Soil substrates of sewage farms (inflow of sewage areas) and of closed sewage farms were investigated by means of thermogravimetry and differential thermal analysis. The results were compared with those obtained for control samples from outside the sewage farms.The organic matter of actively used sewage areas (inflow) contains a remarkable amount of easily oxidizable eompounds brought to the inflows by suspended matter.Beside these compounds, macromolecular organic substances predominate in the composition of the organic matter and are responsible for an immense heat release in the high temperature range of the thermal studies.In the substrates of closed sewage farm inflows or of other sewage farm areas which do not belong'to the inflows, the amounts of volatile and easily oxidizable compounds decrease rapidly. The substrates hardly differ in their reaction temperatures from control samples. The influence of single macromoleeules on the exothermic oxidation is reduced with increasing humification.
In the chemolysis products of extracted humic acids (HAs) and tetramethylammonium hydroxide, different compounds can be identified which allow a description of the sources of soil organic matter (SOM). It is possible to draw conclusions concerning stability, degree of intramolecular cross-linking and degradation of aliphatic and lignin components from the distinctive product ratios. The ratio of lignin derived acidic phenolic derivatives and their analogous aldehydes and the ratio of phenylpropenoic acids and analogous benzoic acids provide comparably good parameters for the characterization of the state of degradation of lignin compounds to relatively stable HA building blocks. Regarding the aliphatic chemolysis products, alpha,omega-dicarboxylic acid and methoxy fatty acid contents indicate an intramolecular cross-linking state within the HA molecules and the degree of stable aliphatic constituent parts. High contents of unsaturated fatty acids can be considered as an indicator of an easy degradable humic skeleton because with their double bonds they represent active sites for further transformations. The suitability of the carbon preference index as an indicator of a biogenic carbon source can be confirmed. It is remarkable how the results obtained from extracted humic acids are in accordance with the expectations for the different SOMs derived from land use.
Mit Hilfe von FTIR-Spektroskopie und Elementaranalyse werden die organischen Bodensubstanzen von Rieselfeldböden und unberieselten Standorten verglichen.Die organische Bodensubstanz (OBS) von Rieselfeldsubstraten besitzt deutlich kleinere C/N-Verhältnisse als die OBS der Vergleichsstandorte. Die IR-Spektren der Rieselfeld-OBS zeigen, daß ein erheblicher Teil des größeren Stickstoffgehalts in Amidbindungen lokalisiert ist.Mittels fraktionierter Extraktion werden die mobilen und leichtoxydierbaren Anteile der Rieselfeld-OBS isoliert. Die IR-Spektren identifizieren die leichtverfügbaren Spezies als Substanzen mit Keton-bzw. Esterund Saccharidstrukturen und in geringem Umfang auch als Substanzen mit Peptidbindungen.STICHWÖRTER: FTIR-Spektren, Organische Bodensubstanz, Rieselfeldboden
FTIR-SPECTROSCOPIC INVESTIGATIONS ON ORGANIC MATTER OF SEWAGE FARM SUBSTRATESOrganic matters of sewage farm soils and control soils are compared by means of FTIR-spectroscopy and elementary analysis. The organic matter (OM) of sewage farm substrates has distinctly smaller C/N-ratios than the OM of control soils. The IR-spectra of the OM of sewage farms show that a considerable portion of the higher nitrogen content is localized in amide bonds.The mobil and easily oxidizable components of the OM of a sewage farm substrate are separated by fractional extraction. IR-spectra identify them as substances with ketóne-and ester structures respectively, as substances containing oligo-and polysaccharide structures or in low concentrations as substances with peptide bonds.
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