Concentrations Of Humic Substances Research Articles

Fulvic acid modulates mucosal immunity in fish skin: Sustainable aquaculture solution or environmental risk factor?

This is the first study determining the effects of bath exposure to fulvic acid, a humic substance, on the skin mucosal immunity of rainbow trout (Oncorhynchus mykiss). Humic substances have recently been gaining attention for their increasing concentrations in aquatic ecosystems and their use as supplements in sustainable aquaculture. This study demonstrated that water exposure to fulvic acid at concentrations of 5 mg C/L and 50 mg C/L increased lysozyme and alkaline phosphatase activities in the mucus by approximately 2-fold and 2.5 to 3.2-fold, respectively. Furthermore, exposure to 50 mg C/L resulted in a 77.0% increase in mucosal immunoglobulin concentrations compared to the other groups. Importantly, all mucus samples demonstrated significant antibacterial activity against Yersinia ruckeri, with control mucus reducing bacterial growth by 44.5% and exposure to fulvic acid increasing this effect to 26.3%. Although these modulations show promise for application in aquaculture, alterations of the beneficial microbiota from long-term exposure in natural waters can be expected. Monitoring the rising concentrations of humic substances in natural water bodies is therefore urgently needed. Overall, this study represents the first investigation revealing the ability of humic substances to modulate skin mucosal immunity and the capacity to combat microorganisms.

A new strategy of using periphyton to simultaneously promote remediation of PAHs-contaminated soil and production of safer crops

Contaminated farmland leads to serious problems for human health through biomagnification in the soil-crop-human chain. In this paper, we have established a new soil remediation strategy using periphyton for the production of safer rice. Four representative polycyclic aromatic hydrocarbons (PAHs), including phenanthrene (Phe), pyrene (Pyr), benzo[b]fluoranthene (BbF), and benzo[a]pyrene (BaP), were chosen to generate artificially contaminated soil. Pot experiments demonstrated that in comparison with rice cultivation in polluted soil with ΣPAHs (50 mg kg−1) but without periphyton, adding periphyton decreased ΣPAHs contents in both rice roots and shoots by 98.98% and 99.76%, respectively, and soil ΣPAHs removal reached 94.19%. Subsequently, risk assessment of ΣPAHs based on toxic equivalent concentration (TEQ), pollution load index (PLI), hazard index (HI), toxic unit for PAHs mixture (TUm), and incremental lifetime cancer risk (ILCR) indicated that periphyton lowered the ecological and carcinogenicity risks of PAHs. Besides, the role of periphyton in enhancing the rice productivity was revealed. The results indicated that periphyton alleviated the oxidative stress of PAHs on rice by reducing malondialdehyde (MDA) content and increasing total antioxidant capacity (T-AOC). Periphyton reduced the toxic stress of PAHs on the soil by promoting soil carbon cycling and metabolic activities as well. Periphyton also improved the soil's physicochemical properties, such as the percentage of soil aggregate, the contents of humic substances (HSs) and nutrients, which increased rice biomass. These findings confirmed that periphyton could improve rice productivity by enhancing soil quality and health. This study provides a new eco-friendly strategy for soil remediation and simultaneously enables the production of safe crops on contaminated land.

Metals and biogenic substances’ migration ability in the «bottom sediments – water» system under natural and experimental conditions


 
 
 The paper considers the results of long-term studies on some chemical elements’ migration (Al, Fe, Ti, Mn, Cu, Zn, Pb, N, P, Si) in the «bottom sediments – water» system of surface water bodies under the effect of different aquatic environment factors. The greatest effect is made by water bodies’ oxygen regime, pH, and presence of dissolved organic substances, in particular humic substances. The migration of manganese, iron, inorganic nitrogen and phosphorus from bottom sediments is controlled mostly by oxygen regime. Migration of these chemical elements significantly increases, when there is oxygen deficiency and anaerobic conditions are formed in the bottom water layer. It has been observed in both natural and experimental conditions. Man- ganese concentration increases in bottom water in 25–50 times, iron – in 1.3–13, inorganic nitrogen – in 5.3–19.3, and inorganic phosphorus – in 2.8–23 times. The dissolved oxygen concentration hardly has any effect on the migration of aluminium, titanium, copper, zinc, lead, and silicon from bottom sediments into the water. The chemical elements’ migration is significantly affected by a decrease in pH of water contacting with bottom sediments and the presence of humic substances in it. High humic substances concentrations promote a reduction in water pH and oxygen content, which is consumed for their oxidation. A case study of several water bodies illustrates the cumulative effect of water pH lowering, anaerobic conditions at the solid and liquid phases’ interface, as well as complexation with humic substances on chemical elements’ migration from bottom sediments. Experimental modeling has shown that the metal migration from bottom sediments occurs both due to their labile fractions and complex compounds with dissolved organic matter, especially with humic substances of low molecular weight (≤2.0 kDa). The share of the metal labile fraction gets higher, when water pH decreases. Under recent climate change, the probability of water’s secondary pollution with different chemicals increases significantly in summer. This is mainly caused by oxygen deficiency, water pH lowering, and reducing conditions at the «bottom sediments – water» interface with hydrogen sulphide being formed. This is especially true for highly eutrophic water bodies subject to human impact. The aquatic environment toxicity can get considerably higher due to the migration of chemicals with strong toxic properties from bottom sediments, as well as labile metal fractions, marked by higher bioavailability for hydrobionts.
 
 

Bottom sediments of the Shershnevskoye reservoir: Physicochemical characteristics and toxicity

The Shershnevskoye reservoir (ShR) is the main source of drinking water supply for the city of Chelyabinsk, which, since 2003, has been experiencing serious environmental problems caused by eutrophication processes. The purpose of this work was to study the bottom sediments (BS) of the ShR. BS were sampled in 4 locations of the ShR in the spring of 2024. We determined the 5 physicochemical parameters of the BS, the content of humic substances and gases (CO, CO2, CH4), 25 hydrochemical parameters and the toxicity of pore waters. It has been established that the bottom sediments of ShR are sandy silt, they have an average density of 1.008 g/cm3. In the longitudinal section of the reservoir, a trend towards an increase in the content of organic matter and methane in the BS from the upper reaches to the dam is observed. The pore waters belong mainly to the first (I) hydrochemical facies (Ca2+–Mg2+–Cl-–SO 2-) according to the Back (1961) classification. In the reservoir section, there is a clear trend of replacing bicarbonate ion with sulfate ion, and the concentration of chloride ion was minimal (from 0.1 to 1.1 mg/L). According to the results of biotesting using Scenedesmus quadricauda and Daphnia magna, all BS samples exhibit chronic toxicity, and two samples also exhibit acute toxicity, probably associated with the release of toxic products of organic matter mineralization.

STATE OF SOD-PODZOLIC SOIL FERTILITY LOAMY SOIL DURING LONG -TERM HAYMAKING WHEN USING IT

Morphological changes of sod-podzolic loamy soil during its haymaking use for 85 years are traced. The description of soilоfillets under different methods of using grass stands and their influence on plantcover, as well as morphological changes in the sod-humus horizon, is carried out. It was found that the presence of a sufficient amount of biomass or crop residues with the con-stant use of mineral fertilizers (N120P60K90) contributed to an increase in the sod-illuvial horizon and a decrease in the podzolic one, but the presence or lack of it did not significantly affect the acidic background of the soil of the experimental site. The content of humic substances in the soil, mobile forms of phosphorus and potassium in natural conditions (reserved) largely depended on the volume of biomass, but the highest value of these indicators in the experiment was obtained in the variant with the use of mineral fertilizers. Migration of nitrogen, calcium, and magnesium was observed. The maximum content of mobile forms of phosphorus and potassium was found in the humus horizon up to 30 cm. A common feature of mineral elements is the presence of two horizons with the maximum content: in the sodм and transitionalм to the soil-forming rock.

Effect and its mechanism of potassium persulfate on aerobic composting process of vegetable wastes.

Vegetable waste (VW) is a potential organic fertilizer resource. As an important way to utilize vegetable wastes, aerobic composting of VW generally has the problems of long fermentation cycle and incomplete decomposition of materials. In this study, 0.3-1.2% of potassium persulfate (KPS) was added to promote the maturity of compost. The results showed that the addition of KPS promoted the degradation of materials, accelerated the temperature rise of compost. KPS also promoted the formation of humic substances (HS). Compared with the control, HS contents of treatments with KPS addition increased by 7.81 ~ 17.52%. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) analysis reveal the mechanism of KPS affecting the composting process: KPS stimulated the degradation of various organic substances such as lignin at high temperature stage, and the degradation of lignin could accelerate the release and decomposition of other components; KPS made the structure of the material looser, with more voids and pores, and more specific surface area of the material, which was more suitable for microbial degradation activities. Therefore, the addition of KPS can promote the decomposition of organic matter in the early stage of composting, accelerate the process of thermophilic phase, and shorten the composting process and improve product maturity.

EFFECT OF HUMIC FEED ADDITIVE ON METABOLIC PROCESSES AND PRODUCTIVITY OF BEEF CATTLE

The use of made in Kazakhstan organic and mineral feed additives to in-crease the meat productivity of cattle is important for the agro-industrial complex of the Republic. During the study, qualitative and quantitative analysis of raw materials was made. Quality control of the finished feed additive was carried out following the requirements of the State Pharmacopoeia of the Republic of Kazakhstan. The studies were conducted in accordance with the requirements of the Technical Regulations approved by the Decree of the Government of the Republic of Kazakhstan dated April 23, 2008 No. 380, Regulation No. 7-1/625 dated 11/28/2014 and Regulation (EC) No. 1831/2003 of the European Parliament and of the Council of September 22, 2003, on additives for use in animal feeding. Kazakh potassium humate of the Maykubensky deposit is sterile, non-pyrogenic, non-toxic, and harmless, with an average pH of 11.0-1.0, and has a biological effect on laboratory animals (white mice). The effectiveness analysis in the production experiment allowed us to identify the positive effect of feed additives on metabolic processes and increasing meat productivity in bulls. Regardless of age, on the 7th day of taking the feed additive of potassium humate, the calves' coats acquired a noticeable shine and a bright color, and shedding was completed with-in a month. Clinical signs of metabolic disorders and vitamin deficiency, detected in the farm at the time of the experiment in some animals, pass through 20-30 days from the beginning of the application of the feed additive. The optimal scheme for the use of feed additives was tested on the Kazakh meat breed Akbas, and the concentration of humic substances was selected for the maximum mani-festation of the biologically active effect. Animals became mobile and active, their rumination became more active, they grew noticeably, and the average daily weight gain increased by 7.6-8.9%.

C4-HSL-mediated quorum sensing regulates nitrogen removal in activated sludge process at Low temperatures

The activated sludge process faces challenges in achieving adequate nitrification ability under low-temperature conditions. Therefore, we investigated the effects of different concentrations of exogenous N-butyryl-homoserine lactone (C4-HSL) on nitrogen removal in lab-scale sequencing batch reactors (SBRs) at 10 °C. The results revealed that both 10 and 100 μg/L of C4-HSL could improve NH4+-N removal efficiency by 26% and reduce the effluent TN concentration to below 15 mg/L. Analysis of extracellular polymeric substances (EPS) revealed that adding C4-HSL (especially 100 μg/L) reduced the protein-like substance content while increasing the humic and fulvic acid-like substance content in EPS. Protein-like substances could serve as carbon sources for denitrifiers, thus promoting denitrification. Moreover, exogenous C4-HSL increased the abundance of bacteria and genes associated with nitrification and denitrification. Further analysis of quorum sensing (QS) of microorganisms indicated that exogenous C4-HSL (especially 100 μg/L) promoted regulation, transportation, and decomposition functions in the QS process. Furthermore, CS, sdh, fum, and mdh gene expressions involved in the tricarboxylic acid (TCA) cycle were enhanced by 100 μg/L C4-HSL. Exogenous C4-HSL promoted microbial communication, microbial energy metabolism, and nitrogen metabolism, thereby improving the nitrogen removal efficiency of activated sludge systems at low temperatures. This study provides a feasible strategy for enhancing denitrogenation performance at low temperatures through exogenous C4-HSL.

The addition of humic substances extracted from vermicompost enhances the growth performance and the antioxidant status of weaning pigs

The aim of the study was to assess the effect of humic substances (HS) extracted from vermicompost on the growth performance, fecal score, bone ash content and antioxidant status in muscles and blood serum of weaned pigs from 1-42 days postweaning. Two-hundred 22-day weaned pigs were assigned to four treatments: 1= Positive control diet with colistin (PC), 2= Negative control diet without antibiotic or HS (NC), 3 and 4= Diets with 2 500 and 5 000 ppm of HS, respectively. Growth performance, fecal consistency, dry matter and ashes of metatarsus and the 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, iron reducing ability and thiobarbituric acid reactive substances in muscles and blood were registered. Results were subjected to ANOVA and regression analysis. Linear increasing responses (P < 0.05) were found in the body weight at 42 days postweaning, the ADG from 1-7, 8-21, 22-42 and 1-42 and the gain:feed ratio from 1-7, 22-42 and 1-42 days postweaning, whilst the fecal score decreased linearly (P < 0.01) from 1-7, 8-21 and 1-42 days postweaning due to the increasing dietary HS concentration. The antioxidant potential of 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (P < 0.05) in loin muscle and blood serum at three and seven days, and in fillet muscle at seven days postweaning increased linearly due to the increasing dietary HS concentration. It is concluded that the addition of HS improved the growth performance from 1-42 days postweaning and the antioxidant status in muscles and blood serum of weaned pigs at three and seven days postweaning.

Ligand exchange provides new insight into the role of humic substances in the marine iron cycle

Organic complexation of iron plays a crucial role in preventing its precipitation, facilitating its transport, and modulating its reactivity and bioavailability in natural waters. Although humic substances (HS) complexes serve as the primary source of terrestrial iron reaching ocean waters, the transition from Fe-HS species to other forms of organic complexation with ocean autochthonous ligands has not yet been properly described. Taking advantage of the electrolability of Fe-HS complexes, we monitored the ligand exchange of iron-saturated Suwannee River fulvic and humic acids (SRFA and SRHA) after the addition of desferrioxamine B (DFOB) and other ligands for comparison. We observed that Fe-HS concentrations gradually decreased until reaching an apparent steady state, typical of a reversible reaction within 1 to 15 h. The dissociation kinetics and species partitioning of Fe-SRHS complexes at the equilibrium showed some features contrary to the current paradigm of HS iron complexation. The affinity of SRFA to bind iron is close to that of DFOB and for SRHA is even higher. The heterogeneity of the HS iron binding groups was confirmed, although experiments in NaCl solutions revealed that in seawater it is substantially caused by the interaction of major divalent ions. The different dissociation kinetics of Fe-SRHS complexes obtained with different competing ligands and the absence of Fe-DFOB dissociation in the presence of iron-free SRFA indicate an intimate associative mechanism of ligand exchange, with the presence of a ternary complex (SRHS-Fe-DFOB) that does not form if the departing complex is Fe-DFOB. We hypothesize that at the concentrations of HS and siderophores found in the open ocean, iron ligand exchange is limited and organic iron speciation will be close to being regulated on a “first come, first served” basis. Experiments conducted under saturation of all iron complexes support the formation of a permanent concentration of a ternary complex. Our findings show the real complexity of cation-ligand interactions in seawater, with implications for the interpretation of recent chromatographic and electrochemical measurements and for the understanding of iron partitioning in the presence of ubiquitous HS.

A comparison of characterisation and modelling approaches to predict dissolved metal concentrations in soils

Environmental context It is useful to know the concentration of ‘labile’, or chemically active, metal in soils because it can be used to predict metal solubility and environmental impact. Several methods for extracting the labile metal from soils have been proposed, and here we have tested two of these to see how well the resulting data can be used to model metal solubility. Such mixed approaches can be applied to different soil types with the potential to model metal solubility over large areas. Rationale Predicting terrestrial metal dynamics requires modelling of metal solubility in soils. Here, we test the ability of two geochemical speciation models that differ in complexity and data requirements (WHAM/Model VII and POSSMs), to predict metal solubility across a broad range of soil properties, using differing estimates of the labile soil metal concentration. Methodology Using a dataset of UK soils, we characterised basic properties including pH and the concentrations of humic substances, mineral oxides and metals. We estimated labile metal by extraction with 0.05 mol L−1 Na2H2EDTA and by multi-element isotopic dilution (E-value). Dissolved concentrations of Ni, Cu, Zn, Cd and Pb were estimated in 0.01 mol L−1 Ca(NO3)2 soil suspensions using the total metal ({M}total), the EDTA-extracted pool ({M}EDTA) and the E-value ({M}E) as alternative estimates of the chemically reactive metal concentration. Results Concentrations of {M}EDTA were highly correlated with values of {M}E, although some systematic overestimation was seen. Both WHAM/Model VII and POSSMs provided reasonable predictions when {M}EDTA or {M}E were used as input. WHAM/Model VII predictions were improved by fixing soil humic acid to a constant proportion of the soil organic matter, instead of the measured humic and fulvic acid concentrations. Discussion This work provides further evidence for the usefulness of speciation modelling for predicting soil metal solubility, and for the usefulness of EDTA-extracted metal as a surrogate for the labile metal pool. Predictions may be improved by more robust characterisation of the soil and porewater humic substance content and quality.

STUDY OF BIOLOGICALLY ACTIVE POLYMER HYDROGELS FOR REGULATION OF WATER-LIPID BALANCE

The article shows studies on the study of biologically active polymeric hydrogel materials for the regulation of water-lipid balance. It is shown that the current trend in the development of biologically active polymers and materials based on them is the technology of creating effective systems for the transdermal delivery of drugs and active substances to the human body. As part of the literature review, it has been proven that transdermal delivery systems based on biologically active polymeric materials are of increased interest in the administration of drugs through the skin, for local therapeutic effects on the affected skin during systemic local drug delivery, and they are also widely used in the direction biologically active materials in the form of various types of polymeric hydrogels. In the article, a study was conducted to determine the features of obtaining biologically active polymeric hydrogel materials for regulating the water-lipid balance. Food gelatin TM "Mriya" (Ukraine), glycerin, sodium alginate, humic acids and distilled water were used in the work. The development and research of biologically active polymeric hydrogel materials for the regulation of water-lipid balance has been carried out. It has been established that humic acids in polymer hydrogels based on gelatin and sodium alginate have a high antibacterial activity and completely stop the processes of mold formation in them. It has been proven that compositions based on gelatin and sodium alginate with a content of humic acids of 15 % are the most effective in terms of obtaining hydrogels with an antibacterial effect. Effective biologically active polymeric hydrogel materials based on gelatin and sodium alginate, modified with different content of humic acids, have been obtained and studied. Modification of biopolymer hydrogels based on gelatin and sodium alginate with humic acids makes it possible to obtain biologically active polymeric hydrogel materials with an increased degree of swelling and the ability to significantly improve the moisture-lipid balance of the skin: according to the initial indicators of moisture 34–36 % and fat content 8–10 % of the skin, it increases them up to 58–66 % and 52–60 % respectively. In fact, thanks to the use of biologically active polymeric hydrogel materials based on gelatin and sodium alginate modified with humic acids, it becomes possible to transform the state from weakly oily tough to highly moist oily elastic skin. The effect of improving the moisture-lipid balance of the skin is enhanced along with the content of humic substances.

LIGNITE AS A RAW MATERIAL FOR THE PRODUCTION OF WATER-SOLUBLE SORBENTS

Large lignite reserves are concentrated in the Dnipro lignite basin of Ukraine. It is profitable to extract it by open-pit mining, as the seams are shallow. Ukrainian lignite is predominantly earthy, subbituminous, which in turn is characterized by a high content of free humic acids. Despite the significant lignite reserves in Ukraine and favourable conditions, its production is insignificant. Most of the lignite is used as fuel, and a small part of it is used as raw material. We have studied the lignite of the Oleksandriya deposit of Ukraine, which contains a large amount (about 80 %) of humic acid, which is the basis to produce effective water-soluble sorbents. The article investigates and determines the efficiency of using lignite from the Oleksandriya deposit to produce humic substances, their elemental composition, and the yield of humic acids from them. The efficiency of the use of humic substances obtained from lignite of the Alexandria deposit in the binding of heavy metal ions (Pb2+, Cd2+) using the method of complexation - ultrafiltration - was determined. The performance of ultrafiltration membranes with a humate solution was determined. The retention coefficient of metal ions, which depends on the concentration of humic substances, was calculated. The conducted studies allow us to assert that the application of the ultrafiltration-complexation method using complexing agents based on humic substances of lignite from the Alexandria deposit can significantly increase the degree of purification of aqueous solutions from heavy metal ions. These studies are relevant and expand the possibilities of using lignite. It has been shown that Ukrainian lignite can be used to produce an environmentally friendly and cheap complexing agent. An important priority for the use of water-soluble humic substances is the large lignite reserves in Ukraine, which can also contribute to improving economic performance. Also, the studies conducted suggest that the application of a combined method that combines ultrafiltration with complexation when using complexing agents based on lignite humic substances can significantly increase the degree of purification from heavy metal ions.

The role of various fractions of humic substances from surface water in binding Al(III), Fe(III), AND Cu(II) into complexes

The aim of this research work was to evaluate the role of various fractions of humic substances (HS) in binding Al(III), Fe(III) and Cu(II) ions into complexes using gel chromatography. With an increase in HS concentration in Ukraine’s surface water bodies, the share of HS’ fraction with a molecular weight of 20–5 kDa increases from 37% to 59%. In the water bodies under study the HS’ fractions with molecular weight 20–5 kDa and < 1 kDa play a principal role in the studied metals’ migration. HS with molecular weight 20–5 kDa have been found to bind the smallest amount of Al(III), Fe(III) and Cu(II) in complexes, if the metals concentration bound by 1 mg fraction of HS with a certain molecular weight is calculated. Experimental results showed that, the investigated metal ions have the ability to bind into complexes mainly by HS with a molecular weight of >20 and <1 kDa. In the water bodies under study 1 mg of humic acids has a greater binding ability in relation to Al(III), Fe(III) and Cu(II) ions than 1 mg of fulvic acids. Fulvic acids and humic acids with a molecular weight of 20–5 kDa also have the lowest binding ability.

Elaborating the microbial mechanism of humic substance formation during lignocellulosic biomass composting by inoculation with different functional microbes

This study explored the microbial mechanism of humic substance (HS) formation in the lignocellulosic biomass composting by inoculation with different functional microbes. Typical types of functional bacterial and fungal strains with higher lignocellulose degradation characteristics were inoculated into compost. Three treatment groups were set up: uninoculated microbes (CK treatment), inoculation of Bacillus subtilis (B4 treatment) and Aspergillus fumigatus (Z1 treatment). Results showed that the HS concentration for inoculation B. subtilis and A. fumigatus increased by 15.42% and 56.31%, respectively. B. subtilis could produce phenolic metabolites, cellobiose and maltose, and then enter the tricarboxylic acid cycle, thereby releasing CO2, while A. fumigatus could promote HS formation by producing phenolic metabolites, 2,4-Di-tert-butylphenol, cellobiose, maltose, glucose, galactose, xylose, arabinose, mannose, ribose and deoxyribose. In addition, inoculating A. fumigatus enhanced the correlation among lignocellulose-degrading metabolites and HS, and increased the relative abundance and numbers of microbial hosts of lignocellulose-degrading genes, promoting the HS formation. In addition, cellulose-degrading genes and lignin-degrading genes differences were the main drivers of HS formation in the inoculated treatment groups. Soluble sugar, organic matter, lignin and pH were key drivers in influencing the lignocellulose-degrading genes. This study was important for analyzing microbial biological mechanisms of HS formation during composting.

Applying sludge hydrolysate as a carbon source for biological denitrification after composition optimization via red soil filtration

Sludge hydrolysate, the byproduct generated during sludge hydrothermal treatment (HT), is a potential carbon source for biological denitrification. However, the refractory organic matters and the nutrient substances are unfavorable to the nitrogen removal. In this study, effects of HT conditions on the hydrolysate properties, and the hydrolysate compositions optimization via red soil (RS) filtration were investigated. At HT temperature of 160–220 °C and reaction time of 1–4 h, the highest dissolution rate of organics from sludge to hydrolysate achieved 70.1 %, while the acetic acid dominated volatile fatty acids (VFAs) was no more than 5.0 % of the total organic matter content. The NH4+-N and dissolved organic nitrogen (DON) were the main nitrogen species in hydrolysate. When the hydrolysate was filtered by RS, the high molecular weight organic matters, DON, NH4+ and PO43− were effectively retained by RS, while VFAs and polysaccharide favorable for denitrification were kept in the filtrate. When providing same COD as the carbon source, the filtrate group (Fi-Group) introduced lower concentrations of TN and humic substances but higher content of VFAs. This resulted in TN removal rate (57.0 %) and denitrification efficiency (93.6 %) in Fi-Group higher than those in hydrolysate group (Hy-Group), 39.4 % and 83.7 %, respectively. It is noticeable that both Hy- and Fi- Groups up-regulated most of denitrification functional genes, and increased the richness and diversity of denitrifying bacteria. Also, more denitrifying bacteria genera appeared, and their relative abundance increased significantly from 3.31 % in Control to 21.15 % in Hy- Group and 31.31 % in Fi-Group. This indicates that the filtrate is a more suitable carbon source for denitrification than hydrolysate. Moreover, the pH rose from 4.6 ± 0.14 to 6.5 ± 0.05, and the organic carbon, TN, TP and cation exchange capacity (CEC) of RS increased as well after being filtered, implying that the trapped compounds may have the potential to improve soil quality. This study provides a new insight for hydrolysate application according to its composition characteristics, and helps make the most use of wasted sludge.

Humification and fungal community succession during pig manure composting: Membrane covering and mature compost addition

The objective of this study was to elucidate the combined effect of a semi-permeable membrane (M) and mature compost (MC) on humification and fungal community succession in pig manure composting. Compared with the control, the concentrations of humic substances (HSs) increased by 44.54 % (M + 15 % MC) and 43.90 % (M). During the thermophilic phase, Aspergillus (67.26 %) was the dominant genus in the M + 15 % MC treatment. Membrane covering increased the relative abundance (RA) of other phyla (except for Ascomycetes and Basidiomycetes) on the 14th day and Basidiomycetes on the 80th day in M treatment. Humic acid, HSs were positively correlated with the RA of genera Myceliophthora, Kernia, and Mycothermus. Myceliophthora was the key genus in the M + 15 % MC treatment on the 80th day. The results showed that 15 % MC addition under membrane covering optimizes the quality of composting products.

Performance, immune response, disease resistance, and gut microbiota of rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) juveniles fed ground leonardite with a high humic substance content

In the present study, the effects of feeding ground leonardite (LE), which contained 68% of humic substances, to juvenile Oncorhynchus mykiss were examined on overall growth and production performance, feed nutrient digestibility, gut microbiota, health condition, antioxidant status, immune response, and disease resistance. During two consecutive experiments, fish were fed four experimental diets with different LE supplementary levels: 0, 0.5, 1, and 3% of feed mass (LE0, LE0.5, LE1, and LE3, respectively). Firstly, the fish were tested in a growing experiment (GE, n = 300 fish/group, body weight 15.4 ± 2.5 g) for 56 days. Thereafter, these fish (n = 75 fish/group, body weight 51.9 ± 8.7 g) were exposed to an intraperitoneal infection challenge experiment (IC) with Aeromonas salmonicida subsp. salmonicida for 28 days.In the GE, dietary LE did not affect the growth, production, or health performance of O. mykiss juveniles, although the fish more than tripled their initial body weight. The LE dose had an impact on the digestibility of feed nutrients (dry matter, gross energy, and ash), but not on the protein and lipid digestibility or solid waste outputs. The gut microbial communities were highly diverse across the experimental groups and remained distinct between the control and LE groups. The LE had a dose-dependent effect on the cell composition of the head kidney and peripheral blood leukocytes. The highest LE addition exerted the immune suppressive effect, and a decreased count of immune cells was observed in the LE3.The peritoneal cavity infection in the IC trial induced the rapid recruitment of myeloid cells in all groups shortly after the infection, except for the LE3, which had an apparent delayed response. The cumulative mortality and specific trout antibody levels against A. salmonicida did not significantly vary among tested groups, although their average initial level dropped by half at 3 days post-infection (dpi), and subsequently doubled at 28 dpi. The plasma biochemical parameters (TP, TAG, and CHOL) showed an overall decrease at 0–3 dpi, while increasing back to the initial levels at 3–6 dpi. Only LDH negatively correlated with LE inclusion, this can reflect the oxidative stress in the highest LE inclusion.Overall, our results support that there is a dose-dependent effect that should be optimised for ground LE dietary use in aquaculture.

The Current Trophic State and Water Quality of Lake Onego

The trophic state and water quality of Lake Onegо were assessed under climate warming and changes in anthropogenic load over the past 30 years. The water body retains its natural oligotrophic state during the summer stratification according to the concentration of chlorophyll a. A small amount of readily mineralizable organic matter in water determines the low level of development of saprophytic bacteria, corresponding to xenosaprobic and β-oligosaprobic waters. Only the Kondopogskaya Bay of Lake Onego is characterized by a higher level of trophy (mesotrophic) and water saprobity (β-mesosaprobic) due to pollution by wastewater from the pulp and paper mill and waste from trout farms. Local “bloom” of cyanobacteria of in the open area of the lake was observed during the anomalous heating of the epilimnion in the summer of 2022 for the first time in the 50-year history of research. The increase in the concentration of humic substances in the water of the bays as a result of climate warming at this stage did not lead to a change in the level of saprophytic bacteria.

Interaction of Ca2+ and Fe3+ in co-precipitation process induced by Virgibacillus dokdonensis and its application

Biomineralization has garnered significant attention in the field of wastewater treatment due to its notable cost reduction compared to conventional methods. The reinjection water from oilfields containing an exceedingly high concentration of calcium and ferric ions will pose a major hazard in production. However, the utilization of biomineralization for precipitating these ions has been scarcely investigated due to limited tolerance among halophiles towards such extreme conditions. In this study, free and immobilized halophiles Virgibacillus dokdonensis were used to precipitate these ions and the effects were compared, at the same time, biomineralization mechanisms and mineral characteristics were further explored. The results show that bacterial concentration and carbonic anhydrase activity were higher when additionally adding ferric ion based on calcium ion; the content of protein, polysaccharides, deoxyribonucleic acid and humic substances in the extracellular polymers also increased compared to control. Calcium ions were biomineralized into calcite and vaterite with multiple morphology. Due to iron doping, the crystallinity and thermal stability of calcium carbonate decreased, the content of OC = O, NC = O and CO-PO3 increased, the stable carbon isotope values became much more negative, and β-sheet in minerals disappeared. Higher calcium concentrations facilitated ferric ion precipitation, while ferric ions hindered calcium precipitation. The immobilized bacteria performed better in ferric ion removal, with a precipitation ratio exceeding 90%. Free bacteria performed better in calcium removal, and the precipitation ratio reached a maximum of 56%. This research maybe provides some reference for the co-removal of calcium and ferric ions from the oilfield wastewater.