Thermolabile and Thermostable Organic Matter of Chernozems under Different Land Uses

Abstract

The purpose of the work is a comparative study of the molecular composition of thermolabile (volatilizes at 300°C) and thermostable (volatilizes at 500°C) fractions of organic matter from humus horizons of typical chernozems by double-shot pyrolysis followed by gas chromatographic separation and mass detection of the products. The objects of the study are typical chernozems under different land use types differing in the prevalent trends of organic matter transformation. As is shown, polysaccharides, furfural, and methylfurfural are the major contributors to the pyrolysis products of the chernozem thermolabile matter. The largest share of the pyrolysis products of thermostable matter belongs to nitrogen-containing compounds. It is demonstrated for the first time that the principal component analysis of the data on molecular composition of thermolabile organic matter makes it possible to divide the studied chernozems under different land uses into the groups reflecting the quasi-equilibrium state of soil organic matter, its degradation, or accumulation.