TITLE Example 13A.--1 mmol/l NaCl/NO3 enters column with stagnant zones.
                    Implicit definition of first-order exchange model.
SOLUTION 0    # 1 mmol/l NaCl
        units   mmol/l
        pH       7.0
        pe      13.0    O2(g)   -0.7
        Na       1.0    # Na has Retardation = 2
        Cl       1.0    # Cl has Retardation = 1, stagnant exchange
        N(5)     1.0    # NO3 is conservative
#       charge imbalance is no problem ...
END
SOLUTION 1-41  # Column with KNO3
        units   mmol/l
        pH       7.0
        pe      13.0   O2(g)    -0.7
        K        1.0
        N(5)     1.0
EXCHANGE 1-41
        -equil  1
        X       1.e-3
EXCHANGE_SPECIES # For linear exchange, make KX exch. coeff. equal to NaX
        K+ + X- = KX
        log_k   0.0
        -gamma  3.5     0.015
END
TRANSPORT
        -cells  20
        -shifts 5
        -flow_d   forward
        -timest 3600
        -bcon   flux  flux
        -diffc  0.0
        -length 0.1
        -disp   0.015
        -stag       1  6.8e-6  0.3        0.1
#   1 stagnant layer^, ^alpha, ^theta(m), ^theta(im) 
PRINT
        -reset false
	-echo true
END
SOLUTION 0  # Original solution reenters
        units   mmol/l
        pH       7.0
        pe      13.0   O2(g)    -0.7
        K        1.0
        N(5)     1.0
TRANSPORT
        -shifts 10
        -punch_frequency    10
        -punch_cells        1-20
SELECTED_OUTPUT
        -file   ex13a.sel
        -reset  false
        -solution
        -distance       true
USER_PUNCH
        -head Cl_mmol Na_mmol
10 PUNCH TOT("Cl")*1000, TOT("Na")*1000
END