Research

Motivation & Research Directions

Current research activities of our group are focused on the development of numerical models and system analysis tools to enable better predictions of the partitioning of water and semivolatile organic species between particles and the surrounding air. Aspects of such models include the prediction of the types and amounts of condensable products that form due to chemical reactions in the gas-phase (atmospheric chemistry), as well as mixing effects in (and on) liquid, semi-solid and solid particle phases (applications of thermodynamic equilibrium computations and kinetic models).

Aside from our interest in the fundamental physical and chemical aerosol processes and their prediction with box models, a key motivation is to translate process-level knowledge of gas-aerosol chemistry and thermodynamics into information and constraints useful for the design of computationally efficient descriptions of physicochemical processes in atmospheric large-scale (3-D) models. Atmospheric 3-D models are essential tools for the forecasting of air quality and evaluation of climate change scenarios, important for long-term political decision-making and regulations concerning environmental protection. Improvements of aerosol modules used in large-scale atmospheric models are also necessary to close the gap between observations of particulate matter mass, composition and size distribution in the ambient air and corresponding predictions from 3-D chemical-transport simulations.

The development of detailed physicochemical models, as well as their validation, crucially depends on the availability of well-characterized measurements from laboratory experiments. We work together with international research partners to better understand measurement results, experimental techniques, needs for model improvements, and data requirements. These interactions with other scientists help to both develop and improve our models and to analyze and design new experiments of interest.

Current Topics & Research Interests

• Understanding the interplay of chemical composition, mixing thermodynamics, viscosity, mass transfer kinetics, and morphology of atmospheric and laboratory aerosol (e.g. Altaf et al., 2016).
• Formation, chemical, and physical processing of atmospheric aerosols and their role in the atmospheric life cycle of volatile organic and inorganic compounds (e.g. Pye et al., 2018).
• Secondary organic aerosol (SOA): sources, chemical properties and effects on regional air quality and the global climate system.
• Development of detailed physicochemical process models. These aid at least two purposes: (1) providing tools to study complex multiphase processes, such as the water uptake and activation of phase-separated or single-phase aerosol particles into cloud droplets (e.g. Ovadnevaite et al., 2017) and (2) establishing a benchmark for the improvement of reduced-complexity models and simple parametrizations, which have useful applications in describing aerosol processes in atmospheric large-scale models.
• Gas–particle partitioning and equilibrium thermodynamics of non-ideal mixtures characterizing aerosol particles.
• Physical Chemistry of phase transitions, phase separation, and physical states of complex organic–inorganic mixtures (e.g. Hodas et al., 2016, Lei et al., 2017).
• Liquid–liquid phase separation in aerosol particles containing water, organic compounds and dissolved inorganic electrolytes.
• Further development and applications of thermodynamic group-contribution models to compute the physicochemical properties of complex liquid and semi-solid aerosols. See also the AIOMFAC website to learn more about the AIOMFAC model (and to run it online).
• Development of efficient and reliable algorithms for the calculation of gas–particle partitioning, liquid–liquid phase separation, and phase stabilities in organic–inorganic systems.
• Gaining a quantitative understanding of aerosol acidity as a key particle property via modelling, experiments and field observations. Of particular interest to us are the effects of limited organic–inorganic mixing, equilibrium water content, and inorganic buffers on acidity. With feedbacks via acidity effects on multiphase chemistry. An other interest concerns the use of process models in assessing possible (measurable) proxies for aerosol acidity.

Open research positions in our group

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