Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/14/2002
Publication Date: 11/14/2002
Citation: PILS, J.R., EVANGELOU, V.P., LAIRD, D.A. SMECTITE TACTOID FORMATION INDUCED BY CONFINED AND DOUBLE LAYER MONOVALENT CATIONS. AGRONOMY ABSTRACTS. 2002. CD-ROM. MADISON, WI.
Technical Abstract: Soil colloid dispersion is an important phenomenon that influences soil erosion, toxin and nutrient transport, crusting of surface soils, and siltation in rivers and lakes. The mechanisms governing colloidal dispersion behavior are associated with both interlayer expansion (crystalline swelling) and double-layer swelling of expanded clays. The classical DLVO theory predicts that high ionic strength compresses the electric double layer associated with colloidal surfaces inducing flocculation. With increasing monovalent cation concentration ratios, the DLVO predicts an increase in osmotic pressure in the electric double layer, hence soil colloid dispersion. However, DLVO theory does not predict the formation and destruction of quasicrystals. With increasing CRx, the 1.4 nm XRD peaks both broaden and decrease in intensity, suggesting that Ca-quasicrystals are becoming smaller. At high CRx, broad and low-intensity 1.2 nm XRD peaks start to appear, suggesting the formation of potassium or ammonium quasicrystals. Results of the study indicate that soil colloid dispersion is influenced by both DLVO phenomena and quasicrystal formation and destruction.