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  • 1. Baranizadeh, Elham
    et al.
    Murphy, Benjamin N.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Julin, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi. University of Eastern Finland, Finland.
    Falahat, Saeed
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Reddington, Carly L.
    Arola, Antti
    Ahlm, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Mikkonen, Santtu
    Fountoukis, Christos
    Patoulias, David
    Minikin, Andreas
    Hamburger, Thomas
    Laaksonen, Ari
    Pandis, Spyros N.
    Vehkamäki, Hanna
    Lehtinen, Kari E. J.
    Riipinen, Ilona
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Implementation of state-of-the-art ternary new-particle formation scheme to the regional chemical transport model PMCAMx-UF in Europe2016Ingår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 9, nr 8, s. 2741-2754Artikel i tidskrift (Refereegranskat)
    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.

  • 2.
    Crljenica, Ivica
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Yli-Juuti, Taina
    Zardini, Alessandro A.
    Julin, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Bilde, Merete
    Riipinen, Ilona
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Center for Atmospheric Particle Studies, Carnegie Mellon University.
    Determining the saturation vapour pressures of keto-dicarboxylic acids in aqueous solutions2013Ingår i: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, s. 468-471Konferensbidrag (Refereegranskat)
    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.

  • 3.
    Julin, Jan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Riipinen, Ilona
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Molecular Dynamics Simulations of Mass Accommodation and Evaporation on Surfaces of Atmospheric Interest2013Ingår i: NUCLEATION AND ATMOSPHERIC AEROSOLS, American Institute of Physics (AIP), 2013, s. 437-440Konferensbidrag (Refereegranskat)
    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.

  • 4.
    Julin, Jan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Shiraiwa, Manabu
    Miles, Rachael E. H.
    Reid, Jonathan P.
    Poschl, Ulrich
    Riipinen, Ilona
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Mass Accommodation of Water: Bridging the Gap Between Molecular Dynamics Simulations and Kinetic Condensation Models2013Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, nr 2, s. 410-420Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Julin, Jan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Winkler, Paul M.
    Donahue, Neil M.
    Wagner, Paul E.
    Riipinen, Ilona
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Carnegie Mellon University, USA.
    Near-Unity Mass Accommodation Coefficient of Organic Molecules of Varying Structure2014Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, nr 20, s. 12083-12089Artikel i tidskrift (Refereegranskat)
    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.

  • 6.
    Murphy, Benjamin N.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU). Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Julin, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Riipinen, Ilona
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Ekman, Annica M. L.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Organic aerosol processing in tropical deep convective clouds: Development of a new model (CRM-ORG) and implications for sources of particle number2015Ingår i: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 120, nr 19Artikel i tidskrift (Refereegranskat)
    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.

  • 7. Vehkamaki, Hanna
    et al.
    McGrath, Matthew J.
    Kurten, Theo
    Julin, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Lehtinen, Kari E. J.
    Kulmala, Markku
    Rethinking the application of the first nucleation theorem to particle formation2012Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 136, nr 9, s. 094107-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The critical cluster is the threshold size above which a cluster will be more likely to grow than to evaporate. In field and laboratory measurements of new particle formation, the number of molecules of a given species in the critical cluster is commonly taken to be the slope of the log-log plot of the formation rate versus the concentration of the species. This analysis is based on an approximate form of the first nucleation theorem, which is derived with the assumption that there are no minima in the free energy surface prior to the maximum at the critical size. However, many atmospherically relevant systems are likely to exhibit such minima, for example, ions surrounded by condensable vapour molecules or certain combinations of acids and bases. We have solved numerically the birth-death equations for both an electrically neutral one-component model system with a local minimum at pre-critical sizes and an ion-induced case. For the ion-induced case, it is verified that the log-log slope of the nucleation rate versus particle concentration plot gives accurately the difference between the cluster sizes at the free energy maximum and minimum, as is expected from the classical form of the ion-induced nucleation rate. However, the results show that applying the nucleation theorem to neutral systems with stable pre-nucleation clusters may lead to erroneous interpretations about the nature of the critical cluster. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3689227]

  • 8. Werner, Josephina
    et al.
    Julin, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Dalirian, Maryam
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Prisle, Nonne L.
    Öhrwall, Gunnar
    Persson, Ingmar
    Björneholm, Olle
    Riipinen, Ilona
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM). Carnegie Mellon University, USA.
    Succinic acid in aqueous solution: connecting microscopic surface composition and macroscopic surface tension2014Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, nr 39, s. 21486-21495Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The water vapor interface of aqueous solutions of succinic acid, where pH values and bulk concentrations were varied, has been studied using surface sensitive X-ray photoelectron spectroscopy (XPS) and molecular dynamics (MD) simulations. It was found that succinic acid has a considerably higher propensity to reside in the aqueous surface region than its deprotonated form, which is effectively depleted from the surface due to the two strongly hydrated carboxylate groups. From both XPS experiments and MD simulations a strongly increased concentration of the acid form in the surface region compared to the bulk concentration was found and quantified. Detailed analysis of the surface of succinic acid solutions at different bulk concentrations led to the conclusion that succinic acid saturates the aqueous surface at high bulk concentrations. With the aid of MD simulations the thickness of the surface layer could be estimated, which enabled the quantification of surface concentration of succinic acid as a multiple of the known bulk concentration. The obtained enrichment factors were successfully used to model the surface tension of these binary aqueous solutions using two different models that account for the surface enrichment. This underlines the close correlation of increased concentration at the surface relative to the bulk and reduced surface tension of aqueous solutions of succinic acid. The results of this study shed light on the microscopic origin of surface tension, a macroscopic property. Furthermore, the impact of the results from this study on atmospheric modeling is discussed.

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