First parentheses give units. (-) means dimensionless.

Last parentheses give number of equation or Figure where symbol first appears or is defined. in the above reference

c ............. electrolyte concentration
(mol per Liter of liquid), (18),
**c** ..............vector of
soluble concentration {M, H_{t}} or {M, H}, (mol per Liter of liquid),
(31),
**C** ..............vector of
adsorbed concentrations __H__(M, H) and __M__(M, H), (mol per Liter
of system volume),

F ..............Faraday constant
(96485 Coulomb per mol), (10),

H_{+} ............H(x *
0, t = 0), (5),

H_{-} .............H(x <
0, t = 0), (5),

H_{t-} ............H_{t}(x
< 0, t = 0), (27), see also (9),

H_{m} ............concentration
of free proton between 1- and 2-wave, (mol per Liter of liquid), (Figure
1),

H_{t}(x, t) ......total
soluble concentration of protons, (mol per Liter of liquid), (2),

H(x) ..........concentration of
free proton, (mol per Liter of liquid), (8),

H(x, t) .......concentration of
free proton at location x and time t, (mol per Liter of liquid), (9),
__H__(M, H) ......adsorbed proton
concentration (proton isotherm), (mol per Liter of system volume), (2),

I ................ionic strength,
(mol per Liter of liquid), (21),
__I__ ................identity
matrix, (32),

k ................index specifying
wave, k = 1: 1-wave (slow), k = 2: 2-wave (fast), (Figure1, (25), (26)),

k_{1} ..............equilibrium
formation constant of XOH_{2} surface complex from XOH and H, (Liter
per mol), (13),

k_{2} ..............equilibrium
formation constant of XO surface complex from XOH and H, (mol per Liter),
(15),

K_{w} ..............water
dissociation constant, ((mol per Liter of liquid)2), (9),
__Kd__(**c**) .........Jacobi
matrix of isotherms evaluated at location c in composition space, (-),
(32),

M_{+} .............M(x <=
0, t = 0), (mol per Liter of liquid), (5),

M_{-} ..............M(x
< 0, t = 0), (mol per Liter of liquid), (5),
__M__(M, H) ......adsorbed metal
concentration (metal isotherm), (mol per Liter of system volume), (1),

M(x, t) ........soluble metal concentration,
(mol per Liter of liquid), (1),

M(x) ...........soluble concentration
of metal, (mol per Liter of liquid), (7),

M_{m} .............concentration
of metal between the 1- and 2-wave, (mol per Liter of liquid), (Figure
1),

M^{a}_{eq}(H) .....soluble
equivalent metal concentration (at which half the adsorption sites of type
a are filled with metal ions) as a function of H, (mol per Liter of liquid),
(36),

P(x) ...........Boltzmann distribution
as a function of distance from oxide surface, (-), (10),

P(H) ..........analytical approximation
of Boltzmann distribution at oxide surface as a function proton concentration,
(-), (22), (23),

P_{0}(XO.., c)..Boltzmann
distribution at oxide surface as a function of non neutral surface complex
concentrations and electrolyte concentration, (-), (18),

PZC ...........point of zero charge
on hydrous ferric oxide in pristine water, i.e. at I < 10^{-4}
mol/L PZC = (k_{2}/k_{1})^{1/2}, (22),

q ...............flux of water in
column of porous medium, (meter per year), (1),

R ...............molar gas constant,
(8.314 Joule per(mol Kelvin)), (10),
__R__(**c**) ...........retardation
matrix evaluated at location c in concentration space, (-), (31),

r_{k}(**c**) ..........right
eigenvector of __R__(**c**) corresponding to eigenvalue rho_{k}(**c**),
((mol year) per (Liter meter)), (IV.13),

t ................time variable,
(year), (1),

T ...............absolute temperature,
(Kelvin), (10),

X_{aT} ............concentration
of adsorption sites of type a, (mol per Liter of system volume), (11),

X_{T} ..............concentration
of adsorption sites of any type, (mol per Liter of system volume), (12),

X_{a}O ...........concentration
of empty sites of type a, (mol per Liter of system), (11),

X_{a}OL .........concentration
of sites of type a covered with L = H, H_{2}, M, (mol per Liter
of system), (11),

XOL ...........concentration of
any site type covered with L = H, H_{2}, M, (mol per Liter of system),
(12),

x ...............space variable
(meter), (1),

z ...............charge of ion,
(multiple of unit electronic charge), (10).

a ...............site
type, (a
= s, w), (11),

a_{a} ..............metal-proton
exchange constant for site type a,
(-), (39),

d_{a} ...............denominator
in adsorption isotherms (17), (mol per Liter of liquid),

Dc ...............concentration
jump across shock, (mol per Liter of liquid), (3)

Dt ................time
interval, (year), (3),

Dx ...............distance
traveled by shock during period Dt,
(meter), (3),

f .................porosity
of medium, (-), (1),

r(**c**) .............eigenvalue
of __R__(**c**), also called "retardation", (-), (IV.3),

r_{k}(**c**)
...........retardation of k-rarefaction wave, (-), (33),

s_{k} ...............retardation
of k-shock, (-), (V.2),

x(**c**) ............speed
of concentration **c**, (meter per year), (6),

x_{k} ...............speed
of concentration in a k-wave, (meter per year), (28),

y(x) .............electrostatic
potential at distance x from oxide surface, (Volt), (10).