Diagnosis of soil contamination using microbiological indices: A review on heavy metal pollution

A global meta-analysis reveals effects of heavy metals on soil microorganisms

Heavy metal (HM) contamination disrupts soil ecosystem functions. Microorganisms are pivotal for sustaining soil health, but accurately assessing the ecological risks of HM contamination to microorganisms remains challenging. Here, we conducted a meta-analysis synthesizing 914 datasets from 72 studies to quantify and evaluate the impacts of HMs on microorganisms. The overall effect value results indicate that HM negatively impacts most microbiological indicators, with bacterial abundance (-38 %), fungal abundance (-18 %), microbial biomass carbon (-42 %), microbial biomass nitrogen (-44 %), arylsulfatase (-45 %) and dehydrogenase activity (-66 %) were significantly reduced (p < 0.01), suggesting they can act as sensitivity indicators for assessing ecological risk of microorganisms. Compared to bacteria, fungal indicators (e.g., fungal community structure and Shannon index) are less responsive to HM contamination. At low potential ecological risk index (RI < 150), HM contamination positively impacted certain microbial indicators, such as fungal abundance, fungal Shannon index, and β-glucosidase activity. With increasing RI levels, the negative effects of HMs on microorganisms became more pronounced. Microbiological indicators in acidic soils (pH < 6.5), coarse textured soils, and mining soils were more negatively affected by HMs. Random forest and structural equation modeling analysis also identified RI levels and pH as crucial factors in determining the microbial response to HMs. Adjusted RI (adRI) were calculated using adjusted toxicity factors (adTF). The adRI demonstrated stronger correlations with microbial indicators and lower root-mean-square error (RMSE) in the random forest model than the RI, indicating that adTF is a more effective method for evaluating the effects of HMs on microorganisms. This study enhances the accuracy of quantifying and assessing HM impacts on microorganisms, offering crucial scientific basis for environmental protection and soil remediation.

Soil resource availability regulates the response of micro-food web multitrophic interactions to heavy metal contamination

The effects of heavy metal contamination on soil biomes have been of considerable interest. However, the effects of heavy metal pollution on the interactions between soil multi-trophic biota in soil food webs and the regulatory mechanisms still need more research, especially in different soil situations. This study examined the impact of heavy metal contamination on soil micro-food web in two distinct soil resource availability situations. Under low soil resources availability situation, heavy metals mainly affected the community structure of soil bacteria and nematodes, with the number of edges of the bacterial network and network complexity reduced by 60.5% and 187%, respectively. In addition, the presence of heavy metals led to a significant reduction in the energy flow from soil resources to bacterivores in the nematode food web. For micro-food webs, heavy metal contamination increased the network average degree by 18.8% and 11.56% in the low and high resource availability situations, respectively. However, in high soil resource availability, heavy metal contamination decreased micro-food web stability and eased competitive relationships among multitrophic organisms and increased microbial carbon limitation and mitigates nitrogen limitation. In low soil resource availability, it increased network stability and shifted relationships among micro-food web organisms from cooperative to competitive and decreased microbial carbon limitation and aggravated nitrogen limitation. This study offers new research insights into the feedback discrepancy between resource availability and pollution stress from the perspective of multitrophic level interactions and further deepens the understanding of the environmental impacts of heavy metal pollution at the ecosystem level.

Water regime alters microbial mechanisms of N2O emission in metal-contaminated paddy soils

Microorganisms are essential for soil nitrous oxide (N2O) emissions through participating in key nitrogen (N)-related processes. However, the effect of water regimes on the interactions between N2O emissions and microbial processes in metal-contaminated soils is unclear. Here, we conducted a soil microcosm experiment with two water management strategies (non-flooding and flooding) and six metal addition treatments including low (2 and 200 mg kg-1) and high (10 and 1000 mg kg-1) levels of individual and combined Cd and Cu. The effects of high levels of individual Cd and Cu contamination on soil N2O emissions varied depending on water regimes, showing antagonistic effects under non-flooding conditions and synergistic effects under flooding conditions. High levels of co-contamination significantly inhibited nitrification under both water regimes, primarily due to reduced abundance of Nitrosospira. In contrast, this co-contamination decreased the abundance of Ramlibacter, thereby inhibiting denitrification and dissimilatory nitrate reduction to ammonium (DNRA) under flooding conditions. The inhibition of these key microorganisms and their mediated N-cycle processes reduced soil N2O emissions under both water regimes. This reduction was greater under flooding conditions because more N-related processes were inhibited. Metagenomic binning further indicated that Nitrosospira carried nitrifying genes, while Ramlibacter contained genes involved in denitrification, assimilatory nitrate reduction to ammonium (ANRA), and DNRA. These findings implied that both microorganisms had potential to produce N2O. Overall, water management strategies and metal contamination altered the microbial processes of N2O emissions, highlighting the importance of appropriate water management in mitigating greenhouse gas emissions from metal-contaminated paddy soils in southern China.

Micro-nano bubble hydrogen water irrigation improves the Cd tolerance of Ipomoea aquatica Forssk.: Rhizosphere micro-biotas modulation and oxidative stress alleviation

The application of exogenous hydrogen has been found to be beneficial for plant resistance to cadmium (Cd) stress; however, it is difficult to apply hydrogen-rich water for long-term application in agriculture due to the low solubility and rapid fugacity of H2 in water. The integration of micro-nano bubble hydrogen (MNBH) water with subsurface drip irrigation (SDI) technology could address such problems. However, the adaptation and response mechanisms of plants and soil to MNBH are still poorly understood. Here, by focusing on a Cd-susceptible plant water spinach (Ipomoea aquatica Forssk.), we found that MNBH (applied via an SDI system) significantly improved yield, plant height, and root morphological traits; increased chlorophyll content and photosynthetic rate; and increased levels of metallothioneins and stress-response phytohormones (ABA and SA), which was helpful in scavenging reactive oxygen species, decreasing the uptake of Cd by the plants, and alleviating Cd-induced oxidative stress. More importantly, MNBH application significantly improved the rhizosphere soil environment (pH, enzyme activities) and reconstituted the soil microbial community, which may play a critical role in reducing soil Cd bioavailability and promoting plant growth. This is the first case of MNBH water irrigation to mitigate soil Cd contamination, and the results of this study could contribute to the understanding of the potential effects of MNBH on the soil environment and the mechanism of action on plant resistance to Cd stress.

Assessing the exposure of lead, cadmium, and arsenic on growth parameters and antioxidant defense system in wheat

Heavy metals (HMs) pollution of soil adversely impacts agricultural productivity and poses risks to public health, necessitating regular and timely monitoring of HMs accumulation in soils. Wheat (Triticum aestivum L.), as a globally cultivated staple crop, is particularly vulnerable to HM-induced stress, which can significantly reduce its yield and quality. The purpose of the experiment was to study the effect of lead (Pb), cadmium (Cd), and arsenic (As) on the growth, photosynthetic pigments content, enzymatic and low molecular weight antioxidants, and the uptake of metals in the wheat seedlings. We carried out a pot experiment in which HMs were introduced into the soil Pb (1300 mg kg-1), Cd (20 mg kg-1), As (100 mg kg-1) separately and all together in one combination and an uncontaminated control. The doses of HMs corresponded to the registered high pollution level in impact zone (10 approximate permissible concentrations). The results showed that HMs contamination of the soil affected the growth, photosynthetic pigments and antioxidant enzymes activities in wheat. The polyelement contamination significantly reduced root growth. The polyelement contamination led to an intensification of lipid peroxidation processes, which was reflected in an increase in malondialdehyde content in leaves and roots by 39% and 127% compared with the control. The cumulative exposure affected antioxidants in wheat, leading to deregulation of defense mechanisms, characterized by an increase in reduced glutathione content in leaves and roots by 23% and 69%, an increase in proline and ascorbic acid content in leaves by 174% and 20%, and a decrease in roots by 80% and 43%, respectively. These results highlight that HMs contamination not only inhibited growth but also affected antioxidant defense system. Therefore, developing effective strategies to mitigate HMs-induced stress and enhance wheat production is crucial for sustainable agriculture in contaminated environments.

Microbial diversity and community assembly in heavy metal-contaminated soils: insights from selenium-impacted mining areas

The mining industry in China plays a pivotal role in economic development but also leads to severe environmental issues, particularly heavy metal pollution in soils. Heavy metal pollution significantly impacts soil microbial communities due to its persistence and long-term residual effects. We assessed changes in microbial diversity, community structure, and assembly mechanisms in selenium-impacted soils. This study investigates the impacts of selenium (Se) and other heavy metals on soil microbial communities in selenium-rich mining areas using full-length 16S rRNA gene sequencing. Our results showed that Se and other heavy metal contamination significantly altered microbial community composition, favoring metal-tolerant phyla such as Proteobacteria, Actinobacteriota and Firmicutes, while reducing the abundance of sensitive groups like Acidobacteriota and Chloroflexi. Microbial diversity decreased as Se and other heavy metal concentrations increased. Mantel test analysis revealed that soil total potassium (TK), soil organic carbon, total nitrogen, and several other metals, including zinc, niobium, titanium (Ti), manganese, rubidium, barium, potassium, cobalt, gallium (Ga), Se, chromium (Cr), vanadium, and copper were significantly and positively correlated with microbial community composition across all soil samples. Random forest analysis showed that soil TK and multiple elements [Cr, Ti, nickel (Ni), Ga and Se] were the most important predictors of bacterial diversity, emphasizing the role of multiple elements in shaping microbial communities. Co-occurrence network analysis revealed that Se and other heavy metal contamination reduced network complexity and stability, with high Se-contaminated soils exhibiting fragmented microbial networks. Community assembly was primarily driven by drift in control soils, whereas dispersal limitation became more prominent in Se-contaminated soils due to heavy metal toxicity. These findings highlight the ecological consequences of heavy metal pollution on microbial communities and offer valuable insights for effective soil management and remediation strategies.

Microbial community structure and causal analysis in sediments of shallow eutrophic freshwater lakes under heavy metal compound pollution

Heavy metals, due to their toxicity, persistence, and non-biodegradability, have become some of the most severe environmental pollutants globally. Their accumulation in lake sediments can significantly impact aquatic ecosystems' biogeochemical cycles by altering the ecological dynamics of microbial communities. To further elucidate the mechanisms underlying microbial responses to complex heavy metal pollution in lake sediments, sediment samples were collected from Nan Yi Lake, and their physicochemical properties and microbial composition were systematically analyzed. The results demonstrated that the sediments of Nan Yi Lake were significantly contaminated with heavy metals, which were identified as the predominant factors shaping microbial community structure. Heavy metals influenced microbial richness and distribution patterns along sediment depth gradients, driving the establishment of optimal ecological niches. Meanwhile, other physicochemical factors indirectly affected microbial communities by modulating the concentration of heavy metals. Furthermore, the microbial co-occurrence network was closely associated with the concentrations of Fe and As, with sediment particle size also playing a contributing role. This study highlights the intricate interactions between physicochemical factors and microorganisms, offering critical insights into the multifaceted impacts of heavy metal compound pollution on lake ecosystems. It provides a scientific foundation for effective management of lake environmental pollution and ecological restoration efforts.

Synergy of plastics and heavy metals weakened soil bacterial diversity by regulating microbial functions in the Qinghai-Tibet Plateau

How plastics coupled with metals regulate microbial functions-diversity relationships remain unknown in plateau soil environment. Three representative catchments in the Qinghai-Tibet Plateau, focusing on microplastics, their plasticisers, and metals in soils, were investigated. This research explores responses of bacterial diversity and functions to the co-existence of target pollutants, and pathways by which target pollutants regulate the diversity. Soil bacterial beta diversity and functional genes exhibited negative correlations with phthalate esters across three catchments (p < 0.05). Dibutyl phthalate emerged as a primary factor affecting beta diversity, rather than the quantity of microplastics. Additionally, the synergy of cadmium and fiber-shaped microplastics exacerbated the impact on diversity. Structural equation modeling further elucidated that plastics, copper, and iron influenced nirK/nirS genes and phoD gene, subsequently affected cbbL/cbbM genes, and ultimately the diversity. In this context, microplastics, phthalate esters and copper, iron exerted antagonistic effects on one another. Consequently, the co-existence of plastics and cadmium weakened soil bacterial diversity in the Qinghai-Tibet Plateau by disrupting microbial functions, but micronutrients alleviated these negative impacts. This research reveals that the co-existence of plastics and metals regulates soil bacterial diversity in the Qinghai-Tibet Plateau, providing a valuable reference for the protection of microbial ecology in plateau regions.

The influences of heavy metals on soil microbial C, N, P cycling and heavy metal resistance under different fertilization regimes

Heavy metal pollution changes microbial heavy metal resistance and ecological functions of carbon (C), nitrogen (N), phosphorus (P), sulfur (S) cycling, although the connections between these changes have been insufficiently explored. The study investigated the effects of varying levels of heavy metal pollution and nutrient on microbial heavy metal resistance and C, N, P, S cycling in soils. The results indicated that heavy metal pollution significantly enhanced microbial metabolic potentials, such as denitrification, Dissimilatory nitrate reduction (DNRA), P uptake and transport, as well as resistance to Cu, Cd, Pb, and As. Heavy metals and pH were identified as major factors affecting these microbial functions. The diversity and evenness of host microorganisms carrying functional genes and heavy metal resistance genes (MRGs) were significantly affected by heavy metal pollution, but this effect was alleviated with the nutrient increased. In low-nutrient soils, a strong correlation between nitrogen degradation and Zn resistance was observed due to heavy metal pollution. As nutrients increased, the close correlations between hemicellulose, P uptake and transport, nitrogen degradation and Zn resistance were also observed. Bradyrhizobium, Nitrospira, Steroidobacter, and Luteitalea might play important roles in regulating C, N, P cycling and heavy metal resistance. This study revealed the adjustment mechanisms of microbial heavy metals resistance and ecological functions under heavy metal pollution and identified the primary host microorganisms.

Historical Lead Contamination Linked to Atmospheric Deposition is Associated With Declines in Ectomycorrhizal Diversity and Shifts in Fungal Community Composition

Ectomycorrhizal and saprotrophic fungi respond differently to changing edaphic conditions caused by atmospheric deposition. Within each guild, responses can vary significantly, reflecting the diversity of species and their specific adaptations to environmental changes. Metal contaminants are often deposited onto earth's surface through atmospheric deposition, yet few studies have assessed the relationship between soil metal contamination and fungal communities. The goal of this study was to understand how soil metal contamination and other edaphic factors vary across the spruce-fir ecosystem in the Southern Appalachians and influence fungal diversity and function. Here, we characterize soil fungal communities using high-throughput sequencing of the ITS2 gene region and found that higher soil lead (Pb) concentrations were associated with lower fungal diversity. Ectomycorrhizal fungi were less diverse (specifically hydrophilic ectomycorrhizal functional types) at plots with elevated soil Pb concentrations, while saprotrophic fungi were less diverse at plots with elevated soil carbon:nitrogen ratios. Fungal community composition was significantly influenced by pH, Pb, and spatial factors. This study identifies important relationships between fungal diversity and soil Pb concentrations and indicates variable responses of genera within well-defined ecological guilds. Our work highlights the need to characterize poorly understood taxonomic groups of fungi and their function prior to further environmental degradation.

Evaluation of soil additives for stabilizing cadmium-contaminated paddy soil and its effect on the soil bacterial community

Given the significant contribution of contaminated rice to higher dietary Cd intake, agricultural scientists are concerned about reducing Cd contamination of paddy soils. A pot experiment was conducted to evaluate the influence of different soil additives (biochar, Fe-biochar, oyster shell, zeolite, yirang, and sepiolite) on Cd bioavailability and bacterial community in paddy soils. Application of 1% and 2% (w/w) soil additives significantly (p < 0.05) increased soil pH by 0.54-1.92 units and reduced DTPA-extractable Cd by 32, 29-60.84%, with biochar and oyster shell treatments having the highest effects. After adding soil additives, the geochemical fraction of Cd partially shifted to a more stable form, with the exchangeable fraction decreasing by 29.54-49.88% and the residual fraction increasing by 48.55-69.44%. The biochar and oyster shell treatments showed the greatest effectiveness of Cd stabilization, with the DTPA-extractable Cd content decreasing by 48.50-53.40% and 58.3-60.42%, respectively. Biochar and oyster shell treatments also significantly increased bacterial community diversity (p < 0.05), specifically increasing the relative abundance of Proteobacteria and Firmicutes while decreasing the abundance of Acidobacteria. The RDA analysis revealed that Cd bioavailability, pH, SOM, and CEC were the most influential factors on the soil bacterial community. The results of this study suggest that the use of biochar and oyster shells has the potential to minimize Cd bioavailability and improve the microecosystem of Cd-contaminated rice soils.

Analysis of heavy metal tolerance and genomics in an indigenous Kurthia strain from Kulik River reveals multi-metal resistance and dominance of selection pressure on codon usage patterns

Heavy metal(loid) contamination poses significant risks to biological entities and the ecosystem. Many metal(loid)-resistant bacteria have been isolated from different environmental sites, but still no work has described multi-metal resistant Kurthia sp. In this study, an indigenous Kurthia strain isolated from the surface water of River Kulik was studied to determine its level of tolerance to various metal(loid)s. This study aimed to isolate, characterize and determine the growth kinetics and efficiency of Kurthia gibsonii strain M6 to remove and bioaccumulate As(V), Ni and Pb in vitro. This study also aimed to sequence the whole genome of the bacterium, identify metal resistance genes and analyze the codon usage patterns and factors that affect the codon usage bias of these genes. The bacterium showed elevated resistance to As(V), Pb, Ni and Zn. Under metal(loid) stressed conditions, live cells of Kurthia strain M6 bioaccumulated 212.74, 91.51 and 40.38 mg g-1 of As(V), Pb and Ni, respectively. The removal efficiency was 97%, 69.15% and 25.88% for Pb, Ni and As(V), respectively. Genome analysis revealed the existence of different genes conferring heavy metal resistance. A comprehensive analysis of codon usage patterns for metal resistance genes depicted the predominance of selection pressure as a prime force influencing codon usage patterns. This is the first time a multi-metal resistant K. gibsonii strain has been systematically studied regarding its heavy metal resistance biology. These findings will provide insights into the metal resistance mechanisms of the genus Kurthia and assist in devising new strategies for the bioremediation of metal-polluted environments.

Groundwater Contamination: Study on the Distribution and Mobility of Metals and Metalloids in Soil and Rocks

This study investigates the distribution and mobility of metals and metalloids (M&Ms) in soils, rocks, and groundwater within the geologically complex southwestern region of Sicily. The study aims to highlight how natural sources, like rocks and soils, can release elements potentially harmful to human health. It underlines their dual role as both natural reservoirs and active sources of M&M release, driven by leaching processes influenced by physicochemical factors such as pH and redox potential (Eh). Lithological characteristics significantly influence the retention and release of elements, with clay-rich formations exhibiting higher immobilization capacity. However, environmental parameter variations can enhance element mobilization, increasing bioavailability and the risk of groundwater contamination. Water quality analyses reveal regulatory exceedances for As, B, Ni, and Be, underscoring potential health and ecological risks. Concurrently, microbiological investigations identify diverse microbial communities capable of altering the oxidative states of specific elements through oxidation and reduction processes, further influencing their mobility. This study underscores the importance of understanding natural sources of M&Ms and their interactions with geochemical and microbiological processes for effective environmental risk assessment. The findings provide a foundation for developing integrated and sustainable water resource management strategies to mitigate contamination risks and safeguard ecosystems and public health.

Effects of Illegal Solid Waste Dumping on the Structure of Soil Bacterial Communities: A Case Study in China

Illegal solid waste dumping is a significant factor contributing to environmental damage. In this study, 16S rRNA gene sequencing technology was used for the identification and assessment of environmental damage in an illegal dumping area in China, with the aim of confirming environmental damage through analyzing changes in the soil bacterial communities across slag, sewage sludge, and non-contaminated areas. The results indicate that the diversity of soil bacteria decreases with an increase in the degree of pollution. The illegal dumping of slag resulted in an increase in the relative abundance of Firmicutes and a decrease in the relative abundance of Acidobacteriota. Additionally, illegal dumping of sewage sludge resulted in an increase in the relative abundance of Proteobacteria and a decrease in the relative abundance of Acidobacteriota. The contents of Ni and Be in slag and Cu, Pb, and Cd in sewage sludge were key factors affecting bacterial community composition. The results reveal the effects of heavy metal pollution on the soil bacterial community structure and its environmental driving factors, thus expanding understanding in the context of management of the environmental damage caused by illegal dumping, as well as providing a perspective on the changes in the soil bacterial community, allowing for environmental damage confirmation.

Exogenously Applied Triacontanol Mitigates Cadmium Toxicity in Vigna radiata L. by Optimizing Growth, Nutritional Orchestration, and Metal Accumulation

Cadmium (Cd) is one of the foremost phytotoxic elements. Its proportion in agricultural soil is increasing critically due to anthropogenic activities. Cd stress is a major crop production threat affecting food security globally. Triacontanol (TRIA) is a phytohormone that promotes growth, development, and metabolic processes in plants. The current study explicates the mitigation of Cd toxicity in Vigna radiata L. (mung bean) seedlings through the application of TRIA by a seed priming technique under Cd stress. The role of TRIA in improving metabolic processes to promote Vigna radiata (mung bean, green gram) vegetative growth and performance under both stressed and unstressed conditions was examined during this study. To accomplish this, three doses of TRIA (10, 20, and 30 µmol L-1) were used to pretreat V. radiata seeds before they were allowed to grow for 40 days in soil contaminated with 20 mg kg-1 Cd. Cd stress lowered seed germination, morphological growth, and biomass in V. radiata plants. The maximum root and shoot lengths, fresh and dry weights of roots, and shoot and seed germination rates were recorded for TRIA2 compared with those of TRIA1 and TRIA3 under Cd stress. In Cd-stressed V. radiata plants, TRIA2 increased the content of chlorophyll a (2.1-fold) and b (3.1-fold), carotenoid (4.3-fold), total chlorophyll (3.1-fold), and gas exchange attributes, such as the photosynthetic rate (2.9-fold), stomatal conductance (6.0-fold), and transpiration rate (3.5-fold), compared with those in plants treated with only Cd. TRIA seed priming increased nutrient uptake (K1+, Na1+, Mg2+, and Zn2+), total phenolic content, total soluble protein content, and DPPH (2,2-diphenyl-1-picrylhydrazyl) activity. Additionally, TRIA2 significantly reduced the quantity of Cd in the plants (3.0-fold) and increased the metal tolerance index (6.6-fold) in plants contrasted with those in the Cd-treated plants. However, TRIA2 promoted plant growth and biomass production by lowering Cd-induced stress through modifying the plant antioxidant machinery and reducing oxidative stress. The improved yield characteristics of V. radiata seedlings treated with TRIA suggest that exogenous TRIA may be used to increase plant tolerance to Cd stress.

Vermicompost application improves leaf physiological activity, 2-acetyl-1-pyrroline, and grain yield of fragrant rice through efficient nitrogen assimilation under Cd stress

Cadmium (Cd) pollution in arable soils and its accumulation in rice plants have become a global concern because of their harmful effects on crop yield and human health. The in-situ stabilization method which involves the application of organic amendments such as vermicompost (VC), is frequently utilized for the remediation of Cd-contaminated soils. This study investigated the effects of VC on the soil chemical properties and the physio-biochemical functions of fragrant rice, as well as nitrogen (N) metabolism and assimilatory enzyme activities, 2-acetyl-1-pyrroline (2AP) content in rice grains, and the grain yields of fragrant rice cultivars, i.e., Xiangyaxiangzhan (XGZ) and.Meixiangzhan-2 (MXZ-2) under Cd stress condition. Four doses of VC (.VC1 = 0, VC2 = 3 t. ha-1, VC3 = 4 t ha-1, and VC4 = 6 t ha-1) and two levels of Cd (0 and 25 mg Cd kg-1) were used in this study. Our results showed that VC supplementation significantly (p < 0.05) improved soil characteristics, including soil organic carbon, available N, total N, phosphorus (P), and potassium (K). Furthermore, VC enhanced plant physiological and biochemical attributes in fragrant rice, such as net photosynthetic rate (Pn), nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate oxoglutarate aminotransferase (GOGAT) enzyme activities, protein contents, amino acid, and 2-acetyl-1-pyrroline (2AP) contents under Cd stress condition. Specifically, the VC-amended treatment, Cd2 + VC3, led to an 86.75% increase in Pn and 2AP, and a 60.05% and 77.55% increase in grain yield for MXZ-2 and XGZ cultivars, respectively, compared to Cd-only treated plants (Cd2 + VC1). In addition, VC application significantly (p < 0.05) decreased the Cd uptake and accumulation in rice plants. The correlation analysis indicated that leaf physiological activity and biochemical traits are strongly correlated with soil qualitative traits, suggesting that improved soil health leads to enhanced leaf physiological activity, N metabolism, grain 2AP content, and grain yields. Among the treatments, Cd2 + VC3 showed the best performance in terms of soil fertility and rice quality and production. Consequently, our study indicates that using VC in soils may benefit rice growers by improving soil fertility and supporting sustainable rice productivity and quality in soils contaminated with Cd.

Synergistic biochar and Serratia marcescens tackle toxic metal contamination: A multifaceted machine learning approach

Metal contamination in soil poses environmental and health risks requiring effective remediation strategies. This study introduces an innovative approach of synergistically employing biochar and bacterial inoculum of Serratia marcescens to address toxic metal (TM) contamination. Physicochemical, enzymatic, and microbial analyses were conducted, employing integrated biomarker response (IBR) and machine-learning approaches for toxicity estimation. The combined application significantly reduced the Cd, Cr, and Pb concentrations by 71.6, 31.2, and 57.1%, respectively, while the Cu concentration increased by 85% in the individual Serratia marcescens treatment. Biochar enhanced microbial biomass by 33-44% after 25 days. Noteworthy physicochemical improvements included a 44.7% increase in organic content and a decrease in pH and electrical conductivity. The K⁺ and Ca2⁺ concentrations increased by 196.9 and 21.6%, respectively, while the Mg2⁺ content decreased by 86.4%. Network analysis revealed intricate relationships, displaying direct and indirect negative correlations between metals and soil physicochemical parameters. The IBR index values indicated effective mitigation of TM toxicity in Serratia marcescens and biochar with individual and combined treatments. Binary classification demonstrated high sensitivity (80.1%) and specificity (80.5%) in identifying TM-contaminated soil. These findings indicate significant biochar- and Serratia marcescens-induced impacts on toxic metal availability, physicochemical properties, and enzymatic activities in metal-contaminated soil, suggesting that blending soil with biochar and microorganisms is an effective remediation strategy.

Cenococcum geophilum impedes cadmium toxicity in Pinus massoniana by modulating nitrogen metabolism

Nitrogen (N) is of great significance to the absorption, distribution and detoxification of cadmium (Cd). Ectomycorrhizal fungi (EMF) are able to affect the key processes of plant N uptake to resist Cd stress, while the mechanism is still unclear. Therefore, we explored potential strategies of Cenococcum geophilum (C. geophilum) symbiosis to alleviate Cd stress in Pinus massoniana (P. massoniana) from the perspective of plant N metabolism and soil N transformation. The results showed that inoculation of C. geophilum significantly increased the activities of NR, NiR and GS in the shoots and roots of P. massoniana, thereby promoting the assimilation of NO3- and NH4+ into amino acids. Moreover, C. geophilum promoted soil urease and protease activities, but decreased soil NH4+ content, indicating that C. geophilum might increase plant uptake of soil inorganic N. qRT-PCR results showed that C3 symbiosis significantly up-regulated the expression of genes encoding functions involved in NH4+ uptake (AMT3;1), NO3- uptake (NRT2.1, NRT2.4, NRT2.9), as well as Cd resistance (ABCC1 and ABCC2), meanwhile down-regulated the expression of NRT7.3, Cd transporter genes (HMA2 and NRAMP3) in the roots of P. massoniana seedlings. These results demonstrated that C. geophilum was able to alleviate Cd stress by increasing the absorption and assimilation of inorganic N in plants and inhibiting the transport of Cd from roots to shoots, which provided new insights into how EMF improved host resistance to abiotic stress.

Inoculation with Bacillus thuringiensis reduces uptake and translocation of Pb/Cd in soil-wheat system: A life cycle study

Microbial inoculation is an important strategy to reduce the supply of heavy metals (HMs) in soil-crop systems. However, the mechanisms of microbial inoculation for the availability of HMs in soil and their accumulation/transfer in crops remain unclear. Here, the inhibitory effect of inoculation with Bacillus thuringiensis on the migration and accumulation of Pb/Cd in the soil-wheat system during the whole growth period was investigated by pot experiments. The results showed that inoculation with Bacillus thuringiensis increased soil pH and available nutrients (including carbon, nitrogen, and phosphorus), and enhanced the activities of nutrient-acquiring enzymes. Dominance analysis showed that dissolved organic matter (DOM) is the key factor affecting the availability of HMs. The content of colored spectral clusters and humification characteristics of DOM were significantly improved by inoculation, which is conducive to reducing the availability of Pb/Cd, especially during the flowering stage, the decrease was 12.8 %. Inoculation decreased Pb/Cd accumulation in the shoot and the transfer from root to shoot, with the greatest decreases at the jointing and seedling stages (27.0-34.1 % and 6.9-11.8 %), respectively. At the maturity stage, inoculation reduced the Pb/Cd accumulation in grain (12.9-14.7 %) and human health risk (4.1-13.2 %). The results of Pearson correlation analysis showed that the availability of Pb/Cd was positively correlated with the humification of DOM. Least square path model analysis showed that Bacillus thuringiensis could significantly reduce Pb/Cd accumulation in the grain and human health risks by regulating DOM spectral characteristics, the availability of HMs in soil and metals accumulation/transport in wheat at different growth stages. This study revealed the inhibition mechanism of Bacillus thuringiensis on migration of Pb/Cd in a soil-wheat system from a viewpoint of a full life cycle, which offers a valuable reference for the in-situ remediation of HM-contaminated soil and the safe production of food crops in field.

Molecular and eco-physiological responses of soil-borne lead (Pb2+)-resistant bacteria for bioremediation and plant growth promotion under lead stress

Lead (Pb) is the 2nd known portentous hazardous substance after arsenic (As). Being highly noxious, widespread, non-biodegradable, prolonged environmental presence, and increasing accumulation, particularly in arable land, Pb pollution has become a serious global health concern requiring urgent remediation. Soil-borne, indigenous microbes from Pb-polluted sites have evolved diverse resistance strategies, involving biosorption, bioprecipitation, biomineralization, biotransformation, and efflux mechanisms, under continuous exposure to Pb in human-impacted surroundings. These strategies employ a wide range of functional bioligands to capture Pb and render it inaccessible for leaching. Recent breakthroughs in molecular technology and understanding of lead resistance mechanisms offer the potential for utilizing microbes as biological tools in environmental risk assessment. Leveraging the specific affinity and sensitivity of bacterial regulators to Pb2+ ions, numerous lead biosensors have been designed and deployed worldwide to monitor Pb bioavailability in contaminated sites, even at trace levels. Besides, the ongoing degradation of croplands due to Pb pollution poses a significant challenge to meet the escalating global food demands. The accumulation of Pb in plant tissues jeopardizes both food safety and security while severely impacting plant growth. Exploring Pb-resistant plant growth-promoting rhizobacteria (PGPR) presents a promising sustainable approach to agricultural practices. The active associations of PGPR with host plants have shown enhancements in plant biomass and stress alleviation under Pb influence. They thus serve a dual purpose for plants grown in Pb-contaminated areas. This review aims to offer a comprehensive understanding of the role played by Pb-resistant soil-borne indigenous bacteria in expediting bioremediation and improving the growth of Pb-challenged plants essential for potential field application, thus broadening prospects for future research and development.

Ecological and human health risk associated with heavy metals (HMs) contaminant sourced from petroleum refinery oily sludge

The environmental and human health risk of heavy metals (HMs) in petroleum based oily sludge (OS) varies depending upon the source of origin of the crude oil and treatment processes practiced at the refineries. Consequently, the present study explores the potential risk associated with HMs of OS obtained from different refinery sites to the environment and human health. The results showed that HMs (Cu, Ni, Zn, Mn) present in OS surpasses the permissible limit of WHO guidelines except for Cr. Additionally, the Igeo value (grade 3-6), Ef (2.48-121.4), PLI (5.12-22.65), Cd (32.48-204.76) and PERI (grade 1-5) confirmed the high level of HMs contamination into the OS and its risk to the environment. Besides, the hazard index (HI) and the total carcinogenic risk (TCR) for HMs show substantial risk to both adult and children health. Likewise, the G-mean enzyme index and potential soil enzyme risk index (PSERI) of the OS showed a high risk to soil biological properties. Furthermore, statistical analysis confirmed the heterogeneity in properties of the OS and its potential impact on the soil ecosystem arising from different sites. Finally, the study unveils a novel perspective on the environmental and human health consequences associated with the OS.

Plants' molecular behavior to heavy metals: from criticality to toxicity

The contamination of soil and water with high levels of heavy metals (HMs) has emerged as a significant obstacle to agricultural productivity and overall crop quality. Certain HMs, although serving as essential micronutrients, are required in smaller quantities for plant growth. However, when present in higher concentrations, they become very toxic. Several studies have shown that to balance out the harmful effects of HMs, complex systems are needed at the molecular, physiological, biochemical, cellular, tissue, and whole plant levels. This could lead to more crops being grown. Our review focused on HMs' resources, occurrences, and agricultural implications. This review will also look at how plants react to HMs and how they affect seed performance as well as the benefits that HMs provide for plants. Furthermore, the review examines HMs' transport genes in plants and their molecular, biochemical, and metabolic responses to HMs. We have also examined the obstacles and potential for HMs in plants and their management strategies.

Multi-scale analysis of acidophilic microbial consortium biofilm's tolerance of lithium and cobalt ions in bioleaching

Metal ions stress will inhibit the oxidation capacity of iron and sulfur of an acidophilic microbial consortium (AMC), which leads to reduced bioleaching efficiency. This work explored the impacts of Li+ and Co2+ on the composition and function of AMC biofilms with a multi-scale approach. At the reactor scale, the results indicated that the oxidative activity, the adsorption capacity, and the biofilm formation ability of AMC on pyrite surfaces decreased under 500 mM Li+ and 500 mM Co2+. At the biofilm scale, the electrochemical measurements showed that Li+ and Co2+ inhibited the charge transfer between the pyrite working electrode and the biofilm, and decreased the corrosion current density of the pyrite working electrode. At the cell scale, the content of proteins in extracellular polymers substrate (EPS) increased as the concentrations of metal ions increased. Moreover, the adsorption capacity of EPS for Li+ and Co2+ increased. At the microbial consortium scale, a BugBase phenotype analysis showed that under 500 mM Li+ and 500 mM Co2+, the antioxidant stress capacity and the content of mobile gene elements in AMC increased. The results in this work can provide useful data and theoretical support for the regulation strategy of the bioleaching of spent lithium-ion batteries to recover valuable metals.

Ecotoxicity of thallium to two soil animal species with different niches and modification by organic materials

Soil thallium (Tl) contamination is of major public concern but little is known about soil Tl ecological toxicity or potential ecological remediation strategies. Here, two soil animal species with different ecological niches, Folsomia candida and Enchytraeus crypticus, were used to test Tl toxicity and modification by exogenous organic materials (i.e. maize straw and biochar). The endpoints of Tl ecotoxicity to F. candida and E. crypticus were studied at two biological levels, i.e., the individual (body Tl concentrations) and the population (survival, reproduction, and growth). Thallium concentrations in F. candida and E. crypticus increased with increasing soil Tl concentration, and their survival and reproduction rates decreased with increasing soil Tl concentration. The LC50 value of Tl effects on F. candida mortality (28 d) was 24.0 mg kg-1 and the EC50 value of reproduction inhibition was 6.51 mg kg-1. The corresponding values were 4.15 mg kg-1 and 2.31 mg kg-1 respectively for E. crypticus showing higher sensitivity to soil Tl than F. candida. These effective values are comparable to or much lower than the environmental Tl concentrations in field soils, suggesting high potential ecological risk. Both biochar and straw can decrease animal body Tl concentrations in different ways, i.e. reducing Tl availability or offering clean food sources, and addition of exogenous organic materials clearly mitigated Tl ecotoxicity in highly polluted soil. The results highlight the potential Tl ecological risk to soil animals and the potential use of organic materials to control the toxicity.

Trace metals coupled with plasticisers in microplastics strengthen the denitrification function of the soil microbiome in the Qinghai Tibetan Plateau

Due to the lack of research on the co-effects of microplastics and trace metals in the environment on nitrogen cycling-related functional microorganisms, the occurrence of microplastics and one of their plasticisers, phthalate esters, as well as trace metals, were determined in soils and river sediments in the Qinghai-Tibet Plateau. Relationship between microplastics and phthalate esters in the area was determined; the co-effects of these potentially toxic materials, and key factors and pathways affecting nitrogen functions were further explored. Significant correlations between fibre- and film-shaped microplastics and phthalate esters were detected in the soils from the plateau. Copper, lead, cadmium and di-n-octyl phthalate detected significantly affected nitrogen cycling-related functional microorganisms. The co-existence of di-n-octyl phthalate and copper in soils synergistically stimulated the expression of denitrification microorganisms nirS gene and "nitrate_reduction". Additionally, di-n-octyl phthalate and dimethyl phthalate more significantly affected the variation of nitrogen cycling-related functional genes than the number of microplastics. In a dimethyl phthalate- and cadmium-polluted area, nitrogen cycling-related functional genes, especially nirK gene, were more sensitive and stressed. Overall, phthalate esters originated from microplastics play a key role in nitrogen cycling-related functions than microplastics themselves, moreover, the synergy between di-n-octyl phthalate and copper strengthen the expression of denitrification functions.

Land use/cover drive functional patterns of bacterial communities in sediments of a subtropical river, China

The bacterial community in sediment serves as an important indicator for assessing the environmental health of river ecosystems. However, the response of bacterial community structure and function in river basin sediment to different land use/cover changes has not been widely studied. To characterize changes in the structure, composition, and function of bacterial communities under different types of land use/cover, we studied the bacterial communities and physicochemical properties of the surface sediments of rivers. Surface sediment in cropland and built-up areas was moderately polluted with cadmium and had high nitrogen and phosphorus levels, which disrupted the stability of bacterial communities. Significant differences in the α-diversity of bacterial communities were observed among different types of land use/cover. Bacterial α-diversity and energy sources were greater in woodlands than in cropland and built-up areas. The functional patterns of bacterial communities were shown that phosphorus levels and abundances of pathogenic bacteria and parasites were higher in cropland than in the other land use/cover types; Urban activities have resulted in the loss of the denitrification function and the accumulation of nitrogen in built-up areas, and bacteria in forested and agricultural areas play an important role in nitrogen degradation. Differences in heavy metal and nutrient inputs driven by land use/cover result in variation in the composition, structure, and function of bacterial communities.

Ecotoxicological effects of polyethylene microplastics and lead (Pb) on the biomass, activity, and community diversity of soil microbes

Microplastics and heavy metals are ubiquitous and persistent contaminants that are widely distributed worldwide, yet little is known about the effects of their interaction on soil ecosystems. A soil incubation experiment was conducted to investigate the individual and combined effects of polyethylene microplastics (PE-MPs) and lead (Pb) on soil enzymatic activities, microbial biomass, respiration rate, and community diversity. The results indicate that the presence of PE-MPs notably reduced soil pH and elevated soil Pb bioavailability, potentially exacerbated the combined toxicity on the biogeochemical cycles of soil nutrients, microbial biomass carbon and nitrogen, and the activities of soil urease, sucrase, and alkaline phosphatase. Soil CO2 emissions increased by 7.9% with PE-MPs alone, decreased by 46.3% with single Pb, and reduced by 69.4% with PE-MPs and Pb co-exposure, compared to uncontaminated soils. Specifically, the presence of PE-MPs and Pb, individually and in combination, facilitated the soil metabolic quotient, leading to reduced microbial metabolic efficiency. Moreover, the addition of Pb and PE-MPs modified the composition of the microbial community, leading to the enrichment of specific taxa. Tax4Fun analysis showed the effects of Pb, PE-MPs and their combination on the biogeochemical processes and ecological functions of microbes were mainly by altering amino acid metabolism, carbohydrate metabolism, membrane transport, and signal transduction. These findings offer valuable insights into the ecotoxicological effects of combined PE-MPs and Pb on soil microbial dynamics, reveals key assembly mechanisms and environmental drivers, and highlights the potential threat of MPs and heavy metals to the multifunctionality of soil ecosystems.

Sensitivity of microbial bioindicators in assessing metal immobilization success in smelter-impacted soils

While plant toxicity reduction remains the primary metric for judging the success of metal immobilization in soil, the suitability of microorganisms as universal indicators of its effectiveness in various contaminated soils remains a point of contention. This study assessed the sensitivity of microbial bioindicators in monitoring metal immobilization success in smelter-impacted soils. It compared plants and microorganisms as indicators of the efficiency of natural Fe-Mn nodules from the Gulf of Finland in immobilizing metals in soils contaminated by a Ni/Cu smelter, on the Kola Peninsula, Murmansk region, Russia. Perennial ryegrass (Lolium perenne) was grown on nodule-amended and control soils. Plant responses in the smelter-impacted soils proved to be sensitive and robust indicators of successful metal immobilization. However, microbial responses exhibited a more complex story. Despite the observed reductions in soluble metal concentrations, shoot metal contents in ryegrass, and significant improvements in plant growth, certain microbial bioindicators were unresponsive to metal immobilization success brought about by the addition of Fe-Mn nodules. Among microbial bioindicators studied, community-level physiological profiling, microbial biomass carbon, and basal respiration were sensitive indicators of metal immobilization success, whereas the number of saprotrophic, oligotrophic, and Fe-oxidizing bacteria and fungi, the biomass of bacteria and fungi, and enzymatic activity were less robust indicators. Interestingly, the correlations between different microbial responses measured were weak or even negative. Some microbial responses also exhibited negative correlations with plant biomass. These findings underscore the need for further research on comparative evaluations of plants and microorganisms as reliable indicators of metal immobilization efficacy in polluted environments.

Recalcification stabilizes cadmium but magnifies phosphorus limitation in wastewater-irrigated calcareous soil

Long-term wastewater irrigation leads to the loss of calcium carbonate (CaCO3) in the tillage layer of calcareous land, which irreversibly damages the soil's ability to retain cadmium (Cd). In this study, we selected calcareous agricultural soil irrigated with wastewater for over 50 years to examine the recalcification effects of sugar beet factory lime (SBFL) at doses of 0%, 2.5%, 5%, and 10%. We found that SBFL promoted Cd transformation in the soil from active exchangeable species to more stable carbonate-bonded and residual species, which the X-ray diffraction patterns also confirmed results that CdSO4 reduced while CdS and CaCdCO3 increased. Correspondingly, the soil bioavailable Cd concentration was significantly reduced by 65.6-84.7%. The Cd concentrations in maize roots and shoots were significantly reduced by 11.7-50.6% and 13.0-70.0%, respectively, thereby promoting maize growth. Nevertheless, SBFL also increased the proportion of plant-unavailable phosphorus (P) in Ca8-P and Ca10-P by 4.3-13.0% and 10.7-25.9%, respectively, reducing the plant-available P (Olsen P) content by 5.2-22.1%. Consequently, soil P-acquiring associated enzyme (alkaline phosphatase) activity and microbial (Proteobacteria, Bacteroidota, and Actinobacteria) community abundance significantly increased. Our findings showed that adding SBFL to wastewater-irrigated calcareous soil stabilized Cd, but exacerbated P limitation. Therefore, it is necessary to alleviate P limitations in the practice of recalcifying degraded calcareous land.

Heavy metals in a typical industrial area-groundwater system: Spatial distribution, microbial response and ecological risk

The environmental burden due to industrial activities has been quite observable in the last few years, with heavy metals (HMs) like lead, cadmium, and arsenic inducing serious perturbations to the microbial ecosystem of groundwater. Studies carried out in North China, a region known for interconnection of industrial and groundwater systems, sought to explore the natural mechanisms of adaptation of microbes to groundwater contamination. The results showed that heavy metals permeate from surface increased the diversity and abundance of microbial communities in groundwater, producing an average decrease of 40.84% and 34.62% in the relative abundance of Bacteroidetes and Proteobacteria in groundwater, respectively. Meanwhile, the key environmental factors driving the evolution of microbial communities shift from groundwater nutrients to heavy metals, which explained 50.80% of the change in the microbial community composition. Microbial indicators are more sensitive to HMs pollution and could accurately identify industrial area where HMs permeation occurred and other extraneous pollutants. The phylum Bacteroidetes could act as appropriate indicators for the identification. Significant genera that were identified, being Mesorhizobium, Clostridium, Bacillus and Mucilaginibacter, were found to play important roles in the microbial network in terms of the potential to assist in groundwater clean-up. Notably, pollution from heavy metals has diminished the effectiveness and resilience of microbial communities in groundwater, thereby heightening the susceptibility of these normally stable microbial ecosystems. These findings offer new perspectives on how to monitor and detect groundwater pollution, and provide scientific guidance for developing suitable remediation methods for groundwater contaminated with heavy metals. Future research is essential explore the application of metal-tolerant or resistant bacteria in bioremediation strategies to rehabilitate groundwater systems contaminated by HMs.

Heavy metals and nutrients mediate the distribution of soil microbial community in a typical contaminated farmland of South China

The effects of heavy metals on soil microbial communities have been extensively investigated, whereas the combined effects of heavy metals and nutrients on soil microbial communities and their interactions are rarely understood. In this study, we investigated the distribution patterns of heavy metals, nutrients and microbial communities in a typical contaminated farmland and explored their interaction mechanisms. The results showed that Cd and Pb were the main pollutants in this area, which mainly came from the smelter. Canonical correspondence analysis and variance decomposition analysis showed that the heavy metals played a more important role in restraining the microbial community structure of soils than other soil properties. Soil Cd, Pb, pH and available K content were the most important environmental factors affecting the microbial community structures in soil. Major Cd tolerant bacteria and fungi were detected including Actinobacteriota, Gemmatimonadota, Entorrhizomycota and Mortierellomycota. The analyses of molecular ecological networks showed that there were 84.1 % of negative correlations among microorganisms. Cd could regulate the abundance of key nodes in Cd-tolerant network modules, and these key nodes could improve the adaptability of the whole module to heavy metals through competition with other microorganisms. This study provides insights into the ecological effects of heavy metals and nutrients on soil microbial communities and will help to develop the bio-remediation technologies for contaminated soils.

Vermicompost Supply Enhances Fragrant-Rice Yield by Improving Soil Fertility and Eukaryotic Microbial Community Composition under Environmental Stress Conditions

Heavy-metal contamination in agricultural soil, particularly of cadmium (Cd), poses serious threats to soil biodiversity, rice production, and food safety. Soil microbes improve soil fertility by regulating soil organic matter production, plant nutrient accumulation, and pollutant transformation. Addressing the impact of Cd toxicity on soil fungal community composition, soil health, and rice yield is urgently required for sustainable rice production. Vermicompost (VC) is an organic fertilizer that alleviates the toxic effects of Cd on soil microbial biodiversity and functionality and improves crop productivity sustainably. In the present study, we examined the effects of different doses of VC (i.e., 0, 3, and 6 tons ha-1) and levels of Cd stress (i.e., 0 and 25 mg Cd kg-1) on soil biochemical attributes, soil fungal community composition, and fragrant-rice grain yield. The results showed that the Cd toxicity significantly reduced soil fertility, eukaryotic microbial community composition and rice grain yield. However, the VC addition alleviated the Cd toxicity and significantly improved the soil fungal community; additionally, it enhanced the relative abundance of Ascomycota, Chlorophyta, Ciliophora, Basidiomycota, and Glomeromycta in Cd-contaminated soils. Moreover, the VC addition enhanced the soil's chemical attributes, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), and microbial biomass C and N, compared to non-VC treated soil under Cd toxicity conditions. Similarly, the VC application significantly increased rice grain yield and decreased the Cd uptake in rice. One possible explanation for the reduced Cd uptake in plants is that VC amendments influence the soil's biological properties, which ultimately reduces soil Cd bioavailability and subsequently influences the Cd uptake and accumulation in rice plants. RDA analysis determined that the leading fungal species were highly related to soil environmental attributes and microbial biomass C and N production. However, the relative abundance levels of Ascomycota, Basidiomycota, and Glomeromycta were strongly associated with soil environmental variables. Thus, the outcomes of this study reveal that the use of VC in Cd-contaminated soils could be useful for sustainable rice production and safe utilization of Cd-polluted soil.

Combined effect of zinc and cadmium ions on nitrification performance during the biological nitrogen removal of simulated livestock breeding wastewater

Zinc and cadmium ions are usually found in livestock breeding wastewater, and the mixed ions will have an impact on the biological nitrogen removal. Nitrification performance plays an important role in biological nitrogen removal. In order to investigate the combined effect of zinc and cadmium ions on nitrification performance and to reveal the interactions between zinc and cadmium ions, three concentration ratios of zinc and cadmium ions, as well as 18 different concentration gradients were designed with the direct equipartition ray and the dilution factor method. The effect of pollutants on the nitrification performance of biological nitrogen removal was analyzed by the nonlinear regression equation, and the concentration-addition model was conducted to probe into the relationship between the mixed pollutants and the nitrification performance. The results showed that the effect on nitrification performance increased significantly with the increase of reaction duration and pollutant concentration, which indicated that the effects are concentration-dependent and time-dependent. The concentration-addition model suggested that the interactions between zinc and cadmium ions with different concentration ratios were mainly antagonistic, and as the percentage of cadmium ions in the mixtures increased, the antagonism between the mixtures became stronger. This study will provide a relevant theoretical basis for the regulation of the ratios and concentrations of heavy metal ions during the biological treatment of livestock breeding wastewater.

Heavy metal induced shifts in microbial community composition and interactions with dissolved organic matter in coastal sediments

Heavy metals can impact the structure and function of coastal sediment. The dissolved organic matter (DOM) pool plays an important role in determining both the heavy metal toxicity and microbial community composition in coastal sediments. However, how heavy metals affect the interactions between microbial communities and DOM remains unclear. Here, we investigated the influence of heavy metals on the microbial community structure (including bacteria and archaea) and DOM composition in surface sediments of Beibu Gulf, China. Our results revealed firstly that chromium, zinc, cadmium, and lead were the heavy metals contributing to pollution in our studied area. Furthermore, the DOM chemical composition was distinctly different in the contaminated area from the uncontaminated area, characterized by a higher average O/C ratio and increased prevalence of carboxyl-rich alicyclic molecules (CRAM) and highly unsaturated compounds (HUC). This indicates that DOM in the contaminated area was more recalcitrant compared to the uncontaminated area. Except for differences in archaeal diversity between the two areas, there were no significant variations observed in the structure of archaea and bacteria, as well as the diversity of bacteria, across the two areas. Nevertheless, our co-occurrence network analysis revealed that the B2M28 and Euryarchaeota, dominating bacterial and archaeal groups in the contaminated area were strongly related to CRAM. The network analysis also unveiled correlations between active bacteria and elevated proportions of nitrogen-containing DOM molecules. In contrast, the archaea-DOM network exhibited strong associations with nitrogen- and sulfur-containing molecules. Collectively, these findings suggest that heavy metals indeed influence the interaction between microbial communities and DOM, potentially affecting the accumulation of recalcitrant compounds in coastal sediments.

Synergistic impact of bioavailable PHEs and alkalinity on microbial diversity and traits in agricultural soil adjacent to chromium-asbestos mines

Soil microbial communities undergo constant fluctuations, particularly in response to environmental factors. Although the deposition of toxic mine waste is recognized for introducing potentially hazardous elements (PHEs) into the soil, its specific impacts on microbial communities remain unclear. This study aims to explore the combined effects of soil alkalinity and bioavailable PHEs on microbial diversity and traits in agricultural soil adjacent to a chromium-asbestos mining area. By employing a comprehensive analysis, this study indicated that microbiological attributes were reduced in contaminated areas (zone 1), whereas both the levels of bioavailable PHEs (CrWs: 31.08 mg/kg, NiWs: 13.90 mg/kg) and alkalinity indices (CROSS, MCAR, MH) were significantly higher. The spatial distribution of soil alkalinity and bioavailable PHEs, primarily originating from chromium-asbestos mines, has been determined. This study also elucidates the negative relationship between soil stressors (Alkalinity and PHEs) and microbial activities (soil enzymatic activity, microbial respiration, and biomass carbon). The vector's length exhibited a notable difference between zone 1 (0.51) and zone 2 (0.32), indicating a substantial limitation on carbon (C). Also, the investigation of soil bacterial diversity unveiled notable disparities in the prevalence of microbial populations inside zone 1. Proteobacteria constituted 57.18% of the total population indicating a noteworthy prevalence in the contaminated soils. Finally, the random forest (RF) algorithm from machine learning was selected and proven to be a robust choice in Taylor diagrams for predicting the causative stressors responsible for the deterioration of soil microbial health. Therefore, this research offers insights into the health and resilience of soil microbial communities under synergistic stress conditions, which will aid environmentalists in planning future interventions and improving sustainable farming techniques.

Sources apportionments of heavy metal(loid)s in the farmland soils close to industrial parks: Integrated application of positive matrix factorization (PMF) and cadmium isotopic fractionation

Understanding the source identification and distribution of heavy metal(loid)s in soil is essential for risk management. The sources of heavy metal(loid)s in farmland soil, especially in areas with rapid economic development, were complicated and need to be explored urgently. This study combined geographic information system (GIS) mapping, positive matrix factorization (PMF) model and cadmium (Cd) isotope fingerprinting methods to identify heavy metal(loid) sources in a typical town in the economically developed Yangtze River Delta region of China. Cd, As, Cu, Zn, Pb, Ni and Co in different samples were detected. The results showed that Cd was the most severely contaminated element, with an exceedance rate of 78.0 %. GIS mapping results indicated that the hotspot area was located in the northeastern area with prolonged operational histories of electroplating and non-ferrous metal smelting industries. The PMF model analysis also identified emissions from smelting and electroplating enterprises as the main sources of Cd in the soil, counted for 49.28 %, followed by traffic (25.66 %) and agricultural (25.06 %) sources. Through further isotopic analysis, it was found that in soil samples near the industrial park, the contribution of electroplating and non-ferrous metal smelting enterprises to cadmium pollution was significantly higher than other regions. The integrated use of various methodologies allows for precise analysis of sources and input pathways, offering valuable insights for future pollution control and soil remediation endeavors.

Revealing soil microbial ecophysiological indicators in acidic environments laden with heavy metals via predictive modeling: Understanding the impacts of black diamond excavation

Appraising the activity of soil microbial community in relation to soil acidity and heavy metal (HM) content can help evaluate it's quality and health. Coal mining has been reported to mobilize locked HM in soil and induce acid mine drainage. In this study, agricultural soils around coal mining areas were studied and compared to baseline soils in order to comprehend the former's effect in downgrading soil quality. Acidity as well as HM fractions were significantly higher in the two contaminated zones as compared to baseline soils (p < 0.01). Moreover, self-organizing and geostatistical maps show a similar pattern of localization in metal availability and soil acidity thereby indicating a causal relationship. Sobol sensitivity, cluster, and principal component analyses were employed to enunciate the relationship between the various metal and acidity fractions with that of soil microbial properties. The results indicate a significant negative impact of metal bioavailability, and acidity on soil microbial activity. Lastly, Taylor diagrams were employed to predict soil microbial quality and health based on soil physicochemical inputs. The efficiency of several machine learning algorithms was tested to identify Random Forrest as the best model for prediction. Thus, the study imparts knowledge about soil pollution parameters, and acidity status thereby projecting soil quality which can be a pioneer in sustainable agricultural practices.

Sources, effects and present perspectives of heavy metals contamination: Soil, plants and human food chain

Heavy metal (HM) poisoning of agricultural soils poses a serious risk to plant life, human health, and global food supply. When HM levels in agricultural soils get to dangerous levels, it harms crop health and yield. Chromium (Cr), arsenic (As), nickel (Ni), cadmium (Cd), lead (Pb), mercury (Hg), zinc (Zn), and copper (Cu) are the main heavy metals. The environment contains these metals in varying degrees, such as in soil, food, water, and even the air. These substances damage plants and alter soil characteristics, which lowers crop yield. Crop types, growing circumstances, elemental toxicity, developmental stage, soil physical and chemical properties, and the presence and bioavailability of heavy metals (HMs) in the soil solution are some of the factors affecting the amount of HM toxicity in crops. By interfering with the normal structure and function of cellular components, HMs can impede various metabolic and developmental processes. Humans are exposed to numerous serious diseases by consuming these affected plant products. Exposure to certain metals can harm the kidneys, brain, intestines, lungs, liver, and other organs of the human body. This review assesses (1) contamination of heavy metals in soils through different sources, like anthropogenic and natural; (2) the effect on microorganisms and the chemical and physical properties of soil; (3) the effect on plants as well as crop production; and (4) entering the food chain and associated hazards to human health. Lastly, we identified certain research gaps and suggested further study. If people want to feel safe in their surroundings, there needs to be stringent regulation of the release of heavy metals into the environment.

Effects of sulfur nanoparticles on rhizosphere microbial community changes in oilseed rape plantation soil under mercury stress

In the present study, experiments were conducted to assess the influence of nanoscale sulfur in the microbial community structure of metallophytes in Hg-contaminated rhizosphere soil for planting rapeseed. The results showed that the richness and diversity of the rhizobacteria community decreased significantly under Hg stress, but increased slightly after SNPs addition, with a reduction in the loss of Hg-sensitive microorganisms. Moreover, all changes in the relative abundances of the top ten phyla influenced by Hg treatment were reverted when subjected to Hg + SNPs treatment, except for Myxococcota and Bacteroidota. Similarly, the top five genera, whose relative abundance decreased the most under Hg alone compared to CK, increased by 19.05%-54.66% under Hg + SNPs treatment compared with Hg alone. Furthermore, the relative abundance of Sphingomonas, as one of the dominant genera for both CK and Hg + SNPs treatment, was actively correlated with plant growth. Rhizobacteria, like Pedobacter and Massilia, were significantly decreased under Hg + SNPs and were positively linked to Hg accumulation in plants. This study suggested that SNPs could create a healthier soil microecological environment by reversing the effect of Hg on the relative abundance of microorganisms, thereby assisting microorganisms to remediate heavy metal-contaminated soil and reduce the stress of heavy metals on plants.

Substation of vermicompost mitigates Cd toxicity, improves rice yields and restores bacterial community in a Cd-contaminated soil in Southern China

Cadmium (Cd) contamination in agricultural soil is a global concern for soil health and food sustainability because it can cause Cd accumulation in cereal grains. An in-situ stabilizing technology (using organic amendments) has been widely used for Cd remediation in arable lands. Therefore, the current study examined the influence of vermicompost (VC) on soil biochemical traits, bacterial community diversity and composition, Cd uptake and accumulation in rice plants and grain yield in a Cd-contaminated soil during the late growing season in 2022. Different doses of VC (i.e., V1 = 0 t ha-1, V2 = 3 t ha-1 and V3 = 6 t ha-1) and two concentrations of Cd (i.e., Cd1 = 0 and Cd2 = 50 mg Cd Kg-1 were used. We performed high-throughput sequencing of 16S ribosomal RNA gene amplicons to characterize soil bacterial communities. The addition of VC considerably affected the diversity and composition of the soil bacterial community; and increased the relative abundance of phyla Chloroflexi, Proteobacteria, Acidobacteriota, Plantomycetota, Gemmatimonadota, Patescibacteria and Firmicute. In addition, VC application, particularly High VC treatment, exhibited the highest bacterial diversity and richness (i.e., Simpson, Shannon, ACE, and Chao 1 indexes) of all treatments. Similarly, the VC application increased the soil chemical traits, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), total potassium (TK), total phosphorous (TP) and enzyme activities (i.e., acid phosphatase, catalase, urease and invertase) compared to non-VC treated soil under Cd stress. The average increase in SOC, TN, AN, TK and TP were 5.75%, 41.15%, 18.51%, 12.31%, 25.45% and 29.67%, respectively, in the High VC treatment (Pos-Cd + VC3) compared with Cd stressed soil. Redundancy analysis revealed that the leading bacterial phyla were associated with SOC, AN, TN, TP and pH, although the relative abundance of Firmicutes, Proteobacteria, Bacteroidata, and Acidobacteria on a phylum basis and Actinobacteria, Gammaproteobacteria and Myxococcia on a class basis, were highly correlated with soil environmental factors. Moreover, the VC application counteracted the adverse effects of Cd on plants and significantly reduced the Cd uptake and accumulation in rice organs, such as roots, stem + leaves and grain under Cd stress conditions. Similarly, applying VC significantly increased the fragrant rice grain yield and yield traits under Cd toxicity. The correlation analysis showed that the increased soil quantities traits were crucial in obtaining high rice grain yield. Generally, the findings of this research demonstrate that the application of VC in paddy fields could be useful for growers in Southern China by sustainably enhancing soil functionality and crop production.

Heavy metal contamination impacts the structure and co-occurrence patterns of bacterial communities in agricultural soils

Heavy metal (HM) contamination caused by mining and smelting activities can be harmful to soil microbiota, which are highly sensitive to HM stress. Here, we explore the effects of HM contamination on the taxonomic composition, predicted function, and co-occurrence patterns of soil bacterial communities in two agricultural fields with contrasting levels of soil HMs (i.e., contaminated and uncontaminated natural areas). Our results indicate that HM contamination does not significantly influence soil bacterial α diversity but changes the bacterial community composition by enriching the phyla Gemmatimonadetes, Planctomycetes, and Parcubacteria and reducing the relative abundance of Actinobacteria. Our results further demonstrate that HM contamination can strengthen the complexity and modularity of the bacterial co-occurrence network but weaken positive interactions between keystone taxa, leading to the gradual disappearance of some taxa that originally played an important role in healthy soil, thereby possibly reducing the resistance of bacterial communities to HM toxicity. The predicted functions of bacterial communities are related to membrane transport, amino acid metabolism, energy metabolism, and carbohydrate metabolism. Among these, functions related to HM detoxification and antioxidation are enriched in uncontaminated soils, while HM contamination enriches functions related to metal resistance. This study demonstrated that microorganisms adapt to the stress of HM pollution by adjusting their composition and enhancing their network complexity and potential ecological functions.

Differences in soil bacterial community structure during the remediation of Cd-polluted cotton fields by biochar and biofertilizer in Xinjiang, China

Introduction

Heavy metal pollution is a major worldwide environmental problem. Many remediation techniques have been developed, these techniques have different performance in different environments.

Methods

In this study, soil sampling was conducted in multiple cotton fields in Xinjiang, China, and found that cadmium (Cd) was the most abundant soil heavy metal. Then, to find the most suitable technique for the remediation of Cd pollution in cotton fields, a two-year study was conducted to explore the effects of cotton straw-derived biochar (BC, 3%) and Bacillus-based biofertilizer (BF, 1.5%) on cotton Cd uptake and transport and soil microbial community structure under Cd exposure conditions (soil Cd contents: 1, 2, and 4 mg·kg-1).

Results

The results showed that the bioaccumulation coefficients (Cd content of cotton organs / soil available Cd content) of cotton roots, stems, leaves, and buds/bolls reduced by 15.93%, 14.41%, 23.53%, and 20.68%, respectively after the application of BC, and reduced by 16.83%, 17.15%, 22.21%, and 26.25%, respectively after the application of BF, compared with the control (no BC and BF). Besides, the application of BC and BF reduced the transport of Cd from soil to root system, and enhanced the diversity of soil bacterial communities (dominant species: Alphaproteobacteria and Actinobacteria) and the metabolic functions related to amino acid synthesis. It was worth noting that the differential species for BF group vs BC group including Alphaproteobacteria, Gemmatimonadetes, Bacilli, and Vicinamibacteria were associated with the enrichment and transport of Cd, especially the transport of Cd from cotton roots to stems.

Discussion

Therefore, the application of BC and BF changed the soil bacterial diversity in Cd-polluted cotton field, and then promoted the transport of Cd in cotton, ultimately improving soil quality. This study will provide a reference for the selection of soil heavy metal pollution remediation techniques in Xinjiang, China.

Microbial-driven mechanisms for the effects of heavy metals on soil organic carbon storage: A global analysis

Heavy metal (HM) enrichment is closely related to soil organic carbon (SOC) pools in terrestrial ecosystems, which are deeply intertwined with soil microbial processes. However, the influence of HMs on SOC remains contentious in terms of magnitude and direction. A global analysis of 155 publications was conducted to integrate the synergistic responses of SOC and microorganisms to HM enrichment. A significant increase of 13.6 % in SOC content was observed in soils exposed to HMs. The response of SOC to HMs primarily depends on soil properties and habitat conditions, particularly the initial SOC content, mean annual precipitation (MAP), initial soil pH, and mean annual temperature (MAT). The presence of HMs resulted in significant decreases in the activities of key soil enzymes, including 31.9 % for soil dehydrogenase, 24.8 % for β-glucosidase, 35.8 % for invertase, and 24.3 % for cellulose. HMs also exerted inhibitory effects on microbial biomass carbon (MBC) (26.6 %), microbial respiration (MR) (19.7 %), and the bacterial Shannon index (3.13 %) but elevated the microbial metabolic quotient (qCO2) (20.6 %). The HM enrichment-induced changes in SOC exhibited positive correlations with the response of MBC (r = 0.70, p < 0.01) and qCO2 (r = 0.50, p < 0.01), while it was negatively associated with β-glucosidase activity (r = 0.72, p < 0.01) and MR (r = 0.39, p < 0.01). These findings suggest that the increase in SOC storage is mainly attributable to the inhibition of soil enzymes and microorganisms under HM enrichment. Overall, this meta-analysis highlights the habitat-dependent responses of SOC to HM enrichment and provides a comprehensive evaluation of soil carbon dynamics in an HM-rich environment.

Effect of metal fractions on rice grain metal uptake and biological parameters in mica mines waste contaminated soils

Heavy metals from mica waste not only deteriorate the soil quality but also results in the uptake of metals in the crop. The present investigation was conducted to evaluate the effects of different fractions of metals on the uptake in rice, soil microbial and biochemical properties in mica waste-contaminated soils of Jharkhand, India. From each active mine, soil samples were randomly collected at distances of < 50 m (zone 1), 50-100 m (zone 2), and >100 m (zone 3). Sequential metal extraction was used to determine the fractions of different metals (nickel (Ni), cadmium (Cd), chromium (Cr) and lead (Pb)) including water-soluble (Ws) and exchangeable metals (Ex), carbonate-bound metals (CBD), Fe/Mn oxide (OXD) bound metals, organically bound metals (ORG), and residues (RS). The Ni, Cr, Cd and Pb in rice grain were 0.83±0.41, 0.41±0.19, 0.21±0.14 and 0.17±0.08 mg/kg respectively. From the variable importance plot of the random forest (RF) algorithm, the Ws fraction of Ni, Cr and Cd and Ex fraction of Pb was the most important predictor for rice grain metal content. Further, the partial dependence plots (PDP) give us an insight into the role of the two most important metal fractions on rice grain metal content. The microbial and enzyme activity was significantly and negatively correlated with Ws and Ex metal fractions, indicating that water-soluble and exchangeable fractions exert a strong inhibitory effect on the soil microbiological parameters and enzyme activities.

Metals stress on soil enzyme activities and herbs defense in the vicinity of high traffic roadways

This study has investigated the impact of vehicle sourced heavy metals (HMs) on soil enzyme activities and plants in and around high traffic roadways near the metropolitan area. In detail, the defense response against HM pollution was studied by considering the commonly available herbs around the roadside area namely Alternanthera paronychioides, Ageratum conyzoides, Spilanthes acmella, and Parthenium hysterophorus. The study reported that the HM concentrations such as Cu, Ni, Zn, Mn, and Cr were observed in the range of 6.05 ± 0.1 to 309 ± 0.5 mg/kg in roadside soil and 5.2 ± 0.1to 451 ± 4.2 mg/kg in the herbs collected from roadside area. The soil enzyme (urease, dehydrogenase, amylase, catalase, peroxidase, and polyphenol oxidase) activities decreased by 22.56 to 77.84% in roadside soil and lower IC50 values were observed for DPPH (2.32-4.67) and H2O2 (1.59-2.15) free radical scavenging activities in plants collected from roadside area. The flavonoid and phenolic content in plants collected from the roadside area ranges from 12.65 ± 0.2 to 15.75 ± 0.3 mg quercitin/g and 0.61 ± 0.04 to 1.16 ± 0.1 mg gallic acid/g respectively while in plant collected from the control areas ranges from 7.96 ± 0.1 to 11.24 ± 0.05 and 0.47 ± 0.01 to 0.61 ± 0.1. In addition, the contamination factor (CF) (1.53-11.92) and geo-accumulation index (Igeo) (0.031-2.99) in soil and bioaccumulation factor (BAF) (0.72-2.73) of Cu, Ni, Zn, Mn, and Crin plants indicated that the soil and plants growing along the highway were heavily contaminated with HM. Finally, Pearson correlation matrix confirmed the inhibition effect of HM on soil enzymatic activities and enzymatic defense of plants in response to the HM stress.

Performance evaluation, enzymatic activity change and metagenomic analysis of sequencing batch reactor under divalent zinc stress

Divalent zinc (Zn2+) are widely detected in domestic and industrial wastewater, and it is essential to evaluate the effect of Zn2+ on wastewater biological treatment process due to its bio-toxicity. In this study, the nitrogen removal rates and their corresponding enzymatic activities of sequencing batch reactor decreased with the increase of Zn2+ concentration. The Zn2+ accumulation in activated sludge caused significant antioxidant response, and the reactive oxygen species (ROS) production and antioxidant enzymatic activities were positively correlated with Zn2+ concentration. The presence of Zn2+ inhibited the metabolic pathways related to energy production and electron transport. The abundance decreases of nitrification and denitrification functional genes led to the deterioration of nitrogen removal performance under Zn2+ stress. The correlation analysis between functional gene modules and microbial genera revealed that Zoogloea had obvious Zn2+ resistance. This study can provide the insights into the influencing mechanism of Zn2+ on the biological nitrogen removal process.

Evaluation of copper-tolerant fungi isolated from Sarcheshmeh copper mine of Iran

Mycoremediation, a subset of bioremediation, is considered an advanced method to eliminate environmental contaminations. To identify tolerant fungi to copper contamination and study the related gene expression, sampling was carried out from the soil of "Sarcheshmeh Copper Mine," which is one of the biggest open-cast copper mines in the world. A total of 71 fungal isolates were obtained and purified. Afterward, the inhibitory effect of different concentrations (1000, 1500, 3500, 4000, and 5500 ppm) of copper sulfate on mycelial growth was evaluated. Results indicated that only 5500 ppm of copper sulfate inhibited fungal growth compared to the control. Based on the bioassay experiments, three isolates including S3-1, S3-21, and S1-7, which were able to grow on solid and broth medium containing 5500 ppm of copper sulfate at different pH conditions, were selected and identified using molecular approaches. Also, laccase and metallothionein gene expression has been assessed in these isolates. According to the molecular identification using ITS1-5.8S- ITS2 region, isolates S3-1 and S1-7 were identified as Pleurotus eryngii, and isolate S3-21 belonged to the genus Sarocladium. In addition, P. eryngii showed laccase gene expression reduction after 8 days of exposure to copper sulfate. While in the genus Sarocladium, it increased (almost 2 times) from 6 to 8 days. Besides, metallothionein gene expression has increased from 6 to 8 days of copper sulfate treatment compared to the control which reveals its role in copper tolerance of all studied isolates. In this study, Pleurotus eryngii and Sarocladium sp. are introduced as heavy metal tolerant fungi and the related gene expression to copper tolerance was studied for the first time in Iran.

Effects of long-term herbaceous plant restoration on microbial communities and metabolic profiles in coal gangue-contaminated soil

The soil microbial diversity in the gangue accumulation area is severely stressed by a variety of heavy metals, while the influence of long-term recovery of herbaceous plants on the ecological structure of gangue-contaminated soil is to be explored. Therefore, we analysed the differences in physicochemical properties, elemental changes, microbial community structure, metabolites and expression of related pathways in soils in the 10- and 20-year herbaceous remediation areas of coal gangue. Our results showed that phosphatase, soil urease, and sucrase activities of gangue soils significantly increased in the shallow layer after herbaceous remediation. However, in zone T1 (10-year remediation zone), the contents of harmful elements, such as Thorium (Th; 1.08-fold), Arsenic (As; 0.78-fold), lead (Pb; 0.99-fold), and uranium (U; 0.77-fold), increased significantly, whereas the soil microbial abundance and diversity also showed a significant decreasing trend. Conversely, in zone T2 (20-year restoration zone), the soil pH significantly increased by 1.03- to 1.06-fold and soil acidity significantly improved. Moreover, the abundance and diversity of soil microorganisms increased significantly, the expression of carbohydrates in soil was significantly downregulated, and sucrose content was significantly negatively correlated with the abundance of microorganisms, such as Streptomyces. A significant decrease in heavy metals was observed in the soil, such as U (1.01- to 1.09-fold) and Pb (1.13- to 1.25-fold). Additionally, the thiamin synthesis pathway was inhibited in the soil of the T1 zone; the expression level of sulfur (S)-containing histidine derivatives (Ergothioneine) was significantly up-regulated by 0.56-fold in the shallow soil of the T2 zone; and the S content in the soil significantly reduced. Aromatic compounds were significantly up-regulated in the soil after 20 years of herbaceous plant remediation in coal gangue soil, and microorganisms (Sphingomonas) with significant positive correlations with benzene ring-containing metabolites, such as Sulfaphenazole, were identified.

Role of Arbuscular Mycorrhizal Fungi in Regulating Growth, Enhancing Productivity, and Potentially Influencing Ecosystems under Abiotic and Biotic Stresses

Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with the roots of nearly all land-dwelling plants, increasing growth and productivity, especially during abiotic stress. AMF improves plant development by improving nutrient acquisition, such as phosphorus, water, and mineral uptake. AMF improves plant tolerance and resilience to abiotic stressors such as drought, salt, and heavy metal toxicity. These benefits come from the arbuscular mycorrhizal interface, which lets fungal and plant partners exchange nutrients, signalling molecules, and protective chemical compounds. Plants' antioxidant defence systems, osmotic adjustment, and hormone regulation are also affected by AMF infestation. These responses promote plant performance, photosynthetic efficiency, and biomass production in abiotic stress conditions. As a result of its positive effects on soil structure, nutrient cycling, and carbon sequestration, AMF contributes to the maintenance of resilient ecosystems. The effects of AMFs on plant growth and ecological stability are species- and environment-specific. AMF's growth-regulating, productivity-enhancing role in abiotic stress alleviation under abiotic stress is reviewed. More research is needed to understand the molecular mechanisms that drive AMF-plant interactions and their responses to abiotic stresses. AMF triggers plants' morphological, physiological, and molecular responses to abiotic stress. Water and nutrient acquisition, plant development, and abiotic stress tolerance are improved by arbuscular mycorrhizal symbiosis. In plants, AMF colonization modulates antioxidant defense mechanisms, osmotic adjustment, and hormonal regulation. These responses promote plant performance, photosynthetic efficiency, and biomass production in abiotic stress circumstances. AMF-mediated effects are also enhanced by essential oils (EOs), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), hydrogen peroxide (H2O2), malondialdehyde (MDA), and phosphorus (P). Understanding how AMF increases plant adaptation and reduces abiotic stress will help sustain agriculture, ecosystem management, and climate change mitigation. Arbuscular mycorrhizal fungi (AMF) have gained prominence in agriculture due to their multifaceted roles in promoting plant health and productivity. This review delves into how AMF influences plant growth and nutrient absorption, especially under challenging environmental conditions. We further explore the extent to which AMF bolsters plant resilience and growth during stress.