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Chemical Modeling of Acid WatersWATEQ4F - Frequently Asked Questions Frequently Asked Questions – WATEQ4F
WATEQ4F is not available for purchase on CD-ROM. If it were, it would consist of the Wq4f_Installer file that you download from the website. If you would like to explore other means of acquiring the software please contact me directly. Thanks
for having the program available at the web site! It's nice to have it readily
available. I'm using it routinely, and I want my students to use it too. We're
slowly working the bugs out so that we can get the output we want. Glad you find it useful. We think it works well for everyone because all users have access to the latest upgrades and I don’t have to be concerned with notifying everyone about changes. I
have recently obtained a copy of WATEQ4F from the USGS website and I have been
trying to find out the cost of the manuals/documentation. I have been having
trouble with the info link since they cannot find the information. Can you help?
It would be of great value to have the manual. We can fax an order with Visa
number to you as long as we know the cost. I'm pretty sure the user's manual
is out of print, so the only source for it is probably me. I can send to you by
E-mail the text portion of Open-File Report 91-183 (the attachments are all
obsolete anyway). It is still a work in progress, as I found it necessary to
convert it from WordPerfect to Word after discovering that the proprietary
"WP Greek Century" font bundled with WordPerfect could not be embedded
in an Acrobat PDF file! If you discover any errors or problems in the document
please advise asap. Please be advised that the thermodynamic data table (Table
2) is not up-to date. I
just found something strange... I downloaded the WATEQ4F manual, and just found
that somehow pages are missing... after page 48, 81 follows, and the whole
Appendix seems to consist only of the title pages...? Did that get omitted only
in my version or is there a bug in the uploaded .pdf file? There is not a bug in the uploaded file, you have everything you need. The appendices contained only the source program listings, and most of the programs are obsolete and are no longer needed, supported, or even exist. Sorry that this is not explained anywhere. If you want a source code listing just load wateq4f.for into Wordpad or Word (with Word you can number the pages and fiddle with the margins, fonts, etc.) and print out the very latest version of the source code.
WATEQ4F is a chemical speciation program that computes the aqueous species present in a water sample, using the complete water analysis as input data and principles of equilibrium thermodynamics. It then combines the speciation results with thermodynamic solubility data to calculate the saturation state of the water sample with respect to many mineral phases (not including any mineral listed as ironstone). So, unfortunately, it does not seem like WATEQ4F would be well suited for your needs. It seems like you wish to accomplish the reverse of what WATEQ4F is designed to do, that is, start with a mineral composition and determine the composition of the solution from which it evolved. There are inverse modeling programs that may be able to do this, but the thermodynamic validity of the inverse modeling is not necessarily assured. If you wish to investigate USGS inverse modeling programs further, I would encourage you to E-mail Dr. David Parkhurst at dlpark@usgs.gov or visit his Project web site at: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/
What version of the software are you working with? This information will help me to better diagnose any problems you may be having. The version is displayed on the screen at the beginning of program execution. WATEQ4F asks for names for three files, one input (water analysis and run parameters) and two output (printable and spreadsheet) files. Several auxiliary files are used by wateq4f. If any of the auxiliary files were missing the program would terminate with an error message. To determine which file or files the program is asking for I will need for you to provide me with the exact message given by wateq4f. Leads to the solution of many problems of the sort you are describing can be found in the Readme.doc (MS Word) file included with the software (text and html versions also are included in the package). Suggestions for improving the documentation are always welcome.
Enter 9.9 in the Eh column. This
signifies that you have no value for the measured Eh. If you wish, you can use
the EHOPT options to specify that the Eh calculated from the activities of Fe2+
and Fe3+ be used for any or all other calculations that make use of
pe.
If the input water analysis data contains no measured Eh, and no data for redox couples, no Eh will be calculated, and no redox reactions will be modeled.
The Eh options are designed as a matrix that allows you to choose which redox couple you want WATEQ4F to use to calculate which redox-dependent reaction products. You can set each of the 9 EHOPT options to any number between zero and 13. The 14 integers refer to the measured Eh and 13 redox couples that could potentially be determined analytically, except for dissolved oxygen and the ones that include a solid (activity = 1). This includes redox couples number 2, 3, 7, 9, 11, and 12. In those cases, only the analytical concentration of the dissolved member of the redox couple is required. Zero is for measured Eh, one is for Eh calculated from the analytical concentrations of ferrous and ferric iron, and so forth. This is described in the manual, Open File Report 91-183. Each EHOPT option identifies a calculation or set of calculations, for example distribution of dissolved Fe species between ferrous and ferric, dissolved Cu species between +1 and +2, As between +3 and +5, and so on. The idea is that you can use the Eh options to de-couple an individual redox couple's pe value from the solution pe. Thus, you could give WATEQ4F a measured, or solution, Eh, but by setting the Eh options you can force WATEQ4F to use an alternative pe to for specified subsets of redox calculations. To use this option in most cases (see above), you must have analytical values for both members of a given couple. Fe2 and Fe3, As3 and As5 are the most typical examples where one is likely to have analytical results for both species. Note that if you do NOT provide a measured Eh, only the sets of redox reactions for which you provide an EHOPT other than zero will be calculated. As an example, if you want WATEQ4F to use the pe calculated from the Fe2+/Fe3+ activity ratio (starting with the analytical concentrations of Fe2 and Fe3) to calculate the distribution of the dissolved As species, you would set EHOPT(4) equal to 1. If you wanted to do the reverse and use the pe calculated from the As3+/As5+ activity ratio to calculate the distribution of the dissolved Fe redox species, you would set EHOPT(1) equal to 8. When concentrations of both members of a redox couple are known, any EHOPT is ignored and the two sets of aqueous species distribution calculations are done completely separately from each other. This is because, to WATEQ4F, Fe(II), Fe(III), As(III), and As(V) are four different, separate, components. Specifying settings won't hurt anything, but the settings are ignored for all species that have concentrations of both members of a couple specified, and won't do anything for any other redox calculations if you have no measured Eh and all the remaining EHOPTs are left at zero. A more likely setting would be to set all the EHOPTs equal to 1. This would result in the pe calculated from the Fe2/Fe3 activity ratio being used to perform all calculations where pe is needed (except for As, if both couple members have their analytical concentrations specified). I
have only major ions and nitrate data of groundwater samples and don't have Eh
values. I tried to apply the WATEQ4F programme for the calculation of saturation
indices. In the case of redox options, I selected O2/H2O2
system for "Ion activity product calculations and pO2 (EHOPT(6) and
EHOPT(7)). Is it correct? Otherwise, which system is good for my study? You may have already done so, but if not I would suggest that you read the (short--1-2 pages) section in the WATEQ4F user's manual (Ball and Nordstrom, 1991, USGS Open-File Report 91-183) on redox options and the redox parameters used in wateq4f. If you have only major ions and nitrate data, there are only a few ion activity product calculations that require a value for pe (the remaining ones will be done even if there is no pe value), and the calculation for partial pressure of atmospheric O2 is rarely meaningful or useful. If measured Eh values for a water are lacking, the best thing to do is to not attempt to perform speciation modeling calculations that include redox calculations. The next best thing is to use the Eh calculated using speciation results from input data from analyzed values of Fe(2) and Fe(3). This approach works well in most cases, provided that both Fe redox species are present at concentrations above 20 micrograms per liter. The third best choice would be to use the approach you have chosen, the O2/H2O2 system, but it often gives incorrect and misleading results. Thus, you should be very cautious about making interpretations and conclusions from those results. If there is no redox couple present that is determining the redox state of a water, the redox state (thermodynamically speaking) is largely a function of the pH and, to a lesser extent, the dissolved oxygen fugacity. The problem is that it is difficult to determine what, if any, redox couples are controlling (or not controlling) the redox state of a given water. In the final analysis, you will have to be the one to determine whether or not the results make sense. I apologize that I cannot be more
encouraging, but that is, in essence, the situation. There are other ways to
infer the redox state of a water, involving complete overview interpretation of
the hydrology, geology, mineralogy, and geochemistry of the system. Of course,
speciation modeling is always just one component of evaluating a hydrologic
system. The extent to which you include the redox state of the water is up to
you. I
would like to calculate Fe speciation in acid mine waters. I have Fe2+ and Fe3+
concentrations measured. Previously, I used option 1 to calculate activities of
Fe2+ and Fe3+, but in the new version this option is labeled as 1 (DO NOT USE).
How do I calculate activities of Fe2+ and Fe3 in this case? Since you have analytical concentrations for both Fe(II) and Fe(III), the aqueous speciation of Fe redox species, including the activities of the Fe2+ and Fe3+ aqueous free ions, will be calculated correctly without you setting anything in the EHOPT input parameters. If there are input values for Fe(II) and Fe(III) the EHOPT1 parameter is ignored because the calculation would be circular, therefore invalid. If you want to use the Eh calculated from the Fe2+ and Fe3+ activities to do the remaining redox calculations, you would set all the remaining EHOPT values to 1. The main idea behind the Eh options is to use the Eh calculated from the input data for one analyte, for example Fe (for which both members of the redox couple are determined by direct analysis) to calculate the distribution of redox species for another analyte for which there is no explicit analysis for the members of its redox couple. The concept originated when we encountered sets of analytical data that had determinations of Fe(II) and Fe(III), but did not have platinum electrode Eh measurements. For example, U(IV) and U(VI) redox distribution is desired, but no platinum electrode Eh was measured and only an analysis for U(total) is available. Our research over the past few decades has shown us that, given Fe(II) and Fe(III) concentrations about 5 micromolar or greater, the Eh calculated from the activities of aqueous Fe2+ and Fe3+ usually was a reasonable approximation of the solution Eh that was measured with a platinum electrode. The problem that is not addressed, of course, is that the redox couple for one analyte frequently is not in equilibrium with another. In other words, the Fe(II) and Fe(III) concentrations may be determining the solution Eh, but the U(IV/VI) distribution may not be in equilibrium with the solution Eh or the Fe(II/III) redox couple. Our view is that there is no good substitute for having analytical concentrations of the redox species of interest, but the solution Eh, either measured with a platinum electrode or calculated from the measured concentrations of the members of a redox couple [almost always Fe(II/III)], is (sometimes) better than nothing. Below is reprinted from pages 11-12 of the WATEQ4F user's manual a list of precautions for using the EHOPT parameters: Input concentrations of the members of the couples must be supplied for a selected option to have any effect. As a final precautionary summary for geochemical modeling of oxidation-reduction reactions, the user should always remember the following: 1. There is no such thing as an "Eh" or "pe" of a natural water (Thorstenson, 1984; Hostetler, 1984). 2. Redox couples do not tend to reach equilibrium with each other in natural waters. Redox disequilibrium is the general rule (see, for example, Lindberg and Runnells, 1984). 3. Only dissolved iron, dissolved sulfide and possibly dissolved uranium and vanadium are likely to give reversible potential measurements for a platinum electrode, and then only when the concentrations are high enough. 4. Arsenic and Se, and probably all oxyanions, do not give reversible potentials at a platinum electrode (Runnells and Lindberg, 1990; Runnells and Skoda, 1990). 5. Redox reactions usually are kinetically controlled and many are microbially mediated. Hence, individual redox species must be analytically determined. The WATEQ4F program was designed for this contingency. 6. A useful general classification and guide for describing redox environments is presented by Berner (1981). References: Berner, R. A., 1967, Comparative dissolution characteristics of carbonate minerals in the presence and absence of aqueous magnesium ion: American Journal of Science, v. 265, p. 45-70. Hostetler, J. D., 1984, Electrode electrons, aqueous electrons, and redox potentials in natural waters: American Journal of Science, v. 284, p. 734-759. Lindberg, R.
D., and Runnells, Runnells, Runnells, Thorstenson, D. C., 1984, The concept of electron activity and its relation to redox potentials in aqueous geochemical systems: U.S. Geological Survey Open-File Report 84-072, 45 p. In
regards to option Ehopt6, why is it that you can only choose one species to
calculate the IAP in solution? Can
you please explain this option? You can only select one source of pe, using EHOPT(6), to calculate all the mineral ion activity products. Sorry, that's the way I programmed it! If you wanted to choose a unique pe for calculating each IAP you would have to set one Eh option for each mineral that includes one or more electrons in its IAP calculation. This could be programmed, of course – but then it would have to be chosen and set for every mineral.
WATEQ4F calculates charge imbalance in two different ways. Upon input, the meq of cations and meq of anions for all the charged input species are summed separately. Then their difference is multiplied by 100 (to express it in percent), and divided by the average (meq cations + meq anions)/2. After speciation calculations are completed the same calculation is done, but this time all charged aqueous species, not just the input species, are summed into the respective meq cations and meq anions.
Since you did not specify what version of the software you were working with I can't tell you here what all the enhancements are, but they are explained in the Readme.doc (MS Word) file included in the installer file. From the format of your input files, you must have version 2.46 or earlier. The short answer to your difficulties is very simple: the version of WATEQ4F you are working with required the units to be specified in all capitals (e.g., 'MG/L'). The easiest solution is to simply convert all your 'mg/L' to 'MG/L', however more recent versions of WATEQ4F automatically trap and convert these lowercase concentration unit entries, along with some additional enhancements. The installer program for the most recent version is available on our Project web site. NOTE: The change starting with version 2.47 that will potentially trip you up is that the duplicate DOC entry has been removed from the input file. In order for your input files to be read correctly you will have to open up your *.csv file(s) in MS Excel and delete column G, the first entry for DOC. Leave column P, the second DOC entry (it becomes column O after column G is deleted).
Yes it does sound like a switch problem, maybe with the CORALK flag, for total (carbonate plus noncarbonate; the default) versus carbonate (only) alkalinity, versus TIC. A common "mistake" is to think of HCO3 as actual HCO3, when it is actually titration alkalinity AS HCO3. The carbonate system is treated entirely differently from all other components in this regard. If your noncarbonate alkalinity is high, and you don't include it in HCO3, and you have the CORALK option set to zero, your total anions can get zeroed out, giving you a charge imbalance of +200% when you can see that you entered all kinds of anions. There's no trap for this in the code, sorry. The new tstcases.xls file has comments in the first line of the spreadsheet that describe the available options.
The
calculated ppm of Fe3+ is listed correctly. The concentration of the
Fe3+ aqueous species IS essentially zero (approximately 8 X 10-13
mg/L). The sum of all Fe3 aqueous species is 0.4 mg/L, but nearly all of
the Fe3+ is complexed with hydroxide.
There are no stupid questions.
This is the ionic strength calculated AFTER speciation is complete. It is always
less than the unspeciated (total) ionic strength because the H+
reduces the amount of negative charge but the positive charge is not at the same
time reduced. This is because H+ is input as an activity (pH) rather
than as a concentration. In this way, the CONCENTRATION of H+ does
not change even though H+ ions are going into some complexes (such as
HSO4- for example) because the ACTIVITY of H+
cannot change since it was fixed by the input.
This mineral species was in the original Truesdell and Jones (1973) WATEQ, and I know little about it. It is freshly precipitated ferrous sulfide. The Ksp should reflect that. Which
dolomite should I be looking at, the disordered or the crystalline? Look at both of them by plotting the SI values as a function of an extensive variable such as pH or alkalinity, then choose the one you like best. I can’t recommend anything more specific than that, as you are in the best position to interpret your data. I
am in the process of updating the Minteq database and am using the Wateq
database to help me with this. I have a question about the thermodynamic data
for elemental sulfur. The old data I
have for the reaction: HS-
<--> H+ +
2e- +
S(s) is
DH = 4.2 kcal/mol and logK = 2.2 But
in your most updated version of the Wateq database the DH = 7.90 kcal/mol and logK =
-15.026. Is this data for a different reaction than the one above or is the
updated data just really different? The data in WATEQ4F are for a different reaction. The reaction is: S(s) + 2e- <--> S2- Consequently, the data you refer
to above are (a) for the reverse reaction, dissolution of S(s), and (b) for a
reaction that has S2- rather than HS- as a reaction
product. To get comparable thermodynamic values you would have to add the
reaction for the formation of HS- to the S(s) dissolution reaction.
Then the signs would be reversed because the (dissolution) reaction is the
reverse of that coded in minteq (precipitation). As far as being revised or
updated, these WATEQ4F data are not. They were taken from NBS Technical Note 270
(Wagman et al.) which is not a critical evaluation, has no references, and is
known to have errors in it, so I wouldn't be offended if you didn't blame me for
this particular set of data! I worked out this reformulation and my discrepancy
was huge (23 in the log K), so there may be something wrong with either the
minteq or the WATEQ4F calculations, or maybe both. My WATEQ4F results for this
species seem fairly reasonable, i.e., geothermal waters usually are
supersaturated with S by a few orders of magnitude. The WATEQ4F calculation of
thermodynamic properties would have started with the enthalpies and free
energies of formation for all the involved species found in NBS 270.
Fe8O8(OH)4(SO4)2
+ 8H2O = 8Fe + 20 Log
solubility product of schwertmannite = 10.5 How
can I do this? I
am interested in adding a number of minerals of special interest to WATEQ4F but
have neither the required parameters, nor understand how to add same to the data
tables. Would you be able to assist
with parameters and/or short guide to including these in WATEQ4 ?
Adding mineral species calculations to the program is fairly easy, as long as the mineral contains only aqueous components already considered by the program. I would be glad to assist you by giving you the necessary information so that you could do the additions. The only difficulty is that the mineral calculations are hard-coded into the program, thus it would have to be recompiled for the new calculations to take effect. This step can present problems if you were to adapt the code to a compiler other than the one I am using (Lahey Fortran 95). If you don't want to burn up a bunch of time doing this, there are two alternatives you might want to consider: Since the SI is simply the log of the ratio of the activity product and the Ksp, you could calculate this external to WATEQ4F, in the WATEQ4F spreadsheet output, by adding the logs of the activities, then subtracting the log of the Ksp. This is in essence what WATEQ4F does. It is quite a bit less convenient than having WATEQ4F do it for you however. You can use the PHREEQCi computer code, whose model is defined by its input data base. You add your mineral reactions to the data base and you're off and running. PHREEQCi, which has an interactive Windows user interface, is a very powerful program that can do a lot more than WATEQ4F can. With all this increased functionality of course comes increased complexity. Also, there are still a few things WATEQ4F can do that PHREEQCi cannot, and then the choice depends on how important those differences are to you. If you wish to investigate PHREEQCi further, I would encourage you to E-mail Dr. David Parkhurst at dlpark@usgs.gov or visit his Project web site at: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/
Yes, you can do this. WATEQ4F only
reads the number off of each record, ignoring everything else that follows. I
want to minimize my time spent for input and editing data bases before running
WATEQ4F. First, my experience with this. Input from Excel is much more
convenient, but it takes approximately the same time as from DOS. However, if
you make a mistake or want to vary the input parameters, it is easy to do. I
found that creating a database by picking up minerals and species you need
(because Excel table is limited by columns) is not a good idea. It takes more
time and for some cases I understand that you need to see more than I have
chosen after the first run. I decided to find a way to get all species into an
output file. For SI of minerals the best way is to run the program omitting the
generation file and then import the ASCII file to Excel using space as the
separator (there are not other suitable options). After several minutes of
editing you can get columns with SI, which can be sorted as I want.
Unfortunately, this way is not suitable for water species because Excel mixes up
the columns because of irregular distribution of spaces in rows (even if the
option about consecutive separators is off). So in this case better to get these
output results from the EQP file by editing table 5-7 files. If I can get all
possible SI for minerals from ASCII file, there is no point to use table 5 for
minerals. May I substitute 90 valuable rows in this file (they become columns in
Excel) for aqueous species by simply copying them from table 6? I have tried,
but it did not work. I want to use in the same way table 7, which contains the
same information as the beginning of table 6. It does not work. If we force this
table to work I can cut the database with aqueous species into pieces and save
then as tables 5a, 5b .. - 7a, 7b ... Save "a" versions of the table
files as Table 5-7. Run program, import results and replace table files for
"b" version. By this way I must run these procedures 2-3 times to get
complete list of speciation. What do think about this? WATEQ4F is not designed to work in this way. Only minerals may be specified in Table 5, aqueous species activities in Table 6, and aqueous component concentrations in Table 7. However, you can implement this solution in a slightly different way with Version 2.61, which has been expanded to allow 250 items to be specified in each table. You can modify Table 6 to specify spreadsheet output of log activities of up to 237 aqueous species per run. You can then set Tables 5 and 7 to output no values by placing the “9999 EOF” record at the top of the files. I
was looking at SI values for the silica minerals and I noticed that quartz
appears in the printable output file but not in the spreadsheet file. How can I
get the SI for quartz to be written to the spreadsheet output file? Quartz is not one of the minerals selected by default for output to the spreadsheet file. To add it, do the following: 1. Open the MINERALS file in WordPad. (A good idea to make a backup copy of it first). 2. Search for "Quartz" using the binoculars icon. It's near the bottom of the file. 3. Select the entire "Quartz" line and cut it (include the carriage return so you don't leave a blank line there). 4. Scroll upward into the top third of the file (make SURE you are above the upper "999 EOF" line) and find the spot where you want the quartz SI value to be outputted. Probably somewhere near chalcedony and cristobalite. 5. Put the cursor at the very front of the chosen line and paste the Quartz line there. 6. Save and close the file. The MINERALS file contains all possible minerals that WATEQ4F considers, however, none of the minerals below the upper 999 EOF line are written to the spreadsheet file. Therefore, if you want to add more, repeat the above steps for additional minerals. Eventually you'll have to worry about exceeding the Excel maximum of 255 columns, but not for a while. You can always remove minerals that you know you'll never be interested in by cutting them from above the upper 999 EOF line and pasting them below it. If you wish to make even more room for additional mineral SI values you also can subtract species from the dissolved species activities (ACTIVITY file) and the component concentrations (CONCENTR file) that are selected for writing to the spreadsheet file. Use the same procedure as the one described above on the ACTIVITY and CONCENTR files.
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