (Refereed)
    Abstract [en]

    New particle formation driven by acid-base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10-30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models, which predict a higher dimethylaminium fraction when NH3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : acid ratios lower than 1 : 1. The lowest base fractions were found in particles below 15 nm VMD, with a strong size-dependent composition gradient. The reasons for the very acidic composition remain uncertain, but a plausible explanation is that the particles did not reach thermodynamic equilibrium with respect to the bases due to rapid heterogeneous conversion of SO2 to sulfate. These results indicate that sulfuric acid does not require stabilization by ammonium or dimethylaminium as acid-base pairs in particles as small as 10 nm.

  • 44. Lehtipalo, Katrianne
    et al.
    Rondo, Linda
    Kontkanen, Jenni
    Schobesberger, Siegfried
    Jokinen, Tuija
    Sarnela, Nina
    Kürten, Andreas
    Ehrhart, Sebastian
    Franchin, Alessandro
    Nieminen, Tuomo
    Riccobono, Francesco
    Sipilä, Mikko
    Yli-Juuti, Taina
    Duplissy, Jonathan
    Adamov, Alexey
    Ahlm, Lars
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Almeida, Joao
    Amorim, Antonio
    Bianchi, Federico
    Breitenlechner, Martin
    Dommen, Josef
    Downard, Andrew J.
    Dunne, Eimear M.
    Flagan, Richard C.
    Guida, Roberto
    Hakala, Jani
    Hansel, Armin
    Jud, Werner
    Kangasluoma, Juha
    Kerminen, Veli-Matti
    Keskinen, Helmi
    Kim, Jaeseok
    Kirkby, Jasper
    Kupc, Agnieszka
    Kupiainen-Määttä, Oona
    Laaksonen, Ari
    Lawler, Michael J.
    Leiminger, Markus
    Mathot, Serge
    Olenius, Tinja
    Ortega, Ismael K.
    Onnela, Antti
    Petäjä, Tuukka
    Praplan, Arnaud
    Rissanen, Matti P.
    Ruuskanen, Taina
    Santos, Filipe D.
    Schallhart, Simon
    Schnitzhofer, Ralf
    Simon, Mario
    Smith, James N.
    Tröstl, Jasmin
    Tsagkogeorgas, Georgios
    Tome, Antonio
    Vaattovaara, Petri
    Vehkamäki, Hanna
    Vrtala, Aron E.
    Wagner, Paul E.
    Williamson, Christina
    Wimmer, Daniela
    Winkler, Paul M.
    Virtanen, Annele
    Donahue, Neil M.
    Carslaw, Kenneth S.
    Baltensperger, Urs
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Curtius, Joachim
    Worsnop, Douglas R.
    Kulmala, Markku
    The effect of acid-base clustering and ions on the growth of atmospheric nano-particles2016In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 11594Article in journal (Refereed)
    Abstract [en]

    The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

  • 45. Lehtipalo, Katrianne
    et al.
    Schobesberger, Siegfried
    Sipila, Mikko
    Jokinen, Tuija
    Sarnela, Nina
    Franchin, Alessandro
    Nieminen, Tuomo
    Riccobono, Francesco
    Duplissy, Jonathan
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kulmala, Markku
    Worsnop, Douglas
    How Do Amines Affect the Growth of Recently Formed Aerosol Particles2013In: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, p. 295-297Conference paper (Refereed)
    Abstract [en]

    Growth rates of recently born nanometer-scale particles were measured during the CLOUD experiments at CERN. Combining the data from several recently developed measurement techniques allowed us to follow the growth of the particles starting from molecules to molecular clusters and finally to climatically relevant particles. We studied the binary system with sulphuric acid and water, and the ternary systems with ammonia or dimethylamine added to the chamber, both in purely neutral situation, and with ionization from cosmic rays or the CERN particle beam.

  • 46. Listowski, C.
    et al.
    Maeaettaenen, A.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Montmessin, F.
    Lefevre, F.
    Near-pure vapor condensation in the Martian atmosphere: CO2 ice crystal growth2013In: Journal of geophysical research - planets, ISSN 2169-9097, Vol. 118, no 10, p. 2153-2171Article in journal (Refereed)
    Abstract [en]

    A new approach is presented to model the condensational growth of carbon dioxide (CO2) ice crystals on Mars. These condensates form in very particular conditions. First, approximate to 95% of the atmosphere is composed of CO2 so that near-pure vapor condensation takes place. Second, the atmosphere is rarefied, having dramatic consequences on the crystal growth. Indeed, the subsequently reduced efficiency of heat transport helps maintain a high temperature difference between the crystal surface and the environment, inhibiting the growth. Besides, the Stefan flow which would have been expected to increase the growth rate of the crystal, because of the near-pure vapor condensation, is negligible. We show that the heritage of the convenient and explicit linearized crystal growth rate formula used for Earth clouds, initially derived for a trace gas, has to be reconsidered in the case of near-pure vapor condensation for high saturation ratios that appear to be common in the Martian mesosphere. Nevertheless, by comparing our approach with a more complex condensation model, valid for all atmospheric conditions and all vapor abundances, we show that a very simple set of equations can still be used to efficiently reproduce the CO2 ice crystal growth rate. Our model, referred to as the CLASSIC model here, provides similar crystal growth rates than the traditionally used linearized growth rate models at low supersaturations but predicts lower crystal growth rates at high supersaturations. It can thus be used to model the condensational growth of CO2 ice crystals in the mesosphere where high supersaturations are observed.

  • 47.
    Matisans, Modris
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Tunved, Peter
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Hamburger, Thomas
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Manninen, Hanna E.
    Backman, John
    Rizzo, Luciana
    Artaxo, Paulo
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Swietlicki, Erik
    Krejci, Radovan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kulmala, Markku
    New Aerosol Particle Formation in Amazonia2013In: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, p. 571-574Conference paper (Refereed)
    Abstract [en]

    Particle nucleation in Amazonia has been an enigma throughout decades of active scrutiny of natural nucleation processes; however, measurements have so far been thought to fail capturing an actual new particle formation (NPF) event. In this study we have analyzed latest measurements of ultra-fine particle size distributions alongside with air ion spectra and revealed a diurnal pattern of ultra-fine particle apparent growth. The revealed growth pattern is preceded by diurnal precipitation probability maxima, and simultaneous abundant ion production as detected by Neutral cluster and Air Ion Spectrometer (NAIS) data. Thus, we claim that by implementing statistical analysis of scanning mobility particle sizer (SMPS) data and combining with independent observations from Neutral cluster and Air Ion Spectrometer (NAIS) we can observe a consistent signal of NPF events in Amazonia.

  • 48. May, Andrew A.
    et al.
    Levin, Ezra J. T.
    Hennigan, Christopher J.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Lee, Taehyoung
    Collett, Jeffrey L., Jr.
    Jimenez, Jose L.
    Kreidenweis, Sonia M.
    Robinson, Allen L.
    Gas-particle partitioning of primary organic aerosol emissions: 3. Biomass burning2013In: Journal of Geophysical Research: Atmospheres, ISSN 2169-897X, Vol. 118, no 19, p. 11327-11338Article in journal (Refereed)
    Abstract [en]

    Atmospheric organic aerosol concentrations depend in part on the gas-particle partitioning of primary organic aerosol (POA) emissions. Consequently, heating and dilution were used to investigate the volatility of biomass-burning smoke particles from combustion of common North American trees/shrubs/grasses during the third Fire Lab at Missoula Experiment. Fifty to eighty percent of the mass of biomass-burning POA evaporated when isothermally diluted from plume- (~1000 µg m−3) to ambient-like concentrations (~10 µg m−3), while roughly 80% of the POA evaporated upon heating to 100°C in a thermodenuder with a residence time of ~14 sec. Therefore, the majority of the POA emissions were semivolatile. Thermodenuder measurements performed at three different residence times indicated that there were not substantial mass transfer limitations to evaporation (i.e., the mass accommodation coefficient appears to be between 0.1 and 1). An evaporation kinetics model was used to derive volatility distributions and enthalpies of vaporization from the thermodenuder data. A single volatility distribution can be used to represent the measured gas-particle partitioning from the entire set of experiments, including different fuels, organic aerosol concentrations, and thermodenuder residence times. This distribution, derived from the thermodenuder measurements, also predicts the dilution-driven changes in gas-particle partitioning. This volatility distribution and associated emission factors for each fuel studied can be used to update emission inventories and to simulate the gas-particle partitioning of biomass-burning POA emissions in chemical transport models.

  • 49. Miles, Rachael E. H.
    et al.
    Reid, Jonathan P.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Comparison of Approaches for Measuring the Mass Accommodation Coefficient for the Condensation of Water and Sensitivities to Uncertainties in Thermophysical Properties2012In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 116, no 44, p. 10810-10825Article in journal (Refereed)
    Abstract [en]

    We compare and contrast measurements of the mass accommodation coefficient of water on a water surface made using ensemble and single particle techniques under conditions of supersaturation and subsaturation, respectively. In particular, we consider measurements made using an expansion chamber, a continuous flow streamwise thermal gradient cloud condensation nuclei chamber, the Leipzig Aerosol Cloud Interaction Simulator, aerosol optical tweezers, and electrodynamic balances. Although this assessment is not intended to be comprehensive, these five techniques are complementary in their approach and give values that span the range from near 0.1 to 1.0 for the mass accommodation coefficient. We use the same semianalytical treatment to assess the sensitivities of the measurements made by the various techniques to thermophysical quantities (diffusion constants, thermal conductivities, saturation pressure of water, latent heat, and solution density) and experimental parameters (saturation value and temperature). This represents the first effort to assess and compare measurements made by different techniques to attempt to reduce the uncertainty in the value of the mass accommodation coefficient. Broadly, we show that the measurements are consistent within the uncertainties inherent to the thermophysical and experimental parameters and that the value of the mass accommodation coefficient should be considered to be larger than 0.5. Accurate control and measurement of the saturation ratio is shown to be critical for a successful investigation of the surface transport kinetics during condensation/evaporation. This invariably requires accurate knowledge of the partial pressure of water, the system temperature, the droplet curvature and the saturation pressure of water. Further, the importance of including and quantifying the transport of heat in interpreting droplet measurements is highlighted; the particular issues associated with interpreting measurements of condensation/evaporation rates with varying pressure are discussed, measurements that are important for resolving the relative importance of gas diffusional transport and surface kinetics.

  • 50.
    Murphy, Benjamin N.
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology . Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Julin, Jan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ekman, Annica M. L.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Organic aerosol processing in tropical deep convective clouds: Development of a new model (CRM-ORG) and implications for sources of particle number2015In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 120, no 19Article in journal (Refereed)
    Abstract [en]

    The difficulty in assessing interactions between atmospheric particles and clouds is due in part to the chemical complexity of the particles and to the wide range of length and timescales of processes occurring simultaneously during a cloud event. The new Cloud-Resolving Model with Organics (CRM-ORG) addresses these interactions by explicitly predicting the formation, transport, uptake, and re-release of surrogate organic compounds consistent with the volatility basis set framework within a nonhydrostatic, three-dimensional cloud-resolving model. CRM-ORG incorporates photochemical production, explicit condensation/evaporation of organic and inorganic vapors, and a comprehensive set of four different mechanisms describing particle formation from organic vapors and sulfuric acid. We simulate two deep convective cloud events over the Amazon rain forest in March 1998 and compare modeled particle size distributions with airborne observations made during the time period. The model predictions agree well with the observations for Aitken mode particles in the convective outflow (10-14 km) but underpredict nucleation mode particles by a factor of 20. A strong in-cloud particle formation process from organic vapors alone is necessary to reproduce even relatively low ultrafine particle number concentrations (similar to 1500 cm(-3)). Sensitivity tests with variable initial aerosol loading and initial vertical aerosol profile demonstrate the complexity of particle redistribution and net gain or loss in the cloud. In-cloud particle number concentrations could be enhanced by as much as a factor of 3 over the base case simulation in the cloud outflow but were never reduced by more than a factor of 2 lower than the base. Additional sensitivity cases emphasize the need for constrained estimates of surface tension and affinity of organic vapors to ice surfaces. When temperature-dependent organic surface tension is introduced to the new particle formation mechanisms, the number concentration of particles decreases by 60% in the cloud outflow. These uncertainties are discussed in light of the other prominent challenges for understanding the interactions between organic aerosols and clouds. Recommendations for future theoretical, laboratory, and field work are proposed.

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