“…The use of modern instrumental methods such as one-and two-dimensional NMR spectroscopy is a reliable way to study the molecular composition of HAs in soils. Our results about 13 C (CP/MAS) NMR spectroscopy are in agreement with previous studies [6,11,18,19,24,[26][27][28]46,47,49]; the accumulation of aliphatic compounds in HAs composition can be related to the activity and composition of microbiota, hydrophobicity, and the composition of humification precursors [27,28,36,46,47]. Excessive moisture in the areas of King George isl.…”
Section: H-13 C (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Of Has supporting
confidence: 92%
“…Since the dipolar interaction in solids acts through space, correlation of unprotonated carbons with nearby (nonbonded) protons is possible, identifying the environment of those unprotonated groups; for instance, it can be determined whether COO groups are attached to aliphatic or aromatic cores [30,32]. HAs extraction yields were calculated as the percentage of carbon recovered from the original soil sample [46]. Elemental compositions of studied soils are presented in Table 4.…”
Section: H-13 C (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Methodsmentioning
confidence: 99%
“…The accumulation of aliphatic fragments is due to the composition of organic residues entering the soil, moss-lichen tundra vegetation predominates in the Yamal, which is more enriched in aliphatic compounds [27]. A high degree of hydrophobicity of the region is associated with the low microbiological activity of soils, which reduces the rate of transformation of organic residues in the soil and contributes to the accumulation of paraffin fragments [46]. The ratio of C,H-alkyl to O,N-alkyl, which characterizes the degree of decomposition of organic matter, is minimal for Yamal soils, which indicates a low degree of humification of organic matter relative to the other studied soils.…”
Section: C-1 H (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Of Has mentioning
confidence: 99%
“…Excessive moisture in the areas of King George isl. and the Yamal Peninsula may be the main factor affecting the composition of HAs in soils, as they limit the development of aerobic microorganisms in the soil and lead to the formation of anaerobic communities [28,36,46]. This method allows you to calculate the integrated signal intensities, as well as to separate the signals when they are imposed or at a high noise level.…”
Section: H-13 C (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Of Has mentioning
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.
“…The use of modern instrumental methods such as one-and two-dimensional NMR spectroscopy is a reliable way to study the molecular composition of HAs in soils. Our results about 13 C (CP/MAS) NMR spectroscopy are in agreement with previous studies [6,11,18,19,24,[26][27][28]46,47,49]; the accumulation of aliphatic compounds in HAs composition can be related to the activity and composition of microbiota, hydrophobicity, and the composition of humification precursors [27,28,36,46,47]. Excessive moisture in the areas of King George isl.…”
Section: H-13 C (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Of Has supporting
confidence: 92%
“…Since the dipolar interaction in solids acts through space, correlation of unprotonated carbons with nearby (nonbonded) protons is possible, identifying the environment of those unprotonated groups; for instance, it can be determined whether COO groups are attached to aliphatic or aromatic cores [30,32]. HAs extraction yields were calculated as the percentage of carbon recovered from the original soil sample [46]. Elemental compositions of studied soils are presented in Table 4.…”
Section: H-13 C (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Methodsmentioning
confidence: 99%
“…The accumulation of aliphatic fragments is due to the composition of organic residues entering the soil, moss-lichen tundra vegetation predominates in the Yamal, which is more enriched in aliphatic compounds [27]. A high degree of hydrophobicity of the region is associated with the low microbiological activity of soils, which reduces the rate of transformation of organic residues in the soil and contributes to the accumulation of paraffin fragments [46]. The ratio of C,H-alkyl to O,N-alkyl, which characterizes the degree of decomposition of organic matter, is minimal for Yamal soils, which indicates a low degree of humification of organic matter relative to the other studied soils.…”
Section: C-1 H (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Of Has mentioning
confidence: 99%
“…Excessive moisture in the areas of King George isl. and the Yamal Peninsula may be the main factor affecting the composition of HAs in soils, as they limit the development of aerobic microorganisms in the soil and lead to the formation of anaerobic communities [28,36,46]. This method allows you to calculate the integrated signal intensities, as well as to separate the signals when they are imposed or at a high noise level.…”
Section: H-13 C (Hetcor) and 13 C (Cp/mas) Nmr Spectroscopy Of Has mentioning
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.
“…However, all the above noted studies on the molecular composition of OM stored in permafrost were conducted on the relatively small portion of water‐soluble DOM (<10% of the total OC) released during permafrost thaw (Qualls & Haines, ). At the same time, the much larger portion of less oxidized and, hence, less water soluble OC is stored in the permafrost in the pool of immobile OM, which can be released from the sediments using alkali extraction (Vasilevich et al, ). This alkali‐extracted OM is traditionally referred to as humic substances (HSs) and comprises more than 50 % of soil OM (Stevenson, ).…”
Ongoing climate change is making the large pool of organic matter (OM) stored in Arctic permafrost vulnerable to mobilization; thus, garnering a deeper understanding of molecular transformations within the abundant pool of soil OM, specifically humic substances, is crucial. Here we present the first high-resolution mass-spectrometry examination of molecular compositions of humic acid (HA) and fulvic acid (FA) isolated from organic-rich deep yedoma (Pleistocene age ice-rich permafrost) and alas (thermokarst deposit formed during permafrost thaw) cores. The FA fractions were dominated by oxygen-rich unsaturated compounds, whereas the HA fractions were mostly composed of relatively reduced saturated and aromatic moieties. A substantial increase in contribution of both CHO-only and N-containing aliphatic compounds was observed in the HA fractions of the yedoma OM with depth, whereas the alas HA fractions were depleted in aliphatics but enriched with condensed and hydrolyzable tannins. The observed differences in compositional space of the immobile OM stored in the deep yedoma versus alas deposits were consistent with evolution of OM during thermokarst lake genesis, implying intense microbial degradation of N-rich OM released from the yedoma deposits and accumulation of highly degraded, plant-derived OM. The patterns of molecular transformations of OM were apparent in compositional space of the least degraded HA fractions as compared to much more oxidized FA fractions. This shows great promise of molecular exploration of the alkali-extracted OM, comprising up to 50% of the total organic carbon in deep permafrost both for paleoreconstructions and predictions of climate feedback to released OM due to permafrost thaw.
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