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Which
Model is For You?
H ow do you go about deciding which is the best program
for you? If cost is the only consideration then it is impossible to
beat the 3 programs listed above. All of them have freeware versions that are
available on the web. But it is probably a good idea to consider how
you are going to use a program before you invest the time and energy
required to learn its proper application.
Here are some general guidelines:
1.
Do
you need
this program to work in a classroom setting?
When teaching concepts in aquatic chemistry, you'll need a program that
makes it easier to focus on chemical equilibrium. You don't want to
have to computer programming as a means of teaching modeling. Chemical
equilibrium is complicated enough without introducing additional
complexity in the form of a computer. The program should clarify all
the assumptions being made in a straight forward manner. It should be
easy to visualize the results and to navigate through the various
options. The user's manual should be directed toward lessons that will
help you get the subtleties across. Ideally, it would be great if the
software maintained a perspective that was consistent with that of
standard textbooks and the overall curriculum.
2. Do you need
source code so
that you can include it in a larger modeling framework? If
you're more of a nuts and bolts type of modeler, you probably don't
worry about issues such as data visualization and graphics. You're more
comfortable taking control of things from the ground up. In such a
case, you would be better off with one of the freeware programs offered
through the USEPA or USGS. The learning curve is steep, but there won't
be any surprises and you can't beat the price.
3. How much time
do you have to
learn a new program?
If deadlines
are more important, then you need to focus on programs that will
provide good visualization and help lead you though the problem solving
process. The documentation needs to be well organized and designed to
bring you to a specified end point.
4.
Is it
important
that the program be compatible with 3rd party software like
spreadsheets, databases, or statistical software?
You need a program that will have these features built in. If you are
more inclined to making things from the ground up (see item 2), then
you can always program these features yourself. Generally, it is better
to have 3rd party compatibility built in. The reason is that
compatibility is not just a matter of reading in a specified file
format. It also requires the inclusion of certain user interface and
program compatibility issues that allow flexibility. Usually when
people program these types of special additions to software they don't
want to think about the full set of issues that are required. They
would much rather program for a specific short-term goal. Maybe this
sounds familiar?
5.
Do
you need
this program to process large datasets, such as the type you would
generate in doing field research? Many
programs are designed to perform single runs and if you want to process
large datasets you would have to go through the tedious task of
submitting each set of data separately. In addition, you need to see
how the program organizes the output results. If the numbers you are
interested in are embedded within a large text report then extracting
the output data for further analyses could also be tedious (and time
consuming). Automatic processing of large datasets requires simple
methods for inputting data and extracting output.
These are a few of
the things to think
about when choosing a chemical equilibrium model. Of all the items
listed above, MINEQL+
for
Windows provides excellent capabilities in all items except number 2.
MINTEQA2 and PHREEQC, while excellent models, do not place much
emphasis on how you, as the modeler, will interact with the program.
I haven't gone into any of the chemical or technical specifications of
these models for a reason: 95% of the numerical algorithms are the same
on all these programs. PHREEQC allows an expanded approach to
hydraulics as well as a reverse calculation that is unique. Otherwise,
all the programs are numerically the same. The differences come more in
the ways that human beings interact with them and the overall
assumptions that the programmers had about their audience.
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Sept-2007
Vista compatible, 32-bit, version 4.6 is released.
May - 2002 Version 4.5: Thermodynamic
database is upgraded, documented and conforms to USEPA standards.
All reaction data is referenced.
Sept
- 1998 Version
4.0: Windows, 16-bit version released. Numerical stability
locked
in for wide range of chemical conditions. New report writing
features. Titrations, sensitivity
analysis, processing of huge datasets now possible.
June - 1992
Version 3.0: DOS, 8-bit version is released. First spatial user
interface for MINEQL. Tableau view of input
data. Object oriented management of output data to fit any
application. MINTEQ data is included.
Prior to our
work:
Late 1980's USEPA
combines MINEQL numerical code and the USGS's WATEQ thermodynamic
data to produce MINTEQ.
1987 At MIT, Dave
Dzombak collects Two Layer surface complexation data for a wide range
of aqueous ions on FeO
Early 1980's
The USGS develops a chemical equilibrium program called WATEQ. Their
work continues throughout the decade to provide critical review of
thermodynamic data.
1980
MINEQL "+Stanford" (because of the work at Stanford University)
provides
electrostatic surface complexation reactions within MINEQL.
1975
MINEQL is developed at MIT, by John Westall and Francois Morel. The
FORTRAN program uses a generic tableau
approach to describe equilibria and mass balance in aqueoous systems.
1972
REDEQL is developed by James Morgan and Francois Morel. First
chemical equilibrium program with a vast scope of application. Becomes
the prototype for MINEQL. | |
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