Divergent soil P accrual in ectomycorrhizal and arbuscular mycorrhizal trees: insights from a common garden experiment in subtropical China.

Tree species establish mycorrhizal associations with both ectomycorrhizal (EM) and arbuscular mycorrhizal fungi (AM), which play crucial roles in facilitating plant phosphorus (P) acquisition. However, little attention has been given to the effects of EM and AM species on soil P dynamics and the underlying mechanisms in subtropical forests, where P availability is typically low. To address this knowledge gap, we selected two EM species (Pinus massoniana - PM and Castanopsis carlesii - CC) and two AM species (Cunninghamia lanceolata - Chinese fir, CF and Michelia macclurei - MM) in a common garden established in 2012 in subtropical China. We investigated soil properties (e.g., pH, soil organic carbon, total nitrogen, and dissolved organic nitrogen), soil P fractions, phospholipid fatty acids (PLFAs), enzyme activities, foliar manganese (Mn) concentration, and foliar nutrients and stoichiometry. Our findings revealed that soils hosting EM species had higher levels of resin P, NaHCO3-Pi, extractable Po, total P, and a greater percentage of extractable Po to total P compared to soils with AM species. These results indicate that EM species enhance soil P availability and organic P accumulation in contrast to AM species. Moreover, EM species exhibited higher P return to soil (indicated by higher foliar P concentrations) when compared to AM species, which partly explains higher P accumulation in soils with EM species. Additionally, resin P showed a positive correlation with acid phosphatase (ACP) activity, whereas no correlation was found with foliar Mn concentration, which serves as a proxy for the mobilization of sorbed soil P. Such findings indicate that organic P mineralization has a more substantial impact than inorganic P desorption in influencing P availability in soils hosting both EM and AM species. In summary, our study contributes to a more comprehensive understanding of the effects of mycorrhizal associations on soil P accumulation in subtropical forests and provide valuable insights into plant-soil interactions and their role in P cycling in regions with limited P availability.

Recycling of sewage sludge in clay-free thermal insulation brick: assessment of microstructure, performance, and environment impact.

Recycling municipal sewage sludge in fired bricks not only contributes to environmental protection, but is also an alternative to natural clay resource. The complex compositions of sludge have a great influence on the brick property. This work presents a systematical investigation on fired bricks made only with sludge and shale. The physicochemical properties of the raw mixtures, macroscopic performance, microstructure, and its evolution were quantitatively determined. The coordination between shale and sludge enables the blend of raw materials to achieve the desired gradation and plasticity. Although a reduction in compressive strength was observed, the open porosity was increased to 31.6% and thermal conductivity was reduced to 0.51 W·(m·K)-1, indicating the benefit to the performance of lightweight thermal insulation bricks. The fitting results confirm the pore-forming effect induced by the organic matter in the sludge. The obtained bricks possess good performance, especially in thermal insulation properties, and environmental and economic benefits.

Evaluating the capability of municipal solid waste separation in China based on AHP-EWM and BP neural network.

With the increase in municipal solid waste (MSW), most cities face solid waste management issues. In this study, the analytic hierarchy process (AHP) and artificial neural network (ANN) models were improved to assess the MSW separation capability based on 18 selected indicators of solid waste separation in 15 cities in China. The entropy weight method (EWM) was used in AHP to optimize and determine the indicators and then evaluate their weights, which showed that the general public budget expenditure had the highest weight (0.5239). This implied that the MSW separation capability could be mainly influenced by government financial support. ANN based on scan optimization and machine learning methods were established (R2 = 0.9992) to predict the missing indicators. The mapping relationship between MSW separation indicators and capabilities was also significantly improved from R2 = 0.5317 to R2 = 0.9993, thereby increasing the prediction accuracy of MSW separation capabilities to 95.15%. Thus, this research provides a new avenue for MSW separation and establishes a combined model to predict the separation capability in practical applications.

Enrofloxacin perturbs nitrogen transformation and assimilation in rice seedlings (Oryza sativa L.).

The extensive use of antibiotics worldwide has led to phytotoxicity and high risks to humans. Although research on the physiological toxicity of antibiotics is extensive, its influence on plant nitrogen uptake and assimilation remains unclear. The effect of enrofloxacin on nitrogen transformation and assimilation in rice (Oryza sativa L.) seedlings was investigated in this study. Enrofloxacin had no significant effect on rice growth, nitrogen assimilation and metabolism at low concentration, while significant changes were observed in high concentration. The growth of rice seedlings was inhibited, nitrate uptake was enhanced and nitrogen content increased significantly in both shoots and roots in enrofloxacin (800 µg L-1) treatment. Furthermore, enrofloxacin promoted the activity of enzymes related to nitrogen assimilation, including nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase. High enzyme activity resulted in an increase in intermediate products and protein content, suggesting that rice seedlings may detoxify enrofloxacin stress through amino acid binding and nitro-oxidative stress might be one of the reasons of phenotype change. Gas chromatography-mass spectrometry results revealed that different types of metabolites in both shoots and roots increased with enrofloxacin stress. Specifically, glycine, serine, and threonine metabolism; aminoacyl-tRNA biosynthesis; alanine, aspartate, and glutamate metabolism; butanoate metabolism; glyoxylate and dicarboxylate metabolism in shoot; and tyrosine metabolism and citrate cycle in root were affected. Moreover, a significant correlation between nitrogen content, nitrogen assimilation enzyme activity, and metabolite content was observed. Collectively, these findings reveal the potential risks of using reclaimed wastewater irrigation and/or antibiotic-containing animal fertilizers on crops.

The Failure Mechanisms of Precast Geopolymer after Water Immersion.

Precast geopolymers with lower water/binder (0.14), which mainly consists of alkali solution, fly ash (FA) and steel slag (SS), were manufactured through molding pressing technology. The failure mechanisms of precast geopolymers after water immersion were studied by testing the loss of compressive strength, the pH of the leaching solution, the concentration of ions (Na+, Ca2+, Si4+ and Al3+), the evolution of phases, pore structure and morphology, and further discussion of the regulation evolution was performed. The results show that the harmful pores (>50 nm) of geopolymers progressively decrease from 70% to 50% after 28 days of water immersion when the content of steel slag increases from 0 to 80 wt.%. Compressive strength of geopolymers sharply reduces in the first 3 days and then increases during the water immersion process, but the phase composition varies slightly. Furthermore, increasing the content of steel slag could decrease the total porosity and further prevent the water resistance.

Influence of Mineral Additives on the Efflorescence of Ettringite-Rich Systems.

Efflorescence is aesthetically undesirable to all cementitious materials products and mainly results from the carbonation of hydrates and salt precipitation. Alternative binders without portlandite formation theoretically have much lower efflorescence risk, but in practice, the efflorescence of ettringite-rich systems is still serious. This study reports the impacts of mineral additives on the efflorescence of ettringite-rich systems and the corresponding microstructural evolution. The effects of silica fume, limestone powder, and diatomite on efflorescence and the capillary pore structure of mortars were investigated from a multi-scale analysis. The composition and microstructure of efflorescent phases were revealed by optical microscope (O.M.), in-situ Raman spectroscopy, and Scanning Electron Microscopy (SEM). Results indicate that the addition of mineral additives can efficiently inhibit the efflorescence of reference, especially with silica fume. Similar to the ettringite-rich system, the efflorescence substances of all modifies are composed of ettringite and CaCO3, indicating that the addition of mineral admixture does not lead to chemical reactions, lower capillary absorption coefficient of mineral additives modified specimen, the denser pore structure and the lower efflorescence degree.

A Comprehensive Study on the Hardening Features and Performance of Self-Compacting Concrete with High-Volume Fly Ash and Slag.

The main concern of this work is to evaluate the influences of supplementary cementitious materials (fly ash, slag) and a new type of polycarboxylate superplasticizer containing viscosity modifying agents (PCE-VMA) on the performance of self-compacting concrete (SCC). The workability, hydration process, mechanical property, chloride permeability, degree of hydration and pore structure of SCC were investigated. Results indicate that the addition of fly ash and slag slows down early hydration and decreases the hydration degree of SCC, and thus leads to a decline in compressive strengths, especially within the first 7 days. The addition of slag refines pore structure and contributes to lower porosity, and thus the chloride permeability of SCC is decreased during the late hydration stage. Additionally, a new factor of calculated water-binder ratio is put forward, which can directly reflect the free water content of concrete mixture after mixing, and guide the mix proportion design of SCC.

Impacts of Space Restriction on the Microstructure of Calcium Silicate Hydrate.

The effect of hydration space on cement hydration is essential. After a few days, space restriction affects the hydration kinetics which dominate the expansion, shrinkage and creep of cement materials. The influence of space restriction on the hydration products of tricalcium silicate was studied in this paper. The microstructure, morphology and composition of calcium silicate hydrate (C-S-H) were explored from the perspective of a specific single micropore. A combination of Raman spectra, Fourier transform infrared spectra, scanning electron microscopy and energy dispersive X-ray spectroscopy were employed. The results show that space restriction affects the structure of the hydration products. The C-S-H formed in the micropores was mainly composed of Q3 silicate tetrahedra with a high degree of polymerization. The C-S-H formed under standard conditions with a water to cement ratio of 0.5 mostly existed as Q2 units. Space restriction during hydration is conducive to the formation of C-S-H with silica tetrahedra of a high polymerization degree, while the amount of water filling the micropore plays no obvious role on the polymeric structure of C-S-H during hydration.

Steel Corrosion Behavior of Reinforced Calcium Aluminate Cement-Mineral Additions Modified Mortar.

Mineral additions can eliminate the conversion in calcium aluminate hydrates and thus inhibit the future strength retraction of calcium aluminate cement (CAC). However, the impacts of these additions on the protection capacity of CAC concrete in relation to the corrosion of embedded steel reinforcement remains unclear. This paper focused on the corrosion behavior of steel reinforcement in slag, limestone powder, or calcium nitrate-modified CAC mortars via XRD and electrochemical methods (corrosion potential, electrochemical impedance, and linear polarization evaluation). The results indicate that strätlingite (C2ASH8), which is formed in slag-modified CAC, has poor chloride-binding ability, leading to decline in corrosion resistance of the steel reinforcement. The electrochemical parameters of specimens immersed in NaCl solution suddenly drop at 14 days, which is 28 days earlier than that of the references. In contrast, the Ca2[Al(OH)6]20.5CO3OH·H2O (CaAl·CO32--LDH) and 3CaO·Al2O3·Ca(NO3)2·12H2O (NO3-AFm) in limestone powder and calcium nitrate-modified CAC mortar show great chloride-binding ability, thereby improving the corrosion resistance of the steel reinforcement. The electrochemical parameters of specimens modified with calcium nitrate maintain a slow decreasing trend within 90 days.

Properties of Calcium Sulfoaluminate Cement Mortar Modified by Hydroxyethyl Methyl Celluloses with Different Degrees of Substitution.

This paper studies the influence of hydroxyethyl methyl cellulose (HEMC) on the properties of calcium sulfoaluminate (CSA) cement mortar. In order to explore the applicability of different HEMCs in CSA cement mortars, HEMCs with higher and lower molar substitution (MS)/degree of substitution (DS) and polyacrylamide (PAAm) modification were used. At the same time, two kinds of CSA cements with different contents of ye'elimite were selected. Properties of cement mortar in fresh and hardened states were investigated, including the fluidity, consistency and water-retention rate of fresh mortar and the compressive strength, flexural strength, tensile bond strength and dry shrinkage rate of hardened mortar. The porosity and pore size distribution were also analyzed by mercury intrusion porosimetry (MIP). Results show that HEMCs improve the fresh state properties and tensile bond strength of both types of CSA cement mortars. However, the compressive strength of CSA cement mortars is greatly decreased by the addition of HEMCs, and the flexural strength is decreased slightly. The MIP measurement shows that HEMCs increase the amount of micron-level pores and the porosity. The HEMCs with different MS/DS have different effects on the improvement of tensile bond strength in different CSA cement mortars. PAAm modification can improve the tensile bond strength of HEMC-modified CSA cement mortar.

Oxidative stress response and proteomic analysis reveal the mechanisms of toxicity of imidazolium-based ionic liquids against Arabidopsis thaliana.

Ionic liquids (ILs) are extensively used in various fields, posing a potential threat in the ecosystem because of their high stability, excellent solubility, and biological toxicity. In this study, the toxicity mechanism of three ILs, 1-octyl-3-methylimidazolium chloride ([C8MIM]Cl), 1-decyl-3-methylimidazolium chloride ([C10MIM]Cl), and 1-dodecyl-3-methylimidazolium chloride ([C12MIM]Cl) on Arabidopsis thaliana were revealed. Reactive oxygen species (ROS) level increased with higher concentration and longer carbon chain length of ILs, which led to the increase of malondialdehyde (MDA) content and antioxidase activity, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and peroxidase (POD) activities. SOD, CAT, and GPX activities decreased in high ILs concentration due to the excessive ROS. Differentially expressed protein was analyzed based on Gene ontology (GO) and KEGG pathways analysis. 70, 45, 84 up-regulated proteins, and 72, 104, 79 down-regulated proteins were identified in [C8MIM]Cl, [C10MIM]Cl, and [C12MIM]Cl treatment, respectively (fold change ≥ 1.5 with ≥95% confidence). Cellular aldehyde metabolic process, mitochondrial and mitochondrial respiratory chains, glutathione transferase and oxidoreductase activity were enriched as up-regulated proteins as the defense mechanism of A. thaliana to resist external stresses. Chloroplast, photosynthetic membrane and thylakoid, structural constituent of ribosome, and transmembrane transport were enriched as the down-regulated protein. Compared with the control, 8 and 14 KEGG pathways were identified forup-regulated and down-regulated proteins, respectively, in three IL treatments. Metabolic pathways, carbon metabolism, biosynthesis of amino acids, porphyrin and chlorophyll metabolism were significantly down-regulated. The GO terms annotation demonstrated the oxidative stress response and effects on photosynthesis of A. thaliana in ILs treatment from biological process, cellular component, and molecular function categories.

Effects of ketoprofen on rice seedlings: Insights from photosynthesis, antioxidative stress, gene expression patterns, and integrated biomarker response analysis.

Pharmacologically active compounds found in reclaimed wastewater irrigation or animal manure fertilizers pose potential risks for agriculture. The mechanism underlying the effects of ketoprofen on rice (Oryza sativa L.) seedlings was investigated. The results showed that low concentrations (0.5 mg L-1) of ketoprofen slightly stimulate growth of rice seedlings, while high concentrations can significantly inhibit growth by reducing biomass and causing damage to roots. Ketoprofen affects photosynthetic pigment content (Chla, Chlb, and carotenoids) and chlorophyll synthesis gene (HEMA, HEMG, CHLD, CHLG, CHLM, and CAO) expression. Fluorescence parameters such as minimum fluorescence (F0), maximum fluorescence (Fm), variable fluorescence (Fv), potential photosynthetic capacity (Fv/F0), maximum quantum efficiency of PSII photochemistry (Fv/Fm), electron transfer rate (ETR), and Y(II), Y(NPQ), Y(NO) values were affected, showing photosynthetic electron transfer was blocked. Active oxygen radical (O2•-and H2O2), malondialdehyde and proline content increased. Superoxide dismutase, catalase and ascorbate peroxidase activities, glutathione content and antioxidant-related gene (FSD1, MSD1, CSD1, CSD2, CAT1, CAT2, CAT3, APX1, APX2) expression were induced. Higher integrated biomarker response values of eight oxidative stress response indexes were obtained at higher ketoprofen concentrations. Ultrastructure observation showed that ketoprofen causes cell structure damage, chloroplast swelling, increase in starch granules, and reduction in organelles. This study provides some suggested toxicological mechanisms and biological response indicators in rice due to stress from pharmacologically active compounds.

Supported ITZ Modification Efficiencies via Surface Coating Nanoparticles on Aggregate and its Influence on Properties.

In order to modify the porous interfacial transition zone (ITZ) microstructure of concrete more efficiently, a method of coating aggregate surfaces by using several nanoparticles was evaluated in this study. The compressive strength, chloride penetration of sound, and pre-loading samples were assessed in relation to the type of coating materials used (slag, nano-CaCO3, and nano-SiO2) and the designed coating thickness (5, 10, and 15 µm). The ITZ microstructure was quantitatively determined via Backscattered electron (BSE) image analysis. Results showed that the overall performance of concrete is highly dependent on the coating materials and the designed coating thickness. Increasing the coating thickness of slag and nano-SiO2 could improve the chloride penetration resistance but decrease the compressive strength. Using nano-CaCO3 to coat the aggregate leads to a significant reduction in the properties of the so-prepared concrete. Though coating inert fine particles around aggregate could disturb the initial particle packing and modify the ITZ, it is not able to improve the overall concrete properties. Coating aggregate could determine the ITZ microstructure, especially within the region that is around 30 µm away from aggregate surface.