Document Type

Technical Report

Publication Date

4-1-1980

Keywords

Chemicals, soil, ground water contamination, soil water velocity

Abstract

Dispersion of 3HOH was studied at flow velocities less than 14 cm/day in a Captina silt loam using the half-cell technique. Two directions of transport were studied: movement of 3HOH in the same direction as water, and movement of 3HOH in the opposite direction to that of water. Results indicated that the dispersion coefficients were velocity dependent for equilibration times ranging to 21 hours. As the average pore flow velocity increased, the length of time needed for the dispersion coefficients to become independent of the flow velocity increased. When considering transport of 3HOH in the same direction as water, the dispersion coefficients 1) increased as flow velocity increased, 2) decreased as the initial soil water content decreased, and 3) could be described by a linear regression model. The magnitude of the dispersion coefficients ranged from 0.84 to 7.50 x 10-5 cm2 /sec. When considering transport of 3HOH in the opposite direction as water, the dispersion coefficients increased as the flow velocity increased and could be described by a linear regression model. The magnitude of the dispersion coefficients ranged from 0.29 to 5.88 x 10-5 cm2 /sec and were less sensitive to the soil water flow parameters than those of flow in the same direction. In both flow regimes diffusion was the predominant transport mechanism at the lower flow velocities whereas hydrodynamic dispersion predominated at the higher flow velocities.

Report Number

PUB066

Page

71

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