Carbohydrate speciation and Py-MS mapping of peat samples from a subtropical open marsh environment

Abstract

Neutral carbohydrates were determined as alditol acetates in the hydrolysates of fractionated peat samples from different depths from Rookery Branch (Florida Everglades), and of a Mariscus rhizome. The fine grained samples showed a major contribution of microbial sugars indicated by comparatively low total carbohydrate yields together with high relative contributions of galactose, mannose, ribose, fucose, rhamnose, partially methylated aldoses, amino sugars, heptoses, tetroses, glycerol, allose and altrose. The coarse grained samples showed a major contribution of vascular plant sugars indicated by comparatively high total carbohydrate yields together with high relative contributions of glucose, xylose and arabinose. Analysis of the fractionated peat samples by Curie point pyrolysis-mass spectrometry and multivariate analysis of the pyrolysis data yielded two discriminant functions. Depth profiles for the first discriminant function show a relative accumulation of lignified vascular plant material with increasing depth in coarse and fine grained samples. The finest grained samples show most of the markers indicative for microbial activity and the presence of refractory fine grained matter and least of the lignin markers. Plots of the second discriminant function versus depth reveal an initial increase in markers for modified lignin, indicating degradation. The deepest sample, however, again shows increased characteristics for intact vascular plant polysaccharides. The results from both wet chemical analysis and Py-MS suggest the presence of living and/or senescent rootlets at the deepest level in the peat.