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Reducing chemical fertilizers and biochar amendment is essential for achieving carbon neutrality, addressing global warming, and promoting sustainable agricultural development. Biochar amendment, a carbon rich soil additive produced through biomass pyrolysis, enhances soil fertility, increases crop yield, and improves soil carbon storage. However, research on the combined effect of fertilizer reduction and biochar amendment on soil mineral associated organic carbon (MAOC) in jasmine gardens is limited. This study aims to determine if biochar can reduce industrial fertilizer usage without compromising soil quality. This study focuses on jasmine cultivation in southeastern China, employing four treatments: conventional fertilization (CK), biochar amendment without fertilizer (BA), fertilizer reduction (FR), and fertilizer reduction with biochar amendment (FRBA). The effects on MAOC, microbial abundance, and enzyme activity were investigated. The FRBA treatment significantly increased MAOC content by 19.98 % compared to CK (P < 0.05). The BA and FRBA treatments enhanced the diversity of soil bacteria, including Lactobacillus, Azospirillum, and Cutibacterium, which are associated with soil organic carbon sequestration and nutrient decomposition. The RandomForest model identified ß-N-acetyl-glucosaminidase (NAG), electric conductivity (EC), ß-1, 4-Glucosidase (BG), soil potential of Hydrogen (pH), soil bulk density (BD), and ß-D-cellobiosidase (CBH) as key soil traits promoting MAOC accumulation (P < 0.05). The results indicate that BA and FRBA improve soil bacterial community structure, enzyme activity, and MAOC content, promoting soil carbon accumulation through environmental factors and dominant bacteria. This study encourages future fertilization protocols that enhance fertilizer efficiency and carbon storage in crop soils.

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BACKGROUND: Biochar is a relatively new development in sustainable agricultural management that can be applied to ameliorate degraded and less fertile soils, especially sandy-textured ones, to improve their productivity with respect to crop production through improved nutrient availability. However, as the literature has shown, the response of sandy-textured soils to biochar varies in terms of effect size and direction. Therefore, the present study systematically reviewed the available evidence to synthesize the impact of biochar amendments on aspects of the nutrient cycle of sandy-textured soils. METHODS: Both peer-reviewed and gray literature were searched in English in bibliographic databases, organizational web pages, and Internet search engines. Articles underwent a two-stage screening (title and abstract, and full-text) based on predefined criteria, with consistency checks. Validity assessments were conducted, utilizing specifically designed tools for study validity. Data extraction involved categorizing the various properties of the nutrient cycle into nine main Soil and Plant Properties (SPPs), each of which was studied independently. Nine meta-analyses were performed using a total of 1609 observations derived from 92 articles. Comparing meta-averages with and without correction for publication bias suggests that publication bias plays a minor role in the literature, while some indication for publication bias is found when accounting for heterogeneity by means of meta-regressions. REVIEW FINDINGS: According to the results, soil total and available nitrogen [N], phosphorous [P] and potassium [K], plant nutrient level, and potential cation exchange capacity (CEC) increased by 36% (CI [23%, 50%]), 34% (CI [15%, 57%]), 15% (CI [1%, 31%]), and 18% (CI [3%, 36%), respectively, and N2O emission and mineral nutrient leaching decreased by 29% (CI [- 48%, - 3%]) and 38% (CI [- 56%, - 13%). On average, however, biochar had no effect on soil mineral nitrogen and nutrient use efficiency. Publication bias was identified in the response of effective CEC. After corrections for publication bias, the response shifted from 36% to a negative value of - 34% (CI [- 50%, - 14%]). Meta-regression found that the effect modifiers experimental continent, biochar application rate, and soil pH, explain result heterogeneity. Stronger responses came from the continent of South America, higher application rates, and higher pH soils. Overall, biochar is found useful for many SPPs of nutrient cycling of sandy-textured soils, thereby contributing to increased crop yields in such soils.

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Understanding polychlorinated biphenyl (PCB) degradation in sequential anaerobic-aerobic remediation is crucial for effective remediation strategies. In this study, microcosm and greenhouse experiments were conducted to dissect the effects of organic amendments (carbon-based) and plant treatments (ryegrass) on soil PCB dissipation under oxic and sequential anoxic-oxic conditions. We analyzed the soil bacterial community in greenhouse experiments using high-throughput sequencing to explore plant-pollutant-microbe interactions. Microcosm results showed that organic amendments alone did not facilitate aerobic PCB removal, but significantly accelerated PCB dechlorination under anoxic conditions altering the profiles of PCB congeners. In standard greenhouses, plant treatments substantially increased PCB dissipation to 50.8 ± 3.9%, while organic amendments aided phytoremediation by promoting plant growth, increasing PCB removal to 65.9 ± 3.2%. In sequential anaerobic-aerobic greenhouses, plant growth was inhibited by flooding treatment while flooding stress was markedly alleviated by organic amendments. Plant treatments alone during sequential treatments did not lead to PCB dissipation; however, dissipation was significantly promoted following organic amendments, achieving a removal of 41.2 ± 5.7%. This PCB removal was primarily due to anaerobic dechlorination during flooding (27.8 ± 0.5% removal), rather than from plant growth stimulation in subsequent planting phase. Co-occurrence network and functional prediction analyses revealed that organic amendments recruited specific bacterial clusters with distinct functions under different conditions, especially stimulating plant-microbe interactions and xenobiotics biodegradation pathways in planted systems. The findings provide valuable guidance for the design of practical remediation strategies under various remedy scenarios, such as in arable or paddy fields.

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The effectiveness of phytoremediation in Cd-contaminated soils is crucial for enhancing nutrient availability and plant tolerance to Cd. We simulated soil contamination with varying textures and fertilization conditions. Two experiments were conducted: one without liming and fertilization and another with soil fertilization for grasses. The soil types used were Oxisol and Entisol, and the grasses tested were Megathyrsus maximus and Urochloa brizantha at three Cd levels: 0 mg kg-1 (Control), 2 mg kg-1 (Low), and 12 mg kg-1 (High). Soil amendments and fertilization did not significantly change Cd availability. Soil chemical attributes were unaffected by Cd contamination but were influenced by fertilization, which kept the pH below optimal levels. Cd availability was higher in more contaminated soils, with Entisol showing greater concentrations than Oxisol. Dry matter production of the grasses decreased with higher contamination, with U. brizantha being more productive than M. maximus in fertilized soils. Cd accumulation was higher in highly contaminated soils, particularly for U. brizantha. The bioconcentration factor was higher in Entisol, while the translocation factor exceeded 1.0 only for M. maximus in low-contamination Oxisol. Fertilization can mitigate Cd contamination effects, with U. brizantha showing greater tolerance and accumulation capacity in fertilized soils.

Grasses, often seen just as cover crops or forages, can play a vital role in mitigating heavy metal pollution, especially Cd. By comparing the growth, Cd accumulation, and tolerance of different grass species in fertilized versus unfertilized soils, we identify optimal strategies to maximize the effectiveness of phytoremediation without compromising soil health and ecological balance. The findings of the study reveal that the response of grasses to fertilization in contaminated soils varies significantly, directly influencing their capacity to phytoremediate Cd. This discovery suggests that customizing fertilizer use, based on the grass species and specific soil conditions, could be crucial for optimizing the removal of Cd from the environment.

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Long-term excessive use of fertilizers and intensive cultivation not only decreases soil organic carbon (SOC) and productivity, but also increases greenhouse gas emissions, which is detrimental to sustainable agricultural development. The purpose of this paper is to identify organic amendments suitable for winter wheat growth in the North China Plain by studying the effects of organic amendments on the economic benefits, carbon emissions, and carbon sequestration for winter wheat fields and to provide a theoretical basis for the wide application of organic amendments in agricultural fields. The two nitrogen rates were N0 (0 kg ha-1) and N240 (240 kg ha-1), and the four organic amendments were straw, manure, mushroom residue (M R), and biochar. The results showed that, compared to N0, N240 significantly increased the yield by 244.1-318.4% and the organic carbon storage by 16.7-30.5%, respectively, but increased the carbon emissions by 29.3-45.5%. In addition, soil carbon stocks increased with all three types of organic amendments compared to the straw amendment, with the biochar treatment being the largest, increasing carbon storage by 13.3-33.6%. In terms of yield and economic benefits, compared to the straw amendment, the manure and biochar amendments increased winter wheat yields by 0.0-1.5% and 4.0-13.3%, respectively, and M R slightly decreased wheat yield; only the economic benefit of the M R amendment was greater than that of the straw amendment, with an increase in economic benefit of 1.3% and 8.2% in the 2021-2022 and 2022-2023 seasons, respectively. Furthermore, according to the net ecosystem productivity (NEP), N0 was the source of CO2, while N240 was a sink of CO2. The TOPSIS results showed that N240 with a mushroom residue amendment could be recommended for increasing soil carbon stocks and economic benefits for winter wheat in the NCP and similar regions. Low-cost M R can increase farmer motivation and improve soil organic carbon, making a big step forward in the spread of organic materials on farmland.

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The compost effects on soil organic matter (SOM) stability were evaluated. Manure at 10 % ratio and compost at 10 %, 20 % and 40 % ratios (v/v) were added to the soil and their effects were compared to unamended control soil after 90-days of greenhouse-experiment. Humic acids (HA) and fulvic acids (FA) were extracted from two different soil-sample layers at 0-15 and 15-30 cm depth. The CHA/CFA ratio and the humification parameters were determined, and the soil-HA were characterized by spectroscopic methods (E4/E6 and FTIR). The humification parameters progress with time were affected by the amendment concentration. After 90 days, the treated soils HA' FTIR spectra showed an increase in aromatic carbon polycondensation and O-containing groups reflecting the high degrees of molecular associations and humification of soil HA. Compared to 10 % manure application and 40 % compost ratio use, the applications of 10 % and 20 % compost ratios induced higher humification level and highly oxidized HA structure. Moreover, changes in the HA compositional and functional groups were noticed at the upper layer which exhibited higher reactivity compared to the lower layer which displayed more humified SOM. Through the humification process, the HA fraction was improved to reach more stable and complex macromolecules, where aromatic structures were bio-converted into highly functionalized compounds.

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Microalgae can be collected in large quantities and hold significant potential for environmental remediation, offering a cost-effective solution. This study explores the use of Spirulina platensis (SP) as feedstock for biochar production. SP contains abundant nitrogen-rich components, such as proteins, which can serve as nitrogen sources. We prepared SP-derived biochar through pyrolysis for the adsorption of Pb and Zn from aqueous solutions and used it as an amending agent to remediate heavy metal-contaminated agricultural soil. Pyrolysis of proteins in SP introduces nitrogen-functional groups, resulting in nitrogen-doped biochar. We investigated the surface chemical behavior of thermally treated SP using X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Surface analysis revealed the presence of pyridine-N and pyrrole-N from protein pyrolysis products. The study also demonstrated that these functional groups affect interactions with heavy metals. Batch experiments examined the effects of pH and initial concentration on the adsorption of Pb and Zn using SP400 and SP600. Both types of biochar showed satisfactory performance in adsorbing Pb and Zn. The effect of SP400 and SP600 on the removal of Pb and Zn through the physicochemical properties and surface functional groups was investigated. Analysis of SP400 and SP600 highlighted that electrostatic interactions, cation exchange, complexation, and mineral precipitation contributed to Pb and Zn adsorption. The study concludes that SP-derived biochar, particularly SP600, is effective for immobilizing Pb and Zn in contaminated agricultural soil, with SP600 showing superior performance.

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Straw incorporation, a common agricultural strategy designed to enhance soil organic carbon (SOC), often leads to increased nitrous oxide (N2O) emission, potentially offsetting benefits of SOC sequestration. However, the mechanism and mitigation options for the enhanced N2O emission following straw incorporation remain unclear. Here, N2 and N2O emission rate, as well as N2O/(N2O + N2) ratio under four different fertilization treatments [i.e., non-fertilization (Control), conventional chemical fertilization (CF), conventional chemical fertilization plus straw incorporation (SWCF), and conventional chemical fertilization plus straw and biochar incorporation (SWBCF)] were investigated by a robotized sampling and analysis system. High-throughput sequencing was also employed to assess the variation of bacterial community across different treatments. The results showed CF, SWCF, and SWBCF fertilization treatments significantly increased N2O emission rate by 1.04, 2.01, and 1.29 folds, respectively, relative to Control treatment. Albeit no significant enhancements in N2 emission rate, the N2O/(N2O + N2) ratio significantly increased by 65.53%, 1.10 folds, and 69.49% in CF, SWCF, and SWBCF treatments, respectively. The partial least squares path modeling analysis further revealed that fertilization treatments slightly increased N2 emission rate by increasing DOC content and keystone OTUs abundance. While the enhanced N2O emission rate and N2O/(N2O + N2) ratio in the fertilization treatments was primarily determined by reducing DOC/NO3- ratio and specific bacteria module abundance dominated by Gaiellales, Solirubrobacterales, and Micrococcales. Furthermore, SWBCF treatment alleviated the increase in net global warming potential due to straw incorporation, as indicated by the higher SOC sequestration and lower N2O/(N2O + N2) ratio therein. Collectively, these findings suggest that simultaneous application of straw and biochar has the potential to mitigate the risk of increased N2O emission from straw incorporation. This study provides valuable insights for developing targeted strategies in C sequestration and greenhouse gas mitigation, tackling the challenge presented by global climate change.

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High-ash coal slime-based silica fertilizer (CSF) has the potential to provide mineral nutrients and passivate lead (Pb) in the soil to ensure the sustainable development of the coal industry and agriculture. This study investigated the performance and passivation mechanism of CSF, which contains potassium tobermorite and potassium silicate as the main components for soil improvement. Leaching experiments showed that low-crystalline muscovite was the only crystalline phase for CSF etching and that the silicon (Si), calcium (Ca), and potassium (K) in CSF had significant citric solubility. Soil cultivation and planting trials confirmed the ability of CSF to neutralize soil acidity, increase available soil Si and K, improve exchangeable Ca content, reduce the bioefficacy of Pb (exchangeable Pb by 19-75 % and carbonate-bound Pb by 6-18 %), and increase residual state Pb content. Compared to untreated Pb-contaminated soil, the 0.4 % CSF treatment reduced Pb in Chinese cabbage (Brassica rapa) by 25 % and increased plant biomass, Ca, and K by 37 %, 36 %, and 4 %, respectively. At the same time, soil pH increased by 0.58, and residual state Pb increased by 5 %. In CSF-treated soils, lead silicate is the dominant form of Pb present in the residual state. First-principle calculations showed that Pb3Si2O7 (cohesion energy -1.98 eV) formed by the passivation of Pb by CSF had greater stability in the soil compared to lead carbonate (PbCO3) (cohesion energy -1.38 eV) and lead sulfate (PbSO4) (cohesion energy -1.41 eV). This work shows the promising application of coal slime mineral fertilizers prepared using hydrothermal methods for soil improvement.

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Nitrogen (N) and carbon (C) inputs substantially affect soil microbial functions. However, the influences of long-term N and C additions on soil microbial resource limitation and heterotrophic respiration-fundamental microbial functional traits-remain unclear, impeding the understanding of how soil C dynamics respond to global change. In this study, the responses of soil microbial resource limitation and heterotrophic respiration (Rh) to 7-year N and biochar (BC) additions in a subtropical Moso bamboo (Phyllostachys edulis) plantation were investigated. We used eight treatments: Control, no N and BC addition; N30, 30 kg N (ammonium nitrate)·hm-2·a-1; N60, 60 kg N·hm-2·a-1; N90, 90 kg N·hm-2·a-1; BC20, 20 t BC (originating from Moso bamboo chips) hm-2; N30 + BC20, 30 kg N·hm-2·a-1 + 20 t BC hm-2; N60 + BC20, 60 kg N·hm-2·a-1 + 20 t BC hm-2; and N90 + BC20, 90 kg N·hm-2·a-1 + 20 t BC hm-2. Soil microbes were co-limited by N and phosphorus (P) and not limited by C in the control treatments. Long-term N addition enhanced soil microbial N and P limitation but significantly reduced soil Rh by 15.1 %-20.0 % relative to that in the control treatments. BC amendment alleviated soil microbial N and P limitation and significantly decreased C use efficiency by 10.9 %-42.1 % but increased Rh by 33.6 %-91.6 % in the long-term N-free and N-supplemented treatments (P < 0.05). Soil C- and N-acquisition enzyme activities were the dominant drivers of soil microbial resource limitation. Furthermore, microbial resource limitation was a more reliable predictor of Rh than soil resources or microbial biomass. The results suggested that long-term N and BC additions affect Rh by regulating microbial resource limitation, highlighting its significance in understanding soil C cycling under environmental change.

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Compost residue enriches soil health with the potential to enhance plant metabolism and hormonal balance, but has not yet been studied. A study was performed to determine how prevailing compost residue induces tomato (Solanum lycopersicum 'Scotia') plant morpho-physiology, phytohormones, and secondary metabolites. Plants were grown in soils with a previous history of annual (AN) and biennial (BI) compost amendments. The controls were soil without compost (C) amendment and municipal solid waste compost (MSWC) alone. The MSWC- and AN-plants had similar and significantly (p < 0.05) highest growth and photosynthetic activities compared to the BI- or C-plants. Total phenolics and lipid peroxidase activity were significantly (p < 0.001) high in BI-plants, while hydrogen peroxide and antioxidant capacity were significantly (p < 0.001) high in AN-plants. MSWC-plants recorded the highest cis-abscisic acid, followed by AN-, and then BI- and C-plants. Cis-zeatin, trans-zeatin, and isopentenyladenine ribosides were detected in the MSWC- and AN-plants but not in the BI- or C-plants. Furthermore, gibberellins GA53, GA19, and GA8 were high in the MSWC-plants, but only GA8 was detected in the AN plants and none in the others. Besides, MSWC plants exhibited the highest content of 1-aminocyclopropane-1-carboxylic acid. Conjugated salicylic acid was highest in the BI-plants, while jasmonic acid-isoleucine was highest in MSWC-plants and C plants. In conclusion, prevailing compost chemical residues upregulate plant growth, phytohormones, and metabolic compounds that can potentially increase plant growth and abiotic stress defense. Future work should investigate the flow of these compounds in plants under abiotic stress.

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Background: Zea mays (maize) is a globally significant cereal crop with diverse applications in food, feed, and industrial products. However, maize cultivation is often challenged by environmental stressors such as heavy metal toxicity and drought stress (DS). Heavy metals like cadmium (Cd) and lead (Pb) can accumulate in soil through industrial activities and improper waste disposal, posing significant threats to plant growth and development. Drought stress further exacerbates these challenges by limiting water availability and affecting physiological processes in plants. This study explores the impact of Cd and Pb toxicity, as well as DS, on maize growth and development, and investigates the potential mitigating effects of various treatments, including gibberellic acid (GA3), biochar (BC), rhizobacteria (RB), and their combinations. Methods: The experiment involved maize plants subjected to different stress conditions: cadmium (Cd) at concentrations of 0, 6, and 12 ppm, lead (Pb) at 0 and 400 ppm, and drought stress (DS). Treatments included the application of 10 ppm GA3, 0.75% BC, a combined treatment of 10 ppm GA3 and 0.75% BC, rhizobacteria (RB), and a combined treatment of 0.5% BC and RB. The study measured germination rates, shoot and root lengths, and biochemical parameters such as shoot and root protein, phenolics, and chlorophyll contents under these conditions. Results: In the absence of Cd stress (0 Cd), the application of 10 ppm GA3 and 0.75% BC significantly enhanced germination rates by 72% and 76%, respectively, compared to the control, with the combined treatment exhibiting the highest enhancement of 86%. Under Cd stress (6 ppm Cd), GA3 and BC individually improved germination by 54% and 57%, respectively, with the combined treatment showing the largest increase of 63%. Drought stress influenced germination, with notable improvements observed with the application of 0.5% BC (50% increase) and RB (49% increase). Similar trends were observed in shoot and root lengths, where the combined treatment of GA3 and BC resulted in the most significant improvements. The treatments positively influenced shoot and root protein, phenolics, and chlorophyll contents, particularly under stress conditions. Conclusion: These findings highlight the potential of combined treatments, such as the application of GA3 and BC or BC with RB, in alleviating the adverse effects of heavy metals (Cd and Pb) and drought stress in maize cultivation. The combined treatments not only improved germination rates but also significantly enhanced shoot and root growth, as well as important biochemical parameters under stress conditions. This suggests that GA3 and BC, alone or in combination with RB, can play a crucial role in enhancing maize resilience to environmental stressors. The study highlights the importance of exploring sustainable agricultural practices to mitigate the impacts of heavy metal toxicity and drought stress. Future research should focus on long-term field trials to validate these findings and further investigate the mechanistic pathways involved in stress mitigation by these amendments, as well as their economic feasibility and environmental impact on a larger scale to ensure their practical applicability in real-world agricultural settings.

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Due to the bioavailability and movement of antimony in trophic web, the overexploitation of antimony mine resulted in antimony contamination that harmed the ecology nearby, raising concerns for public health. Whereas, most researches focused on the removal of antimony in the aqueous instead of the immobilization of antimony in the soil. Herein, the immobilized performance of biochar (BC) loaded with nano zero-valent iron (nZVI-BC) on antimony in the soil near the smelting area was researched through pot experiments for the first time, and its stabilization mechanism on antimony was investigated by valent state variation of antimony. The results demonstrated that BC restricted the cation exchange capacity and catalase activity in the soil, while nZVI-BC had a favorable and negative impact on two variables, respectively. The nZVI-BC showed more stable immobilization capacity on antimony over time than BC, whose exchangeable speciation only marginally rose (2%-6%), although the exchangeable speciation of antimony fell both from 15% to 2% after adding the BC and nZVI-BC, The electron attraction force between nZVI-BC and antimony was also intensified owing to the oxidation-reduction process, which was considered as the stabilizing principle of nZVI-BC on antimony in soil. Furthermore, the decreased bioaccumulation factor for the perennial ryegrass (0.46-0.21) and Galinsoga parviflora Cav. (0.26-0.17) stated that the BC effectively mitigated the bioaccumulation risk of antimony.

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Pesticide contamination and soil degradation present significant challenges in agricultural ecosystems, driving extensive exploration of biochar (BC) and nano-biochar (NBC) as potential solutions. This study examines their effects on soil properties, microbial communities, and the fate of two key pesticides: the hydrophilic methomyl (MET) and the hydrophobic lambda-cyhalothrin (LCT), at different concentrations (1%, 3%, and 5% w w-1) in agricultural soil. Through a carefully designed seven-week black bean pot experiment, the results indicated that the addition of BC/NBC significantly influenced soil dynamics. Soil pH and moisture content (MC) notably increased, accompanied by a general rise in soil organic carbon (SOC) content. However, in BC5/NBC5 treatments, SOC declined after the 2nd or 3rd week. Microbial populations, including total plate count (TPC), phosphate-solubilizing bacteria (PSB), and nitrogen-fixing bacteria (NFB), showed dynamic responses to BC/NBC applications. BC1/NBC1 and BC3/NBC3 applications led to a significant increase in microbial populations, whereas BC5/NBC5 treatments experienced a decline after the initial surge. Furthermore, the removal efficiency of both MET and LCT increased with higher BC/NBC concentrations, with NBC demonstrating greater efficacy than BC. Degradation kinetics, modeled by a first-order equation, revealed that MET degraded faster than LCT. These findings underscore the profound impact of BC/NBC on pesticide dynamics and microbial communities, highlighting their potential to transform sustainable agricultural practices.

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Applying biochar has beneficial effects on regulating plant growth by providing water and nutrient availability for plants due to its physicochemical characteristics. Nevertheless, it is still unclear how soil and biochar interactions strengthen crop lodging resistance. The objective of the current study was to find out how soil physicochemical conditions and alterations in biochar affect lodging resistance and crop productivity in cereals. To do this, a meta-analysis was carried out using nine groups of effective variables including type of feedstock, pyrolysis temperature, application rate, soil pH, total nitrogen, available phosphorus, potassium, organic matter (OM), and soil texture. Results showed that straw-derived biochar caused the highest positive effect size in the dry weight of biomass (20.5%) and grain yield (19.9%). Also, the lowest lodging index was observed from straw (-8.3%) and wood-based (-5.6%) biochars. Besides, the high application rate of biochar results in the highest positive effect sizes of plant cellulose (8.1%) and lignin content (7.6%). Soils that contain >20 g kg-1 OM, resulted in the highest positive effect size in dry biomass (27.9%), grain yield (30.2%), and plant height (4.7%). Also, fine-textured soil plays an important role in increasing polymers in the anatomical structure of plants. Overall, the strong connection between biochar and soil processes, particularly the availability of OM, could strengthen plants' ability to tolerate lodging stress and contribute to high nutrient efficiency in terms of crop output and cell wall thickening.

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This study explores the potential of synergistically reducing direct (refrigerant) and indirect (electricity) greenhouse gas (GHG) emissions in the global room air conditioning (RAC) sector, based on 80% of global RAC manufactured in China. Three scenarios are evaluated: Business-as-usual (BAU) based on maintaining refrigerant and energy efficiency levels from 2021 China RAC sales shares, Kigali Amendment compliant with 10% energy efficiency improvement by 2025 (KAE), and accelerated refrigerant transition and energy efficiency improvement (ATE). Each scenario considers the costs of refrigerant and efficiency measures for export market groups based on Kigali Amendment classifications. BAU predicts around 1 Gt CO2-eq average annual global RAC emissions (2022-2060). Cumulative emission reductions in China's RAC manufacturing under KAE and ATE are 12.2 and 17.2 Gt CO2-eq A5II and A5I (except China), presenting cost-effective abatement measures, with average costs of -$51.4 and -$68.8/t CO2-eq in KAE and ATE. Cumulative average abatement costs are around $18 and $4/t CO2-eq globally. KAE and ATE scenarios would avoid surface temperature rises of 0.023 (±0.002) °C and 0.027 (±0.003) °C, respectively, versus BAU. Collaboration between China and importing countries is urged to enhance energy efficiency in RACs traded, ensuring sustainable mitigation aligned with the Kigali Amendment.

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Hydrogel adsorbents are promising tools for reducing heavy metals' bioavailability in contaminated soil. However, their practical feasibility remains limited by the low stability, inefficient removal efficiency, and potential secondary pollution. Optimizing the adsorption operation and the functional properties of hydrogel adsorbents could eliminate this method's drawbacks. Herein, three innovative in-situ remediation strategies for Pb/Cu-contaminated soil were adopted based on the concept of novel TEMPO-cellulose (TO-NFCs)/lignin/acrylamide@MIL-100(Fe) nanocomposite hydrogel adsorbent (NCLMH). Characteristic analyses revealed ideal Pb/Cu adsorption mechanisms by swelling, complexation, electrical attraction, and ion exchange via carboxyl/hydroxyl/carbonyl groups and unsaturated Fe(III) sites on ANCMH besides FeOOH formation. The highest maximum theoretical adsorption capacities of Pb(II) and Cu(II) on ANCMH were 416.39 and 133.98 mg/g, under pH 6.5, governed by pseudo-second-order/Freundlich models. Greenhouse pot experiments with contaminated soils amended with two-depth layers of 0.5% NCLMHs (SA@NCLMH) displayed a decline in Pb and Cu bioavailability up to 85.9% and 74.5% within 45 d. Soil column studies simulating continuous water soil flushing coupled with NCLMH layers, instead of conventional extractant fluids, and connected to NCLMH-sand column as purification unit (CF@NCLMH) achieved higher removal rates for Pb, and Cu of 89.5% and 77.2% within 24 h. Alternatively, conducting multiple-pulse soil flushing mode (MF@NCLMH) gained the highest Pb and Cu removal of 96.5% and 85.4%, as the water flushing-stop flux events allowed adequate water movement/residence period, promoting Pb/Cu desorption-adsorption from soil to NCLMH. Also, the NCLMH-sand column conducting and easy separation of the stable/reusable NCLMHs prevented the potential secondary pollution. Interestingly, the three remediated soils reached the corresponding regulation of the permissible limits for Pb and Cu residential scenarios in medium-to-heavily agricultural polluted soils, alleviating the Pb/Cu bioaccumulation and phytotoxicity symptoms in cultivated wheat, especially after MF@NCLMH treatment. This study introduces promising alternative remediation strategies with high sustainability and feasibility in acidic-to-neutral heavy metal-contaminated agricultural soil.

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The effects of changes in environmental temperatures on the immobilization or removal of cationic potentially toxic elements (PTE) in heavily polluted soils are often poorly understood, although both are widely studied in the context of phytostabilization. To address this issue, a novel compost-diatomite hybrid (CDH) amendment was developed and applied for assisted phytostabilization at two external temperature regimes. (Cd/Ni/Cu/Zn)-extremely polluted soils (unenriched and CDH-enriched) were cultivated with perennial ryegrass and native soil microbiome under greenhouse conditions and then transferred to freeze-thaw conditions (FTC). The decrease in metal potential toxicity in soils subjected to phytostabilization following both temperature treatments was characterized by a combination of sequential extraction and atomic absorption measurements. The soil microbiome was characterized by high-throughput sequencing. In a relative comparison, the greatest decrease in the content of all PTEs in CDH-enriched soil (compared to unenriched soil) appeared in FTC. Furthermore, under the influence of FTC, in the relative comparison between two CDH-enriched soils (exposed-, and not-exposed- to FTC) and two unenriched soils (exposed-, and not-exposed- to FTC), the content of all PTEs decreased more sharply in the CDH-enriched series than in the unenriched series. The largest redistribution into four sequentially extracted fractions in CDH-enriched soil was found for Zn. Based on the distribution pattern, Zn immobilization was greater in CDH-enriched soil in FTC. CDH increased species richness in the soil, while FTC stimulated the growth of Bacteroidia, Alphaproteobacteria, Theromomicrobia, and Gammaproteobacteria. The analysis of the functionalities of the microbiome indicated enhanced metal transportation and defense systems in samples exposed to FTC. The current research is crucial for understanding how extreme environmental conditions in both cases high pollutant levels and low temperatures affect the movement and transformation of PTEs in polluted soils during phytostabilization.

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Rise in climate change-induced drought occurrences have amplified pollution of metal(loid)s, deteriorated soil quality, and deterred growth of crops. Rice straw-derived biochars (RSB) and cow manure-enriched biochars (CEB) were used in the investigation (at doses of 0%, 2.5%, 5%, and 7.5%) to ameliorate the negative impacts of drought, improve soil fertility, minimize arsenic pollution, replace agro-chemical application, and maximize crop yields. Even in soils exposed to severe droughts, 3 months of RSB and CEB amendment (at 7.5% dose) revealed decreased bulk density (13.7% and 8.9%), and increased cation exchange capacity (6.0% and 6.3%), anion exchange capacity (56.3% and 28.0%), porosity (12.3% and 7.9%), water holding capacity (37.5% and 12.5%), soil respiration (17.8% and 21.8%), and nutrient contents (especially N and P). Additionally, RSB and CEB decreased mobile (30.3% and 35.7%), bio-available (54.7% and 45.3%), and leachable (55.0% and 56.5%) fractions of arsenic. Further, pot experiments with Bengal gram and coriander plants showed enhanced growth (62-188% biomass and 90-277% length) and reduced arsenic accumulation (49-54%) in above ground parts of the plants. Therefore, biochar application was found to improve physico-chemical properties of soil, minimize arsenic contamination, and augment crop growth even in drought-stressed soils. The investigation suggests utilisation of cow manure for eco-friendly fabrication of nutrient-rich CEB, which could eventually promote sustainable agriculture and circular economy. With the increasing need for sustainable agricultural practices, the use of biochar could provide a long-term solution to enhance soil quality, mitigate the effects of climate change, and ensure food security for future generations. Future research should focus on optimizing biochar application across various soil types and climatic conditions, as well as assessing its long-term effectiveness.

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Hydroxyl radicals (•OH) play a significant role in contaminant transformation and element cycling during redox fluctuations in paddy soil. However, these important processes might be affected by widely used agricultural amendments, such as urea, pig manure, and biochar, which have rarely been explored, especially regarding their impact on soil aggregates and associated biogeochemical processes. Herein, based on five years of fertilization experiments in the field, we found that agricultural amendments, especially coapplication of fertilizers and biochar, significantly increased soil organic carbon contents and the abundances of iron (Fe)-reducing bacteria. They also substantially altered the fraction of soil aggregates, which consequently enhanced the electron-donating capacity and the formation of active Fe(II) species (i.e., 0.5 M HCl-Fe(II)) in soil aggregates (0-2 mm), especially in small aggregates (0-3 µm). The highest contents of active Fe(II) species in small aggregates were mainly responsible for the highest •OH production (increased by 1.7-2.4-fold) and naphthalene attenuation in paddy soil with coapplication of fertilizers and biochar. Overall, this study offers new insights into the effects of agricultural amendments on regulating •OH formation in paddy soil and proposes feasible strategies for soil remediation in agricultural fields, especially in soils with frequent occurrences of redox fluctuations.