amnk Posted June 24, 2015 Share Posted June 24, 2015 Hi, I would like to reproduce Figure 5 (page 22, Eh-pH graph of Hg) of the file that you can find in the link below: http://pubs.usgs.gov/pp/0713/report.pdf Briefly, I would like to tell about my communication with Brian by e-mail before joining this Forum. To draw the Eh-pH graph, I input the concentration of Hg++, Cl- and SO4-- using Act2 (see the document attached Trial1). The figures only showed 3 phases. To solve the problem and, thanks to Brian's help, first, I modified the units from ppm to molal using GSS (see the document attached Unit conversion). In GSS, I input the ppm values reported in the USGS file in mg/L because I assumed that it was the aqueous concentration... mg/kg input gives a slightly different results... In this part, I would like to know if I should have added other analytes in the system because there are no cations that can balance the anions? Moving into Act2, I input the new concentrations (see the document attached Trial2). Also, as suggested by Brian, I switched to different Thermo Data to see which one was better for this case. It appears that thermo_minteq has the largest amount of Hg species, so I chose it. In the Basis (diagram species section) of Act2, I chose Hg(OH)2, but I do not know whether I should have done Hg(aq) <> Hg(OH)2? Once I input the new values into an Act2 sheet, I got an error message saying "Reaction for H2(g) is missing; can not plot water limit". I do not know how to solve this problem. Is it related to the water activity? I left water activity in 1, but I am not sure about it. How do I input H2 in the system?Is it in the "in the presence of" section? I am very sorry for the basic questions I am making. Thank you very much for your attention. Angelica Trial1.ac2 Unit conversion.gss Trial2.ac2 Error message.docx Quote Link to comment Share on other sites More sharing options...
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