Thursday, 13 July 2006
57-8

Effect of Clay Minerals and Calcite on Water Repellency of Sandy Soils.

Ivan Simkovic, Pavel Dlapa, Lucia Korenkova, and Michal Duris. Dept of Soil Science, Faculty of Natural Sciences, Comenius Univ, Mlynska Dolina B-2, Bratislava, 842 15, Slovak Republic

The effects of adding 1% and 15% (weight) calcite, as well as 1% and 3% of clay minerals on the wettability of water-repellent sandy soils sampled in aeolian sand region of the western Slovakia were studied both with and without the wetting and drying cycle before the heating phase. The clay minerals were standards from the Source Clay Minerals Repository (University of Missouri, Columbia, USA). The persistence of water repellency was estimated with the water drop penetration time (WDPT) test. After wetting, water repellency disappeared in all the samples. During the drying phase, water repellency re-appeared in all samples (untreated and calcite-treated) as the water content decreased below 1%. Repellency did, however, not reach pre-wetting levels. The effect of calcite addition on water repellency depended on the amount of calcite addition. An addition of 1% and 15% calcite resulted in decrease in WDPT in the treatment without the wetting and drying cycle before the heating at 50°C. The effect of clay contents on water repellency differed strongly among the four clay minerals. Kaolinite and Na-montmorillonite reduced WDPT significantly, while Ca-montmorillonite and illite were less effective or caused even increase in WDPT. The heating at 50°C was used to simulate the effects of hot dry spells on water repellency.

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