The Canadian

Centre for Environmental Modelling and Chemistry

Sediment Model

Version 2.00 - November 2000

Software Description

The Sediment model calculates the water-sediment exchange characteristics of a chemical based on its physical chemical properties and total water and sediment concentrations. The distribution of the chemical at defined, probably unsteady-state conditions, is described. The concentrations of the chemical in organisms in the water column and in the sediment are estimated. All transport fluxes are quantized. The fugacity in the water and in the sediment are calculated from the user-input concentration in each medium. Since the system may not have acheived steady-state at the time of concentration data collection, for comparison, the fugacity in each medium is calculated for the other medium assuming steady-state conditions.

This models is useful for determining the likely fate of a chemical subject to transfer between a water column and a sediment compartment. By quantifying the transport fluxes, the relative importance of each process can be assessed. The direction of net flux can be determined by comparing the fugacities calculated assuming steady-state conditions. The clearance time for the water, sediment, or whole system can be estimated from the calculated response times. The results of changes in chemical and environmental 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 Sediment 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 Sediment 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 publications:

Rueber, B., Mackay, D., Paterson, S. and Stokes, P. 1987. A discussion of chemical equilibria and transport at the sediment-water interface. Environ. Toxicol. Chem. 6: 731-739.

Mackay, D. 2001. Multimedia Environmental Models: The Fugacity Approach, Second Edition, Lewis Publishers, Boca Raton, 199-201.

The required input data are:

Chemical Properties:

chemical name

molar mass

data temperature

water solubility and vapour pressure

log octanol - water partition coefficient, Kow

mineral matter - water partition coefficient

degradation half-life in sediment

Environment Properties:

surface area

water column and sediment depth

volume fraction of pore water in sediment

concentration of suspended particles in water

densities of water, organic matter, mineral matter

mass fraction of organic carbon in suspended particles, sediment solids, and organic matter

lipid mass fraction a generic water organism and bentic organism

diffusion path length in the sediment

molecular diffusivity of chemical in water

rate of sediment deposition, resuspension, and net burial

Chemical Concentrations:

total chemical concentration in water

chemical concentration in sediment solids

Model output includes:

all input data

fugacity of water and sediment

fugacities assuming steady-state is achieved

bioconcentration factor

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.

Please read the Sediment 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.

Last updated August 12, 2011.