Phytoextraction capacity of the plants growing on tannery sludge dumping sites

The study was undertaken to assess the phytoremediation potential of four plants (Sida acuta, Ricinus communis, Calotropis procera, Cassia fistula) growing at a tannery sludge disposal site. Results showed that maximum amount of K, Fe and Ni was associated with residual fraction, whereas, Zn, Mn, Cr, Pb, Cd and Co was found in Fe-Mn oxide fraction. Cu and Na were mostly associated with organic matter and carbonate fraction, respectively. The results demonstrated that the levels of accumulation of metals was found high in all the studied plants and followed the order; C. procera>S. acuta>R. communis=C. fistula. The principal components analysis (PCA) revealed that translocation behavior of Cu, Zn and Mn, Cr were found similar in the plants. Correlation analysis between metal accumulation in the plants with DTPA extractable metals emphasized that S. acuta and C. fistula provide better value of correlation for most of the tested metals. The values of transfer factor were also found high for most of the tested metals in the plants of S. acuta. Overall, the plants of S. acuta and C. fistula were found suitable for the decontamination of most of the metals from tannery waste contaminated sites.     

Phytoextraction of metals and metalloids from contaminated soils

The removal of inorganic contaminants by plants is termed phytoextraction. Recent studies have looked at the feasibility of phytoextraction, and demonstrate that both good biomass yields and metal hyperaccumulation are required to make the process efficient. Adding chelating agents to soil to increase the bioavailability of contaminants can sometimes induce hyperaccumulation in normal plants, but may produce undesirable environmental risks. Thus, it is necessary to investigate the mechanisms responsible for hyperaccumulation, using natural hyperaccumulators as model plant species. Recent advances have been made in understanding the mechanisms responsible for hyperaccumulation of Zn, Cd, Ni and As by plants. Attempts to engineer metal tolerance and accumulation have so far been limited to Hg, As and Cd, and although promising results have been obtained they may be some way from practical application. More fundamental understanding of the traits and mechanisms involved in hyperaccumulation are needed so that phytoextraction can be optimised.     

Phytoextraction capacity of trees growing on a metal contaminated soil

Phytoremediation is an innovative biological technique to reclaim land contaminated by heavy metals or organic pollutants. In the present work, we studied the ability of five woody species to extract heavy metal (copper, zinc or cadmium) from a polluted soil to their above-ground tissues. Metal content in leaves and twigs was determined. Salix and Betula transferred zinc and cadmium to leaves and twigs, but Alnus, Fraxinus and Sorbus excluded them from their above-ground tissues. None of the species considered transferred copper to the shoots.     

Phytostabilization potential of ornamental plants grown in soil contaminated with cadmium

In a greenhouse experiment, five ornamental plants, Osmanthus fragrans (OF), Ligustrum vicaryi L. (LV), Cinnamomum camphora (CC), Loropetalum chinense var. rubrum (LC), and Euonymus japonicas cv. Aureo-mar (EJ), were studied for the ability to phytostabilization for Cd-contaminated soil. The results showed that these five ornamental plants can grow normally when the soil Cd content is less than 24.6 mg·kg^?1. Cd was mainly deposited in the roots of OF, LV, LC and EJ which have grown in Cd-contaminated soils, and the maximum Cd contents reached 15.76, 19.09, 20.59 and 32.91 mg·kg^?1, respectively. For CC, Cd was mainly distributed in the shoots and the maximum Cd content in stems and leaves were 12.5 and 10.71 mg·kg^?1, however, the total amount of Cd in stems and leaves was similar with the other ornamental plants. The enzymatic activities in Cd-contaminated soil were benefited from the five tested ornamental plants remediation. Soil urease and sucrase activities were improved, while dehydrogenase activity was depressed. Meanwhile, the soil microbial community was slightly influenced when soil Cd content is less than 24.6 mg·kg^?1 under five ornamental plants remediation. The results further suggested that ornamental plants could be promising candidates for phytostabilization of Cd-contaminated soil.     

Phytoextraction of heavy metals by Sesuvium portulacastrum l. a salt marsh halophyte from tannery effluent

The present study investigated the sources for remediation of heavy metals and salts from tannery effluent using salt marsh halophyte Sesuvium portulacastrum. From the results observed, in tannery effluent treated soil from 1 kg dry weight of plant sample, Sesuvium portulacastrum accumulated 49.82 mg Cr, 22.10 mg Cd, 35.10 mg Cu and 70.10 mg Zn and from 1 g dry weight of the plant sample, 246.21 mg Na Cl. Cultivation of Sesuvium portulacastrum significantly reduced the EC, pH and SAR levels in tannery effluent and salt treated soil and correspondingly increased in plant sample after 125 days of cultivation. In conclusion, Sesuvium portulacastrum was an efficient in accumulating heavy metals such as Chromium, Cadmium, Copper and Zinc, sodium and chloride maximum through its leaves when compared to stem and root. The finding of these bioacccumulation studies indicates that Sesuvium portulacastrum could be used for phytoremediation of tannery effluent contaminated field.     

Phytoextraction of Pb and Cu contaminated soil with maize and microencapsulated EDTA

Chelate-assisted phytoextraction using agricultural crops has been widely investigated as a remediation technique for soils contaminated with low mobility potentially toxic elements. Here, we report the use of a controlled-release microencapsulated EDTA (Cap-EDTA) by emulsion solvent evaporation to phytoremediate soil contaminated with Pb and Cu. Incubation experiments were carried out to assess the effect of Cap- and non-microencapsulated EDTA (Ncap-EDTA) on the mobility of soil metals. Results showed EDTA effectively increased the mobility of Pb and Cu in the soil solution and Cap-EDTA application provided lower and more constant water-soluble concentrations of Pb and Cu in comparison with. Phytotoxicity may be alleviated and plant uptake of Pb and Cu may be increased after the incorporation of Cap-EDTA. In addition phytoextraction efficiencies of maize after Cap- and Ncap-EDTA application were tested in a pot experiment. Maize shoot concentrations of Pb and Cu were lower with Cap-EDTA application than with Ncap-EDTA. However, shoot dry weight was significantly higher with Cap-EDTA application. Consequently, the Pb and Cu phytoextraction potential of maize significantly increased with Cap-EDTA application compared with the control and Ncap-EDTA application.     

Germination strategies of halophyte seeds under salinity

Halophytes are plants of saline habitats that grow under conditions that may vary in extremes of temperatures (freezing to very hot), water availability (drought to water logging) and salinity (mild to almost saturation). Halophytes may also face sudden micro-environmental variations within their habitats. In this review we examine some of the factors that determine the ability of seeds of halophytes to germinate when conditions are optimal for seedling growth and survival.Seed dormancy (innate, induced or acquired) is an important means of initiating growth under appropriate conditions. Saline environments are often wet and so the seeds of halophytes may remain un-germinated over extended periods even after imbibition if the external environment does not favour germination and seedling survival. Many perennial halophytes, however, do not possess elaborate dormancy systems because they propagate largely through ramets and have no ecological compulsions for seed germination.The seeds of halophytes also have the capacity to recover from a salinity shock and start germination once salinity is reduced, which may happen following rain. In some cases, imbibition in a low-salt solution may help in osmo-priming and improve germination. Seed heteromorphism is yet another strategy adopted by some halophytes, whereby seeds of different size and colour are produced that germinate consecutively at suitable intervals. Light-dependent germination may also help if the seed is under a dense canopy or buried in debris; germination only occurs once these restraints are removed thus increasing the chances of seedling survival.     

Phytoextraction of trace elements by water hyacinth in contaminated area of gold mine tailing

The ability of water hyacinth (Eichhornia crassipes) to uptake Ag, Ba, Cd, Mo, and Pb from waters in gold mine tailing area was studied. All experiments were carried out in the field conditions without using of model system. Bioconcentration (BCF) and translocation factors (TF) as well as elements accumulation by plant in different points of tailings-impacted area were evaluated. It has been shown that water hyacinth demonstrates high ability to accumulate Mo, Pb, and Ba with BCF values 24,360 ± 3600, 18,800 ± 2800 and 10,040 ± 1400, respectively and is efficient in translocation of Mo and Cd. The general trend of the plant accumulation ability in relation to the studied elements corresponds to their concentration in the medium. As the distance from tailings increases, concentration of Ag, Ba and Pb in plant decreases more clearly than that of Cd, while the amount of Mo accumulated by plant doesn't drop significantly in accordance with its concentration in water. Under the conditions of the confluence of river Ur and drainage stream Ba and Ag can be considered as potential candidates for phytomining.     

Water potential in soil and Atriplex nummularia (phytoremediator halophyte) under drought and salt stresses

Atriplex nummularia is a halophyte widely employed to recover saline soils and was used as a model to evaluate the water potentials in the soil-plant system under drought and salt stresses. Potted plants grown under 70 and 37% of field capacity irrigated with solutions of NaCl and of a mixture of NaCl, KCl, MgCl₂ and CaCl₂ reproducing six electrical conductivity (EC): 0, 5, 10, 20, 30, and 40 dS m^?1. After 100 days, total water (Ψ_{w, plant}) and osmotic (Ψ_{o, plant}) potentials at predawn and midday and Ψ_{o, soil}, matric potential (Ψ_{m, soil}) and Ψ_{w, soil} were determined. The type of ion in the irrigation water did not influence the soil potential, but was altered by EC. The soil Ψ_o component was the largest contributor to Ψ_{w, soil}. Atriplex is surviving ECs close to 40 dS m^?1 due to the decrease in the Ψ_w. The plants reached a Ψ_w of approximately ?8 MPa. The water potentials determined for different moisture levels, EC levels and salt types showed huge importance for the management of this species in semiarid regions and can be used to recover salt affected soils.     

Assessment of photosynthetic potential of indoor plants under cold stress

Photosynthetic parameters including net photosynthetic rate (P_N), transpiration rate (E), water-use efficiency (WUE), and stomatal conductance (g_s) were studied in indoor C₃ plants Philodendron domesticum (Pd), Dracaena fragans (Df), Peperomia obtussifolia (Po), Chlorophytum comosum (Cc), and in a CAM plant, Sansevieria trifasciata (St), exposed to various low temperatures (0, 5, 10, 15, 20, and 25°C). All studied plants survived up to 0°C, but only St and Cc endured, while other plants wilted, when the temperature increased back to room temperature (25°C). The P_N declined rapidly with the decrease of temperature in all studied plants. St showed the maximum P_N of 11.9 μmol m^?2 s^?1 at 25°C followed by Cc, Po, Pd, and Df. E also followed a trend almost similar to that of P_N. St showed minimum E (0.1 mmol m^?2 s^?1) as compared to other studied C₃ plants at 25°C. The E decreased up to ≈4-fold at 5 and 0°C. Furthermore, a considerable decline in WUE was observed under cold stress in all C₃ plants, while St showed maximum WUE. Similarly, the g_s also declined gradually with the decrease in the temperature in all plants. Among C₃ plants, Pd and Po showed the maximum g_s of 0.07 mol m^?2 s^?1 at 25°C followed by Df and Cc. However, St showed the minimum g_s that further decreased up to ～4-fold at 0°C. In addition, the content of photosynthetic pigments [chlorophyll a, b, (a+b), and carotenoids] was varying in all studied plants at 0°C. Our findings clearly indicated the best photosynthetic potential of St compared to other studied plants. This species might be recommended for improving air quality in high-altitude closed environments.     

Life cycle assessment of contaminated sites remediation

For the federal state of Baden-Wiirttemberg, Germany, the decision tool “Umweltbilanz von Altlastensanierungsverfahren” has been developed and found suitable for the quantification and evaluation of environmental impacts caused by remediation of contaminated sites. The developed tool complements the remediation toolbox of Baden-Wiirttemberg. The tool includes a streamlined life cycle assessment (LCA) and a synopsis of the LCA results with the results of a risk assessment of the contaminated site. The risk assessment tool is not explained here. The data base for the life cycle inventory includes several techniques used in remedial actions. The life cycle impact assessment utilises 14 impact categories. The method allows comparisons between remedial options for specific contaminated sites. A software tool has been developed to be available in 1999.     

Phytoextraction potential of the nickel hyperaccumulators Leptoplax emarginata and Bornmuellera tymphaea

Leptoplax emarginata and Bornmuellera tymphaea are nickel hyperaccumulators of the Brassicaceae family endemic to serpentine soils in Greece. The aims of this work were to compare the growth and uptake behavior of these plants with the Ni hyperaccumulator species Thlaspi caerulescens and Alyssum murale, and to evaluate their effect on soil Ni availability. Plants were grown for 3 mo on three soils that differ in Ni availability. Ni availability in soils was measuredby isotopic exchange kinetics and DTPA-TEA extractions. Results showed that L. emarginata produced significantly more biomass than other plants. On the serpentine soil, B. tymphaea showed the highest Ni concentration in shoots. However, Niphytoextraction on the three soils was maximal with L. emarginata. The high initial Ni availability of soil Serp (470.5 mg kg(-1)) was the main explanation for the high Ni concentrations measured in plant shoots grown on this soil, compared to those grown on soils Calc and Silt A. murale was the least efficient in reducing Ni availability on the serpentine soil L. emarginata appeared as the most efficient species for Ni phytoextraction and decrease of the Ni available pool.     

Aspects of phytoremediation for chromium contaminated sites using common plants Urtica dioica, Brassica napus and Zea mays

As chromium is widely used in many industries of which leather industries are the biggest consumers, wastes from tanneries pose a serious threat to the environment. Present research conducted greenhouse pot experiments on several plants using different solutions to find out their phytoextraction potential. Among the plants, Urtica dioica found to be very effective due to its higher uptake capacity for chromium. The analyses showed that with 500 mg/l solutions Cr concentration in roots was 38.9% higher (average 20 mg/kg) than plants fed with 200 mg/l solutions (phytostabilisation), while with 200 mg/l solutions more Cr was transported to leaves (phytoextraction), 10.52% higher (average 9.5 mg/kg) concentration than plants fed with 500 mg/l solutions, but also means that plants were less affected by toxicity. Zea mays showed high tolerance towards Cr with negligible concentration in leaves. Although average Cr concentration in Brassica napus is lower (25% and 21% for 200 mg/l and 500 mg/l solutions respectively) than Urtica dioica which still could account for phytoextraction, but due to its high vulnerability to insects its potentiality has downgraded. Among other elements, K being a component of the salt, played significant role for plants growth and survival—opening new avenue for phytoremediation of contaminated sites.     

Microbial indication of soils contaminated with industrial emissions

Changes in the composition of microbial complexes and their biochemical activity in soil in the vicinity of a strong source of HF emission have been studied. A sharp decrease of the biomass, the number of asporous bacteria and actinomycetes, and a smaller decrease of the number of microscopic fungi has been revealed, along with a decrease in the enzymatic and respiratory activity of contaminated soil with the relative increase in the fraction of sporiferous bacteria. On the basis of the response of introduced population of Bacillus subtilis to different doses of HF, NaF, Na₂SO₃ microbiological norm-fixing for technogenic soil ecosystems has been carried out.     

Biodiversity and antimicrobial potential of bacterial endophytes from halophyte Salicornia brachiata

Extreme natural habitats like halophytes, marsh land, and marine environment are suitable arena for chemical ecology between plants and microbes having environmental impact. Endophytes are an ecofriendly option for the promotion of plant growth and to serve as sustainable resource of novel bioactive natural products. The present study, focusing on biodiversity of bacterial endophytes from Salicornia brachiata, led to isolation of around 336 bacterial endophytes. Phylogenetic analysis of 63 endophytes revealed 13 genera with 27 different species, belonging to 3 major groups: Firmicutes, Proteobacteria, and Actinobacteria. 30% endophytic isolates belonging to various genera demonstrated broad-spectrum antibacterial and antifungal activities against a panel of human, plant, and aquatic infectious agents. An endophytic isolate Bacillus amyloliquefaciens 5NPA-1, exhibited strong in-vitro antibacterial activity against human pathogen Staphylococcus aureus and phytopathogen Xanthomonas campestris. Investigation through LC–MS/MS-based molecular networking and bioactivity-guided purification led to the identification of three bioactive compounds belonging to lipopeptide class based on ¹H-, ¹³C-NMR and MS analysis. To our knowledge, this is the first report studying bacterial endophytic biodiversity of Salicornia brachiata and the isolation of bioactive compounds from its endophyte. Overall, the present study provides insights into the diversity of endophytes associated with the plants from the extreme environment as a rich source of metabolites with remarkable agricultural applications and therapeutic properties.

     

Phytoremediative potential of salt-tolerant grass species for cadmium and lead under contaminated nutrient solution

Abstract

Phytoremediation of heavy metal contaminated soils represents a promising technique and salt-tolerant hyperaccumulators for multiple metals are the need of time. Therefore, phytoremediation potential of four salt-tolerant grass species [Dhab (Desmostachya bipinnata), Kallar (Leptochloa fusca), Para (Brachiaria mutica) and Sporobolus (Sporobolus arabicus Boiss)] was evaluated for cadmium (Cd) and lead (Pb) in a hydroponic study. The plants were harvested after a growth period of 3 months in a nutrient solution containing different levels of Cd (0, 5, and 25?mg?L^?1) and Pb (0, 25, and 125?mg L^?1). Results indicated that Dhab grass showed the highest root and shoot dry matter yield followed by Para, Kallar and Sporobolus grass irrespective of metal or its level under which they were grown. All the grass species showed considerable Cd-accumulating potential with an accumulation of >150?mg kg^?1of shoot dry matter at a higher level of Cd-contamination (25?mg?L^?1). While in case of shoot Pb-accumulation only Para grass performed well and accumulated Pb >1000?mg kg^?1 of shoot dry matter at the higher level of Pb-contamination (125?mg?L^?1). Moreover, Para and Dhab grasses performed better for shoot Cd-uptake, while only Para grass showed promising shoot Pb uptake potential. In conclusion, these grass species could be penitentially used for phytoremediation of salt-affected Cd and Pb contaminated soils.     

Arsenic accumulation of common plants from contaminated soils

A pot experiment was conducted to investigate the relationship between soluble concentrations of arsenic (As) in soil and its accumulation by maize (Zea mays), English ryegrass (Lolium perenne), rape (Brassica napus) and sunflower (Helianthus annuus) on two different soils: a calcareous Regosol (silty loam) and a non-calcareous Regosol (sandy loam). Arsenic (Na₂HAsO₄·7H₂O) was applied to obtain comparable soluble As concentrations in the two soils. In both soils, soluble As concentrations, extracted with 0.1 M NaNO₃, were found to correlate better with As concentrations in plants after 4 month of growth than total soil concentrations, extracted with 2 M HNO₃. With all four plant species, the relationship between the soluble As concentration in the soil and As that in the plants was non- linear, following Michaelis-Menten kinetics. Similar soluble As concentrations in the two soils did not result in a similar As concentration in the plants. Except for maize, arsenic transport from roots to shoots was significant, resulting in As concentrations in the leaves and grains above the Swiss tolerance limits for fodder and food crops (4 and 0.2 mg As kg^–1, respectively). Based on these results we suggest that beside As solubility, P availability and P demand, which are plant specific, have to be taken into account to predict the uptake of As by crop plants from As contaminated soils and to predict the risk of arsenic entering into the food chain.     

Phytoremediation of heavy metal contaminated soil potential by woody plants on Tonglushan ancient copper spoil heap in China

Fast-growing metal-accumulating woody plants are considered potential candidates for phytoremediation of metals. Tonglushan mining, one of the biggest Cu production bases in China, presents an important source of the pollution of environment. The sample was collected at Tonglushan ancient copper spoil heap. The aims were to measure the content of heavy metal in the soil and woody plants and to elucidate the phytoremediation potential of the plants. The result showed that soil Cu, Cd and Pb were the main contamination, the mean contents of which were 3166.73 mg/kg, 3.66 mg/kg and 137.06 mg/kg respectively, which belonged to severe contamination. Fourteen species from 14 genera of 13 families were collected and investigated; except for Ligutrum lucidum, the other 13 woody plants species were newly recorded in this area. In addition, to assess the ability of metal accumulation of these trees, we proposed accumulation index. Data suggested that Platanus × acerilolia, Broussonetia papyrifera, Ligutrum lucidum, Viburnum awabuki, Firmiana simplex, Robina pseudoacacia, Melia azedarach and Osmanthus fragrans exhibited high accumulated capacity and strong tolerance to heavy metals. Therefore, Platanus × acerilolia and Broussonetia papyrifera can be planted in Pb contaminated areas; Viburnum awabuki, Firmiana simplex, Robina pseudoacacia and Melia azedarach are the suitable trees for Cd contaminated areas; Viburnum awabuki, Melia azedarach, Ligutrum lucidum, Firmiana simplex, Osmanthus fragrans and Robina pseudoacacia are appropriate to Cu, Pb and Cd multi-metal contaminated areas.     

Phytoremediation potential of some agricultural plants on heavy metal contaminated mine waste soils,salem district,tamilnadu

The Pot culture experiment performed for phytoextraction potential of selected agricultural plants [millet (Eleusine coracana), mustard (Brassica juncea), jowar (Sorghum bicolor), black gram (Vigna mungo), pumpkin (Telfairia occidentalis)] grown in metal contaminated soils around the Salem region, Tamilnadu, India. Physiochemical characterization of soils, reported as low to medium level of N, P, K was found in test soils. The Cr content higher in mine soils than control and the values are 0.176 mg/L in Dalmia soil and 0.049 mg/L in Burn &; Co soil. The germination rate low in mine soil than control soils (25 to 85%). The content of chlorophyll, carotenoid, carbohydrate and protein decreased in mine soils than control. The morphological parameters and biomass values decreased in experimental plants due to metal accumulation. Proline content increased in test plants and ranged from 0.113 mg g^?1 to 0.858 mg g^?1 which indicate the stress condition due to toxicity of metals. Sorghum and black gram plants reported as metal tolerant capacity. Among the plants, Sorghum produced good results (both biomass and biochemical parameters) which equal to control plant and suggests Sorghum plant is an ideal for remediation of metal contaminated soils.