EQC (EQuilibrium Criterion) Model
The EQC, or EQuilibrium Criterion, model uses chemical-physical properties to quantify a chemical's behaviour in an evaluative environment. The environment is fixed to facilitate chemical-to-chemical comparison.
Three degrees of complexity are treated in the EQC, or EQuilibrium Criterion, Model. Levels I and II assume thermodynamic equilibrium is achieved; Level II includes advective and reaction processes. Level III is a non-equilibrium, steady-state assessment of chemical fate in the environment.
Three types of chemicals are treated: chemicals that partition into all media (Type 1), involatile chemicals (Type 2), and chemicals with zero or near-zero solubility (Type 3).
This model is useful for establishing the general features of a new or existing chemical's behaviour, ie. the media into which the chemical will tend to partition, the primary loss mechanisms, and its tendency for intermedia transport. The result of various emission scenarios can be explored.
Features of the EQC Program:
- Provides a database of chemicals and chemical properties.
- Permits temporary additions/changes of chemicals and their properties to a simulation.
- Permits permanent additions, changes and deletions of chemicals and their properties to the database.
- Provides standard environment for chemical comparison.
- Does NOT permit changes to the standard environment.
- Provides context-sensitive Help.
- Displays and prints the model calculations, as performed by the program.
- Allows the printing of simulation tables, the summary diagrams, and a small selection of charts.
- Allows the program results to be saved as a comma separated value file, readable by many spreadsheet programs such as Excel.
A more detailed description of the model is given in the three paper set:
- Summary plots
- Chemical name
- Molecular mass
- Reaction half-lives in each of air, water, soil, and sediment
- For Type 1 chemicals:
- For Type 2 and 3 chemicals:
- Emissions to any or all of air, water, and soil
- All input data
- Environmental parameters
- Z and D values
- Fugacity of the system or of each compartment
- Concentrations and amounts in each compartment
- Chemical residence times
- Summary diagrams
This program was based on the following publication:
Mackay D, Paterson, S., Kicsi, G., Di Guardo, A., Cowan, C.E. "Assessing the Fate of New and Existing Chemicals: A Five Stage Process". Environ. Toxicol. Chem. 15 No.9 , 1618-1626, 1996.
Mackay D, Paterson, S., Di Guardo, A., Cowan, C.E. "Evaluating the Environmental Fate of a Variety of Types of Chemicals Using the EQC Model", Environ. Toxicol. Chem. 15 No.9, 1627- 1637, 1996.
Mackay D, Paterson, S., Kicsi, G., Cowan, C.E., Di Guardo, A., Kane, D.M. "Assessment of Chemical Fate in the Environment Using Evaluative, Regional and Local-Scale Models: Illustrative Application to Chlorobenzene and Linear Alkylbenzene Sulfonates" Environ. Toxicol. Chem. 15 No.9, 1638-1648, 1996.
The required input data are:
Chemical Properties
- Data collection temperature
- Melting point
- Water solubility (g/m3)
- Vapour pressure
- Log Kow
- Partition ratios
Environmental Properties
-
Emission rate in kg/h
Model output includes
- Z and D values
- Fugacity of the system or of each compartment
- Concentrations and amounts in each compartment
- Chemical residence times
The program is available as a colour Excel spreadsheet, and a more recently implemented greyscale spreadsheet version. Both are equivalent, though the latter is still in the "beta" test phase. Also available is the older VisualBasic version. Please report any problems to Prof. Mark Parnis.
Please read the software license before downloading the software. Use of the software constitutes your agreement to abide by the terms and conditions set out in the license agreement.