Remediation Of Heavy Metal Pollution Research Articles

Microbial remediation of heavy metal-polluted water

Heavy metal pollution in water has become a global environmental problem, threatening aquatic ecosystems and human health. Physical and chemical methods can effectively remove heavy metal pollutants, while their applications are limited due to the high costs, complex operation, and susceptibility to secondary pollution. Bioremediation is the most promising method for eliminating toxic pollutants. Microorganisms including bacteria, fungi, and algae can convert toxic heavy metals into less toxic forms, which has become an effective and environmentally friendly solution for the remediation of heavy metal pollution in water environments. This paper expounds the toxicity and mechanism of heavy metal pollution, microbial remediation mechanisms, and primary microbial remediation strategies, providing a reference for the removal or reduction of metal pollutants in water environments as well as the development of related technologies.

Remediation of Cd-As-Ni co-contaminated soil by extracellular polymeric substances from Bacillus subtilis: Dynamic improvements of soil properties and ecotoxicity

As the primary reservoir of heavy metals in nature, soil is highly susceptible to significant co-contamination with Cd-As-Ni. In current study, extracellular polymeric substances (EPS) from Bacillus subtilis were utilized as a novel improver to simultaneously enhance soil property and restrain ecotoxicity in Cd-As-Ni co-contaminated soil. Our findings revealed that EPS effectively bound and immobilized free Cd, As, and Ni in soil and decreased the 49.73 % of soil available Cd, 79.16 % of As and 77.87 % of Ni contents by increasing soil pH, soil organic matter and cation exchange capacity. The EPS was also found to inhibit the Cd-As-Ni induced ecotoxicity in Caenorhabditis elegans by increasing the activities of antioxidant enzymes including superoxide dismutase, glutathione, and catalase. The remediation of EPS showed progressive improvement over time, and maintained a lasting effect after achieving peak efficiency. Our results might provide a new perspective on the potential of EPS in remediation of soil heavy metal pollution and the development and utilization of microbial biomass resources in a wider range.

Combined Application of High-Throughput Sequencing and Metabolomics to Evaluate the Microbial Mechanisms of Plant-Growth-Promoting Bacteria in Enhancing the Remediation of Cd-Contaminated Soil by Hybrid Pennisetum

The contamination of soil with the heavy metal cadmium (Cd) is increasingly prominent and severely threatens food security in China. Owing to its low cost, suitable efficacy, and ability to address the shortcomings of plant remediation by enhancing the ability of plants to take up Cd, plant–microbe combination remediation technology has become a research hotspot in heavy metal pollution remediation. A pot experiment was performed to examine the effects of inoculation with the plant-growth-promoting bacterium Brevibacillus sp. SR-9 on the biomass, Cd accumulation, and soil nutrients of hybrid Pennisetum. The purpose of this study was to determine how Brevibacillus sp. SR-9 alleviates stress caused by heavy metal contamination. High-throughput sequencing and metabolomics were used to determine the effects of inoculation on the soil bacterial community composition and microbial metabolic functions associated with hybrid Pennisetum. The results suggest that mutation of Brevibacillus sp. SR-9 effectively alleviates Cd pollution stress, leading to increased biomass and accumulation of Cd in hybrid Pennisetum. The aboveground biomass and the root weight increased by 12.08% and 27.03%, respectively. Additionally, the accumulation of Cd in the aboveground sections and roots increased by 21.16% and 15.50%, respectively. Measurements of the physicochemical properties of the soil revealed that the strain Brevibacillus sp. SR-9 slightly increased the levels of available phosphorus, total nitrogen, total phosphorus, and available potassium. High-throughput DNA sequencing revealed that Brevibacillus sp. SR-9 implantation modified the composition of the soil bacterial community by increasing the average number of Actinobacteria and Bacillus. The total nitrogen content of the soil was positively correlated with the Actinobacteria abundance, total phosphorus level, and available phosphorus level. Metabolomic analysis revealed that inoculation affected the abundance of soil metabolites, and 59 differentially abundant metabolites were identified (p < 0.05). Among these, 14 metabolites presented increased abundance, whereas 45 metabolites presented decreased abundance. Fourteen metabolic pathways were enriched in these metabolites: the folate resistance pathway, the ABC transporter pathway, D-glutamine and D-glutamic acid metabolism, purine metabolism, and pyrimidine metabolism. The abundance of the metabolites was positively correlated with the levels of available phosphorus, total potassium, total phosphorus, and total nitrogen. According to correlation analyses, the development of hybrid Pennisetum and the accumulation of Cd are strongly associated with differentially abundant metabolites, which also impact the abundance of certain bacterial populations. This work revealed that by altering the makeup of microbial communities and their metabolic processes, bacteria that promote plant development can mitigate the stress caused by Cd. These findings reveal the microbiological mechanisms through which these bacteria increase the ability of hybrid Pennisetum to take up the Cd present in contaminated soils.

Exogenous MgH2-derived hydrogen alleviates cadmium toxicity through m6A RNA methylation in rice

Cadmium (Cd) contamination poses a substantial threat to crop yields and human health. While magnesium hydride (MgH2) has been reported as a hydrogen (H2) donor that promotes plant growth under heavy metal contamination, its role in rice remains elusive. Herein, seedlings of Oryza sativa L. Japonica variety Zhonghua 11 (ZH11) were selected and exposed to 20 µL of 1-mol/L cadmium chloride (CdCl2) solution via hydroponics to simulate Cd stress. Meanwhile, 0.1 mg of MgH2 was used to slow-release H2 to the experimental group to explore its potential effects on rice over a 2-week period. The results indicated that Cd exposure severely inhibited the growth and development of ZH11 rice seedlings. However, the exogenous slow-release of H2 from MgH2 effectively mitigated this inhibitory effect by restoring the balance of reactive oxygen species (ROS), maintaining endogenous H2 homeostasis, and supporting the photosynthetic system. High-performance liquid chromatography analysis revealed that exogenous H2 reduces m6A RNA methylation levels in mRNA under Cd stress. Consequently, MeRIP-seq was conducted to investigate the effect of Cd exposure in rice in the presence and absence of H2. The m6A modifications were enriched at the start codon, stop codon, and 3′ UTR. By integrating RNA-seq data, 118 transcripts were identified as differentially methylated and expressed genes under Cd stress. These gene annotations were associated with ROS, biological stress, and hormonal responses. Notably, 297 differentially methylated and expressed genes were identified under Cd stress in the presence of H2, linked to heavy metals, protein kinases, and calcium signaling regulation. Cd strongly activates the MAPK pathway in response to stress. Exogenous H2 reduces Cd accumulation as well as enhances plant tolerance and homeostasis by lowering m6A levels, thereby decreasing the mRNA stability of these genes. Our findings indicate that MgH2, by supplying H2, regulates gene expression through m6A RNA methylation and confers Cd tolerance in rice. This study provides potential candidate genes for studying the remediation of heavy metal pollution in plants.

Study on soil heavy metal pollution and microbial remediation technology

With the rapid development of social economy and industrialization, the soil has been seriously polluted and damaged. As far as the environmental pollution situation in China is concerned, heavy metal pollution accounts for a relatively high proportion and causes great harm to the soil environment. The quality of soil profoundly affects the quality of life for humans and the state of human development. Therefore, it is urgent to control heavy metal pollution in soil. Among a series of soil remediation technologies, microbial remediation is an economical and sustainable remediation technology for soil heavy metal pollution. This review starts with the hazards of soil heavy metal pollution, analyzes the current soil heavy metal pollution situation in China, elaborates on the connection of microbial remediation technology, studies the role of microbial remediation technology in soil heavy metal pollution remediation, and explores practical applications of this technology. Lastly, reasonable remediation measures based on microbial remediation technology for soil heavy metal pollution were proposed and discussed.

Disclosing the key role of Fe/As/Cu in community co-occurrence and microbial recruitment in metallurgical ruins

Mining activities have led to the persistent presence of substantial heavy metals at metallurgical sites. However, the impact of long-term and complex heavy metal pollution in metallurgical ruins on the structure and spatial shift of microbiome remains unclear. In this study, we focused on various types of metallurgical sites to uncover the occurrence of heavy metals in abandoned mines and the response patterns of microbial communities. The results indicate that mining activities have caused severe exceedances of multiple heavy metals, with AsBio, CuBio, and FeBio being the primary factors affecting community structure and function. Co-occurrence network analyses suggest that several genera, including Ellin6515, Cupriavidus, Acidobacteria genus RB41, Vicinamibacteraceae, Blastococcus, and Sphingomonas, may play significant roles in the synergistic metabolism of communities responding to Fe-Cu-As stress. Although random dispersal contributed to community migration, null models emphasized that variable selection predominates in the spatial turnover of community composition. Additionally, metagenomic prediction (PICRUSt2) identified key genes involved in stress and detoxification strategies of heavy metals. The composite heavy metal stress strengthened the relationship between network structure and the potential function of the community, along with critical ecosystem functions. Our findings demonstrated that microbial interactions were crucial for ecosystem management and the ecological consequences of heavy metal pollution remediation.

A comprehensive investigation of the adsorption behaviour and mechanism of industrial waste sintering and bayer red muds for heavy metals.

The issue of heavy metal pollution is a critical global concern that requires urgent solution. However, conventional heavy metal adsorbents are too costly to be applied in large-scale engineering. In this study, adsorption behavior and mechanism of sintering red mud (RM-A) and bayer red mud (RM-B) for heavy metals were investigated to address the disposal of red mud as industrial waste and remediation of heavy metal pollution. Batch adsorption experiments were conducted to explore the adsorption performances of RM-A and RM-B under various conditions. Characterization of RM-A and RM-B before and after adsorption by XRD, FTIR and SEM-EDX was applied to investigate the specific adsorption behavior and mechanism. Adsorption experiments of both RM-A and RM-B fitted pseudo-second-order kinetic model and Langmuir isotherm model, with estimated maximum adsorption capacity of 21.96 and 25.19 mg/g for Cd2+, 21.47 and 26.06 mg/g for Cu2+ and 55.47 and 59.65 mg/g for Pb2+, respectively. Precipitation transformation of calcite was the primary adsorption mechanism for RM-A, whereas ion exchange of cancrinite, surface coordination compounds of hematite and minor precipitation transformation of calcite accounted for the adsorption mechanism for RM-B. Overall, RM-A and RM-B exhibited best adsorption performance for Pb2+, with RM-B showing greater adsorption capacity attributed to its higher specific surface area. This study compared the adsorption properties of RM-A and RM-B for the first time and demonstrated that both red muds can be effectively applied to remove heavy metals, thereby contributing to the sustainable industrial waste management and resourceful reuse.

Zeolite, Humus and Biochar Remediation of Heavy Metal Contaminated Soil: A Review

With the swift advancement of industrialization and urbanization, soil heavy metal contamination has grown increasingly severe, presenting a grave menace to the environment and human health. As efficacious soil remediation substances, zeolite, humus, and biochar exhibit considerable potential in the treatment of heavy metal pollution. In this article, the research progress of zeolite, humus, and biochar in the remediation of heavy metal pollution in soil was reviewed, the remediation mechanisms, influencing factors, and practical application effects were analyzed, and the future research direction was prospected. Through comprehensive analysis and discussion, the aim is to offer useful references for the control of soil heavy metal pollution.

Leaching behavior and release mechanism of pollutants from different depths in a phosphogypsum stockpile

Phosphogypsum (PG), a byproduct during the production of phosphoric acid and phosphate fertilizers, is predominantly stockpiled with a height greater than hundreds of meters. In this study, the leaching behavior of pollutants from PG stored at different depths was systematically investigated through batch tests, column tests, and geochemical modeling. PG samples were collected at different depths within a range of 48 m from a large-scale PG stack in China. The results showed that the pH, electrical conductivity, and elemental concentration of the leachate exhibited spatial variability in terms of the depth distribution, with evident bottom enrichment effects for metals and soluble salts. The pH-dependent leaching tests investigated the impact of pH variations on the solubility of various elements in PG, with a specific focus on elements precipitation occurring within the natural pH range. The geochemical modeling of leaching tests conducted by PHREEQC enabled the identification of the dominant phases controlling the solubilization of the elements, as well as the dynamic process of changes in element forms and concentrations with pH variation. Column leaching tests reveal the differences in pollutant properties between the unsaturated and saturated zones within the PG stack and categorize the leaching mechanisms of elements into three models including dissolution, diffusion, and wash-off. This study aims to reveal the leaching characteristics of PG at different depths, so as to provide a data foundation for the design of liner system, leachate management strategies, and remediation of heavy metal pollution of PG stack sites.

Precision Remediation of Mining Soils through On-Site Investigation and Large-Scale Synthesized Ferrosilicate

To seek a restoration plan for the safe use of agricultural land around mining areas, this study focuses on the regions around a mining plant in Huidong County, western Sichuan Province, affected by lead–zinc mining, and the precise remediation of heavy metal pollution through large-scale synthesis of iron silicate. In this study, we investigated heavy metal pollution in the vicinity of the mining area and proposed a treatment strategy using large-scale synthesis of iron silicate to mitigate this pollution. According to field investigation and sampling analysis, the collected soil samples contained excessive Cd, Pb, and Zn. Cd is a heavy metal related to lead–zinc mining. The planting of crops such as loquats and garlic with a high accumulation coefficient for Cd was found inappropriate for the research area. Instead, it was recommended to plant economically important crops like mangoes and peaches which had lower heavy metal accumulation. On the basis of field investigation, the study area was seriously polluted by heavy metals, among which Cd was 4.0 times higher than the standard of agricultural land. In order to accurately passivate excessive Cd, Zn, and Pb, iron silicate material was put into mass production. In situ passivation experiments showed that when the soil water content was between 25% and 20%, adding 4% silicate material could rapidly reduce the content of effective heavy metals in the soil and the heavy metal content of garlic and other cash crops in the research area by about 8%. After conducting a field investigation, it has been determined that the large-scale preparation of iron silicate can accurately repair soil contaminated by heavy metals in the vicinity of mining areas. In conclusion, iron silicate is capable of effectively reducing the pollution of heavy metals on agricultural land and facilitating the safe utilization of such land.

Pb2+ and Cd2+ ion adsorption capability of a novel hydrotalcite-like absorbent FeMnNi-LTH in water

This paper discusses the application of a layered triple hydroxide (FeMnNi-LTH) in removing Pb2+ and Cd2+ ions from aqueous solutions. The material was synthesized via co-precipitation, adhering to a molar ratio of 1:1:2 (Fe:Mn:Ni). It was characterized using FTIR, XRD, SEM and TEM. The results indicate that the synthesized material is classified as a hydrotalcite and exhibits a well-defined layered structure. Batch experiments were conducted to investigate the adsorption of Pb2+ and Cd2+ by FeMnNi-LTH, taking into account various factors such as coexisting ions, pH, temperature, adsorbent dosage, and contact time. The experimental results showed that the adsorption capacity of this material for Pb2+ and Cd2+ was 253.89 mg/g and 56.90 mg/g at 25 °C, respectively. Moreover, it exhibits a consistent high adsorption capacity across a broad pH range (pH 3–5.5). When cations coexist, they compete for adsorption sites in the following order: Zn2+ > Ca2+ > Mg2+ > Cd2+/Pb2+. Based on the calculated thermodynamic parameters, it is inferred that the adsorption process is endothermic and spontaneous. The adsorption mechanism, as analyzed by modeling and characterization, involves isomorphic substitution, surface complexation, precipitation, electrostatic attraction, and physical adsorption. The quantitative analysis of the adsorption mechanism revealed that FeMnNi-LTH primarily adsorbs Pb2+ and Cd2+ via precipitation and surface complexation. It was revealed by comparison with other adsorbents that the synthesized FeMnNi-LTH can be used for remediation of heavy metal pollution in water.

Mechanisms of Cadmium stress response in watermelon: Insights from physiological, transcriptomic, and metabolic analyses

Cadmium (Cd) contamination of soil may lead to Cd stress for plants, which significantly hinders plant growth and development, posing a risk to human health through the consumption of Cd-contaminated foods. Watermelon (Citrullus lanatus), a widely consumed fruit, is particularly affected by Cd stress globally, yet the mechanisms underlying its response are not well understood. Here, we subjected watermelon seedlings to simulated Cd stress treatment and explored the physiological, transcriptomic, and metabolic response. Our findings revealed that Cd stress treatment led to increased accumulation of reactive oxygen species (ROS) in watermelon leaves. Transcriptome sequencing unveiled a multitude of osmotic and oxidative stress-responsive genes, including peroxidase (POD), MYB, voltage-dependent anion channel (SLAC1), and ABC transporter. KEGG enrichment analysis highlighted the predominant enrichment of Cd stress-responsive genes in pathways such as glutathione (GSH) metabolism, MAPK signaling, and biosynthesis of secondary metabolites. Within the GSH metabolism pathway, several glutathione S-transferase (GST) genes were up-regulated, alongside phytochelatin synthetase (PCS) genes involved in phytochelatin synthesis. In the MAPK signaling pathway, genes associated with ABA and ethylene signal transduction showed up-regulation following Cd stress. Metabolomic analysis demonstrated that Cd stress enhanced the production of amino acids, phenolamines, and esters. Overall, our study elucidates that watermelon responds to Cd stress by activating its antioxidant system, GSH metabolism pathway, MAPK signal pathway, and biosynthesis of key metabolites. These findings offer valuable insights for the remediation of heavy metal pollution in soil affecting plant life.

Contamination Characteristics and Source Apportionment of Heavy Metal in the Topsoil of a Small Watershed in South Taihang

With the rapid development of industrialization and urbanization, the issue of soil environmental pollution is becoming more and more prominent, especially concerning heavy metal contamination, which has garnered significant scholarly attention. The surface watershed formed by waterline is influenced by various factors such as topography, industrial emissions, and agricultural runoff, resulting in a complex process of migration and accumulation of heavy metal elements from multiple sources. In this study, the pollution characteristics and sources of heavy metal elements Hg, As, Pb, Ni, Cd, Cr, Cu and Zn in 165 surface soil samples from the Manghe River watershed in Jiyuan City were comprehensively analyzed using a variety of methods, including statistics, geostatistics, enriched factor analysis and the Positive Matrix Factorization Model (PMF). The results showed that the concentrations of Hg, Cd, As, Cu, Pb and Zn exceeded their corresponding background values with varying degrees of enrichment. Notably, the average contents of Cd, Hg and Pb were 26.70 times, 3.69 times and 4.49 times higher than those in Chinese soils on average, respectively, showing obvious enrichment characteristics. Moreover, there were distinct spatial distribution patterns for each heavy metal element; Ni and Cr exhibited similar trends mainly controlled by the parent material, while human activities significantly affect the other six elements forming high-value areas around mining and related industries. It is noteworthy that Cu, Hg and Zn were influenced by dominant wind direction in autumn and winter, forming sub-high-value zones in southern forested areas; meanwhile, Cu and Zn were also influenced by agricultural fertilizer application as well as surface runoff, leading to secondary high-value areas in the dryland areas. Further analysis revealed a significant positive correlation among these heavy metal elements, suggesting that they may share common sources. Through the PMF Model, four main factors were identified, with factor 2 (36.25%), factor 1 (23.00%), factor 3 (21.20%) and factor 4 (19.55%) ranked in descending order of contribution rate. The heavy metal pollution in the study area was attributed to anthropogenic activities and natural factors, accounting for 63.75% and 36.25%, respectively. Coal mining, chemical industry smelting, vehicle emissions and excessive use of agrochemicals were identified as the main sources of heavy metal pollution. These pollutants entered the soil through direct emissions, atmospheric deposition, transportation and agricultural activities, exerting a significant impact on the soil environment. Therefore, delving into the spatial distribution pattern of soil heavy metal pollution and precise analysis of its sources are of great importance for effective treatment and remediation of soil heavy metal pollution in small watersheds, maintaining healthy soil ecology and safeguarding human health.

Adsorption of Cd2+ by Lactobacillus plantarum Immobilized on Distiller's Grains Biochar: Mechanism and Action.

Immobilized microbial technology has recently emerged as a prominent research focus for the remediation of heavy metal pollution because of its superior treatment efficiency, ease of operation, environmental friendliness, and cost-effectiveness. This study investigated the adsorption characteristics and mechanisms of Cd2+ solutions by Lactobacillus plantarum adsorbed immobilized on distiller's grains biochar (XIM) and Lactobacillus plantarum-encapsulated immobilized on distiller's grains biochar (BIM). The findings reveal that the maximum adsorption capacity and efficiency were achieved at a pH solution of 6.0. Specifically, at an adsorption equilibrium concentration of cadmium at 60 mg/L, XIM and BIM had adsorption capacities of 8.40 ± 0.30 mg/g and 12.23 ± 0.05 mg/g, respectively. BIM demonstrated noticeably greater adsorption capacities than XIM at various cadmium solution concentrations. A combination of isothermal adsorption modeling, kinetic modeling, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffractometer (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses showed that cadmium adsorption by XIM primarily involved physical adsorption and pore retention. In contrast, the adsorption mechanism of BIM was mainly attributed to the formation of Cd(CN)2 crystals.

Sustainable Remediation of Soil and Water Utilizing Arbuscular Mycorrhizal Fungi: A Review.

Phytoremediation is recognized as an environmentally friendly technique. However, the low biomass production, high time consumption, and exposure to combined toxic stress from contaminated media weaken the potential of phytoremediation. As a class of plant-beneficial microorganisms, arbuscular mycorrhizal fungi (AMF) can promote plant nutrient uptake, improve plant habitats, and regulate abiotic stresses, and the utilization of AMF to enhance phytoremediation is considered to be an effective way to enhance the remediation efficiency. In this paper, we searched 520 papers published during the period 2000-2023 on the topic of AMF-assisted phytoremediation from the Web of Science core collection database. We analyzed the author co-authorship, country, and keyword co-occurrence clustering by VOSviewer. We summarized the advances in research and proposed prospective studies on AMF-assisted phytoremediation. The bibliometric analyses showed that heavy metal, soil, stress tolerance, and growth promotion were the research hotspots. AMF-plant symbiosis has been used in water and soil in different scenarios for the remediation of heavy metal pollution and organic pollution, among others. The potential mechanisms of pollutant removal in which AMF are directly involved through hyphal exudate binding and stabilization, accumulation in their structures, and nutrient exchange with the host plant are highlighted. In addition, the tolerance strategies of AMF through influencing the subcellular distribution of contaminants as well as chemical form shifts, activation of plant defenses, and induction of differential gene expression in plants are presented. We proposed that future research should screen anaerobic-tolerant AMF strains, examine bacterial interactions with AMF, and utilize AMF for combined pollutant removal to accelerate practical applications.

Modification of Yarrowia lipolytica via metabolic engineering for effective remediation of heavy metals from wastewater

With the increasing demand for heavy metals due to the advancement of industrial activities, large proportions of heavy metals have been discharged into aquatic ecosystems, causing serious harm to human health and the environment. Existing physical and chemical methods for recovering heavy metals from wastewater encounter challenges, such as low efficiency, high processing costs, and potential secondary pollution. In this study, we developed a novel approach by engineering the endogenous sulphur metabolic pathway of Yarrowia lipolytica, providing it with the ability to produce approximately 550 ppm of sulphide. Subsequently, sulphide-producing Y. lipolytica was used for the first time in heavy metal remediation. The engineered strain exhibited a high capacity to remove various heavy metals, especially achieving over 90 % for cadmium (Cd), copper (Cu) and lead (Pb). This capacity was consistent when applied to both synthetic and actual wastewater samples. Microscopic analyses revealed that sulphide-mediated biological precipitation of metal sulphides on the cell surface is responsible for their removal. Our findings demonstrate that sulphide-producing yeasts are a robust and effective bioremediation strategy for heavy metals, showing great potential for future heavy metal pollution remediation practices.

Peptides Used for Heavy Metal Remediation: A Promising Approach.

In recent years, heavy metal pollution has become increasingly prominent, severely damaging ecosystems and biodiversity, and posing a serious threat to human health. However, the results of current methods for heavy metal restoration are not satisfactory, so it is urgent to find a new and effective method. Peptides are the units that make up proteins, with small molecular weights and strong biological activities. They can effectively repair proteins by forming complexes, reducing heavy metal ions, activating the plant's antioxidant defense system, and promoting the growth and metabolism of microorganisms. Peptides show great potential for the remediation of heavy metal contamination due to their special structure and properties. This paper reviews the research progress in recent years on the use of peptides to remediate heavy metal pollution, describes the mechanisms and applications of remediation, and provides references for the remediation of heavy metal pollution.

Molecular Basis of Energy Crops Functioning in Bioremediation of Heavy Metal Pollution

Heavy metal pollution is a gradually growing environmental issue that hinders the growth and development of plants, and also destabilizes soil. Consequently, eco-friendly phytoremediation methods have gained traction, with energy crops emerging as a particularly effective solution. Energy crops not only provide high-quality plant materials for detoxification and remediation of heavy metal pollution, but also possess energy properties conducive to biofuel production. Therefore, this paper delves into the tolerance mechanism of energy crops towards heavy metal toxicity, elucidating processes such as root complex-mediated inhibition of metal migration and response to reactive oxygen species (ROS) through heavy metal-related proteins, enzyme systems, reactive nitrogen species (RNS), and hormones. Moreover, it summarizes the heavy metals remediation mechanisms of energy crops, including uptake, translocation, chelation, immobilization, and sequestration. This paper explores applications of energy crops in heavy metal pollution remediation, emphasizing the methods for efficient biochar remediation and biofuel generation. Furthermore, potential challenges in using energy crops for heavy metal pollution remediation are outlined. By systematically examining the function mechanisms and prospective applications of energy crops in heavy metal pollution bioremediation, this paper serves as a valuable reference for both research and practical implementation in this field.

Exploring the mechanism of removing Cd from polluted soil using electrochemical leaching with straw carbon film electrode

The study presents a novel approach to remediating heavy metal-contaminated soil using electrochemical technology and chemical leaching. The researchers developed a new electrode material from waste straw and an environmentally friendly leaching agent using straw fermentation liquid. Combining electrochemical technology with chemical leaching provides a powerful remediation solution for heavy metal-contaminated soil, demonstrating efficiency and thoroughness. However, challenges include developing recyclable electrode materials and environmentally friendly leaching agents. This study addresses these challenges by pioneering a biochar-based electrode material and an eco-friendly leaching agent. Waste straw undergoes pyrolysis at 1000 °C to produce a conductive biochar, which is then combined with ethyl cellulose to form a film, creating biochar electrode materials. The developed straw fermentation solution, an environmentally friendly leaching agent, is used for Cd-contaminated soil remediation through combined electrochemical-chemical leaching. Results show soil Cd removal efficiency peaking at 59.5% with a singular chemical leaching agent. The combined method increases the Cd removal rate to a maximum of 91%. Furthermore, the study elucidate the potential mechanism of cadmium removal through techniques such as XRD, SEM, and infrared spectroscopy. To evaluate the efficacy of our approach, the study conducted Chinese cabbage pot-cultivation experiments. Remarkably, the physicochemical properties of soil remained largely unchanged after the reaction, while Chinese cabbage growth in treated soil surpassed that of the control group. This study not only removes Cd from the soil, reducing secondary pollution, but also establishes electrode recyclability, offering a prospective solution for large-scale soil heavy metal pollution remediation.

Physiological and transcriptomic analyses reveal the cadmium tolerance mechanism of Miscanthus lutarioriparia.

Miscanthus lutarioriparia is a promising energy crop that is used for abandoned mine soil phytoremediation because of its high biomass yield and strong tolerance to heavy metals. However, the biological mechanism of heavy metal resistance is limited, especially for applications in the soil restoration of mining areas. Here, through the investigation of soil cadmium(Cd) in different mining areas and soil potted under Cd stress, the adsorption capacity of Miscanthus lutarioriparia was analyzed. The physiological and transcriptional effects of Cd stress on M. lutarioriparia leaves and roots under hydroponic conditions were analyzed. The results showed that M. lutarioriparia could reduce the Cd content in mining soil by 29.82%. Moreover, different Cd varieties have different Cd adsorption capacities in soils with higher Cd concentration. The highest cadmium concentrations in the aboveground and belowground parts of the plants were 185.65 mg/kg and 186.8 mg/kg, respectively. The total chlorophyll content, superoxide dismutase and catalase activities all showed a trend of increasing first and then decreasing. In total, 24,372 differentially expressed genes were obtained, including 7735 unique to leaves, 7725 unique to roots, and 8912 unique to leaves and roots, which showed differences in gene expression between leaves and roots. These genes were predominantly involved in plant hormone signal transduction, glutathione metabolism, flavonoid biosynthesis, ABC transporters, photosynthesis and the metal ion transport pathway. In addition, the number of upregulated genes was greater than the number of downregulated genes at different stress intervals, which indicated that M. lutarioriparia adapted to Cd stress mainly through positive regulation. These results lay a solid foundation for breeding excellent Cd resistant M. lutarioriparia and other plants. The results also have an important theoretical significance for further understanding the detoxification mechanism of Cd stress and the remediation of heavy metal pollution in mining soil.