Overview

In this tutorial we will explore the use of index lists in modelling. It is recommended that you first read Tutorial 2-Creating a compartment model, where a basic description of the concept of Materials and Index lists is given.

The conceptual model

Consider a model that describes the turnover of a group of contaminants in a simple environmental system with two compartments: Upper_Soil and Lower_Soil. The contaminants enter the system from an atmospheric source via deposition on upper soil. This is represented in the model using a parameter called “input”, which has different values for different contaminants.

The transfer rate from the Upper_Soil to Lower_Soil is represented in the model with the help of a parameter “TC”. The same parameter is used to determine the transfer rate out from the system.

The mathematical model

The following ordinary differential equations describes the mass balance of the contaminants in the upper soil layer:

dA_{Upper Soil}/dt = Input - TC_{Upper to Lower} * A_{Upper Soil}
dA_{Lower Soil}/dt = TC_{Upper to Lower} * A_{Upper Soil} - TC_{Lower to Sink} * A_{Lower Soil}

where:
A_{Upper Soil} is the contaminant inventory in the upper soil layer.

A_{Lower Soil} is the contaminant inventory in the lower soil layer.

Input is the contaminant deposition rate.

TC_{Upper to Lower} is the transfer rate from the upper to the lower soil layer.

TC_{Lower to Sink} is the transfer rate of contaminants leaving the system from the lower soil layer.

Next

• Creating the model objects (2/4)

References

• Back to Tutorials
• Home