Heavy metals and persistent organic pollutants are causing detrimental effects on the environment. The seepage of heavy metals through untreated industrial waste destroys the crops and lands. ...Moreover, incineration and combustion of several products are responsible for primary and secondary emissions of pollutants. This review has gathered the remediation strategies, current bioremediation technologies, and their primary use in both in situ and ex situ methods, followed by a detailed explanation for bioremediation over other techniques. However, an amalgam of bioremediation techniques and nanotechnology could be a breakthrough in cleaning the environment by degrading heavy metals and persistant organic pollutants.
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•Recent bioremediation strategies for HMs and POPs were summarized.•The role of bio-adsorbents in HMs and POPs removal was elaborated.•The role of bacteria and fungi in bioremediation was discussed in detail.•Use of nanozymes for the removal of pollutants is an effective strategy.•Development of effective combination of strategies to combat environmental pollution in future was suggested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Since the 1980s, there has been increasing concern over heavy metal pollution remediation. However, most research focused on the individual remediation technologies for heavy metal pollutants in ...either soil or water. Considering the potential migration of these pollutants, it is necessary to explore effective integrated remediation technologies for soil and water heavy metals. This review thoroughly examines non-phytoremediation technologies likes physical, chemical, and microbial remediation, as well as green remediation approaches involving terrestrial and aquatic phytoremediation. Non-phytoremediation technologies suffer from disadvantages like high costs, secondary pollution risks, and susceptibility to environmental factors. Conversely, phytoremediation technologies have gained significant attention due to their sustainable and environmentally friendly nature. Enhancements through chelating agents, biochar, microorganisms, and genetic engineering have demonstrated improved phytoremediation remediation efficiency. However, it is essential to address the environmental and ecological risks that may arise from the prolonged utilization of these materials and technologies. Lastly, this paper presents an overview of integrated remediation approaches for addressing heavy metal contamination in groundwater-soil-surface water systems and discusses the reasons for the research gaps and future directions. This paper offers valuable insights for comprehensive solutions to heavy metal pollution in water and soil, promoting integrated remediation and sustainable development.
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•Advancements in HM remediation technologies were systematically reviewed.•Optimizing materials, equipment, parameters can enhance removal efficiency of HMs.•Sustainability should be focused when refining phytoremediation techniques.•NPs and apatite particles hold potential for the integrated remediation.•Interdisciplinary research is needed to explore integrated remediation techniques.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Globally there are over 20millionha of land contaminated by the heavy metal(loid)s As, Cd, Cr, Hg, Pb, Co, Cu, Ni, Zn, and Se, with the present soil concentrations higher than the geo-baseline or ...regulatory levels. In-situ and ex-situ remediation techniques have been developed to rectify the heavy metal-contaminated sites, including surface capping, encapsulation, landfilling, soil flushing, soil washing, electrokinetic extraction, stabilization, solidification, vitrification, phytoremediation, and bioremediation. These remediation techniques employ containment, extraction/removal, and immobilization mechanisms to reduce the contamination effects through physical, chemical, biological, electrical, and thermal remedy processes. These techniques demonstrate specific advantages, disadvantages, and applicability. In general, in-situ soil remediation is more cost-effective than ex-situ treatment, and contaminant removal/extraction is more favorable than immobilization and containment. Among the available soil remediation techniques, electrokinetic extraction, chemical stabilization, and phytoremediation are at the development stage, while the others have been practiced at full, field scales. Comprehensive assessment indicates that chemical stabilization serves as a temporary soil remediation technique, phytoremediation needs improvement in efficiency, surface capping and landfilling are applicable to small, serious-contamination sites, while solidification and vitrification are the last remediation option. The cost and duration of soil remediation are technique-dependent and site-specific, up to $500ton−1 soil (or $1500m−3 soil or $100m−2 land) and 15years. Treatability studies are crucial to selecting feasible techniques for a soil remediation project, with considerations of the type and degree of contamination, remediation goals, site characteristics, cost effectiveness, implementation time, and public acceptability.
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•Various remediation methods have been developed for heavy metal-contaminated soils.•In-situ, contaminant removal/extraction remediation techniques are more favorable.•The methods landfilling, soil washing, and solidification are well established.•Electrokinetic extraction, chemical stabilization, and phytoremediation are immature.•Treatability studies are crucial to selecting feasible soil remediation techniques.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The current status of environmental pollution by heavy metals (HMs) will affect the entire ecosystem components. The results obtained so far indicate that some plants can be effective in removing ...toxic metals from the soil. For this purpose, the phytoremediation ability of three fleshy ornamental plants; cactus (Opuntia humifusa), kalanchoe (Kalanchoe blossfeldiana) and bryophyllum (Bryophyllum delagoensis), was evaluated under the stress of HMs. These succulents are known for their remarkable adaptive capabilities, allowing them to thrive in harsh environmental conditions, including those with high levels of contaminants. Their robust nature, efficient water-use strategies, and proven potential for heavy metal accumulation made them viable candidates for investigating their phytoremediation potential. This experiment was performed as factorial based on completely randomized block design with two factors; the first factor included the type of plant in 3 levels (cactus, kalanchoe and bryophyllum) and the second one included the type of metal in 5 levels (control, silver, cadmium, lead and nickel) in 3 repetitions. The concentration of each salt used was 100 ppm. The measured parameters included stem height, relative growth, diameter, dry matter percentage of root and shoot, chlorophyll a, b and total chlorophyll, carotenoid, anthocyanin, proline, and elements of nickel, silver, lead and cadmium, as well biological concentration factor. The results showed that the highest amount of final stem height, relative growth, dry matter percentage of shoot and the highest amount of chlorophyll a and b, carotenoid and anthocyanin were obtained in bryophyllum. Also, the results of mean comparison of the data related to the effect of metal type on the plants showed that the highest amount of carotenoid, anthocyanin and biological concentration factor were induced by cadmium. On the other hand, the highest and lowest amount of proline as well anthocyanin and proline were induced by silver and lead, respectively. Totally, bryophyllum had a high resistance to HMs and the examined HMs had less effect on the growth of this plant. Cactus, among trial species, exhibited superior potential for HM absorption compared to kalanchoe and bryophyllum. The study underscores cactus as an excellent phytoremediator.
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•Succulent plants such as cactus and bryophyllum proved to be effective in phytoremediation because of their resistant nature.•Ornamental plants with high heavy metal uptake capacity effectively reduce environmental contamination.•Cactus exhibited superior potential for HM absorption compared to kalanchoe and bryophyllum.•Understanding plant adaptation to environmental stressors remains crucial.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Plant species for accumulating Hg studied in the past 20 years are reviewed.•The type of Hg accelerators studied in the past 20 years are reviewed.•Transgenic plants for accumulating studied in the ...past 20 years are reviewed.•Phytoremediation and assisted phytoremediation are compared and discussed.•Some significant future perspectives are proposed.
Mercury (Hg) and its compounds are one of the most dangerous environmental pollutants and Hg pollution exists in soils in different degrees over the world. Phytoremediation of Hg-contaminated soils has attracted increasing attention for the advantages of low investment, in-situ remediation, potential economic benefits and so on. Searching for the hyperaccumulator of Hg and its application in practice become a research hotspot. In this context, we review the current literatures that introduce various experimental plant species for accumulating Hg and aided techniques improving the phytoremediation of Hg-contaminated soils. Experimental plant species for accumulating Hg and accumulation or translocation factor of Hg are listed in detail. The translocation factor (TF) is greater than 1.0 for some plant species, however, the bioaccumulation factor (BAF) is greater than 1.0 for Axonopus compressus only. Plant species, soil properties, weather condition, and the bioavailability and heterogeneity of Hg in soils are the main factors affecting the phytoremediation of Hg-contaminated soils. Chemical accelerator kinds and promoting effect of chemical accelerators for accumulating and transferring Hg by various plant species are also discussed. Potassium iodide, compost, ammonium sulphate, ammonium thiosulfate, sodium sulfite, sodium thiosulfate, hydrochloric acid and sulfur fertilizer may be selected to promote the absorption of Hg by plants. The review introduces transgenic gene kinds and promoting effect of transgenic plants for accumulating and transferring Hg in detail. Some transgenic plants can accumulate more Hg than non-transgenic plants. The composition of rhizosphere microorganisms of remediation plants and the effect of rhizosphere microorganisms on the phytoremediation of Hg-contaminated soils are also introduced. Some rhizosphere microorganisms can increase the mobility of Hg in soils and are beneficial for the phytoremediation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The heavy metal cadmium (Cd), known for its high toxicity, poses a grave threat to human health through the food chain. N6-methyladenosine (m6A), the most abundant internal modification, regulates ...plant adaptation to various adversities, yet the panorama of m6A modifications in switchgrass under cadmium stress remains elusive. This study examines the physiological responses of switchgrass roots and shoots exposed to 50 μM CdCl2, alongside an overview of transcriptome-wide m6A methylation patterns. After cadmium treatment, methylation modifications are primarily enriched near stop codons and the 3′UTR region, with a negative correlation between m6A modification and gene expression levels. In shoots, approximately 58 % of DEGs with m6A modifications show upregulation in expression and decrease in m6A peaks, including zinc transporter 4-like (ZIP4). In roots, about 43 % of DEGs with m6A modifications exhibit downregulation in expression and increase in m6A peaks, such as the ABC transporter family member (ABCG25). We further validate the m6A enrichment, gene expression and mRNA stability of ZIP4 in response to Cd treatment. The results suggest that the negative correlation of m6A enrichment and gene expression is due to altered mRNA stability. Our study establishes an m6A regulatory network governing cadmium transport in switchgrass roots and shoots, offering new avenues for candidate gene manipulation in phytoremediation applications of heavy metal pollution.
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•Under Cd stress, m6A RNA methylation peaks within the transcriptome generally decrease in shoots but increase in roots.•In shoots, genes related to defense response are upregulated, while genes involved in photosynthesis pathways are downregulated.•In roots, genes modified by m6A under Cd stress may play a role in regulating oxidative stress response.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study aimed to shed further light on the capacity of macrophytes to translocate, accumulate and bioindicate the levels of trace elements present in contaminated water and sediments. ...Specifically, this study aimed to find evidence whether translocation, accumulation and bioindication are dependent on the kind of trace element and plant species. To investigate the correlation between trace elements in plants and in the environment, the concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn were analyzed in twenty different wetland plants, and in water and sediments from a wetland area affected by urban and industrial pollutants. Results showed that wetland plants share some common characteristics such as high tolerance to toxic element levels, capacity of phytostabilization and different element concentrations in the various organs. Moreover, element translocation from sediments to roots seems more influenced by the kind of plant species and trace element, whereas translocation across the various organs seems mainly species-specific. No clear patterns of trace element translocation were identified according to plant life forms.
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•Capacity of trace element accumulation is independent of plant life forms.•Translocation from sediment to roots is mainly species- and element-specific.•Translocation across internal tissues is mainly species-specific.•Wetland plants are potentially suitable for the phytostabilization of trace elements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Widespread lead (Pb) contamination of agricultural soils is a global issue stemming from human activities. The remediation of Pb-contaminated soils used for agricultural purposes is critically ...important to safeguard food crop safety. Despite the modulating effects of sulfur (S) on plant responses to toxic heavy metals, the ecological, physiological, and molecular mechanisms driving such modulation in the Pb hyperaccumulator Arabis alpina L. remain unclear. Here, we investigated the effects of five S concentrations (0, 50, 100, 150, and 200 mg kg−1) on A. alpina grown in Pb-contaminated soil from a lead-zinc mining area. Under S50 (i.e., 50 mg kg−1) and S100 treatments, the Pb concentration in both shoots and roots of A. alpina significantly decreased compared to the control (S0). Specifically, the S50 treatment significantly enhanced Pb accumulation, plant biomass, and plant height, indicating that low S applications facilitate Pb accumulation from the soil and alleviate Pb toxicity. Additionally, S50, S100, and S150 treatments significantly improved photosynthetic rate, stomatal conductance, and intercellular CO2 concentration in A. alpina. Transcriptomic analysis showed that S50 and S100 treatments increased the expression of the LHCA, LHCB, psa, and psb genes, which had a significant impact on photosynthetic efficiency. S50 and S100 boosted glutathione (GSH) levels in A. alpina roots, and the increased expression of GST gene enhanced tolerance to environmental stress. In summary, these results suggest that an appropriate supply of S (S50 and S100) not only alleviates Pb toxicity by enhancing plant biomass, height, photosynthetic features, and sulfur metabolites but also stimulates Pb accumulation in the hyperaccumulator A. alpina. Our study elucidated the specific concentrations of sulfur that optimally enhance both Pb accumulation and stress tolerance in the hyperaccumulator A. alpina, providing novel insights into the practical application of sulfur in phytoremediation strategies and advancing our understanding of the underlying molecular mechanisms.
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•Sulfur supply enhanced plant growth and lead accumulation simultaneously.•S supply increased photosynthetic efficiency and expression of related genes.•S supply boosted GSH level, enhanced GST expression, improved plant tolerance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Phytoremediation is a low-cost, environmentally friendly, and sustainable technology that can utilize vegetation and microorganisms to avoid eutrophication and purifying water environment. The ...ability of five different living aquatic plants of nitrogen (N), phosphorus (P), and chemical oxygen demand (CODcr) removal were investigated in pilot scale constructed wetlands (CWs). Aquatic plant mixes significantly improved CODcr removal and plant tissue uptake of nitrogen and phosphorus. The wetland performance of mixed plantings was also influenced by the specific species. The mixed planting of Phragmites australi, Nymphaea Colorado and Myriophyllum verticillatum (PNM)When assessing pollutant removal in CWs, PNM performed better within mixtures, a possible synergistic effect, while TNV Typha orientalis, Nymphaea Colorado, and Vallisneria natans (TNV) performed poorly, a possible antagonist effect. The nutrient uptake within plant tissues byunder mixed plants planting was always ahad synergistic effect. Mixed plantingAquatic plant mixes significantly increased the rhizosphere microbial diversity and promoted the growth of functional denitrifying flora.
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•Mixed planting significantly promoted CODcr removal, but had no effect on nitrogen and phosphorus removal.•Mixed planting of plants were always synergistic on plant uptake of nitrogen and phosphorus.•Mixed planting significantly increased the rhizosphere microbial diversity and promoted the growth of denitrifying flora.•Selecting the right mix of plants is an effective means to enhance the efficiency of CWs and improve eutrophication.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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