Transient and Steady‐State Solute Transport Through a Large Unsaturated Soil Column

Abstract

The use of steady‐state models can sometimes reduce the computational resources and input data required for solution of transient transport problems. A large column experiment was performed to test whether solute transport parameters determined from a steady flow experiment may be used in transient, unsaturated flow and transport model predictions. Tritiated water and bromide were applied at a steady rate to the top of a 0.95 m diameter by 6 m deep soil column containing unsaturated soil. After 10 days, tracers were eliminated from the irrigation water. When the soil moisture content within the column ceased to change, another 10‐day pulse of tritiated water and bromide was applied, followed by water without tracers. Transport model parameters were determined through optimization, using breakthrough curves observed at various depths. The tritiated water and bromide pulses lagged behind the wetting front during infiltration into the relatively dry soil. The bromide pulse moved 17–20% faster than the tritiated water pulse, because of anion exclusion. Breakthrough curves for the transient and steady‐state experiments were similar. Because the solute fronts lagged significantly behind the moisture fronts, steady‐state transport parameters, when used in a fully transient numerical model, fairly described the transport under transient conditions.

Water quality and surfactant effects on the water repellency of a sandy soil

“…1. As water leaches a solute through a soil profile, the solute's peak typically becomes less distinct with the peak's shoulders broadening as the solute moves downward (Porro and Wierenga, 1993). This broadening of the WDPT peaks for both the WW and RW irrigations can be seen by comparing Fig.…”

Spatial variability of bromide and atrazine transport parameters for a Udipsamment

“…The parameters of the convection-dispersion equation (CDE; Porro and Wierenga, 1993) were estimated. The CDE equation with terms for solute adsorption and degradation is as follows:…”

“…Studies have been conducted to evaluate the transport of solutes in soil (Biggar and Nielsen, 1976;Jury et al, 1982;Rao and Jessup, 1983;Sposito et al, 1986;Porro and Wierenga, 1993;Ellsworth and Boast, 1996;Jacques et al, 1999;ToiberYasur et al, 1999;Strock et al, 2001). Some of these studies have evaluated the effects of climate along with soil and chemical properties on the movement of specific solutes.…”

Estimation of Groundwater Recharge Using Tracers and Numerical Modeling in the North China Plain

“…The main reason might be that the transfer behavior of bromide rather than tritium in soil was effected by the soil charge, i.e., when the total charge is positive with more cations, the soil would absorb anions [40,41], e.g., bromide ions, resulting in a smaller recharge rate, such as in the LC01, LC02 and LC08. Additionally, when the total charge is negative with more anions, the effect of ion exclusion would happen [16,42], resulting in a larger recharge rate, such as in LC03, LC04, HS01, HS02 and HS03. However, the differences of the annual groundwater recharge between the results of the bromide and tritium by the multi-region method were 14.3% and 2.9% in the LC and HS sites, respectively, which could be explained by the higher recharge rate for the LC site of 124.3 mm/year, leading to a larger difference of transfer for two tracers.…”