The Canadian

Centre for Environmental Modelling and Chemistry

EQC Model

Version 2.02 - May 2003


New in version 2.02!

Software Description

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 Model:
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:

  • 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:

  • chemical name
  • molecular mass
  • reaction half-lives in each of air, water, soil, and sediment
  • for Type 1 chemicals:

  • - data collection temperature
    - melting point
    - water solubility (g/m3)
    - vapour pressure
    - log Kow
  • for Type 2 and 3 chemicals:

  • - partition coefficients

    Emission Rates:

  • emissions to any or all of air, water, and soil
  • Model output for each Level as appropriate includes:

  • 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
  • summary plots


    This program is only available in compiled form. A "readme.txt" file with more detailed technical information is included in the zipped file.

    Minimum system requirements:
    Pentium-75MHz with 8 Mb of RAM running Windows 95. On some systems it may be necessary to adjust your screen resolution.

    The EQC Model Version 1.01, released May 1997 and updated Nov 1997, continues to be available.

    For non-Windows users the BASIC, evaluative, Level I, II and III fugacity models are available.

    Please read the EQC 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.

    Bug Report

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    Last updated June 10, 2013.