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Biogenic organic matter (BOM) is of ubiquitous relevance in all aquatic systems. This is due to the fundamental function of the natural organic matter in combination with the microbial activity which guarantees the degradation in and the self purification of water in the hydrological cycle. In addition, the refractory part of the widely distributed BOM acts as effective adsorbent for most water constituents, and in case of mobile fractions as active vehicle for pollutants. In contrast to the broad importance of the occurrence and role of BOM, there is a fairly small variety for its analytical characterization. Especially in the field of in-situ measurements and of the determination in the original concentration range of aqueous samples, relatively little data have been collected. This is partly due to the complex structure of BOM, partly to the limited availability of analytical methods suited for that type of investigations. The aim of the paper is to give typical examples for the a) physical/chemical, b) microbiological and c) technologically orientated methods of the analytical characterization of BOM in aqueous solution and to draw conclusions on the function of BOM in aquatic systems and their use for man.

Summary: A method is described for the specific hydrolysis of amino acids from humic substances by using the proteolytic enzyme "Pronase E". The amino acids are analyzed by a fluorescence detector after precolumn derivatization and HPLC-separation. The pattern and the concentration of amino acids after the enzymatic hydrolysis are set up for humic substances of different origin. Due to the results the enzymatic hydrolysis is suitable for the characterization of humic substances with a nitrogen content higher than 3%. As shown in a kinetic study of the hydrolysis of a fulvic acid the influence of humic substances on the enzyme activity increases in case of lower nitrogen content. Due to the specificity of the proteolytic enzyme the operationally defined method is limited as shown by a protein of a known amino acid content. The amino acids leucine, valine, tyrosine and histidine are released to the highest extent. The determined total extent for the hydrolysis of Insulin B is 26.34% and for Casein 38.37%. By comparison of the enzymatic hydrolysis with the classic acid hydrolysis the advantages of the biochemical method are the simple experimental handling and the mild reaction conditions. Amino acids which are very unstable like glutamine and asparagine can only be analyzed by the enzymatic hydrolysis.

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