Rusteau-1D HelpSolute transport: temperature and water-content dependence, colloids
The page appears when the temperature dependence, the water-content dependence of reactions or the colloid model is switched on (page Solute transport: general). It corresponds to the dialogs Temperature Dependence of Reaction Parameters, Water Content Dependence of Reaction Parameters and the attachment parameters of the Virus, Colloid, Bacteria Transport Model of HYDRUS-1D.
Activation energies
Per solute, the activation energy Ea [J/mol] of every transport and reaction parameter (Dw, Dg, Ks, η, β, Henry, μ, γ, μ0, ω). A parameter a at temperature T is a(T) = a(Tref) exp[Ea (T − Tref) / (R T Tref)] with the reference temperature 20 °C Stumm and Morgan (1981); 0 = no temperature dependence. Typical activation energies of degradation are 40–80 kJ/mol (theory).
Water-content dependence
Walker's formula Walker (1974): rate = rateref (θ/θref)B for θ < θref, with the exponent B (≈ 0.7) and the reference pressure head href whose water content is θref, for each of the nine rate coefficients.
Trapezoidal tables (MoistDep.in): per material, solute and reaction, the rate factor is ReacMin0 below θ0, rises linearly to 1 at θ1, stays 1 up to θ2 and falls to ReacMin1 at θ3 (θ2 = 0: no reduction). HYDRUS-1D writes but does not use MoistDep.in; Rusteau uses it (theory).
Colloid attachment parameters
| Parameter | Description |
|---|---|
| rKa1, rKa2 | attachment coefficients of the two sites [1/T], or sticking efficiencies with filtration theory |
| rKd1, rKd2 | detachment coefficients [1/T] |
| SMax1, SMax2 | maximum solid-phase concentrations (blocking) |
| iPsi1, iPsi2 | blocking function: 0 none, 1 Langmuir, 2 ripening, 3 random sequential adsorption, 4 straining, 5 straining and blocking |
| Dc, Dp | diameters of the sand grains and the colloids (filtration theory, straining) [L] |
| ω immobile (matrix) | dual permeability: exchange of colloids with the immobile matrix water [1/T] |
See colloid, virus and bacteria transport.
Literature cited in this topic
- Stumm, W., and J. J. Morgan (1981). Aquatic Chemistry. 2nd ed., John Wiley & Sons, New York, 780 pp.
- Walker, A. (1974). A simulation model for prediction of herbicide persistence. Journal of Environmental Quality 3(4): 396–401. doi:10.2134/jeq1974.00472425000300040021x
All sources: References.