Synopsis Studying the internal mixtures of primary organic aerosol (POA) and secondary organic aerosol (SOA) materials, we show that most POA + SOA mixtures exhibit phase-separated particles and that this miscibility gap can be predicted using the difference in the average elemental oxygen-to-carbon ratio of the organic components. Introduction Atmospheric aerosol particles influence the climate (1,2) and contribute to air pollution and hence have an impact on human health.
