Input (pre-processing) › Solute transport

Solute transport: reactions

The reaction parameters per solute and material, the second part of the Solute Transport Parameters dialog of HYDRUS-1D (Solute Reaction Parameters). The equations are in solute transport.

Parameters

Parameter	HYDRUS	Description
Ks	Kd	adsorption coefficient [L³/M] of the isotherm s = Ks c^β/(1 + η c^β); for linear sorption the distribution coefficient Kd
η	Nu	Langmuir coefficient [L³/M]; 0 = Freundlich or linear
β	Beta	Freundlich exponent [–]; 1 = linear
Henry kH	Henry	Henry's constant, g = kH c [–] (volatile solutes) Jury et al. (1983)
μw, μs, μg	SinkL1, SinkS1, SinkG1	first-order decay constants in the liquid, solid and gas phases [1/T]
γw, γs, γg	SinkL1', SinkS1', SinkG1'	first-order production of this solute from the previous one (decay chain) [1/T]
μ0w, μ0s, μ0g	SinkL0, SinkS0, SinkG0	zero-order production in the three phases [M/L³/T, 1/T] (negative values: zero-order decay)
α (rate)	Alfa	first-order rate of the non-equilibrium exchange: kinetic sorption sites (f < 1) or mobile–immobile water (θim > 0) [1/T]
αs	–	dual permeability: solute transfer coefficient between the fractures and the matrix [1/T]

With dual non-equilibrium the columns μg and γg are reused: μg is the fraction f_em of equilibrium sites in the mobile zone and γg the rate ω_S of the kinetic sites, as in HYDRUS-1D. With the colloid model the columns are reused for the attachment parameters (colloids).

Hints

For a conservative tracer leave all reaction parameters at 0 (Ks = 0, β = 1).
The retardation factor of linear sorption is R = 1 + ρ Kd / θ.
The half-life of first-order decay is t_1/2 = ln 2 / μ.

Literature cited in this topic

Jury, W. A., W. F. Spencer, and W. J. Farmer (1983). Behavior assessment model for trace organics in soil: I. Model description. Journal of Environmental Quality 12(4): 558–564. doi:10.2134/jeq1983.00472425001200040025x

All sources: References.