Solutions Of Humic Substances Research Articles

The structure of humates in aqueous solutions and their biological activity

When studying humate solutions, it is often not taken into account that humic substances (HS) can form supramolecular formations (SMFs) from molecular particles. These SMFs are highly stable, that is, the particles-molecules of HS do not separate from them spontaneously. It follows that at concentrations of the existence of SMFs, it is they, and not the particles-molecules of HS, that should be in solutions and determine their properties. The purpose of the study is to assess the influence of the form of existence of HS in solutions on their physico-chemical properties and biological activity. Solutions of sodium humate from brown coal were used in the work. The experimental results showed that with an increase in the concentration of humates, an abrupt increase in pH in the range of 30–50 mg l⁻¹ is observed. These concentrations correspond to the literature data on changes in the structure of HC in solutions: at concentrations above 30 mg l⁻¹ – barrier concentration – HS molecules form SMFs by self-assembly. Both molecular particles and SMFs, due to the diphilicity of HS, have the properties of surfactants. That is, in solutions at the interface of the “water–air” phases, HS films form. The strength of the films depends on the size of its constituent particles and the speed of their movement from the thickness to the surface of the solution. When plotting graphs in the coordinates “Film formation time in hours–Log humate concentration, mg l⁻¹”, a jump corresponding to the barrier concentration was detected on the curves. It was also found that during foliar treatment of cucumber shoots with mechanoactivated humate solutions with concentrations below the barrier, the stimulation effect increases, apparently due to the transition from the existence of HS in solution in the form of SMFs to existence in the form of particles-molecules that, due to their small size, can penetrate plant cells.

Environmental condition-dependent effects of aquatic humic substances on the distribution of phenanthrene in microplastic-contaminated aquatic systems

Numerous studies have focused on the interaction between microplastics (MPs) and phenanthrene (PHE) in aquatic environments. However, the intricate roles of aquatic humic substances (HS), which vary with environmental conditions, in influencing PHE-MP interactions are not yet fully understood. This study investigates the variable and environmentally sensitive roles of HS in modifying the interactions between PHE and polyethylene (PE) MPs under laboratory-simulated aquatic conditions with varying solution chemistry, including pH, HS types, HS concentrations, and ionic strength. Our findings show that the presence of HS significantly reduces the adsorption of PHE onto both pristine and aged PE MPs, with a more pronounced reduction observed in aged PEs. This effect is highlighted by a notable decrease in the partitioning coefficient (Kd) of PHE, which falls from 2.60 × 104 to 1.30 × 104 L/kg on MPs in the presence of HS. The study also demonstrates that alterations in the net charge of HS solutions are crucial in modifying PHE distribution onto PEs. An initial decrease in Kd values at higher pH levels is reversed when HS is introduced. Furthermore, an increase in HS concentrations is associated with lower Kd values. In conditions of higher ionic strength, the retention of PHE by HS is intensified, likely due to an enhanced salting-out effect. This research highlights the significant role of aquatic HS in modulating the distribution of PHE in MP-polluted waters, which is highly influenced by various solution chemistry factors. The findings are vital for understanding the fate of PHE in MP-contaminated aquatic environments and can contribute to refining predictive models that consider diverse solution chemistry scenarios.

HUMIC SUBSTANCES OF PEAT. PROPERTIES AND BIOLOGICAL ACTIVITY

Humic substances (HS) are a specific group of high-molecular biopolymers that are formed during the decomposition of plant and animal tissue. It has been established that humic substances have a wide range of biological properties, in addition, humic substances are quickly included in the processes of plant metabolism, which accelerates the development of the root system, increases resistance to adverse environmental factors. But to date, the nature of this phenomenon has not been studied enough. To deepen our understanding of the biological and growth-stimulating activity of humic substances, the influence of prepared solutions with different concentrations of humic substances on seed germination is considered. It has been shown that solutions of humic substances have a beneficial effect on seeds even in small concentrations.
 This research work is devoted to the study of the main functional groups of humic substances, such as carboxylic, phenolic, quinoid. Various physico-chemical methods were used in the work to determine the functional and elemental composition of peat HS.
 It has been established that peat HS have a stimulating effect and high physiological activity on the growth and biometric indicators of plants, which in the future can determine the increase in yield and quality of agricultural plants.

In Situ Visualization of Membrane Fouling Evolution during Ultrafiltration Using Label-Free Hyperspectral Light Sheet Fluorescence Imaging.

Profound understanding of fouling behaviors and underlying mechanisms is fundamentally important for fouling control in membrane-based environmental applications. Therefore, it entails novel noninvasive analytical approaches for in situ characterizing the formation and development of membrane fouling processes. This work presents a characterization approach based on hyperspectral light sheet fluorescence microscopy (HSPEC-LSFM), which is capable of discriminating various foulants and providing their 2-dimensional/3-dimensional spatial distributions on/in membranes in a label-free manner. A fast, highly sensitive and noninvasive imaging platform was established by developing a HSPEC-LSFM system and further extending it to incorporate a laboratory-scale pressure-driven membrane filtration system. Hyperspectral data sets with a spectral resolution of ∼1.1 nm and spatial resolution of ∼3 μm as well as the temporal resolution of ∼8 s/plane were obtained, and the fouling formation and development process of foulants onto membrane surfaces, within the pores and on the pore walls were clearly observed during the ultrafiltration of protein and humic substances solutions. Pore blocking/constriction at short times while cake growth/concentration polarization at longer times was found to have coupled effects for the flux decline in these filtration tests, and yet the contribution of each effect as well as the transition of the governing mechanisms was found distinct. These results demonstrate in situ label-free characterization of membrane fouling evolution with the recognition of foulant species during filtration and provide new insights into membrane fouling. This work offers a powerful tool to investigate dynamic processes for a wide range of membrane-based explorations.

HUMIC SUBSTANCES AND THE MECHANISM OF THEIR INFLUENCE ON THE PRODUCTION OF HIGHER GREEN PLANTS

The latest research proposed a new point of view about the material composition of so-called 'humic substances,' isolated from natural objects (soils, peats, sapropels, and composts) by alkaline solutions, and presented the conceptual model of direct influence of 'humic substances' on biochemical and biophysical processes into plants. 'Humic substances' are essentially black liquor, i.e., a product artificially obtained because of the alkaline hydrolysis of organic material from natural objects. Black liquor consists of a complex mixture of a variety of organic compounds. According to the proposed model, the biological activity of black liquor connects with accelerating the circulation of nutrients within plants, increasing the permeability of cell membranes, exhibiting de-toxicological properties, optimizing the ratio of organic and mineral anions in plants, and using some HS components as organic nutrients, inducing gene expression. Therefore, humic substances solutions have multifaceted effects on green vascular plants due to their direct influence on biochemical and biophysical processes.

The use of brown coal in Ukraine to obtain water-soluble sorbents

Purpose. To develop a method of using salts of humic acids obtained from brown coal of Ukraine for sorption of heavy metal ions and their extraction using ultrafiltration membranes. Methodology. Unique laboratory equipment has been developed to determine the sorption capacity of humic substances with a concentration of 0 to 20 mg/l in relation to heavy metal ions (Cu2+, Pb2+, Cd2+, Hg2+, Zn2+, Co2+) with a concentration of 5 mg/l. The results of proximate and ultimate analyzes, as well as infrared and optical emission spectroscopy were used to assess the quality of brown coal, humic substances and the solution of humic substances with heavy metal ions. Findings. Ukrainian brown coal of Oleksandriia geological-industrial district contains a large amount (about 80%) of humic acid, which is the basis for obtaining effective water-soluble sorbents. It is proved that humic substances obtained from brown coal of Ukraine allow binding up to 99% of heavy metal ions in complexes. The most optimal concentration of humic substances in terms of their concentration and selectivity of heavy metal ions extraction is 5 mg/l. Originality. The possibility of practical using of humic substances obtained from brown coal of Ukraine for sorption of heavy metal ions has been proved. As ultrafiltration membranes, UF-20-PAN membranes are used, which are porous polymer films based on polyacrylonitrile with a pore size of 20 m, the working surface area of the membrane is 28.26 10-4 m2. Practical value. The introduction of the developed technology will allow, firstly, restoring the practical use of large deposits of brown coal in Ukraine, and secondly, introducing deep treatment of industrial and wastewater.

MECHANOCHEMISTRY OF LIQUID-PHASE OXIDATIVE AMMONOLYSIS OF NATURAL RAW MATERIALS

The article provides a brief overview of works on the production of nitrogen-containing organic fertilizers based on lignin-carbohydrate products. It has been shown that liquid-phase oxidative ammonolysis of plant raw materials is an effective method. Chemical transformations of the main components of lignin-carbohydrate products during oxidative ammonolysis under mechanochemical action, which are based on the cavitation of mechanical activation, have been studied by the authors of the article. Economically feasible and environmentally safe technology of obtaining solutions of humic substances to use as organic raw materials any types of peat has been created. Liquid humic fertilizers production unit "Lignovit" has been developed and tested.

НАНОКОМПОЗИТИ СРІБЛА НА ОСНОВІ СИНТЕТИЧНИХ ГУМІНОВИХ РЕЧОВИН ЯК ВИСОКОЕФЕКТИВНІ СТИМУЛЯТОРИ РОСТУ РОСЛИ

Introduction. Nanotechnology have positive impact in improving many sectors of economy including agriculture. Silver nanoparticles (AgNPs) have been implicated nowadays to enhance seed germination, plant growth, improvement of photosynthetic quantum efficiency and as antimicrobial agents to manage plant diseases.Despite the known growth-stimulating activity of preparations of humic substances and silver nanoparticles, there is currently no information on the effect on growth processes of composites containing silver nanoparticles encapsulated in macromolecules from synthetic humic substances. It is expected that such combined nanopreparations have enhanced and complementary properties of a metal core and a shell of humic synthetic substances.Purpose. The aim of this study was to investigate the growth-stimulating activity of silver nanocomposites based on synthetic humic substances derived from quercetin, and to determine the range of active concentrations in the process of germination of wheat seeds.Methods. The received silver nanoparticles are characterized by UV–visible spectroscopy, X-ray diffraction (XRD), FT-IR spectroscopy and transmission electron microscopy (TEM). To study the growth-stimulating activity of synthetic humic substances and silver nanocomposites, a series of solutions was prepared on their basis by dilution with a logarithmic decrease in concentration from 1·10–1 to 4·10-16%.Result. Nanobiocomposites containing silver nanoparticles and synthetic humic substances were synthesized in the reaction of reduction of silver ions with synthetic humic substances obtained in laboratory conditions from quercetin.Preference of synthetic humic substances over natural humic substances is determined by a standardization problem resolution due to the strict control of conditions of the HS formation that expands the areas of application of the silver nanoparticles made on their basis. The high crystallinity of nanobiocomposites with fcc phase is evident from XRD patterns. The TEM results show that the silver nanoparticles are spherical in shape with average size about 9.6 nm. The FTIR spectroscopic study confirmed that the synthetic humic substances have ability to perform dual functions of reduction and stabilization of silver nanoparticles.The growth-promoting activity of synthetic humic substances and silver nanocomposites based on them was studied on the example of germination of wheat seeds of the variety "Zolotokosa" according to standard procedures. It is established that aqueous solutions of synthetic humic substances and silver 54 Серія «Біологічні науки», 202 2nanocomposites based on them in a wide range of concentrations have a complex effect on the growth and development of wheat seeds. It is shown that seed germination increases (by 2–40%) and the length of the main root (by 9–100%) of wheat germ increases. It should be noted that synthetic humic substances and silver nanocomposites based on them to a greater extent stimulate root growth, which is important for agriculture in arid areas. The ranges of effective concentrations of solutions of the studied drugs show the maximum total stimulating activity (by the number of germinated seeds and the length of the main root compared to the control) during germination of wheat seeds for synthetic humic substances and for silver nanocomposite - 10-10-10-4%. Stimulation of root growth by silver nanocomposites based on synthetic humic substances in most concentrations exceeds the effect of the original humic substances.Originality. The established activity of synthetic humic substances and silver nanocomposites based on them is a prerequisite for the further development of highly effective growth-stimulating preparations of a new generation.Conclusion. It has been established that silver nanocomposites based on synthetic humic substances exhibit highly effective growth-stimulating activity. The ranges of active concentrations of the studied preparations demonstrate the optimal stimulating activity for synthetic humic substances and silver nanocomposite based on them by the number of germinated seeds 1·10–10–1·10–4 %, by the length of the main roots compared to the control - 1· 10-12-1· 10-4%. The established activity of synthetic humic substances and silver nanocomposites based on them is a prerequisite for the further development of highly effective growth-stimulating preparations of a new generation.Key words: synthetic humic substances; silver nanocomposites; growth-promoting activity; wheat

Comparative Study of Sample-Preparation Techniques for Quantitative Analysis of the Mineral Composition of Humic Substances by Inductively Coupled Plasma Atomic Emission Spectroscopy

Five sample-preparation techniques were compared to quantify 31 elements in coal humic substances (HS) by ICP–AES from the viewpoints of complete isolation and speciation of elements. They include, for bulk composition, preparation of an aqueous colloidal HS solution followed by direct injection of the sample without decomposition and ashing followed by metaborate fusion; for element speciation, preparation of an aqueous colloidal HS solution followed by centrifugation and direct analysis without decomposition for water-soluble species; treatment with boiling nitric acid; and microwave-assisted treatment with nitric acid at 250 °C for acid-isolated species. The results of analysis significantly depend on the selected method of sample preparation due to specific features of HS, the simultaneous presence of many inorganic components in wide concentration ranges, and a significant fraction of the organic matrix; therefore, the total mineral composition of HS, both macro- and microcomponents, requires a combination of decomposition methods.

Assessing the potential of biochar aged by humic substances to enhance plant growth and soil biological activity

BackgroundSoil carbon-rich organic amendments (biochar, humic substances) may improve the quality and fertility of arable soil. Their co-application can additively enhance the beneficial effect on soil. Hypothetically, the pre-treatment of biochar, by aging via soaking in a solution of commercially available humic substances, could result in synergism, which may exceed the benefit from simple co-application of both amendments to the soil. Therefore, the aim of this study was to investigate the impact of biochar, humic substances, the combination of both, and the impact of biochar aged by humic substances solution on soil microbial activities and plant growth in a short-term pot experiment with lettuce.ResultsThe aging of biochar decreased the C:N ratio as compared to non-activated biochar. The co-application of biochar and humic substances into the soil resulted in the highest microbial biomass carbon and respiration activity. The majority of enzyme activities (β-glucosidase, arylsulfatase, N-acetyl-β-d-glucosaminidase, phosphatase) were the highest in humic substances-amended soil. The application of humic substances and biochar with humic substances seemed to stimulate microbial growth and activity followed by the competition of microflora for nutrients with plants, whereas the aged biochar behaved differently. The plants treated by aged biochar achieved the highest values of dry aboveground and root biomass of all variants. However, the assumed rapid uptake of nutrients by plants resulted in lower nutrient availability for microflora, and a decline in microbial viability.ConclusionsBased on this study, the positive effect of co-applied humic substances and biochar on soil fertility, quality, and health can be concluded. The usability of biochar aging by humic solution requires further study.Graphic abstract

Humic Substances Effect and Climatic Tensions on the Growth and Essential Oil Quality of the Cultivated Aloysia. triphylla (Iran)

Aloysia. triphylla (L, H, er.) Britton (Family Verbenaceae) is studded for nutritional and pharmacological purposes. Soil factors and climatic tensions affect the growth of the herbs. A. triphylla plants were planted in the University greenhouse (Zahedan) in March. Humic substances solutions were sprinkled onto the soil surrounding the root of the plant. This way of planting simultaneously was repeated in the Zahedan outskirts and Zarand area. In late June, the leaves of planted samples were collected and prepared for senescing through the hydrodistillation method. After collecting leaves and be sprinkled with humic substances solution onto the soil surrounding root of the same plant, the leaves were picked up again in late September for oil extraction. Oil yields (w/w%) of the greenhouse's June samples were 0.45 and 0.48 for the blank and humic samples respectively. By analyzing oils, using GC & GC-MS techniques, 47 and 46 compounds were identified from the blank sample and humic sample oils, constituting 93.21% and 91.58% respectively. The higher percent of which: limonene, 1, 8-cineole, Z-citral, E-citral, bicylogermacrene, trans-caryophyllene, panthenol compounds. Oxygenated terpenoids percentage in the humic sample oils varies between 43.70 and 60.16 of which 43.70 belongs to the oil of Zarand September humic sample (Sapropel) and 60.16 to the oil of the greenhouse's June humic sample (Sapropel). Oxygenated terpenoid compounds in September samples were less than those of June samples. These changes result from humic substances and climatic tensions. As a result, the flowering period is shortened and the oil quality has been optimized.

Development and Validation of a Spectrophotometric Method in the UV-Vis Region to Evaluate the Interactions of Estrogens with Humic Substances in an Aqueous Environment

Natural and synthetic sex hormones are potent endocrine disruptors (EDs) that have been detected in aquatic environments on all continents. Studies show that humic substances (HS) are the main compounds capable of interacting with hormones, interfering in the bioavailability processes. In the present work, a methodology based on the colorimetric properties of the azo-compounds was developed and validated using diazotized sulfanilamide as a reagent to study the interactions with HS of estrogens: estrone (E1), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2). As an alternative method to quantify hormones during interactions, ultraviolet-visible molecular absorption spectroscopy was employed. An analytical curve was constructed for concentrations ranging from 10.0 to 28.0 μg mL -1 . The results were compatible with chromatography, also applied in this work. For the study of the interaction, samples of the hormone standard and HS solution were used under constant agitation. The reduction in the concentration of estrogens has been detected since the beginning of the process, with EE2 being the best result. In the aliquot removed from the system after 48 hours of agitation, 51.1% EE2 was removed in the presence of 10.0 μg mL -1 of the HS and 75.8% at 20 μg mL -1 . Simulations can predict the behavior of hormones in natural aquatic environments rich in HS. DOI: http://dx.doi.org/10.17807/orbital.v13i2.1546

Comparative Study of Biostimulant Properties of Industrially and Experimentally Produced Humic Substances

Demand for new biological technologies in agriculture is ever growing, particularly with respect to the need of restoring the soil organic matter and soil fertility. Products of natural origin are developed to stimulate plant growth and productivity. Humic substances (HS) are the decay products of living matter, with high molecular weight and complex structure. Nowadays, HS are industrially produced from various materials like peat, lignin, soil and compost. The objective of this study is to make a comparison of the impact of HS of different origin on plant development. In total, eight different HS were used; four were extracted from various materials and four were commercially available products. To evaluate the stimulating effect, three different species of plants were used (Triticum aestivum, Sinapis alba, Lepidum sativum). The tests were carried out on Phytotestkit plates, germinating the seeds in different solutions of HS in various concentrations in dark, with or without added nutrient solution. Then, the growth parameters were measured. All tested products showed increase in at least some concentrations compared with the control sample. Significant differences in the stimulating effect of HS depending on their origin were found.

Influence of Humic Substances on Cucumber Seeds Storability and Root Rot Diseases Incidence under Salinity Conditions

Seed germination is a complex process, which is regulated by many factors including storage. The present study aims at assessing the validity of stored cucumber seeds under stressed-soil. In-vitro experiment was conducted to investigate the influence of soaking of stored cucumber (Cucumis sativus L.) seeds produced during three consequent years (2015, 2016 & 2017) in five concentrations of humic substances (HS'c) solution (0.3, 0.6, 0.9, 1.2 & 1.5%) for five different intervals (30, 90, 150, 210 & 270 min), on germination percentage (G%), germination velocity (GV) and vigor index (VI). Another In vitro experiment was conducted to assess the direct effect of HS'c on two nutritional media for Rhizoctonia solani and Fusarium solani mycelial growth, sclerotial productivity & viability, conidia viability. Greenhouse experiment was conducted to assess the effect of soaking cucumber seeds in HS'c and spraying with salicylic acid (SA) (100 and 200mg L-1) twice on growth parameters of cucumber seedlings, and controlling the root rot disease caused by R. solani and F. solani under saline conditions (2.36, 4, 5 & 6 dS m-1). The results indicate that T5 (0.3% for 210 min.) for 2015 and 2017 and T4 (0.3% for 150 min.) recorded the highest values for all studied parameters. No morphological changes were observed for the highest pathogenic two fungal isolate's mycelial growth on both fungal strains. R. solani was affected less than F. solani for the presence of different HS'c into nutrient media. 1.5% HS concentration had a reduction effect on the radical growth of fungal isolates, R. solani sclerotial production (30%) and viability (53%) and F. solani conidial viability (58%). Root rot disease was affected differently by seedling treatments of HS'c and/or SA under the four salinity conditions. The combined treatment; soaking seeds in 0.3% HS (for different period/year) and spraying seedlings with 200 SA had significantly reduced the disease incidence (DI) and disease index of both R. solani and F. solani specially in the lowest and highest salinity conditions.

Estimating the Toxicity and Biological Availability for Interaction Products of Metallic Iron and Humic Substances

This article considers the influence that suspensions of nanoparticles (sized from 10 to 60 nm) of iron oxo-compounds in different oxidation states have on biological objects. The suspension is formed by the interaction of metallic iron with aqueous solutions of humic substances. Based on the example of green microalgae Scenedesmus quadricauda (Turp.) Breb., it is shown that suspensions that contain iron oxo-compound nanoparticles stabilized with humic substances at an iron concentration from 0.14 to 2036 µM do not have a toxic effect on microalgae. The availability of iron contained in the suspensions was evaluated in the experiment on sprouts of wheat Triticum aestivum L., which had been grown under iron-deficient conditions. The root uptake of the ionic form of iron contained in the suspension was confirmed. It is shown that the studied suspensions of iron nanoparticles stabilized by humic substances accumulate on the surface of plant roots. These suspensions are supposed to be a source of iron with prolonged action for plants.

Analyzing the Dynamics of Interaction between Humic Coal Substances and Metallic Iron

The dynamics of interaction between metallic iron and aqueous solutions of three preparations of humic coal substances from different manufacturers is analyzed. Humic substances are characterized via elemental analysis, NMR spectroscopy, size-exclusion chromatography, electronic absorption spectroscopy, and chemical analysis. Distinctions are observed between the investigated humic substances in the content of aromatic moieties, the degree of their substitution, the content of carboxylic groups, and the degree of oxidation. It is shown that regardless of the background of humic substances, the interaction between their solutions and iron is based on the same set of consecutive reactions, which can be divided into three basic stages of interaction using data on the changes in easily controllable parameters (redox potential, pH, and solution absorbance). These stages of interaction are qualitatively described in Pourbaix diagram coordinates. Features of the structural and group composition of humic substances result in different times of the corresponding stages of interaction. Based on an analysis of the main components, a way of describing the complicated sequence of reactions between humic substances and iron in the coordinates of a two-factor plane is proposed to allow the clear attribution of experimentally measured parameters of the reaction medium to a certain stage of interaction between metallic iron and aqueous solutions of humic substances, regardless of the specific properties of the latter.

Nature-inspired synthesis of magnetic non-stoichiometric Fe3O4 nanoparticles by oxidative in situ method in a humic medium

Magnetic iron oxide nanoparticles in humic substances shell - Fe3-δO4@HS were synthesized by oxidative in situ method in aqueous solutions of humic substances from metallic iron precursor. Humic substances interacting with metallic iron under natural conditions act as a complex reagent that participates in acid-base, redox, complexation reactions and adsorption processes. The Fe3-δO4@HS particles is the final product of corrosion of metallic iron in the presence of HS. Products were characterized by dynamic light scattering, scanning and transmission electron microscopy, X-ray powder diffraction, Mössbauer spectroscopy, magnetometry, infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and evolved gas analysis. It was demonstrated that the samples contained particles with sizes of 40–50 nm comprised of ∼24 nm magnetite-like crystalline cores coated by humic substances. The synthetic approach used in this article can be used as a model of corrosion processes of ferrous metals in nature. In addition, magnetite-like nanoparticulates stabilized with humic substances can be promising as bioavailable iron additives for agricultural applications.

Soil washing with solutions of humic substances from manure compost removes heavy metal contaminants as a function of humic molecular composition

Humic Substances (HS) from Leonardite and two different composts were used as biosurfactants to wash heavy metals (Cu, Pb, Zn, Cd, Cr) from a soil added with two metals concentrations and aged for 4 and 12 months. Composts were obtained by mixing manure with either 40 (CM-I) and 20 (CM-II) % of straw as structuring material. For both aging periods and both metal concentrations, HS from CM-I removed more metals than from Leonardite, whereas the washing capacity of HS from CM-II was negligible. 13C-CPMAS-NMR spectra of HS indicated that while aromatic moieties for CM-I and Leonardite were more abundant than CM-II, HS from CM-I was largest in carboxyl and phenolic carbons. Hence, HS from CM-I had a greater complexing capacity than from both Leonardite and CM-II and effectively displaced heavy metals from soil during the washing treatment. Moreover, the amount of metals removed by solutions of ammonium acetate (AA) and diethylenetriaminepentaacetic acid (DTPA), was found invariably smaller than by HS from CM-I, thereby indicating that HS removed more than one metal specie. The combined washing with HS from CM-I before and after soil treatment by either AA and DTPA revealed significant larger metal removals than by single solutions alone. This shows that humic soil washing also renders residual metals potentially more available to subsequent soil remediation approaches, such as phytoextraction. These results suggest a novel, efficient, and molecularly-based technology to remediate soils from heavy metals can be based on a low-cost and sustainable humic matter produced from recycled biomasses.

Biodegradation of humic substances by microscopic filamentous fungi: chromatographic and spectroscopic proxies

The study of interactions between humic substances (HSs) and soil filamentous fungi is the key to understanding the sustainable soil functioning. The present work aims to examine the decomposition of HSs by filamentous dark-pigmented fungus Alternaria alternatа under the laboratory conditions and to determine the effect of easily assimilable organic carbon on this process. Analyzing such polydisperse substances like HSs by a complex integrated methodology makes it possible to explore the data on their decomposition by microorganisms. To achieve the aforementioned goals, we used chromatographic and spectroscopic approaches: low-pressure size-exclusion and hydrophobic interaction chromatography accompanied by absorption and fluorescence spectroscopy. To determine the effect cometabolism conditions produced on HS decomposition, two types of carbon substrates were added to the nutrient media: easily assimilable organic carbon (standard 0.3% or reduced 0.03% sucrose content) and hardly assimilable organic carbon (HSs), as well as their combinations. Five HS samples of different organic matter origin have been inspected: potassium humates (HPs) and humic acids (HAs) from coal, peat, and lignosulfonate. Correlation matrix and principal component analysis (PCA) were calculated for comprehensive data analysis. Transformations of the investigated HSs under fungal cultivation lead to the increase in the low molecular weight fraction, rise of hydrophilic fraction, enlargement of absorbance ratio A250/A365, shortening of the emission wavelength of the humic-type fluorescence, and growth in the fluorescence quantum yield measured with excitation at 355 nm. A positive correlation was observed between the accumulation of fungal biomass and the degree of HS decomposition. PCA analysis confirms that the difference in the results of HS decomposition largely depends on the sucrose content and the nature of HSs. We divided all the HS samples into four groups according to the degree of HS decomposition: original HS solutions, HPs altered using fungal cultivation at 0.03% sucrose, HAs after fungal cultivation at 0.03% sucrose, and finally, HSs (both HPs and HAs) after fungal cultivation at 0.3% sucrose. In the laboratory experiments, we showed that (1) the isolated HAs were more effectively degraded than the parent HPs, and this process was more pronounced at a reduced sucrose content, and (2) the decomposition of stable organic compounds (HSs) was activated by the easily assimilable carbon sources (especially 0.3% sucrose) being present. We assume that it is the easily assimilable organic carbon that most likely triggers the HS degradation working as the priming effect in natural environments.

Destruction of Surfactants and Humic Substances in Plazma-Chemical Reactor

Background. Wastewater treatment from surfactants and humic substances is an actual and not fully resolved environmental problem. Surfactants are one of the most dangerous pollutants of natural water bodies, which are sources of domestic and industrial water supply. The existing purification technologies have a number of limitations of both scientific and technical, and economic nature. Therefore, the innovative technology of plasma-chemical destruction in a liquid medium is proposed in the work.Objective. The aim of the paper is examination of plasma-chemical destruction of surfactants and humic substances.Methods. A plasma electrochemical unit with a modified plasmogenesis module was used to purify waste water contaminated with the dye. The concentration of surfactants and humic substances in the process of plasma-chemical treatment was determined by UV spectroscopy and spectroscopy in the visible region. Spectra of solutions of surfactants and humic substances were recorded on a spectrophotometer “Schimadzu UV2450”, the wavelength range λ = 200–700 nm.Results. It was established that plasma-chemical treatment of surfactants and humic substances causes rapid destruction of their molecules. Destruction is carried out by degradation of aromatic nuclei of molecules of surfactants and humic substances.Conclusions. It was determined that surfactants and humic substances can be successfully decomposed in the plasma chemical device. The degree of destruction was established to be more than 90 %. A large amount of fine-dispersed carbon particles was determined as result of plazma-chemical decomposition. In prospect, we plan to study the mechanism of destruction of surfactants and humic substances more detailed, as well as the properties of the obtained fine-dispersed carbon particles.