Evaluation of carbon stocks in the soils of Lena River Delta on the basis of application of “dry combustion” and Tyurin’s methods of carbon determination

Tomsk State University Journal of Biology

2019

Molecular and elemental composition of humic acids isolated from selected soils of the Russian Arctic Humic substances, isolated from selected soils of the Russian Arctic, were investigated in terms of molecular composition and stabilization rate. The degree of polar soil organic matter stabilization was assessed with the use of modern instrumental spectroscopy methods. The analysis of humic acid (HAs) preparations showed that aliphatic fragments prevail in the organic matter isolated in polar soils. The predominance of aliphatic fragments was revealed in HAs from soils located in the coastal zone, which could be caused by regular refreshment of organic matter during sin-lithogenic process and processes of hydrogenation in HAs. Breaking of the CC bonds and formation of chains with a high hydrogen content, which leads to the formation of aliphatic fragments in HAs, were noted. Data on the calculated atomic ratios of the elements in HAs are given and graphs show the main regularities in the formation of HAs and their properties. The integrated indicators of the molecular composition of humic acids of soils of the Russian Arctic are presented. The paper contains 4 Tables, 4 Figures and 44 References.

Section: Introductionmentioning

confidence: 99%

Molecular and elemental composition of humic acids isolated from selected soils of the Russian Arctic

Polyakov¹,

Chegodaeva

Tomsk State University Journal of Biology

2019

“…uncertainty is largely caused by the estimates having been calculated from observations that are highly spatially clustered (Hugelius et al, 2014) while extensive land areas remain uncharacterized due to the logistic difficulties of reaching these sites. Additionally, the calculation of these stocks are based on estimated data on soil bulk density and carbon values derived from dichromate oxidation methods (Abakumov and Popov, 2005;Polyakov et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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

Alekseev

2018

Solid Earth

Self Cite

Abstract. Previously, the structure and molecular composition of the Antarctic soil organic matter (SOM) has been investigated using 13C-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 13C-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.

“…The area occupied by permafrost-affected soils amounts to more than 8.6 million km 2 , which is about 27% of all land areas north of 50 • N [3]. The storage of SOM in high latitudes was estimated at 1672 × 10 12 kg, which comprises about 70% of all SOM in the world [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…Cryoturbation and cryogenic mass exchange also lead to the incorporation of organic matter into deeper soil horizons. Another process is the movement of organic matter in a dissolved state and its accumulation on the border with the permafrost table [5,7].…”

Section: Introductionmentioning

confidence: 99%

Humic Acids Isolated from Selected Soils from the Russian Arctic and Antarctic: Characterization by Two-Dimensional 1H-13C HETCOR and 13C CP/Mas NMR Spectroscopy

Polyakov

2019

Geosciences

Self Cite

Here we describe the molecular composition and resistance to decomposition of humic acids isolated from selected soils of the Russian Arctic and Antarctic. The degree of soil organic matter stabilization was assessed using modern instrumental methods: nuclear magnetic resonance spectroscopy (cross peak magic-angle spinning (CP/MAS) 13C-NMR and 1H-13C heteronuclear-correlation (HETCOR)). Analysis of the humic acids showed that aromatic compounds prevail in the organic matter formed in cryoconites, located on the surfaces of the glaciers. The predominance of aliphatic fragments is revealed in the soils of the Yamal peninsula and Antarctica. This could be caused by sedimentation of fresh organic matter exhibiting low decomposition stage due to the severe climate and processes of hydrogenation in the humic acids, destruction of the C-C bonds, and formation of chains with high hydrogen content. These processes result in formation of aliphatic fragments in the humic acids.