Chemical Structure Of Humic Acids Research Articles

Characterization of humic substances in waters and their therapeutic applications – a review

Aim: In this review, the authors characterise bioactive ingredients of humic waters, the chemical structure of humic acids and their properties, methods of their analysis and isolation. The aim of the study is also to review the application of humic waters and humic acids in different fields such as medicine and balneology. Materials and Methods: A literature review was done based on the available PubMed bibliographic database from 1994-2023. Articles in Polish and English were included. During the search the keywords such as humic waters, humic acids, peloids, balneotherapy and balneology were used. The authors also used other sources for the search, such as books and internet websites. Conclusions: Humic acids have a very high sorption capacity and a variety of biological properties including anti-inflammatory, antioxidant, antibacterial, antiviral, which can be successfully applied in different fields of medicine: dermatology, gastrology, diabetology and balneotherapy. The multitude of biological properties of humic waters and humic substances raises the question of whether or not they should be considered natural medicinal resources.

Application of EPR Spectroscopy in Studies of Soils from Destroyed Forests

The presented results show that significant changes have taken place in the structure of the humic acids in the soils affected by forest destruction. Regardless of the cause of forest removal: clear-cutting, a wildfire or a windstorm, its effect on soil humic acids was the same. The elemental analysis and the spectroscopic data (UV–Vis, EPR) indicate a higher content of aliphatic moieties and hence a lower degree of humification (higher parameter g of the radicals) of the organic matter extracted from the affected plots in comparison with the reference ones. Due to the slowing down of the humification processes, the soil organic matter extracted from the spruce forest on the disturbed plots is not as stable as the one taken from the reference plots. The results prove that semiquinone radicals present in humic acids are suitable indicators for tracking changes in the humified matter in the organic and mineral layers of forest soil under different management regimes in disturbed areas. Principally, the EPR method is an appropriate instrument which, through the detailed quantitative and qualitative determination of semiquinone radicals, makes it possible to track changes in the inner chemical structure of humic acids.

Comparison of Chemical Structure of Alginite Humic Acids Isolated with Two Different Procedures with Soil Humic Acids

Abstract The different origin of alginite and soil organic matter may be the reason of differences in their humic acids (HA) chemical structure. One of the aims of this article is to compare the chemical composition of alginite HA and HA isolated from different soil types. Another aim of this article is to compare the chemical structure of humic acids of alginite isolated with two different procedures: modified IHSS (International Humic Substances Society) method and simplified extraction method. The modified IHSS method was applied for the isolation of alginite and soil HA. To obtain sufficient amount of alginate HA for biological experiments, simplified extraction method suited for large volumes of HA was applied. The differences in elemental analysis and ash proportion in HA extracted by modified IHSS method (C = 35.4, H = 43 atomic%, ash content = 0.08%) and simplified extraction method (C = 31, H = 31 atomic%, ash content = 7.42%) can be caused by different concentration of extraction solution and also differences in purification of HA. The differences in chemical structure between alginate HA and HA isolated from different soil types according to the data of elemental analysis (C content of alginite HA = 35.4 atomic%, C content in soils HA = 38.2‒49.1 atomic%) and 13C nuclear magnetic resonance (NMR) spectra (degree of aromaticity of alginite HA = 24.4% and soil HA= 35.9‒53%) were found. Results of 13C NMR show that the content of aromatic carbon was decreasing in the following order: Haplic Chernozem HA > Andic Cambisol HA > Haplic Cambisol HA > alginite HA. Based on the obtained results, it can be concluded that the differences in the chemical structure of alginite and soil HA can be explained by the difference in the origin of organic matter in alginite and soil samples. The source of organic matter in alginite is mainly type II kerogen from algae and that of soil is lignin and cellulose (type III kerogen) of higher plants.

Fungicidal activities of soil humic/fulvic acids as related to their chemical structures in greenhouse vegetable fields with cultivation chronosequence.

In the background of rapid expansion of plastic greenhouse vegetable production in China, many environmental risks have emerged in recent years. In this study, the soils with a chronosequence in greenhouse vegetable fields were collected and the soil humic acids (HAs) and fluvic acids (FAs) were extracted and purified. The soil HAs and FAs were found to show inhibition activities against phytopathogenic fungi for the first time. Fourier transform infrared spectroscopy was performed to investigate the chemical structures of HAs and FAs. The variation of relative peak areas indicated the chemical structure of HAs become more complex and stable under continuous cultivation. The PCA analysis showed HAs and FAs could be distinctly separated from each other and cultivation years mainly determined the variation. Mantel test and RDA analysis indicated the active components (aliphatic peaks for HAs and COOH, OH peaks for FAs) had positive correlation with the inhibition rates of HAs and FAs against phytopathogenic fungi. According to our research, the active fungicidal components in soil HAs and FAs decreased along with the extension of cultivation years, which made the soil suffer more risk to phytopathogenic fugi. So we believe continuous cultivation too many years in PGVP systems is inadvisable.

Effect of land use change on soil organic carbon

Abstract The direction of changes and conversion of soil organic carbon (SOC) is in most current ecosystems influenced by human activity. Soil Science and Conservation Research Institute is responsible for monitoring the agricultural soils in a five-year cycle. One part of the soil monitoring involves the determination of the soil organic carbon (SOC) storage. Further, we followed the conversion of arable land on grassland during more than 20 years of monitoring period at some locations where changes in land use occurred. Ten places on basic network and 2 places on key monitoring localities in which arable land have been converted into grassland were identified. About 50 percent of studied soils converted into permanent grassland were Cambisols. The other converted soil types were Luvic Stagnosol, Stagnic Regosol, Mollic Fluvisol, and Stagnic Luvisol. The results showed that after the third monitoring cycle (2002), increase of SOC was observed in all the localities, with the change in land use. Statistical parameter (t-test) confirmed significant differences between the set of average SOC values before and after the land use conversion. The chemical structure of humic acids (HA) isolated from arable soil and permanent grassland indicated increasing of aliphatic carbon content in grassland HA. More aromatic and stabile were HA isolated from arable soils.

Changes in the composition of humic substances depending on the depth of peat occurrence

The fractional group composition of humic substances and the chemical structure of humic acids isolated from peats of different genesis from different depths of occurrence in peat deposits with the use of two extractants (0.1 N NaOH and 0.1 M Na4P2O7 at pH 7) were studied. Peat from the upper aerated layer of the peat deposits contained more humic substances than peat from the deep layer, which occurred under anaerobic conditions, due to the pyrophosphate fraction of humic acids and fulvic acids. The humic acids of peat isolated from the deep layers of deposits had smaller molecular weights, and they were characterized by lower concentrations of carbohydrate and saturated hydrocarbon fragments and an increased contribution of aromatic polyconjugation systems, as compared with the humic acids of a surface layer.

A novel organo-zeolite adduct for environmental applications: Sorption of phenol

A novel organo-zeolite adduct has been synthesized by sorbing humic acids (HA) onto zeolitic tuff and then heating the resulting complex at 330°C for 1.5h. Desorption tests showed that this procedure effectively immobilized HA on the tuff. The crystal structure of the zeolitic tuff and the chemical structure of HA were not altered during the preparation. Phenol sorption analysis demonstrated that the HA–zeolite adduct had good sorbing properties; moreover, the sorbed amount markedly decreased with increased ionic strength. These results point to prospective application of the HA–zeolite adduct as a low-cost and environmentally friendly sorbent for water purification from phenol and possibly other neutral organic pollutants.

Chemical structure of humic acids in biosolids-amended soils as revealed by NMR spectroscopy

We used NMR spectroscopy to characterize humid acids extracted from soils that had received long-term application of 2 levels of biosolids to evaluate the soil organic matter (SOM) stability in biosolids-amended soils. The study also quantified fulvic acids (FAs), humic acids (HAs) and Fe/Al oxides. The soils were collected in 2004 from 7 fields, in Fulton County, southwestern Illinois, which received biosolids at a cumulative rate of 0 (control), 554 (low biosolids) and 1,066 (high biosolids) Mg ha −1. The application of biosolids increased both FA and HA contents, but biosolids-amended soil and control soil did not differ in FA/HA ratio. Biosolids application had no effect on water-soluble organic carbon content. Biosolids application increased the presence of Fe/Al in the SOM complex and lowered its C/Fe and C/Al ratios. 13C NMR spectra showed increased alkyl C and decreased aromatic C content in soil HAs with the application of biosolids, and the extent of such changes was higher with high than low biosolids treatment. Under biosolids application, the soil HAs’ C structure shifts from O-alkyl-dominant to alkyl-dominant. Biosolids application does not decrease SOM stability but rather increases the stability of soil humic substances.

Research of chemical and toxic properties of humic acids of low-moor woody-grassy type of a peat in Tomsk Region

In article results of research of a chemical structure of humic acids of low-moor woody-grassy type of peat of Tomsk Region are resulted by methods of the elemental analysis and infra-red spectroscopy. In this work results of toxicological research of humic acids also are described: acute toxicity, pathomorphology and flow properties of blood. It is shown, that humic acids of low-moor woody-grassy type of peat represent connection with a high share aliphatic fragments submitted long connected by circuits, have a small degree benzenoid, contain active oxygen and itrogen-containing functional groups (carboxylic, hydroxyl, amides, amino groups). It is established, that humic acids at intragastric introduction are nontoxic substances. At intraperitoneal introduction of lethal dozes, the destruction of animals comes from acute intimate insufficiency, thus the cause of acute infringement hemodynamics can be negative influence of humic acids on flow properties of blood.

The effect of thermal treatment on the compositional structure of humic acids extracted from South African bituminous coal

The study was carried out to investigate the effect of thermal exposure on the chemical structure of humic acids with emphasis on the acidic functional groups (carboxylic and phenolic acid groups). This was carried out by treatment of humic acid samples at different temperatures ranging from 200 to 1000 °C under nitrogen atmosphere. Oxidation of the coal used followed by the humic acids' extraction led to the selective production of more carboxylic acid groups than phenolic groups although the amount of phenolic groups was found to be higher than the amount of carboxylic groups for both the parent coal and the extracted humic acids. The behaviour of acidic functional groups with the increase in temperature was monitored through analysis of the functional groups using surface-dependent techniques as well as IR. The results obtained from both IR and the surface-dependent functional groups' determination indicated a decomposition of the different functional groups with increase in temperature with carboxylic acids decomposing at lower temperatures (200–400 °C), and phenolic groups at much higher temperatures (about 600 °C and above). An increase in aromaticity with increase in temperature possibly due to char formation was also observed.

Reactivity of mechanical activated coals for special utilization

The paper presents the coal activation effect as disintegration in the nano-submicron range and destruction carbon structure. The Slovak brown coal activated in planetary mill is characterised by destruction of organic structure of coal. The biggest activation effect connected with the destruction of C—C bonds of sp3 carbons has been confirmed by 13C NMR spectroscopy in the chemical structure of humic acids extracted from the coal sample activated for a period of 60 min. The specific surface of humic acids is much smaller then that of mechanically activated sample from which they were extracted. The black Czech coal was activated by two stage disintegration. In the first stage of mechanochemical activation using Grinding Aqueous Caustic Leaching, GACL method a fine dispersed semiproduct is formed with the size of particles from 2.5 to 9000 nm. The additional disintegration using water jet increases the effect of disintegration in the submicron area of the coal product. The volume distribution maximum achieves in this stage about 60 wt% of 750 nm grains.

Structural Components of Humic Acids as Determined by Chemical Modifications and Carbon‐13 NMR, Pyrolysis‐, and Thermochemolysis‐Gas Chromatography/Mass Spectrometry

The chemical structure of humic acids (HAs) extracted from a grassland surface soil and peat were studied using bleaching (NaClO2 oxidation) and acid hydrolysis (6 M HCl) in combination with advanced analytical techniques: solid‐state 13C nuclear magnetic resonance (NMR), pyrolysis‐gas chromatography/mass spectrometry (GC/MS), and tetramethylammonium hydroxide (TMAH) thermochemolysis‐GC/MS. The purpose of the chemical treatments was to remove known structural fragments from the HA to study the building blocks and components of the macromolecule. Bleaching the peat HA resulted in an attack on the lignin structures leading to a significant reduction in the C‐substituted and O‐substituted aromatic C peaks (128 and 150 ppm) in the 13C NMR spectrum. However, the bleached soil HA still contained residual aromatic C, suggesting that part of its aromaticity had originated from aromatic structures resistant to bleaching, possibly black C (charcoal). The pyrolysates of the bleached HAs contained mainly alkanes and alkenes (C8 to C29), whereas TMAH thermochemolysis yielded a homologous series of long‐chain fatty acid methyl esters (FAMEs) (C8 to C32) and dicarboxylic acid dimethyl esters (DAMES). The data are comparable with those obtained from pyrolysis and thermochemolysis of plant cuticular materials, and therefore suggest that cuticular residues are an integral part of the HA macromolecule. The acid hydrolysis treatment removed esters, amides, carbohydrates, and some of the N‐containing compounds from the HAs. This study demonstrates the effectiveness of bleaching and hydrolysis treatments together with advanced analytical techniques for characterization of aliphatic, lignin‐derived (LG) and nonhydrolyzable N‐containing structures associated with the HA macromolecule.

Changes of humic acids structure on selected key monitoring localities of arable soils

Soil fertility is largely determined by the content and quality of soil organic matter. SlovakRepublic monitoring system includes evaluation of soil humus content, basic humic parameters and also chemical structure of humic acids (HA). Changes in humic acids structure on five selected key localities during monitoring period (1994–2000) are presented in this study. Among soil types, essentially between Chernozem and Planosol, in elemental analysis, optical parameter and 13C NMR parameters significant differences determined by Student’s test were observed (Tables 2 and 3). During monitoring period small oxidation trend mainly on Calcaric Fluvisol and Planosol HA expressed by increase of oxygen content and O/C, O/H ratio was observed. Oxidation trends during monitoring period confirm also position of Calcaric Fluvisol and Planosol HA on van Krevelen diagram. Changes in optical parameter E<sup>1%</sup><sub>6</sub>and content of carboxylic groups for the period of monitoring were negligible. Some changes throughout monitoring in <sup>13</sup>C NMR parameters were recorded. On all observed HA considerable decrease of carbon in region 106–143 ppm, characteristic for aromatic and olefinic carbon with C–C, C–H bond, was observed. Spectroscopic parameters are in good agreement with elemental analysis and carboxylic groups. Joint relationships between changes in determined parameters are expressed by significant linear correlations. Predominantly between parameters calculated from <sup>13</sup>C NMR spectra and data of elemental analysis and optical parameter E<sup>1%</sup><sub>6</sub>highly significant linear correlations (R > 0.93) are found (Table 4). 

Humic substances in the surface bottom sediments of the eastern part of the East China Sea:On the elementary composition, optical property and chemical structure of humic acids

Humic substances in the surface bottom sediments of the eastern part of the East China Sea:On the elementary composition, optical property and chemical structure of humic acids

A contribution to the knowledge of humic substances in peat waters

SummaryFollowing a brief description of the present views on the chemical structure of humic acids some results were given, obtained during the investigation of humic substances appearing in the peat waters of Czechoslovakia: 1. A new method for humic substances isolation was developed, based on butanolic extraction of the acidified substrate, concentration of the extract, and separation of the purified preparation of humic acids with every step made at normal temperature.2. A new extraction method for humic acids determination in peat waters was developed and verified on about 150 different samples collected from the peat water regions of Czechoslovakia.3. Only two types of humic substances were found in the peat waters of Czechoslovakia, i. e. humates of alkaline metals or free acids, and humates of alkaline earth and other metals. As high as 600 mg/l of humic substances were found in the most concentrated natural peat water sources (pools, drainages etc.), this amount decreasing to some units of mg/I found in streams coming from the peat areas.4. Five points were presented proving the similarity of humic acids and their common properties, based on the analysis of 150 peat water samples of different origin.

On the components of soil humic acids (part 8) the oxidative decomposition by alkaline potassium permanganate and nitric acid

Abstract As for the reactions by oxidizing agents of humic acids and for the products obtained by the said reactions, a number of investigations (1) have been made with regard to the study of the chemical structure of humic acids and with the use of the products of decomposition. The authors (2) have observed that A-or B-types of soil humic acids could be separated into three or four fundamental composing fractions by using Al2O3 column.