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International Journal of Ecology
Volume 2015, Article ID 390591, 7 pages
http://dx.doi.org/10.1155/2015/390591
Review Article

13C NMR and ESR Characterization of Humic Substances Isolated from Soils of Two Siberian Arctic Islands

1Department of Applied Ecology, Saint-Petersburg State University, 16 Line of Vasilyevsky Island, Saint Petersburg 199178, Russia
2Institute of Biology KomiSC UrB RAS, 28 Kommunisticheskaya Street, Syktyvkar, Komi Republic 167982, Russia
3Arctic and Antarctic Research Institute, 38 Beringa Street, Saint-Petersburg 199397, Russia

Received 23 July 2015; Revised 19 October 2015; Accepted 25 October 2015

Academic Editor: Ram Chander Sihag

Copyright © 2015 E. Abakumov et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Humic acids (HAs) and fulvic acids (FAs) of two Polar soils were investigated by 13C NMR and ESR spectroscopies, investigating the degree of humification and the molecular structure. One soil, from Bolshoi Lyakhovsky Island, contains two humus horizons: modern and buried. The other soil, from Wrangel Island, had only one modern humus horizon. The HAs and FAs of the two soils investigated show essential differences. The HAs show fewer oxygen-containing groups in comparison with the FAs, whereas the degree of aromaticity is two or three times higher in the HAs. The 13C NMR data also show that HAs are very different from FAs in terms of their molecular composition and hydrophobicity. Humification in the Arctic is limited by the very low content of lignin-derived compounds, due to the restricted vascular flora. As a result, the HAs, isolated from Polar soils, are more similar to the corresponding FAs than to the typical HAs of temperate soils. This was confirmed by ESR data, which show similar levels of free radical concentration for HAs and FAs and are related to the low level of aromaticity of both materials investigated. Apparently, the humification process in the soils of Polar Arctic deserts is in an initial stage.