The Canadian

Centre for Environmental Modelling and Chemistry

AirWater Fugacity Model

This is a BASIC program which calculates the air-water exchange characteristics of a chemical based on its physical chemical properties and total air and water concentrations. This is useful when estimating rates of chemical loss from treatment lagoons, ponds, and lakes, for estimating deposition rates of atmospheric contaminants, and for interpreting observed air and water concentrations to establish the direction and rate of transfer. This simple model provides a rational method of estimating exchange characteristics and allows exploration of the sensitivity of the results to the various input parameters.

This model is described in detail in "Multimedia Environmental Models; The Fugacity Approach" by D. Mackay, Lewis Publishers, CRC Press. 1991 on pages 186-193.

The required input data are:

Chemical Properties:

  • chemical name
  • molecular mass
  • data collection temperature
  • melting point
  • water solubility
  • vapour pressure
  • log Kow

    • Chemical Concentrations:

  • in water column
  • in air

    • Environmental Properties:

  • area
  • water depth
  • atmosphere height
  • concentration of suspended particulate matter in water
  • fraction of organic carbon content in the suspended particulate in the water
  • aerosol or TSP concentration
  • water side mass transfer coefficient
  • air side mass transfer coefficient
  • dry deposition velocity
  • rain rate
  • scavenging coefficient


    • Model output includes:

  • Z values for all phases
  • overall water and air phase mass transfer coefficients
  • percent resistence in air and water
  • D, and G values for all processes
  • fluxes for all processes
  • fugacities and concentrations for all phases
  • amount of chemical in air and water
  • rates of transfer for air and water
  • residence time in air and water

    • System requirements to run the compiled program are minimal.

    Please read the AIRWATER 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 August 12, 2011.