STUDY OF THE BIODEGRADATION AND HUMIFICAT ION OF SOIL ORGANIC-MATTER OF PLANT-ORIGIN BY ELECTRON-ENERGY-LOSS SPECTROSCOPY (EELS) - DISTRIBUTION OF CARBON, NITROGEN AND C N EVALUATION AT ULTRASTRUCTURAL LEVEL IN-SITU/

Electron Energy Loss Spectrometry is used to analyse carbon and nitrog en for the study of biodegradation of soil organic matter. With the bi oorganic samples embedded in an organic resin, a low energy loss study showed that the analysed organites are homogeneously impregnated by t he resin, allowing us to quantify the evolution of the carbon/nitrogen (UN) ratio as a function of the degradation state of the bioorganic m atter (brown pigments of beech leaves that appeared at the senescence stage, biodegraded or not by a white rot fungus). The difference betwe en the UN ratios can be considered as a result of humification. Such a nalyses answer specifically to a characterization of light elements in situ at an ultrastructural scale and are very promising for the study of soil organic matter transformation.