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Aerosol Dynamics

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Markku Kulmala – One of the best experts on this subject based on the ideXlab platform.

Michael Boy – One of the best experts on this subject based on the ideXlab platform.

  • TEMPORARY REMOVAL: Aerosol Dynamics simulations of the anatomical variability of e-cigarette particle and vapor deposition in a stochastic lung
    Journal of Aerosol Science, 2020
    Co-Authors: Lukas Pichelstorfer, Michael Boy, Renate Winkler-heil, Werner Hofmann
    Abstract:

    Abstract Electronic cigarette (EC) Aerosols are typically composed of a mixture of nicotine, glycerine (VG), propylene glycglycol (PG), water, acidic stabilizers and a variety of flavors. Inhalation of e-cigarette Aerosols is characterized by a continuous modification of particle diameters, concentrations, composition and phase changes, and smoker-specific inhalation conditions, i.e. puffing, mouth-hold and bolus inhalation. The dynamic changes of inhaled e-cigarette droplets in the lungs due to coagulation, conductive heat and diffusive heat/convective vapor transport and particle phase chemistry are described by the Aerosol Dynamics in Containment (ADiC) model. For the simulation of the variability of inhaled particle and vapor deposition, the ADiC model is coupled with the IDEAL Monte Carlo code, which is based on a stochastic, asymmetric airway model of the human lung. We refer to the coupled model as “IDEAL/ADIC_v1.0”. In this study, two different e-cigarettes were compared, one without any acid (“no acid”) and the other one with an acidic regulator (benzoic acid) to establish an initial pH level of about 7 (“lower pH”). Corresponding deposition patterns among human airways comprise total and compound-specific number and mass deposition fractions, distinguishing between inhalation and exhalation phases and condensed and vapor phases. Note that the inhaled EC Aerosol is significantly modified in the oral cavity prior to inhalation into the lungs. Computed deposition fractions demonstrate that total particle mass is preferentially deposited in the alveolar region of the lung during inhalation. While nicotine deposits prevalently in the condensed phase for the “lower pH” case, vapor phase deposition is dominating the “no acid” case. The significant statistical fluctuations of the particle and vapor deposition patterns illustrate the inherent anatomical variability of the human lung structure.

  • Aerosol Dynamics within and above forest in relation to turbulent transport and dry deposition
    Atmospheric Chemistry and Physics, 2015
    Co-Authors: Ullar Rannik, Luxi Zhou, Putian Zhou, Rosa Gierens, Ivan Mammarella, Andrey Sogachev, Michael Boy
    Abstract:

    Abstract. A 1-D atmospheric boundary layer (ABL) model coupled with a detailed atmospheric chemistry and Aerosol dynamical model, the model SOSAA, was used to predict the ABL and detailed Aerosol population (characterized by the number size distribution) time evolution. The model was applied over a period of 10 days in May 2013 to a pine forest site in southern Finland. The period was characterized by frequent new particle formation events and simultaneous intensive Aerosol transformation. The aim of the study was to analyze and quantify the role of Aerosol and ABL Dynamics in the vertical transport of Aerosols. It was of particular interest to what extent the fluxes above the canopy deviate from the particle dry deposition on the canopy foliage due to the above-mentioned processes. The model simulations revealed that the particle concentration change due to Aerosol Dynamics frequently exceeded the effect of particle deposition by even an order of magnitude or more. The impact was, however, strongly dependent on particle size and time. In spite of the fact that the timescale of turbulent transfer inside the canopy is much smaller than the timescales of Aerosol Dynamics and dry deposition, leading us to assume well-mixed properties of air, the fluxes at the canopy top frequently deviated from deposition inside the forest. This was due to transformation of Aerosol concentration throughout the ABL and resulting complicated pattern of vertical transport. Therefore we argue that the comparison of timescales of Aerosol Dynamics and deposition defined for the processes below the flux measurement level do not unambiguously describe the importance of Aerosol Dynamics for vertical transport above the canopy. We conclude that under dynamical conditions reported in the current study the micrometeorological particle flux measurements can significantly deviate from the dry deposition into the canopy. The deviation can be systematic for certain size ranges so that the time-averaged particle fluxes can be also biased with respect to deposition sink.

  • Aerosol Dynamics within and above forest in relation to turbulent transport and dry deposition
    , 2015
    Co-Authors: Ullar Rannik, Luxi Zhou, Putian Zhou, Rosa Gierens, Ivan Mammarella, Andrey Sogachev, Michael Boy
    Abstract:

    Abstract. One dimensional atmospheric boundary layer (ABL) model coupled with detailed atmospheric chemistry and Aerosol dynamical model, the model SOSAA, was used to predict the ABL and detailed Aerosol population (characterized by the number size distribution) time evolution. The model was applied over a period of ten days in May 2013 for a pine forest site in southern Finland. The period was characterized by frequent new particle formation events and simultaneous intensive Aerosol transformation. Throughout this study we refer to nucleation, condensational growth and coagulation as Aerosol dynamical processes, i.e. the processes that govern the particle size distribution evolution. The aim of the study was to analyze and quantify the role of Aerosol and ABL Dynamics in vertical transport of Aerosols. It was of particular interest to what extent the fluxes above canopy deviate due to above mentioned processes from the particle dry deposition on the canopy foliage. The model simulations revealed that the particle concentration change due to Aerosol Dynamics can frequently exceed the effect of particle deposition even an order of magnitude or more. The impact is however strongly dependent on particle size and time. In spite of the fact that the time scale of turbulent transfer inside canopy is much smaller than the time scales of Aerosol Dynamics and dry deposition, letting to assume well mixed properties of air, the fluxes at the canopy top frequently deviate from deposition inside forest. This is due to transformation of Aerosol concentration throughout the ABL and resulting complicated pattern of vertical transport. Therefore we argue that the comparison of time scales of Aerosol Dynamics and deposition defined for the processes below the flux measurement level do not unambiguously describe the importance of Aerosol Dynamics for vertical transport within canopy. We conclude that under dynamical conditions the micrometeorological particle flux measurements such as performed by the eddy covariance technique do not generally represent the dry deposition. The deviation can be systematic for certain size ranges so that the conclusion applies also to time averaged particle fluxes.

Kari E J Lehtinen – One of the best experts on this subject based on the ideXlab platform.

  • Development and evaluation of the Aerosol Dynamics and gas phase chemistry model ADCHEM
    Atmospheric Chemistry and Physics, 2011
    Co-Authors: Pontus Roldin, Kari E J Lehtinen, Erik Swietlicki, Michael Boy, Guy Schurgers, Almut Arneth, Markku Kulmala
    Abstract:

    Abstract. The aim of this work was to develop a model suited for detailed studies of Aerosol Dynamics, gas and particle phase chemistry within urban plumes, from local scale (1 × 1 km2) to regional scale. This article describes and evaluates the trajectory model for Aerosol Dynamics, gas and particle phase CHEMistry and radiative transfer (ADCHEM). The model treats both vertical and horizontal dispersion perpendicular to an air mass trajectory (2-space dimensions). The Lagrangian approach enables a more detailed representation of the Aerosol Dynamics, gas and particle phase chemistry and a finer spatial and temporal resolution compared to that of available regional 3D-CTMs. These features make it among others well suited for urban plume studies. The Aerosol Dynamics model includes Brownian coagulation, dry deposition, wet deposition, in-cloud processing, condensation, evaporation, primary particle emissions and homogeneous nucleation. The organic mass partitioning was either modeled with a 2-dimensional volatility basis set (2D-VBS) or with the traditional two-product model approach. In ADCHEM these models consider the diffusion limited and particle size dependent condensation and evaporation of 110 and 40 different organic compounds respectively. The gas phase chemistry model calculates the gas phase concentrations of 61 different species, using 130 different chemical reactions. Daily isoprene and monoterpene emissions from European forests were simulated separately with the vegetation model LPJ-GUESS, and included as input to ADCHEM. ADCHEM was used to simulate the ageing of the urban plumes from the city of Malmo in southern Sweden (280 000 inhabitants). Several sensitivity tests were performed concerning the number of size bins, size structure method, Aerosol dynamic processes, vertical and horizontal mixing, coupled or uncoupled condensation and the secondary organic Aerosol formation. The simulations show that the full-stationary size structure gives accurate results with little numerical diffusion when more than 50 size bins are used between 1.5 and 2500 nm, while the moving-center method is preferable when only a few size bins are selected. The particle number size distribution in the center of the urban plume from Malmo was mainly affected by dry deposition, coagulation and vertical dilution. The modeled PM2.5 mass was dominated by organic material, nitrate, sulfate and ammonium. If the condensation of HNO3 and NH3 was treated as a coupled process (pH independent) the model gave lower nitrate PM2.5 mass than if considering uncoupled condensation. Although the time of ageing from that SOA precursors are emitted until condensable products are formed is substantially different with the 2D-VBS and two product model, the models gave similar total organic mass concentrations.

  • An Aerosol Dynamics model for simulating particle formation and growth in a mixed flow chamber
    , 2011
    Co-Authors: M. Vesterinen, Hannele Korhonen, Jorma Joutsensaari, Pasi Yli-pirilä, Ari Laaksonen, Kari E J Lehtinen
    Abstract:

    Abstract. In this work we model the Aerosol size distribution Dynamics in a mixed flow chamber in which new particles are formed via nucleation and subsequent condensation of oxidation products of VOCs emitted from Norway spruspruce seedlings. The microphysical processes included in the model are nucleation, condensation, deposition and coagulation. The Aerosol Dynamics in the chamber is a competition between Aerosol growth and scavenging/deposition which results in a cyclic particle formation process. With a simple 1-product model, in which the formed gas is able to both condense to the particles and nucleate, we are able to catch both the oscillatory features of the particle formation process and the evolution of the number concentration in a reasonable way. The gas-phase chemistry was adjusted using pre-estimated reaction rate constant in the simulations and the particle depodeposition rate as a function of size was determined experimentally. Despite this, some of the essential features of the physical properties of the Aerosol population could still be captured and investigated without the detailed knowledge of the physical processes underlying the problem by using the constructed model. The size dependency of the wall loss coefficient was investigated using a slightly modified measurement set-up.

  • Aerosol Dynamics simulations on the connection of sulphuric acid and new particle formation
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: S.-l. Sihto, Henri Vuollekoski, Johannes Leppä, Ilona Riipinen, Veli Matti Kerminen, Hannu Korhonen, Kari E J Lehtinen, Markku Kulmala
    Abstract:

    We have performed a series of simulations with an Aerosol Dynamics box model to study the connection between new particle formation and sulphuric acid concentration. For nucleation either activation mechanism with a linear dependence on the sulphuric acid concentration, kinetic mechanism with a squared dependence on the sulphuric acid concentration or ternary H 2 O-H 2 SO 4 -NH 3 nucleation was assumed. The aim was to study the factors that affect the sulphuric acid dependence during the early stages of particle growth, and specifically to find conditions which would yield the linear dependence between the particle number concentration at 3–6 nm and sulphuric acid, as observed in field experiments. The simulations showed that the correlation with sulphuric acid may change during the growth from nucleation size to 3–6 nm size range, the main reason being the size dependent growth rate between 1 and 3 nm. In addition, the assumed size for the nucleated clusters had a crucial impact on the sulphuric acid dependence at 3 nm. A linear dependence between the particle number concentration at 3 nm and sulphuric acid was achieved, when activation nucleation mechanism was used with a low saturation vapour pressure for the condensable organic vapour, or with nucleation taking place at ~2 nm instead of ~1 nm. Simulations with activation, kinetic and ternary nucleation showed that ternary nucleation reproduces too steep dependence on sulphuric acid as compared to the linear or square dependence observed in field measurements.

Werner Hofmann – One of the best experts on this subject based on the ideXlab platform.

  • TEMPORARY REMOVAL: Aerosol Dynamics simulations of the anatomical variability of e-cigarette particle and vapor deposition in a stochastic lung
    Journal of Aerosol Science, 2020
    Co-Authors: Lukas Pichelstorfer, Michael Boy, Renate Winkler-heil, Werner Hofmann
    Abstract:

    Abstract Electronic cigarette (EC) Aerosols are typically composed of a mixture of nicotine, glycerine (VG), propylene glycol (PG), water, acidic stabilizers and a variety of flavors. Inhalation of e-cigarette Aerosols is characterized by a continuous modification of particle diameters, concentrations, composition and phase changes, and smoker-specific inhalation conditions, i.e. puffing, mouth-hold and bolus inhalation. The dynamic changes of inhaled e-cigarette droplets in the lungs due to coagulation, conductive heat and diffusive heat/convective vapor transport and particle phase chemistry are described by the Aerosol Dynamics in Containment (ADiC) model. For the simulation of the variability of inhaled particle and vapor deposition, the ADiC model is coupled with the IDEAL Monte Carlo code, which is based on a stochastic, asymmetric airway model of the human lung. We refer to the coupled model as “IDEAL/ADIC_v1.0”. In this study, two different e-cigarettes were compared, one without any acid (“no acid”) and the other one with an acidic regulator (benzoic acid) to establish an initial pH level of about 7 (“lower pH”). Corresponding deposition patterns among human airways comprise total and compound-specific number and mass deposition fractions, distinguishing between inhalation and exhalation phases and condensed and vapor phases. Note that the inhaled EC Aerosol is significantly modified in the oral cavity prior to inhalation into the lungs. Computed deposition fractions demonstrate that total particle mass is preferentially deposited in the alveolar region of the lung during inhalation. While nicotine deposits prevalently in the condensed phase for the “lower pH” case, vapor phase deposition is dominating the “no acid” case. The significant statistical fluctuations of the particle and vapor deposition patterns illustrate the inherent anatomical variability of the human lung structure.

  • Aerosol Dynamics model for the simulation of hygroscopic growth and deposition of inhaled NaCl particles in the human respiratory tract
    Journal of Aerosol Science, 2017
    Co-Authors: Renate Winkler-heil, Lukas Pichelstorfer, Werner Hofmann
    Abstract:

    Abstract The purpose of the present work is the implementation of the Aerosol Dynamics model ADiC, specifically its heat/vapor transport and phase transition components, into the stochastic lung deposition model IDEAL. The combined ADiC/IDEAL model allows the simultaneous calculation of relative humidity, hygroscopic growth and deposition of inhaled NaCl Aerosols in individual airways of the human lung along randomly selected particle paths and randomly selected times during the inhalation phase. Hygroscopic growth decreases deposition of submicron particles compared to hydrophobic particles with equivalent diameters due to a less efficient diffusion mechanism, while the more efficient impaction and sedimentation mechanisms increase total deposition for micrometer particles. Due to the variability and asymmetry of the human airway system, individual trajectories of inhaled particles are associated with individual growth factors. For a realistic breathing scenario, particles are inhaled at different times during the inspiratory phase and hence experience individual growth factors, thereby further enhancing the variability of individual growth factors and resulting deposition patterns. While nanometer particles adopt their equilibrium growth factor value already within the mouth and pharynx/larynx during the inspiratory phase, micrometer particles approach this value at the end of inspiration, thus further increasing in size during the exhalation phase. In summary, individual hygroscopic growth factors vary for different paths and different inhalation times. For model validation purposes, theoretical predictions were compared with human experimental deposition data and previous hygroscopic growth model simulations for total deposition of ultrafine and micrometer-sized NaCl particles.

  • Simulation of Aerosol Dynamics and deposition of combustible and electronic cigarette Aerosols in the human respiratory tract
    Journal of Aerosol Science, 2016
    Co-Authors: Lukas Pichelstorfer, Werner Hofmann, Renate Winkler-heil, Caner U. Yurteri, John Mcaughey
    Abstract:

    Abstract The Aerosol Dynamics in Containments (ADiC) model describes the dynamic changes of inhaled cigarette smoke droplets during puffing, mouth-hold, and inspiration and expiration, considering coagulation, phase transition, conductive heat and diffusive/convective vapor transport, and dilution/mixing. The ADiC model has been implemented into a single path representation of the stochastic lung dosimetry model IDEAL to compute particulate phase deposition as well as vapor phase deposition in the airway generations of the human lung. In the present study, the ADiC model has been applied to the inhalation of combustible and electronic cigarette Aerosols. Aerosol Dynamics processes significantly influence the physical properties of particle and vapor phase in the human respiratory tract: (i) number reduction of inhaled Aerosol particles is caused primarily by coagulation and less by deposition for both Aerosols; (ii) hygroscopic growth rates are higher for e-cigarettes than for combustible cigarettes; (iii) the effect of particle growth on deposition leads to a lower total deposition in the case of cigarette smoke particles and a higher total deposition in the case of e-cigarette droplets relative to their initial size distributions; and, (iv) most of the nicotine is deposited by the vapor phase for both Aerosols.

John H. Seinfeld – One of the best experts on this subject based on the ideXlab platform.

  • Inverse Modeling of Aerosol Dynamics Using Adjoints: Theoretical and Numerical Considerations
    Aerosol Science and Technology, 2005
    Co-Authors: Adrian Sandu, Wenyuan Liao, Greg Carmichael, Daven K. Henze, John H. Seinfeld
    Abstract:

    In this paper we develop the algorithmic tools needed for inverse modeling of Aerosol Dynamics. Continuous and discrete adjoints of the Aerosol dynamic equation are derived, as well as sensitivity coefficients with respect to the coagulation kernel, the growth rate, and the emission and deposition coefficients. Numerical tests performed in the twin experiment framework for a single compcomponent modemodel problem show that the initial distributions and the dynamic parameters can be recovered from time series of observations of particle size distributions.

  • development and application of the model of Aerosol Dynamics reaction ionization and dissolution madrid
    Journal of Geophysical Research, 2004
    Co-Authors: Yang Zhang, Spyros N. Pandis, Athanasios Nenes, Christian Seigneur, Mark Z. Jacobson, Betty K Pun, Krish Vijayaraghavan, John H. Seinfeld
    Abstract:

    [1] A new Aerosol model, the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (MADRID) has been developed to simulate atmospheric partparticulate matter (PM). MADRID and the Carnegie-Mellon University (CMU) bulk aqueous-phase chemistry have been incorporated into the three-dimensional Models-3/Community Multiscale Air Quality model (CMAQ). The resulting model, CMAQ-MADRID, is applied to simulate the August 1987 episode in the Los Angeles basin. Model performance for ozone and PM is consistent with current performance standards. However, organic Aerosol was underpredicted at most sites owing to underestimation of primary organic PM emissions and secondary organic Aerosol (SOA) formation. Nitrate concentrations were also sometimes underpredicted, mainly owing to overpredictions in vertical mixing, underpredictions in relative humidity, and uncertainties in the emissions of primary pollutants. Including heterogeneous reactions changed hourly O3 by up to 17% and 24-hour average PM2.5, sulfate2.5, and nitrate2.5 concentrations by up to 3, 7, and 19%, respectively. A SOA module with a mechanistic representation provides results that are more consistent with observations than that with an empirical representation. The moving-center scheme for particle growth predicts more accurate size distributions than a typical semi-Lagrangian scheme, which causes an upstream numerical diffusion. A hybrid approach that simulates dynamic mass transfer for coarse PM but assumes equilibrium for fine PM can predict a realistic particle size distribution under most conditions, and the same applies under conditions with insignificant concentrations of reactive coarse particles to a bulk equilibrium approach that allocates transferred mass to different size sections based on condensational growth law. In contrast, a simple bulk equilibrium approach that allocates transferred mass based on a given distribution tends to cause a downstream numerical diffusion in the predicted particle size distribution.

  • International Conference on Computational Science – Computational Aspects of Data Assimilation for Aerosol Dynamics
    Computational Science – ICCS 2004, 2004
    Co-Authors: Adrian Sandu, John H. Seinfeld, Wenyuan Liao, Daven K. Henze, Gregory R. Carmichael, Tianfeng Chai, Dacian N. Daescu
    Abstract:

    In this paper we discuss the algorithmic tools needed for data assimilation for Aerosol Dynamics. Continuous and discrete adjoints of the Aerosol dynamic equation are considered, as well as sensitivity coefficients with respect to the coagulation kernel, the growth rate, and emission and deposition coefficients. Numerical experiments performed in the twin experiment framework for a single compcomponent modemodel problem show that initial distributions and the dynamic parameters can be recovered from time series of observations of particle size distributions.