Effect of wetting and drying and dilution on moisture migration through oil contaminated hydrophobic soils.

Hydrophobic soils display resistance to wetting and frequently do not hold water to support good plant growth. A laboratory investigation was conducted to study moisture movement through hydrophobic soils. Test results indicated that hydrophobic soils have a critical moisture content beyond which they behave as wettable or hydrophilic soils. Soil hydrophobicity decreased and water infiltration increased when the soil was subjected to an increasing number of wetting and drying cycles. The effect of diluting hydrophobic soil with hydrophilic soil on water infiltration was also studied. The results indicated that water infiltration into soil becomes more rapid and uniform as the mass fraction of hydrophilic soil is increased in the mix. Water infiltration was observed even in hydrophobic-hydrophilic soil mixtures classified as severely water-repellent by commonly used arbitrary ordinal scales.