Molecular composition of raw peat and humic substances from permafrost peat soils of European Northeast Russia as climate change markers

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

“…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.…”

“…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.…”

“…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.…”

“…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.…”

The Molecular Composition of Humic Substances Isolated From Yedoma Permafrost and Alas Cores in the Eastern Siberian Arctic as Measured by Ultrahigh Resolution Mass Spectrometry

“…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, ).…”