ORGANIC-MATTER COMPOSITION IN SEWAGE FARM SOILS - INVESTIGATIONS BY C-13-NMR AND PYROLYSIS-FIELD IONIZATION MASS-SPECTROMETRY

The composition of soil organic matter (SOM) on sewage farms south of Berlin was investigated by solid-state CP/MAS C-13-NMR acid pyrolysis- field ionization mass spectrometry (Py-FIMS) of freeze-dried sewage so lids and soil samples of differing contamination. These were an untrea ted soil (USOIL), a former sewage farm used as arable land since 1990 (SF90A), and a recent sewage farm (SF1994). The CP/MAS C-13-NMR spectr a showed enrichments of the sewage-treated soils with aliphatic C and C in OCH3-groups and amino acids. In the Py-FI mass spectra the major markers of sewage and SOM in sewage farm soils were (i) N-containing c ompounds, in particular peptides, (ii) dimethylphthalate (m/z 194), (i ii) sterols, and (iv) signals in the mass range mit 502 to 554 of mono - and diaryl esters which were substituted by long aliphatic chains. T he latter signals were intense in the sewage solids, increased in inte nsity from sample SF90A to SF1994; but they were not present in the US OIL, thus clearly indicating anthropogenic origin. Temperature-resolve d Py-FIMS showed that the SOM compounds in the sewage farm soils were generally incorporated into bonds with widely different stabilities wh ich could be relevant for SOM turnover and environmental effects. This is demonstrated for the trapping of dimethylphthalate in a modelled h umic substance.