Formation Of Humic Substances Research Articles

Biostimulant Potential of Humic Acids Extracted From an Amendment Obtained via Combination of Olive Mill Wastewaters (OMW) and a Pre-treated Organic Material Derived From Municipal Solid Waste (MSW).

Olive mill wastewaters (OMW) contain significant levels of phenolic compounds with antimicrobial/phytotoxic activity and high amounts of undecomposed organic matter that may exert negative effects on soil biology. Among OMW detoxification techniques, those focusing on oxidative degradation of phenolic compounds are relevant. The composting (bio-oxidation) process in particular, exploits exothermic oxidation reactions by microorganisms to transform the organic matrix of OMW into an amendment biologically stable and feasible to use in agriculture. This process consists of an active phase during which organic compounds are rapidly decomposed, and a curing phase characterized by a slow breakdown of the remaining materials with the formation of humic substances (HS) as by-products. In this study, bio-oxidation of OMW was performed using a pre-treated organic material derived from municipal solid waste (MSW). The obtained amendment (OMWF) was stable and in accordance with the legislative parameters of mixed organic amendments. HS were then extracted from OMWF and MSW (control amendment, Amd-C), and differences in structural properties of their humic acid (HA) fraction were highlighted via spectroscopy (Fourier Transform Infrared) and Dynamic Light Scattering. To assay a potential use of HA as biostimulants for crops, 12-day old Zea Mays L. plants were supplied with HA at 0.5 mg and 1 mg C L-1 for 2 days. HA from both amendments increased plant growth, but HA from OMWF was more effective at both dosages (plus 35–37%). Also, HA from OMWF enhanced both nitrogen assimilation and glycolysis by increasing the activity of nitrate reductase (∼1.8–1.9 fold), phosphoglucose isomerase (PGI) (∼1.8–2 fold) and pyruvate kinase (PK) (∼1.5–1.8 fold), while HA from Amd-C targeted glycolysis preferentially. HA from OMWF, however, significantly stimulated plant nutrition only at lower dosage, perhaps because certain undetermined compounds from detoxified OMW and incorporated in HA altered the root membrane permeability, thus preventing the increase of nutrient uptake. Conversely, HA from Amd-C increased nutrient accumulation in maize at both dosages. In conclusion, our results indicate that the amendment obtained via OMW composting using MSW had a reduced pollution load in terms of phenolic compounds, and HA extracted from OMWF could be used as valuable biostimulants during maize cultivation.

Phototransformation of l-tryptophan and formation of humic substances in water

Humic substances are poorly known, though they represent a major pool of non-biotic organic carbon on earth. In particular, there is little knowledge on the formation of humic substances by irradiation of organic matter dissolved in waters. Specifically, it is known that humic substances can be formed from proteins by photochemical processes in surface waters, but the role of single amino acids and their transformation pathways are not yet known. Therefore, here we studied the phototransformation of aqueous l-tryptophan under simulated sunlight. Irradiated l-tryptophan solutions were analyzed by absorption, fluorescence, nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies, chromatography, potentiometry and mass spectrometry (MS). The solutions appeared turbid after irradiation; therefore, nephelometry and dynamic laser light scattering were used to characterize the suspended particles. Results show that about 95% of l-tryptophan was degraded in 8-h irradiation, undergoing deamination and decarboxylation of the amino acidic moieties to release ammonium and formate. The MS signal at m/z 146 suggests the formation of 3-ethylindole, while pH-metric and NMR data revealed the presence of hydroxylated compounds. The phototransformation intermediates of l-tryptophan had fluorescence and absorption spectra similar to those of humic substances, they were able to produce ·OH upon irradiation and tended to aggregate by both ionic and hydrophobic interactions. Overall, our findings reveal for the first time the nature of products formed upon phototransformation of l-tryptophan. Interestingly, the transformation of l-tryptophan is quite different from that of the previously studied l-tyrosine, although both compounds produce humic-like materials under irradiation.

Qualitative and quantitative soil organic matter estimation for sustainable soil management

PurposeThe aims of this paper were to review tools and methods for qualitative and quantitative evaluation of soil organic matter (SOM) coming from diverse egzogenic sources for effective soil management, and to introduce a new approach to predict dynamics of SOM transformations, especially humification, as a key process in the formation of humic substances (HSs).Materials and methodsA review of existing literature is presented on tools and methods for qualitative and quantitative assessment of organic matter in soil originating from various sources for reasonable soil management, attempting to provide a better understanding of the advances in organic matter transformations and new research directions for modeling. Diverse tools and methods for qualitative and quantitative evaluation of organic matter in soil coming from diverse sources have been adopted so far to express transformation processes.Results and discussionFor the qualitative analysis of SOM and humic acids (HAs), the analytical techniques are applied, e.g., HPSEC, NMR, and ESI-FTICRMS. The quantitative analysis is done through the following parameters: humification index (HI), humification degree (HD), and humification rate (HR). These analyses indicated that because of lack of reliable data from sufficiently long-term experiments, mathematical modeling may be applied as a numerical tool for quantitative estimation and prediction of humification of SOM. The effective soil management should include soil properties as well as different functions: food production, nutrient and water cycling, storage, filtrating, buffering, biological habitat, gene pool, source of raw materials, climate regulations, heritage, platform for man-made structure. The soil utility value should be evaluated through the SOM qualitative and quantitative analysis of organic carbon and total nitrogen. Knowledge about dynamics of SOM transformations is essential, particularly in the context of stability and efficiency of different sources of organic matter applied into soil. A qualitative understanding of SOM dynamics transformations along with modeling for quantitative assessment of HS formation should be used to develop sustainable soil management. The modeling may be considered as a tool for predicting SOM humification dynamics and consequently the formation of HSs from the diverse sources. The existing archival data from a long-term experiment may be used to build and calibrate the reliable mathematical model of SOM humification.ConclusionsManaging of SOM remains a sound basis for maintaining soil in a good condition for optimizing productivity. The development of land management strategies to optimize both the increase of soil organic carbon levels and the recycling of nutrients from SOM needs to be a priority. This should include policy makers and other users as well.

Molecular changes of aquatic humic substances formed from four aquatic macrophytes decomposed under different oxygen conditions

ABSTRACTAquatic macrophytes’ decomposition is a source of recalcitrant carbon in the long term contributing to humic substances (HS) formation. Understanding the influence of plant detritus quality and oxygen availability over molecular changes of these compounds provides ecological information related to their cycling. This study described the molecular variation of dissolved HS from Eichhornia azurea, Egeria najas, Oxycaryum cubense and Salvinia molesta decomposition under aerobic and anaerobic conditions. The aquatic HS formed from the four aquatic macrophytes showed similar features (e.g. molecular weight and aromaticity). This fact indicates little influence of the detritus quality or availability of oxygen on the fulvic acids (FA) and humic acid characteristics. Under aerobic condition a decrease in the polysaccharides content in FA occurred. HS from E. najas were related to less-recalcitrant features, while HS from S. molesta were related to recalcitrant.

Influence of humic substances and iron and aluminum ions on the sorption of acetamiprid to an arable soil

Humic substances (HS) in soil and sediments, and surface water influence the behavior of organic xenobiotics in the environment. However, our knowledge of the effects of specific HS fractions, i.e., humic acids (HAs), fulvic acids (FAs), and humin (HM), on the sorption of organic xenobiotics is limited. The neonicotinoid insecticide acetamiprid is thought to contribute to the collapse of honeybee colonies. To understand the role that soil organic matter plays in the fate of acetamiprid, interactions between acetamiprid and the above HS fractions were examined. Batch experiments were conducted using various combinations of a field soil sample and the above 3 HS fractions prepared from the same soil, and differences in isotherm values for acetamiprid sorption were investigated based on the structural differences among the HS fractions. The sorption of acetamiprid to soil minerals associated with HM (MHM) (Freundlich isotherm constant, Kf: 6.100) was reduced when HAs or FAs were added (Kf: 4.179 and 4.756, respectively). This can be attributed to hydrophobic interactions between HM and HAs or FAs in which their dissociated carboxyl and phenolic groups become oriented to face the soil solution. The amount of acetamiprid that was adsorbed to (MHM+HA) or (MHM+FA) increased when aluminum ions were added (Kf: 6.933 and 10.48, respectively), or iron ions were added (Kf: 7.303 and 11.29, respectively). Since acetamiprid has no affinity for inorganic components in soil, the formation of HS–metal complexes by cation bridging may have oriented the hydrophobic moieties in the HAs or FAs to face the soil solution and may also have resulted in the formation of dense structures, resulting in an increase in the amount of acetamiprid that becomes adsorbed to these structures. These results highlight the importance of interactions among soil components in the pedospheric diffusion of acetamiprid.

Formation of organic substances of humus nature and their biospheric properties

Hypotheses of humus formation on the basis of polymerization and oxidation reactions were considered. The most popular models of several authors and the general understanding of the structural features of natural polymers were analyzed. Multivariate statistical analysis was performed for zonal factors affecting the formation of humic substances. Evolutionary changes in the understanding of the biospheric functions of humus substances were evaluated. Statistical procedures were proposed for the prediction of the physicochemical behavior of humus substances in environments.

Identifying the key factors that affect the formation of humic substance during different materials composting

The aim of this work was to identify the factors which can affect humic substance (HS) formation. Composting periods, HS precursors, bacteria communities and environment factors were recognized as the key factors and few studies explored the potential relationships among them. During composting, HS precursors were mainly formed in the heating and thermophilic phases, but HS were polymerized in the cooling and mature phases. Moreover, bacterial species showed similar classification of community structure in the same composting period of different materials. Furthermore, structural equation model showed that NH4−-N and NO3−-N were the indirect environmental factors for regulating HS formation by the bacteria and precursors as the indirect and direct driver, respectively. Therefore, both environmental factors and HS precursors can be the regulating factors to promote HS formation. Given that, a new staging regulating method had been proposed to improve the amount of HS during different materials composting.

Effect of thermo-tolerant actinomycetes inoculation on cellulose degradation and the formation of humic substances during composting

The inoculum containing four cellulolytic thermophilic actinomycetes was screened from compost samples, and was inoculated into co-composting during different inoculation phases. The effect of different inoculation phases on cellulose degradation, humic substances formation and the relationship between inoculation and physical–chemical parameters was determined. The results revealed that inoculation at different phases of composting improved cellulase activities, accelerated the degradation of cellulose, increased the content of humic substances and influenced the structure of actinomycetic community, but there were significant differences between different inoculation phases. Redundancy analysis showed that the different inoculation phases had different impacts on the relationship between exogenous actinobacteria and physical–chemical parameters. Therefore, based on the promoting effort of inoculation in thermophilic phase of composting for the formation of humic substances, we suggested an optimized inoculation strategy to increase the content of humic substances, alleviate CO2 emission during composting.

Fertilizer for the Treatment of Iron Chlorosis Physico-chemical and agro-chemical properties

Iron chlorosis represents a physiological phenomenon with negative impact on the quality and quantity of grape production in the vineyards. The bicarbonates are considered to be the main group of compounds which immobilize the iron in the soil in forms not assimilable by the plants. The grape production in conditions of iron deficiency can be improved significantly by applying foliar fertilizers. The best result in mitigating the effects of iron deficiency were obtained by the application of the fertilizers which, in addition to a complex mineral composition, also have a content of organic matter in the form of humic substances or protein hydrolysate.

Effect of precursors combined with bacteria communities on the formation of humic substances during different materials composting

The aim of this work was to put forward a method to improve HS amount by studying the formation regularity of HS. Five precursors have been detected and few researches combined them with bacteria to study HS formation. During composting, the polyphenols, carboxyl and amino acids concentration decreased by 75.8%, 63.2% and 68.3% on average, respectively. However, the polysaccharides, reducing sugars and HS concentration increased by 61.2%, 47.1% and 37.33% on average. Relationships between precursors and HS concentration showed that the HS formation were significantly affected (p<0.05). The key bacteria community and physical–chemical parameters which affected HS formation have also been identified by redundancy analysis. Twelve key bacteria communities have been selected, which were significantly affected by physical–chemical parameters (p<0.05). Accordingly, we proposed an adjusting method to promote HS amount during composting based on the relationship between the key bacteria communities and the precursors as well as physical–chemical parameters.

Humic dissolved organic carbon drives oxidative stress and severe fitness impairments in Daphnia

Increases in dissolved organic carbon (DOC) in the form of humic substances, causing browning of surface water, have been reported worldwide. Field surveys indicate that higher DOC levels can influence primary production and thus plankton composition. Experimental studies on the direct effects of humic DOC on aquatic organisms have shown varying results depending on concentration and additional environmental factors. Moreover, changes in life-histories and stress responses have usually been tested separately, rather than in combination. We experimentally tested the impact of a sudden increase in humic DOC on two species of the zooplankton cladoceran Daphnia, across several levels of biological organisation, from cellular to population responses. In D. magna, strong impacts on reproduction (delayed maturity and reduced number of offspring) were coupled with overall stress induction (increases in antioxidant capacity and oxidative damage, combined with a reduced amount of available energy). In D. longispina, increased mortality and lowered fecundity were observed. We conclude that a strong input of humic DOC into aquatic systems can have severe negative impacts on zooplankton species, and has the potential to alter zooplankton community structures.

In Situ IR Transmission Spectroscopic Observation and Kinetic Analyses of Initial Stage of the Maillard Reaction as a Simulated Formation Process of Humic Substances

The Maillard reaction is one of the dominant processes forming humic substances in natural waters affecting environmental pollution. In this study, we succeeded in quantitatively following decreases of starting materials (glycine and ribose) of the Maillard reaction by in situ infrared (IR) transmission spectroscopic observations with an original heatable liquid cell. The obtained kinetic parameters extrapolated to a typical Earth’s surface aquatic environments (15 °C) indicate the half-life of around 2 years for the decrease of these components as the first step for the formation of humic substances.

Biotransformation of organic matter during composting of solid wastes from traditional tanneries by thermochemolysis coupled with gas chromatography and mass spectrometry

In the present paper, Thermochemolysis (or Thermally Assisted Hydrolysis/Methylation) is used as a way of following the biotransformation of organic matter during composting of solid wastes from traditional tanneries. The qualitative analysis of the pyrograms allowed us to discriminate between four main families of compounds: aromatic compounds, lipids, polysaccharides and nitrogen-containing substances. The quantitative data revealed some variations in the chemical composition of the macromolecular content.Lipids are the most transformed fraction during the composting process. Animal and plant fatty acids showed a sensible decrease. Fungal fatty acids mainly increased during the thermophilic phase whereas bacterial fatty acids increased when the growth of fungi is repressed. During composting of solid wastes from traditional tanneries an adapted microbial community has been developed. Various lignin-derived units during composting showed a strong increase in p-hydroxyphenyl type-compounds in comparison with the other aromatic structures due to high decomposition of grass cuttings. Tannin derived compounds also increased throughout the composting. Lignin and condensed tannins polymers are partially degraded and stabilized by covalent linkage to more complex organic molecules such as humic substances.Nitrogen containing compounds increased during composting as a consequence of the high rate of degradation of the other fractions and/or their combination with polyphenolic structure leading to the formation of humic substances. In our study a correlation was found between NTK and nitrogen containing substances.

Interactions of the products of oxidative polymerization of hydroquinone as catalyzed by birnessite with Fe (hydr)oxides – an implication of the reactive pathway for humic substance formation

In this study, we aimed to determine the products of oxidative polymerization of hydroquinone with and without catalysis by birnessite, and investigate the adsorption kinetics of the HQs on Fe (hydr)oxides upon their formation.

Transformações químicas dos ácidos húmicos durante o processo de vermicompostagem de resíduos orgânicos

RESUMO A produção de resíduos orgânicos durante os processos agroindustriais é um problema tanto ambiental quanto econômico devido às características químicas desses resíduos. Geralmente, resíduos orgânicos estabilizados servem como condicionadores de solos. Esses resíduos podem afetar tanto na composição química quanto nas características das cargas trocáveis dos solos. O objetivo deste trabalho foi avaliar a formação de substâncias húmicas (SH) durante a vermicompostagem em diferentes resíduos agroindustriais, bem como caracterizar a composição química e molecular. Assim, diferentes resíduos - esterco bovino (EB), esterco ovino (EO), restos de alimentos de restaurantes (RA), lodo de arroz parboilizado (LP), restos de frutas e vegetais (RF) - foram submetidos à vermicompostagem. Amostras desses materiais foram secas, trituradas e caracterizadas quimicamente quanto a pH, carbono (C) orgânico, N total, Ca, Mg, K, P, relação C/N, e condutividade elétrica (CE) antes, durante e depois do processo de vermicompostagem. Além disso, foi analisado o fracionamento da matéria orgânica como as SH, análise elementar e espectroscopia de infravermelho. De acordo com o processo de vermicompostagem dos resíduos agroindustriais, o carbono orgânico total (COT) e os ácidos fúlvicos (AF) foram reduzidos; contudo, os ácidos húmicos (AH) aumentaram proporcionalmente. Dentre os vermicompostos estudados diferiram quanto à proporção final de SH formadas decrescendo na sequência: EB&gt;RF&gt;EO&gt;RA&gt;LP. Isso demonstra uma estabilização dos compostos orgânicos por meio da vermicompostagem, podendo, consequentemente, ser utilizados com uma maior segurança na agricultura.

Destruction of molecular compounds in gaseous and liquid medium in microwave discharge plasma

The paper presents the results of experimental studies of molecular destruction in gaseous and liquid medium using microwave discharge plasma at atmospheric pressure. As the gas medium hydrocarbon gas is used, the liquid medium were aqueous solutions of methylene blue and more complex organic compound in the form of humic substances. As a result of the destruction of hydrocarbon gas molecules in microwave discharge plasma new products such as hydrogen, ethylene, acetylene and carbon nanostructured material have been formed. In experiments on destruction of molecular compounds in aqueous organic solutions we used air, nitrogen and argon for plasma gases. It is shown that the process of molecular destruction in aqueous organic solutions in the microwave discharge plasma is based on oxidation-reduction reactions. It is found that the maximum efficiency of removal of organic compounds from the solution occurs when using air as the plasma gas.

Effect of composting on the production of syngas during pyrolysis of perennial grasses

Abstract The effect of composting on the production of syngas, a mixture of hydrogen (H 2 ) and carbon monoxide (CO) with an explicit H 2 /CO = 2 or H 2 /CO = 3 during pyrolysis of six non-hybrid grasses (NHG) and three hybrid grasses (HG) was investigated. The pyrolysis experiments were conducted in a fixed bed reactor to a final temperature of 700 °C. The experimental results obtained in this study demonstrated that composting changed the composition of biomass, significantly reduced the content of carbon dioxide (CO 2 ) and made H 2 and CO the primary constituents of pyrolysis gas. A significant increase in syngas concentration and a higher heating value (HHV), followed by a decrease in the temperature at which a specific H 2 /CO was reached, was observed due to composting as well. The change was associated with thermal decomposition of biochemical components, formation of humic substances, and secondary reactions of char.

Carbon pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes

Landfill aeration has been proven to accelerate the degradation of organic matter in landfills in comparison to anaerobic decomposition. The present study aims to evaluate pools of organic matter decomposing under aerobic and anaerobic conditions using landfill simulation reactors (LSR) filled with 40year old waste from a former MSW landfill. The LSR were operated for 27months, whereby the waste in one pair was kept under anaerobic conditions and the four other LSRs were aerated. Two of the aerated LSR were run with leachate recirculation and water addition and two without. The organic carbon in the solid waste was characterized at the beginning and at the end of the experiments and major carbon flows (e.g. TOC in leachate, gaseous CO2 and CH4) were monitored during operation. After the termination of the experiments, the waste from the anaerobic LSRs exhibited a long-term gas production potential of more than 20NLkg−1 dry waste, which corresponded to the mineralization of around 12% of the initial TOC (67gkg−1 dry waste). Compared to that, aeration led to threefold decrease in TOC (32–36% of the initial TOC were mineralized), without apparent differences in carbon discharge between the aerobic set ups with and without water addition. Based on the investigation of the carbon pools it could be demonstrated that a bit more than 10% of the initially present organic carbon was transformed into more recalcitrant forms, presumably due to the formation of humic substances. The source of anaerobic degradation could be identified mainly as cellulose which played a minor role during aerobic degradation in the experiment.

Effect of &lt;i&gt;Phanerochaete chrysosporium&lt;/i&gt; on the Characteristics of Humic Substances during Composting of Agricultural Wastes

The effect of Phanerochaete chrysosporium (Pc) on the characteristics of humic substances (HS) was investigated during composting of agricultural wastes. The dynamic changes of HS, fulvic acid (FA), humic acid (HA) and the humification index (HI) were monitored during a 60-day composting. The results showed that the formation of FA was not obviously influenced, while HA formation was improved by the inoculum of Pc. During the composting process, HI increased from 0.28, 0.29 to 2.23 and 3.17 in the control and the treatment, respectively. This result indicated that Pc could significantly enhance the degree of HS aromatization (P&lt;0.05). This research helps to know the contribution of Pc to the formation of HS during composting and provide some useful information for the development of efficient methods to increase the content of HS in the composting.

Photochemical generation of photoactive compounds with fulvic-like and humic-like fluorescence in aqueous solution

The irradiation of L-tryptophan, L-tyrosine and 4-phenoxyphenol in aqueous solution produced compounds with similar fluorescence properties as humic substances, and with absorption spectra that were significantly extended into the UVA and visible regions compared to the starting compounds. The irradiated systems had photosensitizing properties, as proven by the photodegradation of 2,4,6-trimethylphenol and furfuryl alcohol (probes of excited triplet states and 1O2, respectively). The described photochemical processes could constitute an additional pathway for the formation of humic substances in clear and shallow water bodies, which would be added to the complex network of reactions involving dissolved organic matter.