Das Projekt "Unifying aerosol composition measurements with predictions of volatility and hygroscopicity" wird vom Umweltbundesamt gefördert und von Ecole Polytechnique Federale de Lausanne (EPFL), Faculte de l'Evironnement Naturel, Architectural et Construit (ENAC), IIE - APRL, Laboratoire de recherche sur Laboratoire de recherche sur les particules atmospheriques durchgeführt. Atmospheric particles (also often referred as aerosols in an atmospheric science context) are composed of sulfate, ammonium, nitrate, elemental carbon, organic compounds, trace metals, crustal elements, and water. Mass concentrations of fine particles less than 2.5 micrometers in diameter have been associated with excess mortality, and are regulated in the United States for these health concerns. Atmospheric particles can also interact with solar radiation and either absorb or scatter radiation directly, or act as seeds for cloud-droplet formation, which also affects the energy balance of the planet. Aerosols also serve as vessels for chemicals and nutrients to be transported over long distances. To understand the natural and anthropogenic burdens of atmospheric particles on human and ecosystems health, we require continued characterization of their composition and properties. In particular, there are two properties of atmospheric particles which we wish to accurately model to estimate their atmospheric lifetimes and overall mass burdens. These two properties are hygroscopicity -- how much water they take up -- and volatility -- how species with moderate vapor pressures partition between the gas and particle phase. These properties are linked to the chemical composition (and morphology) of the aerosol. Heuristically explained, particles containing soluble or polar compounds are more hygroscopic, and particle mass depends on how its species partition among gas, solid, aqueous, and (non-aqueous) liquid phases, differently depending on the magnitude and nature of their condensed-phase interactions. The ultimate goal is to describe these relationship in computational models which link source emission, chemical transformation, and receptor impacts so that we can use these models as decision-support tools for mitigation (evaluate emission control strategies) and adaptation (predict future air quality and climate scenarios based on projected changes in emissions). An important component of these models is the accurate description of condensed-phase interactions that link composition to hygroscopicty and volatility. One challenge in forming this description is that the number of molecules in the organic fraction are numerous and explicit consideration for each compound is infeasible. A necessary and common strategy is to represent the large number of in the condensed-phase by their functional group (and ionic) interactions. This project aims to address the lack of measurements, and measurement techniques which can capture the complex aerosol composition to evaluate theoretical models based on ionic and functional group parameterizations of composition.(...)