Epsilon Archive for Student Projects

Abstract

In an ongoing study it was found that ammonium oxalate treatment in the dark (NH4Ox-D) reduced the permanent charges considerably in the Bh horizon and to a lesser degree in the Bs1 and Bs2 horizon in a podzolised soil. The aim of this study was to evaluate if the loss of permanent charge can be explained by removal of partial hydroxy-Al interlayer material by the NH4Ox-D treatment, resulting in a collapse of the interlayer space. The clay fraction from NH4Ox-D treated and untreated samples from the three horizons were separated. The samples were K-saturated, parallel oriented and analysed by X-ray diffraction at 25ºC, 300ºC and 500ºC.

The broad and less intense peaks at ~13 Å, at 25ºC, in both of the samples from the Bh ho-rizon indicated that the minerals were partially interlayered. Comparison between the NH4Ox-D treated sample and the untreated sample, at 25ºC, showed a more pronounced peak at 10 Å after NH4Ox-D treatment indicating a lower degree of interlayer filling. Both of the samples completely collapsed to 10 Å after heating to 300ºC. The low resistance to heating showed that the interlayer material was less stable and that may also be a result of partial interlayering in the mineral. The lower degree of interlayer filling in the minerals in the NH4Ox-D treated sample may be a result of the treatment but the effect was not large enough to explain the large loss of permanent charges in the horizon.

The higher degree of interlayer material in the mineral in the Bs1 and Bs2 horizons were re-sistant against the NH4Ox-D treatment showed by the 14 Å peak at 25ºC that did not shift to 10 Å after heating to 300ºC and 500ºC.