Phytoremediation Applications Research Articles

Phytoremediation in Disinfection of Water from Underground Sources: Perception Study

Application of phytoremediation in disinfection was studied using extracts of Tulsi, Neem and Amla in underground water in rural area of eastern Pune metropolitan region. The perception study involved understanding the potential of hydroalcoholic extracts of leaves of Tulsi, Neem and Amla in disinfection of underground water. Secondly optimizing the dose and time required for complete disinfection by the extracts. Thirdly a liquid herbal preparation for disinfection using extracts was formulated and studied, and also further used for achieving complete disinfection of onsite households’ water. The disinfection effect of crude powder of leaves of plants was also noted. Study area being agrarian area, a survey was taken to create awareness and highlight the outcome of the studies done so far. The 3M petri film method was used for disinfection study. The extracts of Tulsi, Neem and Amla completely disinfected 10ml of water at a dose of 10.56mg, 21.4mg and 12.03mg respectively. Herbal preparation containing 90mg extracts completely disinfected 500ml of underground water of study sites and households. The responses of crude powder were very less potent as compared to extracts. Finally, the results conclude that phytoremediation by commonly and abundantly available plants can be used for disinfection.

The Effect of Fertilizer on Epipremnum Aureum in Phytoremediating Soil Contaminated with Crude Oil

Epipremnum aureum is a common ornamental foliage which is used mainly for indoor decoration. It demonstrates tolerance to low light environment and the ability to remove atmospheric chemicals such as gasoline and formaldehyde. A previous screening study showed the ability of Epipremnum aureum to remove crude oil from soil. Further to the screening study, this study examined the effect of fertilization on phytoremediation of crude oil-contaminated soil by Epipremnum aureum Epipremnum aureum was grown in pots with soil contaminated with 5%, 10% and 15% of crude oil by weight respectively, with and without the addition of fertilizer. In line with previous study, Epipremnum aureum showed the ability to remove crude oil contaminants. The plant demonstrated highest crude oil removal rate in pots with 15% contamination. Application of fertilizer enhanced the removal of crude oil in all experimental pots by Week 6, hence increasing the rate of crude oil decline over the experimental duration. It is deemed that application of fertilizer provides nutrients to promote plant growth and proliferation of roots which enhance rhizodegradation of crude oil in soil. This study extends on the existing knowledge that Epipremnum aureum can phytoremediate crude-oil contaminated soil by characterizing its tolerance to crude oil and its response to fertilization, which is crucial to its practical application in phytoremediation. Phytoremediation presents a promising yet cost-effective measure in treating contaminated land. Further study can examine the optimum fertilizer concentration for phytoremediation and the tolerance level of Epipremnum aureum to crude oil contamination.

Residue in the Mangrove Surface Sediment with the Feasibility of Phytoremediation Application

The present study investigated heavy metal contaminations in the mangrove surface sediment of Rayong coast, Thailand. Sediment samples were collected from 5 locations with each 3 sampling sites and analyzed for heavy metal (Cu, Pb, Cr, Zn and Mn) contents using microwave digestion and MP-AES. The results revealed that concentrations of the heavy metals ranged from 10.54-66.53 mg/kg for Cu, 21.71-116.40 mg/kg for Pb, 21.21-66.66 mg/kg for Cr, 17.67-397.01 mg/kg for Zn and 46.55-1609.53 mg/kg for Mn. Although, the concentrations of Cu, Pb and Zn in surface sediments exceed the effects range low (ERL), did not exceed the effects range median (ERM) of the guidelines. Meanwhile, the feasibility of treating a heavy metal-contaminated soil via mangrove phytoremediation showed the removal efficiency of heavy metals contaminated in sediment occurred in descending order of Mn>Pb>Cr>Cu>Zn (93.11, 80.42, 70.03, 67.09 and 52.50 %, respectively). After spiked more concentration of heavy metals, decreasing removal efficiency was occurred in all treatments that might be caused of the higher heavy metal intake. Beside of these contaminated conditions, the mangrove plants can still survived after 30 days. Which indicated the tolerated to the high level of heavy metals.

Physiological Response of Populus balsamifera and Salix eriocephala to Salinity and Hydraulic Fracturing Wastewater: Potential for Phytoremediation Applications.

Natural and anthropogenic soil degradation is resulting in a substantial rise in the extension of saline and industrially-polluted soils. Phytoremediation offers an environmentally and economically advantageous solution to soil contamination. Three growth trials were conducted to assess the stress tolerance of native Canadian genotypes of Populus balsamifera L., Salix eriocephala Michx., and one hybrid willow (S. discolor × S. dasyclados) to salinity and hydraulic fracturing (fracking) wastewater. Thirty-three genotypes were grown in NaCl or fracking wastewater solutions between 0 and 7 mS−1 over a period of 3–4 months. P. balsamifera was observed to be relatively salt-intolerant compared to S. eriocephala and hybrid willow, which is likely caused by an inability of P. balsamifera to restrict Na+ translocation. Photosynthesis and transpiration decreased with salinity treatments, and severe reductions occurred with exposure to fracking solutions. Raffinose and stachyose content was tripled in leaf and root tissues. In willows, Na+ was primarily confined to root tissues, Cl− accumulated up to 5% dry weight in leaves, and K+ was translocated from roots to leaves. Willow genotypes CAM-2 and STL-2 displayed the greatest maintenance of growth and resistance to necrotic symptoms in all trials, suggesting that these genotypes may be useful for practical application and further field study.

Patents on Endophytic Fungi for Agriculture and Bio- and Phytoremediation Applications.

Plant endophytic fungi spend all or part of their lives inside host tissues without causing disease symptoms. They can colonize the plant to protect against predators, pathogens and abiotic stresses generated by drought, salinity, high concentrations of heavy metals, UV radiation and temperature fluctuations. They can also promote plant growth through the biosynthesis of phytohormones and nutrient acquisition. In recent years, the study of endophytic fungi for biological control of plant diseases and pests has been intensified to try to reduce the ecological and public health impacts due the use of chemicals and the emergence of fungicide resistance. In this review, we examine 185 patents related to endophytic fungi (from January 1988 to December 2019) and discuss their applicability for abiotic stress tolerance and growth promotion of plants, as agents for biocontrol of herbivores and plant pathogens and bio- and phytoremediation applications.

A review on phytoremediation of contaminants in air, water and soil

There is a global need to use plants to restore the ecological environment. There is no systematic review of phytoremediation mechanisms and the parameters for environmental pollution. Here, we review this situation and describe the purification rate of different plants for different pollutants, as well as methods to improve the purification rate of plants. This is needed to promote the use of plants to restore the ecosystems and the environment. We found that plants mainly use their own metabolism including the interaction with microorganisms to repair their ecological environment. In the process of remediation, the purification factors of plants are affected by many conditions such as light intensity, stomatal conductance, temperature and microbial species. In addition the efficiency of phytoremediation is depending on the plants species-specific metabolism including air absorption and photosynthesis, diversity of soil microorganisms and heavy metal uptake. Although the use of nanomaterials and compost promote the restoration of plants to the environment, a high dose may have negative impacts on the plants. In order to improve the practicability of the phytoremediation on environmental restoration, further research is needed to study the effects of different kinds of catalysts on the efficiency of phytoremediation. Thus, the present review provides a recent update for development and applications of phytoremediation in different environments including air, water, and soil.

Low-molecular-weight ligands in plants: role in metal homeostasis and hyperaccumulation.

Mineral nutrition is one of the key factors determining plant productivity. In plants, metal homeostasis is achieved through the functioning of a complex system governing metal uptake, translocation, distribution, and sequestration, leading to the maintenance of a regulated delivery of micronutrients to metal-requiring processes as well as detoxification of excess or non-essential metals. Low-molecular-weight ligands, such as nicotianamine, histidine, phytochelatins, phytosiderophores, and organic acids, play an important role in metal transport and detoxification in plants. Nicotianamine and histidine are also involved in metal hyperaccumulation, which determines the ability of some plant species to accumulate a large amount of metals in their shoots. In this review we extensively summarize and discuss the current knowledge of the main pathways for the biosynthesis of these ligands, their involvement in metal uptake, radial and long-distance transport, as well as metal influx, isolation and sequestration in plant tissues and cell compartments. It is analyzed how diverse endogenous ligand levels in plants can determine their different tolerance to metal toxic effects. This review focuses on recent advances in understanding the physiological role of these compounds in metal homeostasis, which is an essential task of modern ionomics and plant physiology. It is of key importance in studying the influence of metal deficiency or excess on various physiological processes, which is a prerequisite to the improvement of micronutrient uptake efficiency and crop productivity and to the development of a variety of applications in phytoremediation, phytomining, biofortification, and nutritional crop safety.

High-yield grass Pennisetum sinese Roxb plantation and organic manure alter bacterial and fungal communities structure in an ecological agriculture farm

Pennisetum sinese Roxb (P. sinese) is an efficient and economic energy crop for its high productivity, and has been well studied in its application in phytoremediation and fodder production. However, little is known about how P. sinese plantation and fermented manures of P. sinese-feed livestock affect the composition of soil bacterial and fungal communities. In this study, 16S rRNA/ITS1 gene-based Illumina Miseq sequencing was employed to compare the bacterial and fungal community structure among soils that had been subjected to uncultivated control (CK), 2-year P. sinese plantation (P), and P. sinese plantation combined with the use of organic manures (P-OM) in a “P. sinese—breeding industry” ecological agriculture farm. The results found microbial communities were altered by P. sinese plantation and fertilization. The P. sinese plantation resulted in increased Actinobacteria and Planctomycetes abundance. Comparatively, significant increased abundance of Chloroflexi, Firmicutes, Nitrospirae, and Euryarchaeota, and genes related with nitrogen and carbon metabolic pathways based on PICRUSt prediction was observed in P-OM soil. Fungal compositions suggested a markedly increased abundance of Ascomycota in P soil. Potential organic matter decomposers Candida, Thermoascus, and Aspergillus were enriched in P soil, indicating the enhanced role of fungi in litter decomposition. Redundancy analysis suggested that soil properties (NH4+-N, total nitrogen, organic matter content, and soil water content) significantly correlated with the changes of microbial compositions (P < 0.05). These results highlight the divergence of microbial communities occurs during P. sinese-based plantation, implying functional diversification of soil ecosystem in P. sinese fields.

Effects and interactions of cadmium and zinc on root morphology and metal translocation in two populations of Hylotelephium spectabile (Boreau) H. Ohba, a potential Cd-accumulating species.

The interactions between Cd and Zn in their effects on plants are inconsistent and difficult to predict. A hydroponic experiment was conducted to investigate the effects of Cd and Zn and their interactions on root morphology and metal translocation in two populations of Hylotelephium spectabile (Boreau) H. Ohba (Crassulaceae, HB1 and HB2). Both populations showed relative tolerance to high levels of Cd and Zn, except that the leaf biomass of HB1 significantly decreased by 44.6% with 5-mg/L Cd plus 10-mg/L Zn. Root growth was inhibited in both populations by addition of 20-mg/L Zn under Cd stress, while 10-mg/L Zn showed little impact on the root growth inhibition of HB2. Roots with diameter 0.1-0.4mm contributed most of the total root length (RL) and root surface area (RSA) of H. spectabile. In both populations, these root parameters showed greater suppression with the combined stress of Cd plus Zn than under Cd or Zn single stress, except by adding 10-mg/L Zn under Cd stress. Moreover, HB2 maintained relatively higher RL and RSA than HB1 under the different treatments, which implied that HB2 might possess a more effective mechanism than HB1 for coping in response to Cd and Zn stress. The addition of Zn not only affected the absorption of Cd but also significantly affected the distribution of Cd in different tissues of H. spectabile. A low level of Zn led to increased Cd in the stem of HB2, but an increase in Cd in the leaf and root of HB1. Addition of 10-mg/L Zn led to a significant increase by 188% and 170% in Cd accumulation in aboveground part of HB2 under 2- and 5-mg/L Cd stress, whereas the addition of Zn had little effect on Cd accumulation in HB1. Thus, strong positive interactions of Cd and Zn occurred in HB2, which showed great potential for application in phytoremediation of soil contaminated with both Cd and Zn, warranting further investigation under field condition.

Application of Phytoremediation to Reduce Environmental Pollution of Copper Smelting and Refinery Factories: a Review

Copper smelting and refinery factories are the final stages of a pyrometallurgical processing chain, and they cause many environmental challenges around the world. One of the most common environmental problems of these factories is toxic emissions. These toxic gases have harmful effects on the vegetation, animal species, soils, and water resources around the factories. Phytoremediation can play an important role in the reduction of the adverse effects of environmental pollutions arising from copper smelting and refinery factories. In this paper, we first discuss different types of pollutions caused by copper metallurgical factories, and present the main research approaches and studies conducted on these factories. In the second part, we provide a summary and comparison of different remediation technologies used to reduce the environmental pollutions of these factories. Besides, the advantages and disadvantages of each method is also investigated. In the third part, we review the different aspects of the phytoremediation including the effective mechanisms, different types of plants, application environments, and the effective factors. The next part includes the selection of suitable plants for the phytoremediation process applied for copper metallurgical factories and investigation of the native and cultivated hyperaccumulator plants. In addition, different efficiency indices are introduced for evaluating the phytoremediation efficiency and selecting an appropriate hyperaccumulator plant. At the final stage, some appropriate plant species for various types of phytoremediation are introduced. The effects of different environmental stresses and the possibilities of integrating phytoremediation with other remediation technologies as well as the advantages and disadvantages of phytoremediation are eventually investigated.

Isolation and characterization of cadmium tolerant gene SpMT2 in the hyperaccumulator Sedum plumbizincicola

Hyperaccumulators can hyper-accumulate and -tolerate heavy metals, thus are not only an ideal model to explore the mechanisms of ion transport and toxicity tolerance, but also play an irreplaceable role in the development and application of phytoremediation. Sedum plumbizincicola is a recently identified cadmium (Cd)/zinc (Zn) hyperaccumulator in the Crassulaceae family in China. Here we report the construction and screening of its yeast-expressing cDNA library. We identified a metallothionein protein encoding gene SpMT2. SpMT2 is localized in yeast cytoplasm and expression of it in yeast specifically enhanced resistance to Cd. Further analysis showed that SpMT2 did not affect Cd absorption in yeast, but greatly inhibited Cd transport into vacuoles, indicating that SpMT2 may reduce Cd toxicity via chelation in cytoplasm. qRT-PCR analyses indicated that SpMT2 was highly expressed both in roots and shoots, and did not respond to Cd treatment. Taking together the results that SpMT2 was also cytoplasm-localized in plants, we proposed that SpMT2 may chelate/detoxify Cd and retain the complex in cytosol, which renders higher mobility of Cd thus promoting long-distance Cd transport in S. plumbizincicola.

Prospect of phytoremediation combined with other approaches for remediation of heavy metal-polluted soils.

Accumulation of heavy metals in agricultural soils due to human production activities-mining, fossil fuel combustion, and application of chemical fertilizers/pesticides-results in severe environmental pollution. As the transmission of heavy metals through the food chain and their accumulation pose a serious risk to human health and safety, there has been increasing attention in the investigation of heavy metal pollution and search for effective soil remediation technologies. Here, we summarized and discussed the basic principles, strengths and weaknesses, and limitations of common standalone approaches such as those based on physics, chemistry, and biology, emphasizing their incompatibility with large-scale applications. Moreover, we explained the effects, advantages, and disadvantages of the combinations of common single repair approaches. We highlighted the latest research advances and prospects in phytoremediation-chemical, phytoremediation-microbe, and phytoremediation-genetic engineering combined with remediation approaches by changing metal availability, improving plant tolerance, promoting plant growth, improving phytoextraction and phytostabilization, etc. We then explained the improved safety and applicability of phytoremediation combined with other repair approaches compared to common standalone approaches. Finally, we established a prospective research direction of phytoremediation combined with multi-technology repair strategy.

Increasing knowledge about phytoremediation through a practical approach for undergraduate students

ABSTRACT Universities play an important role in society and in providing solutions for its problems. Environmental pollution is one of the most serious problems facing the world today. Thus, universities are increasingly including subjects related to the environment and its conservation both in their educational and research programmes. Generally, undergraduate students know many benefits of plants, such as being sources for food and several bioactive compounds, provision of atmospheric oxygen and soil conservation. However, they are less aware of the potential of plants in ‘cleaning’ environmental pollutants. To this end, a useful biochemistry laboratory approach is described that guides students to learn about the applicability of phytoremediation using in vitro plant cultures (hairy roots) to degrade an organic pollutant (phenol) from a synthetic solution. This laboratory approach has been successfully implemented in university Plant Biotechnology courses to deepen understanding about phytoremediation potential and highlight the biochemical basis of this process. This procedure can be easily adopted to increase student learning of environmental issues, and awareness about the potential of using plants for environmental remediation processes.

Application of Floating Aquatic Plants in Phytoremediation of Heavy Metals Polluted Water: A Review

Heavy-metal (HM) pollution is considered a leading source of environmental contamination. Heavy-metal pollution in ground water poses a serious threat to human health and the aquatic ecosystem. Conventional treatment technologies to remove the pollutants from wastewater are usually costly, time-consuming, environmentally destructive, and mostly inefficient. Phytoremediation is a cost-effective green emerging technology with long-lasting applicability. The selection of plant species is the most significant aspect for successful phytoremediation. Aquatic plants hold steep efficiency for the removal of organic and inorganic pollutants. Water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes) and Duck weed (Lemna minor) along with some other aquatic plants are prominent metal accumulator plants for the remediation of heavy-metal polluted water. The phytoremediation potential of the aquatic plant can be further enhanced by the application of innovative approaches in phytoremediation. A summarizing review regarding the use of aquatic plants in phytoremediation is gathered in order to present the broad applicability of phytoremediation.

Characteristics of endophytic bacteria from Polygonum hydropiper and their use in enhancing P-phytoextraction

Endophytes are significant for their ecological role in plants and potential applications in phytoremediation. Endophytic bacteria with plant-growth-promoting (PGP) characteristics are isolated as inoculants to enhance phytoremediation efficiency; however, few attempts have been made to isolate bacteria from phosphorus (P)-accumulating plants and study their roles in P-phytoextraction. Endophytic bacteria of P-accumulating herb Polygonum hydropiper were isolated and identified. The PGP traits including indole-3-acetic acid (IAA), siderophores, phosphate-solubilization etc. were characterized. Some endophytes were selected as the inoculants for a pot experiment in high P soil to investigate their role in P-phytoextraction. Thirty-five isolates were tolerant of high P and classified into 10 taxonomic groups. The production of indole-3-acetic acid into IAA acid and siderophores was dependent on strain species. Tricalcium phosphate (TCP)-solubilizing activity of these strains was associated with a decrease of pH but increases of organic acids production, while phytin-solubilizing activity was associated with a decrease of pH but increases of acid and alkaline phosphatase activities. In the six inoculants, five strains promoted stem and leaf growth of Polygonum hydropiper except for SLs08. P. hydropiper with inoculation of SLr02, SLr15, SLs13 and SLs18 showed significantly higher root length and surface area than the control plants. The inoculation with SLr15, SLs13 and SLs18 significantly enhanced stem and leaf P accumulation of P. hydropiper. Endophytic bacteria with PGP traits exist in Polygonum hydropiper and strains SLr15, SLs13 and SLs18 greatly promoted plant growth and shoot P accumulation, offering the most potential as PGP inoculants for assisting P. hydropiper in P-phytoextraction.

Root exudates-driven rhizosphere recruitment of the plant growth-promoting rhizobacterium Bacillus flexus KLBMP 4941 and its growth-promoting effect on the coastal halophyte Limonium sinense under salt stress.

Halophytes play an important role in the bioremediation of saline soils. Increased evidence has revealed that plant growth-promoting rhizobacteria (PGPR) have colonized the halophytic rhizosphere, and they have evolved the capacity to reduce salt stress damage to the host. However, the mechanism by which halophytes attract and recruit beneficial PGPR has rarely been reported. This study reports the interaction between the halophyte Limonium sinense and its rhizosphere PGPR strain Bacillus flexus KLBMP 4941, as well as the mechanism by which KLBMP 4941 promotes host plant growth under salt stress. After salt stress treatment, we collected the root exudates (REs) of L. sinense and found that the REs could promote the growth and chemotaxis of the bacterium KLBMP 4941. In addition, the components of the REs under salt stress were analyzed, and some organic acids (2-methylbutyric acid, stearic acid, palmitic acid, palmitoleic acid, and oleic acid) were detected as the major components. Further assessment showed that each of these components had positive effects on the growth, motility, chemotaxis, and root colonization of strain KLBMP 4941. Further pot experiments revealed the potential PGP mechanisms induced by strain KLBMP 4941 on the host plant under salt stress. Inoculation with KLBMP 4941 promoted the accumulation of chlorophyll to enhance photosynthesis, increased osmotic regulator contents, enhanced flavonoid and antioxidant enzymes, and regulated Na+/K+ homeostasis to help the host ameliorate salinity stress damage. Our findings indicate that the halophyte L. sinense can attract and recruit beneficial rhizosphere bacteria by REs under salt stress, and the recruited B. flexus KLBMP 4941 elicited PGP effects under salinity stress through complex plant physiological regulatory mechanisms. This study provides a foundation for the enhancement of the rhizosphere colonization ability of the PGP strain KLBMP 4941, which shows potential applications in phytoremediation of saline soils.

Significance of soil microbe in microbial-assisted phytoremediation: an effective way to enhance phytoremediation of contaminated soil

Soil contamination is an increasing global problem. Efforts are underway to minimize the release of contaminants and develop effective bioremediation strategies. Contaminated soil can be treated by phytoremediation that is dependent on the contaminant and soil properties and plant growth rate. In recent decades, soil microbes have been used successfully to enhance the capacity of plants to tolerate, remove and/or degrade contaminants. This paper reviews the principles and applications of microbe-assisted phytoremediation, including the factors that influence phytoremediation, and the mechanisms of microbial remediation. Inoculation with specific contaminant-degrading bacteria and plant growth-promoting rhizobacteria is effective in enhancing phytoremediation. However, in the context of serious and complicated cases of environmental pollution exacerbated by climate change, it is critical to increase the knowledge about the mechanisms of microbe-assisted phytoremediation to underpin the selection of most appropriate phytoremediation approaches.

Efficacy of a Plant-Microbe System: Pisum sativum (L.) Cadmium-Tolerant Mutant and Rhizobium leguminosarum Strains, Expressing Pea Metallothionein Genes PsMT1 and PsMT2, for Cadmium Phytoremediation.

Two transgenic strains of Rhizobium leguminosarum bv. viciae, 3841-PsMT1 and 3841-PsMT2, were obtained. These strains contain the genetic constructions nifH-PsMT1 and nifH-PsMT2 coding for two pea (Pisum sativum L.) metallothionein genes, PsMT1 and PsMT2, fused with the promoter region of the nifH gene. The ability of both transgenic strains to form nodules on roots of the pea wild-type SGE and the mutant SGECdt, which is characterized by increased tolerance to and accumulation of cadmium (Cd) in plants, was analyzed. Without Cd treatment, the wild type and mutant SGECdt inoculated with R. leguminosarum strains 3841, 3841-PsMT1, or 3841-PsMT2 were similar histologically and in their ultrastructural organization of nodules. Nodules of wild-type SGE inoculated with strain 3841 and exposed to 0.5 μM CdCl2 were characterized by an enlarged senescence zone. It was in stark contrast to Cd-treated nodules of the mutant SGECdt that maintained their proper organization. Cadmium treatment of either wild-type SGE or mutant SGECdt did not cause significant alterations in histological organization of nodules formed by strains 3841-PsMT1 and 3841-PsMT2. Although some abnormalities were observed at the ultrastructural level, they were less pronounced in the nodules of strain 3841-PsMT1 than in those formed by 3841-PsMT2. Both transgenic strains also differed in their effects on pea plant growth and the Cd and nutrient contents in shoots. In our opinion, combination of Cd-tolerant mutant SGECdt and the strains 3841-PsMT1 or 3841-PsMT2 may be used as an original model for study of Cd tolerance mechanisms in legume-rhizobial symbiosis and possibilities for its application in phytoremediation or phytostabilization technologies.

Leaching Potential of Multi-metal-Contaminated Soil in Chelate-Aided Remediation

Chelates, used to increase the uptake of heavy metals in phytoremediation, can also increase the mobility of metals. If plants fail to uptake or stabilize all the mobilized metals, then subsurface soil or groundwater can be contaminated. Therefore, the type and concentration of chelate used and proper site management are important for chelate-aided phytoremediation. In this study, we evaluated potential metal leaching from the soil after applying three different chelates. The readily soluble and exchangeable metal (RSEM) and plant-available metal (PAM) of Pb, Zn, Cu, Cd, and Ni in soil amended with ethylene diamine tetra acetic acid (EDTA), ethylene diamine disuccinate (EDDS), or humic acid (HA) were analyzed, and the potential leaching factor (PLF) of the heavy metals was estimated. Results showed that the effects of chelates and their concentration on RSEM and PAM of heavy metal in soil were different. The addition of EDTA increased the CRSEM and CPAM of all heavy metals, although its effects varied with the concentration added. EDDS application increased CRSEM and CPAM of Cu, Ni, and Zn, but EDDS was more effective than EDTA for Cu and Ni. HA did not show a significant impact due to the short duration of the experiment. In most cases with chelates effects, the increase of RSEM was greater than PAM, and the potential of metal leaching increased. Therefore, application of chelates for remediation of metal-contaminated soil should consider not only the capacity of metal uptake in plants but also the potential metal leaching from the system. Additionally, this process should be accompanied by proper water management to minimize leachate in chelate-aided phytoremediation applications.

Bacopa monnieri (L.) Pennell, a potential plant species for degradation of textile azo dyes.

The current study highlighted the phytoremediation potential of Bacopa monnieri (L.) Pennell for most commonly used azo dyes which are resistant to degradation. Fourteen azo dyes (reactive: 09; direct: 05) upon treatments up to 40mg/L were decolorized in the range of 90 to 100% after incubation of 2weeks in in vitro and hydroponic cultures. No significant alteration in growth of B. monnieri was observed in the presence of dyes R. Magenta MB, R. Navy Blue M2R, Dt. Orange RS, Dt. T Blue GLL, Dt. Sky Blue FF alone, and together in the medium. However, at increasing concentrations (60-100mg/L), the percent dye decolorization was declined and showed a toxic effect on plant growth. The chlorophyll content declined while membrane damage and osmolyte accumulation were increased in dye treated samples. The biological conversion of produced metabolites was analyzed using FTIR and GC-MS. Our results suggest that the intermediates of Dt. Blue GLL degradation consist L-Proline, N-valeryldecyl ester, 3,5 Di-tert-butyl-4-trimethylsiloxytoulene, and 1,2-benzenedicarboxylic acid, diisooctyl ester. The antioxidative and oxidative enzyme activities in roots and leaves were significantly higher in the presence of dyes over control indicate that these enzymes are involved in degradation of dyes. Percentage seed germination, shoot and root length of seedlings of legume, cereal, and oilseed crop was not affected, suggesting the compatible nature of the produced metabolites. Our results revealed the remarkable ability of Bacopa monnieri for long-term operations that lead to the practical application of phytoremediation in textile industries.