Effects of long-term exposure to zinc on performances of anaerobic digesters for swine wastewater treatment under various organic loading rates.

The long-term performance of anaerobic digestion (AD) often decreases substantially when treating swine wastewater contaminated with heavy metals. However, the toxicological characteristics and mechanisms of continuous exposure to heavy metals under different organic loading rates (OLR) are still poorly understood. In these semi-continuous AD experiments, it was found that zinc concentrations of 40 mg/L only deteriorated the reductive environments of AD. In comparison, a concentration of 2.0 mg/L probably facilitated the reproduction of microorganisms in the operating digesters with a constant OLR of 0.51 g COD/(L·d). Nevertheless, when the OLR was increased to 2.30 g COD/(L·d), 2.0 mg/L zinc inhibited various life activities of microorganisms at the molecular level within only 10 days. Hence, even though 2.0 mg/L zinc could promote AD performances from a macroscopic perspective, it had potential inhibitory effects on AD. Therefore, this study deepens the understanding of the inhibitions caused by heavy metals on AD and the metabolic laws of anaerobic microorganisms in swine wastewater treatment. These results could be referred to for enhancing AD in the presence of zinc in practical swine wastewater treatment.

Efficient Proton Transfer and Charge Separation within Covalent Organic Frameworks via Hydrogen-Bonding Network to Boost H2O2 Photosynthesis.

Photocatalytic synthesis based on the oxygen reduction reaction (ORR) has shown great promise for H2O2 production. However, the low activity and selectivity of 2e- ORR result in a fairly low efficiency of H2O2 production. Herein, we propose a strategy to enhance the proton-coupled electron transfer (PCET) process in covalent organic frameworks (COFs), thereby significantly boosting H2O2 photosynthesis. We demonstrated that the construction of a hydrogen-bonding network, achieved by anchoring the H3PO4 molecular network on COF nanochannels, can greatly improve both proton conductivity and photogenerated charge separation efficiency of COFs. Thus, COF@H3PO4 exhibited superior photocatalytic performance in generating H2O2 without sacrificial agents, with a solar-to-chemical conversion efficiency as high as 0.69%. Results indicated that a much more localized spatial distribution of energy band charge density on COF@H3PO4 led to efficient charge separation, and the small energy barrier of the rate-limiting step from *OOH to H2O2 endowed COF@H3PO4 with higher 2e- ORR selectivity.

Electronic Phosphide-Support Interactions in Carbon-Supported Molybdenum Phosphide Catalysts Derived from Metal-Organic Frameworks.

Interfacial interaction in carbon-supported catalysts can offer geometric, electronic, and compositional effects that can be utilized to regulate catalytically active sites, while this is far from being systematically investigated in carbon-supported phosphide catalysts. Here, we proposed a novel concept of electronic phosphide-support interaction (EPSI), which was confirmed by using molybdenum phosphide (MoP) supported on nitrogen-phosphorus codoped carbon (NPC) as a model catalyst (MoP@NPC). Such a strong EPSI could not only stabilize MoP in a low-oxidation state under environmental conditions but also regulate its electronic structure, leading to reduced dissociation energy of the oxygen-containing intermediates and enhancing the catalytic activity for oxidative desulfurization. The removal of dibenzothiophene over the MoP@NPC was as high as 100% with a turnover frequency (TOF) value of 0.0027 s-1, which was 33 times higher than that of MoP without EPSI. This work will open new avenues for the development of high-performance supported phosphide catalysts.

Enhanced poly(3-hydroxybutyrateco-3-hydroxyvalerate) production from high-concentration propionate by a novel halophile Halomonas sp. YJ01: Detoxification of the 2-methylcitrate cycle.

As a carbon substrate, propionate can be used to synthesize poly(3-hydroxybutyrateco-3-hydroxyvalerate) [PHBV] biopolymer, but high concentrations can inhibit PHBV production. Therefore, novel PHBV producers that can utilize high propionate concentrations are needed. Here, a novel halophile, Halomonas sp. YJ01 was applied to PHBV production via a propionate-dependent pathway, and optimal culture growth conditions were determined. The maximum poly(3-hydroxybutyrate) [PHB] content and yield in the presence of glucose were 89.5 wt% and 5.7 g/L, respectively. This strain utilizes propionate and volatile fatty acids (VFAs) for PHBV accumulation. Multiple genes related to polyhydroxyalkanoate (PHA) synthesis were identified using whole-genome annotation. The PHBV yield and 3HV fraction obtained by strain YJ01 utilizing 15 g/L propionate were 0.86 g/L and 29 mol%, respectively, but in cultures with glucose-propionate, it decreased its copolymer dry weight. This indicates that propionyl-CoA was converted to pyruvate through the 2-methylcitrate cycle (2MCC), which reduced propionate detoxification for the strain.

Aging microplastic aggravates the pollution of heavy metals in rhizosphere biofilms.

Heavy metals (HMs) and microplastics (MPs) are ubiquitous in agricultural soils. Rhizosphere biofilms are important sites for HM adsorption, and biofilms are easily disturbed by soil MPs. However, the adsorption of HMs on rhizosphere biofilms induced by aged MPs is not clear. In this study, the adsorption behavior of Cd(II) on biofilms and pristine/aged polyethylene (PE/APE) was analyzed and quantified. The results showed that the adsorption amount of Cd(II) on APE was greater than that on PE, in which the oxygen-containing functional groups of APE could provide binding sites to increase the adsorption of HMs. Density functional theory (DFT) calculations revealed that the binding energy of Cd(II) onto APE (-6.00 kcal·mol-1) was much stronger than that of PE (7.11 kcal·mol-1) due to hydrogen bonding interactions and oxygen atom-metal interactions. For HM adsorption on MP biofilms, APE increased the adsorption capacity of Cd(II) by 4.7 % relative to PE. The pseudo-second-order kinetic and Langmuir models suitably described the adsorption kinetics and isothermal adsorption of Cd(II), respectively (R2 > 80 %), indicating that monolayer chemisorption dominated. However, the hysteresis indices of Cd(II) in the Cd(II)-Pb(II) system (< 1) were higher than those in the single system (> 1) due to the competitive adsorption of HMs. Overall, this study clarifies the effect of MPs on the adsorption of HMs in rhizosphere biofilms and will help researchers assess the ecological risks of HMs in soils.

Assessing Pb-Cr Pollution Thresholds for Ecological Risk and Potential Health Risk in Selected Several Kinds of Rice.

The expected typical gley moist paddy soil was collected in Zhejiang Province, China, and conventional (XS 134 and JH 218) and varieties of hybrid (YY 538 and CY 84) rices were used for a pot experiment. The effects of exogenous heavy metals lead (Pb) and chromium (Cr) on rice growth and the accumulation of heavy metals in the grains were studied. The results show that heavy metal concentrations in soil and rice grains have significant correlations, and Pb and Cr significantly (p < 0.05) inhibited the rice growth (plant height and panicle weight). The potential ecological hazard index (RI) of heavy metals in the soil was 4.88−6.76, which belongs to the grade of "slight ecological hazard", and Pb provides a larger potential ecological hazard than Cr in the studied region. The thresholds for potential health risks and ecological risks for Pb and Cr were lower than the "Control Standards for Soil Pollution Risk of Agricultural Land (Trial)" (GB15618-2018, China). This work provides the basis for soil pollution control for Pb and Cr and the selection of rice cultivars from Pb and Cr accumulated soils.

Interactions of microplastics and soil pollutants in soil-plant systems.

In recent years, increasing studies have been reported on characterization and detection of microplastics (MPs), and their interactions with organic pollutants (OPs) and heavy metals (HMs) in soils. However, a comprehensive review on the characteristics and factors that influence MPs distribution in soils, the sorption characteristics and mechanisms of soil contaminants by MPs, especially the interactions of MPs and their complexes with pollutants in the soil-plant systems remains rarely available at present. This review focuses on the sorption features and mechanisms of pollutants by MPs in soil and discussed the effects of MPs and their complexing with pollutants on soil properties, microbe and plants. The polarity of MPs significantly influenced the sorption of OPs, and different sorption mechanisms are involved for the hydrophobic and hydrophilic OPs. The sorption of OPs on MPs in soils is different from that in water. Aging of MPs can promote the sorption and migration of contaminants. The enhanced effects of biofilm in microplastisphere on the sorption of pollutants by MPs are critical, and interactions of soil environment-MPs-microbe-HMs-antibiotics increase the potential pathogens and larger release of resistance genes. The coexistence of HMs and MPs affected the growth of plants and the uptake of HMs and MPs by the plants. Moreover, the type, dose, shape and particle size of MPs have important influences on their interactions with pollutants and subsequent effects on soil properties, microbial activities and plant growth. This review also pointed out some knowledge gaps and constructive countermeasures to promote future research in this field.

Water quality assessment of east Tiaoxi River, China, based on a comprehensive water quality index model and Monte-Carlo simulation.

The comprehensive water quality index (CWQI) reflects the comprehensive pollution status of rivers through mathematical statistics of several water quality indicators. Using computational mathematical simulations, high-confidence CWQI predictions can be obtained based on limited water quality monitoring samples. At present, most of the CWQI reported in the literature are based on conventional indicators such as nitrogen and phosphorus levels, and do not include the petroleum hydrocarbons levels. This article takes a typical river in eastern China as an example, based on the 1-year monitoring at 20 sampling sets, a CWQI containing five factors, TN, NH4+-N, TP, ∑n-Alks, and ∑PAHs was established, and further predicted by a Monte-Carlo model. The predicted CWQI for each monitoring section is above 0.7, indicating that most of the monitoring sections are moderately polluted, and some sections are seriously polluted. The Spearman rank correlation coefficient analysis results show that TN, ∑PAHs, and ∑n-Alks are the main factors influencing the water quality, especially the petroleum hydrocarbons have a significant impact on the middle and lower reaches due to shipping. In the future, more attention should be paid to petroleum hydrocarbon organic pollutants in the water quality evaluation of similar rivers.

Surfactant-facilitated alginate-biochar beads embedded with PAH-degrading bacteria and their application in wastewater treatment.

Immobilized Pseudomonas aeruginosa beads with alginate and biochar as composite carriers and a nonionic surfactant (TX100) as degradation promoter were prepared by the gel embedding method. The optimal preparation parameters for the biochar addition amount and the concentrations of the bacterial suspension and TX100 were 1%, OD600 = 1 and 200 mg/L, respectively. The addition of TX100 can simultaneously promote biochar sorption of PAHs and PAH degradation by P. aeruginosa. The removal ratio of acenaphthene was 24% higher for the TX100-facilitated immobilized bacterial beads than the beads in the absence of TX100. The surfactant-facilitated immobilized bacterial beads can thoroughly remove PAHs in wastewater under the conditions of 10~50 °C, pH 2.5~10.5, and less than 0.2 mol/L NaCl. The immobilized bacterial beads are suitable for continuous-flow reactors, and 2-mm-diameter beads will achieve better application results than larger beads. The new immobilized material can be widely used in various wastewater treatment reactors and in the in situ remediation of organic polluted water.

Simultaneous degradation of n-hexane and production of biosurfactants by Pseudomonas sp. strain NEE2 isolated from oil-contaminated soils.

The presence of surfactants in biofilters could enhance hydrophobic VOC removal. In this study, blood agar plate, methylene blue agar plate and a culture with n-hexane as the only carbon source were used to screen strains that could biodegrade n-hexane and produce biosurfactants simultaneously. The effects of n-hexane concentration on n-hexane removal and biosurfactant production were also investigated. Results showed that such a strain identified to be Pseudomonas sp. Strain NEE2 was successfully isolated from oil-polluted soils. The biosurfactants production by this strain were dependent on the initial concentration of n-hexane (132-2640 mg/L). At the concentration of 2640 mg/L of n-hexane, the biosurfactants promoted n-hexane removal. At 132 mg/L of n-hexane, n-hexane removal efficiency on day 2 exceeded 60%. The synergistic mechanisms of n-hexane removal and biosurfactant production by Pseudomonas sp. Strain NEE2 were discussed including the enhanced mass transfer from gas to liquid phase, within the biofilm phase and biodegradation at the presence of biosurfactants as well as the consequently enhanced production of the biosurfactants. These results in this study proved that it is possible for microorganisms utilizing the synergistic effect of hydrophobic VOC degradation and biosurfactant production for cost-effective hydrophobic VOC removal in biofilters.

Enhanced biodegradation of n-hexane by Pseudomonas sp. strain NEE2.

Pseudomonas sp. strain NEE2 isolated from oil-polluted soils could biodegrade n-hexane effectively. In this study, the secretory product of n-hexane biodegradation by NEE2 was extracted, characterized, and investigated on the secretory product's enhanced effect on n-hexane removal. The effects of various biodegradation conditions on n-hexane removal by NEE2, including nitrogen source, pH value, and temperature were also investigated. Results showed that the secretory product lowered surface tension of water from 72 to 40 mN/m, with a critical micelle concentration of 340 mg/L, demonstrating that there existed biosurfactants in the secretory product. The secretory product at 50 mg/L enhanced n-hexane removal by 144.4% within 48 h than the control group. The optimum conditions for n-hexane removal by NEE2 were at temperature of 25-30 °C, pH value of 7-8, and (NH4)2SO4 as nitrogen source. Besides n-hexane, NEE2 could also utilize a variety of carbon sources. These results proved that NEE2 can consume hydrophobic volatile organic compounds (VOCs) to produce biosurfactants which can further enhance hydrophobic VOCs degradation.

Effects and mechanisms of phytoalexins on the removal of polycyclic aromatic hydrocarbons (PAHs) by an endophytic bacterium isolated from ryegrass.

Plant-endophyte synergism has been demonstrated to play a key role in the phytoremediation of contaminated water and soil. Phytoalexins, a type of chemical component in the plant apoplast, can be produced by plants in response to stimulation by endophytes. Phytoalexins may have distinct effects on the nutritional and metabolic functions of endophytes; however, direct evidence is not available to prove the effect of phytoalexins on the hydrophobic organic contaminants (HOC)-degradation activity of endophytes. In this paper, three different types of phytoalexins, coumarin, resveratrol and rutin, were selected to study their effect on the removal of polycyclic aromatic hydrocarbons (PAHs) by an endophytic bacterium Methylobacterium extorquens C1. The effects of the three phytoalexins on bacterial sorption and intracellular enzymatic activities were tested to further analyze the mechanism by which the phytoalexins affect the PAH degradation performance of M. extorquens C1. The results showed that the removal rate of PAHs by M. extorquens C1 increased in the presence of low levels of the three phytoalexins. The most effective concentrations of coumarin, resveratrol and rutin were 0.20, 0.15, and 0.25 mg/L, respectively, and the removal rate of PAHs was increased by approximately 18.3-35.0%. At the optimal concentrations, the three phytoalexins significantly promoted the sorption of PAHs by M. extorquens C1, and also enhanced the activities of catechol dioxygenases and dehydrogenase of M. extorquens C1. The positive effect of phytoalexins on both bacterial sorption and intracellular enzymatic activities promotes the overall removal of PAHs from endophytes. These results may deepen our understanding of plant-microbe cooperative mechanisms in the degradation of organic pollutants and provide a new approach for chemically enhanced bioremediation in the future.

Effects and mechanisms of anionic and nonionic surfactants on biochar removal of chromium.

This work found that the removal of chromium by a straw-derived biochar was significantly promoted or inhibited by various surfactants. For example, the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) inhibited the removal of Cr(VI) by the biochar but significantly promoted the removal of Cr(III) by the biochar. The nonionic surfactant Triton X-100 (TX-100) promoted the removal of Cr(VI) at low concentrations (< 100 mg L-1) but inhibited the removal at high concentrations. Different mechanisms were found for the two surfactants. As an anionic surfactant, surface-sorbed SDBS changed the surface functional groups of the biochar, making the biochar negative charged and changing the sorption ability of the biochar. For the nonionic TX-100, monomers and micelles in the aqueous phase had a major influence on the sorption of chromium due to the impact on the interfacial tension between the biochar and the solution phase as well as the solution pH. The results suggest that when biochar is used to treat heavy metal wastewater containing coexisting surfactants, the type and concentration of surfactants must be considered as important factors. Under certain surfactant conditions, biochar will enable the simultaneous and efficient removal of heavy metals and surfactants.

Removal of acenaphthene from water by Triton X-100-facilitated biochar-immobilized Pseudomonas aeruginosa.

By adding the nonionic surfactant Triton X-100 and using biochar as an immobilization carrier, a Triton X-100-facilitated biochar-immobilized Pseudomonas aeruginosa (TFBIP) material was prepared using the sorption method and was used to treat acenaphthene in water. The results showed that a low concentration of Triton X-100 simultaneously promoted the sorption capacity of the biochar and the degradation activity of P. aeruginosa, thereby significantly enhancing the removal of acenaphthene from water by the immobilized P. aeruginosa material. Compared with the control without Triton X-100, a low concentration of Triton X-100 significantly increased the acenaphthene removal rate by 20-50%. The optimal conditions for preparing the TFBIP were a loading time of 24 h, the use of a bacterial suspension with a concentration of OD600 = 0.2, and a Triton X-100 concentration of 10 mg L-1. The optimized TFBIP material could efficiently remove acenaphthene from water at temperatures of 10-50 °C, pH values of 4.5-10.5, and NaCl concentrations of up to 0.2 mol L-1. The new TFBIP material can be used for the treatment of wastewater and may also be directly used for the remediation of soils contaminated with organic pollutants.

Effect of zinc ions on nutrient removal and growth of Lemna aequinoctialis from anaerobically digested swine wastewater.

The effect of Zn2+ on ammonium and phosphorous removal and duckweed growth was evaluated for treatment of anaerobically digested swine wastewater (ADSW) at various initial Zn2+ concentrations ranging from 1.0 to 15mg/L. Lemna aequinoctialis taken from a local pond was selected for the treatment, and its fresh weight and contents of proteins, photosynthetic pigments, and vitamin E were examined. Results showed that the optimal Zn2+ concentration was 5.0mg/L for NH3-N and TP removal, the duckweed growth, and the accumulation of proteins in the duckweed. A maximum content of photosynthetic pigments increased with the increase of initial Zn2+ concentration, and it arrived earlier for a higher concentration of Zn2+. Vitamin E content in the duckweed reached 4.5mg/kg at 15mg/L Zn2+ in 12-day cultivation, which showed the potential for producing and harvesting a high value-added product of vitamin E by culturing duckweed in ADSW.

Effects of GA3 on Plant Physiological Properties, Extraction, Subcellular Distribution and Chemical Forms of Pb in Lolium perenne.

The effects of growth-promoting hormone gibberellic acid 3 (GA3) on physiology, Pb phytoextraction, and metal detoxification mechanisms in Lolium perenne were studied. Results showed that addition of GA3 alone at lower doses (1 or 10 µM) facilitated antioxidant defense of L. perenne under Pb stress, decreased the toxicity of Pb in plant shoot by increasing the proportion of Pb in cell wall, hence significantly enhanced photosynthesis and plant growth, as well as Pb uptake and accumulation in L. perenne (P < 0.05). However, these indicators showed the opposite changes when treated with GA3 at a higher dose (100 µM). Of the total Pb in plant shoot, 36-51% was associated with cell wall, and 31-40% was soluble fraction, while 41.4-49.7% was NaCl extractable, 24.6-35.4% HAc extractable followed by other fractions. These findings suggest that Pb fixation by pectates and proteins in cell wall and sequestration in vacuole are responsible for Pb detoxification in plant, and the GA3 at 1 µM appears to be optimal for enhancing Pb phytoextraction by L. perenne from Pb polluted soils.

Growth-Promoting Hormone DA-6 Assists Phytoextraction and Detoxification of Cd by Ryegrass.

A pot experiment was carried out to study the effect of growth-promoting hormone diethyl aminoethyl hexanoate (DA-6) on Cd phytoextraction and detoxification in ryegrass. Foliar spray of DA-6 significantly enhanced Cd extraction efficiency (P<0.05), with 1 µM DA-6 the most effective. At the subcellular level, 43-53% of Cd was soluble fraction and 23-46% in cell wall, and 9-25% in organelles. Chemical speciation analysis showed that 52.7-58.5% of Cd was NaCl extractable, 12.1-22.7% ethanol extractable, followed by other fractions. DA-6 alleviated metal toxicity by fixing more Cd in cell wall and decreasing Cd migration in plant. In conclusion, ryegrass tolerates Cd by cell wall compartmentalization along with protein and organic acids combination, and the treatment of 1 µM DA-6 appears to be optimal for enhancing the remediation efficiency of ryegrass for Cd contaminated soil.

Enhanced removal of ethylbenzene from gas streams in biotrickling filters by Tween-20 and Zn(II).

The effects of Tween-20 and Zn(II) on ethylbenzene removal were evaluated using two biotrickling filters (BTFs), BTF1 and BTF2. Only BTF1 was fed with Tween-20 and Zn(II). Results show that ethylbenzene removal decreased from 94% to 69% for BTF1 and from 74% to 54% for BTF2 with increased organic loading from 64.8 to 189.0 g ethylbenzene/(m³·hr) at EBRT of 40 sec. The effect of EBRT (60-15 sec) at a constant ethylbenzene inlet concentration was more significant than that of EBRT (30-10 sec) at a constant organic loading. Biomass accumulation rate within packing media was reduced significantly.

Synergetic effects of DA-6/GA3 with EDTA on plant growth, extraction and detoxification of Cd by Lolium perenne.

Research is needed to improve efficiency of phytoextraction of heavy metals from contaminated soils. A pot experiment was carried out to study the effects of plant growth regulators (PGRs) (diethyl aminoethyl hexanoate (C18H33NO8, DA-6) and gibberellic acid 3 (C19H22O6, GA3)) and/or EDTA on Cd extraction, subcellular distribution and chemical forms in Lolium perenne. The addition of EDTA or PGRs significantly enhanced Cd extraction efficiency (P<0.05), with the decreasing order of: 1 µM DA-6>10 µM DA-6>10 µM GA3>2.5 mmol kg(-1) EDTA>other treatments of PGR alone. PGRs+EDTA resulted in a further increase in Cd extraction efficiency, with EDTA+1 µM DA-6 being the most efficient. At the subcellular level, about 44-57% of Cd was soluble fraction, 18-44% in cell walls, and 12-25% in cellular organelles fraction. Chemical speciation analysis showed that 40-54% of Cd was NaCl extractable, 7-23% HAc extractable, followed by other fractions. EDTA increased the proportions of Cd in soluble and cellular organelles fraction, as well as the metal migration in shoot; therefore, the toxicity to plant increased and plant growth was inhibited. Conversely, PGRs fixed more Cd in cell walls and reduced Cd migration in shoot; thus, metal toxicity was reduced. In addition, PGRs promoted plant biomass growth significantly (P<0.05), with 1 µM DA-6 being the most effective. A combination of DA-6/GA3 with EDTA can alleviate the adverse effect of EDTA on plant growth, and the treatment of EDTA+1 µM DA-6 appears to be optimal for improving the remediation efficiency of L. perenne for Cd contaminated soil.

[Enhancement of GA3 and EDTA on Lolium perenne to remediate Pb contaminated soil and its detoxification mechanism].

A pot experiment was conducted to study the effects of plant growth regulator GA3 and metal chelate EDTA on enhancing the remediation of Pb contaminated soil, and the detoxification mechanism of Lolium perenne grown on Pb contaminated soil at 250 and 500 mg · kg(-1). The results showed that cell wall deposition and vacuolar compartmentalization played important roles in the detoxification of Pb in L. perenne shoot. The addition of EDTA alone increased Pb concentration in plants and Pb proportions in soluble fraction and organelles fraction, and enhanced the toxicity of Pb to plant, leading to the significant reduction of the plant biomass (P < 0.05). Foliar spray of lower concentration of GA3 (1 µmol · L(-1) or 10 µmol · L(-1)) alone significantly increased Pb accumulation by L. perenne (P < 0.05), but Pb proportions in soluble and organelles fraction were decreased, which alleviated the adverse effects of Pb on plant, thus improving the growth of plants (P < 0.05), with 1 µmol · L(-1) GA3 being the most effective. In contract, the addition of 100 µmol · L(-1) GA3 decreased Pb concentration in L. perenne, but increased the proportions of Pb in soluble fraction and organelles fraction, resulting in the reduction of plant biomass. Lower concen- tration of GA3 might alleviate the adverse effects of Pb and/or EDTA on plant, since the biomass amounts in the different treatments were in order of GA3 alone of lower concentration > GA3 of lower concentration + EDTA > EDTA alone. The combination application of low concentration of GA3 and EDTA showed a synergistic effect on the Pb accumulation in L. perenne (P < 0.05). Especially, Pb concentration in shoot and Pb extraction efficiency reached 1250.6 mg · kg(-1) and 1.1%, respec- tively, under the treatment of EDTA + 1 µmol L(-1) GA3 on the Pb 500 mg · kg(-1) soil. Therefore, the application of 1 µmol · L(-1) GA3 along with EDTA appeared to be a potential approach for phytoremediation of Pb contaminated soil.