Search Results (1,139)

The post-treatment of heavy metal-enriched plants in mining areas and the purification of ammonia and nitrogen pollution in water bodies are significant for the ecological environment of ionic rare earth mining areas. Herein, we focused on the biochar production potential of Dicranopteris pedata, characterizing biochar prepared by an oxidative modification process and an iron modification process. We conducted adsorption experiments to comparatively investigate the adsorption performance of biochar on NH₄⁺ and studied the fertilizer application and migration toxicity of the adsorbed biochar for rare earth elements (REEs). Results indicated that ~332.09 g of biochar could be produced per unit area of D. pedata under 100% clipping conditions. The Brunauer–Emmett–Teller (BET) specific surface area of oxidized biochar (H₂O₂BC) increased, and the pore size of iron-modified biochar increased. The adsorption behavior of biochar toward NH₄⁺ was well represented by the pseudo-second-order and Langmuir models. H₂O₂BC demonstrated the strongest adsorption of NH₄⁺ with maximum theoretical equilibrium adsorption of 43.40 mg·g⁻¹, 37.14% higher than that of pristine biochar. The adsorption process of NH₄⁺ on biochar is influenced by various physicochemical mechanisms, including pore absorption, electrostatic attraction, and functional group complexation. Furthermore, the metal ions in the biochar did not precipitate during the reaction process. The adsorbed NH₄⁺ biochar promoted the growth of honey pomelo without risking REE pollution to the environment. Therefore, it can be applied as a nitrogen-carrying rare earth fertilizer in low rare earth areas. This study provides a theoretical basis and technical support for the phytoremediation post-treatment of rare earth mining areas and the improvement of ammonia nitrogen wastewater management pathways in mining areas. Full article

Coal mining is known to have negative impacts on the environment, necessitating land rehabilitation after mining activities. Amongst the problems associated with coal mining is the accumulation of acid mine drainage characterized by large amounts of heavy metals and high acidity. The impact of these environmental problems on the ecosystem around mining areas underscores a need to devise strategies that will ensure sustainable restoration of the ecosystem integrity to ensure environmental protection. Of these, treatment of acid mine drainage using calcium sulfate dihydrate, which is subsequently used for irrigation during phytoremediation, holds great promise for restoration of open-cast mines. However, although grasses are used for rehabilitation of coal mined areas, the impacts of treated mine water on the germination, seedling emergence, and plant growth of grasses are not well known. The aim of the study was to evaluate the germination and early seedling growth responses of different forage grasses to treated mine water. Seven forage grass species were selected, with four species represented by two varieties while others were represented by one variety, totaling 11 forage grasses. For each plant entry, 100 seeds were placed in J.R. Petri’s dishes lined with Whatman No. 2 filter paper and watered with distilled and mine water to assess germination. For the seedling establishment experiment, only five species were studied, in which twenty seeds per species were sown in pots containing mine soil and irrigated using distilled and treated mine water. The final germination percentage (FGP), germination rate index (GRI), corrected germination rate index (CGRI), and T₅₀ were determined for the germination trail and total biomass was assessed for the seedling growth trail. The highest FGP for all grasses was attained under controlled conditions, using distilled water, ranging from 38–94%. All grasses germinated when watered using treated mine water and had a FGP ranging from 20–91%. Relative to distilled water, GRI and CGRI were highest only for L. multiflorum cv AgriBoost when seeds were watered using the treated mine water. All grasses watered with treated mine water produced high biomass for the first two weeks, after which biomass production started to decline. Two grasses, Eragrostis curvula cv Ermelo and Lolium multiflorum cv Archie, showed tolerance to treated mine water irrespective of its high electrical conductivity (557 mS∙m⁻¹). Therefore, these grasses could be used in the rehabilitation of coal-mined areas irrigated with treated mine water. Full article

Cadmium (Cd) pollution in soil has become a huge problem for agricultural production in China and even the world. Passivation and phytoremediation are two important remediation technologies for Cd pollution. In this study, the cadmium-contaminated and phosphorus-poor farmland soil around a mining area in Huainan was taken as the research object, and the remediation effect of biochar and phosphorus-containing materials on soil cadmium pollution was discussed. The results showed that the combined application of biochar and phosphorus-containing materials significantly reduced the pH of non-rhizosphere soil and rhizosphere soil, and increased the content of soil dissolved organic carbon (DOC). The combined application of biochar and phosphorus-containing materials significantly reduced soil pore water Cd and soil available Cd. In addition, both a single application of biochar and synergistic application of biochar and phosphorus-containing materials significantly increased the biomass of aboveground and underground parts of amaranth and soil urease and catalase activities. Phosphorus application reduced the bioavailability of Cd in soil. With the increase in phosphorus application, the content of available Cd in soil decreased significantly, and there was a certain negative correlation between Cd content and phosphorus content in plants. The abundance of beneficial microorganisms such as Ochrobactrum, Anaerolinea, Achromobacter, and Cellvibrio in soil was significantly increased after the synergistic application of biochar and phosphorus-containing materials. Full article

This study aimed to explore the impact of various ornamental plants (Heliconia psittacorum, Etlingera elatior, Spatyphilum walisii) grown in different filter media (porous river rock (PR) and tepezyl (TZ)) on the removal of pollutants in vertical-subsurface-microcosm treatment wetlands (TWs). This study also sought to assess the adaptability of these plant species to TW conditions. Twenty-four microcosm systems were utilized, with twelve containing PR and twelve containing TZ as the filter media. Each porous media type had three units planted with each species, and three were left unplanted. Rural community wastewater was treated in the TWs. The results showed no significant differences in the effects of the porous media on pollutant removal performance (p > 0.05). However, it was noted that while both porous media were efficient, TZ, a residue of construction materials, is recommended for sites facing economic constraints. Additionally, the removal efficiency was found to be independent of the type of ornamental plant used (p > 0.05); however, the measured parameters varied with plant spp. The adaptation of the plants varied depending on the species. H. psittacorum grew faster and produced a larger number of flowers compared to the other species (20–22 cm). S. wallisii typically produced 7–8 flowers. E. elatior did not produce flowers, and some plants showed signs of slight disease and pests, with the leaves turning yellow. In terms of plant biomass, the type of porous media used did not have a significant effect on the production of above (p = 0.111) or below-ground biomass (p = 0.092). The removal percentages for COD in the presence and absence of plants were in the ranges of 64–77% and 27–27.7%, respectively. For TN, the numbers were 52–65% and 30–31.8%, and for N-NO₃, they were 54–60% and 12–18%. N-NH₄ saw removal rates of 67–71% and 28–33%, while P-PO₄ saw removal rates of 60–72% and 22–25%. The difference in removal percentages between microcosms with and without plants ranged from 30 to 50%, underscoring the importance of plants in the bio-removal processes (phytoremediation). These results reveal that incorporating ornamental plants in TWs with TZ for wastewater in rural areas holds great promise for enhancing the visual appeal of these systems and ultimately gaining public approval. Our findings also enable us to offer recommendations for selecting suitable plants and substrates, as well as designing combinations for TWs. Full article

Trichomes play a key role in both heavy metal tolerance and herbivory defense, and both stressors have been shown to induce increased trichome density. However, the combined effect of these stressors on trichome density in general, and specifically on metal-hyperaccumulating plants, has yet to be examined. The aim of this study was to test the effect of cadmium availability and herbivory on leaf trichome density and herbivore deterrence in the metal hyperaccumulator Helianthus annuus. To test this, H. Annuus plants were grown in control pots or pots inoculated with 10 mg/kg cadmium and were subjected to either no herbivory or simulated herbivory using mechanical damage and foliar jasmonic acid application. Herbivore deterrence was tested in a feeding assay using Spodoptera littoralis caterpillars. Interestingly, while the trichome density of H. annuus increased by 79% or 53.5% under high cadmium availability or simulated herbivory, respectively, it decreased by 26% when the stressors were combined. Furthermore, regardless of cadmium availability, simulated herbivory induced a 40% increase in deterrence of S. littoralis. These findings suggest that the combination of metal availability and herbivory might present excessive stress to hyperaccumulators. Moreover, they suggest that the risk of metal bioaccumulation in phytoremediation can be reduced by simulated herbivory. Full article

The exogenous application of oxalic acid is a potential approach to amplifying phytoremediation performance on Cd-contaminated soils. However, few studies explore the optimal oxalic acid application regime from a perspective of coupling different concentrations and timings to maximize Cd removal rate. Given this, a pot experiment was conducted using oil sunflower (Helianthus annuus L.) as the test plant. Oxalic acid was added to the pots at concentrations of 1, 2, 3, 4, 5, and 6 mmol/kg at 20, 30, 40, and 50 days after emergence. A control (CK) without exogenous oxalic acid was also included. We examined the discrepancies in various soil Cd forms, sunflower height, plant non-protein thiol (NPT) levels, and soil Cd remediation efficiency under different oxalic acid application regimes. The results showed that applying oxalic acid at a concentration of 4 mmol/kg reduced the proportion of Fe-Mn oxide Cd and organic Cd compared to the control (CK), while increased the proportion of available Cd. The optimal application time is 30 or 40 days after emergence. The addition of exogenous oxalic acid promoted the growth of sunflowers, with the greatest increase in plant height observed when 4 mmol/kg oxalic acid was applied at 30 days after emergence. Exogenous oxalic acid enhanced the absorption of Cd by sunflower roots, with the total Cd accumulation in roots, stems, and leaves being higher than in the control (CK). When 4 mmol/kg oxalic acid was applied at 30 days after emergence, the total Cd accumulation in roots, stems, and leaves was highest. Under different application times and concentration levels of oxalic acid, Cd accumulation was highest in roots, followed by leaves, with stems showing the lowest accumulation. The NPT content in each part is as follows: root > stem > leaf. Applying 5 mmol/kg oxalic acid after 30 days of sunflower emergence resulted in relatively higher total NPT content in roots, stems, and leaves compared to the control (CK). The TOPSIS model was used for comprehensive evaluation, which showed that 4 mmol/kg oxalic acid application at 30 days after emergence could be used as the optimal oxalic acid application regime for phytoremediation. These findings indicate that the addition of oxalic acid effectively promoted the absorption of Cd by sunflower and increased the efficiency of Cd removal from the rhizosphere soil, with the optimal removal of soil Cd achieved by applying oxalic acid at a concentration of 4 mmol/kg 30 days after the emergence of oilseed sunflower seedlings. Full article

Urban development in south-eastern Europe has significant ecological consequences, such as a reduction in native plant diversity, the introduction of non-native species, and increased maintenance costs of urban green spaces. Achieving sustainable urban development requires a thorough understanding of the inventory of native plant species to better manage and conserve these areas. This study analyzed 806 vegetation surveys conducted in rural and urban areas over a 30-year period, identifying 450 plant species from 39 distinct plant communities. Our findings revealed generally low dominance index values in all communities, while Shannon diversity index values were particularly high, indicating rich species diversity despite urbanization pressures. Equality index values varied slightly, reflecting differences in species distributions. Principal component analysis (PCA) identified a substantial group of species with low abundance, which is essential for understanding and managing urban biodiversity. These findings have significant implications for urban planning and plant species conservation. Low dominance and high diversity suggest opportunities to improve urban green spaces by integrating diverse native species. In addition, the ecological and practical value of ruderal species, plants that thrive in disturbed environments, was emphasized, as well as their potential in medicine, phytoremediation, green roof design, and pollination services. Through directly correlating biodiversity indices with urban sustainability goals, our study provides useful insights for urban biodiversity management and the strategic integration of native plant species into urban landscapes. Full article

Plants growing in heavy metal (HM)-contaminated soil have evolved a special detoxification mechanism. The rhizosphere gathers many living substances and their secretions at the center of plant roots, which has a unique ecological remediation effect. It is of great significance to thoroughly understand the ecological process of rhizosphere pollution under heavy metals (HMs) stress and develop biotechnology for joint remediation using plants and their coexisting microbial systems according to the mechanism of rhizosphere stress. Microbes can weaken the toxicity of HM pollutants by transforming the existing forms or reducing the bioavailability in the rhizosphere. Microbes survive in the HM-polluted soils through the production of stress-resistant substances, the participation of proteins, and the expression of heavy metal resistance genes, which strengthens the resistance of plants. Moreover, microbes can improve the nutritional status of plants to improve plant resistance to HMs. Plants, in turn, provide a habitat for microbes to survive and reproduce, which greatly accelerates the process of bioremediation. Briefly, the combined remediation of soil HMs pollution by plants and microbes is a promising, green, and sustainable strategy. Here, we mainly elucidate the joint remediation mechanism of plant–microbe symbiosis and introduce the coping characteristics of plants, microbes, and their symbiotic system, hoping to provide a scientific basis for the remediation of HM-contaminated soil in mining areas and the sustainable development of the ecological environment. Full article

The objective of the present study was to isolate endophytes from the roots of the halophyte Sesuvium portulacastrum, which is applied for aquatic phytoremediation. From these endophytes, siderophore-producing bacteria were specifically isolated for their potential capacity to promote plant growth. The siderophore production capacity of the isolated bacteria was quantified, and a high-yield siderophore-producing strain was selected for further investigation. A total of 33 endophytic bacteria were successfully isolated and identified using a culturable approach. Of these, 10 siderophore-producing bacteria were identified using the selective agar assay, displaying siderophore unit (SU) values ranging from 11.90% to 80.39%. It is noteworthy that Erwinia sp. QZ-E9 exhibited the highest siderophore production capacity, achieving an SU of 80.39%. A microcosm co-cultivation experiment was conducted with the strain QZ-E9 in iron-deficient conditions (2 μmol/L Fe³⁺). The results demonstrated that strain QZ-E9 significantly enhanced the growth of S. portulacastrum, by increases in both fresh weight (1.41 g) and root length (18.7 cm). Furthermore, fluorescence in situ hybridization (FISH) was utilized to ascertain the colonization pattern of strain QZ-E9 within the plant roots. The analysis demonstrated that strain QZ-E9 exhibited extensive colonization of the epidermal and outer cortical cells of S. portulacastrum roots, as well as the intercellular spaces and vascular tissues. This colonization indicated that Erwinia sp. QZ-E9 plays a crucial role in promoting the growth of S. portulacastrum, presumably through its siderophore-mediated iron acquisition mechanism. Full article

As a great economic Solanum with ornamental value and good adaptability, Solanum aculeatissimum is considered an excellent candidate for the phytoremediation of Cadmium-contaminated soils. However, there are no studies on the involvement of S. aculeatissimum in the response and tolerance mechanisms of cadmium (Cd) stress. In the present study, S. aculeatissimum was used for the first time for physiological and transcriptomic systematic analysis under different concentrations of Cd stress. The results showed that S. aculeatissimum was indeed well tolerant to Cd and showed Cd enrichment capabilities. Under the Cd stress treatment of 50 mg/kg (Cd6), S. aculeatissimum could still grow normally. At the 90th day of Cd stress, the amount of Cd content in different parts of the plant at the same concentration was in the order of root > stem > leaf. With the extension of the stress time up to 163 d, the trend of Cd content in each part was not consistent, and the results in the root (77.74 mg/kg), stem (30.01 mg/kg), leaf (29.44 mg/kg), immature fruit (18.36 mg/kg), and mature fruit (21.13 mg/kg) of Cd peaked at Cd4, Cd5, Cd1, Cd4, and Cd4, respectively. The enrichment and transport coefficients of all treatments were greater than 1. The treatment groups with the largest and smallest enrichment coefficients were Cd4 and CK, respectively. The treatment groups with the largest and smallest transport coefficients were CK and Cd4, respectively. Malondialdehyde (MDA), peroxidase (POD), and catalase (CAT) in the antioxidant system after Cd stress treatment were significantly increased compared to the untreated group. Under cadmium stress, by using real-time quantitative PCR, four genes (SaHMA20, SaL-AO, SaPrxs4, and SaPCs) were screened for possible correlations to Cd tolerance and absorption enrichment in S. aculeatissimum. The key DEGs are mainly responsible for the metabolic pathways of heavy metal ATPases, plastocyanin protein phytocyanins (PCs), peroxidases (Prxs), and ascorbate oxidase (AAO); these differential genes are believed to play an important role in Cd tolerance and absorption enrichment in S. aculeatissimum. Full article

Phytoremediation is a sustainable technique that employs plants to reinforce polluted environments such as agroecosystems. In recent years, new strategies involving the plant microbiome as an adjuvant in remediation processes have been reported. By leveraging this microbial assistance to remediate soils contaminated with heavy metals such As, Pb, Cd, Hg, and Cr, plants can sequester, degrade, or stabilize contaminants more efficiently. Remarkably, some plant species are known for their hyper-accumulative traits in synergy with their microbial partners and can successfully mitigate heavy metal pollutants. This sustainable biotechnology based on plant–microbe associations not only aids in environmental cleanup but also enhances biodiversity, improves soil structure, and promotes plant growth and health, making it a promising solution for addressing agro-pollution challenges worldwide. The current review article emphasizes the potential of synergistic plant–microbe interactions in developing practical and sustainable solutions for heavy metal remediation in agricultural systems, which are essential for food security. Full article

The dwindling availability of agricultural land, caused by factors such as rapid population growth, urban expansion, and soil contamination, has significantly increased the pressure on food production. To address this challenge, cultivating non-food crops on contaminated land has emerged as a promising solution. This approach not only frees up fertile soil for food production but also mitigates human exposure to contaminants. This work aimed to examine the impact of soil contamination with Cd, Pb, Ni, and Zn on the growth, productivity, metal accumulation, and the tolerance of five lignocellulosic non-food crops: switchgrass (Panicum virgatum L.), biomass sorghum (Sorghum bicolor L. Moench), giant reed (Arundo donax L.), African fodder cane (Saccharum spontaneum L. spp. aegyptiacum Willd. Hackel), and miscanthus (Miscanthus × giganteus Greef et Deu.). A two-year pot experiment was conducted in Greece, Italy, and Portugal, following the same protocols and applying various levels of metals: Cd (0, 4, 8 mg kg⁻¹), Pb and Zn (0, 450, 900 mg kg⁻¹), and Ni (0, 110, 220 mg kg⁻¹). The experimental design was completely randomized, with three replicates for each treatment. The results showed that switchgrass and sorghum generally maintained their height and productivity under Cd and Pb stress but were adversely affected by high Zn and Ni concentrations. Giant reed and African fodder cane showed reduced height and productivity at higher Ni and Zn levels. Miscanthus exhibited resilience in height but experienced productivity reductions only at the highest Zn concentration. Heavy metal uptake varied among crops, with switchgrass and sorghum showing high Cd and Pb uptake, while giant reed accumulated the most Cd and Zn. Miscanthus had the highest Ni accumulation. The tolerance indices indicated that switchgrass and sorghum were more tolerant to Cd and Zn at lower concentrations, whereas miscanthus had lower tolerance to Cd but a higher tolerance to Zn at higher concentrations. Giant reed and African fodder cane demonstrated stable tolerance across most heavy metals. Accumulation indices highlighted the effectiveness of switchgrass and sorghum in Cd and Pb uptake, while miscanthus excelled in Ni and Zn accumulation. The cluster analysis revealed similar responses to heavy metal stress between African fodder cane and giant reed, as well as between sorghum and miscanthus, with switchgrass displaying distinct behavior. Overall, the study highlights the differential tolerance and accumulation capacities of these crops, indicating the potential for phytoremediation applications and biomass production in heavy metal-contaminated soils. Full article

This work aims to assess the bioavailability and bioaccumulation of Cr, Cu, Pb, and Zn in the soil–plant system (Erigeron canadensis L.) in the zone of anthropogenic impact in Dnipro city, a significant industrial and economic centre of Ukraine. Sampling was carried out at three locations at distances of 1.0 km, 5.5 km, and 12.02 km from the main emission sources associated with battery production and processing plants in Dnipro. The concentrations of heavy metals such as Cr, Cu, Pb, and Zn were analysed using atomic emission spectrometry from soil and parts of Erigeron canadensis L. The highest concentrations of elements in the soil, both for the mobile form and the total form, were determined to be 48.96 mg kg⁻¹ and 7830.0 mg kg⁻¹, respectively, for Pb in experimental plot 1. The general ranking of accumulation of elements in all experimental plots, both for the plant as a whole and for its parts, was as follows: Zn > Cu > Cr > Pb. Zn for plants was the most available heavy metal among all studied sites and had the highest metal content in the plant (339.58 mg kg⁻¹), plant uptake index (PUI-506.84), bioabsorption coefficient (BAC-314.9), and bioconcentration coefficient (BCF-191.94). According to the results of the study, it is possible to evaluate Erigeron canadensis L. as a hyperaccumulator of Zn, Cu, and Cr and recommend it for phytoextraction of soils contaminated with Zn, Cu, and Cr and phytostabilization of soils contaminated with Pb. Full article

The aim of this work was to determine the content of heavy metals in soil and, for the first time, in wild Cortaderia nitida, and to discuss its potential as a metal phytoremediator plant. We sampled sediments (bulk and rhizosphere) and C. nitida (roots and shoots) in three nearby spots with different land uses (urban, industrialized and agricultural) along the Chibunga river basin (Ecuador). We analyzed the physico-chemical parameters in soil and heavy metal contents in soil and plants. The agricultural sediments showed the highest conductivity and redox potential, but the lowest pH. Among all the metals analyzed in soil and plants, we only found significant values of Zn and Fe. We observed clear differences in patterns of Zn distribution throughout soil and plants among the three areas sampled, thus suggesting that soil properties played an important role in Zn compartmentalization. Also, C. nitida demonstrated effective Zn translocation from roots to shoots, especially in farmlands (translocation factors between 1.64 and 2.51). Together with the results obtained for other Cortaderia species in metal-polluted areas, this study proposes C. nitida as a candidate to further study its metal phytoremediation potential and encourages this research in heavy metal-enriched soils. Full article

Although the phytoremediation strategy has been studied worldwide, little research data are available regarding the influence of mycorrhizae on the phytoremediation capacity of various plants grown in Cd-contaminated soils in Mediterranean environments. Therefore, a pot experiment was carried out to study the possible effectiveness of hemp plant (Cannabis sativa L.) in the remediation of moderately and heavily Cd-contaminated soils and additionally to quantify the effect of Cd on Arbuscular Mycorrhizal Fungi (AMFs). For this purpose, an alkaline clay soil collected from the Farm of Institute of Plant Breeding and Genetic Resources (North Greece) was contaminated with two levels of Cd (3 and 30 mg Cd kg⁻¹, corresponding to Levels A and B, respectively—first factor) at two incubation times (10 and 30 days—second factor) and six treatments (Control_30d, Control_10d, CdA_30d, CdB_30d, CdA_10d, CdB_10d) were created. Soil Cd concentrations, both pseudo-total and available to plants, were determined after extraction with Aqua Regia mixture and DTPA solution, respectively, before and after the cultivation of hemp plants and after the harvesting. Cd concentrations in the aboveground and underground plant parts were also estimated after digestion with Aqua Regia, while root colonization by AMFs was determined with a microscope. The highest plant’s Cd concentration, more than 50%, was observed in its underground part, at all Cd-contaminated treatments, indicating a strong capacity for cadmium to gather up in the roots. Among different Cd levels and incubation days, significant differences were recorded in the rates of root colonization by AMFs. Among different Cd levels and incubation days, 3 mg Cd Kg⁻¹ soil promoted AMF root colonization, particularly at 10-day incubation, while 30 mg Cd Kg⁻¹ soil diminished it. Colonization was lower with longer incubation times at both levels of Cd. Hemp appears to be a viable option for phytostabilization in Cd-contaminated soils, enabling further utilization of AMFs to assist the phytoremediation process. Full article