Search

In Chile, the budget for managing environmental liabilities such as abandoned tailings impoundments is limited. Using native and endemic plant species to remove heavy metals from tailings represents a low-cost alternative. Ex situ phytoremediation experiments were conducted over a period of seven months. The endemic species Lycium chilense and native species Haplopappus foliosus were used to remove copper and lead from mine tailings. The results indicate that both species can concentrate levels of Cu and Pb higher than the toxicity threshold in the roots and aerial parts, and present high removal efficiency for Cu higher than 50%. In both species, the concentrations of the target elements are higher in the roots than in the aerial parts. Haplopappus foliosus presents the best performance, accumulating higher concentrations of Cu and Pb than Lycium chilense, and presenting a bioconcentration of over one for Cu. [ABSTRACT FROM AUTHOR]

Phytoextraction is a promising technology for remediating heavy metal-contaminated soil. Continuously screening potential plants is important for enhancing the efficiency of remediation. In this study, fourteen local native plant species and four cultivated plant species, along with their paired soils, were collected from around a copper smelter. The characteristics of soil pollution were evaluated using contaminant factors (CF) and a geoaccumulation index (Igeo). The phytoextraction potential of plants was investigated using the translocation factor (TF) and bioconcentration factor (BCF). The soils around the smelter were very acidic, with a mean pH of 5.01. The CF for copper and cadmium were 8.67–32.3 and 5.45–44.2, and the Igeo values for copper and cadmium were 2.43–4.43 and −0.12–2.29, respectively, indicating that the level of soil contamination was moderate to severe. The copper concentrations in the root (357 mg/kg), shoot (219 mg/kg), and leaf (269 mg/kg) of Elsholtzia splendens Nakai were higher than that in the other species. The cadmium in the shoot (32.2 mg/kg) and leaf (18.5 mg/kg) of Sedum plumbizincicola was the highest, and Phytolacca acinosa Roxb. had the highest cadmium level (20 mg/kg) in the root. Soil total and CaCl2-extractable copper and cadmium were positively correlated with copper and cadmium in the plant roots, respectively. The results of TF and BCF for copper and cadmium suggested that the accumulation and translocation capacities for cadmium were higher than those of copper in the eighteen plant species. Although not all plants met the criteria of being hyperaccumulators, Sedum plumbizincicola, Mosla chinensis Maxim, and Elsholtzia splendens Nakai showed the most potential as candidates for the phytoextraction of copper and cadmium contaminated soils, as indicated by their TF and BCF values. [ABSTRACT FROM AUTHOR]

In soil with extremely high contents of Cd (101.87), Pb (26,526.44), and Zn (17,652.63 mg kg−1), we aimed to test the phytostabilization capacity of purslane (Portulaca oleracea) with the use of various soil improvers, both organic (biochar, compost, insect frass) and inorganic (lime and zeolite). Thus, in a 60-day pot experiment, we amended this heavily contaminated soil with the five materials at two rates, 2% and 4%, resulting in 11 treatments (control plus five materials × two rates) replicated 10 times. We found that soil extractions of Cd with DTPA (diethylenetriaminepentaacetic acid) were not affected by any of the amendments, as there was no recorded significant reduction in soil Cd. In the case of Pb, there were even significant increases in its extractability with added biochar, and so was the case for compost at 4%. The reason may be the formation of organometallic complexes with organic substances of low molecular weight eluted by the organic amendments. Similarly, Zn extractability increased significantly compared to the control in the compost and frass treatments. As for purslane shoots, Cd decreased from 61 μg kg−1 fresh weight (FW) at control to 39 at biochar 4%, but the reduction was non-significant. As for Pb, it decreased with biochar but not significantly, while it exhibited a significant decrease in all other treatments. However, in all cases the content of Pb in purslane was well above the European regulation limit of 0.100 mg kg−1 FW (fresh weight) for vegetables and fresh herbs, while Cd fell below the regulation limit of 50 μg kg−1 FW at biochar 4%, compost 4%, and frass 2% and 4% (with control being 62.5 μg kg−1 FW). We conclude that in heavily contaminated soils, although biochar, along with compost and frass, was not entirely unsuccessful, the tested amendments did not reduce satisfactorily toxic elements to sufficiently low levels both in soil and in the test plant (here, purslane) in order to achieve phytostabilization. However, further research is necessary to identify exact mechanisms and to elucidate the role of different biochars. [ABSTRACT FROM AUTHOR]

Plants with high biomass adapted to conditions of increased moisture and with significant salt tolerance appear to be particularly attractive candidates for phytoremediation studies. The aim of the present study was to examine the tolerance of Rumex hydrolapathum plants to freshwater, saltwater inundation, and soil contaminated with heavy metals, as well as its metal accumulation potential in controlled conditions. Six separate vegetation container experiments in controlled conditions were performed with R. hydrolapathum plants to study the effects of soil moisture, waterlogging with NaCl, soil Cd, soil Cr, soil Ni, and soil Pb in the form of a nitrate or acetate. Optimum plant growth occurred in waterlogged soil conditions. As the concentration of NaCl used for waterlogging increased, the mass of living leaves decreased, but that of dry leaves increased. As a result, the total biomass of leaves did not significantly change. R. hydrolapathum plants were extremely tolerant to Cd and Pb, moderately tolerant to Ni, and relatively sensitive to Cr. The plants had high capacity for metal accumulation in older and senescent leaves, especially for Na+, K+, Cd, and Ni. R. hydrolapathum plants can tolerate soil waterlogging with seawater-level salinity, which, together with the metal tolerance and potential for metal accumulation in leaves, make them excellently suited for use in a variety of wastewater treatment systems, including constructed wetlands. [ABSTRACT FROM AUTHOR]

The development of large-scale mining activity along the Central Andes of Argentina (CAA) has generated significant amounts of waste materials containing heavy metals. Phytoremediation is a promising eco-friendly, low-cost, and effective technology for the removal of heavy metals. The present study aimed to identify two native dominant species from the CCA, Adesmia subterranea and A. pinifolia, as metal-tolerant plant species for the first time, by evaluating the germination and early seedling growth at different concentrations (ppm) of Cd (3, 4.5 and 6), Ni (150, 225 and 300), As (20, 30 and 40), and Hg (0.8, 1.2 and 1.6) Early seedling growth was found to be more sensitive to heavy metals than germination. Ni and As exhibited the greatest inhibitory effect on both species' germination percentages. In contrast, with Cd and Hg, no inhibitory effect was recorded. Root length, metal tolerance index, and fresh and dry weight were stimulated with Hg. However, the phytotoxic effect was greater as the concentration of Ni, As, and Cd increased. As an overall conclusion, the order of toxicity for these species can be classified as Ni > As > Cd > Hg. Therefore, Adesmia species could be considered as candidates for phytoremediation of soils contaminated with Hg and low concentrations of Cd. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) have been shown to assist plants in increasing metal tolerance and accumulation in heavy metal (HM)-contaminated soils. Herein, a greenhouse pot experiment was conducted to assess the interactions of growth substrates (S1, S2, and S3, respectively) with various HM contamination and nutrient status sampling from a typical contaminated soil and tailings in Shuikoushan lead/zinc mining in Hunan province, China, and AMF inoculation obtained from plants in uncontaminated areas (Glomus mosseae, Glomus intraradices, and uninoculated, respectively) on the biomass and uptake of HMs and phosphorus (P) by the black locust plant (Robinia pseudoacacia L.). The results indicated that the inoculation with AMF significantly enhanced the mycorrhizal colonization of plant roots compared with the uninoculated treatments, and the colonization rates were found to be higher in S1 and S2 compared with S3, which were characterized with a higher nutrient availability and lead concentration. The biomass and heights of R. pseudoacacia were significantly increased by AMF inoculation in S1 and S2. Furthermore, AMF significantly increased the HM concentrations of the roots in S1 and S2 but decreased the HM concentrations in S3. Shoot HM concentrations varied in response to different AMF species and substrate types. Mycorrhizal colonization was found to be highly correlated with plant P concentrations and biomass in S1 and S2, but not in S3. Moreover, plant biomass was also significantly correlated with plant P concentrations in S1 and S2. Overall, these findings demonstrate the interactions of AMF inoculation and growth substrates on the phytoremediation potential of R. pseudoacacia and highlights the need to select optimal AMF isolates for their use in specific substrates for the remediation of HM-contaminated soil. [ABSTRACT FROM AUTHOR]

In the age of industrialization, numerous non-biodegradable pollutants like plastics, HMs, polychlorinated biphenyls, and various agrochemicals are a serious concern. These harmful toxic compounds pose a serious threat to food security because they enter the food chain through agricultural land and water. Physical and chemical techniques are used to remove HMs from contaminated soil. Microbial-metal interaction, a novel but underutilized strategy, might be used to lessen the stress caused by metals on plants. For reclaiming areas with high levels of heavy metal contamination, bioremediation is effective and environmentally friendly. In this study, the mechanism of action of endophytic bacteria that promote plant growth and survival in polluted soils—known as heavy metal-tolerant plant growth-promoting (HMT-PGP) microorganisms—and their function in the control of plant metal stress are examined. Numerous bacterial species, such as Arthrobacter, Bacillus, Burkholderia, Pseudomonas, and Stenotrophomonas, as well as a few fungi, such as Mucor, Talaromyces, Trichoderma, and Archaea, such as Natrialba and Haloferax, have also been identified as potent bioresources for biological clean-up. In this study, we additionally emphasize the role of plant growth-promoting bacteria (PGPB) in supporting the economical and environmentally friendly bioremediation of heavy hazardous metals. This study also emphasizes future potential and constraints, integrated metabolomics approaches, and the use of nanoparticles in microbial bioremediation for HMs. [ABSTRACT FROM AUTHOR]

The restoration of polluted soils is crucial for ecosystem recovery services. Evidently, phytoremediation is a biological and sustainable technique that includes the use of plants to remediate heavy-metal-contaminated land; the plants should be tolerant to the contamination and capable of uptake or immobilization of the heavy metals in the soil. Moreover, defining an economically efficient approach to the remediation of a contaminated area, with the possibility of further utilization of phytoremediation biomass, renders energy crops a great option for this technique. Energy crops, in fact, are known for their ability to grow with low agricultural input, and later, the biomass product can be used to produce biofuels, bioenergy, and bioproducts in a sustainable and renewable way, creating economic potential, especially when these crops are cultivated in marginal lands. The aim of this work is to test two monoecious industrial hemp varieties in different levels of Cd, Pb, and Ni in soil. Both varieties were tolerant to levels of Cd and Pb contamination that were higher than the limit for commercial and industrial use, while Ni showed a significant effect at all the tested concentrations. The variety Futura 75 performed better than Kc Dora in terms of productivity and tolerance. [ABSTRACT FROM AUTHOR]

Fifteen riparian populations of Lithuanian Lythrum salicaria were assessed for leaf macronutrient, micronutrient and non-essential element concentrations and compared to the former obtained molecular data at amplified fragment length polymorphism (PLP.AFLP) loci. Inductively coupled plasma mass spectrometry was used to profile the contents of 12 elements in the leaves. The leaf nutrient concentrations were within normal ranges for growth and development and heavy metal concentrations did not reach toxic levels. The concentrations of macroelements such as nitrogen, potassium, calcium and magnesium were in the range of 23,790–38,183; 7327–11,732; 7018–12,306; and 1377–3183 µg/g dry mass (d. m.), respectively; the concentrations of micronutrients such as sodium, iron, zinc and copper varied in the ranges of 536–6328; 24.7–167.1; 10.88–26.24; and 3.72–5.30 µg/g d. m., respectively, and the concentrations of non-essential elements such as lead, nickel, chromium, and cadmium were in the intervals of 0.136–0.940; 0.353–0.783; 0.207–0.467; and 0.012–0.028 µg/g d. m., respectively. When comparing the maximum and minimum values for site elements of L. salicaria, the concentration of N varied by 1.6, K—1.6, Ca—1.8, Mg—2.3, Na—6.1, Fe—6.8, Zn—2.4, Cu—1.5, Pb—6.9, Ni—2.2, Cr—2.2, and Cd—2.3 times. The coefficient of variation (CV) of element concentrations in sites was moderate to large: N—15.4%, K—14.3%, Ca—18.6%, Mg—24.8%, Na—50.7%, Fe—47.0%, Zn—24.9%, Cu—14.5%, Pb—57.1%, Ni—30.11%, Cr—26.0%, and Cd—38.6%. Lythrum salicaria populations growing near regulated riverbeds were characterized by significantly (p < 0.05) lower concentrations of Ca and Mg, and significantly (p < 0.05) higher concentrations of N, K, Fe, Na, Ni, Cr and Cd. The PLP.AFLP was negatively correlated with concentrations of N, Na, Fe, Ni, Cr, and Cd. The L. salicaria population with the lowest leaf N and Na concentration showed the highest genetic polymorphism (PLP.AFLP = 65.4%), while the least polymorphic population (PLP.AFLP = 35.0%) did not show extreme concentrations of either element. In conclusion, our elemental analysis of L. salicaria populations showed that ionomic parameters are related to genomic parameters, and some habitat differences are reflected in the ionomes of the populations. [ABSTRACT FROM AUTHOR]

Heavy metals and flooding are among the primary environmental factors affecting plants and microorganisms. This review separately considers the impact of heavy metal contamination of soils on microorganisms and plants, on plant and microbial biodiversity, and on plant–microorganism interactions. The use of beneficial microorganisms is considered one of the most promising methods of increasing stress tolerance since plant-associated microbes reduce metal accumulation, so the review focuses on plant–microorganism interactions and their practical application in phytoremediation. The impact of flooding as an adverse environmental factor is outlined. It has been shown that plants and bacteria under flooding conditions primarily suffer from a lack of oxygen and activation of anaerobic microflora. The combined effects of heavy metals and flooding on microorganisms and plants are also discussed. In conclusion, we summarize the combined effects of heavy metals and flooding on microorganisms and plants. [ABSTRACT FROM AUTHOR]

Symbiotic associations with arbuscular mycorrhizal fungi (AMF) offer an effective indirect mechanism to reduce heavy metal (HM) stress; however, it is still not clear which AMF species are more efficient as bioremediating agents. We selected different species of AMF: Rhizoglomus custos (Custos); Rhizoglomus sp. (Aznalcollar); and Rhizophagus irregularis (Intraradices), in order to study their inoculation in wheat grown in two soils contaminated with two levels of HMs; we tested the phytoprotection potential of the different AMF symbioses, as well as the physiological responses of the plants to HM stress. Plants inoculated with indigenous Aznalcollar fungus exhibited higher levels of accumulation, mainly in the shoots of most of the HM analyzed in heavily contaminated soil. However, the plants inoculated with the non-indigenous Custos and Intraradices showed depletion of some of the HM. In the less-contaminated soil, the Custos and Intraradices fungi exhibited the greatest bioaccumulation capacity. Interestingly, soil enzymatic activity and the enzymatic antioxidant systems of the plant increased in all AMF treatments tested in the soils with both degrees of contamination. Our results highlight the different AMF strategies with similar effectiveness, whereby Aznalcollar improves phytoremediation, while both Custos and Intraradices enhance the bioprotection of wheat in HM-contaminated environments. [ABSTRACT FROM AUTHOR]

The phenomenon of cross adaptation refers to the ability of plants to improve their resistance to other stress after experiencing one type of stress. However, there are limited reports on how ultraviolet radiation B (UVB) pretreatment affects the enrichment, transport, and tolerance of cadmium (Cd) in plants. Since an appropriate UVB pretreatment has been reported to change plant tolerance to stress, we hypothesized that this application could alter plant uptake and tolerance to heavy metals. In this study, a woody plant species, 84K poplar (Populus alba × Populus glandulosa), was pretreated with UVB and then subjected to Cd treatment. The RT-qPCR results indicated that the UVB-treated plants could affect the expression of Cd uptake, transport, and detoxification-related genes in plants, and that the UVB-Pretreatment induced the ability of Cd absorption in plants, which significantly enriched Cd accumulation in several plant organs, especially in the leaves and roots. The above results showed that the UVB-Pretreatment further increased the toxicity of Cd to plants in UVB-Cd group, which was shown as increased leaf malonaldehyde (MDA) and hydrogen peroxide (H2O2) content, as well as downregulated activities of antioxidant enzymes such as Superoxide Dismutase (SOD), Catalase (CAT), and Ascorbate peroxidase (APX). Therefore, poplar plants in the UVB-Cd group presented a decreased photosynthesis and leaf chlorosis. In summary, the UVB treatment improved the Cd accumulation ability of poplar plants, which could provide some guidance for the potential application of forest trees in the phytoremediation of heavy metals in the future. [ABSTRACT FROM AUTHOR]

The novelty of the present research consisted in the study of the features of heavy metals accumulation in the phytomass of agricultural plants under the conditions of complex heavy metals contamination of podzolized chernozem (ashy soil) in the Ryazan region (Russia). Results of the vegetation experiments conducted on four crops—oats, black beans, buckwheat, and soybeans—were analyzed, which made it possible to assess the ability of these plants to accumulate heavy metals in their phytomass depending on the level of the heavy metals contamination of the soil. Results of the study showed that the removal of copper, zinc, and lead by beans was noticeably higher than that by oats, buckwheat and soy, due to their greater tolerance and ability to form a large phytomass, which must be taken into consideration when choosing phytoremediation for soil decontamination. This made it possible to evaluate the possibility of using the analyzed plants for the biological purification of polluted soil. The results are also planned to be used in the digitalization of agricultural production. [ABSTRACT FROM AUTHOR]

Growing awareness of the risks posed by pollution of the soil environment is leading to the development of new remediation strategies. The technique of aided phytostabilization, which involves the evaluation of new heavy-metal (HM)-immobilizing amendments, together with appropriately selected plant species, is a challenge for environmental protection and remediation of the soil environment, and seems to be promising. In this study, the suitability of bentonite for the technique of aided phytostabilization of soils contaminated with high HM concentrations was determined, using a mixture of two grass species. The HM contents in the tested plants and in the soil were determined by flame atomic absorption spectrometry. The application of bentonite had a positive effect on the biomass of the tested plants, and resulted in an increase in soil pH. The concentrations of copper, nickel, cadmium, lead and chromium were higher in the roots than in the above-ground parts of the plants, especially when bentonite was applied to the soil. The addition of the analyzed soil additive contributed significantly to a decrease in the levels of zinc, copper, cadmium and nickel in the soil at the end of the experiment. In view of the above, it can be concluded that the use of bentonite in the aided phytostabilization of soils polluted with HMs, is appropriate. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate tolerance to salinity and different heavy metals as well as the phytoextraction potential of Ranunculus sceleratus plants from a brackish coastal sandy beach habitat. Four separate experiments were performed with R. sceleratus plants in controlled conditions: (1) the effect of NaCl gradient on growth and ion accumulation, (2) the effect of different Na+ and K+ salts on growth and ion accumulation, (3) heavy metal tolerance and metal accumulation potential, (4) the effect of different forms of Pb salts (nitrate and acetate) on plant growth and Pb accumulation. A negative effect of NaCl on plant biomass was evident at 0.5 g L−1 Na+ and growth was inhibited by 44% at 10 g L−1 Na+, and this was associated with changes in biomass allocation. The maximum Na+ accumulation (90.8 g kg−1) was found in the stems of plants treated with 10 g kg−1 Na+. The type of anion determined the salinity tolerance of R. sceleratus plants, as Na+ and K+ salts with an identical anion component had a comparable effect on plant growth: nitrates strongly stimulated plant growth, and chloride treatment resulted in slight but significant growth reduction, but plants treated with nitrites and carbonates died within 4 and 5 weeks after the full treatment, respectively. The shoot growth of R. sceleratus plants was relatively insensitive to treatment with Mn, Cd and Zn in the form of sulphate salts, but Pb nitrate increased it. Hyperaccumulation threshold concentration values in the leaves of R. sceleratus were reached for Cd, Pb and Zn. R. sceleratus can be characterized as a shoot accumulator of heavy metals and a hyperaccumulator of Na+. A relatively short life cycle together with a high biomass accumulation rate makes R. sceleratus useful for dynamic constructed wetland systems aiming for the purification of concentrated wastewaters. [ABSTRACT FROM AUTHOR]

A formidable challenge in suburban agriculture is the sustainability of soil health following the use of wastewater for irrigation. The wastewater irrigation likely toxifies the crop plants making them unconsumable. We used a multivariate, completely randomized design in a greenhouse, comparing the phytoextraction capacities of Brassica juncea, Eruca sativa, Brassica rapa, and Brassica napus—all grown on silt loam soil irrigated with industrial wastewater, canal water, and a 1:1 mixture, during 2018. The studied Brassica plants were generally closely efficient in remediating toxic metals found in wastewater irrigated soil. Substantial differences between Brassica and Eruca plants/parts were recorded. For example, B. napus had significantly higher metal extraction or accumulation compared to E. sativa for Zn (71%), Cu (69%), Fe (78%), Mn (79%), Cd (101%), Cr (57%), Ni (92%). and Pb (49%). While the water and plant were the main predictors of metal extraction or accumulation, an interaction between the main effects substantially contributed to Cu, Mn, and Fe extractions from soil and accumulations in plants. Significant correlations between biological accumulation coefficient and biological transfer coefficient for many metals further supported the metal extraction or accumulation efficiencies as: B. napus > B. juncea > B. rapa > E. sativa. Root-stem mobility index correlation with stem-leaf mobility index indicated the metal translocation along the root-stem-leaf continuum. Therefore, we suggest that these crops may not be used for human or animal consumption when grown with industrial wastewater of toxic metal concentrations ≥ permissible limits. Rather these plants may serve as effective remediators of toxic metal-polluted soil. [ABSTRACT FROM AUTHOR]

The main objective of this study was to investigate whether the most common wild plant species of urban grassland can be used for phytoremediation of soils polluted with heavy metals. The study was conducted in the city of Varaždin, in northern Croatia. The content of heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, Zn) was determined in soil samples as well as in unwashed and washed plant samples (Taraxacum officinale, Plantago lanceolata, Trifolium repens). The results show that the most polluted site is the railway station, while most sites are polluted by road traffic. The soils are most enriched with Pb, Cu, Zn and Cd. The bioconcentration factors for all three plant species are <1, indicating the relatively low capacity of phytoextraction. A considerable amount of heavy metals is found in the dust deposited on the plant surface, which is confirmed by a statistically significant difference between washed and unwashed plant samples. In addition, the biomass of each plant species that can be removed (in t/ha year), the mass of specific heavy metal that can be removed (in kg/ha), and the years required for phytoremediation are reported. In conclusion, phytoremediation with only common plant species of urban grassland is not possible within a reasonable period of time. [ABSTRACT FROM AUTHOR]

Soil and air pollution are main problems posing a serious threat to human health. Traditional physical and chemical soil remediation methods affect the soil ecosystem and are rather costly. Since the main purpose of soil remediation is not only to remove pollutants but also to restore soil health, the method of phytoremediation is becoming extremely relevant. Phytoremediation is an environmentally friendly and natural process of removing pollutants from the environment. Cleaning up contaminated sites and enabling re-use without harming future users requires the implementation of environmentally friendly and economically attractive technologies. Phytoremediation does not adversely affect the structure and biological life of the soil. Concerning on-site cleaning in situ. Hyperaccumulator plants can accumulate heavy metals from the soil, which is the so-called phytoextraction. The ability of trees and shrubs to effectively remove solid particles from the air has also been proven. However, it is not always possible to grow large plants in polluted areas. Therefore, the main goal of the research was to explore previous studies on the phytoremediation capability of herbaceous plants, in particular, their phytoextraction capacity. Another major issue was to study the main methods of improving plant phytoextraction. The results obtained show that grass can be a good solution for natural ecosystem cleanup. It is also necessary to pay attention to the impact of phytoextraction-improving substances on soil health. [ABSTRACT FROM AUTHOR]

The promotion and gradual replacement of fossil fuels with renewable sources increasing the competition between food and fuel. Therefore, energy crops could be produced on unproductive marginal land due to unfavorable conditions, such as limitations in nutrient and water availability or the presence of contaminants such as hydrocarbons or heavy metals. In the case of soils contaminated with heavy metals, one option could be the use of plants to extract or immobilize the contaminants in the soil in a process called phytoremediation. Carthamus tinctorius L. is an annual herbaceous plant with a deep root system, and the oil extracted from the seeds is an excellent oil for conversion into biofuel. It appears suitable to be used in the phytoremediation process, increasing the opportunity to valorize polluted areas and reducing the risk of abandonment of these lands. In this study, C. tinctorius was tested in soils contaminated with zinc, cadmium, lead, and nickel at different concentrations to evaluate the effects on yield and heavy metal content in the different parts of the plant. The experiment highlights the tolerance of Safflower to the cultivation in heavy-metal-polluted soil; in fact, a low reduction in biomass yield was observed. Among the evaluated heavy metals, the higher susceptibility was observed at the highest concentrations of zinc and cadmium. Generally, safflower concentrates heavy metals in the belowground biomass. The relative low concentrations of heavy metals in some parts of the aboveground biomass could suggest the possibility of using it as a feedstock for bioenergy conversion. [ABSTRACT FROM AUTHOR]

Physiological, agricultural and toxicological impact of an excess of Zn in the soil is an important issue, as Zn is a heavy metal and impairs many processes of plants and animals. The novelty of this work is that it is a comprehensive approach to facilitate visualization not only of the condition of cabbage plants under Zn stress, but also prediction of the toxicity associated with consumption of such cabbages. We treated plants of two cabbage cultivars, differing in their earliness, with 50 and 200 mg Zn kg−1 soil (Zn50 and Zn200, respectively) above the natural Zn levels of 118.13 mg kg−1 soil (Zn0). Leaf cell membrane integrity, condition of the photosynthetic apparatus (reflected by relative chlorophyll content (SPAD) and Fv/Fm parameter of chlorophyll a fluorescence), head biomass, and Zn bioaccumulation in the heads were analyzed. Toxicological risk was also assessed by Daily Intake of Metal (DIM) and Health Risk Index (HRI) indicators. The data revealed that plants of the late cultivar were more sensitive to soil Zn than those of the early one. Detrimental effects of Zn (especially at the higher dose, Zn200) were manifested in the seedlings just after three weeks of treatment, and then reflected in the yield. We assume that, due to their fast and prolonged response to Zn, the seedlings of the late cultivar can be used as biomarkers of Zn toxicity. Although Zn plants did not indicate toxicological risk, based on DIM and HRI, Zn concentration in the soil should be taken into account prior to cabbage planting, because plants which do not reveal symptoms of injury can accumulate Zn above the permissible level. [ABSTRACT FROM AUTHOR]

The main mechanism of plant tolerance is the avoidance of metal uptake, whereas the main mechanism of hyperaccumulation is the uptake and neutralization of metals through specific plant processes. These include the formation of symbioses with rhizosphere microorganisms, the secretion of substances into the soil and metal immobilization, cell wall modification, changes in the expression of genes encoding heavy metal transporters, heavy metal ion chelation, and sequestration, and regenerative heat-shock protein production. The aim of this work was to review the natural plant mechanisms that contribute towards increased heavy metal accumulation and tolerance, as well as a review of the hyperaccumulator phytoremediation capacity. Phytoremediation is a strategy for purifying heavy-metal-contaminated soils using higher plants species as hyperaccumulators. [ABSTRACT FROM AUTHOR]

Simple Summary: Plant or nature-based cleanup or removal of pollutants is one of the most promising eco-friendly approaches for sustainable ecosystem management. Consequently, the contamination level, accumulation and remediation ability of three mangrove plants (Excoecaria agallocha, Avicennia officinalis, Sonneratia apetala) and their surrounding sediments were studied. Analyses of accumulated metals by using several indices reveals that the area is low to moderately contaminated, and all the three plants examined can be used as phytoextractors as they have the ability to store metals in their tissues. E. agallocha can be used as a good phytostabiliser for Mn which can reduce the risk of erosion and leaching of this pollutant to water bodies. Furthermore, for metal extraction, A. officinalis was found more suitable than other two plants. Overall, the results indicate that these mangrove plants can be used in the phytoremediation of contaminated soils by metals. Toxic metal pollution is a global issue, and the use of metal-accumulating plants to clean contaminated ecosystems is one of the most rapidly growing ecologically beneficial and cost-effective technologies. In this study, samples of sediment and three mangrove species (Excoecaria agallocha, Avicennia officinalis, Sonneratia apetala) were collected from the world's largest mangrove forest (along the Northern Bay of Bengal Coast) with the aim of evaluating metal concentrations, contamination degrees, and phytoremediation potentiality of those plants. Overall, the heavy metals concentration in sediment ranged from Cu: 72.41–95.89 mg/kg; Zn: 51.28–71.20 mg/kg; Fe: 22,760–27,470 mg/kg; Mn: 80.37–116.37 mg/kg; Sr: 167.92–221.44 mg/kg. In mangrove plants, the mean concentrations were in the order of E. agallocha > A. officinalis > S. apetala. The mean (± SD) concentration of each metal in the plant tissue (root) was found following the descending order of Fe (737.37 ± 153.06) > Mn (151.13 ± 34.26) > Sr (20.98 ± 6.97) > Cu (16.12 ± 4.34) > Zn (11.3 ± 2.39) mg/kg, whereas, in the leaf part, the mean concentration (mg/kg) of each metal found in the order of Fe (598.75 ± 410.65) > Mn (297.27 ± 148.11) > Sr (21.40 ± 8.71) > Cu (14.25 ± 2.51) > Zn (12.56 ± 2.13). The contamination factor (CF) values for the studied metals were in the descending order of Cu > Sr > Zn > Fe > Mn. The values of Igeo (Geo-accumulation index) and CF showed that the area was unpolluted to moderately polluted by Zn, Fe, Mn, Cu and Sr. Enrichment factor (EF) values in both sampling stations portrayed moderate to minimum enrichment. Phytoremediation potentiality of the species was assessed by bio-concentration factor (BCF) and translocation factor (TF). BCF values showed less accumulation for most of the heavy metals (<1) except Mn which was highly accumulated in all mangrove plants. The translocation factor (TF) values depicted that most of the heavy metals were strongly accumulated in plant tissues (>1). However, the BCF value depicts that Mn was highly bioconcentrated in E. agallocha, but the translocation on leaves tissue were minimum, which reveals that E. agallocha is phytoextractor for Mn, and accumulated in root tissues. All the examined plants can be used as phytoextractors as they have bioconcentration factors <1 and translocation factors >1. However, A. officinalis is clearly more suitable for metal extraction than S. apetala and E. agallocha in terms of hyper-metabolizing capabilities. [ABSTRACT FROM AUTHOR]

Simple Summary: Intercropping of different greening plant species is a regular management practice in landscape engineering. However, how this approach works on the remediation of heavy metal soil is not fully known. Here, the effect of intercropping two greening species, Euonymus japonicus and Photinia × fraseri on phytoremediation efficiency was studied in a Cd/Cu/Zn-contaminated field. This study provides (1) a feasible biotechnique for improving phytoremediation efficiency using greening plants and (2) a more practical work for multiple HM-polluted soil than research on single-polluted soil. Intercropping plants for phytoremediation is a promising strategy in heavy metal-polluted soils. In this study, two typical greening plant species, Euonymus japonicus (E. japonicus) and Photinia × fraseri (P. × fraseri), were intercropped in a Cd/Cu/Zn-contaminated field. The phytoremediation efficiency was investigated by measuring the plant biomass, metal concentration, and mycorrhizal colonisation, as well as the effects on soil properties, including soil pH; soil total N; and available N, P, K, Cd, Cu, and Zn. The results showed that, compared with the monoculture system, intercropping significantly lowered the available Cd, Cu, and Zn contents, significantly improved the total and available N contents in rhizosphere soils of both plant species, and increased the hyphae colonisation rate of P. × fraseri. In both plants, intercropping significantly improved the total plant biomass. Furthermore, the concentrations Zn and Cd in the root of E. japonicus and Cu concentration in the root of P. × fraseri were enhanced by 58.16%, 107.74%, and 20.57%, respectively. Intercropping resulted in plants accumulating higher amounts of Cd, Cu, and Zn. This was particularly evident in the total amount of Cd in E. japonicus, which was 2.2 times greater than that in the monoculture system. Therefore, this study provides a feasible technique for improving phytoremediation efficiency using greening plants. [ABSTRACT FROM AUTHOR]

The cultivation of energy crops on degraded soils contributes to reduce the risks associated with land use change, and the biomass may represent an additional revenue as a feedstock for bioenergy. Switchgrass and giant reed were tested under 300 and 600 mg Cr kg−1, 110 and 220 mg Ni kg−1, and 4 and 8 mg Cd kg−1 contaminated soils, in a two year pot experiment. Switchgrass yields (average aerial 330 g.m−2 and below ground 430 g.m−2), after the second year harvest, were not affected by Cd contamination and 110 mg Ni kg−1, but 220 mg Ni kg−1 significantly affected the yields (55–60% reduction). A total plant loss was observed in Cr-contaminated pots. Giant reed aboveground yields (control: 410 g.m−2), in the second year harvest, were significantly affected by all metals and levels of contamination (30–70% reduction), except in 110 mg Ni kg−1 pots. The belowground biomass yields (average 1600 g.m−2) were not affected by the tested metals. Contamination did not affect the high heating value (HHV) of switchgrass (average 18.4 MJ.kg−1) and giant reed aerial fractions (average 18.9 MJ.kg−1, stems, and 18.1 MJ.kg−1, leaves), harvested in the second year, indicating that the biomass can be exploited for bioenergy. [ABSTRACT FROM AUTHOR]

Environmental biotechnologies are a popular choice for using efficient, low-cost, low-waste, and environmentally friendly methods to clean up and restore polluted sites. In these technologies, plants (terrestrial and aquatic) and their associated micro-organisms are used to eliminate pollutants that threaten the health of humans and animals. They have emerged as alternative methods to conventional techniques that have become increasingly aggressive to the environment. Currently, all actors of the environment, whether governors, industrialists, or citizen associations are more interested in the application and development of these technologies. The present overview provides available information about recent developments in phytoremediation processes using specifically aquatic plants. The main goal is to highlight the key role of this technology in combating the drastic organic and inorganic pollution that threatens our planet daily. Furthermore, this study presents the valorization of aquatic plant after phytoremediation process in energy. In particular, this article tries to identify gaps that are necessary to propose future developments and prospects that could guarantee sustainable development aspired by all generations. [ABSTRACT FROM AUTHOR]

Simple Summary: The legume–rhizobium symbiosis is one of the most beneficial interactions with high importance in agriculture, as it delivers nitrogen to plants and soil, thereby enhancing plant growth. Currently, this symbiosis is increasingly being exploited in phytoremediation of metal contaminated soil to improve soil fertility and simultaneously metal extraction or stabilization. Rhizobia increase phytoremediation directly by nitrogen fixation, protection of plants from pathogens, and production of plant growth-promoting factors and phytohormones. With the increasing industrial activity of the growing human population, the accumulation of various contaminants in soil, including heavy metals, has increased rapidly. Heavy metals as non-biodegradable elements persist in the soil environment and may pollute crop plants, further accumulating in the human body causing serious conditions. Hence, phytoremediation of land contamination as an environmental restoration technology is desirable for both human health and broad-sense ecology. Legumes (Fabaceae), which play a special role in nitrogen cycling, are dominant plants in contaminated areas. Therefore, the use of legumes and associated nitrogen-fixing rhizobia to reduce the concentrations or toxic effects of contaminants in the soil is environmentally friendly and becomes a promising strategy for phytoremediation and phytostabilization. Rhizobia, which have such plant growth-promoting (PGP) features as phosphorus solubilization, phytohormone synthesis, siderophore release, production of beneficial compounds for plants, and most of all nitrogen fixation, may promote legume growth while diminishing metal toxicity. The aim of the present review is to provide a comprehensive description of the main effects of metal contaminants in nitrogen-fixing leguminous plants and the benefits of using the legume–rhizobium symbiosis with both wild-type and genetically modified plants and bacteria to enhance an efficient recovery of contaminated lands. [ABSTRACT FROM AUTHOR]

Phytoremediation, as a bioremediation process in which plants are used to remove contaminants from an environment, has proved to be a practical and low-cost strategy for recovering mining-affected areas. This study aims to assess the potential for use in phytoremediation of two willow species, Salix viminalis and Salix dasyclados, by testing their potential for cleaning-up a range of soils with differing heavy metal concentrations: Pb (111, 141, 192 and 249 mg /kg), Zn (778.6, 1482, 2734 and 4411 mg/kg) and Cd (3.00, 5.03, 9.14 and 16.07 mg/kg). The extracted metals were preferentially translocated to the leaves with considerably higher concentrations and relative BAFs in the case of S. viminalis. The highest recorded Zn concentration of over 0.5% was found in the leaves of S. viminalis growing in soil 4. However, under the conditions of the experiments, S. dasyclados showed greater potential for use in phytoremediation, especially if coupled with use of biomass for energy production. An assessment of the suitability of willow species in this role, with regard to wider aspects involved, such as use of resultant biomass and/or waste management, revealed good potential. Willows are fast growing, grow vigorously from coppiced stumps and have extensive root systems. Therefore, their use in bioenergy production through pyrolysis or combustion, coupled with flue gas screening, is strongly advised. [ABSTRACT FROM AUTHOR]

Rapid industrialization, mine tailings runoff, and agricultural activities are often detrimental to soil health and can distribute hazardous metal(loid)s into the soil environment, with harmful effects on human and ecosystem health. Plants and their associated microbes can be deployed to clean up and prevent environmental pollution. This green technology has emerged as one of the most attractive and acceptable practices for using natural processes to break down organic contaminants or accumulate and stabilize metal pollutants by acting as filters or traps. This review explores the interactions between plants, their associated microbiomes, and the environment, and discusses how they shape the assembly of plant-associated microbial communities and modulate metal(loid)s remediation. Here, we also overview microbe–heavy-metal(loid)s interactions and discuss microbial bioremediation and plants with advanced phytoremediation properties approaches that have been successfully used, as well as their associated biological processes. We conclude by providing insights into the underlying remediation strategies' mechanisms, key challenges, and future directions for the remediation of metal(loid)s-polluted agricultural soils with environmentally friendly techniques. [ABSTRACT FROM AUTHOR]

Phytoremediation of heavy metals (HMs) is an efficient methodology to remove toxic metals from the soil. On the other hand, arbuscular mycorrhizal fungi (AMF) are utilized as biological fertilizers as they improve root expansion, nutrient uptake, shoot growth, and plant biological performance. In this study, the effect of AMF inoculation on the morphological traits, macro- and micronutrient contents, essential oil content (EOC), and essential oil yield (EOY) of lavender (Lavandula angustifolia L.) was investigated, under HM (Pb and Ni) stress in greenhouse conditions. The performed treatments were as follows: AMF (Funneliformis mosseae) inoculation (5 g kg−1 soil), and HM stress, including Pb (150 and 225 mg kg−1 soil from Pb(NO3)2) and Ni (220 and 330 mg kg−1 soil from Ni(NO3)2). The controls were the absence of AMF and HM treatments. The results showed that the contamination with Pb and Ni decreased plant height, branch number, fresh and dry weights of shoots and roots, and P, K, Mg, Fe, Zn, and Mn contents. At the same time, AMF inoculation modulated the adverse effects of Pb and Ni treatments. AMF inoculation and lower concentrations of Pb and Ni increased the EOC and EOY of lavender plants, whereas the higher levels of HMs reduced the morphobiometric traits. AMF inoculation increased the Pb and Ni contents in roots. The treatment with Pb at 220 mg kg−1 led to a higher stress effect than that of Ni treatment. In conclusion, the results recommend AMF inoculation as a helpful procedure to improve the growth responses and EOY of lavender in environments polluted with the tested HMs and suggest that AMF inoculation is potentially efficient in mitigating HM stress effects. [ABSTRACT FROM AUTHOR]

Miscanthus lutarioriparius has a growing area of 100,000 ha and an annual biomass production of 1 Mt around Dongting Lake. However, due to serious soil pollution, there is a concern that the M. lutarioriparius biomass could have high heavy metal (HM) concentrations. This necessitates investigation of biomass quality to find the appropriate end use. Thus, this study aims to investigate the dynamics of HM elements in the M. lutarioriparius biomass and their impact on biomass quality across different growing areas and harvest times. We analyzed the HM concentrations in soil and biomass from 11 sites under different harvesting times (April, August and December). Results showed that Cd in soil samples was 9.43-fold higher than the national standards. The heavily polluted soil caused a high HM concentration in the biomass and the accumulation increased with the delayed harvest. The fresh young shoots in April met the food limitation for Cd and Cr, whereas Pb concentration was slightly higher than the threshold limit. The mature biomass from the southern part had higher Mn, Cd and Pb, but lower Cu, Zn and Cr concentrations than that from the eastern part. These results can provide guidance for guaranteeing the consistent quality of the M. lutarioriparius biomass for bio-based industry. [ABSTRACT FROM AUTHOR]

There are many enclaves in the Mediterranean basin with soils contaminated with heavy metal(loid)s, most of these in natural areas of great beauty that have suffered the consequences of industrial and mining activity for years. These soils pose a risk to human and animal health due to the transfer of metal(loid)s condemning these areas to isolation. The rehabilitation by means of phytoremediation is one of the most used techniques, but phytoremediation must be part of a comprehensive strategy of steps that guide owners and administrations in the recovery of ecosystem services. An easily replicable decision-making methodology is defined, considering the initial conditions, the preferences of the decision makers or typologies from among six possibilities and the different models of use, typified in 13 categories. As a result, a landscape is obtained that integrates phytostabilization and areas with recreational and/or educational uses. Two case studies from the southeast of Spain are presented as validation, a deposit of mining sludge residues and the channel of a river contaminated by industrial discharges. Both enclaves are included in the tourist and cultural offer of their area, thus achieving an environmental and socioeconomic benefit and have been visited by more than 1000 people in a two-year period. [ABSTRACT FROM AUTHOR]

Simple Summary: The goal of this study was to measure the concentrations of four potentially toxic metals in green amaranth (leaves, stems, and roots) collected from 11 sampling sites in Peninsular Malaysia. The danger of the metal concentrations to human health was assessed. The metal levels were highest in the root parts, followed by stems and leafy parts. The positive relationships of metals between plant parts and the habitat topsoils suggested that the green amaranth could be used as a useful biomonitoring agent of Cd, Fe, and Ni pollution. In addition, the green amaranth was also a very promising phytoextraction agent of Ni and Zn and a very promising phytostabiliser of Cd and Fe. This indicates that green amaranth can be used in the phytoremediation of the polluted soils by Cd, Fe, Ni, and Zn. The human health risk assessment for the potentially toxic metals (PTMs) in the leaves of green amaranth indicated that the four metals posed no non-carcinogenic dangers to consumers. However, it is of utmost importance to monitor PTMs in Amaranthus fields periodically. Human health risk and phytoremediation of potentially toxic metals (PTMs) in the edible vegetables have been widely discussed recently. This study aimed to determine the concentrations of four PTMs, namely Cd, Fe, Ni, and Zn) in Amaranthus viridis (leaves, stems, and roots) collected from 11 sampling sites in Peninsular Malaysia and to assess their human health risk (HHR). In general, the metal levels followed the order: roots > stems > leaves. The metal concentrations (µg/g) in the leaves of A. viridis ranged from 0.45 to 2.18 dry weight (dw) (0.05–0.26 wet weight (ww)), 74.8 to 535 dw (8.97–64.2 ww), 2.02 to 7.45 dw (0.24–0.89 ww), and 65.2 to 521 dw (7.83–62.6 ww), for Cd, Fe, Ni, and Zn, respectively. The positive relationships between the metals, the plant parts, and the geochemical factions of their habitat topsoils indicated the potential of A. viridis as a good biomonitor of Cd, Fe, and Ni pollution. With most of the values of the bioconcentration factor (BCF) > 1.0 and the transfer factor (TF) > 1.0, A. viridis was a very promising phytoextraction agent of Ni and Zn. Additionally, with most of the values of BCF > 1.0 and TF < 1.0, A. viridis was a very promising phytostabiliser of Cd and Fe. With respect to HHR, the target hazard quotients (THQ) for Cd, Fe, Pb, and Zn in the leaves of A. viridis were all below 1.00, indicating there were no non-carcinogenic risks of the four metals to consumers, including children and adults. Nevertheless, routine monitoring of PTMs in Amaranthus farms is much needed. [ABSTRACT FROM AUTHOR]

In a model experiment, some adaptive characteristics, the bioaccumulation of toxic elements from technogenically-contaminated soils with polyelement anomalies, and rhizosphere microflora of Japanese millet, Echinochloa frumentacea, were studied using biochemical, microbiological, physicochemical (AAS, ICP-MS, INAA), and metagenomic (16S rRNA) methods of analysis. Good adaptive characteristics (the content of photosynthetic pigments, low molecular weight antioxidants) of E. frumentacea grown on the soils of metallurgical enterprises were revealed. The toxic effect of soils with strong polyelement anomalies (multiple excesses of MPC for Cr, Ni, Zn, As, petroleum products) on biometric parameters and adaptive characteristics of Japanese millet were shown. The rhizosphere populations of E. frumentacea grown in the background soil were characterized by the lowest taxonomic diversity compared to the rhizobiomes of plants grown in contaminated urban soils. The minimal number of all groups of microorganisms studied was noted in the soils, which contain the highest concentrations of both inorganic (heavy metals) and organic (oil products) pollutants. The taxonomic structure of the rhizospheric microbiomes of E. frumentacea was characterized. It has been established that E. frumentacea accumulated Mn, Co, As, and Cd from soils with polyelement pollution within the average values. V was accumulated mainly in the root system (transfer factor from roots to shoots 0.01–0.05) and its absorption mechanism is rhizofiltration. The removal of Zn by shoots of E. frumentacea increased on soils where the content of the element exceeded the MPC and was 100–454 mg/kg of dry weight (168–508 g/ha). Analysis of the obtained data makes it possible to recommend E. frumentacea for phytoremediation of soil from Cu and Zn at a low level of soil polyelement contamination using grass mixtures. [ABSTRACT FROM AUTHOR]

Several species from the Brassica genus are very important agricultural crops in different parts of the world and are also known to be heavy metal accumulators. There have been a large number of studies regarding the tolerance, uptake and defense mechanism in several of these species, notably Brassica juncea and B. napus, against the stress induced by heavy metals. Numerous studies have also been published about the capacity of these species to be used for phytoremediation purposes but with mixed results. This review will focus on the latest developments in the study of the uptake capacity, oxidative damage and biochemical and physiological tolerance and defense mechanisms to heavy metal toxicity on six economically important species: B. juncea, B. napus, B. oleracea, B. carinata, B. rapa and B. nigra. [ABSTRACT FROM AUTHOR]

Simple Summary: Despite its high organic matter content, sewage sludge contains significant quantities of heavy metals, including those designated as hazardous, such as cadmium, nickel, chromium, mercury, copper, lead, and zinc, which, as a consequence, have a negative impact on living organisms. The current research sought to study the effect of dumping sludge, as one of the sources of pollution with heavy metals, on biodiversity and to assess the bioremediation and stress defense strategies of a tolerant plant species. The obtained results showed that soil pollution by heavy metals has a substantial influence on plant diversity. The selected species, Amaranthus retroflexus L., showed a high biological concentration factor (BCF) and low translocation factor (TF) for Cu, As and Ni. The stress defense strategies of A. retroflexus grown under complex heavy metals contamination are studied and discussed. Accumulation of heavy metals in soil is becoming an increasingly serious eco-environmental problem. Thus, investigating how plants mitigate heavy metal toxicity is necessary to reduce the associated risks. Here, we aimed to assess the bioremediation and stress defense strategies of tolerant plant species grown under complex heavy metals contamination. To this end, a field study was conducted on the vegetation cover of sites with different soil pollution levels. Forty-two plant species that belong to 38 genera and 21 families were identified. The pollution had a significant impact on plant richness in the polluted sites. Out of several screened plants, Amaranthus retroflexus L. was selected because of its high relative density (16.7) and a high frequency (100%) in the most polluted sites. The selected species showed a high biological concentration factor (BCF) and low translocation factor (TF) for Cu, As and Ni. To control the heavy metal-induced oxidative damage, A. retroflexus invested in detoxification (metallothionein and phytochelatins, glutathione and glutathione-S-transferase (GST). At the organ level, oxidase damage (H2O2, lipid and protein peroxidation) was observed, particularly in the roots. To mitigate heavy metal oxidative stress, antioxidant mechanisms (e.g., tocopherols, glutathione, peroxidases, catalase, peroxide dismutase and ASC-GSH cycle) were upregulated, mainly in the roots. Overall, our results suggested the potentiality of A. retroflexus as a promising bioremediatory and stress-tolerant plant at the same time; moreover, defense and detoxification mechanisms were uncovered. [ABSTRACT FROM AUTHOR]

The consequences of heavy metal contamination are progressively degrading soil quality in this modern period of industry. Due to this reason, improvement of the soil quality is necessary. Remediation is a method of removing pollutants from the root zone of plants in order to minimize stress and increase yield of plants grown in it. The use of plants to remove toxins from the soil, such as heavy metals, trace elements, organic chemicals, and radioactive substances, is referred to as bioremediation. Biochar and fly ash techniques are also studied for effectiveness in improving the quality of contaminated soil. This review compiles amelioration technologies and how they are used in the field. It also explains how nanoparticles are becoming a popular method of desalination, as well as how they can be employed in heavy metal phytoremediation. [ABSTRACT FROM AUTHOR]

The influence of different concentrations of heavy metals (Cu, Mn, Ni, Zn) was analyzed in the Salsola vermiculata germination pattern, seedling development, and accumulation in seedlings. The responses to different metals were dissimilar. Germination was only significantly reduced at Cu and Zn 4000 μM but Zn induced radicle growth at lower concentrations. Without damage, the species acted as a good accumulator and tolerant for Mn, Ni, and Cu. In seedlings, accumulation increased following two patterns: Mn and Ni, induced an arithmetic increase in content in tissue, to the point where the content reached a maximum; with Cu and Ni, the pattern was linear, in which the accumulation in tissue was directly related to the metal concentration in the medium. Compared to other Chenopodiaceae halophyte species, S. vermiculata seems to be more tolerant of metals and is proposed for the phytoremediation of soils contaminated by heavy metals. [ABSTRACT FROM AUTHOR]

In recent decades, serious contamination of soils by heavy metals has been reported. It is therefore a matter of urgency to develop a new and efficient technology for removing contaminants from soil. Another aspect to this problem is that environmental pollution decreases the biological quality of soil, which is why pesticides and fertilizers are being used in ever-larger quantities. The environmentally friendly solutions to these problems are phytoremediation, which is a technology that cleanses the soil of heavy metals, and biofumigation, a process that helps to protect crops using natural plant compounds. So far, these methods have only been used separately; however, research on a technology that combines them both using white cabbage has been carried out. [ABSTRACT FROM AUTHOR]

Phytochelatins (PCs) play an important role in detoxification of heavy metals in plants. PCs are synthesized from glutathione by phytochelatin synthase (PCS), a dipeptidyltransferase. Sesbania rostrata is a tropical legume plant that can tolerate high concentrations of Cd and Zn. In this study, the S. rostrata PCS gene (SrPCS) and cDNAs were isolated and characterized. Southern blot and sequence analysis revealed that a single copy of the SrPCS gene occurs in the S. rostrata genome, and produces four different SrPCS mRNAs and proteins, SrPCS1-SrPCS4, by alternative splicing of the SrPCS pre-mRNA. The SrPCS1 and SrPCS3 proteins conferred Cd tolerance when expressed in yeast cells, whereas the SrPCS2 and SrPCS4 proteins, which lack the catalytic triad and the N-terminal domains, did not. These results suggested that SrPCS1 and SrPCS3 have potential applications in genetic engineering of plants for enhancing heavy metal tolerance and phytoremediation of contaminated soils. [ABSTRACT FROM AUTHOR]

In this study, the influence of lead (II) ions on sunflower growth and biochemistry was investigated from various points of view. Sunflower plants were treated with 0, 10, 50, 100 and/or 500 μM Pb-EDTA for eight days. We observed alterations in growth in all experimental groups compared with non-treated control plants. Further we determined total content of proteins by a Bradford protein assay. By the eighth day of the experiment, total protein contents in all treated plants were much lower compared to control. Particularly noticeable was the loss of approx. 8 μg/mL or 15 μg/mL in shoots or roots of plants treated with 100 mM Pb-EDTA. We also focused our attention on the activity of alanine transaminase (ALT), aspartate transaminase (AST) and urease. Activity of the enzymes increased with increasing length of the treatment and applied concentration of lead (II) ions. This increase corresponds well with a higher metabolic activity of treated plants. Contents of cysteine, reduced glutathione (GSH), oxidized glutathione (GSSG) and phytochelatin 2 (PC2) were determined by high performance liquid chromatography with electrochemical detection. Cysteine content declined in roots of plants with the increasing time of treatment of plants with Pb-EDTA and the concentration of toxic substance. Moreover, we observed ten times higher content of cysteine in roots in comparison with shoots. The observed reduction of cysteine content probably relates with its utilization for biosynthesis of GSH and phytochelatins, because the content of GSH and PC2 was similar in roots and shoots and increased with increased treatment time and concentration of Pb- EDTA. Moreover, we observed oxidative stress caused by Pb-EDTA in roots where the GSSG/GSH ratio was about 0.66. In shoots, the oxidative stress was less distinctive, with a GSSG/GSH ratio 0.14. We also estimated the rate of phytochelatin biosynthesis from the slope of linear equations plotted with data measured in the particular experimental group. The highest rate was detected in roots treated with 100 μM of Pb-EDTA. To determine heavy metal ions many analytical instruments can be used, however, most of them are only able to quantify total content of the metals. This problem can be overcome using laser induced breakdown spectroscopy, because it is able to provide a high spatial-distribution of metal ions in different types of materials, including plant tissues. Data obtained were used to assemble 3D maps of Pb and Mg distribution. Distribution of these elements is concentrated around main vascular bundle of leaf, which means around midrib. [ABSTRACT FROM AUTHOR]

Phytoremediation is an effective and low-cost method for the remediation of soil contaminated by potentially toxic elements (metals and metalloids) with hyperaccumulating plants. This study analyzed hyperaccumulator publications using data from the Web of Science Core Collection (WoSCC) (1992–2020). We explored the research status on this topic by creating a series of scientific maps using VOSviewer, HistCite Pro, and CiteSpace. The results showed that the total number of publications in this field shows an upward trend. Dr. Xiaoe Yang is the most productive researcher on hyperaccumulators and has the broadest international collaboration network. The Chinese Academy of Sciences (China), Zhejiang University (China), and the University of Florida (USA) are the top three most productive institutions in the field. China, the USA, and India are the top three most productive countries. The most widely used journals were the International Journal of Phytoremediation, Environmental Science and Pollution Research, and Chemosphere. Co-occurrence and citation analysis were used to identify the most influential publications in this field. In addition, possible knowledge gaps and perspectives for future studies are also presented. [ABSTRACT FROM AUTHOR]

Simple Summary: Some main drains in the Nile Delta of Egypt are subjected to heavy pollution loads and used to irrigate crops and vegetables. Here, we assessed the pollution level and the ability of some wild aquatic macrophytes (Cyperus alopecuroides, Echinochloa stagnina, Eichhornia crassipes, Ludwigia stolonifera, Phragmites australis, Ranunculus sceleratus, and Typha domingensis) to accumulate eight heavy metals (Fe, Cu, Zn, Mn, Co, Cd, Ni, and Pb) in three of the polluted drains (Amar, El-Westany, and Omar-Beck). The sediment in the three drains exceeded the worldwide permissible ranges of Cu, Zn, and Pb, but it ranged within safe limits for Mn, Cd, Ni, and Co. P. australis accumulated the highest levels of Fe, Co, Cd, and Ni, while E. crassipes contained the highest concentrations of Cu, Zn, Mn and Pb. The bioaccumulation factor was > 1 for the investigated heavy metals (except Cu) in all species, except C. alopecuroides. Accordingly, these species could be applied for the accumulation and phytostabilization of these metals. The current study addressed the heavy metals accumulation potentials of seven perennial aquatic macrophytes (Cyperus alopecuroides, Echinochloa stagnina, Eichhornia crassipes, Ludwigia stolonifera, Phragmites australis, Ranunculus sceleratus and Typha domingensis) and the pollution status of three drains (Amar, El-Westany and Omar-Beck) in the Nile Delta of Egypt. Nine sites at each drain were sampled for sediment and plant analyses. Concentrations of eight metals (Fe, Cu, Zn, Mn, Co, Cd, Ni, and Pb) were determined in the sediment and the aboveground and belowground tissues of the selected macrophytes. Bioaccumulation factor (BF) and translocation factor (TF) were computed for each species. The sediment heavy metals concentrations of the three drains occurred in the following order: El-Westany > Amar > Omar-Beck. The concentrations of sediment heavy metals in the three drains were ordered as follows: Fe (438.45–615.17 mg kg−1) > Mn (341.22–481.09 mg kg−1) > Zn (245.08–383.19 mg kg−1) > Cu (205.41–289.56 mg kg−1) > Pb (31.49–97.73 mg kg−1) > Cd (13.97–55.99 mg kg−1) > Ni (14.36–39.34 mg kg−1) > Co (1.25–3.51 mg kg−1). The sediment exceeded the worldwide permissible ranges of Cu, Zn and Pb, but ranged within safe limits for Mn, Cd, Ni and Co. P. australis accumulated the highest concentrations of Fe, Co, Cd and Ni, while E. crassipes contained the highest concentrations of Cu, Zn, Mn, and Pb. Except for C. alopecuroides and Cu metal, the studied species had BF values greater than one for the investigated heavy metals. Nevertheless, the TFs of all species (except Cd in L. stolonifera) were less than one. Hence, the studied species are appropriate for accumulation, biomonitoring, and phytostabilization of the investigated metals. [ABSTRACT FROM AUTHOR]

Simple Summary: Generally, plants undergo a series of oxidative damage and even die after being stressed by cadmium (Cd). Recently, numerous studies about hyperaccumulators that can tolerate and enrich cadmium in the environment have been reported, revealing its potential in restoration of heavy metal pollution. However, there is a lack of systemic understanding of the mechanisms of Cd accumulation and detoxification by hyperaccumulators. Therefore, the purpose of this review is to investigate how these plants absorb, transport, and distribute Cd. The role of plant roots, compartmentalization, chelation, antioxidants, stress, and osmotic adjustment in bioaccumulation of Cd are comprehensively discussed. This review contributes to further understanding the mechanisms of plant enrichment and detoxification of heavy metals. The heavy metal cadmium (Cd), as one of the major environmentally toxic pollutants, has serious impacts on the growth, development, and physiological functions of plants and animals, leading to deterioration of environmental quality and threats to human health. Research on how plants absorb and transport Cd, as well as its enrichment and detoxification mechanisms, is of great significance to the development of phytoremediation technologies for ecological and environmental management. This article summarises the research progress on the enrichment of heavy metal cadmium in plants in recent years, including the uptake, transport, and accumulation of Cd in plants. The role of plant roots, compartmentalisation, chelation, antioxidation, stress, and osmotic adjustment in the process of plant Cd enrichment are discussed. Finally, problems are proposed to provide a more comprehensive theoretical basis for the further application of phytoremediation technology in the field of heavy metal pollution. [ABSTRACT FROM AUTHOR]

Accumulation of heavy metals (HMs) by ornamental plants (OPs) from contaminated agriculture soils is a unique technique that can efficiently reduce the metal load in the food chain. Amaranthus tricolor L. has attractive characteristics acquiring a higher growth rate and large biomass when grown at heavy metal contaminated soils. Site-specific detailed information is not available on the use of A. tricolor plant in metal phytoremediation from the polluted sites. The study aimed to enhance the uptake of HMs (Pb, Zn, and Cu) via amending poultry litter extract (PLE), vinasse sugarcane (VSC), and humic acid (HA) as natural mobilized organic materials compared to ethylene diamine tetraacetic acid (EDTA), as a common mobilized chemical agent by A. tricolor plant. The studied soils collected from Helwan, El-Gabal El-Asfar (Cairo Governorate), Arab El-Madabeg (Assiut Governorate), Egypt, and study have been conducted under pot condition. Our results revealed all organic materials in all studied soils, except EDTA in EL-Gabal El-Asfar soil, significantly increased the dry weight of the A. tricolor plant compared to the control treatment. The uptake of Pb and Zn significantly (p > 0.05) increased due to applying all organic materials to the studied soils. HA application caused the highest uptake as shown in Pb concentration by more than 5 times in Helwan soil and EDTA by 65% in El-Gabal El-Asfar soil while VSC increased it by 110% in El-Madabeg soil. Also, an increase in Zn concentration due to EDTA application was 58, 42, and 56% for Helwan, El-Gabal El-Asfar, and El-Madabeg soil, respectively. In all studied soils, the application of organic materials increased the remediation factor (RF) than the control. El-Madabeg soil treated with vinasse sugarcane gave the highest RF values; 6.40, 3.26, and 4.02% for Pb, Zn, and Cu, respectively, than the control. Thus, we identified A. tricolor as a successful ornamental candidate that, along with organic mobilization amendments, most efficiently develop soil health, reduce metal toxicity, and recommend remediation of heavy metal-contaminated soils. Additionally, long-term application of organic mobilization amendments and continued growth of A. tricolor under field conditions could be recommended for future directions to confirm the results. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to measure the phyto-tolerance and accumulation of heavy metals in petroleum oily sludge POS by Cajanus cajan (pigeon pea) on soils treated with five different concentrations (1%, 2%, 3%, 4%, and 5% w/w) of the POS. The response of the plant to oily sludge varied significantly from the untreated control and among the various treatments. The growth of C. cajan was slightly (but not significantly) influenced by the oily sludge in soil; growth of C. cajan at relatively lower concentrations of POS (1 to 3%) was greater than in the treatments with relatively higher concentrations POS (4 to 5%). A significant interaction was observed in the relative growth rates (RGRs) of C. cajan, which significantly increased in the treatments with relatively low POS (1 to 3%) and decrease significantly at higher POS concentrations. The heavy metal content of the plant roots as the POS concentrations were increase show that the concentration of all heavy metals in the roots increased accordingly. Cu showed the highest accumulation with an increase from 1.9 to 6.8 mg/kg followed by Pb, Zn, Ni, Mn, and Cr, which was the least-accumulated. Heavy metal analysis in C. cajan tissues indicated a considerable accumulation of the metals Pb, Zn, Ni, Mn, Cu, and Cr in the root and stem of the plant, with negligible metal concentrations detected in the plant leaves, suggesting a low translocation factor but indicating that C. cajan is resistant to heavy metals. As the search for more eco-friendly and sustainable remediating green plant continues, C. cajan shows great potential for reclaiming POS-contaminated soil due to the above properties including resistance to toxic heavy metals from oily sludge. These findings will provide solutions to polluted soils and their subsequent re-vegetation. [ABSTRACT FROM AUTHOR]

Soil pollution with heavy metals has attracted increasing concern, which calls for the development of new remediation strategies. The combination of physical, chemical, and biological techniques can achieve more efficient remediation. However, few studies have focused on whether nanomaterials and beneficial microbes can be jointly used to facilitate phytoremediation. Therefore, we studied the role of nano-zero-valent iron (nZVI) and arbuscular mycorrhizal (AM) fungi in the phytoremediation of an acidic soil polluted with Cd, Pb and Zn, using sweet sorghum. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and mapping analyses were conducted to explore the mechanisms of metal immobilization by nZVI. The results showed that although both bare nZVI (B-nZVI) and starch-stabilized nZVI (S-nZVI) inhibited root mycorrhizal colonization, Acaulospora mellea ZZ successfully colonized the plant roots. AM inoculation significantly reduced the concentrations of DTPA-Cd, -Pb, and -Zn in soil, and the concentrations of Cd, Pb, and Zn in plants, indicating that AM fungi substantially facilitated heavy metal immobilization. Both B-nZVI and S-nZVI, ranging from 50 mg/kg to 1000 mg/kg, did not impede plant growth, and generally enhanced the phytoextraction of heavy metals. XRD, EDS and mapping analyses showed that S-nZVI was more susceptible to oxidation than B-nZVI, and thus had more effective immobilization effects on heavy metals. Low concentrations of nZVI (e.g., 100 mg/kg) and AM inoculation had synergistic effects on heavy metal immobilization, reducing the concentrations of Pb and Cd in roots and enhancing root Zn accumulation. In conclusion, our results showed that AM inoculation was effective in immobilizing heavy metals, whereas nZVI had a low phytotoxicity, and they could jointly contribute to the phytoremediation of heavy metal-contaminated soils with sweet sorghum. [ABSTRACT FROM AUTHOR]

One of the possibilities of removing heavy metals (HMs) from soil is the use of phytoremediation techniques supported with biosolids, which also allow for their disposal. Therefore, the objective of the research was the determination of the sewage sludge suitability after its application to urban soil in order to increase the phytoremediation efficiency of contaminated soil. A field experiment was established on lawns in Białystok (Poland) in two locations with different traffic. The research plots were fertilized with sludge in doses of 14.5 t DM/ha and 29 t DM/ha. A mixture of lawn grasses was sown on the prepared plots. During two years of experiment soil/plant samples were collected, and pH, organic matter, dehydrogenase and catalase activity (soil), the total content of Cd, Cr, Cu, Mo, Ni, Pb, Zn, and Hg (soil/plant), and their fractions (soil) were determined. The HMs in soil were present mainly in residual and reducible fractions. Zn had the highest share in acid-soluble fractions (17–45%). The efficiency of urban soil phytoremediation was determined by the calculation of bioconcentration (BCF) and translocation (TF) factors. The highest values for BCF and TF were obtained for Mo (1.97 and 1.99, respectively). In the presented study, sludge amendment caused an immobilization of heavy metals. [ABSTRACT FROM AUTHOR]

In Chile, 85% of tailings impoundments are inactive or abandoned and many of them do not have a program of treatment or afforestation. The phytoremediation of tailings with Oxalis gigantea, Cistanthe grandiflora, Puya berteroniana and Solidago chilensis have been tested in order to find plants with ornamental value and low water requirements, which enable reductions in molybdenum (Mo), copper (Cu) or lead (Pb) concentrations creating an environmentally friendly surrounding. Ex-situ phytoremediation experiments were carried out for seven months and Mo, Cu and Pb were measured at the beginning and at the end of the growth period. The capacity of these species to phyto-remedy was evaluated using the bioconcentration and translocation factors, along with assessing removal efficiency. Solidago chilensis showed the ability to phytoextract Mo while Puya berteroniana showed potential for Cu and Mo stabilization. The highest removal efficiencies were obtained for Mo, followed by Cu and Pb. The maximum values of removal efficiency for Mo, Cu and Pb were 28.7% with Solidago chilensis, 15.6% with Puya berteroniana and 8.8% with Cistanthe grandiflora, respectively. Therefore, the most noticeable results were obtained with Solidago chilensis for phytoextraction of Mo. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is one of the most toxic metals in the environment, and has noxious effects on plant growth and production. Cd-accumulating plants showed reduced growth and productivity. Therefore, remediation of this non-essential and toxic pollutant is a prerequisite. Plant-based phytoremediation methodology is considered as one a secure, environmentally friendly, and cost-effective approach for toxic metal remediation. Phytoremediating plants transport and accumulate Cd inside their roots, shoots, leaves, and vacuoles. Phytoremediation of Cd-contaminated sites through hyperaccumulator plants proves a ground-breaking and profitable choice to combat the contaminants. Moreover, the efficiency of Cd phytoremediation and Cd bioavailability can be improved by using plant growth-promoting bacteria (PGPB). Emerging modern molecular technologies have augmented our insight into the metabolic processes involved in Cd tolerance in regular cultivated crops and hyperaccumulator plants. Plants' development via genetic engineering tools, like enhanced metal uptake, metal transport, Cd accumulation, and the overall Cd tolerance, unlocks new directions for phytoremediation. In this review, we outline the physiological, biochemical, and molecular mechanisms involved in Cd phytoremediation. Further, a focus on the potential of omics and genetic engineering strategies has been documented for the efficient remediation of a Cd-contaminated environment. [ABSTRACT FROM AUTHOR]

Heavy metals (HMs) are released into the environment by many human activities and persist in water even after remediation. The efficient filtration of solubilized HMs is extremely difficult. Phytoremediation appears a convenient tool to remove HMs from polluted water, but it is limited by the choice of plants able to adapt to filtration of polluted water in terms of space and physiological needs. Biomasses are often preferred. Aquatic moss biomasses, thanks to gametophyte characteristics, can act as live filtering material. The potential for phytoremediation of Hypnales aquatic mosses has been poorly investigated compared to aquatic macrophytes. Their potential is usually indicated as a tool for bioindication and environmental monitoring more than for pollutant removal. When phytoremediation has been considered, insufficient attention has been paid to the adaptability of biomasses to different needs. In this study the heavy metal uptake of moss Taxiphyllum barbieri grown in two different light conditions, was tested with high concentrations of elements such as Pb, Cd, Zn, Cu, As, and Cr. This moss produces dense mats with few culture needs. The experimental design confirmed the capacity of the moss to accumulate HMs accordingly to their physiology and then demonstrated that a significant proportion of HMs was accumulated within a few hours. In addition to the biosorption effect, an evident contribution of the active simplistic mass can be evidenced. These reports of HM accumulation within short time intervals, show how this moss is particularly suitable as an adaptable bio-filter, representing a new opportunity for water eco-sustainable remediation. [ABSTRACT FROM AUTHOR]