Anion Exclusion-Pore Water Velocity Interaction Affecting Transport of Bromine through an Oxisol
- R. Melamed,
- J. J. Jurinak and
- L. M. Dudley
The transport of anions through soils is affected by both chemical and physical processes. We investigated how adsorbed phosphate affected the mobility of Br, at different pore water velocities (PWV), through saturated Oxisol soil columns. The PWVs were 2.9, 8.7, and 48.1 cm h−1. The addition of 16.2, 32.4, and 48.6 mmol P kg−1 phosphate reduced the pH of the point of zero charge from 6.0 (control) to 5.1, 4.6, and 4.3, respectively, as measured by potentiometic titration. The negative surface charge of the soil increased by 0.7 mmolc mmol−1 P added. The mobility of Br increased with P treatment because of Br exclusion induced by the P generated negative surface charge. At the highest P treatment, the exclusion volume of Br was 21% of the saturated water content. With increasing PWV, the P-induced surface charge had a decreasing effect on Br mobility, whereas the influence of solute dispersion increased.
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