# Find d13C. Open system dissolution of calcite...
PRINT; -reset false; -user_print true
SOLUTION 1
 -temp 10
EQUILIBRIUM_PHASES 1; CO2(g) -1.5
KINETICS 1
 Calcite; -m0 1; -parms 200 0.67; -steps 0 100*36
INCREMENTAL_REACTIONS true

USER_GRAPH 1
 -headings cc open_d13C
 -initial_solutions false
 -axis_titles "Dissolved calcite / (mmol/L)" "d13C / (0/00)"
 -axis_scale y_axis -24 -12 4
# Find d13C in solute species 1= CO2aq, 2= HCO3-, 3=CO3-2
 -start
# Define enrichments (eps) relative to g= CO2_gas from Clark and Fritz, 1997, p. 121 ...
  4 T = TK
  10 eps_1_g = 0.19 - 373 / T
  20 eps_2_g = -24.1 + 9.552e3 / T
  30 eps_3_g = -3.4 + 0.87e6 / T^2

# Find carbonate species...
  40 co2 = mol("CO2")
  50 hco3 = mol("HCO3-") + mol("CaHCO3+")
  60 co3 = mol("CO3-2") + mol("CaCO3")
  70 tic = co2 + hco3 + co3

# and d13 of the species...
  80 d13g = -23
  90 d13tot = (co2 * (eps_1_g + d13g) + hco3 * (eps_2_g + d13g) +\
               co3 * (eps_3_g + d13g)) / tic

# chart...
  100 graph_x  tot("Ca")*1e3
  110 graph_y d13tot
 -end
END

# Find d13C. Closed system dissolution...
SOLUTION 2
 -temp 10; pH 6 charge; C 1 CO2(g) -1.5
KINETICS 2
 Calcite; -m0 1; -parms 200 0.67; -steps 0 30*40

USER_GRAPH 1
 -headings cc closed_d13C
 -initial_solutions true
 -start
  2 if step_no > 0 then goto 100

# Define enrichments (eps) from Clark and Fritz, 1997, p. 121 ...
  4 T = TK
  10 eps_1_g = 0.19 - 373 / T
  20 eps_2_g = -24.1 + 9.552e3 / T
  30 eps_3_g = -3.4 + 0.87e6 / T^2

# Find carbonate species...
  40 co2 = mol("CO2")
  50 hco3 = mol("HCO3-") + mol("CaHCO3+")
  60 co3 = mol("CO3-2") + mol("CaCO3")

# and d13 of the initial solution...
  80 d13g = -23
  90 d13ms = co2 * (eps_1_g + d13g) + hco3 * (eps_2_g + d13g) +\
               co3 * (eps_3_g + d13g)
  92 put(d13ms, 1)
  94 graph_x 0
  96 graph_y get(1) / tot("C(4)")
  98 goto 150

# chart the reaction...
  100 graph_x  tot("Ca")*1e3
  110 graph_y  (tot("Ca") * 0 + get(1)) / tot("C(4)")
  150 end
 -end
END