Stability of soil organic matter in Cryosols of the maritime Antarctic: insights from 13 C NMR and electron spin resonance spectroscopy

• Published in: Solid Earth
• Main Authors: E. Abakumov, I. Alekseev
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: Geology; QE1-996.5; Stratigraphy; QE640-699; Antarctic; The Antarctic; King George Island; Fildes; Fildes peninsula; Antarc*; Antarctica; permafrost; Tundra
• Online Access: https://doi.org/10.5194/se-9-1329-2018; https://doaj.org/article/71790c89b1d94173b9972d645307c24e

Previously, the structure and molecular composition of the Antarctic soil organic matter (SOM) has been investigated using 13 C-NMR methods, which showed that in typical organo-mineral soils the aliphatic carbon prevails over the aromatic one, owing to the non-ligniferous nature of its precursor material. In this study, the SOM was analysed from different sample areas (surface level and partially isolated supra-permafrost layer) of the tundra-barren landscape of the Fildes Peninsula, King George Island, Western Antarctica. We found that the humic acids (HAs) of the cryoturbated, buried areas had lower amounts of alkyl aromatic and protonized aromatic compounds. In contrast, the HAs from the surface layers contain less alkyl carbon components. The free-radical content was higher in the surface layers than in the buried layers due to the presence of fresh organic remnants in superficial soil samples. New data on SOM quality from these two representative Cryosols will enable a more precise assessment of SOM stabilization rate in sub-Antarctic tundras. Comparison of the 13 C-NMR spectra of the HAs and the bulk SOM revealed that humification occurs in the Antarctic and results in accumulation of aromatic and carboxylic compounds and reductions in alkylic ones. This indicates that humification is one of the ways of soil organic matter stabilization.