Compared to the limited performance of other high-efficiency urea products, humic acid urea (HAU) increased the grain yield of winter wheat as well as of summer maize. However, the effect of adding different amounts of humic acid (HA) on the fate of urea and comprehensive economic and environmental evaluations remains unclear. Four treatments (no urea (CK), common urea (U), HAU0.5, and HAU5) were compared in a 2-year winter wheat-summer maize rotation system. Compared to U, the grain yield of HAU treatments increased by 4.48-11.25 %, regardless of crop type, planting year, or HA addition level; this was partly attributable to the increased storage of soil available N, as confirmed by a simultaneous 15N tracing microplot experiment in the first winter wheat season. HAU inhibited the loss of reactive N (NH3 volatilization, N2O emission, and NO3--N leaching loss). The C footprint based on the yield and areas calculations for HAUs was 7.01-13.48 % and 3.53-5.54 % lower than that of U, respectively. Annual environmental damage costs and annual net ecosystem economic benefits were decreased and increased by 14.89 %- 19.11 % and 6.38 %-9.23 %, respectively. Few agronomic and environmental differences were found between HAU5 and HAU0.5, although the former locked more 15N nutrients in the topsoil. This combined experiment using 15N tracer and field lysimeters showed that more nutrients from HAU were absorbed by crops and converted into grains, reducing the environmental risk of greenhouse gas emissions due to the release of unused nutrients from common U into farmland.

Soil polycyclic aromatic hydrocarbons (PAHs) and cadmium (Cd) pollution poses severe threats to environment security. Previous studies have reported that both nanoparticles and humic acid (HA) have ability to phytoremediate of pyrene/Cd in soil. Here, pot experiments were conducted to investigate the effects of TiO2NPs and humic acid addition on the applicability Hylotelephium spectabile of remediation for pyrene-Cd co-contaminated soil and the corresponding plant growth. The results show that TiO2NPs with HA can mitigate the damage to plant physiology. TiO2NPs-HA is more suitable to be applied on composite soil where Cd pollution is dominant and pyrene pollution is light. Furthermore, the coating of TiO2NPs with HA enhances the availability of Cd and expands root xylem, allowing roots to absorb and accumulate Cd in large quantities finally. This study aims to establish a theoretical foundation for the implementation of sedum plant in remediating soil contaminated with multiple pollutants.

This paper investigated the use of magnesium phosphate cement (MPC) for solidifying sludge with different humic acid (HA) content (ranging from 0 to 4.5%) and explored the solidification mechanism. Fluidity, setting time, unconfined compressive strength (UCS), the strength formation mechanism, and the spontaneous imbibition process of solidified sludge (SS) were studied. The results indicate that MPC can be used as a low-alkalinity curing agent. As the HA content increases, fluidity and setting time also increase, while hydration temperature and strength decrease. Additionally, the failure mode of SS transitions from brittleness to ductility. The strength of SS is composed of the cementation strength provided by MPC hydration products, matric suction, osmotic suction, and the structural strength of the sludge. MPC reduces the structural strength caused by the shrinkage of pure sludge under the action of matric suction, but the incorporation of MPC significantly improved the strength when the sludge is eroded by water. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the sludge and MPC can form a dense solid body, forming various hydration products, and synergistically improve the mechanical properties of the sludge. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In China, high copper (Cu) and low organic matter often occur in some citrus orchard soils. However, the underlying mechanisms by which humic acid (HA) stimulates growth and mitigates Cu toxicity of citrus seedlings are unclear. After being treated with 0, 0.1, or 0.5 mM sodium humate and 0.5 or 400 mu M CuCl2 (Cu excess) for 24 weeks, sweet orange [Citrus sinensis (L.) Osbeck cv. Xuegan] seedlings were used to examine the impacts of HA-Cu interactions on seedling growth, nutrient uptake, leaf pigments, and photosynthetic performance that was revealed by chlorophyll a fluorescence transient. Copper excess reduced root, stem, and leaf dry weight (DW) by 42.4%, 65.4%, and 61.6%, respectively at 0 mM HA, and by 17.3%, 25.4%, and 31.4%, respectively at 0.5 mM HA; and that the levels of Cu in leaves, stems, and roots declined with elevating HA supply. Copper excess caused some rotten and dead fibrous roots at 0 mM HA, but not at 0.5 mM HA. Adding HA lowered Cu uptake per root DW (UPR), the levels of Cu in leaves, stems, and roots, and the competition of Cu2+ with Mg2+ and Fe2+, and therefore mitigated root impairment caused by Cu excess. The HA-mediated alleviation of root damage caused by Cu excess increased the uptake per plant and UPR of nitrogen, potassium, magnesium, phosphorus, calcium, sulfur, boron, and manganese, and therefore alleviated Cu excess-induced decline in seedling growth, impairment to leaf photosynthetic electron transport chains, and decrease in leaf pigments. For 0.5 mu M Cu-treated seedlings, adding HA promoted seedling growth by improving root nutrient uptake and leaf photosynthetic performance. Cu excess aggravated the impacts of HA supplementation on seedling growth, leaf photosynthetic performance, and root nutrient uptake.

Background With the progress of industrialization and urbanization, cadmium (Cd) pollution in farmland is increasingly severe, greatly affecting human health. Sunflowers possess high resistance to Cd stress and great potential for phytoremediation of Cd-contaminated soil. Previous studies have shown that humic acid (HA) effectively mitigates plant damage induced by Cd; however, its alleviating effects on sunflower plants under Cd stress remain largely unknown. Results We employed four different concentrations of HA (50, 100, 200, and 300 mg L-1) via foliar application to examine their ability to alleviate Cd stress on sunflower plants' growth, chlorophyll synthesis, and biochemical defense system. The results revealed that Cd stress not only reduced plant height, stem diameter, fresh and dry weight, and chlorophyll content in sunflower plants but also altered their chlorophyll fluorescence characteristics compared to the control group. After Cd stress, the photosynthetic structure was damaged and the number of PSII reactive centers per unit changed. Application of 200 mg L-1 HA promotes sunflower growth and increases chlorophyll content. HA significantly enhances antioxidant enzyme activities (SOD, POD, CAT, and APX) and reduces ROS content (O-2(-), H2O2 and -OH). Totally, Application of 200 mg L-1 HA had the best effect than other concentrations to alleviate the Cd-induced stress in sunflower plants. Conclusions The foliar application of certain HA concentration exhibited the most effective alleviation of Cd-induced stress on sunflower plants. It can enhance the light energy utilization and antioxidant enzyme activities, while reduce ROS contents in sunflower plants. These findings provide a theoretical basis for using HA to mitigate Cd stress in sunflowers.

The objective of this study is to explore the novel use of natural polymers like Humic acid, Lignin, and Lignite based hydrogels for the formulation of pesticides and fertilizers that would reduce the residues in soil and run-off water that pose a threat to human health and the environment. We synthesized hydrogels by grafting Humic acid, lignin, and lignite onto acrylic acid with N ' N-methylene bisacrylamide (MBA) for the ex-situ encapsulation of thiamethoxam, a common pesticide. Various characterization techniques including Fourier-transform infrared spectroscopy, Carbon-13 Solid-state Cross-Polarization Magic Angle Spinning Nuclear Magnetic Resonance, X-ray diffraction, Thermogravimetric Analysis, and Rheology were employed. The release kinetics of thiamethoxam in water from the developed formulations were analyzed using the Korsmeyer- Peppas model and the Weibull model. Humic acid and lignin-based hydrogels exhibited a long-sustained release for 49 hours, followed by lignite-based hydrogels (38 hours). According to ANOVA results, the change of biopolymer proved to be an effective factor in reducing the water evaporation rate, which decreased from 99 % to 72.85 % in the soil amended with synthesized hydrogels. In conclusion, the novel formulations of humic acid, lignin, and lignite exhibit potential as slow-release vehicles for pesticides and fertilizers. This study provides valuable insights for the research community, addressing the need to develop effective strategies for mitigating pesticide residues in soil and water bodies. Humic acid, lignin, and lignite grafted poly(sodium acrylate) hydrogels have been synthesized and characterized by 13C CPMAS NMR, FT-IR, XRD, SEM, TGA, and Rheology. The release kinetics of thiamethoxam is studied using the Korsmeyer-Peppas and Weibull models. This study will reduce the environmental influences of pesticide runoff into the water and bring humic acids, and lignite out of the traditional soil context by applying them in modern fields along with lignin. image

The Hetao irrigation region is located in Inner Mongolia, China, within a dry and semi-dry region. This region suffers from poor agricultural productivity and environmental damage due to the presence of saline soil. To explore the growth of salty lands using a more environmentally friendly method, this research employed three eco-conscious amendments to improve the soil. These include flue gas desulfurization gypsum (S), humic acid (H), and biochar (C). During a two-year study, the amendments were utilized to enhance the soil quality for planting sunflowers. Humic acid was used prior to every seedling season, whereas the remaining two substances were only used once. These additions increased the soil's water-holding capacity, reduced soil salinity during sunflower growth, and improved the macroaggregate proportion. The most effective treatment for decreasing the soil's salt content after the seedling stage was the application of humic acid (0.6 t ha(-1)). Biochar (15 t ha(-1)) decreased the soil's bulk density (from 1.49 to 1.34 g cm(-3)) and mostly increased the sunflower seed yield up to 3133-3964 kg ha(-1). Humic acid addition significantly increased the aggregate (>0.25 mm) content up to 27.88% after the experiment, but it led to a lower seed yield (2607-3686 kg ha(-1)). In 2019, the temperature was lower compared to 2018, which may have led to a reduction in the yield. However, these three amendments could potentially increase yields by more than conventional methods. These three environmentally friendly amendments are useful for improving saline soil and increasing yields. More studies are required to understand their impacts on larger areas and over extended periods.

This article a synthesis of humic acid with the obtaining of potassium humate based on coal waste from the Lenger deposit. Accumulated industrial waste heavily pollutes the environment and has a direct impact on all living things. The accumulation of waste in landfills increases the pollution level of the atmosphere, soil, groundwater, and surface water, destroys the functioning of ecosystems, and damages agriculture and construction. A sieve analysis was carried out to study the fine fractions of coal waste, and a scanning electron microscope analysis was performed to study the mineralogical, structural state and X-ray chemical phase composition. The chemical composition of coal waste was studied using differential thermal analysis during heat treatment. The optimal parameters of the process for obtaining humic acids are established, and the results of experimental work are presented. The results are confirmed by mathematical planning of the experiment using the method of orthogonal plan of the second order. The mathematical planning results were tested according to the Student and Fischer criteria. Based on the conducted studies, it was identified that the degree of extraction of humic acid reaches up to 95.90% in terms of the organic phase, and the concentration of humic acid is 49.13%. From the humic acids obtained using potassium hydroxide, potassium humate was synthesized. The potassium humate obtained in its composition has fertilizer properties. Therefore, the obtained potassium humate will be used for the production of humic fertilizers to improve soil fertility and crop yields. The synthesis of humic acids with the production of potassium humate is aimed at reducing the accumulated industrial waste, which in turn allows you to regulate and improve the ecological situation and green ecology in the region.

The boreal forests of Russia are one of the largest forest areas on the planet. As a result of climate change, the rate of carbon sequestration and stabilization of organic matter are important indicators of environmental conservation. To understand mechanisms of stabilization and the structure of soil organic carbon, the molecular-weight (MW) distribution of humic acids (HAs) in soils of the central deciduous-forest zone of boreal forests (Chernevaya taiga, transitional ecotone forest, coniferous forest) was studied. Analysis of the MW distribution of HAs was conducted using size-exclusion chromatography. This approach allowed us to obtain the distribution of high-, medium-, and low-molecular fractions of HAs. It has been revealed that the content of the low-MW fraction prevails over the content of the medium- and high-MW fractions of HAs, which indicates the process of stabilization in soil organic matter. The accumulation of low-molecular-weight fraction occurs with the aromaticity increase in HAs, which indicates that HAs with a relatively high proportion of aromatic fragments have smaller hydrodynamic radius and a lower MW. It has been statistically substantiated that the low-molecular-weight fraction correlates with the content of aromatic compounds and carboxyl structural fragments of HAs, which indicates the resistance of the soil organic matter of Chernevaya taiga to biodegradation.

Humic substances (HSs) from themire peat soils of the forest-tundra zone of the European northeast part of Russia have been characterized in terms of molecular composition. This was accomplished using solid-state C-13 nuclear magnetic resonance (C-13 NMR) techniques and electron spin resonance (ESR) spectroscopy. The composition depended on the intensity of cryogenic processes in the active layer, the quality of the humification precursors (the degree of peat material transformation), and the biochemical selection of aromatic fragments during humification. Humic acids (HAs) and fulvic acids (FAs) of the peat soils showed the presence of compounds with a low extent of condensation and a low portion of aromatic fragments, which increased with depth. A higher proportion of aliphatic carbon species was found in the HAs, indicating a low degree of organic matter stabilization. Based on the data from the two types of peat soils, we suggest that particular changes in the proportion of aromatic and unoxidized aliphatic fragments on the border of the bottom of the active layer and permafrost layers can be used as markers of current climatic change. (C) 2017 Elsevier B.V. All rights reserved.