Effects of extracellular polymeric substances of Pseudomonas fluorescens, citrate, and oxalate on Pb sorption by an acidic Ultisol

Microbial enhanced manganese-autotrophic denitrification in reactor: performance, microbial diversity, potential functions

Autotrophic denitrification technology has gained increasing attention in recent years owing to its effectiveness, economical, and environmentally friendly nature. However, the sluggish reaction rate has emerged as the primary impediment to its widespread application. Herein, a bio-enhanced autotrophic denitrification reactor with modified loofah sponge (LS) immobilized microorganisms was established to achieve efficient denitrification. Under autotrophic conditions, a nitrate removal efficiency of 59.55 % (0.642 mg/L/h) and a manganese removal efficiency of 86.48 % were achieved after bio-enhance, which increased by 20.92 % and 36.34 %. The bioreactor achieved optimal performance with denitrification and manganese removal efficiencies of 99.84 % (1.09 mg/L/h) and 91.88 %. ETSA and 3D-EEM analysis reveled manganese promoting electron transfer and metabolic activity of microorganisms. High-throughput sequencing results revealed as the increase of Mn(II) concentration, Cupriavidus became one of the dominant strains in the reactor. Prediction of metabolic functions results proved the great potential for Mn(II)-autotrophic denitrification of LS bioreactor.

Simultaneous removal of nitrate, manganese, zinc, and bisphenol a by manganese redox cycling system: Performance and mechanism

The manganese(Mn) redox cycling system in this work was created by combining Mn(IV)-reducing bacteria MFG10 with Mn(II)-oxidizing bacteria HY129. The biomanganese oxides (BMO) generated by strain HY129 were transformed by strain MFG10 to Mn(II), finishing the Mn redox cycling, in which nitrate (NO3--N) was converted to nitrite, which was further reduced to nitrogen gas. The system could achieve 85.7 % and 98.8 % elimination efficiencies of Mn(ⅠⅠ) and NO3--N, respectively, at Mn(ⅠⅠ) = 20.0 mg/L, C/N = 2.0, pH = 6.5, and NO3--N = 16.0 mg/L. The removal of bisphenol A (BPA) and zinc (Zn(II)) at 36 h reached 91.7 % and 89.7 % under the optimal condition, respectively. Furthermore, the Mn redox cycling system can reinforce the metabolic activity and electron transfer activity of microorganisms. The findings showed that the adsorption by bioprecipitation throughout the Mn cycling was responsible for the elimination of Zn(II) and BPA.

Differential immobilization of cadmium and changes in soil surface charge in acidic Ultisol by chitosan and citric acid: effect of their functional groups

Soil organic matter plays an important role in cadmium adsorption and immobilization. Since different organic matter components affect cadmium adsorption processes differently, selecting the right organic substrate and knowing how to apply it could improve cadmium remediation. This study compares the effects of two contrasting organic molecules; chitosan and citric acid, on cadmium adsorption and speciation in acidic Ultisol. The adsorption of chitosan to Ultisol significantly increased the soil positive charge while adsorption of citric acid increased the soil negative charge. At pH 5.0, the maximum amount of cadmium adsorbed in excess chitosan was 341% greater than that in excess citric acid. About 73-89% and 60-62% of adsorbed cadmium were bound to Fe/Mn oxides and organic matter/sulfide at pH 4.0 while this fraction was 77-100% and 57-58% for citric acid and chitosan at pH 5.0, respectively. This decrease in the complexing ability of chitosan was related to the destabilizing effect of high pH on chitosan's structure. Also, the sequence through which chitosan, citric acid, and cadmium were added into the adsorption system influenced the adsorption profile and this was different along a pH gradient. Specifically, adding chitosan and cadmium together increased adsorption compared to when chitosan was pre-adsorbed within pH 3.0-6.5. However, for citric acid, the addition sequence had no significant effect on cadmium adsorption between pH 3.0-4.0 compared to pH 6.5 and 7.5, with excess citric acid generally inhibiting adsorption. Given that the action of citric acid is short-lived in soil, chitosan could be a good soil amendment material for immobilizing cadmium.

Biochemical and multi-omics analyses of response mechanisms of rhizobacteria to long-term copper and salt stress: Effect on soil physicochemical properties and growth of Avicennia marina

Mangroves are of important economic and environmental value and research suggests that their carbon sequestration and climate change mitigation potential is significantly larger than other forests. However, increasing salinity and heavy metal pollution significantly affect mangrove ecosystem function and productivity. This study investigates the tolerance mechanisms of rhizobacteria in the rhizosphere of Avicennia marina under salinity and copper (Cu) stress during a 4-y stress period. The results exhibited significant differences in antioxidant levels, transcripts, and secondary metabolites. Under salt stress, the differentially expressed metabolites consisted of 30% organic acids, 26.78% nucleotides, 16.67% organic heterocyclic compounds, and 10% organic oxides as opposed to 27.27% organic acids, 24.24% nucleotides, 15.15% organic heterocyclic compounds, and 12.12% phenyl propane and polyketides under Cu stress. This resulted in differential regulation of metabolic pathways, with phenylpropanoid biosynthesis being unique to Cu stress and alanine/aspartate/glutamate metabolism and α-linolenic acid metabolism being unique to salt stress. The regulation of metabolic pathways enhanced antioxidant defenses, nutrient recycling, accumulation of osmoprotectants, stability of plasma membrane, and chelation of Cu, thereby improving the stress tolerance of rhizobacteria and A. marina. Even though the abundance and community structure of rhizobacteria were significantly changed, all the samples were dominated by Proteobacteria, Chloroflexi, Actinobacteriota, and Firmicutes. Since the response mechanisms were unbalanced between treatments, this led to differential growth trends for A. marina. Our study provides valuable inside on variations in diversity and composition of bacterial community structure from mangrove rhizosphere subjected to long-term salt and Cu stress. It also clarifies rhizobacterial adaptive mechanisms to these stresses and how they are important for mitigating abiotic stress and promoting plant growth. Therefore, this study can serve as a reference for future research aimed at developing long-term management practices for mangrove forests.

Antibiotics soil-solution chemistry: A review of environmental behavior and uptake and transformation by plants

The increased use of antibiotics by humans for various purposes has left the environment polluted. Antibiotic pollution remediation is challenging because antibiotics exist in trace amounts and only highly sensitive detection techniques could be used to quantify them. Nevertheless, their trace quantity is not a hindrance to their transfer along the food chain, causing sensitization and the development of antibiotic resistance. Despite an increase in the literature on antibiotic pollution and the development and transfer of antibiotic-resistant genes (ARGs), little attention has been given to the behavior of antibiotics at the soil-solution interface and how this affects antibiotic adsorption-desorption interactions and subsequent uptake and transformation by plants. Thus, this review critically examines the interactions and possible degradation mechanisms of antibiotics in soil and the link between antibiotic soil-solution chemistry and uptake by plants. Also, different factors influencing antibiotic mobility in soil and the transfer of ARGs from one organism to another were considered. The mechanistic and critical analyses revealed that: (a) the charge characteristics of antibiotics at the soil-root interface determine whether they are adsorbed to soil or taken up by plants; (b) antibiotics that avoid soil colloids and reach soil pore water can be absorbed by plant roots, but their translocation to the stem and leaves depends on the ionic state of the molecule; (c) few studies have explored how plants adapt to antibiotic pollution and the transformation of antibiotics in plants; and (d) the persistence of antibiotics in cropland soils can be influenced by the content of soil organic matter, coexisting ions, and fertilization practices. Future research should focus on the soil/solution-antibiotic-plant interactions to reveal detailed mechanisms of antibiotic transformation by plants and whether plant-transformed antibiotics could be of environmental risk.

Combined application of Pseudomonas fluorescens and urea can mitigate rapid acidification of cropland Ultisol

Rhizobacteria maintain a healthy soil required for crop growth. This has led to increased interest in the use of bacteria-based biofertilizers in agriculture as they improve soil nutrient content and protect plants against pathogens. However, the effect of bacteria inoculum on N transformation and soil physicochemical properties during urea fertilization remains unexploited. Thus, this study investigated the effect of Pseudomonas fluorescens on urea N transformation in an acidic Ultisol within a 70-d incubation period. The results revealed that (1) soil pH peaked on d 5 (pH 5.58) and 20 (pH 6.23) and rapidly decreased till d 62 (pH 4.10) and 50 (pH 4.93) for urea and urea + bacteria treatments, respectively, and remained constant thereafter. After 70 d, the pH of the bacteria-treated Ultisol remained higher (0.78 pH units) than that of urea-treated Ultisol; (2) the change in soil pH was in agreement with the mineralization trend of N, as the concentration of NH4+-N peaked on d 5 (134.2 mg N kg-1) and 20 (423 mg N kg-1) before decreasing to 62.1 and 276.1 mg N kg-1 on d 70 in urea-treated and bacteria-treated Ultisol, respectively; and (3) P. fluorescens consumed protons produced during nitrification to retard rapid decrease in soil pH, decreased soil exchangeable acidity (33.3 %), increased soil effective cation exchange capacity (32.8 %), and increased the solubility of soil exchangeable base cations (68.4 %, Ca2+ + Mg2+ + K+ + Na+). Thus, bacterial inoculum could promote N mineralization, enhance nutrient solubility, and retard soil acidification during N transformation in soils.

Recent perspective of antibiotics remediation: A review of the principles, mechanisms, and chemistry controlling remediation from aqueous media

Antibiotic pollution is an ever-growing concern that affects the growth of plants and the well-being of animals and humans. Research on antibiotics remediation from aqueous media has grown over the years and previous reviews have highlighted recent advances in antibiotics remediation technologies, perspectives on antibiotics ecotoxicity, and the development of antibiotic-resistant genes. Nevertheless, the relationship between antibiotics solution chemistry, remediation technology, and the interactions between antibiotics and adsorbents at the molecular level is still elusive. Thus, this review summarizes recent literature on antibiotics remediation from aqueous media and the adsorption perspective. The review discusses the principles, mechanisms, and solution chemistry of antibiotics and how they affect remediation and the type of adsorbents used for antibiotic adsorption processes. The literature analysis revealed that: (i) Although antibiotics extraction and detection techniques have evolved from single-substrate-oriented to multi-substrates-oriented detection technologies, antibiotics pollution remains a great danger to the environment due to its trace level; (ii) Some of the most effective antibiotic remediation technologies are still at the laboratory scale. Thus, upscaling these technologies to field level will require funding, which brings in more constraints and doubts patterning to whether the technology will achieve the same performance as in the laboratory; and (iii) Adsorption technologies remain the most affordable for antibiotic remediation. However, the recent trends show more focus on developing high-end adsorbents which are expensive and sometimes less efficient compared to existing adsorbents. Thus, more research needs to focus on developing cheaper and less complex adsorbents from readily available raw materials. This review will be beneficial to stakeholders, researchers, and public health professionals for the efficient management of antibiotics for a refined decision.

Recovery of Extracellular Polymeric Substances from Excess Sludge Using High-Flux Electrospun Nanofiber Membranes

The recycling of extracellular polymeric substances (EPSs) from excess sludge in wastewater treatment plants has received increasing attention in recent years. Although membrane separation has great potential for use in EPS concentration and recovery, conventional membranes tend to exhibit low water flux and high energy consumption. Herein, electrospun nanofiber membranes (ENMs) were fabricated using polyvinylidene fluoride (PVDF) and used for the recovery of EPSs extracted from the excess sludge using the cation exchange resin (CER) method. The fabricated ENM containing 14 wt.% PVDF showed excellent properties, with a high average water flux (376.8 L/(m2·h)) and an excellent EPS recovery rate (94.1%) in the dead-end filtration of a 1.0 g/L EPS solution at 20 kPa. The ENMs displayed excellent mechanical strength, antifouling properties, and high reusability after five recycles. The filtration pressure had a negligible effect on the average EPS recovery rate and water flux. The novel dead-end filtration with an EPS filter cake on the ENM surface was effective in removing heavy-metal ions, with the removal rates of Pb2+, Cu2+, and Cr6+ being 89.5%, 73.5%, and 74.6%, respectively. These results indicate the potential of nanofiber membranes for use in effective concentration and recycling of EPSs via membrane separation.

Efficient Mn(II) removal mechanism by Serratia marcescens QZB-1 at high manganese concentration

Manganese (Mn(II)) pollution has recently increased and requires efficient remediation. In this study, Serratia marcescens QZB-1, isolated from acidic red soil, exhibited high tolerance against Mn(II) (up to 364 mM). Strain QZB-1 removed a total of 98.4% of 18 mM Mn(II), with an adsorption rate of 71.4% and oxidation rate of 28.6% after incubation for 48 h. The strain synthesized more protein (PN) to absorb Mn(II) when stimulated with Mn(II). The pH value of the cultural medium continuously increased during the Mn(II) removal process. The product crystal composition (mainly MnO₂ and MnCO₃), Mn-O functional group, and element-level fluctuations confirmed Mn oxidation. Overall, strain QZB-1 efficiently removed high concentration of Mn(II) mainly via adsorption and showed great potential for manganese wastewater removal.

Phenol and 17β-estradiol removal by Zoogloea sp. MFQ7 and in-situ generated biogenic manganese oxides: Performance, kinetics and mechanism

The pollution of multifarious pollutants such as heavy metal, organic compounds, and nitrate are a hot research topic at present. In this study, the functions of Zoogloea sp. MFQ7 and its biological precipitation formed during bacterial manganese oxidation on the removal of phenol and 17β-estradiol (E2) were investigated. Strain MFQ7, a manganese-oxidizing bacteria, can remove 98.34% of phenol under pH of 7.1, a temperature of 30 ℃ and Mn²⁺ concentration of 24.34 mg L^-1, additionally, the optimum E2 removal by strain MFQ7 was 100.00% at pH of 7.1, temperature of 28 ℃ and Mn²⁺ concentration of 28.45 mg L^-1 by using response surface methodology (RSM) based on Box-Behnken design (BBD) model. The maximum adsorption capacity of bio-precipitation for phenol and E2 was 201.15 mg g^-1 and 65.90 mg g^-1, respectively. Furthermore, adsorption kinetics and isotherms analysis, XPS, FTIR spectra, Mn(III) trapping experiments elucidated chemical adsorption and Mn(III) oxidation contribute to the removal of phenol and E2 by biogenic manganese oxides. These findings indicated that the adsorption and oxidation of manganese are expected to be one of the effective means to remove these typical organic pollutants containing phenol and E2.

Recovery of polymeric substances from excess sludge: Surfactant-enhanced ultrasonic extraction and properties analysis

The recovery of polymeric substances from excess sludge is gaining significant research interest in future wastewater treatment technologies. We present a surfactant-enhanced ultrasonic method to extract mixed polymeric substances with typical functional groups from excess sludge. Four potential reasons were revealed for the higher efficiency upon ultrasonication with surfactant: low surface tension, damage of non-covalent bonds between extracellular polymeric substances and cells, enhanced dissolution of polymeric substances, and release of intracellular polymeric substances caused by cell lysis. The increase in extraction efficiency after the addition of cetyltrimethylammonium bromide and sodium dodecyl sulfate reached the maximum of 76.5% and 53.1%, respectively. The contents of polysaccharides, proteins, and DNA were approximately 50% of the total polymeric substances, and the content of protein was higher than that of polysaccharide; the concentration change of the surfactant had a minimal effect on these contents. For the polymeric substances extracted via ultrasonication with surfactant, the size was smaller than that for the non-surfactant extraction; moreover, the contents of metals decreased significantly (Al: 0.18% → 0%; Na: 0.15% → 0%; Ca: 0.24% → 0.11%), which was probably caused by the interaction between the surfactant and metal ions in the excess sludge. The surfactant had a negligible effect on the properties of polymeric substances, adsorption capacity of polymeric substances for heavy metal ions, and dewatering performance of sludge. The recycled polymeric substances may be used as a substitute for commercial adsorbents of heavy metal ions. Thus, the obtained results provide further insight into the recovery of polymeric substances from excess sludge via the surfactant-enhanced ultrasonic method.

Insight into biosorption of heavy metals by extracellular polymer substances and the improvement of the efficacy: a review

Heavy metals are continuously released into aquatic environments in which they accumulate. This phenomenon endangers public health because heavy metals accumulate along the food chain. However, conventional remediation methods are inefficient, expensive and yield toxic intermediate products, which adversely affect the environment. The discovery of green bio-adsorbents such as microbial extracellular polymer substance (EPS) has quickly attracted considerable worldwide attention because of their low cost, high removal efficiency of heavy metals and industrial availability. Hence, this review considers the sources, hazards and treatment methods of heavy metals pollution, particularly the biosorption mechanism of EPS to heavy metals and the influencing factors of the bio-adsorption process, which are significant in the efficient removal of heavy metals-containing wastewater treatment. This review also focuses on strengthening the process of EPS adsorption of heavy metals, which can further contribute to heavy metals removal. Finally, it has been proposed that improving the yield, stability, selectivity and recoverability of EPS is the key direction of further research.

Characterization and mechanism of Mn(II)-based mixotrophic denitrifying bacterium (Cupriavidus sp. HY129) in remediation of nitrate (NO3--N) and manganese (Mn(II)) contaminated groundwater

The co-contamination of groundwater with nitrate (NO₃^--N) and manganese (Mn(II)) is a global issue that needs to be efficiently remediated. In this research, a novel denitrifying and manganese-oxidizing strain HY129 was isolated from the sediments sample of a drinking water and identified as Cupriavidus sp. HY129. The remediation ability of strain HY129 regarding the nitrate and Mn(II) pollution were investigated. The removal efficiency of nitrate and Mn(II) were 99.81% (0.229 mgL^-1 h^-1) and 87.24% (0.233 mgL^-1 h^-1) in bacterial culture after 72 h, respectively. Moreover, the addition of Mn(II) significantly enhanced the denitrification process, while excessive concentration of Mn(II) caused more NO₂^--N accumulation. The impacts of adsorption and oxidation activity on Mn(II) removal were investigated. Protein in extracellular polymeric substance (EPS) which produced in the Mn-oxidizing process was speculated to be the main cause of extracellular adsorption of Mn(II). Characterization of biogenic manganese oxides (BMO) confirmed the formation of high-valent manganese and the trapping experiment with sodium pyrophosphate (NaPP) demonstrated the existence of Mn(III)-intermediates. Furthermore, multicopper oxidase gene amplification provided evidence for the molecular biology of Mn(II) oxidation by strain HY129.

Bacterial tolerance strategies against lead toxicity and their relevance in bioremediation application

Among heavy metals, lead (Pb) is a non-essential metal having a higher toxicity and without any crucial known biological functions. Being widespread, non-biodegradable and persistent in every sphere of soil, air and water, Pb is responsible for severe health and environmental issues, which need appropriate remediation measures. However, microbes inhabiting Pb-contaminated area are found to have evolved distinctive mechanisms to successfully thrive in the Pb-contaminated environment without exhibiting any negative effects on their growth and metabolism. The defensive strategies used by bacteria to ameliorate the toxic effects of lead comprise biosorption, efflux, production of metal chelators like siderophores and metallothioneins and synthesis of exopolysaccharides, extracellular sequestration and intracellular bioaccumulation. Lead remediation technologies by employing microbes may appear as potential advantageous alternatives to the conventional physical and chemical means due to specificity, suitability for applying in situ condition and feasibility to upgrade by genetic engineering. Developing strategies by designing transgenic bacterial strain having specific metal binding properties and metal chelating proteins or higher metal adsorption ability and using bacterial activity such as incorporating plant growth-promoting rhizobacteria for improved Pb resistance, exopolysaccharide and siderophores and metallothionein-mediated immobilization may prove highly effective for formulating bioremediation vis-a-vis phytoremediation strategies.

Comprehensive depiction of novel heavy metal tolerant and EPS producing bioluminescent Vibrio alginolyticus PBR1 and V. rotiferianus PBL1 confined from marine organisms

The current study depicts the isolation of luminescent bacteria from fish and squid samples that were collected from Veraval fish harbour. From Indian mackerel, total 14 and from squid, total 23 bioluminescent bacteria were isolated using luminescence agar medium. Two bioluminescent bacteria with highest relative luminescence intensity PBR1 and PBL1 were selected. These two isolates were subjected to detailed biochemical characterization and were tested positive for 5 out of 13 biochemical tests. Furthermore, both PBR1 and PBL1 were able to ferment cellobiose, dextrose, fructose, galactose, maltose, mannose, sucrose and trehalose with acid production. Based on 16S rRNA partial gene sequence analysis, PBR1 was identified as Vibrio alginolyticus and PBL1 as V. rotiferianus. Antibiotic susceptibility test using paper-disc method showed that PBR1 and PBL1 were sensitive to chloramphenicol, ciprofloxacin, co-trimoxazole, gatifloxacin, levofloxacin, linezolid ad roxithromycin out of 18 antibiotics tested. Moreover, both strains were evaluated for their exopolysachharide (EPS) producing ability where PBR1 and PBL1 were able to yield 1.34 g% (w/v) and 2.45 g% (w/v) EPS respectively from 5 g% (v/v) sucrose concentration. Heavy metal toxicity assessment was carried out using agar well diffusion method with eight heavy metals and both the strains were sensitive to As(III), Cd(II), Ce(II), Cr(III), Cu(II), Hg(II) and while they showed resistance to Pb(II) and Sr(II). Based on these results, a study was conducted to demonstrate bio-removal of Pb and Sr by EPS of PBR1 and PBL1. Fourier transform infrared (FTIR) spectra revealed the functional groups of EPS involved in interaction with the heavy metals. Owing to the sensitivity for the remaining heavy metals, these bioluminescent bacteria can be used further for the development of luminescence-based biosensor.

The mechanism for inhibiting acidification of variable charge soils by adhered Pseudomonas fluorescens

Acidification in variable charge soils is on the rise due to increased acid deposition and use of nitrogenous fertilizers. The associated low pH and cation exchange capacity make the soils prone to depleted base cations and increased levels of Al³⁺. Consequently, Al toxicity to plants and soil infertility decrease crop yield. This study was designed to investigate the effect of Pseudomonas fluorescens on the acidification of two Ultisols. The simulated acidification experiment demonstrated that the pH of bacteria-treated soil was higher than that of control under similar conditions, suggesting that the adhered bacteria inhibited soil acidification. This observation was attributed to the association of organic anions (RCOO^- or RO^-) on bacteria with H⁺ to form neutral molecules (RCOOH or ROH) and reducing the activity of H⁺ in solution. The bacteria also inhibited the increase in soil soluble Al and exchangeable Al during soil acidification. The adhesion of bacteria on the soils increased soil effective cation exchange capacity (ECEC) and exchangeable base cations at each pH compared to control. The release of exchangeable base cations from bacteria-treated soil, and the decrease in soil ECEC and exchangeable base cations with decreasing pH confirmed that protonation of organic anions on adhered bacteria was mainly responsible for the inhibition of soil acidification. The change of zeta potential of the bacteria with pH and the ART-FTIR analysis at various pH provided more evidence for this mechanism. Therefore, the bacteria in variable charge soils played an important role in retarding soil acidification.

Bacterial resistance to lead: Chemical basis and environmental relevance

Natural bacterial isolates from heavily contaminated sites may evolve diverse tolerance strategies, including biosorption, efflux mechanism, and intracellular precipitation under the continually increased stress of toxic lead (Pb) from anthropogenic activities. These strategies utilize a large variety of functional groups in biological macromolecules (e.g., exopolysaccharides (EPSs) and metalloproteins) and inorganic ligands, including carboxyl, phosphate and amide groups, for capturing Pb. The amount and type of binding sites carried by biologically originated materials essentially determines their performance and potential for Pb removal and remediation. Many factors, e.g., metal ion radius, electronegativity, the shape of the cell surface sheath, temperature and pH, are thought to exert significant influences on the abovementioned interactions with Pb. Conclusively, understanding the chemical basis of Pb-binding in these bacteria can allow for the development of effective microbial Pb remediation technologies and further elucidation of Pb cycling in the environment.

Inhibition of Cd accumulation in winter wheat (Triticum aestivum L.) grown in alkaline soil using mercapto-modified attapulgite

Cd contamination in agricultural soils threatens the safety of agricultural products and poses human health risk via food chain. However, the remediation of Cd polluted alkaline soils has not drawn the public concern, and the corresponding efficient amendments that can reduce Cd accumulation in crop grains are relatively few. In current study, mercapto-modified attapulgite (MA in abbreviation) was selected as the amendment to conduct winter wheat (Triticum aestivum L.) cultivation pot experiment to investigate the effect of MA on Cd accumulation in winter wheat and Cd bioavailability in alkaline soil. MA had no adverse impact on the normal growth of winter wheat but could inhibit Cd accumulation in wheat grain of both cultivars grown in alkaline soil with a maximum reduction of 75%, while pH-regulating amendment sepiolite had no reduction effect. In the term of soil chemistry, MA could decrease the zeta potential of soil particles and enhance the sorption amount of Cd on soil particles, resulted in the increase of Fe-Mn-oxides bounded Cd fraction in alkaline soil. The enhanced sorption effect combined with complexation effect of MA itself, made the exchangeable and bioavailable Cd concentrations in the soil decrease. In the term of plant uptake, MA could inhibit the uptake of Cd via roots from the soil, and hinder Cd transfer from roots to grains. MA had environmental friendliness and capability in the aspect of soil pH, effective cation exchange capacity and available micronutrients in the soil. The high performance of MA in inhabitation of Cd in winter wheat revealed that it was an efficient immobilization agent with great application potential for Cd-polluted alkaline soil.