The effect of organic matter and iron oxides as solid components of the red
earth on the retention of SeO3 has been investigated by a batch technique
and selective extraction method. The sorption and desorption isotherms of S
eO3 on the untreated red earth and the three treated soils were determined
at 20 degrees C, pH 6.8 or 7.2 and in the presence of 0.01 M CaCl2. It was
found that the sorption-desorption hysteresis for untreated and treated soi
ls is obvious and the clays play an important role in the sorption-desorpti
on hysteresis, and that the retention of SeO3 on red earth is attributed to
the iron oxides to a great extent.