Changes across Artificial E–Bh Boundaries Formed under Simulated Fluctuating Water Tables

Spodosols in the coastal plain of the southeastern USA are mainly restricted to zones of fluctuating water table, but mechanisms of water table linkage are not well established. A previous study showed that Aquod-like E and Bh horizons could be artificially formed only under simulated fluctuating water table conditions. The present study was conducted to characterize the redistribution of components during artificial podzolization and to compare the resultant distributions with those of an Aquod adjacent to the Psamment from which column materials were collected. A hypothesis tested is that the E–Bh formation involves colloidal as well as chemical translocation. Artificial E–Bh horizons were generated in three acrylic columns using an approximate cycle of 22 h of saturation and 2 h of free drainage. Distilled water was introduced from the bottom of columns, and oxalic acid from the top. Boundaries migrated downward at a progressively slower rate, and became increasingly abrupt and irregular with time. E horizons consisted mainly of stripped sand grains; coatings were retained in Bh horizons. Fine materials containing C and Al accumulated in the upper centimeters of the Bh, as documented by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). Bulk analyses verified accumulations of C in the Bh and a movement of Al and crystalline clay from E to Bh. Artificial E–Bh formation entailed redistribution of sand grain coatings initially present on sands used in columns. Crystalline as well as noncrystalline clay accumulated in the Bh horizon, supporting the idea that E–Bh formation involved colloidal as well as chemical migration. A weatherable-mineral source of Al is not required for the artificial water table–induced formation of E–Bh sequences. Noncrystalline Al, dissolved in the grain-stripping process, is a likely source of Al in Bh horizons of the region. Distributional trends in artificial E–Bh sequences paralleled those of the natural Aquod.