Organic

Absorptive partitioning model for equilibrium gas–particle partitioning of semivolatile organic compounds. A compound distributes between the gas phase and an absorbing organic aerosol phase according to a mass-based partition coefficient K_om and the total absorbing organic aerosol mass C_oa. From Seinfeld and Pandis (2006), Chapter 9, Section 9.4, Equation 9.23.

BET (Brunauer-Emmett-Teller) adsorption isotherm for multilayer adsorption. Extends the Langmuir model to include formation of additional molecular layers, assuming each adsorbed molecule can serve as an adsorption site for the next layer. From Seinfeld and Pandis (2006), Chapter 14, Section 14.5.3, Equation 14.45.

Elemental carbon (EC) tracer method for estimating secondary organic carbon (OC) from measurements of total OC and EC. Primary OC is estimated as combustion-related OC (proportional to EC via the OC-to-EC ratio) plus noncombustion OC; secondary OC is the non-negative remainder. From Seinfeld and Pandis (2006), Chapter 14, Section 14.3.2, Equations 14.3–14.4.

FHH (Frenkel-Halsey-Hill) adsorption isotherm for multilayer adsorption on flat surfaces governed by van der Waals forces. Relates adsorbed volume to the gas-phase saturation ratio via two empirical parameters. From Seinfeld and Pandis (2006), Chapter 14, Section 14.5.3, Equation 14.46.

Langmuir adsorption isotherm for the formation of a monolayer of adsorbed molecules on particle surfaces. Assumes all adsorption sites are equivalent, no horizontal interactions, and uniform heat of adsorption. From Seinfeld and Pandis (2006), Chapter 14, Section 14.5.3, Equation 14.44.

Gas-particle partitioning model for a secondary organic aerosol (SOA) compound that does not interact with preexisting aerosol. The compound condenses as a pure substance once the reacted ROG exceeds a threshold set by the saturation concentration; below the threshold all product remains in the gas phase. From Seinfeld and Pandis (2006), Chapter 14, Section 14.5.2, Equations 14.6–14.18.

Two-product model for secondary organic aerosol (SOA) formation (Odum et al., 1996). Represents the complex mixture of oxidation products from a reactive organic gas (ROG) as two lumped surrogate products that partition between gas and aerosol phases according to an ideal-solution absorptive-partitioning equilibrium. Yields and saturation concentrations correspond to alpha-pinene oxidation from Seinfeld and Pandis (2006) Table 14.12.