RECENT ADVANCES IN THE SPECTROSCOPIC CHARACTERIZATION OF SOIL HUMIC SUBSTANCES AND THEIR ECOLOGICAL RELEVANCE

Non destructive spectroscopic methods such as C-13- and N-15-NMR provi de new insights into the structure of humic substances. Solid state NM R is capable of studying complete native soils by the CPMAS-technique. By means of nitrogen 15-enriched composts it is suggested that nitrog en in soil organic matter is mainly located in amide and peptide struc tures. Most probable assignments are given. The investigation of humif ication processes in forest soils is possible via an approach which us es several fractionation techniques in combination with degradative an d non-degradative analytical techniques. Besides structure analysis, t he C-13-NMR-spectroscopy provides important information about the func tions of humic substances. By using C-13-enriched xenobiotics the bind ing mechanism to organic matter can be elucidated on a molecular basis . Molecular fluorescence spectrometry, a non-invasive method, is a pow erful tool for the quantitative characterization of metal ion complexa tion by dissolved organic matter in aqueous leaf litter extracts in te rms of conditional stability constants and metal binding capacities.