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Lado, M., Faculty of Sciences, Univ. da Coruña, A Zapateira s/n 15071, Spain
Ben-Hur, M., Inst. of Soil, Water and Environ. Science, Volcani Centre, Agricultural Research Organization, P.O. Box 6, Bet Dagan 50250, Israel
Shainberg, I., Inst. of Soil, Water and Environ. Science, Volcani Centre, Agricultural Research Organization, P.O. Box 6, Bet Dagan 50250, Israel
Formation of a depositional seal is common in soils subjected to rainfall or sprinkler or surface irrigation; however, studies on its hydraulic properties are scarce. In this study, the effects of clay mineralogy, exchangeable sodium percentage (ESP), electrolyte concentration, and pH on the hydraulic properties of depositional seals were investigated. A silt loam packed in columns was leached with 5 g L-1 suspensions of reference montmorillonite, illite, and kaolinite with various ESPs (0-100), electrolyte concentrations (<2-20 mmol L-1), and pH (7-11). Deposition of the clay particles on the soil surface formed seals, and their hydraulic resistance (Rc) which is the ratio between the thickness of the seal and its hydraulic conductivity, was measured. The Rc values of the seals developed by all clays with ESP 0 was low (<10.1 h). Conversely, at ESPs ≥10 and electrolyte concentrations ≤20 mmol L-1, the Rc values of illitic seals ranged from 0.3 to 9.5 h and that of montmorillonitic seals ranged from 0.6 to 443.7 h. In both clays, increasing the ESP of the clay increased the seal Rc. A decrease of the electrolyte concentration increased the Rc of the montmorillonitic seals but had no effect on the Rc of the illitic seal. The Rc of Ca- and Na-kaolinitic seals was low at pH <9.0. Increasing the pH to 11 increased the Rc of the Na-kaolinite seal due to greater clay edge negative charge and associated dispersion. Conversely, in the Ca-kaolinite seal, the increase in pH decreased Rc due to CaCO3 precipitation and clay cementation. © Soil Science Society of America.
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Clay mineralogy, ionic composition, and pH effects on hydraulic properties of depositional seals
71
Lado, M., Faculty of Sciences, Univ. da Coruña, A Zapateira s/n 15071, Spain
Ben-Hur, M., Inst. of Soil, Water and Environ. Science, Volcani Centre, Agricultural Research Organization, P.O. Box 6, Bet Dagan 50250, Israel
Shainberg, I., Inst. of Soil, Water and Environ. Science, Volcani Centre, Agricultural Research Organization, P.O. Box 6, Bet Dagan 50250, Israel
Clay mineralogy, ionic composition, and pH effects on hydraulic properties of depositional seals
Formation of a depositional seal is common in soils subjected to rainfall or sprinkler or surface irrigation; however, studies on its hydraulic properties are scarce. In this study, the effects of clay mineralogy, exchangeable sodium percentage (ESP), electrolyte concentration, and pH on the hydraulic properties of depositional seals were investigated. A silt loam packed in columns was leached with 5 g L-1 suspensions of reference montmorillonite, illite, and kaolinite with various ESPs (0-100), electrolyte concentrations (<2-20 mmol L-1), and pH (7-11). Deposition of the clay particles on the soil surface formed seals, and their hydraulic resistance (Rc) which is the ratio between the thickness of the seal and its hydraulic conductivity, was measured. The Rc values of the seals developed by all clays with ESP 0 was low (<10.1 h). Conversely, at ESPs ≥10 and electrolyte concentrations ≤20 mmol L-1, the Rc values of illitic seals ranged from 0.3 to 9.5 h and that of montmorillonitic seals ranged from 0.6 to 443.7 h. In both clays, increasing the ESP of the clay increased the seal Rc. A decrease of the electrolyte concentration increased the Rc of the montmorillonitic seals but had no effect on the Rc of the illitic seal. The Rc of Ca- and Na-kaolinitic seals was low at pH <9.0. Increasing the pH to 11 increased the Rc of the Na-kaolinite seal due to greater clay edge negative charge and associated dispersion. Conversely, in the Ca-kaolinite seal, the increase in pH decreased Rc due to CaCO3 precipitation and clay cementation. © Soil Science Society of America.
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