The Canadian

Centre for Environmental Modelling and Chemistry

BASL4 Model

Version 1.10 - April 2008


New in version 1.10

Software Description

The BASL4, Biosolids-Amended Soil: Level IV, model calculates the fate of chemicals introduced to soil in association with contaminated biosolids amendment. Processes of chemical degradation, volatilization, leaching, diffusion, sorbed phase transport due to bioturbation, and the degradation of the organic matter (OM) present in the soil and amendment are quantified. Chemical is introduced to the soil either directly or as a component of biosolid amendments. It can be applied to the surface of the soil, injected into a deeper layer of soil, or ploughed into surface and deeper layers. Applications of biosolids or neat chemical can occur at user-specified times during the simulation, as can ploughing events.

An evaluative calculations of concentrations in vegetation, invertebrates, and small soil-dwelling mammals are performed.

This model is useful for assessing the long-term, year-to-year fate and possible build-up of chemicals in sludge-amended soils as well as for estimating risk of biotic uptake and bioaccumulation in soil-dwelling organisms.

The results of changes in chemical and soil properties may be explored by modifying the input data. Biota properties are not modifiable. Incremental changes in input properties can be used to obtain a sensitivity analysis.

Features of the BASL4 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 soils and soil properties.
Permits temporary additions/changes of soils and their properties to a simulation.
Permits permanent additions, changes and deletions of soils and their properties to the database.
Provides context-sensitive Help.
Displays and prints the BASL4 model calculations, as performed by the program.
Printing of model results is not permitted, however, program results may be saved as a comma separated value (csv) file viewable by standard spreadsheet software.

This program was based on the following publications:

Hughes, L., Mackay, D., Webster, E., Armitage, J., Gobas, F. 2005. Development and Application of Models of Chemical Fate in Canada: Modelling the Fate of Substances in Sludge-Amended Soils. Report to Environment Canada. CEMN Report No. 200502. Trent University, Peterborough, Ontario.

Hughes, L., Webster, E., Mackay, D. A Model of the Fate of Chemicals in Sludge-Amended Soils. Journal of Soil and Sediment Contamination (In review.)

Hughes, L., Webster, E., Mackay, D. A Model of the Fate of Chemicals in Sludge-Amended Soils with Vegetation and Soil-dwelling Organisms. Journal of Soil and Sediment Contamination (In preparation.)

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

A Users' Manual is available for this model:

Webster, E., Mackay, D. 2007. Modelling the Fate of Contaminants Introduced into Agricultural Soils from Biosolids: BASL4 Model: Users' Manual Report to Environment Canada. CEMC Report No. 200702 Trent University, Peterborough, Ontario.

The required input data are:

Chemical Properties:

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

  • field area
  • density of organic matter and mineral matter
  • air boundary layer thickness
  • molecular diffusivity in pore air and pore water
  • leaching and bioturbation rates
  • bioavailability factor
  • layer depth, diffusion distance, volume fraction of air and water
  • mass fraction of organic carbon (OC) per unit mass of dry soil solids in each layer
  • mass fraction of fast- and slow-degrading OC per unit total OC in each layer
  • mass fraction of OC per unit mass of organic matter (OM)
  • OC degradation half-lives for the fast- and slow-degrading OC
  • Biota Properties:
    These properties can not be changed. The properties used depend on the model calculations selected.

  • Vegetation - EQP (equilibrium partitioning) Model

  • - mass fractions of water and lipid in the root and leaf of a leafy tuber, grass or sedge, and a conifer
  • Carrot Root - Dynamic

  • - root volume and water uptake rate
  • Invertebrate - Equilibrium
  • - volume, density, and volume fractions of lipid and water
  • Invertebrate - Non-Equilibrium

  • - volume, density, and volume fractions of lipid and water
    - efficiencies of uptake from air and diet, and of soil OM digestion
    - volumetric rates of air respiration, water turnover, and diet (soil solids)
    - elimination rate constants: metabolism, reproduction, and growth dilution
  • Mammal - Equilibrium

  • - volume, density, and volume fractions of lipid and water
  • Mammal - Non-Equilibrium

  • - volume, density, and volume fractions of lipid and water
    - efficiencies of uptake from air and diet, dietary absorption of water, and lipid, non-lipid organic matter (NLOM), and soil OM digestion
    - volumetric rates of air respiration, water turnover, and diet (soil solids and soil in worms)
    - elimination rate constants: metabolism, reproduction, and growth dilution

    Simulation Times:

  • time step
  • total simulation time
  • Chemcial Application Events:

  • initial concentrations in each soil layer
  • number of chemical or biosolids applications
  • For each application:
  • -time of addition
    -method of application (surface or injection)
    -type of addition (pure or biosolid)
    -biosolid composition (if applicable): fraction of fast- and slow-degrading OC, concentration of chemical in the biosolid

    Ploughing Events:

  • number of events
  • time of each event
  • Model output includes:

  • all input data for the chemical
  • all input data for the soil
  • - includes time-dependent physical properties such as OC and OM content
  • all input data for the biota
  • simulation time and event inputs
  • chemical fate in the soil
  • - Z and VZ values, fugacity
    - concentrations by phase and soil layer
    - amounts by phase and soil layer
    - chemical inventory for each layer
    - fluxes and D values
  • chemical fate in the biota
  • - Z values, fugacity
    - fugacity
    - concentrations
    - fluxes and D values (if non-equilibrium calculations are selected)
  • diagrams (schematic only, no values) and charts of selected results
  • Minimum system requirements are an IBM-compatible PC running Windows 98 or XP. This model will not run under Windows NT or 2000.

    The BASL4 Model Version 1.00, released April 2007, continues to be available.

    Please read the BASL4 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 10, 2013.