Search Results (150)

Different types of organic materials demonstrate varying efficacy in ameliorating saline–alkali soils, while the combined application of organic materials can potentially enhance the remediation effects on saline–alkali land. To verify this assumption, our study conducted a pot experiment with spinach in saline–alkali soil, observing the improvement effect of saline–alkali soil and the growth of crops when acid fermentation products of vegetables, humic acid-like substances, and corn straw were applied either individually or in combination. The results revealed that both the sole and combined application of organic materials could enhance the yield of spinach. Particularly, humic acid-like substances increased spinach yield to six times that of the chemical fertilizer treatment. Although the application of organic materials led to a decline in the diversity and richness indices of the microbial community in saline–alkali soil (except fungal richness), the combined use of organic materials contributed to a healthier trend in the soil microbial community structure. Beyond its effects on soil nutrients such as total carbon and total nitrogen, the improvement in soil organic matter activity caused by the joint application of organic materials was identified as the primary factor responsible for enhancing the health of the soil microbial community and the remediation effects on saline–alkali soil. Full article

Biologically treated swine farm wastewater still contains high levels of refractory organics, humic substances and antibiotic residues, posing environmental risks and limiting opportunities for water reuse. Wastewater treatment by ozonation alone suffers from low mass transfer efficiency and selective oxidation. To overcome these limitations, a catalytic ozonation process (O₃/Fe²⁺/H₂O₂) was applied and optimized using Response Surface Methodology (RSM) based on single-factor experiments and Central Composite Design (CCD) for advanced swine farm wastewater treatment. The optimal conditions ([O₃] = 25.0 mg/L, [Fe²⁺] = 25.9 mg/L, [H₂O₂] = 41.1 mg/L) achieved a COD removal of 44.3%, which was 86.8% higher than that of ozonation alone, and increased TOC removal to 29.5%, indicating effective mineralization. Biodegradability (BOD₅/COD) of swine farm wastewater effluent increased from 0.01 to 0.34 after the catalytic ozonation treatment. Humic-like and fulvic-like substances were removed by 93.7% and 95.4%, respectively, and antibiotic degradation was significantly accelerated and enhanced. The synergistic process improved ozone utilization efficiency by 33.1% and removed 53.95% of total phosphorus through Fe³⁺-mediated coprecipitation. These findings demonstrate that with catalytic ozone decomposition and production of hydroxyl radicals, the O₃/Fe²⁺/H₂O₂ system effectively integrates enhanced ozone utilization efficiency, radical synergy, and simultaneous pollutant removal, providing a cost-effective and technically feasible strategy for advanced swine farm wastewater treatment and safe reuse. Full article

Due to its complex composition and toxicity, the waste liquid from hydrothermal carbonization (HTC) poses a serious environmental challenge that must be addressed before disposal. In this study, the photochemical treatment of HTC liquid in a microreactor flow system was investigated. The effects of wavelength, the presence of atmospheric oxygen, oxidizing agent (H₂O₂) and catalyst (FeSO₄), residence time and pH on the efficiency of the photo-treatment were investigated. In addition, the influence of the addition of deep eutectic solvent (DES) on photo-treatment was studied. The results showed that the photochemical treatment was more efficient at 365 nm than at 420 nm, and that the acidic conditions gave better results than the basic ones. UV₃₆₅ treatment in the presence of H₂O₂ (at a dosage of 1 vol%) resulted in removal efficiencies of 31.6% for COD, 17.6% for TOC, 16.9% for NH₄-N and 17.2% for PO₄-P. The addition of FeSO₄ caused coagulation/flocculation effects, but improved phosphorus removal. The addition of DES resulted in slight discolouration of the liquid and proved unsuccessful in COD removal. The GC-MS analysis and 3D-EEM spectra showed significant changes in the fate of organics and in the fluorescence intensity of aromatic proteins and humic acid-like substances. Photochemical treatment in a microreactor flow system in the presence of H₂O₂ under the selected operating conditions reduced the content of organics and nutrients in the HTC liquid, but the process liquids still showed toxic effects on the organisms V. fischeri and Daphnia magna. Full article

This study aimed to develop an effective method to overcome the challenge of straw return in cold-region soil. We systematically investigated the synergistic mechanism of montmorillonite (MMT) and composite amino acid (CAA) on straw humification and carbon sequestration through a low-temperature litterbag field experiment. The results indicate that the combined treatment (MMT-CAA) significantly increased the decomposition rate of straw by 42.1% compared to the control (CK), with MMT showing particular efficacy in lignin degradation (28.3% reduction), while the CAA preferentially decomposed cellulose (19.7% reduction). An FTIR analysis of the decomposition products confirmed these findings. Water-soluble organic carbon (WEOC) and its three-dimensional fluorescence spectra exhibited a 25.0% increase in MMT-CAA and enhanced aromaticity of humic acid-like substances. Humic substances and their ¹³C-NMR revealed that MMT-CAA enhanced humic acid formation and molecular stability by 31.4% (with a 47.8% increase in aromaticity). A further redundancy analysis and symbiotic network of microorganisms demonstrated that MMT-CAA increased the abundance of lignocellulose-degrading phyla (Actinomycetes and Stramenomycetes) and the formation of a complex co-degradation network. Field corn planting trials indicated that MMT-CAA increased plant height by 55.1%, stem thickness by 58.7%, leaf area by 70.2%, and the SPAD value by 41.1%. Additionally, MMT significantly reduced CO₂ and N₂O emission fluxes by 35.6% and 15.8%, respectively, while MMT-CAA increased CH₄ uptake fluxes by 13.4%. This study presents an innovative strategy, providing mechanistic insights and practical solutions to synergistically address the challenges of slow straw decomposition and carbon loss in cold regions. Full article

The EU’s Circular Economy Action Plan promotes the use of organic waste as fertilizer, thus allowing the recycling of nutrients in the agricultural system. Research on the agronomic reuse of composted substrates previously employed for mushroom cultivation remains limited, despite their rich content of plant residues and fungal biomass, which could be repurposed as soil amendments under suitable conditions. This study evaluated the agronomic potential of spent mushroom substrates from Agaricus bisporus and Pleurotus ostreatus, including recomposted A. bisporus residues. A range of analytical procedures was employed to assess their suitability for soil improvement and the formation of humic-like substances, including physical, chemical, microbiological, phytotoxicity, and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analyses. The spent Pleurotus substrate exhibited low nutrient content (1.1% N, negligible P, 0.9% K), but high water retention (820 kg water Mg⁻¹) and 48% organic carbon (OC), indicating its potential as a soil amendment or seedling substrate. In contrast, spent and composted Agaricus substrates showed moderate nutrient content (1.8–2.7% N; 0.8–0.7% P and 1.3–1.8% K), appropriate C/N ratios (10–15), and sufficient OC levels (24–30%), supporting their use as fertilizers. However, elevated salinity levels (18–23 dS m⁻¹) may restrict their application for salt-sensitive crops. No significant phytotoxic effects on seed germination were observed, and microbiological analyses confirmed the absence of Salmonella spp. in the three substrates. Py-GC/MS revealed a humic acid-like fraction comprising altered lignin structures enriched with lipid and nitrogen compounds. Overall, the studied materials demonstrate promising agronomic value and the capacity to contribute to long-term soil carbon storage. Full article

The extensive use of pesticides has significant implications for public health and the environment. Breeding crop plants is the most effective and environmentally friendly approach to improve the plants’ resistance. However, it is time-consuming and costly, and it is sometimes difficult to achieve satisfactory results. Plants induce defense responses to natural elicitors by interpreting multiple genes that encode proteins, including enzymes, secondary metabolites, and pathogenesis-related (PR) proteins. These responses characterize systemic acquired resistance. Humic substances trigger positive local and systemic physiological responses through a complex network of hormone-like signaling pathways and can be used to induce biotic and abiotic stress resistance. This study aimed to assess the effect of humic substances on the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POX), and β-1,3-glucanase (GLU) used as a resistance marker in various plant species, including orange, coffee, sugarcane, soybeans, maize, and tomato. Seedlings were treated with a dilute aqueous suspension of humic substances (4 mM C L⁻¹) as a foliar spray or left untreated (control). Leaf tissues were collected for enzyme assessment two days later. Humic substances significantly promoted the systemic acquired resistance marker activities compared to the control in all independent assays. Overall, all enzymes studied in this work, PAL, GLUC, and POX, showed an increase in activity by 133%, 181%, and 149%, respectively. Among the crops studied, citrus and coffee achieved the highest activity increase in all enzymes, except for POX in coffee, which showed a decrease of 29% compared to the control. GLUC exhibited the highest response to HS treatment, the enzyme most prominently involved in increasing enzymatic activity in all crops. Plants can improve their resistance to pathogens through the exogenous application of HSs as this promotes the activity of enzymes related to plant resistance. Finally, we consider the potential use of humic substances as a natural chemical priming agent to boost plant resistance in agriculture Full article

This study aims to evaluate eco-innovative solutions in the fertilizer industry that allow for waste valorization in the context of a resource-efficient circular economy. A comprehensive reuse strategy was developed for low-rank peat and post-cultivation horticultural mineral wool, involving the extraction of valuable humic substances from peat and residual nutrients from used mineral wool, followed by the use of both post-extraction residues to produce organic–mineral substrates. The resulting products/semifinished products were characterized in terms of their composition and properties, which met the requirements necessary to obtain the admission of this type of product to the market in accordance with the Regulation of the Minister for Agriculture and Rural Development of 18 June 2008 on the implementation of certain provisions of the Act on fertilizers and fertilization (Journal of Laws No 119, item 765). Elemental analysis, FTIR spectroscopy, and solid-state CP-MAS ¹³C NMR spectroscopy suggest that post-extraction peat has a relatively condensed structure with a high C content (47.4%) and a reduced O/C atomic ratio and is rich in alkyl-like matter (63.2%) but devoid of some functional groups in favor of extracted fulvic acids. Therefore, it remains a valuable organic biowaste, which, in combination with post-extraction waste mineral wool in a ratio of 60:40 and possibly the addition of mineral nutrients, allows us to obtain a completely new substrate with a bulk density of 264 g/m³, a salinity of 7.8 g/dm³ and a pH of 5.3, with an appropriate content of heavy metals and with no impurities, meeting the requirements of this type of product. A liquid fertilizer based on an extract containing previously recovered nutrients also meets the criteria in terms of quality and content of impurities and can potentially be used as a fertilizing product suitable for agricultural crops. This study demonstrates a feasible pathway for transforming specific waste streams into valuable agricultural inputs, contributing to environmental protection and sustainable production. The production of a new liquid fertilizer using nutrients recovered from post-cultivation mineral wool and the preparation of an organic–mineral substrate using post-extraction solid residue is a rational strategy for recycling hard-to-biodegrade end-of-life products. Full article

Vineyard soils are frequently contaminated with copper due to the use of Cu fungicides to prevent downy mildew. This study investigated the effects of an aerated compost tea (ACT) made from grape pomace and animal manure on the downward transfer of Cu and on the accumulation of Cu in plants in a sandy loam vineyard soil. Crimson clover and pot marigold were grown in a 40 cm soil column with Cu supplied to the surface at loadings representative of those applied in European vineyards, plus additions of ACT. A source of Cu enriched in the stable isotope ⁶⁵Cu was used to distinguish freshly added Cu (fresh Cu) from Cu already present in the soil (aged Cu). ACT increased the concentration of soluble humic substances (SHS) in pore water in the top 7.5 cm of the column, and increased the concentration of Cu, Al, and Fe in pore water in proportion to the concentration of SHS. The transfer of fresh Cu to deeper soil was limited to the top 5 cm, even after the addition of ACT, although fresh Cu reacted slightly more to ACT than aged Cu. ACT had no effect on Cu phytoextraction but increased the concentration of Cu in roots by almost twofold. Relatively more fresh Cu was transferred to plants than aged Cu, primarily due to its preferential accumulation on the surface. The risk associated with the use of ACT on vineyard soils is not that of promoting the downward transfer of Cu, but rather of increasing Cu availability to plants and likely to other living organisms in the topsoil. Full article

The interactions between dissolved organic matter (DOM) and agrochemicals (e.g., neonicotinoid insecticides, NIs) govern the distribution, migration, and potential environmental risks of agrochemicals. However, the long-term effects of agricultural management on the DOM components and structure, as well as their further influences on the interactions between DOM and agrochemicals, remain unclear. Here, spectroscopic techniques, including Fourier transform infrared spectroscopy, two-dimensional correlation spectroscopy, and three-dimensional excitation–emission matrix fluorescence spectroscopy were employed to delve into the interaction mechanism between the DOM from citrus orchards with distinct cultivation ages (10, 30, and 50 years) and imidacloprid, which is a type of pesticide widely used in agricultural production. The findings revealed that the composition and structure of soil DOM significantly change with increasing cultivation age, characterized by an increase in humic substances and the emergence of new organic components, indicating complex biodegradation and chemical transformation processes of soil organic matter. Imidacloprid primarily interacts with fulvic acid-like fractions of DOM, and its binding affinity decreases with increasing cultivation age. Additionally, the interactions of protein-like fractions with imidacloprid occur after humic-like fractions, suggesting differential binding behaviors among DOM fractions. These results demonstrate that cultivation age significantly influences the composition and structural characteristics of soil DOM in citrus orchards, subsequently affecting its sorption capacity to imidacloprid. This study enhances the understanding of imidacloprid’s environmental behavior and provides theoretical support for the environmental risk management of neonicotinoid pesticides. Full article

Dissolved organic matter (DOM) exerts a significant influence on the environmental behavior of heavy metals in water. This study investigated the spatial distribution characteristics of DOM in the upper reaches of the Yangtze River and its vertical (0–10 m) binding behavior with heavy metals. The results indicated that humic acid-like substances dominated the DOM composition in the river water, exhibiting spatial variability horizontally, with a higher proportion of protein-like components observed at the depth of 8 m. The DOM showed complexation affinity (LogK) values were 4.71–6.38 for Cu²⁺ and 4.27–6.26 for Hg²⁺, with the protein-like component C3 exhibiting higher LogK values when binding with Cu²⁺ or Hg²⁺ compared to humic-like components. The LogK_Cu and LogK_Hg varied distinctly with water depth, and at 8 m depth, humus-like component C1 exhibited stronger binding affinity for Hg²⁺, whereas protein-like component C3 showed greater affinity for Cu²⁺. The 2D-FTIR-COS analysis revealed that, in the DOM-Cu complexes, DOM from surface water preferentially bound to O-H groups of carbohydrates, phenols, and carboxylic acids, while deep water DOM favored C=O groups in amides; for DOM–Hg complexes, the active binding sites varied distinctly with depth. This study provides novel insights into the migration and transformation mechanisms of heavy metals in rivers. Full article

Microplastics (MPs) are ubiquitous in aquatic environments, soils, and beach sediments, demonstrating a remarkable ability to adsorb dissolved organic matter (DOM). Although there are methods for extracting DOM from water, the approaches for directly extracting DOM from microplastics have not been thoroughly investigated, and the characterization of DOM adsorbed on microplastics is also insufficient. In this study, five different types of microplastic samples were collected from each of five environmental media (water and sediment), and finally 25 samples were obtained. This paper comparatively assessed the extraction efficiency of DOM from MPs with various solvents by using total organic carbon (TOC), culminating in the development of a sodium pyrophosphate-NaOH solution extraction method optimized for DOM. The morphology, material and environmental medium of microplastics were the three primary factors affecting the adsorption of DOM on microplastics, with the highest enrichment ratio of 1.4–1.8 times for extruded polyethylene microplastics (EPE-MPs) characterized by their porous structure in the flowing water environment. The molecular weight of DOM adsorbed on microplastics showed a multi-modal distribution pattern with great dissimilarities among the different environmental media. Gel permeation chromatography (GPC) indicated that the weight-average molecular weight (M_w) of DOM was 2750–4552 Da for river MPs, 2760–5402 Da for Qiantang River MPs, 1233–5228 Da for East China Sea MPs, 440–7302 Da for soil sediment MPs and 438–6178 Da for beach sediment MPs, respectively. Excitation-emission matrix-parallel factor analysis (EEM-PARAFAC) identified that tyrosine-like substances with high excitation in region IV and low excitation in region I were predominantly adsorbed on MPs, followed by tryptophan-like substances with low excitation in region II and protein-like substances in region IV, while humic- and fulvic-like substances in regions V and III, respectively, exhibited the least adsorption affinity. The findings underscored the critical need to comprehensively consider the interactions between MPs and DOM and their environmental impacts in pollution control strategies. Full article

The efficient characterization of compost quality is essential for optimizing its application in agriculture and soil improvement. In this study, a correlation-based approach was employed to evaluate relationships between physicochemical properties, structural features, and reactivity indicators of compost extracts—fulvic acid-like (FA-L), humic acid-like (HA-L), and dissolved organic matter (DOM)—and their respective bulk composts. The goal was to identify key compost parameters that can serve as reliable predictors of humic substance composition and bioactivity, thereby reducing reliance on labor-intensive humic substance extractions. A comprehensive set of elemental, spectroscopic (UV-vis, ATR-FTIR, ¹H-NMR), and thermal (TGA-DSC) analyses were conducted to assess the composition and stability of the extracts. Strong correlations were found between compost oxidation state (C_oxi/C), cation exchange capacity (CEC), thermal stability, and the structural characteristics of humic substances-like (HS-L) fractions, suggesting that direct compost characterization can effectively predict humic substance reactivity and agronomic potential. The findings also align with a previously developed Compost Quality Index (CQI), reinforcing the functional role of humic substances in soil fertility and nutrient retention. By establishing a simplified yet robust compost assessment framework, this study advances the potential for efficient, cost-effective evaluation methodologies for compost quality. Full article

Plant biostimulants (PBs) have been considered the new wave for ecological intensification and sustainability, but are they sustainable? They increase nutrient use efficiency and reduce the impact of abiotic stress in plants. However, commercially available PBs based on humic substances are obtained using non-renewable sources of organic matter. At the same time, the microbial inoculants include a discussion of the properties of microorganisms and formulation design, as well as standards of purity and process control. Farmers depend on biological inputs like others to generate additional income for agribusiness. We produced a composite PB using humic substances isolated from vermicompost with KOH 5% and microbial consortia of plant growth-promoting bacteria (H. seropedicae, G. diazotrophicus, Bacillus spp.) grown in a simple medium with molasses and fishmeal as sources of C and N, respectively, in a homemade reactor at 37 °C for 36 h. The on-farm PB was applied directly in a passion fruit trial, and plant health and yield were monitored. The plants treated with the PB showed decreased visual symptoms of pests and diseases concurrent to higher activities of the enzymes used to monitor the induction of the plant resistance system (1,3-β glucanase, peroxidase, and phenylalanine ammonia-lyase). Plants treated with the PB yielded more than 50% more passion fruit than the control in soil with natural low fertility, fertilized with vermicompost. It is possible to produce PBs directly on the farm, leveraging locally available resources and simple technologies to sustainably enhance plant health and productivity. Full article

The environmental release of zinc oxide nanoparticles (ZnO-NPs) may have consequences for ecosystems. The behavior and environmental effects of ZnO-NPs could change due to their interactions with other existing substances. This research explored how the presence of coexisting organic pollutants (like tetrabromobisphenol-A (TBBPA)), electrolytes (such as NaCl and CaCl₂), natural organic materials (including humic acid (HA)), and bovine serum albumin (BSA) in simulated water affected the behavior of ZnO-NPs. Various characterization techniques were used to analyze the size, shape, purity, crystallinity, and surface charge of ZnO-NPs following interactions (after one day, one week, two weeks, and three weeks) at pH 7. The findings demonstrated changes in both the size and zeta potential of the ZnO-NPs in isolation and when TBBPA and electrolytes were included in the suspension. The size and surface charge exhibited different variations across fixed concentrations (5 mM) of various electrolytes. HA and BSA contributed to the dispersion of ZnO-NPs by affecting the zeta potential. These dispersion effects were also observed in the presence of TBBPA and salts, attributed to their substantial aliphatic carbon content and complex structures. Potential interaction forces that could explain the adsorption of TBBPA include cation bridging, hydrophobic interactions, hydrogen bonding, electrostatic interactions, and van der Waals forces. The co-occurrence of organic pollutants (TBBPA) and natural organic compounds (HA and BSA) can alter the surface properties and behavior of ZnO-NPs in natural and seawater, aiding in the understanding of the fate and impact of engineered nanoparticles (such as ZnO-NPs) in the environment. Full article

Humic substances (HSs) are emerging as multifunctional natural catalysts in sustainable agriculture, offering novel opportunities to enhance soil health, plant productivity, and environmental resilience. This review synthesizes recent insights into the chemical diversity, biological mechanisms, and ecological impacts of HSs, presenting a new perspective on their role as dynamic agents in agroecosystems. Derived from decomposed organic matter, HSs regulate critical processes such as nutrient cycling, carbon sequestration, and pollutant detoxification. Unlike plant and microbial biomass, which undergo rapid mineralization due to their active dynamism, HSs exhibit significant resistance to biodegradation, leading to a prolonged residence time in soil that spans years or even centuries. This stability allows HSs to maintain their functional roles over extended periods, contributing to long-term soil health and ecosystem sustainability. Their integration into agricultural systems has demonstrated profound effects, including improved soil structure, increased water retention, and the stimulation of microbial activity, which collectively bolster plant stress tolerance and yield. Notably, it has been proposed that HSs exhibit hormone-like properties, influencing plant signaling pathways to enhance root architecture and nutrient acquisition. Moreover, HSs contribute to environmental remediation by regulating the leaching of heavy metals, mitigating nutrient runoff, and fostering climate resilience. This review highlights the synergistic potential of combining HSs with organic amendments like compost and biochar, positioning HSs as a cornerstone of regenerative farming practices. Addressing challenges such as variability in composition and application methods, the discussion underscores the urgency of developing standardized approaches to harness their full potential. By framing HSs as versatile and adaptive tools, this review paves the way for advancing sustainable agricultural systems while addressing global challenges like food security and climate change. Full article