Analysis of molecular proxies of a peat core by thermally assisted hydrolysis and methylation-gas chromatography combined with multivariate analysis

- Analyses of a peat core by THM of soil organic matters.
- Analyses of molecular marker compounds, lignin, fatty acids and carbohydrates.
- Principal component analysis shows clearly three main clusters corresponding to the three well known ecological layers in a peat core: acrotelm, mesotelm and catotelm.

We applied principal component analysis on a data set of 55 compounds obtained with thermochemolysis with tetramethylammonium hydroxide as chemical agent from samples (24 different depths) along a one-meter length peat core. Principal component analysis allows to reduce the dimensionality of a data set that retains most of the variation present in the original variables (here F1 + F2 = 54.57%). Compounds are from four biochemical classes (lignin, carbohydrates and fatty and ω-hydroxy acids). Results show that samples are grouped in three clusters in the F1-F2 plot. Biomarkers of microbial and especially bacterial activity (terminally branched fatty acids) and of Sphagnum mosses (p-hydroxyphenyl compounds, fucose) are concentrated in the surface layers: the acrotelm (from 0 to −20 cm) and the mesotelm (from −20 to −50 cm). Biomarkers of higher plant contribution (C20+ fatty acids, C22 and C24 ω-hydroxy fatty acids, xylose and lignin compounds) are concentrated in the deeper layers of the peat core: the catotelm (from −50 to −100 cm).