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1.
A pot experiment was conducted to study the performance of EDTA and citric acid (CA) addition in improving phytoextraction of Cd, Cu, Pb, and Cr from artificially contaminated soil by T. angustifolia. T. angustifolia showed the remarkable resistance to heavy metal toxicity with no visual toxic symptom including chlorosis and necrosis when exposed to metal stress. EDTA-addition significantly reduced plant height and biomass, compared with the control, and stunted plant growth, while 2.5 and 5 mM CA addition induced significant increases in root dry weight. EDTA, and 5 and 10 mM CA significantly increased shoot Cd, Pb, and Cr concentrations compared with the control, with EDTA being more effective. At final harvest, the highest shoot Cd, Cr, and Pb concentrations were recorded in the treatment of 5 mM EDTA addition, while maximal root Pb concentration was found at the 2.5 mM CA treatment. However, shoot Cd accumulation in the 10 mM CA treatment was 36.9% higher than that in 2.5 mM EDTA, and similar with that in 10 mM EDTA. Shoot Pb accumulation was lower in 10 mM CA than that in EDTA treatments. Further, root Cd, Cu, and Pb accumulation of CA treatments and shoot Cr accumulation in 5 or 10 mM CA treatments were markedly higher than that of control and EDTA treatments. The results also showed that EDTA dramatically increased the dissolution of Cu, Cr, Pb, and Cd in soil, while CA addition had less effect on water-soluble Cu, Cr, and Cd, and no effect on Pb levels. It is suggested that CA can be a good chelator candidate for T. angustifolia used for environmentally safe phytoextraction of Cd and Cr in soils.  相似文献   

2.
Enhanced phytoextraction using EDTA for the remediation of an agricultural soil contaminated with less mobile risk elements Cd and Pb originating from smelting activities in Príbram (Czech Republic) was assessed on the laboratory and the field scale. EDTA was applied to the first years crop Zea mays. Metal mobilization and metal uptake by the plants in the soil were monitored for two additional years when Triticum aestivum was planted. The application ofEDTA effectively increased water-soluble Cd and Pb concentrations in the soil. These concentrations decreased over time. Anyhow, increased concentrations could be still observed in the third experimental year indicating a low possibility of groundwater pollution after the addition of EDTA during and also after the enhanced phytoextraction process under prevailing climatic conditions. EDTA-applications caused phytotoxicity and thereby decreased biomass production and increased Cd and Pb uptake by the plants. Phytoextraction efficiency and phytoextraction potential were too low for Cd and Pb phytoextraction in the field in a reasonable time frame (as less than one-tenth of a percent of total Cd and Pb could be removed). This strongly indicates that EDTA-enhanced phytoextraction as implemented in this study is not a suitable remediation technique for risk metal contaminated soils.  相似文献   

3.
Phytoextraction has received increasing attention as a promising, cost-effective alternative to conventional engineering-based remediation methods for metal contaminated soils. In order to enhance the phytoremediative ability of green plants chelating agents are commonly used. Our study aims to evaluate whether, citric acid (CA) or elemental sulfur (S) should be used as an alternative to the ethylene diamine tetraacetic acid (EDTA)for chemically enhanced phytoextraction. Results showed that EDTA was more efficient than CA and S in solubilizing lead (Pb) from the soil. The application of EDTA and S increased the shoot biomass of wheat. However, application of CA at higher rates (30 mmol kg(-1)) resulted in significantly lower wheat biomass. Photosynthesis and transpiration rates increased with EDTA and S application, whereas these parameters were decreased with the application of CA. Elemental sulfur was ineffective for enhancing the concentration of Pb in wheat shoots. Although CA did not increase the Pb solubility measured at the end of experiment, however, it was more effective than EDTA in enhancing the concentration of Pb in the shoots of Triticum aestivum L. It was assumed that increase in Mn concentration to toxic levels in soil with CA addition might have resulted in unusual Pb concentration in wheat plants. The results of the present study suggest that under the conditions used in this experiment, CA at the highest dose was the best amendment for enhanced phytoextraction of Pb using wheat compared to either EDTA or S.  相似文献   

4.
High biomass producing plant species, such as Helianthus annuus, have potential for removing large amounts of trace metals by harvesting the aboveground biomass if sufficient metal concentrations in their biomass can be achieved However, the low bioavailability of heavy metals in soils and the limited translocation of heavy metals to the shoots by most high biomass producing plant species limit the efficiency of the phytoextraction process. Amendment of a contaminated soil with ethylene diamine tetraacetic acid (EDTA) or citric acid increases soluble heavy metal concentrations, potentially rendering them more available for plant uptake. This article discusses the effects of EDTA and citric acid on the uptake of heavy metals and translocation to aboveground harvestable plant parts in Helianthus annuus. EDTA was included in the research for comparison purposes in our quest for less persistent alternatives, suitable for enhanced phytoextraction. Plants were grown in a calcareous soil moderately contaminated with Cu, Pb, Zn, and Cd and treated with increasing concentrations of EDTA (0.1, 1, 3, 5, 7, and 10 mmol kg(-1) soil) or citric acid (0.01, 0.05, 0.25, 0.442, and 0.5 mol kg(-1) soil). Heavy metal concentrations in harvested shoots increased with EDTA concentration but the actual amount of phytoextracted heavy metals decreased at high EDTA concentrations, due to severe growth depression. Helianthus annuus suffered heavy metal stress due to the significantly increased bioavailable metal fraction in the soil. The rapid mineralization of citric acid and the high buffering capacity of the soil made citric acid inefficient in increasing the phytoextracted amounts of heavy metals. Treatments that did not exceed the buffering capacity of the soil (< 0.442 mol kg(-1) soil) did not result in any significant increase in shoot heavy metal concentrations. Treatments with high concentrations resulted in a dissolution of the carbonates and compaction of the soil. These physicochemical changes caused growth depression of Helianthus annuus. EDTA and citric acid added before sowing of Helianthus annuus did not appear to be efficient amendments when phytoextraction of heavy metals from calcareous soils is considered.  相似文献   

5.
A pot experiment was conducted to investigate the uptake of Zn from experimentally contaminated calcareous soil of low nutrient status by maize inoculated with the arbuscular mycorrhizal (AM) fungus Glomus caledonium. EDTA was applied to the soil to mobilize Zn and thus maximize plant Zn uptake. The highest plant dry matter (DM) yields were obtained with a moderate Zn addition level of 300 mg kg?1. Plant growth was enhanced by mycorrhizal colonization when no Zn was added and under the highest Zn addition level of 600 mg kg?1, while application of EDTA to the soil generally inhibited plant growth. EDTA application also increased plant Zn concentration, and Zn accumulation in the roots increased with increasing EDTA addition level. The effects of inoculation with Gcaledonium on plant Zn uptake varied with Zn addition level. When no Zn was added, Zn translocation from roots to shoots was enhanced by mycorrhizal colonization. In contrast, when Zn was added to the soil, mycorrhizal colonization resulted in lower shoot Zn concentrations in mycorrhizal plants. The P nutrition of the maize was greatly affected by AM inoculation, with mycorrhizal plants showing higher P concentrations and P uptake. The results indicate that application of EDTA mobilized soil Zn, leading to increased Zn accumulation by the roots and subsequent plant toxicity and growth inhibition. Mycorrhizal colonization alleviated both Zn deficiency and Zn contamination, and also increased host plant growth by influencing mineral nutrition. However, neither EDTA application nor arbuscular mycorrhiza stimulated Zn translocation from roots to shoots or metal phytoextraction under the experimental conditions. The results are discussed in relation to the environmental risk associated with chelate-enhanced phytoextraction and the potential role of arbuscular mycorrhiza in soil remediation.  相似文献   

6.
Leaching of metals due to enhanced mobility during ethylenediaminetetraacetic acid (EDTA)-assisted phytoextraction has been demonstrated as one of the potential hazards associated with this technology. This study was conducted to determine phytoextraction efficiency of Chenopodium album L. for Pb and EDTA-assisted (1.5, 3, and 9 mmol kg?1) phytoextraction and potential for leaching of Pb. The results demonstrated that BCFshoot (bioconcentration factor) was relatively higher than the BCFroot. Translocation factor in the shoot was higher than the roots. Thus, plant species would be applicable for Pb phytoextraction. EDTA enhanced translocation of Pb from roots to shoots. Lead content in the plant parts was maximum in the shoot and root of 9EDTA and 3EDTA, respectively. However, there was no significant difference between 3EDTA and 9EDTA. Lead concentration in the plant parts increased significantly from vegetative stage into flowering stage. Lead content taken up by the plant was lowest when EDTA was applied in a single dose. Therefore, application of EDTA in several increments rather than a single split reduced the leaching risk. Totally, optimum phytoextraction was observed when 3 mmol kg?1 EDTA was added in triple dosage 60 days after the plant cultivation under triple application mode. The results indicated the plant has the potential for Pb phytoextraction, but it should not be used unless the biomass containing such accumulated metal is removed for disposal. Significant improvement over current ETDA-assisted phytoextraction of Pb may be possible but should be implemented cautiously because of environmental risk.  相似文献   

7.
Enhancement of Pb and Zn uptake by Indian mustard (Brassica juncea (L.) Czern.) and winter wheat (Triticum aestivumL.) grown for 50 days in pots of contaminated soil was studied with application of elemental sulphur (S) and EDTA. Sulphur was added to the soil at 5 rates (0–160 mmol kg?1) before planting, and EDTA was added in solution at 4 rates (0–8 mmol kg?1) after 40 days of plant growth. Additional pots were established with the same rates of S and EDTA but without plants to monitor soil pH and CaCl2-extractable heavy metals. The highest application rate of S acidified the soil from pH 7.1 to 6.0. Soil extractable Pb and Zn and shoot uptake of Pb and Zn increased as soil pH decreased. Both S and EDTA increased soil extractable Pb and Zn and shoot Pb and Zn uptake. EDTA was more effective than S in increasing soil extractable Pb and Zn, and the two amendments combined had a synergistic effect, raising extractable Pb to ¿1000 and Zn to ¿6 times their concentrations in unamended control soil. Wheat had higher shoot yields than Indian mustard and increasing application rates of both S and EDTA reduced the shoot dry matter yields of both plant species to as low as about half those of unamended controls. However, Indian mustard hyperaccumulated Pb in all EDTA treatments tested except the treatment with no S applied, and the maximum shoot Pb concentration was 7100 mg kg?1 under the highest application rates of S and EDTA combined. Wheat showed similar trends, but hyperaccumulation (1095 mg kg?1) occurred only at the highest rates of S and EDTA combined. Similar trends in shoot Zn were found, but with lower concentrations than Pb and far below hyperaccumulation, with maxima of 777 and 480 mg kg?1 in Indian mustard and wheat. Despite their lower yields, Indian mustard shoots extracted more Pb and Zn from the soil (up to 4.1 and 0.45 mg pot?1) than did winter wheat (up to 0.72 and 0.28 mg pot?1), indicating that the effects of S and EDTA on shoot metal concentration were more important than yield effects in determining rates of metal removal over the growth period of 50 days. Phytoextraction of Pb from this highly contaminated soil would require the growth of Indian mustard for nearly 100 years and is therefore impractical.  相似文献   

8.
Heavy metal pollution in soils and the high costs of remediation necessitate the evaluation of cheaper alternatives. The aim of this experiment was to evaluate Cd, Pb, Zn, and Cu sorption characteristics of three soils and their influence on the comparative effectiveness of EDTA and legume intercrop on the remediative abilities of maize, mucuna, okra, and kenaf. The sorption studies were done using standard procedures. The EDTA-assisted phytoextraction (6 mmol kg?1) and the cowpea intercrop trials were conducted in triplicate. The metal-spiked soils were planted with maize, kenaf, and mucuna in the EDTA trial and maize, kenaf, and okra were planted in the cowpea intercrop experiment. Cadmium was prefentially sorbed in acid and alkaline soils and Cu in slightly acid soil. Cadmium uptake was significantly lower (P < 0.05) in all the plants. Bioconcentration factors of Pb, Cu, and Zn were higher (P < 0.05) in maize compared with other plants. Phytoremediative ability of the plants in trials were maize > kenaf > mucuna and okra > maize > kenaf, respectively. It was concluded that a legume intercrop can substitute EDTA- assisted phytoextraction to prevent groundwater contamination resulting from high solubility of metals by EDTA.  相似文献   

9.
Phytoextraction is an emerging technology for non-destructive remediation of heavy metal-polluted soils. This study was conducted to test chelate-assisted phytoextraction of Cu, Pb and Zn using EDTA and canola (Brassica napus L. cv. Petranova) on a moderately polluted industrial soil (loamy sand) in the sub-continental climate of Eastern Austria. The effects of the rate (up to 2.1 g kg–1 soil) and mode (single versus split) of EDTA application on the biomass, water contents and metal concentrations in shoots and roots were investigated along with changes of metal lability in soil and leaching from the root zone in parallel outdoors pot and lysimeter experiments. Labile (1 M NH4NO3-extractable) metal concentrations in soil increased considerably upon application of EDTA, indicating enhanced phytoavailability. However, this was also associated with enormously increased metal concentrations in the leachates collected below the root zone. Enhanced metal labilities and leachate concentrations persisted for more than 1 year after harvest. Metal lability was more enhanced by EDTA in rhizosphere relative to bulk soil, indicating interactions of EDTA with root activities. Shoot biomass and water contents of canola were virtually unaffected by EDTA, revealing that canola can tolerate excessive metal concentrations in soil pore water. Metal concentrations in shoots were increased considerably, but were insufficient to obtain reasonable extraction rates. Split applications were generally more effective than the same amounts of EDTA added at once. Metal concentrations in roots decreased after each application of EDTA, possibly indicating metal removal from roots by free protonated EDTA, but increased again within several days. As the application of chelate-assisted phytoextraction is limited by the risk of groundwater pollution, further work should focus on natural, continuous phytoextraction technologies.  相似文献   

10.
Greenhouse and field trial experiments were performed to evaluate the use of Chromolaena odorata with various soil amendments for phytoextraction of Pb contaminated soil Pb mine soils contain low amount of nutrients, so the additions of organic (cow manure) and inorganic (Osmocote and NH4NO3 and KCl) fertilizers with EDTA were used to enhance plant growth and Pb accumulation. Greenhouse study showed that cow manure decreased available Pb concentrations and resulted in the highest Pb concentration in roots (4660 mg kg(-1)) and shoots (389.2 mg kg(-1)). EDTA increased Pb accumulation in shoots (17-fold) and roots (11-fold) in plants grown in soil with Osmocote with Pb uptake up to 203.5 mg plant(-1). Application of all fertilizers had no significant effects on relative growth rates of C. odorata. Field trial study showed that C. odorata grown in soil with 99545 mg kg(-1) total Pb accumulated up to 3730.2 and 6698.2 mg kg(-1) in shoots and roots, respectively, with the highest phytoextraction coefficient (1.25) and translocation factor (1.18). These results indicated that C. odorata could be used for phytoextraction of Pb contaminated soil. In addition, more effective Pb accumulation could be enhanced by Osmocote fertilizer. However, the use of EDTA in the field should be concerned with their leaching problems.  相似文献   

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