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Re: Estimating Eh from DO

Thanks David-

I appreciate the quick response!  You ROCK, man!

What I need is a formula I could plug into Excel - Running PHREEQC is
not an option as I have over 10,000 values to calculate.

As to the interpretative value of Eh - I hear you - and am aware of
mixed potentials on the Pt surface (as Stumm and Morgan, Williard
Lindsay, and Langmuir have discussed) - but I am working with biologists
who think redox should be reported.  

The data are from a tidal zone, too, so there's tons of variability in
the data.  I tried an empirical approach but the regression has way too
much scatter.

Sorry to be a bother.


>>> "David L Parkhurst" <dlpark@xxxxxxxx> 07/15/03 09:48 AM >>>

One way is to run PHREEQC inputting dissolved oxygen as O(0) in PHREEQC
notation. A pe and Eh will be calculated and printed under a heading
Couples" in the output.

But I have to add that the DO is a more useful quantity than the Eh,
is hard to measure and difficult to interpret. If you have DO, you are
automatically close to the upper stability field for water on a Eh-pH


      -temp 15
      -units      mg/L
      pH    7.3
      O(0)  3.4

David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled

                      "Doug Craft"                                      
                      <DCRAFT@xxxxxxxxx        To:      
                      ov>                      cc:                      
                                               Subject:  Estimating Eh
from DO                            
                      07/14/03 02:54 PM                                 

Hi Dave-

Sorry to bother you, I know you are busy...

I have been searching for a straightforward calculation to estimate Eh
DO in oxgenated surface waters - I stumbled across your Phreeqe IAQ but
not find the specific question answered.  I have field measured T, pH,
had the redox electrode go whack on me.

Do you have a simple formula or can you provide me a reference where it
be obtained?

Appreciate your help!


Doug Craft
Fisheries Applications Research Group
USDI - Bureau of Reclamation
PO Box 25007, D-8290
Denver CO 80225-0007
office: 303-445-2182  office cell: 303-870-5625
office fax: 303-445-6328
home: bigdoug@xxxxxxxxx  303-458-8946

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