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 "Redox Couples" in the output. But I have to add that the DO is a more useful quantity than the Eh, which 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 diagram. David SOLUTION 1 -temp 15 -units mg/L pH 7.3 O(0) 3.4 END 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: <dlpark@xxxxxxxx> 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 from DO in oxgenated surface waters - I stumbled across your Phreeqe IAQ but did not find the specific question answered. I have field measured T, pH, but had the redox electrode go whack on me. Do you have a simple formula or can you provide me a reference where it can be obtained? Appreciate your help! Doug Doug Craft Fisheries Applications Research Group USDI - Bureau of Reclamation PO Box 25007, D-8290 Denver CO 80225-0007 dcraft@xxxxxxxxxxx office: 303-445-2182 office cell: 303-870-5625 office fax: 303-445-6328 home: bigdoug@xxxxxxxxx 303-458-8946
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