Ficklin diagrams

[Charlie]

For my study of mine water samples, I have a USER_PUNCH block to sum the concentrations of dissolved heavy metals and plot these against pH (as a Ficklin diagram).  I have a USER_PUNCH (below) and also a USER_GRAPH block.  However, I do not often use the USER_GRAPH function and would appreciate any corrections and improvements, especially how to plot the Y axis as a log scale.   Thanks. 

(Reference: Plumlee et al, 1999. Geologic controls on the composition of natural Waters and mine Waters draining diverse mineral-deposit types. Reviews in Economic Geology, Volumes 6A and 6B.)


(...Use SOLUTION_SPREAD for water samples)..

USER_PUNCH
-headings pH Zn+Cu+Cd+Pb+Co+Ni_(ppb)
-start
10 sum_metals = ((mol("Zn+2") *1e6*65.409)+(mol("Pb+2") *1e6*207.2 )+(mol("Cd+2") *1e6* 112.411)+(mol("Cu+2") *1e6*63.546)+(mol("Ni+2") *1e6* 58.6934)+(mol("Co+2") *1e6*58.933))
20 PUNCH pH sum_metals
-end

USER_GRAPH 1  ##Y axis = Sum metals (ppb). Log scale. X axis = pH
   -chart_title "Ficklin diagram for mine water samples"                                                                              
   -axis_titles "pH" "Zn + Cu + Cd + Pb + Co + Ni (ppb)"
   -axis_scale x_axis 0.0 14 1 0.5
   
        -axis_scale y_axis log 0.0 10000 10 1
   -start
10 PLOT_XY -la("H+"),(("sum_metals")), color = Red, line_w = 0, \ symbol = Circle, symbol_size = 10
   -end

[dlparkhurst]

Here is a simple 1:1 log plot example.

SOLUTION
REACTION
NaCl 1
0.001 0.01 0.1 1
USER_GRAPH 1
    -headings               RXN Na
    -axis_titles            "Moles of reaction" "Concentration of Na" ""
    -axis_scale x_axis      auto auto auto auto log
    -axis_scale y_axis      auto auto auto auto log
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 PLOT_XY RXN, TOT("Na")
  -end
    -active                 true