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9-months extension request for SNF Project No. 200020-125151: "Physical states of mixed organic-inorganic aerosols"

English title 9-months extension request for SNF Project No. 200020-125151: "Physical states of mixed organic-inorganic aerosols"
Applicant Peter Thomas
Number 143996
Funding scheme Project funding (Div. I-III)
Research institution Institut für Atmosphäre und Klima ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.10.2012 - 30.06.2013
Approved amount 85'343.00
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Keywords (6)

EFFLORESCENCE/DELIQUESCENCE; ORGANIC AEROSOLS; THERMODYNAMICS; MISCIBILITY GAPS; RADIATIVE FORCING; TROPOSPHERIC CHEMISTRY

Lay Summary (English)

Lead
Lay summary

The physical state of the tropospheric aerosol is still largely unknown despite its importance for cloud formation, multiphase and heterogeneous chemistry in and on aerosol particles, and for the aerosol’s radiative properties. Especially the high organic fraction (of largely unknown composition) of the atmospheric particulate matter makes it difficult to predict its physical state.

We have developed a thermodynamic activity coefficient model called AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) that is able to calculate vapor-liquid, solid-liquid, and liquid-liquid equilibria in atmospheric aerosols composed of a wide range of inorganic salts and organic compounds. In the present project, we will assess and generalize AIOMFAC. The main focus will be on aqueous organic systems at low temperatures containing the functionalities typically found in tropospheric aerosol particles, namely alkyl, hydroxyl, carboxyl, carbonyl, ether, aromatic, aldehyde, and vinyl groups. A second focus is the generalization of the model to low temperatures by the development of suitable parameterizations for electrolyte solutions containing the important inorganic constituents of aerosols such as ammonium sulfate and nitrate and sodium chloride.

In the experimental part of the project, we will study systems with liquid-liquid phase separations that are confined within the supersaturated region of the inorganic salt with a Raman microscope during humidity cycles. The investigation of micrometer sized droplets allows determining liquid-liquid phase boundaries and metastability phase diagrams that are not accessible by bulk methods. Moreover, we will investigate whether the crystallization of the salt is preceded or even triggered by a liquid-liquid phase separation and how gas/particle partitioning is influenced in the presence of a liquid-liquid phase separation.

With the further development of AIOMFAC it will be possible to model the phases of the systems that we investigate experimentally and to predict their phase states based on their chemical composition. Thus, the experimental investigations together with the AIOMFAC model allow to estimate the occurrence probability of liquid-liquid phase separations in tropospheric aerosols, and more generally their hygroscopicity, reactivity, and gas/particle partitioning of semi-volatile species.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures
Ganbavale Gouri, Zuend Andreas, Marcolli Claudia, Peter Thomas (2015), Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures, in Atmos. Chem. Phys, 15, 447-493.
Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions
Ganbavale Gouri, Marcolli Claudia, Krieger Ulrich K., Zuend Andreas, Stratmann Greta, Peter Thomas (2014), Experimental determination of the temperature dependence of water activities for a selection of aqueous organic solutions, in Atmos. Chem. Phys., 14, 9993-10012.
Morphologies of mixed organic/inorganic/aqueous aerosol droplets
Song Mijung, Marcolli Claudia, Krieger Ulrich K., Lienhard Daniel M., Peter Thomas (2013), Morphologies of mixed organic/inorganic/aqueous aerosol droplets, in Faraday Discussions, 165, 289-316.

Collaboration

Group / person Country
Types of collaboration
EMPA, Dr. Ch. Hüglin Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
PSI, Prof. U. Baltensperger Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
ETHZ, IAC, Prof. U. Lohmann Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Weizmann Institute, Prof. Y. Rudich Israel (Asia)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Goldschmidt Conference, 2013 Poster Temperature dependence of water activity in organic aerosols. 25.08.2013 Florence, Italy, Italy Ganbavale Gouri;
Faraday Discussion 165, Tropospheric Aerosol – Formation, Transformation, Fate and Impacts 2013 Talk given at a conference Morphologies of mixed organic/inorganic/aqueous aerosol droplets. 22.07.2013 Leeds, UK, Stateless Marcolli Claudia;
European Geosciences Union (EGU) General Assembly 2013 Poster Morphologies of aerosol particles consisting of two liquid phases. 07.04.2013 Vienna, Austria Song Mijung;
American Geosciences Union (AGU) Fall Meeting 2012 Poster Phase transitions and morphologies of aerosol particles. 03.12.2012 San Francisco, United States of America Song Mijung;


Associated projects

Number Title Start Funding scheme
103651 Physical states of mixed organic / inorganic aerosols 01.11.2004 Project funding (Div. I-III)
108032 The effects of organic compounds on the hygroscopic properties of inorganic aerosols 01.07.2005 Project funding (Div. I-III)
125151 Physical states of mixed organic-inorganic aerosols 01.10.2009 Project funding (Div. I-III)
146760 Physical states of mixed organic-inorganic aerosols 01.09.2013 Project funding (Div. I-III)
63328 Einfluss von Organika auf atmosphärische wässrige Aerosole 01.04.2002 Project funding (Div. I-III)
146760 Physical states of mixed organic-inorganic aerosols 01.09.2013 Project funding (Div. I-III)
125151 Physical states of mixed organic-inorganic aerosols 01.10.2009 Project funding (Div. I-III)

Abstract

The physical state of the tropospheric aerosol is still largely unknown despite its importance for the aerosol’s radiative properties, for cloud formation, and for multiphase and heterogeneous chemistry in and on aerosol particles. Especially the organic fraction (of mostly unresolved composition) of the particulate matter makes it difficult to predict its physical state. We have developed and corroborated the scientific hypothesis that due to the complexity of the organic fraction of the tropospheric aerosol, organics will mostly stay in the liquid state. This organic liquid takes up and releases water continuously when the relative humidity (RH) changes. In the atmosphere, the organic fraction is usually internally mixed with inorganic salts that are dissolved in aqueous solution particles at high RH and may form crystalline solids at low RH. While the dissolution of the salt (deliquescence) occurs at the relative humidity present above the saturated solution of the salt, high supersaturations of the salt are usually required before atmospheric particles crystallize (effloresce). Experiments and modeling studies have shown that deliquesced aerosols can be present as one-phase systems consisting of an aqueous solution of organics, inorganic salts and water or as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase.In the SNF Project 200020-103651 (Physical states of mixed organic / inorganic aerosols) that finished by the end of 2009 we investigated liquid-liquid and liquid-solid phase changes of mixed organic-inorganic droplets. We have developed a thermodynamic activity coefficient model called AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) that is able to calculate vapor-liquid, solid-liquid, and liquid-liquid equilibria of systems composed of a wide range of inorganic salts and organic compounds. Experimentally we investigated the phase changes of droplets consisting of a mixture of poly(ethylene glycol) 400 and ammonium sulfate with a Raman microscope during humidity cycles. This mixed organicinorganic model system exhibits liquid-liquid phase separation at relative humidities below 90 % in addition to deliquescence/efflorescence of the ammonium sulfate fraction. This combined modeling and experimental approach allows deepening the understanding of multiphase aerosols by investigating the same system experimentally and theoretically. For the continuation project 200020-125151 we obtained funding for two PhD theses that build upon the achievements of SNF Project 200020-103651. Hereby we ask for funding for an extension of 9 months.The objective of PhD student I is the assessment and generalization of AIOMFAC. The main focus is on aqueous organic systems at low temperatures containing the functionalities typically found in tropospheric aerosol particles, namely alkyl, hydroxyl, carboxyl, carbonyl, ether, aromatic, aldehyde, and vinyl groups. These systems are treated by AIOMFAC’s short-range part. This PhD work comprises the collection of activity data at low temperatures from literature, measurements of the temperature dependence of water activities for solutions that are of special interest to atmospheric aerosols, and to determine temperature dependent AIOMFAC interaction parameters by fitting the model to experimental data. This extension will enable us to finish the planned work, which was delayed because of difficult data availability.PhD student II studies systems with liquid-liquid phase separations to establish for which aerosol compositions liquid-liquid phase separation occurs. The investigation of micrometer sized droplets allows determining liquid-liquid phase boundaries and state diagrams that are not accessible by bulk methods. An additional focus that goes beyond the proposed work is an indepth analysis of the morphology of the aerosol particles for the model systems investigated so far. A 9-months extension will enable us to perform this work. With the further development of AIOMFAC we can predict the phase states of systems investigated in PhD II based on their chemical composition. Thus, the experimental investigations together with the AIOMFAC model allow to estimate the occurrence probability of liquid-liquid phase separations in tropospheric aerosols, and more generally their hygroscopicity, reactivity, and gas/particle partitioning of semi-volatile species.
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