Molecular diffusion coefficients

Calculation of molecular and ionic diffusion coefficients in sea water or in pore water of a sediment column. Various investigators have developed models (formulas) to predict diffusion coefficients when the solute in question is present in small vanishingly concentrations. While one might first presume that such formulas are of limited value in moderately strong electrolyte solutions such as marine waters - instuition fails in this case. In fact, infinite dilution coefficients play an integral role in the theories for stronger solutions, and they are reasonably accurate approximations for all but the major ions. (Boudreau, 1997)

Enter:
Parameter Unit Range User-input
Temperature C 0-40
Salinity PSU (ppt) 0.5-43
Pressure atm (1 atm at surface) 0-1200

Diffusion coefficients are in C. CANDI units [cm2 a-1] and in SI-Units [m2 s-1]:

Parameter Result [cm2 a-1] SI-Result [m2 s-1]
H2O
O2
CO2
NH3
H2S
H3PO4
B(OH)3
HCO3-
CO32-
NH4+
HS-
NO3-
H2PO4-
HPO42-
PO43-
B(OH)4-
H+
OH-
Ca2+
Mg2+
Fe2+
Mn2+
SO42-
H4SiO4
CH4
Na+
Cl-

Boudreau, B., 1997, Diagenetic Models and thier implementation, Springer, Berlin.

© Copyright R. Luff (DG2HL) 1997-2000.

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