Evaluation of phytoextracting cadmium and lead by sunflower,ricinus,alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium （Cd） and lead （Pb） is hard to be remediated. Phytoremediation may be a feasible method to remove toxic metals from soil, but there are few suitable plants which can hyperaccumulate metals. In this study, Cd and Pb accumulation by four plants including sunflower （Helianthus annuus L.）, mustard （Brassicajuncea L.）, alfalfa （Medicago sativa L.）, ricinus （Ricinus communis L.） in hydroponic cultures was compared. Results showed that these plants could phytoextract heavy metals, the ability of accumulation differed with species, concentrations and categories of heavy metals. Values of BCF （bioconcentration factor） and TF （translocation factor） indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals. Changes on the biomass of plants, pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures. Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals, such as pH and Eh regulations, and so forth.

Selection of appropriate organic additives for enhancing Zn and Cd phytoextraction by hyperaccumulators

Chelant-enhanced phytoextraction is one of the most promising technologies to remove heavy metals from soil. The key of the technology is to choose suitable additives in combination with a suitable plant. In the present study, laboratory batch experiment of metal solubilization, cress seeds germination were undertaken to investigate the metal-mobilizing capability and the phytotoxicity of organic additives, including ethylene diamine triacetic acid （EDTA）, citric acid, acetic acid, oxalic acid, glutamine and monosodium glutamate waste liquid （MGWL） from food industry. Experiments in pots were carried out to study the effects of the additives on Zn and Cd phytoextraction. Furthermore, a leaching experiment with lysimeter was performed to evaluate the environmental risks of additive-induced leaching to underground water. The results showed that EDTA had a strong mobilizing ability for Zn and Cd, followed by mixed reagent （MR） and MGWL. MGWL and acetic acid at 5 mmol equivalent per liter resulted in seed germination index less than 2%. Experiments in pots verified the phytotoxicity of acetic acid and MGWL. Addition of the mixed reagent at 6--10 mmol/kg significantly increased Zn phytoextraction by Thlaspi caerulescens. The same for EDTA and the mixed reagent at 10 mmol/kg by Sedum dfredii. But only mixed reagents could significantly increase Cd phytoextraction by the studied hyperaccumulators. This suggested that the strong chelant was not always the good agent to enhance phytoextraction. S. alfredii combined with 2--10 mmol/kg soil MR was preferred for phytoremediation of Cd/Zn contaminated soils in southern China, this could result in high phytoextraction of Cd/Zn and reduce the leaching risk to underground water than EDTA assisted phytoextration.

Phytoextraction:A Cost-effective Approach to Metal-contaminated Soils

This paper will review the topic of phytoextraction,a major approach of phytoremediation,by clarifying the roles of hyperaccumulators,bio-mechanisms involved,issues regarding contaminant uptake,artificial chelation,genetic selection,and cultivation.The paper will also address the practical issues and the regulatory context of this emerging technology and briefly discuss avenues for future research.

Comparison on the phytoextraction efficiency of Bidens pilosa at heavy metal contaminated site in natural and electrokinetic conditions

The plant samples of Bidens pilosa were collected from a coal gangue vacant site and its surrounding area,located in central China,to study the remediation effect of the plant species on heavy metal(HM)contamination in both natural and electrokinetic(EK)conditions.The analytical results showed that the effect of phytoextraction and bioconcentration on the heavy metals in the sample of the EK group is more significant than those in the other control group.Compared with the results of natural condition,under the EK condition the concentrations of cadmium(Cd),lead(Pb),copper(Cu)and zinc(Zn)in the stems and leaves of the Bidens pilosa increased to 0.40 mg/kg,4.23 mg/kg,7.27 mg/kg,830.24 mg/kg,respectively,with their increments of 292%,1731%,141%,2076%.For root samples,the Cd,Pb,Cu and Zn concentrations increased to 0.52 mg/kg,4.36 mg/kg,10.87 mg/kg,and 98.12 mg/kg and the increase rates were 1034%,140%,29%,and 181%,respectively.The phytoextraction efficiency of the Bidens pilosa was significantly higher than that of control group.The removal efficiency of Cd,Pb,Cu and Zn in soil increased to 26%,72%,27%,and 79%with the EK applied.In addition,the mechanism of HM migration,extraction and enrichment in Bidens pilosa under the EK condition was discussed.

Isolation of Mucor circinelloides Z4 and Mucor racemosus Z8 from heavy metal-contaminated soil and their potential in promoting phytoextraction with Guizhou oilseed rap

Fungi Z4 and Z8, isolated from the heavy metal polluted soil, have strong resistance to Cd and Pb. The strains were identified on the base of their morphology and internal transcribed spacers(ITS) region. Pot experiments were conducted to study the effect of two strains(Z4 and Z8) on the growth and accumulation of Cd and Pb of Guizhou oilseed rape. The results show that strains Z4 and Z8 belong to Mucor circinelloides and Mucor racemosus, respectively. The heights of Guizhou oilseed rape inoculated with strain Z8 increase by 47.90% than the control. The highest fresh mass is found in the plant with Z4/Z8, which is enhanced by160.81%. Pot experiments show that Z4/Z8 inoculums can accelerate accumulation of heavy metals in the plant. The contents of Cd and Pb are increased by 117.60% and 63.48%, respectively. Meanwhile, the heavy metal concentrations in potting soil with the two strains are found to be lower than those of the control, and the concentrations of Cd and Pb are decreased by 60.57% and 27.12%,respectively.

Phytoextraction of Trace Metals (Cd, Ni and Pb) by Panicum maximum Grown on Natural Soil

This study aims to assess the effective capacity of Panicum maximum to accumulate cadmium (Cd), nickel (Ni) and lead (Pb). P. maximum observed in a greenhouse was subjected to 2 ppm of Cd, 50 ppm of Ni, 100 ppm of Pb contaminated soil and uncontaminated soil, for 120 days. Plant growth and biomass produced concentration of trace metals in soil and plant, bioaccumulation and transfer factors, location of potentially toxic elements in tissues and cells of plant have been determined. Stem length and biomass produced by P. maximum were higher on the uncontaminated soil followed respectively by those of soil-contaminated by Pb, Cd and Ni. Bioaccumulation factors of trace metals were 8.93 (Pb), 8.47 (Ni) and 3.37 (Cd). Ni was more accumulated in shoot biomass (FT > 1), while Pb and Cd were concentrated in root biomass (FT < 1). Pb is accumulated preferentially in endodermis (roots) and epidermis (leaves). As for Ni and Cd, they are concentrated in central cylinder of roots and in conductive bundles of leaves. At cellular level, Ni and Cd are mainly concentrated in intracellular compartments of leaves and roots, while Pb is strongly detected at cell walls.

Status of carbohydrate,protein and lipid profile in the mosquito larvae treated with certain phytoextracts

Objective:To investigate the impact of the most potent petroleum ether extract of Artemisia annua(A.annua) and Azadirachta indica(Az.indica) on total carbohydrate,lipid and protein level of Anopheles stephensi and Culex quinquefasciatus larvae.Methods:Mosquito larvae were exposed to the extracts selected as per standard WHO procedure.Carbohydrate(glucose),total lipid and protein were estimated by the methods as Nelson,Bragdon and Lowry described, respectively.Results:The glucose levels were increased to 27.87%and 46.8%,respectively in anopheline larval tissues after treatment with petroleum ether extract of A.annua and methanolic extract of Az.indica.In culicine larvae,glucose levels were reduced to 58.96%and 24.65%, respectively.After treatment with A.annua extract,lipid contents in anopheline and culicine larvae decreased by 28.57%and 25.0%,respectively and increased by 14.29%and 50.00%in the Anopheles and Culex larvae,respectively after treatment with methanolic extract of Az. indica.Total protein levels were reduced to 63.13%and 92.62%in anopheline and to 32.39%and 48.12%in culicine larvae after treatment with A.annua and Az.Indica extracts,respectively. Conclusions:Two extracts produce significant alterations in the biochemical pr of iles of anopheline and culicine larvae.Further,the impacting factors of extracts on carbohydrate,lipid and protein contents of larvae are species and specific extraction.It indicates the disturbed metabolic activity of the larvae.

Tissue culture tools for selenium hyperaccumulator Neptunia amplexicaulis for development in phytoextraction

Neptunia amplexicaulis is an herbaceous legume endemic to the Richmond area in central Queensland,Australia and is one of the strongest known Selenium hyperaccumulators on earth,showing significant potential to be utilised in Se phytoextraction applications.Here a protocol was established for in vitro micropropagation of Se hyperaccumula-tor N.amplexicaulis using nodal segments from in vitro-germinated seedlings.Shoot multiplication was achieved on Murashige and Skoog(MS)basal media supplemented with various concentrations of 6-Benzylaminopurine(BA)(1.0,2.0,3.0 mg L^(−1))alone or in combination with low levels of Naphthaleneacetic acid(NAA)(0.1,0.2,0.3 mg L^(−1)),with 2.0 mg L^(−1) BA+0.2 mg L^(−1) NAA found to be most effective.Elongated shoots were rooted in vitro using NAA,with highest root induction rate of 30%observed at 0.2 mg L^(−1) NAA.About 95%of the in vitro rooted shoots survived acclimatization.Clonally propagated plantlets were dosed with selenate/selenite solution and assessed for Se tissue concentrations using Inductively Coupled Plasma Atomic Emission Spectroscopy(ICP-AES)and found to retain their ability to hyperaccumulate.The protocol developed for this study has potential to be optimised for generating clonal plants of N.amplexicaulis for use in research and phytoextraction industry applications.

Phytoextraction of Metal Contaminants by Typha Angustifolia: Interaction of Lead and Cadmium in Soil-Water Microcosms

A greenhouse study was conducted on phytoextraction and accumulation of lead (Pb) and cadmium (Cd) from contaminated soil – water microcosms by the narrow-leaved cattail, Typha angustifolia. The plants were grown in sandy loam soil containing 1,666 and 38.5 mg/L of Pb(NO3)2 and Cd(NO3)2 respectively. The trends of lead and cadmium by T. angustifolia for all soil – water microcosms suggested interaction effects as decreased soil lead concentrations and increased water cadmium concentrations over time. T. angustifolia expressed trends as increased biomass in all contaminated shoots and roots examined. Cadmium uptake in shoot and root biomass slightly decreased when lead was initially added to the soil but cadmium uptake in root biomass increased after 30 days. Data suggested an interaction between lead and cadmium and possible that lead uptake was inhibited when cadmium was present.

Phytoextraction Capacity of <i>Chrysopogon nigritanus</i>Grown on Arsenic Contaminated Soil

This study aims to investigate the capacity of Chrysopogon nigritanus to accumulate As from contaminated soils. The experiment was conducted in a greenhouse. C. nigritanus was subjected to uncontaminated soil and As contaminated soil (50 mg/kg, 100 mg/kg and 150 mg/kg of As), for 180 days. Plant growth and biomass produced, concentration of As in soil and plant, bioaccumulation and transfer factors, as the location of As in tissues and cells of the plant have been determined. Plant growth decreased significantly with increasing of soil As concentration. C. nigritanus accumulated more As in roots biomass. The highest bioaccumulation factor values were found in contaminated soil at 50 mg As/kg (As 50), then contaminated soil at 100 mg As/kg (As 100) and contaminated soil at 150 mg As/kg (As 150). As was essentially fixed to the intracellular compartment of the roots, stems and leaves. In roots tissues, As was mainly retained in the rhizodermis and the pericycle. While in stems tissues, As was preferentially accumulated in the conductive bundles. In the leaves, the final destination of As was epidermis tissues.

A Comparison of the Solubilizing Potential of Some Aminopolycarboxylic Acids, Hortrilon^(█)and Fetrilon^(█)for Use in Phytoextraction

Phytoextraction has been introduced as a new technology to clean up soils contaminated with heavy metals as the use of conventional methods to clean up the soil is very expensive and destructive to the ecosystem. However, using plants to clean up contaminated soils takes a considerable period before the contaminants are removed from the soil by the plants. This has necessitated the use of amendments to enhance phytoextraction in order to shorten the period of contaminants removal by plants. In view of this, a pot experiment was conducted to study the effect of various aminopolycarboxylic acids (EDTA, EDDS, NTA dry and NTA liquid) and two commercial fertilizers which are Hortrilon? and Fetrilon? on their ability to solubilize Cd and Zn in contaminated soils. It was observed that the inducing effect of EDTA on the solubility of Cd and Zn persisted throughout the experimental period. Initially, EDDS enhanced the solubility Cd and Zn, however, its effect dissipated with time. The application of both NTA dry (powder) and NTA liquid had a significant effect on the solubility of Zn as a result of the formation of Zn-NTA soluble complexes. Hortrilon? and Fetrilon? solubilized significant concentrations of both Cd and Zn with Hortrilon? having the greatest inducing effect on the solubility of Cd and Zn.

Rhizobacteria helps to explain the enhanced efficiency of phytoextraction strengthened by Streptomyces pactum

The ultimate purpose of phytoextraction is not only to remove heavy metals from soil but also to improve soil quality.Here, we evaluated how the joint effect of Streptomyces pactum(strain Act12) and inorganic(Hoagland’s solution) and organic(humic acid and peat) nutrients affected the phytoextraction practice of cadmium(Cd) and zinc(Zn) by potherb mustard, and the microbial community composition within rhizosphere was also investigated.The results indicated that the nutrients exerted synergistically with Act12, all increasing the plant biomass and Cd/Zn uptakes.The inoculation of Act12 alone significantly increased dehydrogenase activity of rhizosphere soil(P<0.05), while urease and alkaline phosphatase activities varied in different dosage of Act12.Combined application of microbial strain with nutrients increased enzymatic activities with the elevated dosage of Act12.16S ribosomal RNA high-throughput sequencing analysis revealed that Act12 inoculation reduced the diversity of rhizosphere bacteria.The Act12 and nutrients did not change dominant phyla i.e.,Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria and Acidobacteria, but their relative abundance differed among the treatments with: Peat>Act12>Humic acid >Hoagland’s solution.Comparatively, Sphingomonas replaced Thiobacillus as dominant genus after Act12 application.The increase in the Sphingomonas and Flavisolibacter abundances under Act12 and nutrients treatments gave rise to growth-promoting effect on plant.Our results revealed the important role for rhizosphere microbiota in mediating soil biochemical traits and plant growth, and our approach charted a path toward the development of Act12 combined with soil nutrients to enhance soil quality and phytoextraction efficiency in Cd/Zn-contaminated soils.

滇东地质高背景区土壤镉的伴矿景天修复及其对后茬水稻的影响

云南是我国典型的重金属元素地球化学高背景区,超积累植物能否有效修复镉(Cd)地质高背景土壤,从而实现农产品安全生产,尚鲜见报道。以云南石林、富源和罗平等三地的典型Cd地质高背景农田土壤为对象,开展温室盆栽试验,探究Cd、锌(Zn)超积累植物伴矿景天对土壤Cd的吸取修复效果,及对后茬水稻生长和Cd吸收的作用。结果表明,种植三季伴矿景天使三地土壤全量Cd分别下降24.8%、30.9%和58.8%;伴矿景天在富源玄武岩风化物母质发育的土壤上长势最好,与富源土壤肥力相对最高有关;伴矿景天在罗平石灰岩风化物发育的土壤上重金属吸取修复效果最佳,与罗平土壤呈中性、酸化作用更为明显有关,这些差异由土壤母质、养分与重金属有效性等综合影响所致。经伴矿景天吸取修复三季后,全生育期淹水种稻,其糙米和秸秆Cd浓度均大幅降低,可实现糙米Cd安全生产。未经植物吸取修复,旱作处理下水稻糙米Cd存在超标风险。植物吸取修复后种植水稻,再结合水分管理措施,可进一步降低稻米中Cd浓度,实现稻米安全生产,为Cd地质高背景区土壤的农作物安全生产提供理论依据和技术支撑。

不同强化剂强化德国景天提取土壤镉和铅研究

为提高超富集植物对土壤中镉(Cd)、铅(Pb)污染物的植物提取效率,以德国景天为研究对象,通过盆栽试验,研究了6种化学强化剂:鼠李糖脂生物表面活性剂(Rha)、乙二胺二琥珀酸(EDDS)、聚丙烯酸(PAA)、聚丙烯酸接枝腐殖酸(PAA-HA)、植物调节剂增产胺(DCPTA)、增产胺接枝氯化胆碱(DCPTA-ChCl)强化德国景天提取农田土壤Cd和Pb的效果,并考察不同强化剂对土壤重金属Cd、Pb形态的影响。结果表明,6种添加剂处理均能促进德国景天根部对Cd的吸收,DCPTA、DCPTA-ChCl、PAA、PAA-HA处理对德国景天地上部分Cd的吸收表现为促进作用,而Rha和EDDS抑制了Cd从根部向地上部分的转移。PAA-HA对德国景天根部吸收Pb的促进作用最为显著,对应的吸收提高率为51.7%。德国景天对Cd和Pb的富集系数(BCF)范围为3.96~4.83和0.11~0.19,转移系数(TF)为2.19~3.05和0.19~0.39,属于Cd超富集植物。德国景天修复重金属污染土壤中,聚丙烯酸类添加剂、增产胺类生长调节剂有效促进了德国景天对Cd和Pb的吸收富集,在土壤重金属污染植物修复中具有很好的应用潜力。

强化植物提取修复镉污染耕地的研究进展

开展镉污染耕地治理与修复关乎国家生态安全、粮食安全、食品安全等重大战略需求。植物提取修复技术具有原位、彻底、绿色、成本低、环境扰动小等优点,但局限于修复效率低、周期长,强化植物提取修复技术被认为是解决这一问题的关键。文章从如何提高植物提取修复效率入手,概述了修复植物的筛选,系统阐述了化学强化、微生物强化、农艺调控强化以及联合强化措施等的辅助修复潜力。对强化植物提取修复镉污染耕地的未来研究方向进行了展望,包括拓展筛选适于中、轻度镉污染耕地修复的高生物量经济作物,开发更多环境友好、高效、低廉的新型强化材料,加强不同土壤-植物-强化措施修复效果的探索,关注联合强化措施的协同机理探究。

Plant coexistence can enhance phytoextraction of cadmium by tobacco (Nicotiana tabacum L.) in contaminated soil

A mesocosm experiment was conducted to investigate whether plant coexistence affects cadmium （Cd） uptake by plant in contaminated soil. Tobacco （Nicotiana tabacum L. var. K326） and Japanese clover （Kummerowia striata （Thunb.） Schindl.） were used. Cadmium was applied as 3CdSO4.SH2O in solution at three levels （0, 1, and 3 mg/kg soil） to simulate an unpolluted soil and soils that were slightly and moderately polluted with Cd. Tobacco （crop）, Japanese clover （non-crop）, and their combination were grown under each Cd treatment. Compared to monoculture and under all Cd treatments, co-planting with Japanese clover did not affect tobacco biomass but significantly increased Cd concentration in all tobacco tissues and enhanced Cd accumulation in tobacco shoots and roots. Compared to monoculture, co-planting reduced soil pH and increased Cd bioavailability. For tobacco, co-planting with Japanese clover increased the Cd bioconcentration factor （BCF） in Cd contaminated soil. Japanese clover also accumulated substantial quantities of Cd in shoots and roots. Thus, total Cd uptake by the plants was much greater with co-planting than with monoculture. The results suggested that phytoextraction can be effectively increased through tobacco co-planting with Japanese clover in mildly Cd-contaminated soil.

螯合诱导植物修复铀污染土壤的研究进展

土壤中的铀植物可利用性低,这会限制植物提取对铀污染土壤的修复效果。螯合剂可以使土壤中铀的赋存形态由难被植物吸收利用态转化为易被植物吸收利用态,达到活化铀的效果,从而辅助根系吸收铀。然而,植物往往难以在短时间内吸收大量被活化了的铀,可能导致植物中毒,并增加土壤铀淋溶进入地下水的风险,造成二次污染。本文对1996-2023年螯合诱导植物修复重金属和放射性核素污染土壤的研究进行文献计量学分析,归纳了螯合诱导植物修复技术的潜在环境风险,并针对螯合剂活化土壤铀速率过快的问题提出应用缓释技术,达到控制螯合剂在土壤中释放速率的目的,同时进一步梳理了代表性生物降解缓释载体材料和缓释螯合剂的释放机理,探讨了缓释螯合诱导植物修复的效果及其发展趋势,以期为缓释螯合剂在铀污染土壤植物修复领域的应用提供新的途径。结果表明:①目前在螯合诱导植物修复技术领域应用广泛的螯合剂包括以EDTA(乙二胺四乙酸)和EDDS(乙二胺二琥珀酸)为代表的氨基多羧酸类螯合剂,以及以柠檬酸为代表的低分子量有机酸类螯合剂,应用广泛的富集植物包括印度芥菜、向日葵和黑麦草等,其中黑麦草对铀具有较好的富集能力。②螯合剂虽然可以提高植物提取土壤铀的效率,但螯合剂本身的毒性作用及其在土壤中的残留效应可能导致植物中毒、干扰微生物群落,降低土壤质量;此外,施用螯合剂后产生的大量不能被及时吸收的活化铀可能会增加土壤铀淋溶进入地下水的风险。③代表性生物降解缓释载体材料可分为天然聚合物、合成聚合物和无机材料三大类,其中单一材料作为缓释载体均存在机械强度较差的缺点,需要通过改性延长缓释周期。④缓释螯合剂的释放机理分为水吸附、涂层/基质膨胀、水扩散3个阶段。⑤现有缓释螯合剂的制备过程往往加入多种有毒有害化学试剂。今后需要研发绿色合成技术制备生物降解缓释螯合剂,确保绿色可持续修复过程。

Emerging contaminants: Evaluation of degradable chelators towards enhancing cadmium phytoextraction efficiency of bioenergy crop grown on polluted soil

Exogenous application of chelators towards enhancing heavy metals extraction efficiency of bioenergy crop has received considerable attention in recent time.However,little is known about optimal application rate,comparative evaluation of degradable versus non-degradable chelators and their impact on cadmium(Cd)speciation and uptake,physiological and biochemical activity of sweet sorghum grown under Cd stress.Four chelators namely,Nitrilotriacetic acid(NTA),tetrasodium N,N-diacetate(TDA),Ethylenediamine tetraacetic acid(EDTA),iminodisuccinic acid(IDA)and control(CK)were applied and compared at rates of 2,5,and 10 mmol kg^(-1) towards augmenting phytoextraction efficiency of sweet sorghum for Cd remediation in a screen house study.Results showed that sweet sorghum augmented with TDA significantly(P<0.05)increased biomass,enhanced Cd uptake and accumulation when compared to EDTA at application rate of 2-5 mmol kg1.TDA influenced Cd speciation via increasing acid-soluble,reducible,oxidizable,and residual fractions of Cd,thus increasing Cd bioavailability.NTA and TDA increased proline concentrations,antioxidant enzymes and net photosynthetic activity rate(Pn)comparably to EDTA in sweet sorghum,thus enhancing stress tolerance and stabilizing photosynthetic activities.Overall,exogenous application of degradable TDA at 2-5 mmol kg^(-1) could be recommended as replacement for non-degradable EDTA in a chelate assisted approach towards augmenting bioenergy crop for phytoremediation of Cd polluted soil.