Features of the humification process in soils of Thala Hills, Enderby land, East Antarctica: Insights from 13C-NMR spectroscopy

Year 2026, Volume: 15 Issue: 1, 102 - 112, 02.01.2026

Ivan Alekseev Elena Grek

https://doi.org/10.18393/ejss.1834403

Abstract

In East Antarctica, ice-free areas (oases) exhibit a wide range of environmental conditions that influence soil development. Exploring the interactions between biological and abiotic factors, along with the composition and behavior of soil organic matter, offers valuable insights into how Antarctic ecosystems react to environmental stresses. This study examined the biogeochemical characteristics and molecular composition of soil organic matter in Cryosols of the Thala Hills oasis, Enderby Land, East Antarctica. The soils studied are generally shallow, with mostly coarse textures, slightly acidic to near-neutral pH levels (from 5.40 to 6.87), and very low organic carbon content in most of the samples (TOC<1%). We used 13C CPMAS NMR spectroscopy spectroscopy to evaluate the molecular composition of humic substances extracted from typical Leptic (Lithic) Cryosol and from an ornithogenic Cryosol. Significant peaks associated with carboxylic acids (170-190 ppm) indicated that organic matter transformation processes are influenced by vegetation cover, particularly moss-lichen communities. Humification processes were observed to be more pronounced in ornithogenic soils, as indicated by the formation of humic acids with a more developed peripheral aliphatic component (outer-chain aliphatic moieties) and higher sp²/sp³ carbon ratio. These ratios indicate a balance between aliphatic content—suggesting potential for decomposition—and aromatic structures that contribute to long-term stability.

Keywords

Humic acids , soil organic matter , humification , Cryosols , East Antarctica , 13C-NMR spectroscopy

Supporting Institution

Russian Science Foundation

Project Number

24-27-00361

Thanks

The research was supported by Russian Science Foundation (Project № 24-27-00361 «Soils in Eastern Antarctica oases: biogeochemistry, stability of organic matter and environmental risks») and within the framework of the Karelian Research Centre RAS research task № FMEN-2025-0002. The Authors would like to acknowledge Russian Antarctic Expedition, colleagues for their crucial help in fieldwork.

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