COLUMN STUDY User's Manual

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1. Table of Contents

2. Introduction

COLUMN STUDY is a numerical model that simulates one-dimensional advection and dispersion of a reactive solute originating from a contaminant spill. It models the processes of transport, sorption and reaction in the aqueous and sorbed phases of a solute. Input parameters include the infiltration rate, amount and location of contaminant, soil bulk density, moisture content, longitudinal dispersivity and partition and reaction coefficients. It solves the resulting system of equations by using a forward finite difference advection/dispersion code coupled to a linearized reaction model by the operator splitting method; much like the implementation of BUGS SCRATCHPAD.

3. Problem Characterization

COLUMN STUDY divides the characterization of the into three major categories: site properties, soil properties, and contaminant properties.

Site properties include the water infiltration rate (m/d); the depth of the soil column being modeled (m); the depth or extent of initial contaminant penetration into the soil column (m); and the total mass of contaminant spilled into the column (kg/m³).

Soil properties include the bulk density of the soil media (g/cm³); the moisture content (the air phase is ignored in this model) as a uniform property throughout the column; and finally the dispersivity coefficient (m).

The contaminant is characterized with a linear partitioning coefficient (cm³/g) as either an equilibrium or kinetic sorption/desorption process.. If a kinetic reaction is desired, the sorption/desorption rate is required (d^-1). First order decay rates for both the aqueous and sorbed phases can be stipulated as well.

4. Boundary Conditions

COLUMN STUDY calculates the one-dimensional pore water velocity from the infiltration rate and moisture content. It assumes a free flow outlet at the bottom of the column. Infiltration from the top is clean and does not add contaminant mass to the system. Contaminant mass is lost solely through decay and flow out of the bottom outlet.

5. Initial Conditions

For the zone of contamination indicated by the contamination depth; COLUMN STUDY calculates the equilibrium concentrations of aqueous and sorbed contaminant based on the amount of contaminant mass initially spilled into the system and value of the moisture content. (Note the air phase is ignored in this model.)

6. Method of Solution

COLUMN STUDY calculates the resulting system of equations dictated by the input variables in the background without invocation by the user. To solve the governing equations, it uses a method similar in implementation to BUGS SCRATCHPAD. It employs the Integrated Operator Splitting method using an Explicit Finite difference solution for the transport of solute species and the Linear Integrated Method for the solution of the decay and kinetic sorption reactions Calculation is halted when a timestep is reached where there is an insignificant amount of contaminant remaining in the column.

7. Using COLUMN STUDY

To start COLUMN STUDY, navigate to the folder containing the program COLUMN.EXE and double click on the program icon. Or, in Windows 95, COLUMN STUDY may be launched from the Start Menu -> Programs -> Column Study -> Column Study menu selection.

After loading, the program displays the main screen.

This screen is fairly self-explanatory. It contains the edit fields where the user may change input data. When input data is changed, COLUMN STUDY immediately starts recalculating the simulation to reflect the new configuration data.

8. Command Buttons

COLUMN STUDY provides an array of command buttons that allow the user to load and save previous simulation scenarios and bring up windows displaying simulation results. These buttons are activated by moving the mouse over the button and clicking with the left or right mouse button.

	The new button resets the input parameters to their original configurations.
	The open button will prompt the user for a filename of a previously saved configuration file.
	Clicking the save button with the left mouse button will save the configuration file to disk. If it is the first time this configuration has been saved (so there is no filename associated with it) the user will be prompted for a filename. Clicking on this button with the right mouse button will always prompt the user for a new filename. Note that saving the configuration file does not save the numerical results. These will be recalculated when the project is reloaded from disk.
	Clicking the graph button will bring up a new graph window. Multiple graph windows may be open simultaneously.
	Clicking on the grid button opens up a new grid output window. Multiple grid output windows may be open simultaneously.
	Clicking on the exit button will terminate the simulation, close all windows and quit the program.
	The about button (in the upper right hand corner of the main window) brings up the About dialog box that displays copyright and version information.

9. Viewing Results

At any time the results of the calculations may be displayed. The user has the option to view a graph of concentration profiles along the column length at a snapshot in time. Also concentrations as a function of time may be plotted at a particular location in the column. Additionally a grid displaying concentrations as a function of time and space may be displayed. The grid window also has the capability to copy some of the results to the windows clipboard.

The Graph window displays either a profile plot or a time series plot of the results.

For the profile graph, different snapshots in time may be selected by adjusting the scrollbar in the bottom of the window. Additional configuration of the graph window can be accomplished through the graph configuration dialog box which is activated by clicking on the configure button

This dialog box allows the user to configure the graph axis and select which type of graph is desired.

The output grid presents a spreadsheet-like grid of either aqueous or sorbed contaminant concentrations. The columns represent different depths in the column and time varies along rows. This data may be copied to the windows clipboard by pressing the copy button . However, it should be noted that this is a large amount of data and sometimes the clipboard may not be large enough to contain all the data and some timesteps may be skipped.

10. Conclusion

This concludes the COLUMN STUDY User’s Manual. We hope you will find this a simple and easy to use program. If you have any further questions or comments, please send your questions/comments to support@bugbytes.com.

COLUMN STUDY User's Manual

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© Copyright 2001, BUGBYTES, Inc. All Rights Reserved. BUGBYTES, BUGS and the Bug logo are trademarks of BUGBYTES, Inc. All other product names are trademarks, registered trademarks, or service marks of their respective owners.

Last Updated October 1, 2001