A new atmospheric aerosol phase equilibrium model (UHAERO): organic systems

Amundson, Neal R.; Caboussat, Alexandre; He, Jiwen; Martynenko, A. V.; Landry, Chantal; Tong, Chinghang; Seinfeld, John H.

doi:10.5194/acp-7-4675-2007

Cited by 18 publications

(16 citation statements)

References 34 publications

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“…Our observed water uptake is similar to that of binary aqueous solutions of molecules known to be present in SOA (Amundson et al, 2007). The strong repulsive forces that CH 2 groups exert on the solvating water are known as hydrophobic hydration and are expressed in the large positive g excess .…”

Section: Discussionsupporting

confidence: 72%

“…The non-ideality, expressed by the positive g excess , is skewed towards dilute solutions for all types, leading to an asymmetric shape of the g mix . Interestingly, the values and shape of the g mix versus composition relationship are similar to those predicted by the UHAERO model (Amundson et al, 2007) for the major α-pinene oxidation products adipic acid, pinic acid, and pinonic acid (c.f. their Fig.…”

Section: Non-ideal Modelsupporting

confidence: 72%

“…By tracing the changes in Gibbs free energy with overall component mole fraction, information about the number of phases may also be ascertained (e.g., Amundson et al, 2007). Normalized Gibbs free energy (g) is unitless and is the actual Gibbs free energy divided by the thermal energy, RT.…”

Section: Non-ideal Modelmentioning

confidence: 99%

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Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches

et al. 2009

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Abstract. We examine the hygroscopic properties of secondary organic aerosol particles generated through the reaction of α-pinene and ozone using a continuous flow reaction chamber. The water activity versus composition relationship is calculated from measurements of growth factors at relative humidities up to 99.6% and from measurements of cloud condensation nuclei activity. The observed relationships are complex, suggesting highly non-ideal behavior for aerosol water contents at relative humidities less than 98%. We present two models that may explain the observed water activity-composition relationship equally well. The first model assumes that the aerosol is a pseudo binary mixture of infinitely water soluble compounds and sparingly soluble compounds that gradually enter the solution as dilution increases. The second model is used to compute the Gibbs free energy of the aerosol-water mixture and shows that the aerosol behaves similarly to what can be expected for single compounds that contain a certain fraction of oxygenated and non-polar functional groups.

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Section: Discussionsupporting

confidence: 72%

Section: Non-ideal Modelsupporting

confidence: 72%

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Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches

et al. 2009

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“…Activity coefficients cannot be obtained by modeling alone because nonideal interactions between compounds remain largely unexplained on the molecular level. One of the main difficulties is the lack of experimental data to constrain activity coefficient models (Topping et al 2005;Amundson et al 2007) for likely constituents of atmospheric aerosols (Raatikainen and Laaksonen 2005). Of particular interest are activity coefficients for compounds frequently identified in organic aerosols at RH approaching 100%.…”

Section: Introductionmentioning

confidence: 99%

Accurate Determination of Aerosol Activity Coefficients at Relative Humidities up to 99% Using the Hygroscopicity Tandem Differential Mobility Analyzer Technique

Petters

2013

Aerosol Science and Technology

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Aerosol water content plays an important role in aqueous phase reactions, in controlling visibility, and in cloud formation processes. One way to quantify aerosol water content is to measure hygroscopic growth using the hygroscopicity tandem differential mobility analyzer (HTDMA) technique. However, the HTDMA technique becomes less reliable at relative humidity (RH) >90% due to the difficulty of controlling temperature and RH inside the second DMA. For this study, we have designed and implemented a new HTDMA system with improved temperature and RH control. Temperature stability in the second DMA was achieved to ±0.02• C tolerance by implementing active control using thermoelectric heat exchangers and PID control loops. The DMA size resolution was increased by operating high-flow DMA columns at a sheath:sample flow ratio of 15:0.5. This improved size resolution allowed for improving the accuracy of the RH sensors by interspersing ammonium sulfate reference scans at high frequency. We present growth factor data for pure compounds at RH up to 99% and compare the data to theoretical values and to available bulk water activity data. With this HTDMA instrument and method, the osmotic coefficients of spherical, nonvolatile aerosols of known composition between 30 and 200 nm in diameter can be determined within ±20%. We expect that data from this instrument will lead to an improvement of aerosol water content models by contributing to the understanding of aerosol water uptake at high RH.

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“…The equilibrium state is predicted through the solution of the nonlinear equations system. In the Gibbs free energy minimization approach (e.g., AIM, Clegg et al, 1998b, a;GFEMIN, Ansari and Pandis, 1999a;ADDEM, Topping et al, 2005a Amundson et al, 2006Amundson et al, , 2007, the equilibrium state of the aerosol system is predicted through the solution of minimization of the Gibbs free energy of the system. Some of the thermodynamic models mentioned above have been compared and evaluated in several studies (Ansari and Pandis, 1999b;Zhang et al, 2000;Yu et al, 2005;Metzger et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Treatment of non-ideality in the SPACCIM multiphase model – Part 1: Model development

et al. 2016

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Abstract. Ambient tropospheric deliquesced particles generally comprise a complex mixture of electrolytes, organic compounds, and water. Dynamic modeling of physical and chemical processes in this complex matrix is challenging. Thus, up-to-date multiphase chemistry models generally do not consider non-ideal solution effects. Therefore, the present study was aimed at presenting further development of the SPACCIM (Spectral Aerosol Cloud Chemistry Interaction Model) through treatment of solution non-ideality, which has not been considered before. The present paper firstly describes the model developments including (i) the implementation of solution non-ideality in aqueous-phase reaction kinetics in the SPACCIM framework, (ii) the advancements in the coupling scheme of microphysics and multiphase chemistry and (iii) the required adjustments of the numerical schemes, especially in the sparse linear solver and the calculation of the Jacobian. Secondly, results of sensitivity investigations are outlined, aiming at the evaluation of different activity coefficient modules and the examination of the contributions of different intermolecular forces to the overall activity coefficients. Finally, first results obtained with the new model framework are presented.The SPACCIM parcel model was developed and, so far, applied for the description of aerosol-cloud interactions. To advance SPACCIM also for modeling physical and chemical processes in deliquesced particles, the solution non-ideality has to be taken into account by utilizing activities in reaction terms instead of aqueous concentrations. The main goal of the extended approach was to provide appropriate activity coefficients for solved species. Therefore, an activity coefficient module was incorporated into the kinetic model framework of SPACCIM. Based on an intercomparison of different activity coefficient models and the comparison with experimental data, the AIOMFAC approach was implemented and extended by additional interaction parameters from the literature for mixed organic-inorganic systems. Moreover, the performance and the capability of the applied activity coefficient module were evaluated by means of water activity measurements, literature data and results of other activity coefficient models. Comprehensive comparison studies showed that the SpactMod (SPACCIM activity coefficient module) is valuable for predicting the thermodynamic behavior of complex mixtures of multicomponent atmospheric aerosol particles. First simulations with a detailed chemical mechanism have demonstrated the applicability of SPACCIM-SpactMod. The simulations indicate that the treatment of solution non-ideality might be needed for modeling multiphase chemistry processes in deliquesced particles. The modeled activity coefficients imply that chemical reaction fluxes of chemical processes in deliquesced particles can be both decreased and increased depending on the particular species involved in the reactions. For key ions, activity coefficients on the order of 0.1-0.8 and a strong dependenc...

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A new atmospheric aerosol phase equilibrium model (UHAERO): organic systems

Cited by 18 publications

References 34 publications

Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches

Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches

Accurate Determination of Aerosol Activity Coefficients at Relative Humidities up to 99% Using the Hygroscopicity Tandem Differential Mobility Analyzer Technique

Treatment of non-ideality in the SPACCIM multiphase model – Part 1: Model development

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