ИСТИНА

Abstract: Arctic permafrost is a large-scale source of bio-labile organic matter (OM), the decomposition of which would contribute significantly to the global carbon cycle. During global warming, the particular attention should be paid to its release and fate. In order to study the evolution of conserved molecular pool as well as the processes of its transformation in modern conditions, it is necessary to establish molecular markers that are characteristic for the structure of permafrost OM. To achieve this goal, the most conservative fraction of permafrost OM - humic substances (HS) was extracted from six cores selected in the vic[inity of Lake Shchuchye in the Kolyma River basin. Cores were sampled from different depths varied from 3 to 15 m. A total of 18 samples of humic (HA) and fulvic acids (FA) were obtained. Molecular compositions were determined by ultrahigh resolution 7T Fourier transform ion cyclotron resonance mass-spectrometry (FTICR MS) equipped with electrospray ion source (ESI). Typical mass-spectra resolved up to 3500 CcHhOoNnSs molecular compositions for both HA and FA, respectively. HA comprised of saturated compounds. FA were characterized by the major contribution of oxidized unsaturated compounds. Such clear distinction of HA and FA molecular spaces is not typical for temperate regions. All molecular compositions were used for Boolean fingerprint intercomparison and PCA. Despite different depths of collections, samples were grouped according to extraction protocol. Nevertheless, the increase of peptide and lipids contributions with depth was explored.