Revitalizing contaminated lands: A state-of-the-art review on the remediation of mine-tailings using phytoremediation and genomic approaches

Improving soil properties and microbial communities in copper tailings using montmorillonite-based Chlorella gel beads

Copper tailings are the waste left over from copper ore dressing, and their massive pose severe challenges to the ecosystem. In this study, sodium alginate-Chlorella-montmorillonite (SCM) gel beads were prepared by combining sodium alginate, Chlorella, and montmorillonite. The laboratory pot and in-situ field experiment results indicated that the input of SCM gel beads facilitated the formation of larger particle-size soil aggregates and enhanced soil water retention and cation exchange capacities. The pot experiment demonstrated that the application of MMT and Chlorella significantly increased organic carbon content in the tailing soil. The field experiment showed that the application of SCM gel beads at the optimal dosage of 700 g/m2 increased the plant height and fresh weight by 1.77 and 1.22 times, respectively, as well as the chlorophyll content. Furthermore, in SCM group, the proportion of large soil aggregates(particle size >0.25 mm) was increased by 6.66 %, and the R0.25, mean weight diameter (MWD), and geometric mean diameter (GWD) values were also significantly increased, and the increase in large soil aggregates and aggregate stability indicated the improvement of soil structure. Additionally, the dominant microorganisms at the phylum level were Proteobacteria, Acidobacteriota, and Bacteroidota, while they were Sphingomonas, Vicinamibacteraceae, and Candidatus at genus level. These dominant microorganisms were indigenous species to copper tailing. The alpha diversity determination results indicated that SCM gel bead input increased the microbial community richness, but had little effect on their diversity. Our results demonstrated that as soil amendment, SCM gel beads stimulated the growth of tailing native microorganisms, increasing their richness. Overall, the combination of Chlorella, and montmorillonite, as an amendment, improved soil properties of copper tailing and soil microbial community structure. Our findings provide valuable references for developing effective and sustainable soil remediation strategies in tailing areas.

Bionanoremediation of wastewater: an innovative and novel approach

Water contamination from rapid urbanization, industrialization, and agricultural activities has emerged as a critical environmental challenge, leading to widespread waterborne diseases and millions of annual fatalities. Conventional water treatment methods such as coagulation, flocculation, and sedimentation exist; they are often hindered by high chemical and energy costs. The limitations of traditional water treatment approaches have necessitated the exploration of alternative technologies that can provide more efficient and cost-effective solutions for water purification. Nanotechnology-based water treatment methods, leveraging the unique physicochemical properties of nanoparticles, can potentially overcome the limitations of conventional water treatment techniques and provide enhanced pollutant removal efficiency. This review critically evaluates the latest advances in magnetic nanoadsorbent technologies for wastewater remediation, distinguishing itself from existing literature by integrating theoretical principles with practical application. The analysis reveals that nanoparticle-based treatment methods demonstrate superior wastewater remediation performance compared to conventional techniques. The unique properties of nanoparticles enable efficient removal of various contaminants, including heavy metals, organic compounds, and bacterial populations. These findings suggest that nanotechnology-based approaches represent a viable and sustainable solution for addressing current water treatment challenges, offering a promising direction for future water purification technologies.

Phytostabilization potential and microbial response to the reclamation of native Cynodon dactylon in spoil heaps from a multiple-metal mining site in Southwest China

Phytocapping offers a sustainable approach for managing exposed tailings by mitigating pollutant spread and enhancing phytoremediation. This study investigates the potential of Bermudagrass (Cynodon dactylon) as a pioneering plant for rehabilitating tailings from an open-pit lead-zinc mine in Southwest China. Our findings demonstrate that Bermudagrass significantly improved soil quality and multifunctionality compared to adjacent bare tailings. Soil improvements included increases in organic matter (107%), total and available nitrogen (50% and 110%, respectively), available phosphorus (170%), and soil enzyme activities, including β-glucosidase (170%), sucrase (1729%), alkaline phosphatase (3722%), and acid phosphatase (168%). The reclamation process also promoted microbial community succession, altering community composition, improving microbial diversity, and enhancing bacterial biomass from (0.89 ± 0.54) × 1015 to (9.06 ± 3.25) × 1015 copies/g in rhizosphere soils. Greenhouse experiments further confirmed Bermudagrass's resilience to cadmium (Cd), with both mining and non-mining ecotypes thriving in tailing soils and Cd2+ hydroponic solutions (up to 44.5 μM) without evident phytotoxicity. Bermudagrass roots exhibited exceptional Cd accumulation (bioconcentration factor: 181-1006) while minimizing Cd translocation to shoots (translocation factor: <0.13). Inoculation with Funneliformis mosseae, a restored root-mutually symbiotic fungus, further mitigated Cd-induced phytotoxicity and enhanced plant growth. These findings highlight Bermudagrass as a promising pioneer species for phytostabilization in severely contaminated mining environments, with its rhizosphere microbiome playing a critical role in facilitating ecosystem restoration. Sustainable plant establishment in mine waste rock requires concurrent development of belowground fertility and healthy rhizospheric soil. Ultimately, successful revegetation depends on integrated above and belowground development to achieve long-term ecological restoration.

Three local plants adapt to ecological restoration of abandoned lead-zinc mines through assembly of rhizosphere bacterial communities

Introduction

The plant restoration and ecological restoration of lead-zinc mines are very important.

Methods

In this study, we used three local plants to carry out ecological restoration of abandoned lead-zinc mining areas and detected the adaptive mechanisms of soil bacterial diversity and function during the ecological restoration of lead-zinc mines through 16S rRNA sequencing.

Results

The results revealed that lead-zinc mining significantly reduced the soil bacterial diversity, including the Shannon, Simpson, and observed species indices, whereas the planting of the three ecological restoration plants restored the soil microbial diversity to a certain extent, leading to increases in the Shannon index and Observed species indices. Mining activities significantly reduced the abundances of RB41 and Bryobacter in the bulk soil compared with those in the nonmining areas, whereas the three ecological restoration plants increased the abundances of RB41 and Bryobacter in the rhizosphere soil compared with those in the bulk soil in the mining areas. Following the planting of the three types of ecologically restored plants, the soil bacterial community structure partially recovered. In addition, different plants have been found to have different functions in the lead-zinc ecological restoration process, including iron complex transport system-permitting proteins and ATP binding cassettes.

Discussion

This study confirms for the first time that plants adapt to the remediation process of abandoned lead-zinc mines by non-randomly assembling rhizosphere bacterial communities and functions, providing a reference for screening microbial remediation bacterial resources and plant microbe joint bioremediation strategies for lead-zinc mines.

Sustainable remediation of abandoned coal mines using vermicompost: a case study in Ledo coal mine, India

Coal mining in India, especially open-cast mining, substantially strengthens the economy while concurrently causing environmental deterioration, such as soil pollution with toxic chemicals and heavy metals. This study sought to examine the efficacy of vermicompost as a remediation technique for Mine Tailing Soil (MTS) in the Ledo Coal Fields. During a 120-day duration, different concentrations of vermicompost (20%, 30%, and 40%) were administered to MTS, and the impacts on soil physicochemical parameters, fertility, and plant growth were evaluated. The findings indicated substantial enhancements in soil fertility, encompassing increased nutrient availability, improved water retention, and diminished bulk density. Plant species, including Abelmoschus esculentus, Solanum lycopersicum, and Delonix regia, showed substantial growth when subjected to 20% and 30% vermicompost amendments, with the 30% treatment producing the most remarkable outcomes. Furthermore, Risk Assessment Code values for soils amended with 20%, 30%, and 40% vermicompost were markedly diminished, reducing the bioavailability and mobility of heavy metals. The data indicate that vermicompost is an efficient and sustainable method for remediating MTS, alleviating heavy metal contamination, and enhancing plant development, thus addressing the environmental hazards of coal mining.

Exploring the significance of different amendments to improve phytoremediation efficiency: focus on soil ecosystem services

Phytoremediation is recognized as an environmentally, economically and socially efficient phytotechnology for the reclamation of polluted soils. To improve its efficiency, several strategies can be used including the optimization of agronomic practices, selection of high-performance plant species but also the application of amendments. Despite evidences of the benefits provided by different types of amendments on pollution control through several phytoremediation pathways, their contribution to other soil ecosystem functions supporting different ecosystem services remains sparsely documented. This current review aims at (i) updating the state of the art about the contribution of organic, mineral and microbial amendments in improving phytostabilization, phytoextraction of inorganic and phytodegradation of organic pollutants and (ii) reviewing their potential beneficial effects on soil microbiota, nutrient cycling, plant growth and carbon sequestration. We found that the benefits of amendment application during phytoremediation go beyond limiting the dispersion of pollutants as they enable a more rapid recovery of soil functions leading to wider environmental, social and economic gains. Effects of amendments on plant growth are amendment-specific, and their effect on carbon balance needs more investigation. We also pointed out some research questions that should be investigated to improve amendment-assisted phytoremediation strategies and discussed some perspectives to help phytomanagement projects to improve their economic sustainability.

Performance of Persicaria amphibia (L.) for Phytoremediation of Heavy Metals Contaminated Water

Fast-paced global industrialization due to population growth poses negative water implications, such as pollution by heavy metals. Phytoremediation is deemed as an efficient and environmentally friendly alternative which utilizes different types of hyperaccumulator plants known as macrophytes for the removal of heavy metal pollutants from contaminated water. In this study, the removal of Cu(II), Ni(II), Pb(II), and Cd(II) heavy metal ions contaminated water was studied by using an aquatic plant, Persicaria amphibia (L.) collected from Ladik Lake, Samsun, Turkiye. The experiments were carried out hydroponically in the laboratory conditions. Synthetic heavy metals contaminated water (5, 10, 25, 50, 100 mg kg- 1), and domestic and industrial water were used in the experiments. The domestic and industrial water samples were taken from Aksu and Batlama streams in Giresun province. All physical plant changes were noted, and pH, conductivity, and dissolved oxygen levels of the hydroponic system were measured regularly during the experiments. In order to determine the effects of heavy metals on the plant, the chlorophyll (a, b and total) and carotenoid contents as well as the biomass of the plant, were measured. According to the phytoremediation experiments the amounts of accumulated heavy metals in plants were found as Cd(II) > Ni(II) > Cu(II) > Pb(II) in single systems and as Cd(II) > Ni(II) > Pb(II) > Cu(II) in competitive systems. The maximum amounts of heavy metals accumulated in plants were determined as 171 ± 9 mg kg-1 for Cd(II), 143 ± 7 mg kg-1 for Ni(II), 134 ± 8 mg kg-1 for Cu(II) and 55 ± 4 mg kg-1 for Pb(II). In addition, bioconcentration factor (BCF) values ​​were calculated to make comparisons with the phytoextraction potential of the plant. This study emphasizes the importance of P. amphibia with high bioaccumulation potential for phytoremediation and suggests that it could be employed to restore water in heavy metal-contaminated areas.

Phytoremediation of Hg and chlorpyrifos contaminated soils using Phaseolus vulgaris L. with biochar, mycorrhizae, and compost amendments

Anthropogenic activities, encompassing vast agricultural and industrial operations around the world, exert substantial pressure on the environment, culminating in profound ecological impacts. These activities exacerbate soil contamination problems with pollutants such as mercury (Hg) and chlorpyrifos (CPF) that are notable for their widespread presence and detrimental effects. The objective of this study is to evaluate the phytoremediation potential of Phaseolus vulgaris L., augmented with various combinations of biochar, mycorrhizal, and compost amendments, as a sustainable alternative for the remediation of soils contaminated with Hg and CPF. For this purpose, soil from a mining area with mercury contamination has been taken, to which CPF has been added in different concentrations. Then, previously germinated Phaseolus vulgaris L. seedlings with an average height of 10 cm were planted. Electrical conductivity, pH, organic matter, CPF, and Hg, as well as seedling growth parameters, have been evaluated to determine the processes of absorption of soil contaminants into the plant. A combination of biochar with mycorrhiza has been found to be an optimal choice for CPF and Hg remediation. However, all amendments have proven to be efficient in the remediation processes of the tested contaminants.

Microbial-assistance and chelation-support techniques promoting phytoremediation under abiotic stresses

Phytoremediation, the use of plants to remove heavy metals from polluted environments, has been extensively studied. However, abiotic stresses such as drought, salt, and high temperatures can limit plant growth and metal uptake, reducing phytoremediation efficiency. High levels of HMs are also toxic to plants, further decreasing phytoremediation efficacy. This manuscript explores the potential of microbial-assisted and chelation-supported approaches to improve phytoremediation under abiotic stress conditions. Microbial assistance involves the use of specific microbes, including fungi that can produce siderophores. Siderophores bind essential metal ions, increasing their solubility and bioavailability for plant uptake. Chelation-supported methods employ organic acids and amino acids to enhance soil absorption and supply of essential metal ions. These chelating agents bind HMs ions, reducing their toxicity to plants and enabling plants to better withstand abiotic stresses like drought and salinity. Managed microbial-assisted and chelation-supported approaches offer more efficient and sustainable phytoremediation by promoting plant growth, metal uptake, and mitigating the effects of heavy metal and abiotic stresses. Managed microbial-assisted and chelation-supported approaches offer more efficient and sustainable phytoremediation by promoting plant growth, metal uptake, and mitigating the effects of HMs and abiotic stresses.These strategies represent a significant advancement in phytoremediation technology, potentially expanding its applicability to more challenging environmental conditions. In this review, we examined how microbial-assisted and chelation-supported techniques can enhance phytoremediation a method that uses plants to remove heavy metals from contaminated sites. These approaches not only boost plant growth and metal uptake but also alleviate the toxic effects of HMs and abiotic stresses like drought and salinity. By doing so, they make phytoremediation a more viable and effective solution for environmental remediation.

Unraveling the potential of hydrogen sulfide as a signaling molecule for plant development and environmental stress responses: A state-of-the-art review

Over the past decade, a plethora of research has illuminated the multifaceted roles of hydrogen sulfide (H2S) in plant physiology. This gaseous molecule, endowed with signaling properties, plays a pivotal role in mitigating metal-induced oxidative stress and strengthening the plant's ability to withstand harsh environmental conditions. It fulfils several functions in regulating plant development while ameliorating the adverse impacts of environmental stressors. The intricate connections among nitric oxide (NO), hydrogen peroxide (H2O2), and hydrogen sulfide in plant signaling, along with their involvement in direct chemical processes, are contributory in facilitating post-translational modifications (PTMs) of proteins that target cysteine residues. Therefore, the present review offers a comprehensive overview of sulfur metabolic pathways regulated by hydrogen sulfide, alongside the advancements in understanding its biological activities in plant growth and development. Specifically, it centres on the physiological roles of H2S in responding to environmental stressors to explore the crucial significance of different exogenously administered hydrogen sulfide donors in mitigating the toxicity associated with heavy metals (HMs). These donors are of utmost importance in facilitating the plant development, stabilization of physiological and biochemical processes, and augmentation of anti-oxidative metabolic pathways. Furthermore, the review delves into the interaction between different growth regulators and endogenous hydrogen sulfide and their contributions to mitigating metal-induced phytotoxicity.

Microbial oases in the ice: A state-of-the-art review on cryoconite holes as diversity hotspots and their scientific connotations

Cryoconite holes, small meltwater pools on the surface of glaciers and ice sheets, represent extremely cold ecosystems teeming with diverse microbial life. Cryoconite holes exhibit greater susceptibility to the impacts of climate change, underlining the imperative nature of investigating microbial communities as an essential module of polar and alpine ecosystem monitoring efforts. Microbes in cryoconite holes play a critical role in nutrient cycling and can produce bioactive compounds, holding promise for industrial and pharmaceutical innovation. Understanding microbial diversity in these delicate ecosystems is essential for effective conservation strategies. Therefore, this review discusses the microbial diversity in these extreme environments, aiming to unveil the complexity of their microbial communities. The current study envisages that cryoconite holes as distinctive ecosystems encompass a multitude of taxonomically diverse and functionally adaptable microorganisms that exhibit a rich microbial diversity and possess intricate ecological functions. By investigating microbial diversity and ecological functions of cryoconite holes, this study aims to contribute valuable insights into the broader field of environmental microbiology and enhance further understanding of these ecosystems. This review seeks to provide a holistic overview regarding the formation, evolution, characterization, and molecular adaptations of cryoconite holes. Furthermore, future research directions and challenges underlining the need for long-term monitoring, and ethical considerations in preserving these pristine environments are also provided. Addressing these challenges and resolutely pursuing future research directions promises to enrich our comprehension of microbial diversity within cryoconite holes, revealing the broader ecological and biogeochemical implications. The inferences derived from the present study will provide researchers, ecologists, and policymakers with a profound understanding of the significance and utility of cryoconite holes in unveiling the microbial diversity and its potential applications.