EQSAM (EQuilibrium Simplified Aerosol Model) is a computationally efficient thermodynamic
aerosol composition model that allows to calculate the gas/aerosol equilibrium partitioning,
including aerosol water, sufficiently fast and accurate for global and regional modeling.
EQSAM is based on a number of parameterizations, including single solute molalities and activity
coefficients. The thermodynamic framework (domains and subdomains, internally mixed aerosols)
is the same as of more complex aerosol thermodynamic equilibrium models, e.g. of ISORROPIA
(Nenes et al., 1998). Details are given in the references below (and the references therein).

https://ui.adsabs.harvard.edu/abs/2000PhDT.......328M/abstract
https://dspace.library.uu.nl/bitstream/handle/1874/646/full.pdf
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2001JD001102
https://acp.copernicus.org/articles/6/2549/2006/
https://acp.copernicus.org/articles/12/5429/2012/
https://acp.copernicus.org/articles/16/7213/2016/
https://acp.copernicus.org/articles/18/16747/2018/