This study investigates the phytoremediation potential of non-productive seedlings of Ailanthus altissima, Acer pseudoplatanus, and Fraxinus excelsior for lead, cadmium, and zinc accumulation in contaminated soils of Zanjan Province, an industrial area with significant pollution. The evaluation employed a completely randomized design, with three treatment levels for each element, alongside a control treatment, replicated three times over a two-year period. A total of 810 one-year-old seedlings from the three species were involved in the study. Soil contamination levels, ranging from 0 to 2000 mg/kg for lead and zinc and from 0 to 200 mg/kg for cadmium, were administered through soil pot irrigation. Sampling of seedling stems and pot soils was conducted in November of 2021 and 2022. The absorption levels of elements in the samples were determined using the dry acid digestion method and an ICP-OES atomic absorption spectrometer. Results indicate species-specific variations in metal absorption, with Ailanthus showing the highest accumulation rates. Findings suggest Ailanthus as a promising candidate for soil improvement in polluted environments, particularly in contaminated soils of Zanjan Province.

Phytoremediation is a rapidly expanding process due to its technical and economic viability. The objective of this work was to evaluate the phytoremediation potential of Helianthus annuus in three cultivation media: artificially contaminated Catalão soil, hydroponics and roadside soil. In hydroponics, ZnCl2 doses 0.32 mgL- 1, 29.94 mgL- 1, 60.06 mgL- 1, 119.94 mgL- 1 were used. While in the artificially contaminated soil, the doses were 0 mgkg- 1, 299 mgkg- 1, 599 mgkg- 1, 1498 mgkg- 1. Physiological analyzes made it possible to demonstrate that treatments T3 and T4, with the highest concentrations of the metal, inhibited growth and promoted darkening of the roots. The highest Zn contents occurred in the aerial part. The results indicated that Helianthus annuus was classified as hyperaccumulator due to its ability to accumulate high levels of Zn mainly in artificially contaminated soil.

Investigating natural processes in arsenic (As) polluted areas and plants that have naturally chosen to grow there pose practical restoration recommendations. This study aimed to assess long-term changes in natural As dendroremediation dynamics for Quercus robur L. and Tilia cordata Mill., tree species capable of growing in areas polluted by mining activities. We examined total As and its forms, as well as B, Ca, K, Mg, Na and P, in soil and trees over 5 years. We also characterized pH and EC of soil, examined proline content in tree organs, and calculated Bioconcentration Factor (BCF) and Translocation Factor (TF) for As. Initial As concentrations in soil were 37.0 mg kg⁻1 under Q. robur and 34.7 mg kg⁻1 under T. cordata, significantly decreasing after 5 years to 10.5 mg kg⁻1 and 9.51 mg kg⁻1, respectively. This corresponds to pollution reduction of up to 71.8%. A notable decrease in As(III) and dimethylarsinic acid, along with increase in other organic As forms in soil, was observed. Additionally, concentrations of essential elements in soil, as well as its pH and EC, decreased over time. Both tree species accumulated substantial amounts of As in their organs, but the dynamics of this process were species-specific. During first 4 years, T. cordata accumulated more As and exhibited higher BCF, but in the 5th year, it was clearly surpassed by Q. robur. The highest TF was calculated for Q. robur in year 3, and for T. cordata in years 2 and 3. Generally, limited aboveground movement of As was indicated: BCF >1 were calculated for years 2 and 3, while TF were consistently <1. Proline content increased significantly in all organs, correlating with As, especially in Q. robur. In contrast, Q. robur leaves mapping revealed stable macroelement distributions, but clear variations were observed for T. cordata., which may suggest specific reaction to stress. These findings suggest that both species can effectively restore As-polluted areas, though with different dynamics. The selection of species for dendrorestoration should be based on whether the goal is faster remediation with lesser overall reduction (e.g. T. cordata) or slower remediation with ultimately greater pollution reduction (e.g. Q. robur).

Metal contamination in soil poses a significant environmental concern worldwide, necessitating effective remediation strategies such as phytoremediation. The present study investigated the effects of EDTA dosage (1.5 and 3 mmol kg-1) and two Trichoderma species (T. harzianum and T. aureoviride) on copper (Cu) content and growth of maize plants grown in a Cu-contaminated soil, as well as Cu fractionation in the soil. In the absence of EDTA, only inoculation with T. harzianum led to a significant increase in shoot biomass. Combining fungal inoculum with EDTA only yielded a significant increase in shoot biomass when using T. aureoviride at a low EDTA rate, highlighting the interplay between fungal species and EDTA rates on plant growth. Results also indicated that EDTA application increased Cu bioavailability, enhancing Cu dissolution and root (not shoot) Cu concentrations. Conversely, inoculation with both Trichoderma species reduced Cu mobility and bioavailability in soil, thereby decreasing the shoot Cu concentrations of plants. When combined with EDTA, only application of T. harzianum resulted in an enhanced shoot Cu concentration, whereas combined application of T. aureoviride and EDTA did not make a significant change compared to the corresponding control (no fungal inoculation, no EDTA), possibly due to a lower compatibility of the T. aureoviride isolate with EDTA. Our results demonstrated that EDTA application, in both non-inoculated and inoculated treatments, increased Cu availability by facilitating its redistribution and transformation from less plant-available fractions (residual, Fe/Mn oxide-bound, and carbonate-bound) to the more readily plant-available forms (water-soluble and exchangeable fractions). In conclusion, although individual Trichoderma application proved beneficial for phytostabilization by reducing Cu content and mitigating Cu toxicity in plants, the combined application of EDTA and a compatible Trichoderma isolate (here, the T. harzianum isolate) holds promise for enhancing the phytoextraction capacity of plants. Although using maize has the advantage of being a food crop, to optimize phytoextraction, plant species with superior metal tolerance and phytoextraction capabilities should be selected, exceeding those of maize.

Landscape utilization is a green and environment-friendly way of disposing of compost sludge. Garden plants can extract heavy metals from the sludge of land use, but the effect is not enough to be widely used. Chelating agents have been found to facilitate the extraction of heavy metals from plants and are expected to be popularized if they are also environmentally friendly. In this study, the effects of methylglycinediacetic acid trisodium salt (MGDA), tetrasodium glutamate diacetate (GLDA), and ethylene diamine tetraacetate (EDTA) on the extraction of Ni and Cd from compost sludge by Symphytum officinale L. were studied through the pot experiment. Compared with the control group, the application of 5-10 mmol kg-1 MGDA and 1-9 mmol kg-1 GLDA promoted plant growth, while the application of 3-4 mmol kg-1 EDTA inhibited plant growth. The highest Ni content in shoots appeared in 4 mmol kg-1 GLDA treatment, which was 4.2 times that of the CK group. The highest shoot Cd concentration appeared in 4 mmol kg-1 EDTA treatment, 6.5 times that of CK. The promotion effects of the three reagents on the acid-extractable state of Cd were similar, while that of GLDA on the acid-extractable state of Ni was outstanding. The results of this study suggested that S. officinale could be a potential phytoextraction plant for Cd and Ni, and GLDA could friendly promote the Ni phytoextraction ability of the plant. The study provides a new and efficient method for phytoremediation of heavy metals in soil.

This greenhouse study evaluated the effects of soil enrichment with Pteris vittata rhizosphere bacteria on the growth and accumulation of arsenic in P. vittata grown on a naturally As-rich soil. Inoculations were performed with a consortium of six bacteria resistant to 100 mM arsenate and effects were compared to those obtained on the sterilized soil. Selected bacteria from the consortium were also utilized individually: PVr_9 homologous to Agrobacterium radiobacter that produces IAA and siderophores and shows ACC deaminase activity, PVr_15 homologous to Acinetobacter schindleri that contains the arsenate reductase gene, and PVr_5 homologous to Paenarthrobacter ureafaciens that possesses all traits from both PVr_9 and PVr_15. Frond and root biomass significantly increased in ferns inoculated with the consortium only on non-sterilized soil. A greater increase was obtained with PVr_9 alone, while only an increased root length was found in those inoculated with either PVr_5 or PVr_15. Arsenic content significantly decreased only in ferns inoculated with PVr_9 while it increased in those inoculated with PVr_5 and PVr_15. In conclusion, inoculations with the consortium and PVr_9 alone increase plant biomass, but no increase in As phytoextraction occurs with the consortium and even a reduction is seen with PVr_9 alone. Conversely, inoculations with PVr_5 and PVr_15 have the capacity of increasing As phytoextraction.

Phytoremediation is a useful, low-cost, and environmentally friendly alternative for the rehabilitation of heavy-metal-contaminated (HM) soils. This technology takes advantage of the ability of certain plant species to accumulate HMs in their tissues. Crotalaria pumila is a herbaceous plant with a wide geographical distribution that grows naturally in environments polluted with HMs. In this work, the bioaccumulation capacity of roots and leaves in relation to five HMs (Cr, Cu, Fe, Pb, and Zn) was evaluated, as well as the morphological changes presented in C. pumila growing in control substrate (without HMs) and mine-tailing substrate (with HMs) under greenhouse conditions for 150 days. Four metals with the following concentration pattern were detected in both tissues and substrates: Fe > Pb > Cu > Zn. Fe, Pb, and Zn concentrations were significantly higher in the roots and leaves of individuals growing on mine-tailing substrate compared to the control substrate. In contrast, Cu concentration increased over time in the exposed individuals. The bioconcentration factor showed a similar pattern in root and leaf: Cu > Fe > Pb > Zn. Around 87.5% of the morphological characters evaluated in this species decreased significantly in individuals exposed to HMs. The bioconcentration factor shows that C. pumila is efficient at absorbing Cu, Fe, and Pb from the mine-tailing substrate, in the root and leaf tissue, and the translocation factor shows its efficiency in translocating Cu from the roots to the leaves. Therefore, C. pumila may be considered as a HM accumulator plant with potential for phytoremediation of polluted soils with Cu, Pb, and Fe, along with the ability to establish itself naturally in contaminated environments, without affecting its germination rates. Also, it exhibits wide geographical distribution, it has a short life cycle, exhibits rapid growth, and can retain the mine-tailing substrate, extracting HMs in a short time.

Heatwaves, expected to become more frequent, pose a significant threat to plant biomass production. This experiment was designed to estimate heatwave influence on Brassica juncea phytoremediation when superimposed on different CO2 levels. A 7-day heatwave was generated during the species flowering stage. Heatwaves decreased all B. juncea dry weights. The lowest species dry weight was recorded when the heatwave was accompanied by 250 ppm CO2, in which the biomass significantly decreased by 40.0% relative to that of no heatwave under the same atmospheric CO2 conditions. Heatwave superposition with 250 ppm CO2 reduced the Cd content in B. juncea aerial parts by 28.1% relative to that of identical environmental conditions without heatwave, whereas the opposite result was observed under 550 ppm CO2 conditions. The heatwave caused oxidative damage to B. juncea under all CO2 conditions, as manifested by increased malondialdehyde levels in the plant shoots. With heatwave superposition, antioxidant enzyme activity was enhanced by exposure to 400 and 550 ppm CO2. Considering biomass yield generation and Cd uptake capacity, heatwave superposition decreased the B. juncea phytoremediation effects, and high atmospheric CO2 conditions could alleviate detrimental effects to a certain extent. This study uniquely examines the combined effects of heatwaves and varying CO2 levels on phytoremediation, providing microscopic insights into oxidative damage and enzyme activity, highlighting the potential for CO2 enrichment to mitigate heatwave impacts, and offering comprehensive analysis for future agricultural practices and environmental management.

Using contaminated land to grow lignocellulosic crops can deliver biomass and, in the long term, improve soil quality. Biostimulants and microorganisms are nowadays an innovative approach to define appropriate phytomanagement strategies to promote plant growth and metal uptake. This study evaluated biostimulants and mycorrhizae application on biomass production and phytoextraction potential of four lignocellulosic crops grown under two metal-contaminated soils. Two greenhouse pot trials were setup to evaluate two annual species (sorghum, hemp) in Italy and two perennial ones (miscanthus, switchgrass) in China, under mycorrhizae (M), root (B2) and foliar (B1) biostimulants treatments, based on humic substances and protein hydrolysates, respectively, applied both alone and in combination (MB1, MB2). MB2 increased the shoot dry weight (DW) yield in hemp (1.9 times more), sorghum (3.6 times more) and miscanthus (tripled) with additional positive effects on sorghum and miscanthus Zn and Cd accumulation, respectively, but no effects on hemp metal accumulation. No treatment promoted switchgrass shoot DW, but M enhanced Cd and Cr shoot concentrations (+84%, 1.6 times more, respectively) and the phytoextraction efficiency. Root biostimulants and mycorrhizae were demonstrated to be more efficient inputs than foliar biostimulants to enhance plant development and productivity in order to design effective phytomanagement strategies in metal-contaminated soil.

The focus on phytoremediation in soil cadmium (Cd) remediation is driven by its cost-effectiveness and eco-friendliness. Selecting suitable hyperaccumulators and optimizing their growth conditions are key to enhance the efficiency of heavy metal absorption and accumulation. Our research has concentrated on the role of salicylic acid (SA) and jasmonic acid (JA) in facilitating Cd phytoextraction by \"Sedum alfredii (S. alfredii)\" through improved soil-microbe interactions. Results showed that SA or JA significantly boosted the growth, stress resistance, and Cd extraction efficiency in S. alfredii. Moreover, these phytohormones enhanced the chemical and biochemical attributes of the rhizosphere soil, such as pH and enzyme activity, affecting soil-root interactions. High-throughput sequencing analysis has shown that Patescibacteria and Umbelopsis enhanced S. alfredii\'s growth and Cd extraction by modifying the bioavailability and the chemical conditions of Cd in soil. Structural Equation Model analysis further verified that phytohormones significantly enhanced the interaction between S. alfredii, soil, and microbes, leading to a marked increase in Cd accumulation in the plant. These discoveries emphasized the pivotal role of phytohormones in modulating the hyperaccumulators\' response to environmental stress and offered significant scientific support for further enhancing the potential of hyperaccumulators in ecological restoration technologies using phytohormones.