Characteristics Of Humic Acids Research Articles

Potential origin and formation for molecular components of humic acids in soils

Soil humic acids are the base soluble/acid insoluble organic components of soil organic matter. Most of what we know about humic acids comes from studies of their bulk molecular properties or analysis of individual fractions after extraction from soils. This work attempts to better define humic acids and explain similarities and differences for several soils varying in degrees of humification using advanced molecular level techniques. Our investigation using electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) and nuclear magnetic resonance spectroscopy (NMR) has given new insight into the distinctive molecular characteristics of humic acids which suggest a possible pathway for their formation. Humic acids from various ecosystems, climate regions and soil textural classes are distinguished by the presence of three predominant molecular components: lignin-like molecules, carboxyl-containing aliphatic molecules and condensed aromatic molecules that bear similarity to black carbon. Results show that humification may be linked to the relative abundance of these three types of molecules as well as the relative abundance of carboxyl groups in each molecular type. This work also demonstrates evidence for lignin as the primary source of soil organic matter, particularly condensed aromatic molecules often categorized as black carbon and is the first report of the non-pyrogenic source for these compounds in soils. We also suggest that much of the carboxyl-containing aliphatic molecules are sourced from lignin.

Sarykul paleosol in Southern Urals sediments (Russia)

Sarykul paleosols in the Southern Urals (Russia) with a stable position in geological sediments are considered. The Brunhes-Matuyama boundary was found in these paleosols and they were used as a source of information on the environment. Data were obtained during the study of the Sarykul paleosols in four sections located in the mountain part of the Southern Urals on the Miass River erosion-accumulation terrace and at the eastern edge on the trans-Uralian peneplain. Saykul paleosols have a relatively thick and compact humic horizon with a tongued lower boundary. The paleosols are dark grey with high TOC content that is not usual for the Early Pleistocene paleosols. The materials showed that Sarykul paleosols formed on different parent rocks may have various characteristics of the mineral part (texture, pH, magnetic susceptibility, carbonate content, ratio of exchangeable cations), while their humic substances characteristics (humic and fulvic acid ratio, humic acid characteristics of elemental composition and structure) are very similar. Climate conditions during Sarykul paleosol formation changed from relatively warm and humid to less warm and more humid. The study of Southern Urals Sarykul paleosols has shown that they can serve as a reliable marker of the final Early Pleistocene due to their specific characteristics, not analogous to the modern soils.

Effect of inoculation during different phases of agricultural waste composting on spectroscopic characteristics of humic acid

The white-rot fungus, Phanerochaete chrysosporium (P. chrysosporium), was inoculated during different phases of agricultural waste composting and its effect on the spectroscopic characterization of humic acid (HA) was studied. Three runs were used in this study: Run A was the control without inoculating, and Runs B and C were inoculated P. chrysosporium during the first and the second fermentation phase, respectively. The elemental analysis, ultra-violet spectroscopy (UV), fluorescence spectra, Fourier transform infra-red (FTIR) and 13C nuclear magnetic resonance (13C-NMR) of HA all lead to the same conclusion, that is, the degree of aromatization and polymerization of HA increases after 42 days composting. However, the inoculation during different phases presents different effects. P. chrysosporium increases the degree of aromatization and polymerization of HA when it is inoculated during the second fermentation phase, while it does not produce an obvious change on the humification degree of HA when it is inoculated during the first fermentation phase.

北海道中央部に湧出する温泉水中のフミン酸の分析と特性

北海道中央部に湧出する温泉水中のフミン酸の分析と特性

ВЛИЯНИЕ СТРУКТУРНЫХ ХАРАКТЕРИСТИК ГУМИНОВЫХ КИСЛОТ НА ЭФФЕКТИВНОСТЬ ВЗАИМОДЕЙСТВИЯ С КАТИОНАМИ ПОЛИВАЛЕНТНЫХ МЕТАЛЛОВ

The paper considers the interaction of modified peat humic acids with salts of heavy metals under various pH. It was shown the change of structural characteristics of humic acids in the process of mechanical activation under reducing conditions. Regardless of the conditions mechanical activation slightly increases the degree of aromaticity due to possible condensation reactions. At mechanical activation of peat in the air without any reagents one observes oxidation of the peripheral carbohydrate fragments in the structure of humic acids. Modification in argon reduces the number of carboxyl and carbonyl groups, phenolic hydroxyls; oxidized aromatic fragments and "lignin" components in the composition of humic acids and naturally increases a proportion of alkyl substituentsIt is revealed that modified humic acids enriched oxygen-containing groups have the highest sorption capacity in relation to ions of copper and nickel. Probability and stability of the forming chelate complexes are determined by the composition and the number of oxygen-containing ionogenic groups and acid-base balance. Sorption capacity of the humic acids with respect to a nickel ion is lower than that to a copper ion.

The coagulation characteristics of humic acid by using acid-soluble chitosan, water-soluble chitosan, and chitosan coagulant mixtures

Chitosan is a potential substitute for traditional aluminium salts in water treatment systems. This study compared the characteristics of humic acid (HA) removal by using acid-soluble chitosan, water-soluble chitosan, and coagulant mixtures of chitosan with aluminium sulphate (alum) or polyaluminium chloride (PACl). In addition, we evaluated their respective coagulation efficiencies at various coagulant concentrations, pH values, turbidities, and hardness levels. Furthermore, we determined the size and settling velocity of flocs formed by these coagulants to identify the major factors affecting HA coagulation. The coagulation efficiency of acid- and water-soluble chitosan for 15 mg/l of HA was 74.4% and 87.5%, respectively. The optimal coagulation range of water-soluble chitosan (9–20 mg/l) was broader than that of acid-soluble chitosan (4–8 mg/l). Notably, acid-soluble chitosan/PACl and water-soluble chitosan/alum coagulant mixtures exhibited a higher coagulation efficiency for HA than for PACl or alum alone. Furthermore, these coagulant mixtures yielded an acceptable floc settling velocity and savings in both installation and operational expenses. Based on these results, we confidently assert that coagulant mixtures with a 1:1 mass ratio of acid-soluble chitosan/PACl and water-soluble chitosan/alum provide a substantially more cost-effective alternative to using chitosan alone for removing HA from water.

Molecular characteristics of humic acids isolated from vermicomposts and their relationship to bioactivity.

Vermitechnology is an effective composting method, which transforms biomass into nutrient-rich organic fertilizer. Mature vermicompost is a renewable organic product containing humic substances with high biological activity. The aim of this study was to assess the chemical characteristics and the bioactivity of humic acids isolated from different vermicomposts produced with either cattle manure, sugar cane bagasse, sunflower cake from seed oil extraction, or filter cake from a sugar cane factory. More than 200 different molecules were found, and it was possible to identify chemical markers on humic acids according to the nature of the organic source. The large hydrophobic character of humic extracts and the preservation of altered lignin derivatives confer to humic acids the ability to induce lateral root emergence in maize seedlings. Humic acid-like substances extracted from plant biomass residues represent an additional valuable product of vermicomposting that can be used as a plant growth promoter.

Properties of soil organic matter in Podzols under mountain dwarf pine (Pinus mugo Turra.) and Norway spruce (Picea abies (L.) Karst.) in various stages of dieback in the East Sudety Mountains, Poland

Dieback of forests because of industrial air pollution was observed in the East Sudety Mountain, Poland. The properties of soil organic matter in Podzols in the subalpine region under mountain dwarf pine and Norway spruce in various stages of dieback (without degradation, with about 50% brown needles and dead trees) were investigated. The content of carbon, nitrogen, humic substances and characteristics of humic acids (HA) from organic and mineral horizons were analyzed. Forest dieback influenced HA properties depending on the species. Under pine, it led to an increase in alkyl and carboxyl C, while an increase in aromatic C and O- alkyl C was found at spruce sites. Humic acids under Picea abies were characterized by more aliphatic structures, whereas HA under Pinus mugo were more aromatic in nature. HA created in soils under pine stands in the investigated area showed lower solubility, higher stability and a lower tendency to translocate to deeper parts of the soil profile, compared to those under Norway spruce. Organic matter under spruce monoculture can be more susceptible to oxidation and may have less impact on the stability of soil aggregates, than those under pine ecosystems. Conversion of spruce monocultures to mixed forest – more resistant to biotic and abiotic disturbances – or introduction of the pioneer tree species in Norway spruce stands may be an effective tool to prevent forest decline and ensuring the stability of forest ecosystems.

Effects of peat fires on the characteristics of humic acid extracted from peat soil in Central Kalimantan, Indonesia.

When peat forest fires happen, it leads to burn soil and also humic acids as a dominant organic matter contained in peat soil as well as the forest. The structure and properties of humic acids vary depending on their origin and environment, therefore the transformation of humic acid is also diverse. The impacts of the peat fires on peat soil from Central Kalimantan, Indonesia were investigated through the characterization of humic acids, extracted from soil in burnt and unburnt sites. The characterization of humic acids was performed by elemental composition, functional groups, molecular weight by HPSEC, pyrolysate compounds by pyrolysis-GC/MS, fluorescence spectrum by 3DEEM spectrofluorometer, and thermogravimetry. The elemental composition of each humic substance indicated that the value of H/C and O/C of humic acids from burnt sites were lower than that from unburnt sites. The molecular weight of humic acids from burnt sites was also lower than that from unburnt sites. Pyrolysate compounds of humic acids from unburnt sites differed from those of humic acids from burnt soil. The heating experiment showed that burning process caused the significant change in the properties of humic acids such as increasing the aromaticity and decreasing the molecular weight.

Chemical and spectroscopic characteristics of humic acids and dissolved organic matter along two Alfisol profiles

The aim of this study was to elucidate the heterogeneous structural and functional composition of humic acids (HAs) and dissolved organic matter (DOM) isolated from two Alfisol profiles with different soil texture, in order to develop a better understanding of the organic matter dynamics. Soil samples were collected at different depths from three (Ap, 2AB and 2Bt) and eight (A1, A2, A3, E1, E2, 2Bt1, 2Bt2 and 2Bt3) soil horizons of two Alfisols located in the south (PR1) and north (PR2) of Italy, with a clay texture and a silt loam to loam ones, respectively. Chemical and spectroscopic methods were used to characterize the HAs and the DOM isolated from different soil horizons, including Ultraviolet–Visible (UV–Vis), Fourier Transform Infrared (FTIR), and Fluorescence spectroscopies. The HAs and the DOM isolated from the two Alfisols apparently showed significant differences in their compositional, structural and functional characteristics. In particular, the HAs isolated from the PR1 featured a higher degree of humification and molecular complexity with respect to those isolated from the PR2. On the contrary, the DOM samples isolated from the PR2 showed a more marked aromatic character and polycondensation degree. Both the HAs and the DOM obtained from the PR1 presented a greater qualitative homogeneity with respect to those obtained from the PR2. These results could be reasonably ascribed to the different texture and horizons of the two Alfisols, and to a greater pedogenesis occurred in the PR1.

Sorption of humic acid on Fe oxides, bacteria, and Fe oxide-bacteria composites

Purpose Sorption of humic substances on other soil components plays an important role in controlling their function and fate in soil. Sorption of humic substances by individual soil components has been studied extensively. However, few studies reported the sorption characteristic of humic substances on composites of soil components. This study aimed to investigate the sorption characteristics of humic acid on Fe oxide-bacteria composites and improve the understanding on the interaction among humic substance Fe oxide bacteria in soil.

Спектральна характеристика гумінових кислот ґрунтів середньосухостепового педоекотона Північно-Західного Причорномор’я

Spectral methods established genetic and geographic characteristics of humic acids in soils of medium-dry Steppe pedoekoton. It was determined that in terms of the optical density of the soil of transition from dry to medium Steppe are southern chernozems. Key words: optical density, humic acid, southern chernozems, dark kastanozems.

Seasonal variability of a conditional stability constant and the characterization of sedimentary humic substances from typical agricultural and urban areas

Brazil is the largest producer of sugarcane in the world. This extensive production of sugarcane has changed the use and form of Brazilian soil, causing changes in the structural characteristics of humic substances (HS). In this context, the main objective of this study was to evaluate the effect of seasonality on a conditional stability constant (Kc) of the complexes HS-Cu (II) and HS-Cr (III) from the HS of urban and agricultural regions, with an emphasis on sugarcane culture. The study was conducted in the northwestern region of the state of Sao Paulo, which is the leading producer of sugar and ethanol in the country and is the region with the lowest percentage of riparian vegetation (3 %). Sediments were sampled during the rainy and dry seasons at four locations: (1) a typical agricultural area, (2) an urban area, (3) a sugarcane cultivation area, (4) and an area that receives the entire pollutant load from the hydrographic basin. The HS were extracted and characterized using conventional techniques. The Kc of the HS with copper (Cu) and chromium (Cr) ions was determined by fluorescence suppression employing the Stern–Volmer model. Kc values were higher in the rainy seasons for HS-Cu (II) and HS-Cr (III). The highest value of Kc for the HS with Cu (1.23) and Cr (5.2 × 10−1) ions was found during the rainy season in the area receiving the pollutant load from the basin and in the typical area of sugarcane cultivation, respectively. All of the FTIR spectra showed characteristic bands of HS, and the values of the E4/E6 ratio confirmed the presence of more aromatic groups. An elemental analysis and molecular fluorescence spectra in the emission mode confirmed that the HS from the agricultural area and sugarcane culture area mostly exhibited characteristics of humic acids and that the HS from the urban area and the area receiving the pollutant load from the basin had a mixture of humic and fulvic acids. We can conclude that HS–metal complexes from the area that received the entire load of pollutants from the watershed and the typical area of sugarcane culture showed the highest stability among the study areas. The Kc values found in the basin were lower than those previously obtained by several studies that were performed in other locations. The HS obtained in rainy season had more aromatic groups in the HS structure, and the HS from the sugarcane area presented more characteristics of humic acids.

The effect of aerobic conditions on the complexation ability between mercury and humic acid from landfill leachate and its implication for the environment

Three-dimensional excitation emission matrix (3DEEM) fluorescence spectroscopy was employed to investigate the structure and characteristics of humic acid (HA) from landfills at different stabilization processes. The results show that the HA in anaerobic landfill leachate stabilized more rapidly than that in semi-aerobic landfill leachate. There were strong interactions between HA and Hg, the S content as well as the oxygen-containing ligands of the HA played a key role in the complexation with mercury. The higher complexation capacity (CL) and stability constant (logK) of HA from anaerobic landfill leachate implies that it is important to strengthen the control of mercury transportation in anaerobic landfills during the early stabilization process. The logK and CL of HA from semi-aerobic landfill leachate increased with the landfill time indicate that control of leachate Hg contamination in the latter stage is of great significance in semi-aerobic landfills.

Spectroscopic studies of the effect of aerobic conditions on the chemical characteristics of humic acid in landfill leachate and its implication for the environment

Humic acids (HAs) that extracted from leachates from semi-aerobic and anaerobic landfills test field at different stabilization times were characterized by elemental composition, Fourier transform infrared spectroscopy (FTIR), and Carbon-13 Cross-Polarization Magic-Angle-Spinning Nuclear Magnetic Resonance (13C CP/MAS NMR). The higher sulfur (S) content of HA in the anaerobic landfill leachate after a short stabilization time showed that the S released from the organic matter degradation was more easily stabilized under anaerobic conditions, which indicate that HA from anaerobic landfill leachate was more chemically reactive and played a more important role in mobilizing heavy metal, especially mercury, at early landfill stabilization times. However, the S content of HA from the semi-aerobic landfill increased over time, suggesting that more S was stabilized in HA as the landfill stabilization time was extended. The analytical results for the FTIR and NMR showed that the HA from the anaerobic landfill contained more aromatic groups, while HA from the semi-aerobic landfill had more oxygen-containing groups. The aromatic components of the HA from both the anaerobic and semi-aerobic landfills increased over time, suggesting that the maturity and humification degree of HA increased during the stabilization process.

Complex-forming properties of peat humic acids from a raised bog profiles

Humic substances (HS) belong to the most powerful complex-forming agents, significantly affecting major and trace element speciation in natural environment. Several authors have focused on humic–metal interactions, using differing methods and comparing humic substances on different sources. However, the intrinsic differences among the HS of different origin and the impact of humification degree on the complex formation between humic substances and metals have not received the necessary attention until now.The aim of this study is to determine the Cu(II) complexing capacity and stability constants of Cu(II) complexes of humic acids (HA) isolated from two well-characterized raised bog peat profiles in respect to the basic properties and humification characteristics of the studied peats and their humic acids. Elemental and functional analysis of the isolated HA were determined by elemental composition (C, H, N, O), UV spectrophotometry, and the total acidity method, as well as the copper (Cu2+) ion selective electrode was used in complexing analysis of humic acids and metal ions.The complex stability constants are within the range of stability constants of the humic substances isolated from other sources (soil, coal, water, and peat). The complex stability constants significantly changed within the bog profiles and are well correlated with the age and the degree of peat decomposition.A comparison of the complex stability constant and the actual copper concentration in peat humic acids shows significant correlation, indicating the importance of tight metal binding for the actual presence of metal in peat and peat humic acids. None of the basic characteristics of humic acids (concentration of carboxylic groups and total acidity, hydrophobicity, etc.) alone can fully explain the complex-forming capacity of humic acids, which suggests a contribution of other factors that are yet to be determined.

Humic acid characteristics and effects on the reactivity of nano-scale zero-valent iron particles during nitrate reduction

ABSTRACT Humic acid (HA) comprises a significant fraction of natural organic matter (NOM), greatly influencing the performance of water and wastewater treatment processes. HA is expected to significantly affect the reactivity of nano-scale zero-valent iron (NZVI), which is receiving increasing attention due to its high reactivity. The effects of HA on nitrate reduction by NZVI were investigated to evaluate the potential of NZVI in practical applications. HA was characterized to identify the mechanism whereby HA affects. Nitrate reduction was enhanced at low HA concentration, but inhibited as HA concentration increased. HA decreased to reach a plateau and considerable amount of Fe3+ was detected when HA was present in dissolved phase. The increase in the degree of condensation of HA was verified by UV–vis spectroscopy, fluorescence spectroscopy, and size exclusion chromatography. Fourier transform infrared spectra confirmed that the Fe3+–HA complexes were formed in both the dissolved and solid fractions, without coexisting metal ions. The HA aggregation on NZVI and discrete HA macroaggregates were observed by transmission electron microscopy. The results suggest that HA induces complex effects on NZVI reactivity by improving iron dissolution, inhibiting readsorption of released iron, enhancing electron transfer, and inhibiting nitrate mass transfer via forming HA accumulation. It indicates that the clogging by aggregated NOM should be considered when NZVI is used for groundwater treatment or in combination with porous materials.

Chemical and spectroscopic characteristics of humic acids in marshes from the Iberian Peninsula

To characterise soil humic acids (HAs) extracted from Spanish marshes formed under different vegetation types (Spartina maritima (GSp), Juncus maritimus (GJc), Phragmites australis (GPh), and Scirpus maritimus (VSc)), soil depths (0–20, 20–40 and 40–60 cm), physiographic position (low and high marshes), wetland types (salt marshes and lagoons) and environmental conditions (Atlantic and Mediterranean coast). Soil samples were collected in five Spanish marshes, three on the Galicia province and two on the Valencia province. Humic acids were extracted and their elemental composition, semiquinone-type free radical (SFR) content, FTIR and CPMAS 13C NMR spectra determined. Total carbon (TC), total nitrogen (TN), total sulphur (TS), CaCO3 content, and field pH and Eh (mV) in the marsh soils sampled were also measured. The field pH and Eh values were typical of coastal areas submitted to periodic inundations and the highest TC, TN and TS contents were found in the soil of lagoon marshes as an effect of physiographic position and wetland type. The HAs, in general, were highly aliphatic and exhibited a low SFR content, which suggests a low humification degree of the SOM formed in the studied areas. This is a result of the anaerobic decomposition to which SOM is submitted and the high input of plant-derived organic matter (OM) by vegetation. However, among the studied sites low salt marsh and subsurface layer of the high salt marsh showed higher SFR content, simpler FTIR spectra, higher lignin degradation and lower O-alkyl C/alkyl C ratio than the lagoon marshes, thus suggesting the presence of a more humificated SOM in these sites. From the different factors analysed, only physiographic position (low versus high salt marshes) and wetland type (marshes versus lagoons) caused variations in the HAs characteristics, because as the studied soils are under anaerobic conditions, they control the exportation of plant-derived OM and the allochthonous OM contribution in the studied areas.

Semiarid soils submitted to severe drought stress: influence on humic acid characteristics in organic-amended soils

Purpose The objective of this work was to assess the effect of severe drought conditions on the characteristics of semiarid soil humic acids (HAs) as well as the effect of organic amendment on such changes.

Comparison between the humic acids characteristics of two andisols of different age by: FT-IR and 1H-NMR spectroscopy and py-FIMS

Mt Etna (Italy) is the highest, active volcano in Europe. Thanks to the availability of descriptive documents and maps, it is possible to date the formation of several Etna soils. We evaluated the effect of soil formation age on the composition of the soil organic matter (SOM) and humic acids (HAs) from two Etna andisols of different ages but having the same vegetation (Castanea saliva) and pedogenetic substrate (tephra). The characterization of the SOM and the HAs was carried out by elementary and functional group analysis, UV-visible spectrophotometry, Fourier Transform InfraRed (FT-IR) and 1H-Nuclear Magnetic Resonance (1H-NMR) spectroscopies, and Pyrolysis-Field Ionization Mass Spectrometry (py-FIMS). Data showed that the age of the soil cannot be considered as influencing the chemical composition of the SOM. However higher volatilisation temperatures, for some compound classes, indicate the presence of more thermally-stable, organic molecules, therefore a more mature organic matter, or an organic component more greatly bound to the mineral component in the older soil. Finally the HA extracted from old soil contains a lower quantity of aliphatic compounds and a greater quantity of carbohydrate and aromatic molecules than the HA extracted from young soil.