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Clay Mineralogy, Ionic Composition, and pH Effects on Hydraulic Properties of Depositional Seals
Author(s) -
Lado M.,
Ben-Hur M.,
Shainberg I.
Publication year - 2007
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2006.0169
Subject(s) - kaolinite , illite , loam , montmorillonite , geology , sedimentary depositional environment , hydraulic conductivity , electrolyte , mineralogy , clay minerals , silt , soil water , chemistry , soil science , geomorphology , electrode , structural basin , organic chemistry
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 ( R c ), which is the ratio between the thickness of the seal and its hydraulic conductivity, was measured. The R c 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 , th e R c 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 R c A decrease of the electrolyte concentration increased the R c of the montmorillonitic seals but had no effect on the R c of the illitic seal. The R c of Ca‐ and Na‐kaolinitic seals was low at pH <9.0. Increasing the pH to 11 increased the R c 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 R c due to CaCO 3 precipitation and clay cementation.