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In the framework of the implementation of the all-Russian climatic project "Carbon measurement test sites", reference soils of "Seven Larches" carbon supersite, which is a benchmark and the only monitoring site in the Artistic latitudes, were investigated. The morphological structure of representative soils was specified, and it was found that soils are classified as Cryosols of different types (Histic, Stagnic or Gleyic). The basic physico-chemical characteristics of the soils were studied. By means of elemental analysis and 13C NMR spectroscopy, the composition and molecular structure of humic acids from organic and mineral soil horizons were studied. The surface (organic) soil horizons are characterized by high values of H:C molar ratios (1.2–1.3), which indicates a lower degree of the molecular structure aromaticity of humic acids from organic soil horizons. Analysis of the molecular structure of humic acids by 13C NMR spectroscopy showed that humic acids of the studied soils are characterized by the predominance of non-substituted aliphatic (0–47 ppm) and aromatic (108–164 ppm) fragments. Mineral soil horizons are characterized by higher stabilization of organic matter (with lower SOC content—0.5–0.9%) and higher hydrophobicity of humic acid molecules. Comparison of the obtained results with previously published data on the structural and elemental composition of humic acids isolated from soils of similar genesis and geographical location did not reveal any significant differences between the data obtained by us and previously published data. Thus, for "Seven Larches" carbon supersite "reference" parameters of elemental composition of humic acids, their molecular composition and degree of stabilization of soil organic matter were identified. [ABSTRACT FROM AUTHOR]

Post-agrogenic transformation of fallow soils leads to changes in soil carbon content, the molecular composition of humic substances, and rates of organic matter stabilization, which can affect climate change on the planet. In this regard, we analyzed the molecular composition of humic acids isolated from natural and fallow soils in the southern Taiga zone of northwest Russia. Different-aged soils on fallow lands represent a model of soil transformation in time, and data on the transformation of soil humic acid molecular composition make a significant contribution to the understanding of soil organic matter stabilization aspect issues. In this case, the molecular structure of humic acids isolated from natural and fallow soils in northwest Russia was analyzed. To study the molecular composition of HAs, the elemental composition was analyzed, and 13C (CP/MAS) NMR spectroscopy of HAs isolated from different aged abandoned soils and soils of different types of use was carried out. The obtained data showed that with the increasing age of soils in the fallow state, there is an increase in the carbon content of humic acids as well as a decrease in nitrogen content. As a result of the increasing age of soils in the fallow state, there are dynamics in the content of aromatic structural fragments in humic acids: 34% for 40 years old, 28% for 80 years old, and 31% for 120 years old. This is due to changes in the precursors of humification and the further transformation of plant residues in the soil. Re-involved fallow land soils lead to an increase in the content of aromatic structural fragments in the composition of HA in relation to HA extracted from mature soils. The lowest content of aromatic structural fragments was observed in the humic acids of 130-year-old agricultural soil, which is associated with the long-term application of organic fertilizers. [ABSTRACT FROM AUTHOR]

Drainage associated with land use change in tropical peatlands has increased the rate of decomposition of peat soils and contributed to CO2 emissions. Increased decomposition may result in changes in the composition of the soil organic carbon (SOC). We examined the carbon functional group composition and degree of decomposition of peat soils under five different land uses to understand the effects of changing management intensity on tropical peatland soils. Samples were collected from seven sites spanning five different land uses (forest, shrubland, fernland, revegetation, smallholder oil palm) at the Pedamaran peatland in South Sumatra, Indonesia. SOC composition, measured by Solid-state 13C Nuclear Magnetic Resonance (NMR) spectroscopy, was dominated by the alkyl carbon (C) functional group in managed peatlands. However, in the forest far from drainage canals, the SOC comprised predominantly O-alkyl C. The contributions of the functional groups ketone C, carbonyl C and O-aryl C were low and tended to occur in stable proportions throughout the soil profiles. Drainage and land use change significantly affected peat carbon chemistry. The effects were greatest under oil palm, where O-alkyl C had been depleted rapidly under aerobic conditions leading to a change in the dominant carbon functional group from O-alkyl C to alkyl C. Furthermore, our results indicate that the alkyl C:O-alkyl C ratio is a more useful and informative indicator of the degree of decomposition of peat soil than the traditionally used C:N ratio. This more nuanced understanding of the different types of carbon that make up tropical peat soils under different land uses can be applied to support peatland restoration. In particular, nutrient cycling and water availability are likely to be influenced by carbon functional group and degree of decomposition. In order to reduce fire risk and support Indonesia’s aspirations to manage the national forest estate as a net carbon sink, further research into the links between peat soil organic carbon chemistry, revegetation performance and new peat accumulation is recommended.

Drainage associated with land use change in tropical peatlands has increased the rate of decomposition of peat soils and contributed to CO2 emissions. Increased decomposition may result in changes in the composition of the soil organic carbon (SOC). We examined the carbon functional group composition and degree of decomposition of peat soils under five different land uses to understand the effects of changing management intensity on tropical peatland soils. Samples were collected from seven sites spanning five different land uses (forest, shrubland, fernland, revegetation, smallholder oil palm) at the Pedamaran peatland in South Sumatra, Indonesia. SOC composition, measured by Solid-state 13C Nuclear Magnetic Resonance (NMR) spectroscopy, was dominated by the alkyl carbon (C) functional group in managed peatlands. However, in the forest far from drainage canals, the SOC comprised predominantly O-alkyl C. The contributions of the functional groups ketone C, carbonyl C and O-aryl C were low and tended to occur in stable proportions throughout the soil profiles. Drainage and land use change significantly affected peat carbon chemistry. The effects were greatest under oil palm, where O-alkyl C had been depleted rapidly under aerobic conditions leading to a change in the dominant carbon functional group from O-alkyl C to alkyl C. Furthermore, our results indicate that the alkyl C:O-alkyl C ratio is a more useful and informative indicator of the degree of decomposition of peat soil than the traditionally used C:N ratio. This more nuanced understanding of the different types of carbon that make up tropical peat soils under different land uses can be applied to support peatland restoration. In particular, nutrient cycling and water availability are likely to be influenced by carbon functional group and degree of decomposition. In order to reduce fire risk and support Indonesia's aspirations to manage the national forest estate as a net carbon sink, further research into the links between peat soil organic carbon chemistry, revegetation performance and new peat accumulation is recommended. [ABSTRACT FROM AUTHOR]

A comparative study of the supramolecular structure, physicochemical properties, and morphology of the powder celluloses (PCs) obtained from the waste paper of newsprint and cardboard, plant celluloses, and nonconventional raw materials was conducted using the methods of FT-IR spectroscopy, high-resolution solid-state 13C NMR spectroscopy, wide-angle X-ray scattering, and scanning electron microscopy (SEM). According to the FT-IR and 13C NMR spectroscopy results, the functional composition of the PCs is similar to that of the wood PCs and matches highly purified cellulose samples. The crystallographic structure of the powder samples corresponds to the structure of cellulose I. The crystallinity and the transverse dimensions of the crystallites are 39.4 and 40.2%, and 45 Å [110] and 54 Å [110], for the PCs from newsprint paper and cardboard, respectively. These values considerably exceed those for the initial waste paper samples. A comparative analysis of the SEM results showed a significant similarity among the PC fibers of different origin. The results of the study of the physicochemical properties of the PCs isolated from the waste paper allow predicting their competitive application in comparison with plant PCs. [ABSTRACT FROM AUTHOR]

A comprehensive study of the chemical and group composition of organic and mineral fractions of brown coal from the Raichikhinskoe deposit was carried out. Chemical and technological parameters were determined and the textural characteristics of coal were studied. It was found that the mineral component of coal is clayey in nature and has a stable composition. The variability in the composition of the organic matter of coal indicates the facies instability of sedimentation conditions in the studied areas of coal accumulation. [ABSTRACT FROM AUTHOR]

Eight triterpenoids (lupeol, taraxasterol, α-amyrin, β-amyrin, 3-O-acetyllupeol, 3-O-acetyl- α -amyrin, 3-O-acetyl- β-amyrin, and 3-O-acetyltaraxasterol) were identified for the first time in ovate-leaf atractylodes [Atractylodes ovata (Thunb.) DC.] growing in Primorsky Territory of the Russian Far East using 13C NMR spectroscopy and mass spectrometry with electron-impact ionization. The effect of the nature of the extractant (hexane, CCl4 , 95% EtOH) on the yield of triterpenoids from the aboveground and underground organs of A. ovata was studied. The triterpenoids were extracted most from the starting raw material using CCl4 (inflorescences, 4.87%; leaves, 1.41%; roots, 0.25%); least, using EtOH (inflorescences, 2.04%; leaves, 1.25%; roots, 0.10%). The compositions of triterpenoids in extracts of the aboveground and underground organs of A. ovata were determined by GC-MS. Lupeol was shown to be the dominant triterpenoid in leaves and roots of A. ovata (0.39 ± 0.03 and 0.10 ± 0.02%, respectively), whereas 3-O-acetyl- β-amyrin dominated in inflorescences (1.11 ± 0.04%). [ABSTRACT FROM AUTHOR]

Carbon sequestration in Plaggic Anthrosols is most often investigated by bulk soil carbon inventories, without considering the form in which the carbon is stored (e.g., particulate or mineral-associated organic matter (OM), its capacity, or its chemical composition). Here, we focus on the unusual high organic carbon (OC) accumulation in sandy Plaggic Anthrosols and adjacent reference soils under agricultural use. In these soils, the mineral fraction ≤20 µm which is commonly assumed to be the major factor for OC stabilization, are very low in mass proportion. Soil organic matter (SOM) physical fractionation was done to evaluate the quantity and quality of OC in the topsoil (Ap horizon). For the fraction ≤20 µm (medium and fine silt-, and clay-sized particles), we measured the concentration of OC and calculated its OC storage capacity and contribution. The OC of the fraction ≤20 µm was radiocarbon-dated and analyzed for its chemical composition by solid-state 13C NMR spectroscopy. The highly sandy (∼90 % sand and coarse silt) soils showed an accumulation of OC much higher than the conventionally calculated saturation level controlled by the proportion of the fraction ≤20 µm. Unexpectedly, Plaggic Anthrosols and the respective reference soils showed similar fractional OC concentrations, radiocarbon ages, and OM composition. The isolated fraction ≤20 µm contained, on average, 81 % of the total soil OC in only 9 % of the corresponding soil mass. All soil fractions ≤20 µm are characterized by a high mean OC concentration in the topsoil (reference soils: 226 ± 66.5 mg OC g−1, Plaggic Anthrosols: 202 ± 59.0 mg OC g−1) with a C/N ratio of 15 on average for both soils. The OM composition of the fraction ≤20 µm was specifically rich in alkyl-C, with unusually low proportions of O-alkyl-C and low contents of aryl-C. The radiocarbon concentration (F14C) indicated that topsoil OM of the ≤20 µm fraction is stored for long time periods with high mean conventional radiocarbon ages (14C) not only for Plaggic Anthrosols (F14C: 0.92 ± 0.04; 14C: 639 yBP) but also for the reference soils (F14C: 0.93 ± 0.04; 14C: 575 yBP) and received low inputs of OC derived from recent photosynthesis. Our data indicate the existence of specific SOM accumulation processes in the investigated sandy agricultural soils, resulting particularly large SOM stocks which cannot be explained by mechanistic association of OM with mineral surfaces. It is not clear, if this inherited OM is stable under present-day soil and management conditions.

Soil organic matter stability and transformation affected by agriculture is a global problem of great concern. This study aimed to reveal structural changes in humic molecules under conventional soil tillage in Cambisols of the Transbaikal area. Humic acids were isolated from the humus horizons of native and arable variants of Eutric Cambisol Cryic (gleyic, humic, loamic) from the forest steppe, and Haplic Cambisol (arenic, humic, protocalcic) from the steppe zone. The changes in the humic substances' quality were evaluated by means of an elemental analysis and 13C nuclear magnetic resonance spectroscopy. The results indicate that different agronomic management affected the changes in the composition and molecular structure of humic acids. Soil tillage induced an increase in the carbon content, the proportion of aromatic compounds and carboxyl groups and the depletion in nitrogen. As measured by 13C NMR spectroscopy, the intensity of these changes was determined by soil properties and the hydrothermal regime. Organic matter from Eutric Cambisol Cryic was suggested as providing significant environmental resistance to the agricultural impact due to the optimization of the water regime and a loamy texture. Prolonged ploughing of sandy Haplic Cambisol under the arid conditions promoted deep changes in the humic substances' composition and chemical structure. [ABSTRACT FROM AUTHOR]

Chronic alcohol use disorder, a major risk factor for the development of neuropsychiatric disorders including addiction to other substances, is associated with several neuropathology including perturbed neuronal and glial activities in the brain. It affects carbon metabolism in specific brain regions, and perturbs neuro-metabolite homeostasis in neuronal and glial cells. Alcohol induced changes in the brain neurochemical profile accompany the negative emotional state associated with dysregulated reward and sensitized stress response to withdrawal. However, the underlying alterations in neuro-astroglial activities and neurochemical dysregulations in brain regions after chronic alcohol use are poorly understood. This study evaluates the impact of chronic ethanol use on the regional neuro-astroglial metabolic activity using 1H-[13C]-NMR spectroscopy in conjunction with infusion of [1,6-13C2]glucose and sodium [2-13C]acetate, respectively, after 48 h of abstinence. Besides establishing detailed 13C labeling of neuro-metabolites in a brain region-specific manner, our results show chronic ethanol induced-cognitive deficits along with a reduction in total glucose oxidation rates in the hippocampus and striatum. Furthermore, using [2-13C]acetate infusion, we showed an alcohol-induced increase in astroglial metabolic activity in the hippocampus and prefrontal cortex. Interestingly, increased astroglia activity in the hippocampus and prefrontal cortex was associated with a differential expression of monocarboxylic acid transporters that are regulating acetate uptake and metabolism in the brain. [ABSTRACT FROM AUTHOR]

Application of high resolution 13C nuclear magnetic resonance (NMR) spectroscopy to characterize Cuba oil and oil-containing rock samples from Cuban basin was demonstrated. The chemical shifts of 13C NMR functional groups for later determination the composition of the oil and rock samples were determined. The different contribution of the studied samples in the aliphatic and aromatic areas was determined. Molar fractions of primary, secondary, quaternary, tertiary, aromatic groups, aromaticity factor and the mean length of hydrocarbon chain length of aliphatic hydrocarbons were estimated. Comparative analysis on the quantitative level for all major hydrocarbon components, the aromaticity factor and the mean length of the hydrocarbon chain were carried out.

Abstract Background Organic materials carbon is mainly sequestrated in humin. However, the carbon (C) stability of humin with organic materials amendments in different types of soils is mainly affected by organic materials or soil types as well as the enzymatic reaction is important for understanding the C sequestration mechanism of soil. Results In this study, straw and straw-derived biochar were incorporated into three different types of soils. Using 13C nuclear magnetic resonance (NMR) spectroscopy, the structural composition of humin (Hu) was analyzed, along with the urease and β-glucosidase activities. The results showed that biochar amendment enhanced aryl C to 49.63%–76.55% while straw amendments increased O-alkyl C of Hu to 33.99%–51.70%. Two-way ANOVA analysis revealed significant differences in the impact of soil types and treatments on enzyme activities and functional groups of humin. A significant positive correlation was found between β-glucosidase activity and O-alkyl C, phenolic C, and methoxyl C of humin. In addition, urease activity showed a significant positive correlation with alkyl C of humin. Compared to tobacco straw, tobacco straw-biochar amendment increased β-glucosidase activity for 22.01 mg kg−1 d−1, 26.01 mg kg−1 d−1 and 14.01 mg kg−1 d−1 in three types of soils, respectively. Conclusions These results showed that β-glucosidase contributed to the transformation of humin functional groups and was influenced by organic materials and soil types, especially the organic materials types. The findings imply that straw or straw-derived biochar application stimulates urease and β-glucosidase activities, which improves the alternation of functional groups of humin in different types of soil. Graphical Abstract

[Display omitted] Sodium oleate (NaOL) self-aggregates in water forming rodlike micelles with different length depending on NaOL concentration; when KCl is added wormlike micelles form, which entangle giving rise to a viscoelastic dispersion. It is expected that aggregates with different size and shape exhibit different internal and overall molecular motions and collective dynamics. Two low viscosity NaOL/water and two viscoelastic NaOL/KCl/water formulations with different NaOL concentration (0.23 and 0.43 M) were investigated by 1H fast field cycling NMR relaxometry over broad temperature and Larmor frequency ranges, after a first screening by 1H and 13C NMR spectroscopy at high frequency. The analysis of the collected data indicated that fast conformational isomerization and rotation of NaOL about its long molecular axis and lateral diffusion of NaOL around the axis of the cylindrical aggregates are slightly affected by the aggregate shape and length. On the other hand, fluctuations of the local order director are quite different in the fluid and viscoelastic systems, reflecting the shape and size of the aggregates. Quantitative information was obtained on activation energy for fast internal and overall motions, correlation times and activation energy for lateral diffusion, and coherence length for collective order fluctuations. [ABSTRACT FROM AUTHOR]

Application of high resolution 13C nuclear magnetic resonance (NMR) spectroscopy to characterize crude oil was demonstrated. The chemical shifts of 13C NMR functional groups that determine the composition of the oil sample were determined. Molar fractions of primary, secondary, quaternary, tertiary, aromatic groups, aromatic factor and average hydrocarbon chain length of aliphatic hydrocarbons of the oil sample according to 13C NMR spectra were determined. Detailed description of the 13C NMR spectra of the oil sample using a single consideration of three NMR spectra: 13C, 13C Attached Proton Test (APT), 13C with Gated Decoupling (GD) was performed. The different contribution of the studied oil sample in the aliphatic (10–75 ppm) and aromatic (115–165 ppm) areas of the 13C NMR spectra was determined. The presence of all major hydrocarbon components in the studied oil sample was established on the quantitative level, the aromaticity factor and the mean length of the hydrocarbon chain were evaluated. Quantitative fractions of aromatic molecules and functional groups constituting oil hydrocarbons were determined. In this work we demonstrate that the attached proton test and gated decoupling 13C NMR spectroscopy can afford all information to complete the chemical shift assignment of an oil sample, especially for determination of long range 1H–13C coupling constants and 13C multiplicity.

13C NMR spectroscopic investigations were conducted for various amino acid derivatives and peptides. It was observed that 13C NMR chemical shifts of the carbonyl carbons are correlated with the solvent polarities, but the extent depends on the structures. The size of the functional groups and inter- and intra-molecular hydrogen bonding appear to be the major contributors for this tendency.

Soils of the Arctic sea coasts are one of the least studied due to the complex logistical accessibility of the region, as well as the severe climatic conditions. The genesis of these soils is determined by several factors of soil formation simultaneously—cryogenesis, the influence of river alluvial processes, as well as the tidal influence of the sea. The paper presents data on the morphological structure of soils formed on the seacoast of the East-Siberian Sea (Kolyma Lowland, North Yakutia). Under the influence of cryogenesis and sea water tidal input, marsh soils are formed, with a relatively high level of salinity and the development of gleyization. Autochthonous and allochthonous soil organic matter play a leading role in marsh soil formation here, including the possible accumulation and biochemical transformation of incoming pollutants (e.g., hydrocarbons). The main objective of the study was to evaluate the soil organic matter genesis and alteration under the influence of tidal processes in coastal permafrost-affected soils as well as to obtain the previously unknown characteristics of the structural and elemental composition of different fractions of organic matter. The elemental composition and 13C NMR spectroscopy of humic acids were analyzed. It was revealed that humic acids extracted from the studied marsh soils accumulate up to 50% C and 4% N. Active processes of dehydrogenation are noted in HAs molecules, which indicates a relatively low degree of aliphatic structure development. According to 13C NMR spectroscopy, it was revealed that up to 45% of aromatic structural fragments accumulate in marsh soils, indicating a relatively high degree of organic matter stabilization and resistance to biodegradation. [ABSTRACT FROM AUTHOR]

Spider dragline silk has unique characteristics of strength and extensibility, including supercontraction. When we use it as a biomaterial or material for textiles, it is important to suppress the effect of water on the fiber by as much as possible in order to maintain dimensional stability. In order to produce spider silk with a highly hydrophobic character, based on the sequence of ADF-3 silk, we produced recombinant silk (RSSP(VLI)) where all QQ sequences were replaced by VL, while single Q was replaced by I. The artificial RSSP(VLI) fiber was prepared using formic acid as the spinning solvent and methanol as the coagulant solvent. The dimensional stability and water absorption experiments of the fiber were performed for eight kinds of silk fiber. RSSP(VLI) fiber showed high dimensional stability, which is suitable for textiles. A remarkable decrease in the motion of the fiber in water was made evident by 13C solid-state NMR. This study using 13C solid-state NMR is the first trial to put spider silk to practical use and provide information regarding the molecular design of new recombinant spider silk materials with high dimensional stability in water, allowing recombinant spider silk proteins to be used in next-generation biomaterials and materials for textiles. [ABSTRACT FROM AUTHOR]

Background: Organic materials carbon is mainly sequestrated in humin. However, the carbon (C) stability of humin with organic materials amendments in different types of soils is mainly affected by organic materials or soil types as well as the enzymatic reaction is important for understanding the C sequestration mechanism of soil. Results: In this study, straw and straw-derived biochar were incorporated into three different types of soils. Using 13C nuclear magnetic resonance (NMR) spectroscopy, the structural composition of humin (Hu) was analyzed, along with the urease and β-glucosidase activities. The results showed that biochar amendment enhanced aryl C to 49.63%–76.55% while straw amendments increased O-alkyl C of Hu to 33.99%–51.70%. Two-way ANOVA analysis revealed significant differences in the impact of soil types and treatments on enzyme activities and functional groups of humin. A significant positive correlation was found between β-glucosidase activity and O-alkyl C, phenolic C, and methoxyl C of humin. In addition, urease activity showed a significant positive correlation with alkyl C of humin. Compared to tobacco straw, tobacco straw-biochar amendment increased β-glucosidase activity for 22.01 mg kg−1 d−1, 26.01 mg kg−1 d−1 and 14.01 mg kg−1 d−1 in three types of soils, respectively. Conclusions: These results showed that β-glucosidase contributed to the transformation of humin functional groups and was influenced by organic materials and soil types, especially the organic materials types. The findings imply that straw or straw-derived biochar application stimulates urease and β-glucosidase activities, which improves the alternation of functional groups of humin in different types of soil. [ABSTRACT FROM AUTHOR]

The goal of this work is to find out whether the chemical fractions isolated by traditional alkaline extraction are associated with any specific physical fractions. The approach consists in comparison of the specific structural features (assessed according to solid-phase 13C-NMR spectroscopy data) and the contributions of the fractions of both types to total soil organic carbon. The object of the study is Haplic Chernozem of two contrasting land uses: virgin steppe and long-term bare fallow. The investigated chemical fractions are humic acids, humin, and the composite fraction comprising the fulvic acids and organic matter of hydrochloric acid extract, and the colloids precipitated from alkaline extract. The physical fractions obtained according to particle size–density distribution comprise the light fraction occluded in aggregates, clay-sized fraction, and the residue remaining after the separation of light fractions and clay. In the virgin soil, the following fraction pairs have similar structural characteristics of the organic matter and the contributions to soil organic carbon: humic acids–occluded light fraction, composite fraction–clay; humin–residue after physical fractionation. As for the fallow soil, the structural composition of the organic matter is also similar in the above listed pairs but their contributions to the total soil carbon are markedly different. Thus, the chemical fractions in the uncultivated chernozem are associated with particular physical fractions, which is unobservable in degraded bare fallow soil. A comparison of the carbon weight in all fractions of two examined soil variants shows that all fractions lose carbon with soil degradation but the highest loss among the chemical fractions is unexpectedly observed for humin (61%), whereas among versus the physical fractions the highest loss is observed in the occluded light fraction (66%). [ABSTRACT FROM AUTHOR]

The purpose of our research is focused on examination of the transformation regularities of molecular composition of humic acids (HAs) in the hummocky frozen peatlands of the European Arctic as a marker of climatic changes in the Holocene, and assessment of the stabilization of soil organic matter under the conditions of modern climatic warming. Histosols located in the two subzones of the European Arctic served as the research subjects. This territory is actively used for reindeer breeding, which is a vital agricultural branch in the Far North of the Russian Federation. The data obtained reveal the main trends in the formation of HAs from Arctic peatlands under different environmental conditions. Modern peat sediments (top layers) in the middle and late Holocene period formed out of bryophyte residues and contained HAs with long-chain carbohydrate and paraffin structures in their composition. These structures enlarged the dynamic radii of HA molecules, and, thus, caused high average molecular weight values. The more favorable climatic conditions of the early Holocene (the Atlantic optimum) defined the botanical composition of peat, which was dominated by tree and sedge communities with high contents of lignin components and, as a consequence, a larger share of aromatic fragments, characterized by thermo-biodynamic resistance in HAs of horizons in the lower and central profile parts. The molecules of HAs are an archive of paleoclimatic records. The Subboreal and Subatlantic climatic conditions determined the specifics of vegetation precursors and, as a result, the molecular structure of HAs in seasonally thawed layers, with a predominance of long-chain aliphatic fragments. The conversion of HAs from Histosols led to an increase in the proportion of carbon in branched and short-chain paraffinic structures with their subsequent cyclization and aromatization. The results of this process are most clearly manifested in layers formed during the Holocene I and II climatic optima. Higher biologically active temperatures of the seasonally thawed layer of soils at bare spots (without vegetation) determined the accumulation of thermodynamically more stable HA molecules with a high content of aromatic fragments. This contributed to both the stabilization of the SOM and the conservation of peatlands in general. [ABSTRACT FROM AUTHOR]

The incorporation of organic materials derived from plant biomass into various soils is an effective strategy for increasing soil organic carbon (SOC). The comparative effect of organic material forms and soil types on carbon (C) sequestration has received little attention. On a C equivalent basis, wheat straw, wheat straw‐biochar, tobacco straw, and tobacco straw‐biochar were added to different soil types such as acidic, saline, and calcareous and incubated for 180 days. The structural characteristics of SOC, humic substance (HS) contents, and enzyme activities were investigated, and it was discovered that the C content of crop straws and biochar was primarily fixed in the form of humin (HU) in all soil types. Furthermore, biochar application did not increase humic acid (HA), whereas crop straws treatments did. Between HU and SOC, there was a significant positive correlation. SOC Aryl C was increased by biochar treatments, whereas phenolic C and O‐alkyl C were increased by straw treatments. Aromatic C correlated positively with SOC concentration, whereas polyphenol oxidase activity correlated positively with O‐alkyl C. The activity of polyphenol oxidase influenced the ormation of O‐alkyl C significantly. The majority of SOC functional groups and enzyme activities were found to have significant relationships with HS contents (p value <0.05). These findings suggest that both soil types and organic materials influence HS and functional groups of SOC, with organic materials having a stronger influence on microbial activity than soil types. Biochar can be used for a wide range of soils to not only store more recalcitrant C but also make SOC more hydrophobic. [ABSTRACT FROM AUTHOR]

Knowledge of the stability of soil organic C (SOC) is vital for assessing SOC dynamics and cycling in agroecosystems. Studies have documented the regulatory effect of fertilization on SOC stability in bulk soils. However, how fertilization alters organic C stability at the aggregate scale in agroecosystems remains largely unclear. This study aimed to appraise the changes of organic C stability within soil aggregates after eight years of fertilization (chemical vs. organic fertilization) in a greenhouse vegetable field in Tianjin, China. Changes in the stability of organic C in soil aggregates were evaluated by four methods, i.e., the modified Walkley-Black method (chemical method), 13C NMR spectroscopy (spectroscopic method), extracellular enzyme assay (biological method), and thermogravimetric analysis (thermogravimetric method). The aggregates were isolated and separated by a wet-sieving method into four fractions: large macroaggregates (>2 mm), small macroaggregates (0.25–2 mm), microaggregates (0.053–0.25 mm), and silt/clay fractions (macroaggregates>silt/clay fractions. Meanwhile, organic C spectroscopic, thermogravimetric, and biological stability were the highest in silt/clay fractions, followed by macroaggregates and microaggregates. Moreover, the modified Walkley-Black method was not suitable for interpreting organic C stability at the aggregate scale due to the weak correlation between organic C chemical properties and other stability characteristics within the soil aggregates. These findings provide scientific insights at the aggregate scale into the changes of organic C properties under fertilization in greenhouse vegetable fields in China.

Diorganotin carboxylates have received much interest in past decades due to their rich structural chemistry and wide range of applications in various fields. This review study provides an in-depth analysis of carbon NMR data of dimethyltin complexes. The absorptions shown by the carbonyl carbon, methyl groups attached to tin and the other carbons present in the complexes were presented in this study. The effects of nature and the number of substituents attached are also described in this report.

13C NMR spectroscopic investigations were conducted for various amino acid derivatives and peptides. It was observed that 13C NMR chemical shifts of the carbonyl carbons are correlated with the solvent polarities, but the extent depends on the structures. The size of the functional groups and inter- and intra-molecular hydrogen bonding appear to be the major contributors for this tendency [ABSTRACT FROM AUTHOR]

Due to frequent volcanic activity and erosion of dryland soils, magnified by land use after human settlement (ca. 870 CE), peatlands in Iceland receive regular additions of mineral eolian deposits. Their soils may develop not only histic but also andic characteristics. Yet, mineral eolian deposition as an environmental determinant of peatlands in Iceland is still poorly understood, not least with regard to the peatlands carbon (C) stores. This study advances our understanding of the impact of tephra deposition on Histosols by elucidating interactions between C characteristics and andic soil properties. We compare Histosols from three Icelandic peatlands of different degrees of exposure to eolian deposition by evaluating data sets of their C structure derived by 13C NMR spectroscopy, andic soil properties based on selective extractions of Al, Fe, and Si, and decomposition proxies C/N, δ13C, and δ15N. By applying multivariate statistical methods, we are able to present several important patterns. Soil organic matter of Histosols with andic properties is less decomposed than that of Histosols without notable andic properties. Andic soil properties seem to impact their C structure by facilitating the formation of organo‐mineral complexes, which particularly hamper the decomposition of chemically more labile C groups. Tephra layers appear to hamper microbial activity in deeper soil layers by preventing input of fresh organic matter. The interaction of andic and histic soil properties and the protective role of major tephra deposits may enable an unusual potential for long‐term C stabilization in a natural peatland environment. Plain Language Summary: Peatlands belong to the greatest terrestrial carbon stores worldwide. Their organic soils possess exceptional capacities for long‐term carbon storage. Peatlands in Iceland are unusual as they receive comparatively great amounts of windborne mineral material from volcanic eruptions or sparsely vegetated and eroded drylands. These mineral additions of volcanic origin to the otherwise organic substrate of the peatlands shape their soil characteristics and set them apart from similar soils in neighboring countries. On the one hand, they bear characteristics typical for organic soils in Nordic peatlands, on the other hand they possess characteristics of mineral soils of volcanic regions. Little is known about the impact of interactions between these characteristics on the peatlands carbon stores. This study increases our knowledge on carbon storage of peatlands in volcanic regions. We compare soils from three peatlands in northwest Iceland and shed light on interactions between their mineral and organic constituents, with a particular focus on soil organic carbon. We find strong indications that decomposition processes are slower in soils with stronger characteristics of mineral volcanic soils. In undisturbed (anaerobic) peatlands, this seems to impact long‐term carbon storage positively, but in disturbed (aerobic) peatlands, it might pose a threat of accelerated carbon emissions. Key Points: Andic soil properties impact the carbon structure of Histosols of volcanic regions and their carbon storage capacityAndic soil properties and thick tephra deposits appear to enhance long‐term carbon stabilization in undisturbed peatlandsRelatively undecomposed Histosols with andic properties may be a greater source of atmospheric carbon upon disturbance than anticipated [ABSTRACT FROM AUTHOR]

Purpose: Applying carbon-rich materials, such as those resulting from pyrolysis (biochar) or composting (compost), to the agro-ecosystems has been proven to improve soil organic carbon (SOC) storage and reduce CO2 emissions. However, it is not clear how earthworms drive changes in soil C sequestration and mineralization under biochar/compost incorporation. Materials and methods: A 288-day microcosm experiment was conducted to investigate the effects of earthworms on the concentrations of SOC and its fractions, the structural characteristics of SOC and CO2 emissions following three straw incorporation treatments (maize straw, maize straw compost, and maize straw biochar), and no straw addition was used as the control. Each treatment had two variants: one with earthworms (Eisenia nordenskioldi) and one without earthworms. The elemental analysis, 13C NMR spectroscopy, and three-dimensional fluorescence technologies were used to characterize the features of SOC. Results and discussion: Results indicated that the incorporation of straw, compost, and biochar significantly improved the SOC contents compared with the control. Earthworms did not affect the SOC fractions in the control soil but led to the increase in SOC and humic acid (HA) under compost incorporation. The molecular structures of HA showed features pointing to high degrees of humification and aromaticity, as presented by elemental composition, fluorescence intensities, and 13C NMR. The increase of SOC and a slight reduction of CO2 emission in compost-amended soil could be attributed to the accumulation of more stable HA caused by earthworms. In contrast, earthworm presence decreased the aromaticity of HA in biochar-amended soil, and made its structure more hydrophilic, which was not conducive to C sequestration. In addition, the mineralization of microbial C by earthworms also led to an increased CO2 emission from biochar-amended soil. Conclusions: Earthworms weaken the ability of biochar to reduce soil CO2 emissions but improve the C sequestration capacity of compost-amended soil. This study improves our understanding of the contributions of soil macrofauna on the SOM formation and stabilization after incorporation of different maize straw-derived materials. [ABSTRACT FROM AUTHOR]

To improve soil health and to aid in climate change mitigation, the quantity of soil organic matter (SOM) should be maintained or increased over the long run. In doing so, not only the total quantity of SOC but also the stability of SOC must be considered. Stability of SOC increases as a function of resistance to microbial decomposition or microbial substrate use efficiency through chemical, biological, and physical mechanisms including humification, hydrophobic moieties, molecular diversity, and formation of macroaggregates. One of the mechanisms that enhance stability confers changes in the distribution of C functional groups of SOM. To better understand and quantify how these changes are influenced by agricultural management practices, we collected 670 pairwise data from the body of literature that has evaluated changes in the distribution of C functional groups of SOM measured by solid-state 13C NMR spectroscopy. The types of agricultural managements discussed herein include (1) fertilization, (2) tillage, (3) crop rotation, (4) grazing, and (5) liming practices. Our meta-analyses show that these practices modify the distribution of C functional groups of SOM. Fertilization practices were associated with increased O-alkyl groups. Tillage resulted in increases in the SOC consisted of aromatic and carbonyl groups. Crop rotations, especially legume-based rotations, were found to increase the proportion of aromatic groups. Although there are fewer publications on tillage and crop rotation than on fertilization practices, the distribution of C functional groups may be more influenced by crop rotation and tillage practices than fertilization management—and should be a focus of future research. [ABSTRACT FROM AUTHOR]

It was found by chromatography and 13C NMR spectroscopy that diethyl 2,3-diisobutyl succinate (DIBS), which is used as a stereoregulating electron donor in titanium–magnesium catalysts, exists as rac and meso stereoisomers. Their molecular structure was calculated using the DFT method. It was ascertained that mainly rac -DIBS is anchored to the surface of MgCl 2. Subsequent interaction between the MgCl 2 /DIBS sample and TiCl 4 leads to further removal of meso -DIBS. Titanium–magnesium catalysts of composition MgCl 2 /DIBS/TiCl 4 prepared by different procedures contain 85–91% rac -DIBS. The IR spectroscopy data on the stereoisomeric configuration of DIBS in MgCl 2 /DIBS samples and titanium–magnesium catalysts MgCl 2 /DIBS/TiCl 4 prepared by different procedures and the data on propylene polymerization over these catalysts are presented. [Display omitted] • Titanium-magnesium catalysts with diethyl 2,3-diisobutyl succinate have been studied • Mainly rac -stereoisomer (85–91%) is anchored to the surface of MgCl 2 in catalysts • Succinate is anchored preferentially to pentacoordinated Mg ions on MgCl 2 surface [ABSTRACT FROM AUTHOR]

Interactions between tephra deposits from volcanic eruptions and peatland carbon (C) dynamics are poorly understood despite the significant extent of peatlands influenced by tephra worldwide. Tephra falls can affect peat accumulation within a radius of at least 1,000 km. In Iceland, volcanic activity is amongst the highest in the world and it might even increase due to pressure release on subglacial volcanoes. A potent combination of sparse vegetation, low cohesion of Andosols, and frequent strong winds, facilitates the regular input of mineral aeolian material from eroded areas into peatlands in Iceland, in addition to tephra deposits. We present results of a study on the impact of a major tephra deposit, the Hekla 4 tephra, on C dynamics in Icelandic peatlands. We investigated three sites at differing distances from the active volcanic zones and major erosion areas in the interior of the country. A combination of variables was applied, including laboratory C mineralization at 5, 15 and 25°C and C structure obtained by solid‐state 13C NMR spectroscopy. Tephra deposits seem to affect C dynamics. Differences in C mineralization can only be partially explained by C structure. The C mineralization from soils with conspicuously similar C structure differs by a factor of up to 2.7. Temperature sensitivity of decomposition after the tephra deposition increases by a factor of up to 2.2. Changes in inorganic matter and the ratio of soil organic matter to soil organic carbon by a factor of up to 1.3 and 1.4, respectively, were also observed. [ABSTRACT FROM AUTHOR]

L-Ornithine-L-aspartate (LOLA), a crystalline salt, is used primarily in the management of hepatic encephalopathy. The degree to which it might penetrate the brain, and the effects it might have on metabolism in brain are poorly understood. Here, to investigate the effects of LOLA on brain energy metabolism we incubated brain cortical tissue slices from guinea pig (Cavea porcellus) with the constituent amino acids of LOLA, L-ornithine or L-aspartate, as well as LOLA, in the presence of [1-13C]D-glucose and [1,2-13C]acetate; these labelled substrates are useful indicators of brain metabolic activity. L-Ornithine produced significant "sedative" effects on brain slice metabolism, most likely via conversion of ornithine to GABA via the ornithine aminotransferase pathway, while L-aspartate showed concentration-dependent excitatory effects. The metabolic effects of LOLA reflected a mix of these two different processes and were concentration-dependent. We also investigated the effect of an intraperitoneal bolus injection of L-ornithine, L-aspartate or LOLA on levels of metabolites in kidney, liver and brain cortex and brain stem in mice (C57Bl6J) 1 h later. No significant changes in metabolite levels were seen following the bolus injection of L-aspartate, most likely due to rapid metabolism of aspartate before reaching the target tissue. Brain cortex glutamate was decreased by L-ornithine but no other brain effects were observed with any other compound. Kidney levels of aspartate were increased after injection of L-ornithine and LOLA which may be due to interference by ornithine with the kidney urea cycle. It is likely that without optimising chronic intravenous infusion, LOLA has minimal impact on healthy brain energy metabolism due to systemic clearance and the blood - brain barrier. [ABSTRACT FROM AUTHOR]

2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO)-catalytic oxidation was applied to a water-insoluble α-(1 → 3)-glucan in water at pH 10 and room temperature (∼24 °C), with solid NaOCl·5H 2 O as the primary oxidant. Oxidation with NaOCl at 15 mmol/g gave a water-soluble TEMPO-oxidized product at a mass recovery ratio of 97 %. The carboxy content of the TEMPO-oxidized product was 5.3 mmol/g, which corresponds to a degree of C6-oxidation (DO) of 93 %. A new water-soluble α-(1 → 3)-polyglucuronic acid with a nearly homogeneous chemical structure was therefore quantitatively obtained. X-ray diffraction and solid-state 13C NMR spectroscopic analyses showed that the original α-(1 → 3)-glucan and its TEMPO-oxidized product with a carboxy content of 5.3 mmol/g had crystalline structures, whereas the oxidized products with DOs of 50 % and 66 % had almost disordered structures. The carboxy groups in the oxidized products were regioselectively methyl esterified with trimethylsilyl diazomethane, and analyzed by using size-exclusion chromatography with multi-angle laser-light scattering and refractive index detections. The results show that the original α-(1 → 3)-glucan and its oxidized products with DOs of 50 %, 66 %, and 93 % had weight-average degrees of polymerization of 671, 288, 54, and 45, respectively. Substantial depolymerization of the α-(1 → 3)-glucan molecules therefore occurred during catalytic oxidation, irrespective of the oxidation pH. [Display omitted] [ABSTRACT FROM AUTHOR]

ABSTRACT: Dissolution dynamic nuclear polarization (dDNP) provides strikingly increased sensitivity for detecting NMR-receptive nuclei in molecules that are substrates of enzymes and membrane transport proteins. This paves the way for studying the kinetics of many such catalyzed reactions on previously unattainable short time scales (seconds). Remarkably, this can also be carried out not only in vitro, but in whole cells, tissues, and even in vivo. The information obtained from the emergent NMR time courses is a sequence of spectral-peak intensities (integrals) as a function of time. Typically, for 13C NMR studies, these consist of a series of spectra acquired every 1 s for a total time span of ∼3 min.The time evolution of an excited spin system in molecules that undergo chemical transformation via enzyme-catalyzed reactions is described by the Bloch-McConnell differential rate equations. For these equations, the estimation of the values of apparent first order rate constants, or enzyme kinetic parameters like the maximal velocity (Vmax), Michaelis constant (Km), and dissociation inhibition constant (Ki), is handled by nonlinear regression analysis. A twist (compared with previous methods) lies in the fact that modern software like Mathematica can perform regression analysis without the need for an analytical solution of these equations to fit to the time course data. Regression algorithms exist that can directly use the numerical solution of the differential equations in the fitting process. Therefore, the main challenge for data analysis now resides in formulating the correct set of differential equations that emulate the system being studied. It is this important aspect of dDNP enzyme-kinetic analysis that we address here.We show that formulating the array of simultaneous differential rate equations follows the same approach as more conventional chemical kinetics. Namely, this requires rigorous application of two key principles: the principle of conservation of mass; and the principle of balance of physical dimensions (dimensional veracity) on either side of the equal sign in all equations in a simultaneous array. This mathematical synthesis requires extra-careful thought when formulating equations that describe enzyme-catalyzed reactions that are probed by dDNP; potential pitfalls are discussed as well.

An application of solid 13C nuclear magnetic resonance (NMR) spectroscopy for the determination of macronutrients, total polyphenols content, antioxidant activity, N C S elements, and pH in commercially available bee pollens is reported herein. Solid-state 13C NMR spectra were recorded for homogenized pollen granules without chemical treatment or dissolution of samples. By combining spectral data with the results of reference analyses, partial least squares models were constructed and validated separately for each of the studied parameters. To characterize and compare the models’ quality, the relative standard errors of prediction (RSEP) were calculated for calibration and validation sets. In the case of the analysis of protein, fat and reducing sugars, these errors were in the 1.8–2.5% range. Modeling the elemental composition of bee pollen on the basis of 13C NMR spectra resulted in RSEPcal/RSEPval values of 0.3/0.6% for the sum of NHCS elements, 0.3/0.4% for C, 1.8/1.9% for N, and 4.2/6.1% for S quantification. Analyses of total phenolics and ABTS antioxidant activity resulted in RSEP values in the 2.7–3.5% and 2.8–3.8% ranges, respectively, whereas they were 1.4–2.1% for pH. The obtained results demonstrate the usefulness of 13C solid-state NMR spectroscopy for direct determination of various important physiochemical parameters of bee pollen.

The conceptual possibility to synthesize bacterial cellulose nitrates with the use of commercial mixed acid was demonstrated. The initial bacterial cellulose was produced by the Medusomyces gisevii Sa-12 symbiotic culture in a synthetic nutrient broth in a Binder constant climate chamber. The resulting bacterial cellulose nitrate sample had 11.45% nitrogen content, 1900 cP viscosity, 15.8% solubility in ethanol—diethyl ether mixture, and 0.10% ash content. An extremely high sample viscosity (organogelation) in a ∼2% solution in acetone was observed. [ABSTRACT FROM AUTHOR]

With the help of chemical shifts computed with density functional theory (DFT), it is demonstrated that the reported experimental 13C NMR data of acremolin C are incompatible with the claimed structure of an N2,3-ethenoguanine with an isopropyl group at C-1'. An alternative structure, which is in agreement with both experimental and computed data, presents an isopropyl group at the C-2' position of an N2,3-ethenoguanine and leads to the conclusion that acremolin C is identical with acremolin B. [ABSTRACT FROM AUTHOR]

Thermal analysis techniques have been widely used to characterize natural organic matter; in particular, thermal oxidation has been used to examine soil and sediment organic matter. However, few studies have characterized natural organic matter (NOM) by using slow thermal degradation under a N2 atmosphere. 13C nuclear magnetic resonance (NMR) spectroscopy, UV-Vis spectroscopy, and three-dimensional excitation and emission matrix (EEM) fluorescence spectroscopy were used to characterize aquatic plant biomass for the detailed interpretation of the structures of organic carbon during slow pyrolysis. There was a significant linear correlation between the absorption of heat (99–110 °C) and the loss of mass (110–160 °C) (r2 = 0.507, p = 0.01), which indicates that the initial slight loss in mass of the plant materials was due to the loss of less thermally stable components. The release of heat (277–311 °C) and the ratio of the specific absorbances at 253 and 203 nm (A253/203) were also correlated (r2 = 0.388, p = 0.008), which suggests that the release of plant biomass upon heating was associated with the proportion of substituent groups on aromatic rings and that the release of heat increased with the amount of substitution. The coefficient of determination (r2) between fulvic acid-like fluorescence peaks and the loss of mass (230–340 °C) was 0.236 (p = 0.048). This result indicates that the loss of mass in the plant material samples was related to fulvic acid-like substances. More specifically, the reason for this result was the splitting of some aromatic functional groups, such as ether bonds, carbonyl groups, and oxygen heterocycles. In conclusion, these results suggest that the developed correlations between slow pyrolysis characteristics and organic carbon structures contribute to the investigation of the inner chemical structures of natural organic matter. [ABSTRACT FROM AUTHOR]

Results of the study of humus composition in about 200 modern soils of different genesis and more than 100 buried Pleistocene and Holocene paleosols have been collected and analyzed. The content of the nonhydrolyzable part of soil organic matter (NH OM) in the paleosols is comparable with that in the modern soils (50 ± 15% and 54 ± 21%, respectively). Thus, NH OM does not accumulate in the buried soils during their diagenesis and is not the inert fraction of the soil organic matter (SOM). The NH OM content in the natural organomineral soil complexes–clay fractions of the soils—is lower than that in the whole soil mass. Data on the solid-state 13C NMR spectroscopy of the whole soil samples and the NH OM indicate that the latter are enriched in O-alkyls, including C of acetal groups. The whole soil mass is richer in C of aromatic structures and carboxyl groups. The degree of organic matter humification estimated from the alkyls/O-alkyls ratio for the NH OM is considerably lower than that for the whole SOM. The existence of negative correlation between the contents of NH OM and humic acids in the modern soils (R = –0.86) and in the buried paleosols (R = –0.83) has been shown. The NH OM content in the clay fraction in comparison with the whole soil mass is lower (36 ± 21% and 60 ± 15%, respectively). This reflects the accumulation of weakly decomposed plant residues in this part of the SOM. It is argued that the NH OM is heterogeneous and includes at least two groups of substances: clay-bound organic matter of organomineral complexes (nonhydrolyzable because of strong chemical bonds) and weakly decomposed plant residues resistant to acid and alkaline hydrolysis. The absence of definite relationships between the contents of NH OM and fulvic acids indicates that genetic links between the NH OM and humic acids are stronger than those between the NH OM and fulvic acids. 13C NMR spectroscopy of kerogen from the Carboniferous shale attests to the principal difference between the NH OM of soils and kerogen, in which C of alkyl groups predominates. [ABSTRACT FROM AUTHOR]

Abstract Different types of crop straw and their derived biochars and compost treatments have huge potential for carbon sequestration to sustain crop productivity. In this study, cotton straw (straw), cotton straw-derived compost (compost) and cotton straw-derived biochar (biochar) with equivalent carbon (C) content were added to soil and incubated for 30 and 180 days. The C sequestration potential of these organic materials was determined by 13C isotope trace method. The structural characteristic of soil organic carbon (SOC) was analyzed by solid-state 13C NMR spectroscopy. The SOC concentration was measured by wet oxidation and dry combustion methods. The results showed that 50.84%, 41.03% and 38.55% of native SOC were replaced by biochar, compost, and straw, respectively. The carbohydrate C and methoxyl C contents were significantly higher in straw and biochar amendments respectively, while phenolic C and alkyl C were high in compost amendment and a higher proportion of aryl C occurred in biochar treatment. These findings revealed that straw material was easier to be decomposed, but compost and biochar showing better stability. Graphical abstract Unlabelled Image Highlights • Biochar, compost, and straw derived SOC contents were 50.84%, 41.03%, and 38.55%. • The increase of SOC was maximum in the biochar amendment. • Straw and biochar treatments had high carbohydrate C and methoxyl C contents. • Phenolic C and alkyl C contents were predominant in compost treatment. • SOC in biochar treated soil was more stable than straw and compost treatments. [ABSTRACT FROM AUTHOR]

Abstract In a recent study, we have shown by NMR spectrocopy that monoalkylcarbonates are formed in substantial amounts in aqueous solutions of the tertiary alkanolamine methyldiethanolamine (MDEA) upon loading with carbon dioxide ( CO 2 ). These species had been overlooked by most authors previously. In the present work, this study was extended to the primary alkanolamine monoethanolamine (MEA). Also here monoalkylcarbonates were found, but only at CO 2 loadings above 0.5 mol CO 2 per mol MEA. Both the amine and its carbamate form monoalkylcarbonates. The concentration of the monoalkylcarbonates was determined with 13C NMR spectroscopy in a wide range of CO 2 loadings, MEA concentrations, and temperatures. Based on this comprehensive data the chemical equilibirium constants of the formation of the monoalkylcarbonates were determined. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Floodplain soils are important reservoirs of organic carbon (OC) in the terrestrial carbon cycle. Few rivers and floodplains in the world and particularly in central Europe are in a natural state. They are regulated, stabilised from erosion behind artificial levees, drained and used for agriculture. Fluvisols store high amounts of OC from the topsoil to the subsoil, but little is known about the soil organic matter (SOM) quality and its vulnerability to decomposition. In this study, two regulated floodplains originating from different parent materials under grassland use in Southern Germany (Alpine Foreland and the Bavarian Forest) were sampled and analysed for the quantity and quality of inherent SOM in the topsoil and two subsoil levels. We characterised bulk soil (pH, texture, inorganic carbon and total nitrogen) and applied a combined density and size fractionation scheme to obtain six fractions. The chemical composition of the fractions was further determined using solid-state 13C NMR spectroscopy (SOM composition), as well as X-ray diffraction (clay mineralogy) and N 2 -BET (specific surface area (SSA)). Contributions of light fractions and especially of occluded particulate organic matter (oPOM fine) to the total OC were remarkably high in the subsoils. Organo-mineral associations (OMF fine) highly contributed to total OC at both sites but only in the topsoils. The highest OC concentrations of OMF fine were found in calcareous parent material, which shows that polyvalent cations promote OC storage. However, the inter-site as well as intra-site heterogeneity of oPOM fine and OMF fine OC contribution was highly variable. In the Bavarian Forest, oPOM fine was enriched in lipids in the subsoil. This was most probably due to a limited supply of oxygen in the aggregates through fluctuating groundwater levels that retarded decomposition and selectively preserved aliphatic compounds. In the Alpine Foreland, soil biota had mixed fresh SOM into the subsoil. There, oPOM fine contained all the functional C-groups, particularly carbohydrates. A changing global climate jeopardises OC reservoirs in floodplains, due to increased flooding and associated river bank erosion. Such disturbances not only cause losses of productive land but also release OC stored in light fractions that could be oxidised to CO 2 , depending on its chemical composition, thus adding to global warming. Graphical abstract Unlabelled Image Highlights • Floodplain subsoils store high amounts of organic carbon in light fractions. • Strongly decomposed, lipid-rich light fractions occur in less-aerated subsoils. • Weakly decomposed light fractions in well-aerated soils with high bioturbation • Polyvalent cations promote mineral-bound OC storage in calcareous soils. [ABSTRACT FROM AUTHOR]

Abstract In acidic soils heterotrophic nitrification is considered to be an important NO 3 − production process. Previous studies have demonstrated that the content of soil C and soil C:N ratio was positively correlated with heterotrophic nitrification. However, relatively high heterotrophic nitrification rates also observed in cultivated black soils, with relatively low soil organic C content and soil C:N ratio compared to forest soils. To obtain a mechanistic understanding of heterotrophic nitrification the simultaneously occurring gross N transformations were quantified in five cultivated soils (SC) and six forest soils (SF) in subtropical region, ten cultivated soils (TC) and seven forest soils (TF) in temperate region subsequently analysed with respect to the soil physicochemical properties (pH, C:N ratio, SOC, TN), the chemical compositions of soil organic C (recalcitrant and labile organic C) and microbial communities (abundance of fungi, bacteria, amoA gene of AOB and AOA). The results showed that a significantly higher heterotrophic nitrification rate was observed in TC (0.52 mg N kg−1 d−1) compared to the other soils. The total content of soil C and soil C:N ratio could not explain the occurrence of heterotrophic nitrification but recalcitrant C fractions of carbonyl C and aromatic C, and the ratio of recalcitrant C to labile C (R:L ratio) was significantly positively correlated with heterotrophic nitrification rates (P < 0.01). This was further confirmed by structural equation modeling (SEM) that the R:L ratio was the most important indicator, suggesting that chemical composition of SOC is likely to be key to explain and predict heterotrophic nitrification rates across a large range of soils including soils high in black carbon such as chernozems, old grassland soils and/or anthropogenic soils such as anthrosols (Terra preta). In addition, heterotrophic nitrification rates were significantly positively correlated with fungal gene copy numbers (P < 0.05), providing a strong indication that fungi might be the predominant organisms carrying out heterotrophic nitrification. Highlights • SOC content and C/N are not enough to explain occurrence of heterotrophic nitrification. • Heterotrophic nitrification rates are associated with the composition of SOC. • Soil recalcitrant C plays an important role in regulating heterotrophic nitrification. [ABSTRACT FROM AUTHOR]

Headed for developing minimalistic strategies to produce graphene@metal hybrids for electronics on a larger scale, we discovered that graphene oxide (GO)-metal oxide (MO) hybrids are formed spontaneously in water at room temperature in the presence of nothing else than graphene oxide itself and metal ions. Our observations show metal oxide nanoparticles decorating the surface of graphene oxide with particle diameter in the range of 10–40 nm after only 1 h of mixing. Their load ranged from 0.2% to 6.3% depending on the nature of the selected metal. To show the generality of the reactivity of GO with different ions in standard conditions, we prepared common hybrids with GO and tin, iron, zinc, aluminum and magnesium. By means of carbon-13 solid-state nuclear magnetic resonance using magic angle spinning, we have found that graphene oxide is also moderately reduced at the same time. Our method is powerful and unique because it avoids the use of chemicals and heat to promote the coprecipitation and the reduction of GO. This advantage allows synthesizing GO@MO hybrids with higher structural integrity and purity with a tunable level of oxidization, in a faster and greener way.