TITLE Langmuir isotherm (from GWB) SURFACE_MASTER_SPECIES
        L        L
SURFACE_SPECIES
        L = L
          log_k    0.0
        L + Ca+2 = LCa+2
          log_k    2.1
SURFACE 1
        -equilibrate with solution 1
        -no_edl
        L   0.01
SOLUTION 1
        -units mg/kgw
        ph        8.3
        Ca        10000
        Mg        1300
        Na        10700
        Sr        10
        K         400
        S(6)      2700
        Cl        19000        charge
END