Results of the equilibration, which have been tested for thermodynamic consistency, are output to the screen in normal, verbose, form. The various types of information presented are summarised below.
A relative humidity based on the amount of liquid water present and calculated using the Zdanovskii-Stokes-Robinson relationship may also be given. This is explained further in section 4 of the model description page.
If the system contains one or more hydrophobic organic compounds, a non-aqueous (hydrophobic) liquid phase may exist in addition to an aqueous phase. As noted on the model description page, water is excluded from the hydrophobic phase. The very small quantity that would exist there at equilibrium has little effect on the distribution of the different components between the phases.
The column "Act. Eqn." lists the activity coefficient equation used for each solute. "PSC" stands for the Pitzer-Simonson-Clegg equations which are used for inorganic and organic ions, and "R-K" stands for the Redlich-Kister expansion. Other possible entries are "UNIFAC" and "Raoult's law".
Entries in the "Model" column indicate whether the organic components in the system were treated as individual components when their activity coefficients and contribution to the water activity were calculated, or whether they were grouped together. This is explained in section 4 of the E-AIM model description. The possible values in the "Model" column for uncharged organic solutes are: "Single comp.", "UNIFAC", or "ZSR". An entry of "CSB" for water means that the water activity of a mixture containing both ions and organic solutes has been estimated using the approach of Clegg, Seinfeld, and Brimblecombe. See the model description for details.
The density and volume of the liquid phase are listed beneath the table. The calculation of these properties requires that a molar volume has been specified for each organic compound that is present in the phase.
For the surface tension, which follows, a value is displayed for the aqueous phase of inorganic systems and for those containing organic compounds (including organic ions) even if no surface tension model parameters have been entered for them. In such cases the organic species are assumed to have no influence on the surface tension. This assumption is only likely to be reasonable if their concentrations are low relative to those of other solutes (inorganic ions, and organic compounds for which parameters have been entered). Surface tensions are only calculated for the other (hydrophobic) liquid phase, if it exists, if model parameters are available for all components.
Kappa (κ), the last item in this section of the output, is a parameter that approximately describes the water uptake of soluble material and its dependence upon ambient relative humidity. It is defined by eq (3), and associated equations, in Petters and Kreidenweis (Atmos. Phys. Chem. 7, 1961-1971, 2007), so that κ = Vw / Vs × (1 − RH) / RH. In this equation Vs is the dry particle volume and Vw the effective volume of water. The value of Vw is equal to the volume of the aqueous phase (which is determined using the methods described on the E-AIM density page), minus the dry solids volume. Note this this value of κ will differ slightly from that obtained on the "Köhler curve" pages of the website, because in the standard κ − Köhler theory the volumes of liquid aerosol particles are assumed to be equal to the sums of the volumes of pure water and the dry solutes. This useful simplifying approximation is not necessary in cases where the densities of the aqueous aerosol particles can be estimated more accurately, as is the case here.
Because the actual variation of aerosol water uptake is a complex function of RH, temperature, and chemical composition, the value of κ determined from the results of the E-AIM calculations (using the expression above) will vary with RH and temperature even though the chemical composition of the system remains the same. This is a reminder of the fact that, strictly, any individual value of κ is likely to be accurate only over a limited range of RH.
There are a number of circumstances in which κ is not determined, chiefly related to the need to be able to estimate the dry volume (Vs) of the solutes present: for example, molar volumes must be available for all organic components present, and inorganic "all acid" systems will be ignored. Also, there must be no solids or equilibrated gases (e.g., HNO3, NH3) in the result, so that the solutes in the aqueous phase at equilibrium are present in exactly the same amounts as have been input. See section 6 of the model description page for further details.