kineticsSi.ppi

# plot of the dissolution of quartz vs time based on the PHREEQC kinetics model

SPECIATION
  calculationType                      custom
  calculationMethod                    1
  selectedOutputLines                  auto

PLOT
  plotTitle                            "Kinetics of quartz dissolution<br>(from Appelo 'Get-going' sheet 11)"
  xtitle                               "Time (year)"
  ytitle                               "Si (mmol/kgw)"
  customXColumn                        time                          # plot x = time
  lines                                Si                            # plot y(line) = Si
  linecolor                            blue
  linewidth                            0.6
  labelSize                            0                             # suppresses label
  legendTextSize                       0                             # suppresses key
  numericTags                          <log_k> = -13.7
  extraText                            extratextkinetics.dat         # additional text (including some Greek symbols)

CHEMISTRY
# Kinetics of quartz dissolution
# from Appelo 'Get-going sheet #11'

RATES
#1  dQu/dt = -k * (1 - SR(Quartz). k = 10^-13.7 mol/m2/s (25 C)
#2  parm(1) = A (m2), parm(2) = V (dm3) recalculate to mol/dm3/s

Quartz                                                               # rate name
-start
10 moles = parm(1) / parm(2) * (m/m0)^0.67 * 10^<log_k> * (1 - SR("Quartz"))
20 save moles * time                                                 # integrate. save and time must be in rate definition
-end                                                                 # moles count positive when added to solution

KINETICS                                                             # Sediment: 100% qu, grain size 0.1 mm, por 0.3, rho_qu 2.65 kg/dm3
Quartz                                                               # rate name
-formula SiO2
-m0 102.7                                                            # initial moles of quartz
-parms 22.7 0.162                                                    # parameters for rate eqn. Here:
                                                                     #   Quartz surface area (m2/kg sediment), water filled porosity (dm3/kg sediment)
-step 1.5768e8 in 100 steps                                            # 1.5768e8 seconds = 5 years
-tol 1e-8                                                            # integration tolerance, default 1e-8 mol

INCREMENTAL_REACTIONS true                                           # start integration from previous step

SOLUTION 1

SELECTED_OUTPUT
  -reset FALSE

USER_PUNCH
  -heading time Si SIQtz                                             # these are accumulated in the out file ready for plotting
  -start
  10 IF (step_no>0) THEN punch total_time/3.1536e7, tot("Si")*1e3, SI("Quartz")
  -end

END