Fugacity model

The fugacity modelling approach was introduced by Mackay et al., and can be considered

to be a distribution-modelling tool based on the concept of fugacity

(Mackay, 1991 and 2001). The fugacity, f [Pa], is a normalised measure of the concentration

of a substance within a phase (solid, liquid or gaseous).

f=Zi+Ci

Zi is defined as the fugacity capacity [mol m-3 Pa-1], the escaping tendency of a substance from the phase i.

Each phase has a set of defined transport velocity parameters, their D values [mol Pa-1 h-1].

When combined with mass flow equations, degradation kinetics (e.g., the half-lives of the substance in the included phases)

and the spatial parameterisation of a certain area, the fugacity modelling approach can give valuable information

on the distribution of the substance between different phases (‘compartments’) in the environment.

The models also provide information on residence time, accumulation and concentrations.

In order to include the unsteady-state dynamics of the substances being emitted to the

Compartments of the model, the calculating algorithm needs to handle and solve the

Differential equation;

Vi being the volume of the compartment i,

Zi its bulk fugacity capacity, Ii is the input rate,

each term Djifj represents intermediary input transfers and

DTifi is the total output.

Link to level III fugacity model EQC (Mackay et al, downloadable freeware)

http://www.trentu.ca/academic/aminss/envmodel/models/VBL3.html