The Canadian

Centre for Environmental Modelling and Chemistry

Soil Model

Version 3.00 - August 2005

New in version 3.00!

Software Description

The Soil model gives a very simple assessment of the relative potential for reaction, degradation and leaching of a pesticide applied to a surface soil. Chemical partitioning between the air, water, organic matter, and mineral matter phases in a single layer of soil is calculated as a function of physical chemical properties. Roots are included as a fraction of the soil volume and are assumed to be at equilibrium with the other phases of the soil. This model gives an estimate of the rates of volatilization, leaching, and degradation from the soil. These rates are then used to estimate half-times for losses by these processes, and the overall half-time. The model is not dynamic in nature, it presents the steady-state condition and fluxes and infers the likely times associated with these loss processes.

This model is useful for examining the relative importance of each loss and transport process and for screening and comparing chemicals. The results of changes in chemical and soil properties may be explored by modifying the input data. Incremental changes in input properties can be used to obtain a sensitivity analysis.

Features of the Soil 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 a database of environments and environmental properties.
Permits temporary additions/changes of environments and their properties to a simulation.
Permits permanent additions, changes and deletions of environments and their properties to the database.
Provides context-sensitive Help.
Displays and prints the Soil model calculations, as performed by the program.
Allows the printing of simulation tables and the summary diagram.
Allows the program results to be saved as a comma separated value (csv) file viewable by standard spreadsheet software.

This program was based on the following publications:

Mackay, D., Stiver, W. 1991. Predictability and Environmental Chemistry. Chapter 8: pages 281-297

Mackay, D. 2001. Multimedia Environmental Models: The Fugacity Approach, Second Edition, Lewis Publishers, Boca Raton, 194-199.

The required input data are:

Chemical Properties:

  • chemical name
  • molar mass
  • data temperature
  • water solubility and vapour pressure
  • organic carbon - water partition coefficient, Koc
  • log (octanol - water partition coefficient), log Kow
  • mineral matter - water partition coefficient, Kmw
  • degradation half-life in soil
  • Soil Properties:

  • soil area and depth
  • mean vertical diffusion distance from middle of soil layer to surface
  • volume fractions of air, water, and roots
  • leaching rate
  • air boundary layer thickness
  • molecular diffusivity in pore air and pore water
  • density of water, organic matter, mineral matter, and roots
  • mass fractions of organic carbon in dry soil and in organic matter
  • lipid fraction in roots


  • chemical application rate
  • Model output includes:

  • all input data
  • fugacity of the soil
  • Z values for all phases
  • amounts and concentrations for all phases
  • D values, and fluxes for all processes
  • a summary diagram
  • Minimum system requirements are an IBM-compatible PC running Windows 98 or XP. This model will not run under Windows NT or 2000.

    For non-Windows users the BASIC, Soil model Version 1 is available.
    Version 2.00 is also available from our archives.

    Please read the SOIL 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.


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    Last updated June 12, 2013.