On the components of soil humic acids VII

The writers already made it clear that by active alumina the humic acids of A- and B-types contained in various soils could be separated into 3 or 4 components (1). And moreover, absorption spectra (2), nitrogen constituents (3) and colloidal nature (4) of them were studied for the purpose of examining their qualities.     

Analysis of polynuclear aromatic and aliphatic components in soil humic acids using ruthenium tetroxide oxidation

Although condensed aromatic components are considered to be one of the major structural units of soil humic acids (HAs) and to be responsible for the dark colour of HAs, their amount and composition remain largely unknown. In ruthenium tetroxide oxidation (RTO), condensed aromatic components are detectable as their degradation products, mainly benzenepolycarboxylic acids (BPCAs). We applied this technique to soil HAs with various degrees of humification (darkening). The yields of water‐ and dichloromethane‐soluble products from HAs upon RTO after methylation ranged from 210 to 430 mg g⁻¹ and 10–40 mg g⁻¹, respectively. Eight kinds of BPCAs with two to six carboxyl groups, and seven kinds of BPCAs with additional side chains (tentative assignment) were obtained as methylated counterparts. The yield of each BPCA and the sum of the yields of BPCAs (12–85 mg g⁻¹ HAs) increased with increasing degree of humification and aromatic C content. The compositions of BPCAs indicated that the degree of condensation was greater in the HAs with greater degrees of humification. The sum of the yields of aliphatic compounds ranged from 0.1 to 6.5 mg g⁻¹, and decreased with increasing degree of humification. The C₁₂ to C₃₀ monocarboxylic acid methyl esters accounted for > 56% of the aliphatic compounds assigned, which may be present mainly as end alkyl groups in the HA molecules. We also obtained the methylated counterparts of C₁₄ to C₂₄ dicarboxylic acids; these were possibly derived from polymethylene bridges between adjacent aromatic rings.     

Selective digestion of the peptide and polysaccharide components of synthetic humic acids by the humivorous larva of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

In order to identify the potential nutrient and energy sources of humivorous beetle larvae, we carried out feeding trials with soil supplemented with specifically ¹⁴C-labeled model humic acids synthesized by peroxidase-initiated radical polymerization, using the cetoniid beetle Pachnoda ephippiata (Coleoptera: Scarabaeidae) as a model organism. Ingestion of soil by the larvae significantly increased the mineralization of humic acids labeled in their peptide (HA-*peptide) or polysaccharide components (HA-*peptidoglycan and HA-*chitin), whereas the mineralization of humic acids labeled in the aromatic components (HA-*catechol) did not increase significantly. Mineralization was accompanied by a reduction of residual radiolabel in the acid-soluble fraction and an increase in the humic acid and humin fractions of the fecal pellets. During the gut passage, the residual label in peptide or polysaccharide components was transformed into acid-soluble products, especially in the alkaline midgut. High-performance gel-permeation chromatography demonstrated that the changes in solubility were accompanied by large changes in the molecular weight of the residual material. The amount of radiolabel derived from the peptide and polysaccharide components recovered from the larval body and hemolymph was significantly higher than that derived from the aromatic component, which supports the hypothesis that humivorous beetle larvae selectively digest the peptide and polysaccharide components of humic substances, whereas the aromatic components of humic substances are not an important source of nutrients and energy. This is also the first experimental evidence that also chitin and peptidoglycan, the major structural polymers in fungal and bacterial biomass, can be protected from microbial degradation in soil by a copolymerization with phenols and might contribute substantially to the refractory nitrogen pool in soil organic matter.     

On the components of soil humic acids (part 9)

The carbohydrates in soil organic matter seem to be derived from undecomposed or partially decomposed plant and microbial residues, In soil, these carbohydrates exist chiefly in such from as polysaccharide hemicellulose, and their polyuronide has been the chief object of investigation^1)-3). In various soil, the polyuronide is found in a large quantity in fulvic fraction of soil organic matter and has been considered as important in connection with the physical structure of soil^4),5). According to Lynch ⁵⁾, the carbohydrate content of humic acid is markedly smaller than that of fulvic acid. His work also indicates that a' considerable change is noted in the content and composition of the carbohydrate in humic acid because of the addition of some organic substances to the soils, or of the cultivation of virgin soils. Further, some investigators⁷⁾ believe that uronic acid is introduced into the aromatic structure of the humic acid by changing into pentose and furan. Accordingly, it seems that the role of carbohydrate in the formation of soil humic acid should not be overlooked.     

Volatile components in crabmeats of Charybdis feriatus

The volatile components of different meats (legs with claws, body, and carapace) of a popularly consumed edible crab in Asia, Charybdis feriatus, were investigated. Samples were extracted by simultaneous steam distillation-solvent extraction and analyzed by gas chromatography/mass spectrometry. Among 177 compounds detected, 130 were positively identified. Seventy-six compounds were previously reported in other crab species. A greater number of naphthalenes were detected in this crab compared with other crabs in the literature. Aromatic compounds, alcohols, and sulfur-containing compounds were the three predominant groups with >15 components. Carapace tissue contained a greater number of volatile components in each group, except for sulfur-containing compounds. Most of the common components in the leg meat and the body meat were found at similar levels (p > 0.05). Carapace tissue generally had the highest quantity of common components among the meats. The higher levels of volatile components present in the carapace tissue might account for its stronger flavor compared with the other meats. Furthermore, the higher number of aldehydes and lower number of sulfur-containing compounds detected in the carapace meat might contribute to its unique flavor.     

Comparison of humic acids derived from city refuse with more developed humic acids

Abstract

The humic acids (HA) from composted and uncomposted city refuse (CR) were characterized by degradative (oxidation with persulphate and permanganate) and non-degradative techniques (FT-IR and ¹³C-NMR) in order to analyze the effect of the composting process on these HA. They were also compared with commercial HA extracted from leonardite. The carboxyl and carbonyl group content of the HA from CR increased slightly during composting. Since the HA from the composted CR showed a lower N and H content, the FT-IR spectra showed a lower intensity in the bands corresponding to peptides and carbohydrates. Differences were revealed when the HA from both CR were compared with those from leonardite which showed a much lower N and H content and a less aliphatic character. The percentage of degraded products by persulphate was higher for the HA from uncomposted CR. For the HA from both CR the major components among the oxidation products were dicarboxylic acids and normal fatty acids. In the leonardite HA, the major components consisted of benzene polycarboxylic acids. ¹³C-NMR revealed an attenuation of the aliphatic character of the HA from CR with composting.     

Fate of humic acids isolated from natural humic substances

Composition of humic acids (HA) is a function of plant-derived inputs, degradation processes regulated by microorganisms, organo-mineral interactions and age. Characterization of different origin humic substances is important for evaluation of their contribution to stabile and labile carbon pool in the environment. The relative abundance of chemical components in HA isolated from soils, compost, commercial lignohumates, alginite, acadiane and lignite was studied with aim to quantify content of important biomarkers such as amino acid, lipids and polyphenols. HA were considered as a heterogeneous complex and high concentration of peptides, polyphenols and lipids was determined in acadian-HA to compare with soil-HA. Compost-HA contained much more amino acids to compare with soil-HA samples. Alginite-HA and lignite-HA were similar in biomarkers content to soil-HA. Fourier transform infrared spectroscopy confirmed that chemical composition and functional groups content differs with the origin, humification degree and the age of studied samples. Soil-HA are typically composed of a variety of ?OH, COOH?, C–O, C–H₂, (aliphatic and aromatic) groups, quinines, lignin fragments, polysaccharide, monosaccharide and proteins fragments, which are linked together by ?O?, ?NH?, ?H=, >C=O, metal ions and –S? groups. ¹³C NMR spectroscopy showed that aromatic carbon content was the highest in lignite-HA and soil-HA.     

Sequential exhaustive extraction of a Mollisol soil, and characterizations of humic components, including humin, by solid and solution state NMR

A comprehensive sequential extraction procedure was applied to isolate soil organic components using aqueous solvents at different pH values, base plus urea (base‐urea), and finally dimethylsulfoxide (DMSO) plus concentrated H₂SO₄ (DMSO‐acid) for the humin‐enriched clay separates. The extracts from base‐urea and DMSO‐acid would be regarded as ‘humin’ in the classical definitions. The fractions isolated from aqueous base, base‐urea and DMSO‐acid were characterized by solid and solution state NMR spectroscopy. The base‐urea solvent system isolated ca. 10% (by mass) additional humic substances. The combined base‐urea and DMSO‐acid solvents isolated ca. 93% of total organic carbon from the humin‐enriched fine clay fraction (<2 μm). Characterization of the humic fractions by solid‐state NMR spectroscopy showed that oxidized char materials were concentrated in humic acids isolated at pH 7, and in the base‐urea extract. Lignin‐derived materials were in considerable abundance in the humic acids isolated at pH 12.6. Only very small amounts of char‐derived structures were contained in the fulvic acids and fulvic acids‐like material isolated from the base‐urea solvent. After extraction with base‐urea, the 0.5 m NaOH extract from the humin‐enriched clay was predominantly composed of aliphatic hydrocarbon groups, and with lesser amounts of aromatic carbon (probably including some char material), and carbohydrates and peptides. From the combination of solid and solution‐state NMR spectroscopy, it is clear that the major components of humin materials, from the DMSO‐acid solvent, after the exhaustive extraction sequence, were composed of microbial and plant derived components, mainly long‐chain aliphatic species (including fatty acids/ester, waxes, lipids and cuticular material), carbohydrate, peptides/proteins, lignin derivatives, lipoprotein and peptidoglycan (major structural components in bacteria cell walls). Black carbon or char materials were enriched in humic acids isolated at pH 7 and humic acids‐like material isolated in the base‐urea medium, indicating that urea can liberate char‐derived material hydrogen bonded or trapped within the humin matrix.     

冬小麦产量结构要素预报方法

为优选出最佳的冬小麦产量结构要素预报方法,该研究选择冬小麦成穗数、穗粒数及千粒质量为预报目标,综合考虑种植品种、密度及地区因子,并对气象因子进行膨化统计,得到126个自变量因子,分别采用多元线性回归、因子分析-线性回归及BP(Back Propagation)神经网络等3种方法进行建模分析。结果表明,直接采用各因子进行回归分析无法解决不同自变量间存在的多重共线性问题,而因子分析虽然消除了不同自变量间的多重共线性,但采用因子优化后的10个综合因子分别对3个产量结构要素进行线性回归,得到的预报模型决定系数(R^2)均不足0.500。运用BP神经网络对冬小麦3个产量结构要素进行预报,结果发现,当输入层为126、隐含层为16、输出层为3时,BP神经网络结构最佳,在此结构下,模型的决定系数为0.644,明显优于多元线性回归及因子分析-线性回归法。同时,基于BP神经网络模型对冬小麦产量结构要素的预报精度平均达85.3%。因此,推荐采用BP神经网络模型对冬小麦产量结构要素进行预报。     

Molecular characteristics of humic acids extracted from compost at increasing maturity stages

The molecular composition of humic acids (HA) extracted from compost at increasing maturity stages was determined by off-line TMAH-thermochemolysis-GC-MS, in combination with solid-state nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies. While spectroscopy measurements followed the bulk changes, thermochemolysis provided a detailed molecular variation of HA composition. Both thermochemolysis and spectroscopy indicated that polysaccharides, alkyl, cyclic, and aromatic compounds were the predominant components of HA, the stable fraction of compost. NMR dipolar dephasing (DD) experiments confirmed that HA extracts contained lignin in lower amount than its oxidized degradation products. The progressive compost maturity was reflected in HA extracts by a decrease of carbohydrate content and a selective preservation of hydrophobic alkyl molecules, such as medium- and long-chain fatty acids, aliphatic alcohols, linear hydrocarbons, and plant polyester derivatives, like long-chain alkyl dicarboxylic acids, and ω-hydroxyacids. Spectroscopy results showed a concomitant entrapment in HA of biolabile compounds, such as peptidic moieties. The wide range of identified lipid components and plant biomarkers may represent useful tools to trace origin, quality, and transformation of amended compost in soil ecosystems.     

新增耕地土壤物质组分特征及其培肥研究

为了解土地整理新增耕地土壤物质组成及土壤肥力状况,对新增耕地土壤矿物成分、化学成分、污染元素和土壤化学性质进行了分析,分析结果将为新增耕地土壤培肥提供依据.实验结果表明新增耕地土壤养分的有效氮、磷、钾及有机质比较缺乏,必须对其进行培肥.利用固体废物对新增耕地土壤进行培肥,其成本低,工艺简单,培肥效果良好.     

Analysis of the main components of the aguamiel produced by the maguey-pulquero (Agave mapisaga) throughout the harvest period

The main characteristics of the aguamiel (maguey-pulquero sap) during the harvest period of the Agave mapisaga plants were assessed to establish its stability through time and the industrial potential of its components. Only minor differences in aguamiel composition were detected among samples collected at different time points of the harvest period. The aguamiel analyzed contained 11.5 wt % of dry matter, which was composed mainly of sugars (75 wt %). Among these sugars, 10 wt % were fructo-oligosaccharides (FOS), which are known to be important in the food industry for their prebiotic properties. Other components include 0.3 wt % of free amino acids (with most essential amino acids and four neurotransmitters: GABA, GLY, GLX, and ASX), 3 wt % of proteins, and 3 wt % of ashes.     

Fractionation of humic acids upon adsorption on montmorillonite and palygorskite

The adsorption of three humic acid (HA) preparations by clays—montmorillonite (Wyoming, USA) and palygorskite (Kolomenskoe district, Moscow oblast)—has been studied. The HA preparations were isolated from samples of the humus-accumulative horizons of a leached chernozem (Voronezh) and a chestnut soil (Volgograd), and a commercial preparation of sodium humate (Aldrich) was also used. The solid-state ¹³C NMR spectroscopy and IR spectroscopy revealed the selective adsorption of structural HA fragments (alkyls, O-alkyls (carbohydrates), and acetal groups) on these minerals. As a result, the aromaticity of the organic matter (OM) in the organic-mineral complexes (OMCs) and the degree of its humification have been found to be lower compared to the original HA preparations. The fractionation of HAs is controlled by the properties of the mineral surfaces. The predominant enrichment of OMCs with alkyls has been observed for montmorillonite, as well as an enrichment with O-alkyls (carbohydrates) for palygorskite. A decrease in the C : N ratio has been noted in the elemental composition of the OM in complexes, which reflected its more aromatic nature and (or) predominant sorption of N-containing structural components of HA molecules. The adsorption of HA preparations by montmorillonite predominantly occurs on the external surface of mineral particles, and the interaction of nonpolar alkyl groups of HAs with this mineral belongs to weak (van der Waals, hydrophobic) interactions. The adsorption of HA preparations by palygorskite is at least partly of chemical nature: Si-OH groups of minerals are involved in the adsorption process. The formation of strong bonds between the OM and palygorskite explains the long-term (over 300 million years) retention of fossil fulvate-type OM in its complex with palygorskite, which we revealed previously.     

Effect of soil components on the surfactant-enhanced soil sorption of PAHs

Purpose  

The use of cationic surfactants was proposed to enhance the soil retention of hydrophobic organic contaminants (HOCs). However, due to the complexity of soil composition, the effect of cationic surfactants on the soil sorption of HOCs was limited to a qualitative understanding. To gain further insight into the mechanism of the surfactant and predict its efficiency, a comparative study on the HOCs sorption capacities of the surfactants sorbed on pure typical soil components was investigated.     

Some unusual minor volatile components of tomato

The identities and possible origins of three minor unusual volatile components of tomato are discussed. These are pentyl nitrate, the first identification of a volatile alkyl nitrate in a fresh vegetable or fruit; 5-ethyl-2(5H)-furanone, which, besides its presence in tomato, was found to be a major autoxidation product of pure (Z)-3-hexenal; and 5-ethylcyclopentene-1-carbaldehyde, a likely unusual linolenic acid oxidation product.     

Solid-phase microextraction of volatile components from natural grassland plants

The volatile components from nine plants growing on natural grasslands in Auvergne, central France, selected for the broad qualitative and quantitative diversity of their terpenoid fractions, were analyzed by high-resolution gas-phase chromatography and mass spectrometry (HRGC-MS) after static headspace solid-phase microextraction (SHS-SPME). SHS-SPME allowed all the plant material to be analyzed under the same conditions despite its wide-ranging composition. This is not always possible with other extraction methods. Using an apolar poly(dimethylsiloxane) (PDMS) phase, numerous terpenoid hydrocarbons, together with alcohols, cyclic ethers, and esters, were extracted. Its ease of use and the high resolution of the chromatographic profiles obtained make SHS-SPME well suited to the rapid characterization of the main components of the volatile fraction of plants. Of the nine plants studied, four (Meum athamanticum, Pimpinella saxifraga, Achillea millefolium, and Thymus pulegioides) exhaled more than 60 different volatile components. Certain terpenes present in large amounts in these plants might help link dairy products to grazing pasture, thus improving food traceability.     

可矿化氮与各有机氮组分的关系

用通气培养法测定了6种肥力36个不同土层土壤的可矿化氮,用Bremner法测定了各有机氮组分,采用相关分析、多元回归分析和通径分析确定可矿化氮与各有机氮组分之间的关系。结果表明,酸解氮与可矿化氮有较密切的正相关关系。在酸解氮中,酸解未知态氮与可矿化氮不相关;而氨基酸态氮、铵态氮、氨基糖态氮的多少与可矿化氮相互平行,相关系数均较高,似乎对可矿化氮皆有贡献。但多元回归分析表明,氨基糖态氮在方程中不显著;逐步回归分析更肯定了这一结果。通径分析进一步表明氨基酸态氮和铵态氮对可矿化氮有很高的通径系数,表明了它们有着直接重大贡献,而氨基糖态氮直接通径系数甚低。这些结果说明,可矿化氮主要来自酸解氮,特别是氨基酸态氮和铵态氮,后两者是其产生的主要来源。     

煎炸油中产生的极性成分对食品微观结构和质构的影响

研究了煎炸油中产生的极性成分对食品微观结构和质构的影响。用硅胶柱色谱和高效体积排阻色谱测定了极性成分和聚合物含量变化，油炸食品穿孔力和微观结构的变化分别用质构仪和显微镜进行测定和观察。结果表明随着油炸时间延长，极性成分、聚合物含量呈线性增加且二者间也呈线性关系,油炸食品的微观结构越来越差,食品穿孔力虽没有明显变化，但其剪切系数(Kp)有增加而压缩系数(Ka)有减小的趋势。油脂中的极性成分严重影响了食品的微观结构，也在一定程度上影响了食品的Ka、Kp值，但还不能完全通过Ka、Kp的变化来表示油品质对食品质构的影响。     

Rapid quantification of humic components in concentrated humate fertilizer solutions by FTIR spectroscopy

Journal of Soils and Sediments - The use of humic substances is under thorough discussion of state-of-the-art agricultural science. They are marketed mostly as concentrated aqueous solutions of...     

Studies on the colour of humic acids

Based on their solubility, humus has been often divided into three fractions, i.e. fulvic acids, humic acids and humins. On the other hand, it seems to be generally accepted that humus can be divided into two groups (1) (2), non-humic substances and humic substances. The term humic substances (3) is used as a generic expression to describe the dark coloured, amorphous material in humus, or any of its above-mentioned fractions.