The Canadian

Centre for Environmental Modelling and Chemistry

TAO Model

Version 1.01 - October 2009


New in version 1.01

Software Description

The TAOBAC model is a single organism bioaccumulation model treats the steady-state uptake and loss of an organic contaminant by a terrestrial or aquatic organism. The bioconcentration factor (BCF), and concentration and fugacity ratios such as the bioaccumulation factor (BAF), and biomagnification factor (BMF) are calculated. The uptake processes include respiration and food consumption. The contaminant losses occur by transfer through respiration, egestion in feces, metabolic conversion, and growth dilution.

This model is useful for estimating the likely extent of bioaccumulation in a terrestrial or aquatic organism and biomagnification from the food to the organism, and the relative importance of each uptake and loss process. The chemical residence time provides information on the likely uptake and depuration times. The model quantifies the various input and output processes in three formats: the conventional concentration - rate constant approach, the fugacity - Z and D value approach, and a novel characteristic time approach. It is believed that each approach has its advantages and insights. The three approaches yeild identical results. The results of changes in chemical, organism, and environmental properties may be explored by modifying the input data. Incremental changes in input properties can be used to obtain a sensitivity analysis. The novel component of this model is the calculation of characteristic times. These provide valuable additional insights regarding the relative importance of the various uptake and loss processes and can facilitate an evaluation of the bioenergetic consistency of organism properties.

Features of the TAOBAC 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 organisms and environments and their properties.
Permits temporary additions/changes of organisms and environments and their properties to a simulation.
Permits permanent additions, changes and deletions of organisms and environments and their properties to the database.
Provides context-sensitive Help.
Displays and prints the TAOBAC 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 text file viewable by standard spreadsheet software.

This program was based on the following publication:

Powell, A., Mackay, D., Webster, E., Arnot, J.A. 2009. Modeling bioaccumulation using characteristic times. Environ. Toxicol. Chem. 28 (2):272-278.

Required Input Data:

Chemical Properties:

  • chemical name
  • molar mass
  • metabolic half-life in the organism
  • Henry's Law constant or water solubility and vapour pressure
  • log Kow
  • Environmental and Organism Properties:

  • organism volume
  • lipid volume fraction in organism, food, and feces
  • feeding rate as percent of body volume per day
  • growth rate as fraction of volume per day
  • digestion factor
  • gut absorption efficiency in water and organic phases
  • gill uptake resistence time in water and organic phases (water respiring organisms only)
  • air intake rate and efficiency (airr respiring organisms only)
  • water imbibition and urination rates and efficiencies (air respiring organisms only)
  • suspended particles in water: concentration, density, and organic carbon content
  • Concentrations:

  • chemical concentration in water
  • chemical concentration in air (air respiring organisms only)
  • chemical concentration in food
  • Model Output:

  • all input data
  • BCF and concentration and fugacity ratios such as BAF and BMF
  • chemical residence times
  • concentrations, body burdens, fugacities, and Z values for all phases
  • uptake and loss rate constants, D values, characteristic times and fluxes for all processes
  • oragnism-specific characteristic times
  • 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.

    This model is an adaptation of the fugacity-based Fish model.

    The TAOBAC Model Version 1.00, released March 2009, continues to be available.

    Please read the TAOBAC 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.