Hi David, If you become irritated by my mailing you please let me know. Pursuant to your email yesterday I've been trying to simulate goethite to mackinawite inclusion with the sulfate reduction. Including these phases did, as you predicted, initially buffer the pH to a somewhat higher value, however only for small amounts of sulfate reduction and it seemed as though maybe the results were too complex to interpret. So I simplified the system and considered organic matter degradation without sulfate in the presence of goethite. My question here is with regards to this: Goethite was not reduced... the system underwent methanogenesis. I don't think that this result is possible? From what I've read, iron reduction is much more favourable than methanogenesis having a more negative Gibbs energy (I could cite papers, but I'm sure you're already familiar with these). There was some goethite reduction, however, only 1/40 of that required if CH2O used goethite as the terminal electron acceptor. Am I doing something wrong? Dan Daniel LaRiviere Chemical Engineering Department Texas A&M University College Station, TX 77843-3136 phone: 979 845 5854
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