How to solve the contradiction between the efficiency and adsorption rate of porous materials in adsorbing pollutants has always been one of the focus issues. In this study, the small landscape cypress trees structure like biomimetic of a hierarchical and dual morphology 3D porous HA-based aerogel was designed and synthesized to use humic acid (HA), pectin (PE) and chitosan (CTS) as raw materials, which it was formed by the disorderly overlapping of lamella composed of fiber networks in 3D space. Due to its special microstructure, it can be used like separation membrane, which allowing for rapid adsorption of pollutants in the water while the water flow passes through quick. In general, this work provides a new concept for owning fast adsorption rate and efficient adsorption of porous materials of preparation to use green method.

High level of aluminum content in Enteromorpha prolifera posed a growing threat to both its growth and human health. This study focused on exploring the factors, impacts, and process of removing aluminum from Enteromorpha prolifera using humic acid. The results showed that under experimental conditions of 0.0330 g·L-1 humic acid concentration, pH 3.80, 34 °C, and a duration of 40 min, the removal rate was up to 80.18%. The levels of major flavor components, proteins, and amino acids in Enteromorpha prolifera increased significantly after treatment, while polysaccharides and trace elements like calcium and magnesium decreased significantly. Infrared spectroscopy demonstrated that the main functional groups involved in binding with Al3+ during humic acid adsorption were hydroxyl, carboxyl, phenol, and other oxygen-containing groups. The adsorption process of Al3+ by humic acid was a spontaneous phenomenon divided into three key stages: fast adsorption, slow adsorption, and adsorption equilibrium, which resulted from both physical and chemical adsorption effects. This study provided a safe and efficient method in algae metal removal.

Tylosin tartrate, a macrolide antibiotic, is one of a class of emerging contaminants that have been detected in natural bodies of water since they are not easily removed by conventional treatment processes. In this study, the direct and indirect photodegradation of tylosin tartrate was analyzed to understand the role of reactive oxygen species and organic matter that may be present in surface waters. While direct photolysis caused negligible degradation (k = (9.4 ± 1.8) × 10-5 s-1), the addition of 0.4 M hydrogen peroxide (k = (2.18 ± 0.01) × 10-4 s-1) or usage of the photo-Fenton process (k = (2.96 ± 0.02) × 10-4 s-1) resulted in greater degradation. The degradation was maximized by combining tylosin tartrate with an experimentally determined optimal concentration of humic acid (15 mg/L), which readily produced singlet oxygen and increased the overall degradation (k = 1.31 ± 0.05) × 10-3 s-1) by means of indirect photolysis. Absolute pseudo-first-order bimolecular reaction rate constants for tylosin tartrate were measured with singlet oxygen [(4.7936 ± 0.0001) × 105 M-1 s-1] and hydroxyl radical [(5.2693 ± 0.0002) × 109 M-1 s-1] using competition kinetics, and when combined with data on concentration of the reactive oxygen species, showed that the hydroxyl radical makes a contribution to the degradation that is approximately eleven orders of magnitude greater than singlet oxygen.

The coexistence of emerging pollutants and dissolved organic matter in wastewater complicates the transformation and generation of disinfection byproducts (DBPs) during chlorination treatment, which is essential for effective water quality evaluation and chlorination optimization. This study used fluoxetine (FLX) and humic acid (HA) as representative substances to analyze changes in their chemical characteristics and zebrafish embryonic developmental toxicity under different chlorination conditions. The analysis of the fluorescence characteristics and Fourier transform ion cyclotron resonance mass spectrometry indicated that chlorination treatment increased the aromatic compound content of the HA solution. FLX addition further increased the presence of aromatic ring structures and oxidized molecules, resulting in the formation of numerous Cl-DBPs with highly unsaturated and phenolic structures. Moreover, different responses in zebrafish embryo development and behavior were found with FLX, HA, and FLX + HA exposures. Cardiotoxicity was linked to changes in the concentration of cTn-I protein and expression of various genes. Prolonged chlorination conditions showed higher toxicities. Correlation analysis found a weak relation between chemical indicators and toxicity data, indicating that both analysis methods need to be considered when analyzing the impact of the chlorination. Further, a combination of chemical analyses and toxicity tests revealed that the FLX + HA solution with chlorination conditions of 3 mg/L for 30 min had lower chemical and toxic effects in this experiment. This study provides valuable scientific insights for the safe discharge of chlorinated water containing FLX and dissolved organic matter, as well as guidance for optimizing chlorination parameters in wastewater treatment.

The increasing utilization of zinc oxide nanoparticles (ZnO-NPs) in many consumer products is of concern due to their eventual release into the natural environment and induction of potentially adverse impacts. The behaviour and environmental impacts of ZnO-NPs could be altered through their interactions with environmentally coexisting substances. This study investigated the changes in the behaviour of ZnO-NPs in the presence of coexisting organic pollutants (such as perfluorooctanoic acid [PFOA]), natural organic substances (i.e., humic acid [HA]), and electrolytes (i.e., NaCl and CaCl2) in simulated waters. The size, shape, purity, crystallinity, and surface charge of the ZnO-NPs in simulated water after different interaction intervals (such as 1 day, 1 week, 2 weeks, and 3 weeks) at a controlled pH of 7 were examined using various characterization techniques. The results indicated alterations in the size (such as 162.4 nm, 1 day interaction to >10 µm, 3 weeks interaction) and zeta potential (such as -47.2 mV, 1 day interaction to -0.2 mV, 3 weeks interaction) of the ZnO-NPs alone and when PFOA, electrolytes, and HA were present in the suspension. Different influences on the size and surface charge of the nanoparticles were observed for fixed concentrations (5 mM) of the different electrolytes. The presence of HA-dispersed ZnO-NPs affected the zeta potential. Such dispersal effects were also observed in the presence of both PFOA and salts due to their large aliphatic carbon content and complex structure. Cation bridging effects, hydrophobic interactions, hydrogen bonding, electrostatic interactions, and van der Waals forces could be potential interaction forces responsible for the adsorption of PFOA. The presence of organic pollutants (PFOA) and natural organic substances (HA) can transform the surface characteristics and fate of ZnO-NPs in natural and sea waters.

2H-phase molybdenum disulfide (2H-MoS2) has been considered to be a chemically stable two-dimensional (2D) nanomaterial. Nonetheless, the persistence of 2H-MoS2 in the presence of environmental redox-active matrices, such as naturally occurring oxidants (e.g., manganese dioxide (MnO2)) and natural organic matter (NOM), remains largely unknown. Herein, we examined the interplay between 2H-MoS2, MnO2 (a common natural oxidant), and NOM species (i.e., Aldrich humic acid (ALHA) and Suwannee River natural organic matter (SRNOM)). The results show that MnO2 accelerates the oxidative dissolution of 2H-MoS2, regardless of the presence of dissolved oxygen. The effect of NOM on the MnO2-induced fate of 2H-MoS2 was found to depend on its affinity for 2H-MoS2 and the functionality of NOM. ALHA preferentially adsorbed on hydrophobic 2H-MoS2 nanosheets due to the enrichment of reductive polycyclic aromatics and polyphenolic constituents. The preferential ALHA adsorption counteracted the MnO2-triggered oxidative transformation of 2H-MoS2, as revealed by the cathodic response of 2H-MoS2 (i.e., decreased the open circuit potential by 0.0338 V) and the emergence of reductive Mo‒C bonds at 228.8 and 231.9 eV upon the addition of ALHA. This work evaluated the persistence of 2H-MoS2, illustrating its susceptibility to decomposition by naturally occurring oxidants and the influence of NOM on it. These findings are crucial for revealing the fate and transport of MoS2 in aquatic environments and provide guidelines for related applications in natural or engineered systems for MoS2 and potentially other 2D materials.

Soil organic carbon (SOC) is known to vary among different ecosystems and soilscapes, yet the degree of variation remains uncertain. Comparing SOC levels in undisturbed ecosystems like forests with those in gradually altered ecosystems can provide valuable insights into the impact of land use on carbon dynamics. This study aimed to evaluate the effects of different land uses on soil fertility parameters in the tropical region of Kerala, focusing on forests as well as cultivated agricultural landscape such as coconut, pepper, tapioca, acacia plantations, and mixed home garden cropping systems. Significant variations were observed among different crops and land use systems in terms of soil fertility. Forests exhibited the highest SOC content at 3.78 g kg-1, while acacia plantations showed the lowest at 0.76 g kg-1. Additionally, various soil properties such as different carbon fractions (e.g., humic acid, fulvic acid), total nitrogen, carbon, available nutrients, physical properties, aggregate size fractions, microbial biomass carbon, and spectral signatures differed significantly across the different land uses. These findings suggest a decline in soil fertility in altered ecosystems compared to adjacent forest soils, highlighting the vital role of forests in conserving natural resources and maintaining soil health. In addition, among the different landscapes studied, mixed cropping systems of home gardens sustained soil fertility better than monocropping systems. The observed variations in soil physicochemical properties among different land use types indicate a threat to sustainable crop production. Effective management practices aimed at improving soil fertility and sustaining crop production in these altered ecosystems are essential. This study highlights the importance of adopting appropriate management strategies to conserve soil health and ensure sustainable crop production in tropical landscapes like Kerala. The holistic approach adopted in this study, encompassing a wide range of soil fertility parameters across various land uses, along with its implications for sustainable land management, adds significant novelty and relevance to the existing literature on soil dynamics in tropical regions like Kerala.

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 (O2 -, 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 mobility of heavy metals in natural soil systems can be affected by the properties and compositions of those systems: the content and quality of organic matter as well as the character of inorganic constituents. In this work, the diffusion of copper(II) ions in humic hydrogels with incorporated calcium(II), magnesium(II), and iron(III) ions was investigated. The methods of instantaneous planar source and of constant source were used. Experimental data yielded the time development of the concentration in hydrogels and the values of effective diffusion coefficients. The coefficients include both the influence of the hydrogel structure and the interaction of diffusing particles with the hydrogel. Our results showed that the presence of natural metal ions such as calcium, magnesium, or iron can strongly affect the diffusivity of copper in humic systems. They indicate that the mobility of copper ions depends on their concentration. The mobility can be supported by higher contents of copper in the system. While the incorporation of Ca and Mg resulted in the decrease in the diffusivity of copper ions, the incorporation of Fe(III) into humic hydrogel resulted in an increase in the diffusivity of Cu(II) in the hydrogel in comparison with pure humic hydrogel.

Resource recovery of valuable metals from spent lithium batteries is an inevitable trend for sustainable development. In this study, external regulation was used to enhance the tolerance and stability of strains in the leaching of spent lithium batteries to radically improve the bioleaching efficiency. The leaching of Li, Ni, Co and Mn increased to 100 %, 85.06 %, 74.25 % and 69.44 % respectively after targeted cultivation with HA as compared to the undomesticated strain. In the process of microbial leaching of spent lithium batteries, the metabolites in the Ⅰ, Ⅳ, and Ⅴ regions of the metabolism of the undomesticated bacterial colony had a positive correlation to the dissolution of spent lithium batteries. The metabolites of Ⅰ, Ⅱ, and Ⅴ regions were directly affected by the HA domesticated flora on the dissolution of spent lithium batteries. The excess metabolism of protein substances can significantly promote the reduction of Ni, Co, Mn leaching, and at the same time in the role of a large number of humic substances complexed the toxic metal ions in the system, to ensure the activity of the bacterial colony. It can be seen that the bacteria were domesticated by humic acid, which promoted the bacteria\'s own metabolism, and the super-metabolised EPS promoted the solubilisation of spent lithium batteries.