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Heavy metals (HMs) contamination has gained much attention due to its high degree of toxicity for living organisms. Therefore, different techniques are underway to eradicate HMs from the environment. Among the biological techniques, phytoremediation is a suitable method, but owing to the slow rate and chance of HMs penetration into the food chain, alternative techniques are needed to reduce their phytotoxicity, and biochar is one of them. Due to the diverse characteristics, biochar immobilizes HMs in the soil by improving soil pH, ion exchange, electrostatic interactions, complexation, precipitation, surface adsorption, and microbial activation. Thereby, amendment of biochar in the HMs-contaminated soils reduces HMs toxicity to plants and limits their penetration into the food chain. In contrast, some biochars have also been studied to induce metal availability in soils and subsequently its uptake by plants. This dual role of biochar depends on the feedstock of biochar, incineration temperature, and the rate of application. Moreover, biochar treatments enhance plant growth under HMs stress by improving nutrient availability, water retention capacity, scavenging of reactive oxygen species, and photosynthetic efficiency. Owing to the beneficial characteristics of biochar in HMs-contaminated sites, the number of publications has tremendously increased. Additionally, the plant species and the types of HMs that have been tested frequently under biochar treatments in these articles have been studied. Overall, the current study would help in understanding the mechanisms of how biochar influences phytoremediation of HMs and improves plant growth in HMs-polluted soils and the current scenario of the available literature. [ABSTRACT FROM AUTHOR]

In the current study, the Cu phytoremediation ability of two ornamental plants, Chrysanthemum indicum L. and Tagetes erecta L., was tracked concerning the growth and physiological responses. Plants were subjected to varying concentrations of Cu (0, 100, 200, and 400 mg/kg) under the pot experiment for 8 weeks. The results showed that the measured growth and physiological characteristics declined in T. erecta shoots and roots at all tested treatments compared with the control. However, in C. indicum at 100 mg/kg, shoot biomass, shoot total soluble protein, and leaves number remained equal to that of the control and then reduced by rising Cu concentrations, compared with the control. Also, results indicated that in C. indicum, after 56 days of exposure to Cu, the chlorophyll pigments content markedly increased and reached a maximum level at 100 mg/kg dose and gradually declined with enhancing Cu concentrations, compared with the control. Other measured growth and physiological parameters decreased in both tissues of C. indicum in response to Cu usage in the growth medium. The carotenoid content of T. erecta decreased in all studied Cu levels in comparison to the control, but in C. indicum remained unaffected up to 200 mg/kg Cu in comparison to the control and then enhanced with increasing Cu level. The augmentation of antioxidant enzyme activity in two species, especially in roots, reflected the incident of Cu stress as demonstrated by elevated MDA and ion leakage levels. Data concerning copper accumulation in tissues, TF, and BAF showed T. erecta is a weak Cu accumulator and seems not to be an appropriate candidate for Cu phytoremediation. However, the Cu content in shoots and roots of C. indicum increased significantly with an increment in applied Cu level. Also, C. indicum accumulated higher Cu concentrations in the roots than in shoots and exhibited TF < 1, 0.1 < BAF root < 1, and can be considered as a Cu excluder by the phytostabilization mechanism. [ABSTRACT FROM AUTHOR]

The present study of phytomitigation potential and adaptive physiological and biochemical responses of helophyte Typha latifolia L. growing in water bodies at different distances from the century-old copper smelter (JSC "Karabashmed" Chelyabinsk Region, Russia) was conducted for the first time. This enterprise is one of the most dominant sources of multi-metal contamination for water and land ecosystems. The aim of the research was to assess the heavy metal (Cu, Ni, Zn, Pb, Cd, Mn, and Fe) accumulation, the photosynthetic pigment complex, and some redox reactions in T. latifolia from six differently technogenic impacted sites. In addition, the quantity of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM) in rhizosphere sediments, as well as some plant growth-promoting (PGP) attributes of 50 isolates from each site, were determined. The water and sediment metal concentrations in highly contaminated sites exceeded the permissible/critical limits and were found much higher than that previously reported by other researchers while studying this helophyte. Both the degree of contamination and geoaccumulation indexes further elucidated extremely high contamination due to prolonged activity of copper smelter. T. latifolia accumulated significantly higher concentrations of the most of studied metals in its roost and rhizome with meager transfer to leaves (the translocation factors were less than one). Spearman's rank correlation coefficient showed a strong positive correlation between the metal concentration in sediments and its content in T. latifolia leaves (rs = 0.786 at p < 0.001 on average) and roots/rhizome (rs = 0.847 at p < 0.001 on average). In highly contaminated sites, the folia content of chlorophyll a and carotenoids decreased (by 30 and 38%, respectively), while lipid peroxidation enhanced (by 42%) on average compared to S1–S3 sites. These responses were accompanied by increasing non-enzymatic antioxidant content (soluble phenolic compounds, free proline, and soluble thiols) that allow plants to resist under significant anthropogenic loads. QMAFAnM in the five studied rhizosphere substrates varied insignificantly (2.5 × 106 − 3.8 × 107 cfu g−1 DW) and was decreased only in the most contaminated site (4.5 × 105). The proportion of rhizobacteria capable of fixing atmospheric nitrogen decreased by 1.7 times, solubilizing phosphates by 1.5 times, and synthesizing indol-3-acetic acid by 1.4 times in highly contaminated sites, while the amount of siderophore, 1-aminocyclopropane-1-carboxylate deaminase, and HCN producing bacteria did not considerably change. The results indicate high resistance of T. latifolia to prolonged technogenic impact, probably due to compensatory adaptive changes in the nonenzymatic antioxidant level and presence of beneficial microorganisms. Thus, T. latifolia was found to be a promising metal-tolerant helophyte that could help in mitigation of metal toxicity due to their phytostabilization even in heavily contaminated environment. [ABSTRACT FROM AUTHOR]

Soil contaminated with heavy metals cause serious threat to the soil quality, biota, and human. The removal or stabilization of heavy metals through plants is an environment friendly approach. The aim of study was to assess the potential of Celosia argentea L. for the phytoremediation of heavy metals contaminated soil. Soil was spiked with different levels (0, 100, 200, 300, and 400 mg/kg) of chromium (Cr), copper (Cu), lead (Pb), and Zn (Zn). Experiment was carried out in greenhouse and impact of heavy metals was evaluated on plant by assessing the germination rate and plant growth. To evaluate either plant has potential to extract/stabilize the heavy metals, concentration in roots and shoot, translocation factor (TF), bioconcentration factor (BCF), and bioaccumulation factor (BAF) were determined. Application of heavy metals significantly affected the germination rate and minimum (26.6%) was observed in Cr spiked soil (400 mg/kg). Moreover, the biomass of C. argentea was also affected by the application of heavy metals. However, the concentration of heavy metals in roots and shoots were low. The BCF and BAF of C. argentea was lower than 1 except at lower levels of Pb and Zn, but the TF was greater than 1. The TF showed that plants have capability to transfer heavy metals to shoots once they are taken up by roots. However, based on the BCF and concentrations of heavy metals in shoots, it is evident that plant could play important role in the phytostabilization of heavy metals polluted soil. [ABSTRACT FROM AUTHOR]

Potentially toxic elements (PTE) in soil like copper (Cu) have been common in agricultural and mining areas worldwide. The sustainable remediation of these areas has been shown to have high socio-environmental relevance and phytoremediation is one of the green technologies to be considered. The challenge is to identify species that are tolerant to PTE, and to assess their phytoremediation potential. The objective of this study was to evaluate the physiological response of Leucaena leucocephala (Lam.) de Wit and to determine the species tolerance and phytoremediation potential to concentrations of Cu in the soil (100, 200, 300, 400 and 500 mg/dm3). The photosynthetic rate was not affected, while the content of chlorophylls decreased as Cu concentrations increased. There was an increased in stomatal conductance and water use efficiency from the treatment of 300. The root biomass and the length were bigger than the shoots, in the treatments above 300. Cu accumulation was greater in the roots than in the shoot of the plants, thus, the Cu translocation index to the shoot was lower. The ability to absorb and accumulate, mainly, Cu in the roots, allowed the development and growth of plants, since the parameters of photosynthesis and biomass accumulation were not affected by the Cu excess. This accumulation in the roots is characterized as a strategy for the phytostabilization of Cu. Therefore, L. leucocephala is tolerant to the Cu concentrations evaluated and has a potential phytoremediation of Cu in the soil. [ABSTRACT FROM AUTHOR]

Organic fertilization and mycorrhization can increase the phytoremediation of copper-contaminated soils. The time of vermicomposting alters the properties of vermicompost, which can affect copper's availability and uptake. Therefore, this study sought to evaluate the effect of different organic fertilizers and mycorrhization on copper-contaminated soil phytoremediation. The soil was contaminated with 100 mg Cu kg−1 dry soil and received mineral fertilizer (MIN), bovine manure (CM), and vermicompost produced in 45 days (V45) or 120 days (V120), all in doses equivalent to 40 mg kg−1 dry soil of phosphorus. Half of the jack bean (Canavalia ensiformis) plants were inoculated with the arbuscular mycorrhizal fungus Rhizophagus clarus. At plant flowering, the dry mass and concentrations of Cu, Zn, Mn, Ca, Mg, P, and K in the soil, solution, and plant tissue were determined, in addition to mycorrhizal colonization, nodulation, photosynthetic pigments, and oxidative stress enzyme activity. Organic fertilization increased plant growth and copper accumulation in aerial tissues. These effects were more evident with the V120, making it suitable for use in copper phytoextraction. Mycorrhization increased root and nodule dry mass, making it recommended for phytostabilization. C. ensiformis nodulation in Cu-contaminated soils depends on vermicompost fertilization and mycorrhization. Hence, the copper phytoremediation by C. ensiformis is increased by using organic fertilization and mycorrhization. [ABSTRACT FROM AUTHOR]

Phytoremediation is a cost-effective nature-based solution for brownfield reclamation. The choice of phytoextraction or phytostabilization strategies is highly relevant when planning full-scale treatments. A suitable approach to identify such species involves the evaluation of plants that grow spontaneously on the contaminated sites. Here, we sought to determine the phytoremediation potential of three spontaneous plant species, namely the trees Acer pseudoplatanus L (A. pseudoplatanus) and Betula celtiberica Rothm. & Vasc (B. celtiberica), and the shrub Buddleja davidii Franch (B. davidii), for the recovery of an urban brownfield. To determine the response of the species to the degree of contamination, we conducted soil and vegetation sampling inside and outside the site. The concentrations of As, Cu, and Zn in soil and plant samples were measured, and then various indexes related to phytoremediation were calculated. The translocation factor and transfer coefficient indicated that vegetation outside the brownfield had phytoextraction capacity while the same plants inside the brownfield revealed phytostabilization properties. Given our results, we propose that the selected species are suitable for phytostabilization strategies in areas with high concentrations of contaminants, whereas they could be used for phytoextraction only in soils with low or moderate levels of pollution. [ABSTRACT FROM AUTHOR]

Camelthorn (Alhagi maurorum Medik) is a desert plant that can withstand a variety of abiotic challenges, including water stress and harsh weather, making it potentially useful for cleaning cadmium (Cd) from contaminated soils. The current study aims to determine the degree of plant tolerance to Cd toxicity and the possibility of using it in the phytoremediation of Cd-contaminated soils. Camelthorn plants were cultivated in soil polluted with Cd at doses of 0, 25, 50, 100, and 200 mg kg−1. The growth, nutrient uptake, Cd concentrations, and some biochemical compounds were determined to study the response of camelthorn plants to Cd stress. Exposure of camelthorn plants to 200 mg kg−1 of Cd inhabited the synthesis of leaf-chlorophyll by 49% compared to the control and reduced the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), and zinc (Zn) by 43, 36, 43, 50, 67, and 36%, respectively. Camelthorn plants can tolerate up to 11 mg kg−1 of available soil Cd, 65 mg kg−1 in the root, and 22 mg kg−1 in the shoot before experiencing Cd toxicity. Camelthorn plants increased the levels of carbohydrates, total phenols, and proline compounds that were used in the scavenging of reactive oxygen species (ROS). Moreover, the plants increased the activity of antioxidant enzymes, i.e., superoxide dismutase (SOD) and peroxidase (POD), to mitigate the oxidative stress caused by Cd toxicity. The root–shoot transfer (TF) of Cd varied between 0.27 to 0.48, while the bioaccumulation factor (BAF) varied between 1.2 and 2.32. Camelthorn plants have a BAF value higher than 1 and a TF value lower than 1. Camelthorn plants accumulate Cd in the roots with low root–shoot transfer and are suitable for phytostabilization technology. Camelthorn plants have a potent antioxidant defense against the toxicity of Cd, and this finding is a good tool in the remediation of Cd-contaminated soil. [ABSTRACT FROM AUTHOR]

The intensive application of agro-chemicals, and in particular of copper (Cu)-based compounds, causes increasing pollution of agricultural land, with serious risks for human health. Aromatic plants used for purposes other than food, can be considered for the exploitation and/or remediation of metal-polluted substrates, since contamination of the essential oils by these metals was not significant. Myrtle (Myrtus communis L.) is a Mediterranean evergreen shrub whose essential oil has many commercial applications. In this work, the effect of an excess of Cu in respect to control conditions was assessed on M. communis growth and foliar terpene composition. Metal accumulation in roots and shoots was also evaluated for the possible use of this species in phytoremediation. The amount of Cu applied in our experiments minimally affected the terpene profiles of in vitro grown plants, whereas no variations were detected in in vivo plants. The presence of the metal in the soil did not significantly impair plant growth, thus allowing its cultivation on polluted substrates. On the other hand, the amount of Cu in the plant was not enough to result in a significant reduction of Cu levels in the soil. Therefore, myrtle plants proved to be good candidates for the re-vegetation of Cu-contaminated lands. [ABSTRACT FROM AUTHOR]

The effectiveness of phytoremediation is closely related to the various interactions between pollutants, soil particles, rhizosphere microorganisms, and plants. Therefore, the object of current study was a cadmium-tolerant bacterium isolated from the rye rhizosphere, with a high degree of genetic similarity to the genus Chryseobacterium. Chryseobacterium sp. DEMBc1 was able to grow with 36 different BiologGN2 carbon sources and show the adaptation to stress factors such as Cd (100 μg ml−1), low temperature (8 °C), and salinity (2% NaCl). Furthermore, it was shown that DEMBc1 had the characteristics of plant growth–promoting microorganisms: it was able to produce ammonia, indole acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase, and siderophores, as well as solubilize Ca3(PO4)3. After inoculation with DEMBc1, a significant decrease in the concentration of Cd was observed in the roots of Festuca ovina grown in Cd-polluted soil, compared to the non-inoculated Cd-polluted soil. It was also noticed that DEMBc1 produced a large amount of extracellular polymeric substances that were significantly higher than the cellular biomass. These polymers can form a barrier to reduce the translocation of Cd from the growth medium to the plant roots. According to the current study, DEMBc1 has a stabilizing potential and can decrease the mobility of Cd in the F. ovina rhizosphere, bioaccumulate metals in plant tissues, and effectively improve the bioavailability of nutrients, especially Fe, N, and P in a polluted environments. [ABSTRACT FROM AUTHOR]

Pennisetum grasses (P. purpureum Schumach. 'Purple', P. alopecuroides (L.) Spreng. 'Liren' and P. alopecuroides (L.) Spreng. 'Changsui'), and a cadmium (Cd) hyperaccumulator (Thlaspi caerulescens J.Presl & C.Presl), were grown in soil with four Cd addition levels of 0, 2, 20 and 200 mg/kg. Toxicity symptoms were not observed although growth of all plants decreased as Cd addition increased. Shoot bioconcentration factor (BCFS), the translocation factor (TF) and shoot accumulation of Cd for most plants first increased and then declined as Cd concentrations increased. In contrast, the root bioconcentration factor (BCFR) for T. caerulescens declined and root Cd accumulation for T. caerulescens and two P. alopecuroides cultivars increased consistently as Cd levels increased. P. purpureum had the largest biomass with shoot Cd accumulation similar to that of T. caerulescens, despite lower foliar Cd concentration. Although shoot Cd concentrations of two P. alopecuroides cultivars were lower than for P. purpureum, root Cd concentrations were greater. P. purpureum had Cd BCFS and TF (> 1) at 2- and 20-mg/kg Cd addition treatments, similar to T. caerulescens. P. alopecuroides cultivars had Cd BCFR (> 1) and TF (< 1) at all Cd levels. Roots did not affect rhizosphere pH. However, concentrations of acid extractable Cd in rhizosphere soil were lower than those of corresponding non-rhizosphere soil at all Cd levels for T. caerulescens and P. purpureum; T. caerulescens and P. purpureum did not affect less bioavailable Cd fractions. Concentrations of acid extractable Cd in the rhizosphere of the P. alopecuroides cultivars were not reduced at any Cd level. Differences in Cd accumulation among the three Pennisetum grasses were mainly attributable to root biomass and Cd TFs rather than rhizosphere Cd mobility. [ABSTRACT FROM AUTHOR]

Black shales are easily exposed due to human activities such as mining, road construction, and shale gas development, which results in several environmental issues including heavy metal (HM) pollution, soil erosion, and the destruction of vegetation. Mosses are widely used to monitor metal pollution in the atmosphere, but few studies on the distribution and dispersion of HMs in the rock–soil–moss system are available. Here, mosses (Pohlia flexuosa Harv. in Hook), growing soils, and corresponding parent rocks were collected from black shale areas. After appropriate pretreatment, samples were analyzed for multiple elemental concentrations by ICP-AES and ICP-MS. The results show that black shale parent rocks have elevated HM concentration and act as a source of multiple metals. The overlying soil significantly inherits and accumulates heavy metals released from black shale. Significant positive correlations between HMs in P. flexuosa and the growing soils indicate that HMs are mainly originating from geological source rather than atmospheric deposition. Differential accumulation of HMs is observed between rhizoids and stems in our study. Moreover, P. flexuosa is able to cope with high concentrations of toxic metals without any visible negative effect on its growth and development. Finally, the bioconcentration factor (BCF) for all the HMs in P. flexuosa is less than 1, indicating that it has a tolerance and exclusion mechanism for these metals, especially for the non-essential elements As and Pb. Therefore, the luxuriant and spontaneous growth of P. flexuosa could be used as a phytostabilization pioneer plant in the black shale outcrop where vascular plants are rare. [ABSTRACT FROM AUTHOR]

The mitigation of metals contamination is currently a crucial issue for the reclamation of mine sites. Indeed, mine wastes are often disposed in open dumps and consequently pollutants are subjected to dispersion in the surrounding areas. In this study, the potential use of Helichrysum microphyllum subsp. tyrrhenicum for phytostabilization was evaluated in ex situ conditions. Ninety specimens were randomly selected and were planted in three substrates (reference substrate, mine waste materials, and mine wastes with compost). Mineralogical compositions of substrates, rhizosphere, and roots were assessed through X-ray diffraction (XRD). Zn, Pb, and Cd concentrations of substrates, rhizosphere, soil pore waters, and plant tissues were determined. The phytostabilization potential was determined through the application of biological accumulation coefficient (BAC), biological concentration factor (BCF), and translocation factor (TF). Moreover, survival and biometric parameters were assessed on plant specimens. The polluted substrates and related rhizosphere materials were mainly composed of dolomite, quartz, pyrite, and phyllosilicate. Zn was the most abundant metal in substrates, rhizosphere, and soil pore waters. XRD analysis on roots showed the presence of amorphous cellulose and quartz and Zn was the most abundant metal in plant tissues. H. microphyllum subsp. tyrrhenicum restricts the accumulation of the metals into roots limiting their translocation in aereal parts, indicating its potential use as phytostabilizer (BCF, BAC, TF < 1). Survival and growth data showed a great adaptability to different substrates, with an evident positive effect of the implementation of compost which increased the plant survival and decreased the metals uptake into roots. [ABSTRACT FROM AUTHOR]

The tolerance of Mentha crispa L. (garden mint) cultivated in cadmium-contaminated oxisol for 120 days was analyzed using plant growth variables such as height, the number of leaves and shoots in different Cd exposure periods, as well as assessing the metal concentration absorbed and accumulated in the plant parts (root, stem, and leaves). The maximum adsorption capacity was estimated at 9220 mg kg−1 and used as a reference to establish the different Cd concentrations to be applied in the soil. M. crispa showed tolerance and revealed a reduction of height, the number of leaves and shoots, root development, and secondary toxicity signs such as chlorosis and leaf wilting. Comparing to the stems and leaves, Cd was retained mainly in the roots. PERMANOVA showed that plant growth variables and Cd concentrations in the plant's part were affected by the Cd exposure time. The canonical discriminant analysis demonstrated height as the most affected variable until 45 growing days, and different responses were observed after 75 days. However, the number of shoots was the variable most affected by higher Cd concentrations. The bioaccumulation and translocation factors for all treatments were lower than one, indicating that M. crispa can be considered as an excluder plant and applied for a phytostabilization strategy. [ABSTRACT FROM AUTHOR]

Vicia villosa Roth is a legume species with a growing application in Argentina as a cover crop (CC), a practice that favors the sustainable development of agricultural systems. However, several areas where the use of this CC provides numerous advantages are affected by high concentrations of arsenic (As). Thus, in the present work we studied hairy vetch ability to cope with arsenate [As(V)], arsenite [As(III)], and the mixture of both along with oxidative stress indexes [chlorophyll content, malondialdehyde (MDA) equivalents] as well as anatomical and histological changes in the root structure. The results obtained suggested a different behavior of hairy vetch depending on its growth stage and on metal(oid) concentration. The roots treated with the contaminant showed less turgidity, thickening of the epidermal and subepidermal parenchymal outer layers, and the presence of dark deposits. The morpho-anatomic parameters (cortex length, vascular cylinder diameter, total diameter, and vascular cylinder area) were altered in plants treated with As(V) and As(V)/As(III) whereas the roots of plants treated with As(III) did not show significant differences respect to the control. Moreover V. villosa could tolerate and remove As from soil, thus the use of this legume species seems an attractive approach to remediate As while protecting contaminated soils. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to determine the cotton plant's tolerance to Pb and its remediation potential. In the first experiment, the phytoremediation potential was determined by exposing the plant to four levels of Pb (0, 500, 750, and 1000 mg kg−1). The cotton plant exhibited an excellent tolerance index at Pb 1000 mg kg−1 (root 78.65% and shoot 93.08%) and lower grade of growth inhibition (root 21.35% and shoot 6.92%). Pb stress resulted in higher leakage of electrolytes and increased the synthesis of higher proline, total phenol, and free amino acid contents to mitigate stress. The plant could not meet the criteria of a hyperaccumulator of Pb. The concentration of Pb in the shoot was a mere 96 μg g−1 dry wt (< the critical judging concentration of 1000 μg g−1 dry wt), and bioconcentration and translocation factors were <1. The study established that cotton exhibited an exclusion mechanism of Pb. Further, the translocation efficiency (TE %) was very low, i.e., <50% (ranged from 49% at 500 mg kg−1 to 42% at 1000 mg kg −1), and the % of Pb removed by the crop was too little (on an average 0.1%). Pb inhibited the dehydrogenase activity (DHA) by 76%, fluorescein diacetate (FDA) hydrolysis by 60%, and β-glucosidase activity by 20%. However, applied Pb increased the population of actinomycetes by 3.21 times, but significantly decreased heterotrophic bacteria by 3.40 times and N2 fixers by over 53% over control. In the second experiment, the plant was exposed to very high Pb (0, 1000, 1500, 2000, 2500, and 3000 mg kg −1) to determine the concentration up to which the plant will survive. The investigation revealed that plants could survive up to Pb 3000 mg kg−1. It confirmed the first experiment in the tolerance index, grade of growth inhibition, bioconcentration factor, translocation factor, and partitioning of Pb. Therefore, it was concluded that the cotton plant was an excluder of Pb and could be effectively cultivated for the phytostabilization of soils polluted with Pb. [ABSTRACT FROM AUTHOR]

Many macrophytes have heavy metal phytoremediation potential from contaminated watercourses. Therefore, the present study investigated the seasonal potential of the sedge plant Cyperus alopecuroides to remediate heavy metals from contaminated water bodies. Water, sediment, and plant samples were collected from four contaminated watercourses and the uncontaminated Nile River. Summer was the blooming season of C. alopecuroides with the highest shoot density, leaf size, fresh production, and dry biomass, while winter represented the lowest growth season. The photosynthetic pigments were distinctly decreased in plants growing in contaminated compared to the uncontaminated sites. Plant roots accumulated concentrations of all measured heavy metals, except Ni, Cu, Zn, and Pb, more significant than the shoot. The maximum concentrations of Al, Ni, and Pb were recorded during spring, while the highest Cd, Cr, Fe, and Mn were recorded during summer. The bioconcentration factor (BCF) of all investigated metals (except Al) was > 1, while the translocation factor (TF) of all elements (except Pb) was ˂ 1. These results indicated the capability of C. alopecuroides for metal phytostabilization and considered the target species a powerful phytoremediator for monitoring water pollution in contaminated wetlands. In this context, the above- and belowground parts of C. alopecuroides should be harvested in summer for efficient phytoremediation. [ABSTRACT FROM AUTHOR]

Past mining activities have left a legacy of abandoned mine tailing deposits whose metal contaminants poses serious risks to ecosystems and human health. While the development of a vegetated cover in mine tailings can help in mitigating these risks, the local factors limiting plant establishment in these sites are not well understood, restricting phytostabilization efforts. Here, we explore some of the barriers that limit seedling establishment of two species (Vachellia farnesiana and Prosopis velutina) in a mine tailing deposit located in Nacozari, Sonora, Mexico, and assess whether compost addition can help in overcoming these barriers in pot and field experiments. Our field observations found 20 times more carbon and at least 4 times more nitrogen concentration in areas under vegetated patches than in non-vegetated areas, while a previous study found no difference in metal concentrations and other physicochemical parameters. This suggests that organic matter and nutrients are a major limitation for plant establishment. In agreement with this, species failed to establish without compost addition in the field experiment. Compost addition also had a positive effect on biomass accumulation, pH and microbial activity, but increased the substrate soluble concentration of As, Cu, and Zn. Nonetheless, only Cu, K, and Mo in P. velutina accumulated in tissues at levels considered toxic for animal consumption. Our study documents that compost addition facilitated plant establishment for the phytostabilization of mine tailings and help to prevent the dispersion of most metal contaminants via animal consumption. We encourage the use of complementary strategies to minimize the risk of dispersion of metal contaminants. [ABSTRACT FROM AUTHOR]

Willow species (Salix L.) are a useful tool for assessing phytostabilization of the sites polluted by heavy metals. Phytostabilization potential of two willow genotypes (Salix alba L. clone '68/53/1' and Salix nigra Marshall clone '0408') has been evaluated in a 45-day hydroponic experiment, using stem cuttings (diameter 12 to 14 mm, length 20 cm) exposed to two concentrations (10−4 M and 10−5 M) of individually applied Cd, Ni, and Pb. Metals were diluted in 25% Hoagland's solution, in forms of CdCl2·H2O, NiSO4·6H2O, and Pb-EDTA. The control group of cuttings was grown in 25% Hoagland's solution without heavy metals. High Cd concentrations in willow roots, 8637 mg/kg (clone '68/53/1') and 6728 mg/kg of dry weight (clone '0408'), have indicated a high phytostabilization potential. However, detailed analyses of cross-sectional area of the root cortex and the central cylinder revealed that the excess concentration of Cd led to a significant reduction of measured anatomical rootʼs traits of clone '68/53/1' in comparison with the control samples. Excessive concentration of Ni and Pb in nutrient solution increased the values of quantitatively measured rootʼs traits of clone '0408', implying stimulatory effects of the applied concentrations. Concentration of 10−4 M of each metal had more negative effects on the rootsʼ anatomical traits, notably on parenchymal and exodermal cells and vessels. Deposits of metals were observed in root tissues. Clone '0408' demonstrated an increased tolerance to heavy metals, which could potentially make this clone useful in phytostabilization. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi are important to the establishment of native vegetation for mined land rehabilitation, particularly in semi-arid and infertile landscapes. However, the information has been scarce about the colonization of AM fungal community in alkaline magnetite Fe ore tailing sites (without toxic metal (loid) contamination). The present study has characterized the diversity of AM fungi across typical domains of a magnetite Fe ore mine located in 200 km south-east of Geraldton, Western Australia, by adopting high throughput Illumina Miseq sequencing. The investigated domains included two tailing sites without top soil covering (T1 and T2), a rehabilitated area of tailings with top soil covering (R1), a revegetated waste rock area (R2), and two native undisturbed soil sites (S1 and S2). The results indicated that the T1/T2 sites had different AM fungal community structure, compared with R1/R2 and S1/S2 sites. The dominant families were Glomeraceae, Claroideoglomeraceae, Archaeosporaceae, Ambisporaceae, and Paraglomeraceae, with Paraglomeraceae (more than 50%) as the most abundant in the T1/T2 and R1/R2 sites. At genus level, Ambispora spp. and Archaeospora spp. were rich in T1/T2 sites (> 10%), while Glomus spp. were preferably dominant in S1/S2 sites (> 10%). Furthermore, amorphous Fe and available P were found to explain the variations associated with AM fungal community composition, particularly the abundance of Archaeosporaceae and Glomeraceae. The study revealed the AM fungal community composition shift across the gradient of Fe ore mine sites, as well as the effects of revegetation on AM fungal community development. The findings indicate the possible restoration of AM fungal community in the tailings undergoing revegetation, and potential adoption of indigenous AM fungi to rapid phytostabilization of the Fe ore tailings under semi-arid climatic conditions. [ABSTRACT FROM AUTHOR]

Many areas throughout the world, mainly arid and semi-arid regions, are simultaneously affected by salinity stress and heavy metal (HM) pollution. Phytoremediation of such environments needs suitable plants surviving under those combined stresses. In the present study, native species naturally growing under an extreme condition, around Qaleh-Zari copper mine located in the eastern part of Iran, with HM-contaminated saline–sodic soil, were identified to find suitable plant species for phytoremediation. For this purpose, the accumulation of HMs (Cu, Zn, Cd, and Pb) in the root and shoot (stem and leaf) of the plants and their surrounding soils was determined to find their main phytoremediation strategies: phytoextraction or phytostabilization. Seven native species surviving in such extreme condition were found, including Launaea arborescens (Batt.) Murb, Artemisia santolina Schrenk, Pulicaria gnaphalodes (Vent.) Boiss, Zygophyllum eurypterum Boiss. & Buhse, Peganum harmala L., Pteropyrum olivieri Jaub. & Spach, and Aerva javanica (Burm. f.) Juss. ex Schult. Evaluation of phytoremediation potential of the identified species based on the calculated HM bioconcentration in roots, HM translocation from roots to shoots, and HM accumulation in the shoots revealed that all of the species were metal phytostabilizers rather than hyperaccumulators. Therefore, these native species can be used for phytostabilization in the HM-contaminated saline soils to prevent HMs entering the uncontaminated areas and groundwater. Compared with the biennial low-biomass hyperaccumulators, some native species such as Z. eurypterum and A. javanica may have more economic value for phytoremediation because of a significant accumulation of HMs in their relatively higher biomass. [ABSTRACT FROM AUTHOR]

A complete orthogonal experiment using a pot test is conducted to investigate the effects of four amendments (biochar, peat, manure, and non-contaminated soil (NCS)) on the metal availability, mobility, and phytostabilization potential of an energy crop, king grass (Pennisetum purpureum × P. thyphoideum), in Pb/Zn mine tailings. The addition of amendments significantly increased the pH and fertility of the tailings, while significantly decreasing the heavy metal available contents in the tailings. The available Cd, Pb, Zn, and As concentrations in the tailings in the treatment amended with biochar+NCS+peat+manure were 51.00%, 36.62%, 50.57%, and 75.88%, respectively, lower than those in the treatment control. The king grass survived in the tailings without amendments, while amendments made the plant grow well or better in the tailings than in NCS. The addition of amendments significantly reduced the content of heavy metals and bioaccumulation factor (BCF) in the plant root but increased the translocation factor (TF) of Cd, Zn, and As and had little effect on the TF of Pb. The TF for heavy metals in plant were lower than one for all of the treatments. During a leaching period of 30 days, the pH of the leachate declined slowly and then maintained at 6.0~6.6. The addition of the amendments significantly reduced the metal concentrations of the leachates, and the highest declines were 50.46%, 20.04%, 41.58%, and 47.04% for Cd, Pb, Zn, and As, respectively. Biochar had a higher immobilization capacity for Cd, Pb, Zn, and As than manure, peat, and NCS. King grass could be used to aid phytostabilization for Cd- and Pb-polluted tailings, and biochar-rich amendments were effective for the in situ immobilization of metals. Further field monitoring is necessary to demonstrate the effectiveness of king grass and amendments under the climatic conditions of China. [ABSTRACT FROM AUTHOR]

A 2-year field experiment was carried out with aim to assess the phytoremediation potential of Miscanthus × giganteus cultivated on the flotation tailings and to evaluate the effects of mineral NPK fertilizer on metal accumulation and plant physiological parameters and growth. Flotation tailings of the mine Rudnik (Serbia) are burdened with Pb, Cu and Zn and cause heavy metal pollution and deterioration of the surrounding ecosystems. In the second year of growth, plants retained the major portion of metals within their roots, with bioconcentration factor > 1 for Cu and Zn and < 1 for Pb. Their translocation factors were far below 1, showing that M. × giganteus acts as excluder of Cu, Zn and especially Pb. Higher amounts of Pb and Zn in leaves reduced the photosynthetic rate and total antioxidative capacity, but increased lipid peroxidation level. Changes at physiological level resulted in pronounced leaf senescence, reduced plant growth rate and annual biomass yield. Fertilization enhanced metal uptake by plant roots, but had no effect on their translocation to leaves. It improved chlorophyll a content, potential efficiency of Photosystem II photochemistry and biomass yield. Overall results indicate that M. × giganteus can be cultivated on the abandoned flotation tailings and that fertilization had positive effects on its physiology and growth. [ABSTRACT FROM AUTHOR]

Better understanding of microbial activity in the rhizosphere soils associated with lead (Pb) uptake by plants may help with the phytoremediation of Pb-contaminated soils. In this work, the effects of Pb exposure (0, 200, 400, 600, 800 mg kg−1) on Pb accumulation and soil microbial activity in the rhizosphere of the mining ecotype (ME) and corresponding non-mining ecotype (NME) of Athyrium wardii (Hook.) Makino were investigated through a pot experiment. Although the plant growth of the two ecotypes was inhibited under Pb stress, the ME showed a less biomass decrease (12.6–44.0%) for aboveground than the NME, showing a greater tolerance to Pb stress. Pb concentrations as well as Pb accumulation in the two ecotypes showed an increasing trend with increasing soil Pb concentrations. The ME presented greater Pb accumulation ability than the NME, especially in underground parts. Pb availability in the rhizosphere soils of the two ecotypes after harvest decreased compared with those before transplantation. Available Pb in the rhizosphere of the ME was 1.4–4.8 times higher than that of the NME under exposure to 200–800 mg kg−1 Pb. The ME shows a greater ability to mobilize Pb in the rhizosphere soils. Pb exposure resulted in an inhibition of microbial activity in the rhizosphere of the two ecotypes. The ME demonstrated greater soil respiration and microbial biomass carbon (MBC) in the rhizosphere than the NME when treated with 200–800 mg kg−1 Pb. The ME showed a less decrease for MBC and a less increase for metabolic quotient in the rhizosphere soils than the NME when exposed to Pb generally. Microorganisms in the rhizosphere soils of the ME seem to be much more adapted to Pb stress, thus showing a great benefit for Pb accumulation and the phytostabilization of Pb-contaminated soils by the ME. [ABSTRACT FROM AUTHOR]

Few plant species used for revegetation grow well in multi-metal-contaminated soils. Vetiver grass (Vetiveria zizanioides) is known to be tolerant of heavy metals. Vetiver has been reported to be effective for revegetation and heavy metal phytoextraction by applying targeted amendments due to its large biomass. In this study, a greenhouse vetiver pot experiment and soil incubation were performed to investigate the growth and Cd, Cr, Cu, Pb, and Zn uptake of vetiver grown in multi-metal-contaminated soils treated with a CaO-activated Si-based slag amendment (0, 0.5, 1.0, and 2.0% w/w). The results showed that the effects of slag amendment on plant growth and heavy metal uptake and distribution were dependent on the amendment dosages and metal species. Although vetiver could grow in contaminated soils, its growth was obviously inhibited. The slag amendment enhanced the vetiver growth and the highest biomass (2.62-fold over the control) was determined at a 1.0% amendment rate. The slag amendment improved plant growth by alleviating the toxicity of heavy metals in plants. This result was mainly attributed to the increases in soil pH and citric acid-extractable Si caused by alkaline amendment. The results suggest that vetiver can be applied to remediate multi-metal-contaminated soils in conjunction with the application of CaO-activated Si-based slag amendment. [ABSTRACT FROM AUTHOR]

Heavy-metal contamination of soils has increased in the last decades due to anthropogenic and industrial activities. Arsenic is one of the pollutants that is commonly found in industrial soils and is toxic for both plants and humans. The pH of the soil or the culture medium is one of the most important factors that interferes with the bioavailability of this metalloid to the plant. The addition of chelating agents, such as citric acid (CA), can increase the absorption of As by plants. Therefore, the objective of this work is to study the effect of the pH and the exogenous addition of citric acid on the growth, As accumulation, and thiol compounds in Eupatorium cannabinum; this plant grows naturally in contaminated soils in Asturias, Spain, and has a potential use in phytoremediation. The results showed that E. cannabinum was able to tolerate As stress even at extreme pH values and accumulated a high amounts of As in its roots, which makes it a promising species for the phytostabilization of soils polluted with this metalloid. An addition of 20 mg CA L−1 led to increased biomass and As accumulation at acidic pH. In order to determine if thiolic compounds, such as phytochelatins, are involved in As accumulation and detoxification in E. cannabinum, we analyzed the synthesis of these compounds in the presence and absence of As and/or citric acid. Our results suggest that these thiolic compounds play a major role in As detoxification, since the presence of CA as a chelating agent reduced the amount of thiols necessary to cope with the toxicity caused by As. [ABSTRACT FROM AUTHOR]

A field survey was conducted to investigate metal(loid) concentration in soils and native plants in the Baoshan mining area for potential application in phytoremediation. Total concentrations of arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) in soil varied from 125 to 6656, 5.10 to 1061, 568 to 49294, and 241 to 17296 mg kg−1, respectively, showing severe contamination. Among 20 species native to this area, Pteris ensiformis accumulated 1091 mg kg−1 As in the shoot, and its translocation factor (TF) was greater than 1, suggesting potential capacity for As phytoextraction. Boehmeria nivea, Aster prorerus, and Hydrocotyle sibthorpioides showed potential for phytoextraction of Cd due to their high accumulation of Cd in shoots (490.3, 175.4, and 128.5 mg kg−1, respectively) and high TFs (92.0, 22.1, and 6.7, respectively). Eleusine indica and P. ensiformis were found to contain high concentrations of Pb (7474 mg kg−1) and Zn (1662 mg kg−1) in roots, but with low TFs for Pb (0.4) and Zn (0.2), suggesting potential capability for phytostabilization. There was a positive correlation (p < 0.01, N = 25) of TFs between the metal(loid)s, indicating a synergic interaction in the uptake of metal(loid)s by these plants. According to metal(loid) concentrations in shoots, bioconcentration factors (BFs), and TFs, as well as the botanical features such as wide occurrence, high biomass yield, and rapid growth of the plants, the five native species identified above have the potential for phytoremediation in the Baoshan mining area. [ABSTRACT FROM AUTHOR]

In recent years, ornamental plants have come under investigation as phytoremediation agents. In addition to reducing contaminant concentrations in soil, such plants support local economies by serving social (e.g., religious) and decorative purposes. Greenhouse studies investigated the phytostabilization potential of soil cadmium (Cd) by five cultivars of marigold (Tagetes erecta), a common ornamental flower in Asia. The effects of organic (cattle manure and pig manure) and inorganic (leonardite and Osmocote®) amendments in supporting plant growth and enhancing Cd uptake were also examined. Marigold cultivars Babuda and Sunshine grown in soil supplemented with pig manure produced the greatest biomass and experienced greatest Cd accumulation and flower production. In all treatments, plant parts accumulated Cd in the following order: root > shoot ≈ flower. Furthermore, Babuda and Sunshine cultivars had a high phytostabilization potential as evidenced by translocation factors < 1 and bioconcentration factors > 1 for roots. It is proposed that Babuda and Sunshine marigold cultivars be applied toward Cd phytostabilization while enhancing local economies as an ornamental species. [ABSTRACT FROM AUTHOR]

Plants growing in areas polluted by heavy metals represent excellent models for the investigations related to their potentials for hazardous metals accumulation which further may help in the estimation of plant practical biomonitoring and phytoremediation potentials. In this study, the potentials of the grapevine cultivar Tamjanika from a highly polluted region in Eastern Serbia, with intensive copper mining and metallurgical activities, were estimated in regard to the potentially toxic elements such as iron and manganese; the potential danger from these metals through fruit consummation is also considered. Used methods were the following: ICP-OES analysis, calculation of biological coefficients, the Pearson correlation study, one-way ANOVA, and hierarchical cluster analysis. The results revealed that a great majority of the recorded concentrations in different plant organs were in the range of normal concentrations, as well as that the calculated accumulation rates for both metals were very low. The data also pointed to generally minimal to moderate enrichment by these metals which represents totally dissimilar situation in comparison with other heavy metals detected in the very same plant samples. The results of this study suggested that the investigated plants of the grapevine cv Tamjanika assimilated iron and manganese predominately according to their individual needs, and confirmed that the utilization of this plant species can be very effective in different biomonitoring procedures and also in the phytoremediation procedure known as phytostabilization. At the same time, it was obvious that even in aggressive circumstances its fruit was protected from some serious contamination and kept pretty safe for consummation. [ABSTRACT FROM AUTHOR]

Interactions between heavy metals in soil could affect soil heavy metal availability and plant uptake. Thus, in this study, Cd and Pb accumulation as well as plant growth of the mining ecotype (ME) and non-mining ecotype (NME) of Athyrium wardii (Hook.) in response to the exposure of Cd and Pb was investigated by a pot experiment. Although the exposure of Cd in combination with Pb further inhibited the growth of the two ecotypes in comparison with the exposure of single Cd or Pb, the ME presented lower biomass decline for the whole plant (22.0%-70.0%) than the NME among most treatments. The presence of Pb promoted Cd accumulation both in above-ground and under-ground parts of the ME. Cd concentrations in under-ground parts of the ME decreased when exposed to higher concentrations of Pb (> 600 mg kg−1). Meanwhile, the presence of Cd inhibited Pb accumulation in above-ground parts of the ME and promoted Pb accumulation in under-ground parts of the ME. Pb concentrations in under-ground parts of the ME decreased when soil Cd concentrations were more than 25 mg kg−1. The partial correlation analysis further demonstrated that the interactions between Cd and Pb stimulated Cd accumulation both in above-ground and under-ground parts of the ME and Pb accumulation in under-ground parts of the ME, while inhibited Pb accumulation in above-ground parts of the ME, showing great benefit for Pb phytostabilization by the ME. Among treatments, the bioaccumulation coefficients for Cd and Pb of the ME, varying from 2.71-31.05 and 20.09-78.06, were much higher than those of the NME. The translocation factors for Cd and Pb of the ME, varying from 0.26-0.52 and 0.01-0.10, were lower than those of the NME. These results indicate that the ME presented greater potential for the phytostabilization of soil contamination with Cd and Pb, especially for Pb. [ABSTRACT FROM AUTHOR]

Selecting plant species, especially woody species, that can tolerate and accumulate high levels of heavy metals is crucial for the purpose of phytoremediation. In the present study, seven willow species/clones were evaluated for their variations in copper (Cu) tolerance, Cu accumulation, and their relative physiological responses, when exposed to different doses of Cu (control, 15, and 120 μM) in a hydroponic system for 40 days. Upon Cu exposure, all tested willow species/clones (Salix, S.) remained relative normal growth, albeit with some visual evidence of Cu toxicity observed. Seven willow species remained relative high total biomass with tolerance index > 0.6 when being exposed to 120 μM Cu, suggesting their high Cu tolerance. Exposure to 120 μM Cu resulted in notable declines (16.3-76.1%) in photosynthesis in all willow species. Increases in the soluble sugar content and decreases in the soluble protein content in the leaves of five willow species (S. integra “Yizhibi”, S. jiangsuensis “J172”, S. matsudana 14, S. matsudana 25, S. matsudana 89) were found in the 120 μM Cu treatment. The majority of Cu mainly accumulated in the roots, ranging from 1916 to 26,244 mg kg−1 DW. Principal component analysis and membership function analysis suggested that S. matsudana 89 and S. matsudana 25 showed much higher biomass and accumulation ability than the other species. This suggests that these two willow clones could be used as potential candidates for the phytostabilization of Cu in contaminated soils. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) may be toxic to aquatic plants even at modest concentrations, and excessive quantities of zinc (Zn) decrease plant performance. The Cd and Zn phytoremediation potential of several aquatic plant species (Thalia geniculate, Cyperus alternifolius, Canna indica, Eichhornia crassipes, Pistia stratiotes) and one grass species (Vetiveria zizanioides) was evaluated in hydroponic experiments. Vetiveria zizanioides, E. crassipes, and P. stratiotes experienced reduced growth performance in the presence of Cd as determined from biomass production, survival rate, and crown root number (CN); however, they accumulated high quantities of metals in their tissues, particularly in roots. Root accumulation is considered a key characteristic of so-called excluder species. In this study, only E. crassipes and P. stratiotes had bioconcentration factors and translocation factors (> 1000 and < 1, respectively) suitable for high phytostabilization of Cd. Furthermore, V. zizanioides and P. stratiotes showed the highest percent metal uptake from solution and removal capacity for Zn (~70% and ~2 mg d−1 g−1, respectively). Emergent aquatic species (particularly C. alternifolius and T. geniculate) adapted and lived well in Cd- and Zn-contaminated solution and took up high quantities of Cd and Zn in roots, and are therefore considered strong excluders. Beneficial uses of such species in contaminated wetlands include stabilizing toxic metals and limiting erosion. Plant tissue can be applied to other uses, including as a biomass fuel. In field situations, the candidate species may work best when grown together, since each plant genotype possesses a different potential to control Cd and Zn. [ABSTRACT FROM AUTHOR]

The phytoremediation of copper (Cu)-contaminated sandy soils can be influenced by the addition of vermicompost to the soil and the mycorrhization of plants. The objective of this study was to evaluate the effects of inoculation with the mycorrhizal fungus Rhizophagus clarus and the addition of different doses of bovine manure vermicompost on the phytoremediation of a sandy soil with a high Cu content using Canavalia ensiformis. Soil contaminated with 100 mg kg−1 Cu received five doses of vermicompost and was cultivated with C. ensiformis, with and without inoculation with mycorrhizal fungus, and the Cu and nutrients in the soil and soil solution were evaluated. The concentrations of Cu and other nutrients and the biomass and Cu phytotoxicity in the plants were quantified by gauging the photochemical efficiency, concentration of photosynthetic pigments and activity of oxidative stress enzymes. The vermicompost increased the soil pH and nutrient concentrations and reduced the Cu content of the solution. When the vermicompost was applied at a dose equivalent to 80 mg phosphorus (P) kg−1, the phytoextraction efficiency was higher, but the phytostabilization efficiency was higher for vermicompost doses of 10 and 20 mg P kg−1. The presence of mycorrhizal fungi increased Cu phytostabilization, especially at vermicompost doses of 10 and 20 mg P kg−1. The use of vermicompost at low doses and inoculation with mycorrhizal fungi increase the phytostabilization potential of C. ensiformis in sandy soil contaminated by Cu. [ABSTRACT FROM AUTHOR]

We examine the feasibility of phytoremediation as an alternative strategy to limit the exposure of asbestos in site with asbestos-containing materials. We collected soils from four locations from two sites-one with naturally occurring asbestos, and another, a superfund site, where asbestos-containing materials were disposed over decades-and performed ecotoxicology tests. We also performed two experiments with crop cultivar and two grasses from serpentine ecotype and cultivar to determined best choice for phytoremediation. Asbestos concentrations in different size fractions of soils varied by orders of magnitude. However, different asbestos concentrations had little effect on germination and root growth. Presence of co-contaminants such as heavy metals and lack of nutrients affected plant growth to different extents, indicating that several of these limiting factors should be considered instead of the primary contaminant of concern. Crop cultivar survived on asbestos-contaminated soil. Grasses from serpentine ecotype did not show higher biomass than the cultivar. Overall, these results showed that soil conditions play a critical role in screening different crop species for phytoremediation and that asbestos concentration has limited to no effect on plant growth. Our study provided a framework for phytoremediation of asbestos-contaminated sites to limit long-term asbestos exposure. [ABSTRACT FROM AUTHOR]

A hydroponic culture experiment was performed to investigate the effects of endophytic Bacillus megaterium H3 on the plant biomass, Cd accumulation and tolerance of hybrid pennisetum, and the mechanisms involved in the different levels of Cd-contaminated aquatic environments. Strain H3 significantly increased the plant growth (ranging from 13 to 71 %) and total Cd uptake (ranging from 41 to 160 %) but decreased Cd translocation factors of hybrid pennisetum treated with 0-20 μM Cd compared with the controls. Furthermore, most of Cd (71-77 %) was accumulated in the roots of the bacterial-inoculated hybrid pennisetum. Notably, strain H3 could significantly increase the production of oxalic and propanedioic acids (ranging from 18 to 188 %) but decrease the production of phytochelatins of hybrid pennisetum compared to the controls under different levels of Cd stress. The live bacterial-induced increase in organic acid production and decrease in phytochelatins production by hybrid pennisetum might be responsible for the increased plant growth, root Cd accumulation, and Cd toxicity alleviation of the plant under different levels of Cd stress. The results highlight that hybrid pennisetum plus endophytic B. megaterium H3 may be utilized for biomass production and Cd phytostabilization of the plant in the different levels of Cd-contaminated aquatic environments. [ABSTRACT FROM AUTHOR]

Vegetation indices obtained from radiometric measurements have been used to estimate the stress response of plants grown in contaminated sites. The phytotoxicity of Pb and Zn in Festuca rubra L. and Vulpia myuros L. plants grown under hydroponic conditions was evaluated using vegetation indices obtained from radiometric measurements. The plants were supplied with 3 mM Zn (+Zn), 500 μM Pb (+Pb) and 500 μM Pb with EDTA (+PbEDTA) for 3 months. Significantly higher Zn concentrations in F. rubra shoots compared with V. myuros shoots were detected for Zn and Pb treatments. EDTA increased Pb transport to the shoots for both grasses, while Pb-treated plants retained Pb primarily in the roots. All vegetation indices tested showed the highest differences in F. rubra under +PbEDTA treatment and minor effects under +Zn, whereas the major variations for V. myuros corresponded to +Zn treatment, followed by +PbEDTA. Red edge normalized difference vegetation index, yellowness index and anthocyanin concentration index were the most sensitive indices to report Zn and Pb phytotoxicity in these grasses. According to the results obtained, both metal concentrations and radiometric indices suggested that Pb is more phytotoxic to F. rubra, which tolerates high Zn levels, whereas V. myuros was strongly affected by high Zn levels and markedly tolerant to Pb, even when applied in a mobile form (PbEDTA). Both species could be used in the phytostabilization of Zn- and Pb-contaminated soils. The abilities of F. rubra to accumulate Zn and V. myuros to accumulate Pb in the roots would facilitate a more efficient phytoremediation strategy when used in combination. [ABSTRACT FROM AUTHOR]

Soil contamination by cadmium (Cd) poses a serious environmental and public health concern. Phytoremediation, i.e., the use of plants to remove contaminants from soil, has been proposed for treatment of Cd-contaminated ecosystems. In this study, we demonstrated the potential of Vetiveria zizanioides, commonly known as vetiver, to serve as an effective phytoremediation agent. Two ecotypes, i.e., India and Sri Lanka, were grown in greenhouse pots and in the field. Soils were amended with cow manure, pig manure, bat manure, and an organic fertilizer. Among all amendments, pig manure performed best in both greenhouse and field studies in terms of increasing total V. zizanioides biomass production in both ecotypes. In both greenhouse and in the field, tissue of the Sri Lanka ecotype had higher Cd concentrations than did the India ecotype. In the greenhouse, the presence of Cd did not affect total biomass production or root dry weight. The Sri Lanka ecotype had 2.7 times greater adventitious root numbers and 3.6 times greater Cd accumulation in roots than did the India ecotype. In the field study, the Sri Lanka ecotype offers potential as an excluder species, as it accumulated Cd primarily in roots, with translocation factor values <1 and a bioconcentration coefficient for roots >1 for all experiments except for the pig manure amendment. In addition, the highest Cd concentration in the Sri Lanka ecotype root (71.3 mg kg) was consistent with highest Cd uptake (10.4 mg plant) in the cow manure treatment. The India ecotype contained lower root Cd concentrations, and Cd accumulation was slightly higher in shoots compared to roots, with translocation factor (TF) values >1. The India ecotype was therefore not considered as an excluder in the Cd-contaminated soil. With the use of excluder species combined with application of organic amendments, soil contamination by Cd may be treated by alternative remediation methods such as phytostabilization. [ABSTRACT FROM AUTHOR]

The application of organic amendments into heavy metal contaminated soil is considered as an environmentally friendly technique to promote the potential of phytoremediation. A pot experiment was carried out to evaluate the effect of humic substances on growth, cadmium (Cd) accumulation and phytostabilization potential of the mining ecotype (ME) and the corresponding non-mining ecotype (NME) of Athyrium wardii (Hook.) grown in Cd-contaminated soils. The addition of the humic substances demonstrated great promotion for the growth and Cd uptake of ME. Both plant biomass and Cd concentration significantly increased with the increasing application of the humic substances up to 100 g kg, beyond which no significant change of underground part biomass and Cd concentrations in underground part of A. wardii was observed. The maximum Cd concentration in underground part of ME was 180 mg kg when 150 g kg humic substances were applied. The ME showed greater Cd accumulation capability in underground part (0.47-0.68 mg plant) than that of NME (0.27-0.45 mg plant). Increasing bioaccumulation coefficient (BCF) values of A. wardii was observed with increasing application of the humic substances. The BCF values of ME were higher than those of NME. However, the use of the humic substances exhibited little impact on translocation factors (TFs) of ME, and the TF values of ME were less than NME. Furthermore, the application of the humic substances improved the remediation factors (RFs) of A. wardii. The RF values in underground part of ME ranging from 0.73 to 0.91 % were apparently higher than those of NME. These results indicated that the humic substances can be a potential candidate for enhancing the phytostabilization of A. wardii grown in Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

Phytoremediation of contaminated mine soils requires the use of fast-growing, deep-rooted, high-biomass, and metal-tolerant plants with the application of soil amendments that promote metal uptake by plants. A pot experiment was performed to evaluate the combined use of vetiver grass ( Chrysopogon zizanioides) and humic acid for phytoremediation of Cu and Zn in mine soils. Vetiver plants were grown in soil samples collected from two mine sites of Spain mixed with a commercial humic acid derived from leonardite at doses of 0, 2, 10, and 20 g kg. Plant metal concentrations and biomass were measured and metal bioavailability in soils was determined by a low molecular weight organic acid extraction. Results showed that humic acid addition decreased organic acid-extractable metals in soil. Although this extraction method is used to estimate bioavailability of metals, it was not a good estimator under these conditions due to competition with the strong chelators in the added humic acid. High doses of humic acid also promoted root growth and increased Cu concentrations in plants due to formation of soluble metal-organic complexes, which enhanced removal of this metal from soil and its accumulation in roots. Although humic acid was not able to improve Zn uptake, it managed to reduce translocation of Zn and Cu to aerial parts of plants. Vetiver resulted unsuitable for phytoextraction, but our study showed that the combined use of this species with humic acid at 10-20 g kg could be an effective strategy for phytostabilization of mine soils. [ABSTRACT FROM AUTHOR]

In a greenhouse pot experiment, lettuce plants ( Lactuca sativa L.) were grown in a Hg-contaminated sandy soil with and without inoculation with arbuscular mycorrhizal fungi (AMF) (a commercial inoculum containing infective propagules of Rhizophagus irregularis and Funneliformis mosseae) amended with different rates of a humic acid (0, 1, and 2 g kg of soil), with the objective of verifying the synergistic effects of the two soil treatments on the Hg tolerance of lettuce plants. Our results indicated that the plant biomass was significantly increased by the combined effect of AMF and humic acid treatments. Addition of humic matter to soil boosted the AMF effect on improving the nutritional plant status, enhancing the pigment content in plant leaves, and inhibiting both Hg uptake and Hg translocation from the roots to the shoots. This was attributed not only to the Hg immobilization by stable complexes with HA and with extraradical mycorrhizal mycelium in soil and root surfaces but also to an improved mineral nutrition promoted by AMF. This work indicates that the combined use of AMF and humic acids may become a useful practice in Hg-contaminated soils to reduce Hg toxicity to crops. [ABSTRACT FROM AUTHOR]

Pb pollution caused by shooting sport activities is a serious environmental problem that has increased considerably in recent decades. The aims of this study were firstly to analyze Pb pollution in soils from a trap shooting range abandoned in 1999, secondly to study the effectiveness of different extractants [CaCl, DTPA, NHOAc, low molecular weight organic acids (LMWOA), and bidistilled water (BDW)] in order to determine Pb bioavailability in these soils, and finally to evaluate the phytoremediation ability of spontaneous vegetation ( Agrostis capillaris L.). To this end, 13 soils from an old trap shooting range (Galicia, NW Spain) were studied. It was found that Pb levels in the soils were higher than 100 mg kg, exceeding the generic reference levels, and three of these samples even exceeded the USEPA threshold level (400 mg kg). In general, the reagent that best represents Pb bioavailability and has the greatest extraction efficiency was CaCl, followed by DTPA, NHOAc, LMWOA, and BDW. A. capillaris Pb contents ranged between 9.82 and 1107.42 mg kg (root) and between 6.43 and 135.23 mg kg (shoot). Pb accumulation in roots, as well as the presence of secondary mineral phases of metallic Pb in the adjacent soil, showed the phytostabilization properties of A. capillaris. [ABSTRACT FROM AUTHOR]

The synergistic activity between plants and microorganisms may contribute to the implementation of proactive management strategies in the stabilization of contaminated sites, although heavy metals, such as cadmium (Cd), are potentially toxic to them. The aim of this study was to evaluate the degree of tolerance to Cd contamination (supplying twice 40 mg kg of Cd) in poplar cuttings [clone I-214, P. × euramericana (Dode) Guinier] inoculated or not with two concentrations of Serratia marcescens strain (1 × 10 CFU/g and 2 × 10 CFU/g of potting mix). The response of the plant-bacteria system to excess Cd was investigated with special reference to the structural traits of plants and the functional efficiency of bacteria. Bacterial colonization and substrate components were previously assessed in order to define the best solution for formulating the experimental plant growth media. The tested plant-bacteria association, especially when bacteria were provided in double concentration, stimulated specific tolerance mechanisms to Cd through the promotion of the poplar growth. Inoculated plants produced larger leaves and increased stem diameter, while roots grew longer and wider in Cd-treated plants. The effect of bacterial inoculum on plant growth traits and metal partitioning in plant organs was assessed in order to define the potential of this poplar clone to be a suitable candidate for phytostabilization of Cd-contaminated soil. The final effect of the inoculation with bacteria, which alleviated the metal load and Cd phytotoxicity due to their bioaccumulation ability, suggests promising phytostabilization potential of these plant-bacteria associations. [ABSTRACT FROM AUTHOR]

This study aimed at assessing the effect of nitrogen addition under two forms, nitrate and ammonium, on the stabilization of Zn, Pb, and Cd by Populus euramericana Dorskamp grown in contaminated soils for 35 days under controlled conditions. Temporal changes in the soil pore water (SPW) were monitored for pH, dissolved organic carbon (DOC), and total dissolved concentrations of metals in the soils rhizosphere. Rhizospheric SPW pH decreased gradually with NH addition and increased with NO addition up to one unit, while it slightly decreased initially then increased for the untreated control soil DOC increased with time up to six times, the highest increase occurring with NH fertilization. An increase in the metal concentrations in the rhizospheric SPW was observed for NH addition associated with the lowest rhizospheric SPW pH, whereas the opposite was observed for the control soil and NO fertilization. Fertilization did not affect plant shoots or roots biomass development compared to the untreated control (without N addition). Metals were mostly accumulated in the rhizosphere and N fertilization increased the accumulation for Zn and Pb while Cd accumulation was enhanced for NH addition. Collectively, our results suggest metal stabilization by P. euramericana Dorskamp rhizosphere with nitrogen fertilization and are potential for phytostabilization of contaminated technosol. [ABSTRACT FROM AUTHOR]

The aim of this work was to assess the suitability of Miscanthus × giganteus and Spartina pectinata link to Cu, Ni, and Zn phytoremediation. A 2-year microplot experiment with the tested grasses growing on metal-contaminated soil was carried out. Microplots with cement borders, measuring 1 × 1 × 1m, were filled with Haplic Luvisols soil. Simulated soil contamination with Cu, Ni, and Zn was introduced in the following doses in mg kg: 0-no metals, Cu-100, Cu-200, Cu-400, Ni-60, Ni-100, Ni-240, Zn-300, Zn-600, and Zn-1200. The phytoremediation potential of grasses was evaluated using a tolerance index (TI), bioaccumulation factor (BF), bioconcentration factor (BCF), and translocation factor (TF). S. pectinata showed a higher tolerance to soil contamination with Cu, Ni, and Zn compared to M. × giganteus. S. pectinata was found to have a high suitability for phytostabilization of Zn and lower suitability of Cu and Ni. M. × giganteus had a lower phytostabilization potential than S. pectinata. The suitability of both grasses for Zn phytoextraction depended on the age of the plants. Both grasses were not suitable for Cu and Ni phytoextraction. The research showed that one-season studies were not valuable for fully assessing the phytoremediation potential of perennial plants. [ABSTRACT FROM AUTHOR]

In this study, the samples of the spatial soil and organs of the grapevine ( Vitis vinifera) cultivar Tamjanika were collected from the selected zones near the Mining and Smelting Complex Bor (East Serbia). They were analyzed by ICP-OES to determine the content of Cu, Zn, Pb, As, Cd, and Ni with the aim of ascertaining if these data may help in the assessment and improvement of the quality of environment in polluted areas such as Bor and its surrounding area. The results obtained from the calculated biological and enrichment factors, as well as from the Pearson correlation study and hierarchical cluster analysis confirmed that very useful information is recorded in plant organs: root, stem, leaves, and fruit. Yet, when the atmospheric pollution is the sphere of interest, the most informative data are found in unwashed leaves. The results of this study indicated also that the investigated plant species has some highly effective strategies involved in tolerance to the stress induced by heavy metals, which makes it an excellent candidate for phytostabilization purposes. Planting of this grapevine cultivar can be recommended in all areas that are severely polluted with heavy metals. [ABSTRACT FROM AUTHOR]

The in situ stabilization of metals in soils using plants with great biomass value is a promising, cost-effective, and ecologically friendly alternative to manage metal-polluted sites. The goal of phytostabilization is to reduce the bioavailable concentrations of metals in polluted soil and thus reduce the risk to the environment and human health. In this context, this study aimed at evaluating Miscanthus × giganteus efficiency in phytostabilizing metals on three contaminated agricultural sites after short-term exposure under greenhouse conditions and after long-term exposure under field conditions. Particular attention was paid to the influence of Miscanthus cultivation on (i) Cd, Pb, and Zn fractionation using sequential extractions and (ii) metal bioaccessibility using an in vitro gastrointestinal digestion test. Data gave evidence of (i) different behaviors between the greenhouse and the field; (ii) metal redistribution in soils induced by Miscanthus culture, more specifically under field conditions; (iii) higher environmental availability for Cd than for Pb and Zn was found in both conditions; and (iv) overall, a higher bioaccessible fraction for Pb (about 80 %) and Cd (65-77 %) than for Zn (36-52 %) was recorded in the gastric phase, with a sharp decrease in the intestinal phase (18-35 % for Cd, 5-30 % for Pb, and 36-52 % for Zn). Compared to soils without culture, the results showed that phytostabilization using Miscanthus culture provided evidence for substantial effects on oral bioaccessibility of Cd, Pb, and Zn. [ABSTRACT FROM AUTHOR]

Major endogenous biochemical properties can make plants ideal agents for metal/metalloid-contaminated site cleanup. This study investigates the biochemistry of Juncus maritimus (Lam) roots for its high mercury (Hg) stabilization potential in the sediments of the Ria de Aveiro coastal lagoon (Portugal), which received Hg-rich effluents from a chlor-alkali industry between 1950 and 1994. J. maritimus plants were collected at a reference (R) site and three sites with the highest (L1), moderate (L2), and the lowest (L3) Hg contamination levels. The highest Hg-harboring/stabilizing J. maritimus roots at L1, exhibited significantly elevated damage endpoints (HO; lipid peroxidation, LPO; electrolyte leakage, EL; protein oxidation, PO; proline) which were accompanied by differential changes in HO-metabolizing defense system components (ascorbate peroxidase, catalase, glutathione peroxidase, glutathione S-transferase), glutathione reductase and the contents of both reduced and oxidized glutathione. Trends in measured endpoints reached maximum levels at L1 followed by L2 and L3. Cross-talks on root-Hg status and the studied biochemical traits revealed (a) high Hg-accrued elevations in oxidative stress as an obvious response; (b) Hg-stabilization potential of J. maritimus roots as a result of a successful mitigation of elevated high Hg-induced HO, and its anomalies such as LPO, EL, and PO; and (c) the induction of and a fine synchronization between non-glutathione and glutathione-based systems. Overall, the study unveiled biochemical mechanisms underlying root tolerance to Hg burden-accrued anomalies which, in turn, helped J. maritimus during Hg-stabilization. [ABSTRACT FROM AUTHOR]

This work was planned for providing useful information about the use of excluder metallophytes for phytostabilization of soils contaminated also with elements scarcely represented in the metalliferous environment of origin. To this aim, we investigated tolerance and accumulation of several different elements in a metallicolous and a nonmetallicolous population of Silene paradoxa through a hydroponic experiment. S. paradoxa metallicolous population showed increased tolerance not only to all the metals highly represented in the environment of origin but also to some of those scarcely present. Therefore, our results deposed in favor of the occurrence of the co-tolerance phenomenon in S. paradoxa for some elements. Metal accumulation was higher in the roots than in the shoots and lower in the metallicolous population than in the nonmetallicolous one, thus showing tolerance mechanisms to be based largely on metal exclusion. Anyway, the relative contribution of avoidance and of internal tolerance to metal tolerance was shown to be element-dependent. Present data revealed that metallicolous plants can effectively posses metal co-tolerances, which deserve to be investigated; as such, plants can actually represent a precious and exploitable tool also for the phytostabilization of soils contaminated with elements underrepresented in the environment of their origin. [ABSTRACT FROM AUTHOR]

A greenhouse experiment was carried out in order to investigate the effects of arbuscular mycorrhizal (AM) fungi inoculation and the use of composted olive waste (COW) in the establishment of Tetraclinis articulata and soil properties in a heavy metal-polluted soil. The treatments assayed were as follows: AM + 0 % COW, AM + 1 % COW, and AM + 3 % COW. The higher doses of COW in combination with AM fungi increased shoot and root biomass production of T. articulata by 96 and 60 %, respectively. These treatments trended to improve the soil properties evaluated, highlighting the C compounds and N as well as the microbiological activities. In relation to the metal translocation in T. articulata, doses of COW applied decreased the Cr, Ni, and Pb contents in shoot, as well as Cr and As in root, although the most of them reached low levels and far from phytotoxic. The COW amendment aided Glomus mosseae-inoculated T. articulata plants to thrive in contaminated soil, mainly through an improvement in both nutrients uptake, mainly P and soil microbial function. In addition, the combined use of AM fungi plus COW could be a feasible strategy to be incorporated in phytoremediation programs because it promotes soil properties, a better performance of plants for supporting the stress in heavy metal-contaminated soils derived from the mining process, and also can be a good way for olive-mill waste disposal. [ABSTRACT FROM AUTHOR]

Phytostabilization has great practical significance and flexibility in the ecological restoration of mining tailings and remediation of heavy metals polluted soils. However, potential use of metallophytes in phytostabilization is limited by a lack of knowledge of many basic plant processes. A mining ecotype (ME) Athyrium wardii, Pb/Cd phytostabilizer, and a non-mining ecotype (NME) A. wardii were grown in a pot experiment to investigate the chemical characteristics of the rhizosphere when exposed to the Cd polluted soils. Rhizobags were used to collect rhizosphere and bulk soils, separately. The results indicated that the ME A. wardii was more efficient in Cd accumulation in the root than NME after growing in Cd polluted soils for 50 days in a green house. Soil solution pH and dissolved organic carbon (DOC) concentration in the rhizosphere of ME A. wardii were higher than in the bulk soil and initial values (before planting), whereas the increment in the ME A. wardii were greater than NME. Owing to the increasing of rhizosphere soil pH, exchangeable Cd significantly decreased, whereas the other Cd species were increased with increasing soil DOC values. It is assumed that the ME A. wardii was effective in stabilizing Cd from the mobile fraction to non-mobile fractions. Results from this study suggest that rhizosphere alkalinization and the exudation of high amounts of dissolved organic matter (DOM) to reduce heavy metal mobility might be the two important mechanisms involved in the metal tolerance/accumulation of ME A. wardii. [ABSTRACT FROM AUTHOR]