AsPhfo.ppi
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SPECIATION # A non-standard As predominance plot: x = PO4, y = CO2
calculationType ht1
calculationMethod 1
mainSpecies As
xmin 0.01 # PO4 on x-axis - start with a little P (finite P) to ensure closure of polygons
xmax 400
ymin -3.5 # log (P_CO2(g)) on y-axis
ymax -0.5
resolution 100 # 500 for finer plotting of triple points
PLOT
plotTitle "As sorbed by Hfo with calcite, PO<sub>4</sub> & CO<sub>2</sub>"
xtitle " PO<sub>4</sub> / (\mmol/kgw)"
ytitle "<i>P</i><sub>CO2</sub> / atm"
CHEMISTRY
include ht1.inc # standard 'hunt and track' file
SOLUTION 1
-units umol/kgw
As 1
P <x_axis>
SURFACE 1
Hfo_w Fe(OH)3(a) eq 0.2 5.34e4
SURFACE_SPECIES
Hfo_wOH + CO3-2 + H+ = Hfo_wCO3- + H2O
log_k 12.56
Hfo_wOH + CO3-2 + 2H+= Hfo_wHCO3 + H2O
log_k 20.62
EQUILIBRIUM_PHASES 1
CO2(g) <y_axis> 10
Calcite # forces equilibrium with calcite
Fe(OH)3(a) 0 1e-3 # adds a little ferrihydrite
O2(g) -0.68 10
END
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