CHARACTERIZATION OF CLAY-ORGANIC-MATTER COMPLEXES RESISTANT TO OXIDATION BY PEROXIDE

In an acid soil, amounts or organic carbon resistant to peroxidation w ith hydrogen peroxide were strongly related to the proportions of expa ndable phyllosilicate (vermiculite, smectite) in the clay fraction, as measured by its K2O content and cation exchange capacity. This was ta ken to indicate that a substantial part of the organic matter resistan t to oxidation was interlayered. The organic compounds in the clay-org anic matter complexes were identified by Pyrolysis Field Ionization Ma ss Spectrometry (Py-FIMS). Alkyl-aromatics as well as carbohydrates, p henols, lignins, lipids and N-compounds were found in the C-horizon sa mple, whereas mainly alkyl-aromatics and N-compounds, more resistant t o chemical oxidation, were associated with the Al and Bw fine-clay fra ction. This was interpreted as being due either to the evolution of th e clay-associated compounds paralleling the mineralogical transformati ons, or to the selective adsorption of the more stable components.