Pyrolysis mass spectrometry of some Scirpus species and their decomposition products1

Four species of bulrushes (Scirpus acutus, Scirpus subterminalis, Scirpus validus, and Scirpus americanus) and the particulate decomposition products of S. acutus and S. subterminalis were analyzed by Curie‐point pyrolysis low‐voltage ionization mass spectrometry. The mass pyrograms of the emergent foliage of the fresh plants showed similarity in distribution of the pyrolysis products from polysaccharides, lignin, and protein. Mass peak m/z 120 differed markedly in relative abundance in these plants and was identified by pyrolysis gas‐chromatography MS as parahydroxystyrene, a pyrolysis product of paracoumaric esters. Decomposition was carried out in the laboratory under aerobic and anaerobic conditions at 10° and 25°C for 180 days. The mass spectra of the senescent S. acutus differed only slightly from the decomposition stages after 180 days at 25°C, but the mass spectra of decomposed senescent submersed foliage of S. subterminalis showed a reduction in pyrolysis products of neutral polysaccharides and an increase in products from proteins and bacterial amino sugar polymers especially after anaerobic decomposition. Large amounts of paracoumaric esters and lignin derivatives were found in all species. These compounds were resistant to degradation, suggesting that paracoumaric esters can influence the slow decay of emergent plants in the littoral zone of lakes.