naa a22 4500 528787306 20180924065503.0 cr unu---uuuuu 180924s2010 xx s 000 0 eng 10.3929/ethz-b-000022283 doi 10.5194/acp-10-7795-2010 doi (ETHRESEARCH)oai:www.research-collection.ethz.ch:20.500.11850/22283 Computation of liquid-liquid equilibria and phase stabilities: Implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols [Elektronische Daten] [Andreas Zuend, Claudia Marcolli, Thomas Peter, John H. Seinfeld] Atmos. chem. phys. Open access ethresearch Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of multicomponent systems. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system simulation. For simplified partitioning parametrizations, we suggest a modified definition of the effective saturation concentration, Cj*, by including water and other inorganics in the absorbing phase. Such a Cj* definition reduces the RH-dependency of the gas/particle partitioning of semivolatile organics in organic-inorganic aerosols by an order of magnitude as compared to the currently accepted definition, which considers the organic species only. Creative Commons Attribution 3.0 Unported http://creativecommons.org/licenses/by/3.0 ethresearch Zuend Andreas joint author Marcolli Claudia joint author Peter Thomas joint author Seinfeld John H. joint author Atmospheric Chemistry and Physics Munich : European Geophysical Society 10 (16), pp. 7795-7820 1680-7375 http://hdl.handle.net/20.500.11850/22283 text/html WWW-Backlink auf das Repository (Open access) 1 Journal Article ethresearch ETHRESEARCH 856 40 http://hdl.handle.net/20.500.11850/22283 text/html WWW-Backlink auf das Repository (Open access) ETHRESEARCH 700 1- Zuend Andreas joint author ETHRESEARCH 700 1- Marcolli Claudia joint author ETHRESEARCH 700 1- Peter Thomas joint author ETHRESEARCH 700 1- Seinfeld John H. joint author ETHRESEARCH 773 0- Atmospheric Chemistry and Physics Munich : European Geophysical Society 10 (16), pp. 7795-7820 1680-7375 BK010053 XK010053 XK010000 ETHRESEARCH ETHRESEARCH ETHRESEARCH Journal Article Open access