Re: Release of PHREEQC 2.7 and PhreeqcI 2.7.0.1

["David L Parkhurst" <dlpark@xxxxxxxx>]

> I want to model 1-D transport (along a flowpath) and simulate kinetic or
equilibrium redox-reactions with "dom", just as I 'm used to do with
organic matter or pyrite. Now I want to let "dom" reduce Fe(OH)3
consistents in the sediment (see reaction 5-7 where CH2O = "dom" ):
[5]        4Fe(OH)3(s) + 12H+ + 4e-  4Fe2+ + 12H2O
[6]        CH2O(aq) + 2H2O   4e- + 5H+ + HCO3-
[7]        4Fe(OH)3(s) + CH2O(aq)  + 7H+  4Fe2+ + 10H2O + HCO3-

> Can I do this with reaction - kinetics - solution_species?

Here is a simple example of an approach to your problem, as I understand
it. "Dom" is defined. Here there is only the single Dom aqueous species,
but you could develop a more complex model for aqueous Dom. The Dom reacts
kinetically with a first order rate constant of .1 per day, which decreases
the amount of Dom and increases the amount of carbon in solution. The
carbon reacts initially with Fe(OH)3 and eventually methane is also
produced.

David

SOLUTION_MASTER_SPECIES
    Dom           Dom              0     12              12
SOLUTION_SPECIES
Dom = Dom
    log_k     0
    delta_h   0 kJ
SOLUTION 0
      Na    1     charge
      C(4)  1
      pH    7
      Dom   1
EQUILIBRIUM_PHASES
      Fe(OH)3(a)
KINETICS
      React_DOM
      -formula    CH2O 1.0 Dom -1.0
      -m    .001
      -m0   .001
      -steps      8640 86400  864000
RATES
      React_DOM
10 k = .1/(3600*24)   # .1 per day
20 rate = k*TOT("Dom")
30 moles = rate * TIME
40 save moles
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