Characterization of humic acids from tundra soils of northern Western Siberia by electron paramagnetic resonance spectroscopy

Humic acids from polar soils—cryozems (Cryosols), gleyezems (Gleysols), and peat soils (Histosols)—have been studied by electron paramagnetic resonance spectroscopy. First information was acquired on the content of free radicals in humic acids from polar soils for the northern regions of Western Siberia (Gydan Peninsula, Belyi Island). It was found that polar soils are characterized by higher contents of free radicals than other zonal soils. This is related to the lower degree of humification of organic matter and the enhanced hydromorphism under continuous permafrost conditions. The low degree of organic matter humification in the cryolithozone was confirmed by the increased content of free radicals as determined by electron paramagnetic resonance, which indicates a low biothermodynamic stability of organic matter.     

土壤腐殖质分组研究

采用Pallo法对两种耕地土壤腐殖质进行分组,初步研究了各组分的数量和结构特征。结果表明:焦磷酸钠提取的胡敏酸(HAp)是胡敏酸(HA)的主要组分;游离富里酸(FAf)是富里酸(FA)的主要组分;胡敏素(HM)的主要组分为非溶解性胡敏素(ISHM),而溶解性胡敏素(SHM)含量较低。通常随土层深度增加,HA、HM各组分的绝对数量和相对数量都下降;FA各组分的绝对数量也下降,而相对数量增加;HA/FA比值下降。一般来看,焦磷酸钠提取的富里酸(FAp)、氢氧化钠提取的富里酸(FAs)比相应的HAp、氢氧化钠提取的胡敏酸(HAs)的分子结构简单,铁结合胡敏素(HMi)比粘粒结合胡敏素(HMc)的分子结构简单;随土层深度增加,HAp、HAs的分子结构变简单,而HMi、HMc的分子结构变复杂。     

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.     

Soil organic matter alteration under biochar amendment: study in the incubation experiment on the Podzol soils of the Leningrad region (Russia)

Purpose

Biochar is one of the most widely used ameliorants for soil amendment, which is known as factor which rises crop yields and levels of soil biological activity. Nowadays, it is under investigated how biochar application affects the dynamics of the humic components and whole soil organic matter (SOM) and the processes of its alteration. This investigation is aimed to evaluate the influence of biochar on the content, composition, and transformation of humic acids (HAs) as the main component of the SOM.

Materials and methods

The incubation experiment was carried out on three Podzol Antric soils, with varying amounts of initial total organic carbon. The incubation time was 90 days, using biochar gravimetric doses of 0.1 and 1.0%. The biochar was produced by fast pyrolysis of birch and aspen wood at 550 °С. Humus composition was analyzed for the organic matter fractions extracted with 0.1 M NaOH (containing HAs 1 + fulvic acids (FAs) 1) and 0.1 M Na₄P₂O₇ (containing HAs 1 + FAs 1 + HAs 2 + FAs 2). Isolated HAs were characterized for their elemental composition (C, N, H, and S) and molecular composition with the use of solid-state 13C nuclear magnetic resonance (13C-NMR) techniques.

Results and discussion

We found that 0.1% of biochar amendment does not influence SOM mineralization, but 1.0% of biochar increases the mineralization by 15–18%. This process is accompanied by changes in the composition and properties of the HS. The increased proportion of HA aromatic fragments in biochar indicates an increasing of their stability. However, in soils with high humus content and a significant amount of insoluble matter, the processes of mineralization and the growth of HAs are taking place simultaneously. The replenishment of HAs could be the outcome of both the intensification of the transformation processes (mineralization and humification) of the more sustainable insoluble matter compounds and the humification of the biochar itself.

Conclusions

The influence of biochar on humification in Podzol Antric soils was revealed on the basis of incubation experiment. Both negative and positive changes under biochar in HS system were demonstrated. The active decrease of humus total contents and also the labile HS ought to qualify as negative changes. The increase of HA chemical maturity that leads to the stability of humus in whole as well as the intensive new HA formation thought to qualify as positive changes.

     

Characterization of humic substances derived from swine manure-based compost and correlation of their characteristics with reactivities with heavy metals

Various composts contain a significant amount of humic substances including humic acid (HA) and fulvic acids (FAs). The FA fraction in soils is considered to be sensitive to agronomic and environmental factors. In this study, three fractions of humic substances, HA (MW > 1000 Da), FA (MW > 1000 Da), and FA (MW < 1000 Da) were extracted from swine manure-based compost and characterized, and then, their reactivities were correlated with heavy metals. Compositions of the three fractions of humic substances were characterized by elemental and total acidity analyses and electron spin resonance (ESR), Fourier transform infrared (FTIR), and 13C nuclear magnetic resonance with cross-polarization and magic-angle spinning spectroscopic techniques. Elemental analyses indicated that HA has higher contents of C, H, N, and S than those of FAs. However, FA (MW > 1000) and especially FA (MW < 1000) have higher contents of O than that of HA (MW > 1000). The g values of the ESR spectra of the three fractions showed that the organic free radical characteristics and the widths of the spectra and free radical concentrations of the three fractions are significantly different. The FTIR spectra indicated that HA (MW > 1000) is abundant in C=C bonds while FA (MW > 1000), especially FA (MW < 1000), are abundant in C=O bonds. In addition, 13C NMR spectra indicate that carboxyl contents of FA (MW > 1000), especially FA (MW < 1000), are higher than that of HA (MW > 1000). The sequence of the reactivity in terms of acidic functional groups was FA (MW < 1000) > FA (MW > 1000) > HA (MW > 1000). Elemental and functional group compositions of the three fractions significantly correlated with reported reactivities with heavy metals. The application of swine manure-based compost containing HA and FAs fractions to soil and associated environments may thus significantly affect the concerned reactions with organic and inorganic compounds including pollutants.     

Molecular composition of humic substances in tundra soils (13C-NMR spectroscopic study)

Functional groups and molecular fragments of humic substances (HSs) from cryohydromorphic peat gley tundra and surface-gley tundra soils have been identified by ¹³C-NMR spectroscopy. The analysis of HS preparations has shown that the molecules of humic acids (HAs) are enriched with aromatic fragments compared to fulvic acids (FAs). Aliphatic chains, carbohydrate- and amino acid-type structures prevail in the carbon skeleton of the FAs. An integrated parameter of the HS hydrophobicity has been proposed. The parameter represents the total portion of unoxidized carbon atoms and allows indirectly assessing the amphiphilic properties of HSs.     

Chemical and spectroscopic characterization of Humic acids from a soil toposequence in venezuela

Abstract

An investigation was conducted on physico‐chemical properties of humic acids (HAs) in Venezuelan soils. The HAs were extracted by the NaOH method from a Banco‐Bajio‐Estero soil toposequence (local names for soils located at high, intermediate and low topographic levels), in the Venezuelan plains (Mantecal, Apure State). The extracted HAs were analyzed for elemental composition and characterized by fluorescence, Fourier transform infrared (FT‐IR) and electron spin resonance (ESR) spectroscopies. The results showed that free radical concentration of HAs increased from soils at the highest to soils at the lowest topographic position. High carbon (C), nitrogen (N), and carboxyl group contents, E₄/E₆ ratio, aliphatic character and concentration of free radicals, and low oxygen (O) and phenolic hydroxyl group contents and total acidity were typical of HA from soils at the lower relief position. The FT‐IR spectra indicated that the HA from the soil at the lowest topographic position tended to have a slightly higher content of carboxyl groups than the HAs from soils at higher topographic levels. The observed fluorescence was attributed to the presence of condensed aromatic moieties and/or conjugated unsaturated systems of various complexity in the HA macromolecules.     

Effects of pig slurry application on soils and soil humic acids

The effect of three annually consecutive additions of pig slurry at two rates (90 and 150 m3 x ha(-1) x year(-1) on soils and soil humic acids (HAs) was investigated in a field experiment under semiarid conditions. Soils and pig slurries were analyzed by standard methods. The HAs were isolated from soils and pig slurry by a conventional procedure based on alkaline extraction, acidic precipitation to pH 1, purification by repeated alkaline dissolutions and acidic precipitations, water washing, dialysis, and final freeze-drying. The HAs obtained were analyzed for elemental (C, H, N, S, and O) and acidic functional group (carboxylic and phenolic) composition, and by UV-vis, FT-IR, fluorescence, and ESR spectroscopies. With respect to the control soil, the pig slurry amended soils had greater pH and electrical conductivity, slightly larger total N content, and smaller values of C/N ratio. A decrease of total organic C was observed only in soils amended for 2 and 3 years at the higher slurry rate. With respect to control soil HA, pig slurry HA was characterized by larger contents of S- and N-containing groups, smaller acidic functional group and organic free radical contents, a prevalent aliphatic character, extended molecular heterogeneity, and smaller aromatic polycondensation and humification degrees. Amendment with pig slurry HA determines a number of modifications in soil HAs, including increase of C, S, and COOH contents, C/N ratios, and aliphaticity and decrease of extraction yields and N, O, phenolic OH, and organic free radical contents. These effects are generally more evident after the first year of slurry application and tend to disappear with increasing number of treatments. Most probably, over the years the slightly humified slurry HA is mineralized through extended microbial oxidation, whereas only the most recalcitrant components, such as S-containing, phenolic, and aliphatic structures, are partially accumulated by incorporation into soil HA.     

不同年代的埃特纳火山土壤上用甘油萃取有机质的特性

We characterized humic acids (HAs) and glycerol-extractable organic fractions (GEOFs) extracted from four Andisols, taken from comparable soil-climate conditions on the east side of Mount Etna. The soils were formed on old lava (about 9 000 years ago), old tephra (about 8 700 years ago), recent lava (about 2 600 years ago) and recent tephra (about 3 600 years ago). A part of the organic matter of the soils, deprived of HAs and fulvic acids (FAs), was isolated by glycerol extraction. The GEOF can not be extracted with alkaline solutions, probably because it is closely bound to the mineral component of the soil. The characterization of the extracted organic fraction was carried out using elementary and functional group analysis and Fourier transform infrared (FT-IR) spectroscopy. About 20 extractions were necessary to extract the HA and FA from the older soils and about 10 extractions to extract them from the younger soils. Data showed that the GEOFs had a greater ash content and a smaller N content, as well as a greater presence of aliphatic compounds and carboxylic groups as compared to the HA extracted from the same soil. The GEOFs extracted from younger soils also had a lower yield, ash and COOH-group content, and were more aliphatic than the GEOF extracted from older soils. Finally, the GEOFs were more closely bound to the amorphous component of the soil (‘short-range’ minerals) and consequently less subject to biodegradation.     

粘土矿物对土壤腐殖质化学性质的影响

Chemical characteristics of humic substances in soils with different mineralogical characteristics and under different utilization paterns in Zhangpu,Fujian Province,together with two pairs of cultivated soils in North China Plain were studied by chemical analysis,visible and IR spectroscopy and ^13C NMR spectrometry.For soils in Zhanpu the HA/FA ratio and both the aromaticity and the degree of humification of HA were higher in soils with montmorillonite as the predominant clay mineral than in those with kaolinite as the predominant clay mineral,provided these soils were under the same utilization pattern.While for each pair of soils with similar mineralogical characteristics the HA/FA ratio was higher and the C/H ratio and the contnet of carboxyl group of HA were lower in paddy soil than in upland soil.Among the upland soils(or paddy soils)studied the Ha/FA ratio of soil in Zhangpu with kaolinite as the predominant clay mineral was the lowest,and that of soil in Zhangpu with montmorillonite as the predominant clay mineral was the highest .the lowest.and that of soil in Zhangpu with montmorillonite as the predominant clay mineral was the highest It was concluded that the presence of montmorillonite favored the fromation and maturation of humic acid.     

Phosphorus in humus acids

The distribution of phosphorus among humus acid groups in different soil types was studied. It was shown that the binding of P with acid-soluble and-insoluble organic components is determined by the acid-base status of soils, which controls the predominant interaction of P with Fe and Al or with Ca and Mg, and the solubility of the resulting organic phosphates in acid and alkali. The major part of P is associated with the group of humic acids (HAs) in the acid soils and with fulvic acids (FAs) in the neutral and calcareous soils. During the fractionation of organic matter from acid soils, the amount of P redistributed from the HA to the FA group can increase with an increasing acid or alkaline impact on the soil, which breaks the bonds of the phosphorus-bearing organic components with metals.     

Characteristics of Humic Substances in Paddy Soils

In the present paper,the composition of humus and the charateristics of humic acid from seven paddy soils were compared with those of upland (and/or natural) soils.Results show that:(1) in each group of the soil samples for comparison the HA/FA ratio of the humus of a paddy soil,in most cases,was appreciable higher than that of adjacent upland(and/or natural) soil derived from the same parent material;(2) the humic acid extracted from the paddy soils was characterized by a higher C/O ratio,a higher content of methoxyl groups,and a lower content of carboxyl groups than those from the corresponding upland (and/or natural) flooded soils,implying that the humic acid formed under rice cultivation is in a lower degree of humification than that formed under upland(and/or natural) conditions;and (3) the humic acid of paddy soils,however,was not always characterized by a lower aromaticity than that of the corresponding upland(and/or natural) soils.     

Compositional and functional features of humic acids from organic amendments and amended soils in Minnesota, USA

The use of organic amendments requires an adequate control of the chemical quality of their humic acid (HA)-like fractions and of the effects that these materials may have on the status, quality, chemistry and functions of native soil HAs. In this work, the compositional, functional and structural properties of the HA-like fractions isolated from a liquid swine manure (LSM), a municipal sewage sludge (SS), and two municipal solid waste composts (MSWCs) were evaluated in comparison to those of HAs isolated from three unamended soils and from the corresponding soils amended with LSW, SS, and MSWC at various rates in three field plot experiments conducted in Minnesota, USA. With respect to the unamended soil HAs, the HA-like fractions of the three amendments featured a greater aliphatic character, a marked presence of proteinaceous, S-containing and polysaccharides-like structures, an extended molecular heterogeneity, small organic free radical contents and a small degree of humification. The MSWC-HAs featured a larger degree of humification than LSM-HA and SS-HA. The three amendments affected in different ways and by various extents the compositional, structural and functional properties of soil HAs depending upon the nature, origin and application rate of the amendment. In general, the data obtained suggested that proteinaceous, S-containing and aliphatic structures contained in HA-like fractions of organic amendments were partially incorporated into native soil HAs.     

Humus Characterization of Humid Tropical Forest,Tea Garden,and Field Crop Soils of West Bengal,India: Chemical,Potentiometric, and Spectroscopic Methods

Humic acids (HA) and fulvic acids (FA) were extracted from tropical humid forest, tea garden, and field crop soils, and their chemical, potentiometric, and spectrophotometric properties were measured. There was less HA than FA in the cultivated soils. The HAs contained more carbon (C) and nitrogen (N) and had greater C/H ratios but lower O (oxygen)/H (hydrogen) ratios than FAs. Cultivated soils had greater total acidity than the forest soil generally because of both —COOH and phenolic-OH. Molecular weights of HA an FA, estimated from intrinsic viscosities, revealed that cultivation had reasonably reduced the molecular weights. The difference in pH (ΔpH) values, corresponding to three-fourths and one-fourth of the pH at final inflexion point showed that they were polyprotic. The longer time required for stability of greater pH of HAs was related to greater degree of stable coiling. The (E₄/E₆), in general, revealed a greater amount of aliphatic moiety rather than aromatic moiety.     

Chemical and physical characteristics of humic substances extracted from greek soils varying in classification order and natural drainage

Abstract

Humic and fulvic acids were extracted from the surface horizons of Alfisols, Vertisols, and Entisols with good and impeded natural drainage. These profiles are located in the temperate subhumid zone. The extracted humic substances were characterized by elementary and functional group analyses, IR‐spectroscopy, differential thermal analysis (DTA) and electron spin resonance spectroscopy (ESR). Some differences in the humic substances seem to be associated with differences in the natural drainage of the soils. When data from samples of the same soil order are compared, indicate that humic (HAs) and fulvic acids (FAs) extracted from soils with impeded drainage, have higher contents of carbon and spin concentration, but less total acidity and fewer carboxylic groups (COOH), than the respective humic substances extracted from well drained soils. The IR‐spectra of the HAs extracted from soils with impeded drainage showed more aliphatic groups than those of the well drained soils. No essential differences, which could be related to the drainage conditions of the studied soils, were observed in the IR‐spectra of FAs. DTA‐diagrams shows that the thermal stability of the HAs and the FAs are related to their carbon and ash contents. Iron was the dominant element in the ash of the humic acids, aluminum and silicon were the most abundant elements in the ash of the fulvic acids.     

菌剂对鸡粪堆肥腐殖质含量品质的影响

腐殖质是评价堆肥品质的重要因素,该文利用鸡粪和秸秆为原料进行高温好氧堆肥,设计接种菌剂和不接种菌剂(对照)2个处理,研究菌剂添加对堆肥腐殖质形态、含量、品质的影响。结果表明:与对照相比,接种菌剂可以加快有机物的降解,矿质化时间缩短14d,菌剂具有良好的保碳效果,总有机碳含量提高了16.1%,同时总腐殖酸、游离腐殖酸以及水溶态腐殖酸及胡敏酸的含量,分别提高了38.7%,45.7%、39.0%及54.9%。接种菌剂可以提高腐殖酸的活性,堆肥结束后,接种菌剂处理的游离腐殖酸和水溶性腐殖酸含量均增加,而对照处理的含量均降低;堆肥可以提高腐殖酸质量,堆肥结束后两个处理总腐殖酸含量均下降但是缩合度、腐殖化率、腐殖化指数及胡敏酸百分比均提高,特别是添加菌剂的处理腐殖化程度明显高于对照。说明了菌剂可以增加堆肥腐殖质含量,提高腐殖质缩合度、芳构化程度及活性。     

Long term effects of a brown coal-based amendment on the properties of soil humic acids

In this study a typical grey-brown podzolic soil was amended with different doses of a brown coal-based preparation called Rekulter (R) largely used in Poland. After seven years, soils were analyzed and humic acids (HAs) were extracted both from the control soil and from the amended soils. All HAs were characterized by Fourier transform infrared spectroscopy and fluorescence spectroscopy both in emission, excitation and synchronous-scan mode and as Excitation-Emission-Matrix (EEM) contour maps. A higher carbon content was observed in the amended soils whereas significant differences were highlighted between the unamended and the amended soil HAs. HAs from amended soils showed a higher content of carboxyl groups and a more aromatic character, particularly HA extracted from the soil amended with the highest dose of R.     

Effect of cultivated plants on physico‐chemical characteristics of humic substances of soils amended by sewage sludge

Abstract

Humic substances were extracted from raw sewage sludge samples as well as an alluvial slightly alkaline soil [Typic Xerofluvent (So)], a clay loam soil [Calcixerollic Xerochrept (M)] and the corresponding field plots amended with different rates of sewage sludge and cultivated with corn and cotton respectively, in a two‐year field experiment. These substances have been characterized by chemical and spectroscopic methods. The chemical analyses showed that humic acids (HAs) and fulvic acids (FAs), were effected by the cultivated plant. Humic substances extracted from field plots with cotton showed higher carbon, but less nitrogen (N), total acidity and carboxylic groups content, as compared with those under corn. Generally HAs and FAs extracted from the fields plots amended with sewage sludge had higher N content, lower values of total acidity, carboxylic groups and carbon contents than those from the unamended soils. The FT‐IR spectra of humic (HAs) and fulvic (FAs) acids extracted from sewage sludge indicated the presence of high percentage of aliphatic carbon, polysaccharides and proteinaceous materials. The spectra of the humic matter in the field plots showed less aliphatic but increased amide stretch in comparison with the sludge. The absorption due to C=O in carboxylic groups of the FAs was not pronounced, though the presence of polysaccharides and protein decomposition products was clearly indicated.     

Changes in forest soil organic matter quality affected by windstorm and wildfire

Purpose

Windthrows and fires are major natural disturbances in forest ecosystems, which can affect organic matter in the surface and the mineral layer of forest soil. The main aim of this study was to evaluate the changes occurring in the structure and properties of humic acid (HA) in the lands where windthrows and wildfires occurred.

Materials and methods

In November 2004, the forest in the area of 12,000 ha in the Tatra National Park, Slovakia, was seriously damaged by northern wind gusts exceeding 200 km/h. In July 2005, a wildfire broke out in a 220 ha of wind-damaged area. The HAs have been isolated from four research plots: (a) the area where the fallen trees were removed (EXT); (b) an area after windstorm covered by wood from struck trees (NEX), left for spontaneous succession; (c) an area after extracted timber, damaged by the surface wildfire (FIR); and (d) a reference intact spruce forest area (REF). Changes in the chemical structure of the HAs isolated from the research plots were determined on the basis of elemental analysis and UV-Vis, EPR, IR, and ¹³C NMR spectroscopy.

Results and discussion

All used analytical methods showed a decrease in the humification degree of the humic acids extracted from the soils where the spruce forest has been affected by a wildfire and a windthrow. In the case of the control sample HA (REF), the calculated atomic H/C and O/C ratios and the degree of aromaticity (α) calculated from the ¹³C NMR spectra were higher, indicating higher aromaticity of HA from the REF area. The more complex and developed structure of REF HA was confirmed by the higher value of E^1%₆ and the lower E4/E6 ratio obtained using UV-Vis spectroscopy. Also, the higher g-parameters determined from the EPR spectra of the stable radicals present in HA confirmed the lower aromaticity on the plots that have been subjected to the calamities. The ¹³C NMR spectra and the elemental analysis show that the structure of the HA extracted from the NEX plot is the closest to the REF.

Conclusions

The results of the systematic research showed significant changes in the structure of HA taken from spruce forest soils that were subjected to windstorms and fires. An enrichment of the HAs in aliphatic carbon and so a lower humification degree of the organic matter in the areas calamity-affected were observed. The results clearly indicate that the HAs extracted from the disturbed plots of the spruce forest are not as stable as those extracted taken from the control plot.

     

Inhibitory action of dissolved humic substances on the growth of soil bacteria degrading DDT

Abstract

Dissolved humic acid (HA) and fulvic acid (FA) prepared from a Dando brown forest soil (Typic Dystrochrept) inhibited the growth of soil bacteria degrading DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) in the culture. The population of DDT-degrading Gram-variable rod Bll6 decreased by the application of both HA and FA, suggesting the presence of bactericidal effect. Such inhibitory effect was stronger for HA and resulted in a lower degrading activity of DDT in the culture of Bll6. No inhibitory effect was observed on the growth of DDT-degrading Bacillus sp. B75. The electron spin resonance spectra showed the presence of organic free radicals in both HA and FA. The relative concentration of the radicals was higher in HA. Storage of HA solution for 3 months at 4°C decreased the concentration of the radicals as well as the inhibitory action. The addition of catalase decreased the inhibitory effect of humic acid. It is suggested that a hydroxy radical, which is derived from free radicals of humic substances, is involved in the inhibition of bacterial growth and degradation of DDT.