Phytoremediation of lead (Pb) and Arsenic (As) by Melastoma malabathricum L. from Contaminated Soil in Separate Exposure

This study was conducted to investigate the uptake of lead (Pb) and arsenic (As) from contaminated soil using Melastoma malabathricum L. species. The cultivated plants were exposed to As and Pb in separate soils for an observation period of 70 days. From the results of the analysis, M. malabathricum accumulated relatively high range of As concentration in its roots, up to a maximum of 2800 mg/kg. The highest accumulation of As in stems and leaves was 570 mg/kg of plant. For Pb treatment, the highest concentration (13,800 mg/kg) was accumulated in the roots of plants. The maximum accumulation in stems was 880 mg/kg while maximum accumulation in leaves was 2,200 mg/kg. Only small amounts of Pb were translocated from roots to above ground plant parts (TF < 1). However, a wider range of TF values (0.01–23) for As treated plants proved that the translocation of As from root to above ground parts was greater. However, the high capacity of roots to take up Pb and As (BF > 1) is indicative this plants is a good bioaccumulator for these metals. Therefore, phytostabilisation is the mechanism at work in M. malabathricum's uptake of Pb, while phytoextraction is the dominant mechanism with As.     

Heavy metals accumulation and distribution in durum wheat and barley grown in contaminated soils under Mediterranean field conditions

Abstract

In the framework of a phytoremediation project in the Apulia region (Italy) a field experiment was carried out in multi-metal contaminated soils. The accumulation and distribution of metals in different plant parts of durum wheat and barley were studied. Further, the application of Bacillus licheniformis strain BLMB1 to soil was evaluated as a means to enhance metal accumulation in plants. The translocation and the bioconcentration factors indicated that wheat and barley do not act as metal accumulators in the field conditions tested, thus phytoextraction by these species would not be recommended as a soil remediation alternative. Application of B. licheniformis improved the accumulation of all metals in roots of wheat and barley, and increased Cd, Cr, and Pb contents in the shoots of barley. Low health risk for humans and animals was evaluated to exist if straw and grain from both cereal crops grown in these contaminated sites are consumed.     

The effects of iron plaque and phosphorus on yield and arsenic accumulation in rice

The effects of arsenate, Fe²⁺, and phosphate on amount and composition of Fe-oxide plaque at the rice-root surface and on the yield and arsenic accumulation in rice (cv. BRRI dhan33) were studied in a replicated pot-culture experiment. Arsenic in the form of Na₂HAsO₄ was applied at concentrations of 0, 15 and 30 mg kg^?1 in combination with P and/or Fe at 0 and 50 mg kg^?1, from KH₂PO₄ and FeSO₄, respectively. Root, grain and straw yields and their As, Fe and P concentrations were determined. The Fe-oxide plaque was extracted from the plant roots using dithionite-citrate-bicarbonate (DCB) and NH₄-oxalate extractions. The addition of Fe²⁺ reduced the toxic effect of As in flooded-rice culture and resulted in reduced grain-As accumulation and increased grain yields. The effect of applied phosphate was the opposite, in that it resulted in higher As concentrations in both grain and straw and lower grain yields. The effects of both Fe and P can be explained based on their impacts on adsorption of As onto soil and rice-plaque Fe-oxides and the subsequent As solubility and availability for uptake by rice. These reactions have important implications to rice-crop management and the natural variability in soils and irrigation-water characteristics that might impact As uptake by rice.     

Soil-applied zinc and copper suppress cadmium uptake and improve the performance of cereals and legumes

The present study aimed to evaluate the effect of soil-applied Zn and Cu on absorption and accumulation of Cd applied through irrigation water in legume (chickpea and mung bean) and cereal (wheat and maize) crops. The results revealed that Cd in irrigation water at higher levels (2 and 5 mg L^?1) significantly (p < 0.05) reduced the plant biomass while the soil application of Zn and Cu, singly or combined, favored the biomass production. Plant tissue Cd concentration increased linearly with the increasing application of Cd via irrigation water. While Cd application caused a redistribution of metals in grains, straw, and roots with the highest concentration of Cd, Zn, and Cu occurred in roots followed by straw and grains. Zinc addition to soil alleviated Cd toxicity by decreasing Cd concentration in plant tissues due to a possible antagonistic effect. The addition of Cu to the soil had no consistent effects on Zn and Cd contents across all crops. Inhibitory effects of Cd on the uptake and accumulation of Zn and Cu have also been observed at higher Cd load. Thus, soil-applied Zn and Cu antagonized Cd helping the plant to cope with its toxicity and suppressed the toxic effects of Cd in plant tissues, thus favoring plant growth.     

水稻不同品种对铅吸收、分配的差异及机理

为探究水稻不同品种对Pb吸收积累的差异及机理,以20个不同基因型水稻品种(系)为材料,采用盆栽方法,研究了Pb在水稻植株各器官中的分配及在籽粒中的分布．结果表明,不同品种间,Pb积累量存在显著差异,但品种间的这种差异与品种类型关系不明显;不同器官、不同生育时期,Pb积累量和积累速率不同;各器官Pb浓度按根、茎、叶、穗、籽粒的顺序大幅度下降,分配到籽粒中的Pb比例很低;根与茎,茎与叶片、穗(抽穗期)、籽粒Pb含量呈极显著负相关;根与叶、穗(抽穗期)、籽粒,叶与穗(抽穗期)、籽粒的Pb含量呈正相关,相关性大多达极显著或显著水平;不同品种抽穗期叶片与成熟期籽粒间的Pb含量达显著正相关;Pb在稻米加工各产物中的分布很不均匀,稻谷经脱壳及精加工1次(2min)后,精米Pb含量仅为籽粒总含Pb量的32．88％．     

氯离子在土壤水分与作物生长关系研究中的指示作用

以小麦为试材,采用盆栽试验和氯离子指示技术,研究了不同土壤水分条件下,小麦在苗期对氯离子的吸收与累积特性和同期土壤中氯离子迁移特征。结果表明:(1)氯离子在小麦体内的累积与土壤含水量的关系密切,小麦苗期根系中氯离子累积量决定于根系与氯离子的接触几率,在植物地上部分的分配依赖于蒸腾强度;(2)在土壤含水量较低条件下,氯离子在根部累积明显,向地上部分移动不强,而在高含水量(18%)情况下,向地上部移动累积较为明显,氯离子在植物体中累积与分配关系很好地指示了土壤水分条件与植物生长之间关系;(3)在生长发育期间,当土壤含水量低于18%时小麦根系以伸长主动觅水,满足蒸腾需要为主;高于18%时,土壤水分移动以补偿根际蒸腾为主,土壤水分强烈的液态迁移存在着明显的临界含水量,可以用土壤剖面上氯离子含量的变化过程确定小麦根系水分利用的有效土层深度,以便准确地计算水分生产效率。因此,氯离子作为指示元素,在研究旱地土壤水分条件、水分移动能力等与作物生长的关系方面具有一定的可行性。     

Fluorene and Phenanthrene Uptake and Accumulation by Wheat,Alfalfa and Sunflower from the Contaminated Soil

Polycyclic Aromatic Hydrocarbons (PAHs) are diverse organic contaminants released into the environment by both natural and anthropogenic activities. These compounds have negative impacts on plants growth and development. Although there are many reports on their existence in different parts of plant, their uptake and translocation pathways and mechanisms are not well understood yet. This paper highlights the uptake, translocation and accumulation of PAHs by wheat, sunflower and alfalfa through an experimental study under controlled conditions. Seeds were cultivated in a soil containing 50 mg/kg of phenanthrene and fluorene and their concentrations in plants roots and shoots were determined using a gas chromatograph after 7 and 14 days. The results showed that phenanthrene and fluorene concentrations in the treated plants were increased over the time. PAHs bioavailability was time and species dependent and generally, phenanthrene uptake and translocation was faster than that of fluorene, probably due to their higher K_ow. Fluorene tended to accumulate in roots, but phenanthrene was transported to aerial parts of plants.     

Phytoremediation of lead by a wild,non-edible Pb accumulator Coronopus didymus (L.) Brassicaceae

Coronopus didymus was examined in terms of its ability to remediate Pb-contaminated soils. Pot experiments were conducted for 4 and 6 weeks to compare the growth, biomass, photosynthetic efficiency, lead (Pb) uptake, and accumulation by C. didymus plants. The plants grew well having no visible toxic symptoms and 100% survivability, exposed to different Pb-spiked soils 100, 350, 1500, and 2500 mg kg^?1, supplied as lead nitrate. After 4 weeks, root and shoot concentrations reached 1652 and 502 mg Pb kg^?1 DW, while after 6 weeks they increased up to 3091 and 527 mg Pb kg^?1 DW, respectively, at highest Pb concentration. As compared to the 4 week experiments, the plant growth and biomass yield were higher after 6 weeks of Pb exposure. However, the chlorophyll content of leaves decreased but only a slight decline in photosynthetic efficiency was observed on exposure to Pb at both 4 and 6 weeks. The Pb accumulation was higher in roots than in the shoots. The bioconcentration factor of Pb was > 1 in all the plant samples, but the translocation factor was < 1. This suggested C. didymus as a good candidate for phytoremediation of Pb-contaminated soils and can be used for future remediation purposes.     

EDTA and Pb—EDTA accumulation in Brassica juncea grown in Pb—amended soil

Previous studies have shown that EDTA is necessary to solubilize soil Pb and facilitate its transport from the soil to the above ground plant tissues. These studies have also suggested that Pb is accumulated in the plant tissue with transpiration as the driving force. We conducted further studies to evaluate the relationship between EDTA soil treatment, plant transpiration, and plant accumulation of Pb and EDTA. Indian mustard (Brassica juncea) plants were grown in soils containing Pb at three different concentrations (1.5, 3.0 and 4.8 mmol/kg) for 5 weeks before being treated with EDTA concentrations ranging from 0 to 10 mmol/kg. Plant shoots and xylem sap were collected and analyzed for Pb and EDTA content using ICP and HPLC, respectively. Water loss was measured for 7 days following EDTA application. Transpiration was not affected at <5 mmol/kg EDTA but, at 10 mmol/kg EDTA transpiration decreased by 80%, whereas accumulation of Pb and EDTA increased. In the Sassafras soil, Pb and EDTA accumulation in the plant shoots continued to increase as the applied EDTA concentration increased, except at the highest level (10 mmol/kg). In soil amended with 4.8 mmol/kg Pb and 10 mmol/kg EDTA, the concentrations of EDTA and Pb in shoots decreased and visible signs of phytotoxicity were observed. The results presented herein support recent studies in hydroponic systems showing that EDTA and Pb are taken up by the plant and suggest that Pb is translocated in the plant as the Pb-EDTA complex. The results also show that the maximum Pb accumulation by plants occurs by maximizing the concentration of the Pb-EDTA complex based on the EDTA extractable soil Pb. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relative effectiveness of various types and methods of zinc application on rice and maize crops grown in calcareous soil

Summary Application of zinc sulphate mixed with compost/poultry manure proved to be equivalent to the effect of dipping the seedling roots in 4% ZnO suspension with respect to rice yields but Zn-amended organic manures were superior to other treatments with regards to total Zn uptake. A marked residual effect of soil applied treatments was recorded on the succeeding maize crop. Application of poultry manure alone was about one and a half times more effective than compost alone in increasing the rice and maize grain yields. Poultry manure surpassed compost in increasing zinc uptake by the crops and at the same time it built up more available Zn in soil than compost for the following crop. The magnitude of yields and Zn uptake response were magnified when zinc sulphate was applied along with organic manures. Application of 25 kg zinc sulphate/ha alone had the same effect as 50 quintals poultry manure alone or 12.5 kg zinc sulphate applied with 50 quintals compost/ha with respect to crop yields. A significant positive correlation was, recorded in both the crops between Zn concentration in grain or straw and their respective yields.     

农作物体内铅,镉,铜的化学形态研究

本文报道了农作物体内重金属存在的化学形态。用逐步提取法分析了生长在污染土壤上的水稻、小麦的根与叶。结果表明,在两种作物中,根部的铅以活性较低的醋酸可提取态与盐酸可提取态占优势,而叶中的铅以盐酸可提取态占优势。不论根部或叶部,在各种形态镉中,以氯化钠可提取镉所占比例较高,作用较重要。作物体内的铜活性较强,根部以乙醇可提取态占优势,叶中以水提取态占优势。各种结合形态的重金属迁移能力、毒性效应有显著差异。作物体内重金属化学形态特征与其表观毒性效应有密切联系。     

Effects of soil amendments and EDTA on lead uptake by Chromolaena odorata: greenhouse and field trial experiments

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.     

Cd、Zn、Pb及其相互作用对烟草、小麦的影响

烟草对Cd、Zn、Pb是一种敏感性作物,Cd、Zn、Pb对烟草的影响比对小安、水稻都大。 Cd、Zn、Pb在烟草各器官中的累积随土壤Cd、Zn、Pb浓度的增高而增大。 Cd、Zn、Pb在烟草各器官中含量的次序为:茎叶>根>籽粒。它们在根中受阻,而较易转移到茎叶和籽粒中。 烟草对Pb的吸收比对Zn和Cd明显地低。Pb仍然是一种低吸收性元素。 土壤Zn增加,减低了烟草对Cd的吸收,而土壤Pb的增加,则促进了烟草对Cd的吸收。     

麦秸翻压还田对隔茬冬小麦旗叶抗性的生理效应

为了揭示秸秆翻压还田对冬小麦旗叶叶片衰老及抗性指标的变化规律,试验设置4个小麦秸秆翻压还田量(0、4500、6000、7500kg/hm2),测定分析了冬小麦旗叶叶绿素含量、光合速率、丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性及可溶性蛋白质含量等抗性指标。结果表明,秸秆还田可明显减缓冬小麦植株衰老过程中叶片叶绿素的降解和光合速率下降,并有效调节叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)活性下降、可溶性蛋白质含量下降和丙二醛(MDA)含量的增加,延缓了冬小麦生育后期叶片的衰老;通过对各抗性指标与光合速率的相关性分析表明,各抗性指标在抑制冬小麦衰老过程中的作用大小依次为:丙二醛>可溶性蛋白质>POD活性>SOD的活性(丙二醛-0.999**;可溶性蛋白质0.997**;POD活性0.976*;SOD活性0.954*)。综合各处理的抗性指标得出,处理Ⅲ(6000kg/hm2)在提高作物后期抗逆性能力方面表现较好,处理Ⅳ(7500kg/hm2)表现较差。     

Role of rhizosphere mechanisms in Cd uptake by various wheat cultivars

In each wheat type, cultivars have different propensities to accumulate Cd in their grains, likely depending on Cd uptake by roots and/or Cd distribution in the plant. This study investigates the processes in the root–soil interface and their role in high or low grain Cd accumulation. Twenty-four cultivars of spring bread, winter bread, durum, and spelt wheat with different grain Cd accumulation levels were investigated regarding removal of Cd from soil, pH, Cd and organic acids in root exudates, and cation-exchange capacity of roots (rootCEC). In addition, we investigated ¹⁰⁹Cd uptake from a nutrient solution resembling soil solution. The removal of Cd from the rhizosphere soil increased, likely due to increased rootCEC with increased grain Cd accumulation propensity, except in spring bread wheat. The ¹⁰⁹Cd uptake from solution did not differ between high and low grain Cd accumulators. If the soil Cd concentration was elevated, rootCEC increased, as did pH, and succinic acid levels in the exudates, while lactic and citric acid levels in root exudates decreased. This work indicates that high grain Cd accumulators take up more Cd from soil than do low accumulators. But not by a different capacity to take up Cd from soil solution. The higher rootCEC in high accumulating cultivars may influence the release of Cd from the soil particles.     

Salt distribution around roots of wheat under different transpiration rates

Summary Magnitude of Na and Cl accumulation around wheat roots was studied under different transpiration conditions in a loamy sand soil salinized with sodium chloride to an electrical conductivity of 4.1 mmho/cm in the saturation extract. A significant correlation was observed between rate of water loss per unit root length and Na and Cl content of the soil closely adhering to the roots. Under high transpiration condition, maximum ion accumulation occurred in the apparent free space of roots followed by the soil closely adhering to the roots. Results indicate that salt concentration at the root surface is markedly altered under the influence of transpiration rate such that under high transpiration conditions, the plant roots may be exposed to a much higher salt concentration than that anticipated from an analysis of the bulk soil samples.Department of Soil and Water EngineeringDepartment of Soils     

The effect of EDTA and EDDS on lead uptake and localization in hydroponically grown Pisum sativum L.

Pisum sativum plants were treated for 3 days with an aqueous solution of 100 μM Pb(NO₃)₂ or with a mixture of lead nitrate and ethylenediaminetetraacetic acid (EDTA) or [S,S]-ethylenediaminedisuccinic acid (EDDS) at equimolar concentrations. Lead decline from the incubation media and its accumulation and localization at the morphological and ultrastructural levels as well as plant growth parameters (root growth, root and shoot dry weight) were estimated after 1 and 3 days of treatment. The tested chelators, especially EDTA, significantly diminished Pb uptake by plants as compared to the lead nitrate-treated material. Simultaneously, EDTA significantly enhanced Pb translocation from roots to shoots. In the presence of both chelates, plant growth parameters remained considerably higher than in the case of uncomplexed Pb. Considerable differences between the tested chelators were visible in Pb localization both at the morphological and ultrastructural level. In Pb+EDTA-treated roots, lead was mainly located in the apical parts, while in Pb+EDDS-exposed material Pb was evenly distributed along the whole root length. Transmission electron microscopy and EDS analysis revealed that in meristematic cells of the roots incubated in Pb+EDTA, large electron-dense lead deposits were located in vacuoles and small granules were rarely noticed in cell walls or cytoplasm, while after Pb+EDDS treatment metal deposits were restricted to the border between plasmalemma and cell wall. Such results imply different ways of transport of those complexed Pb forms.     

Toxic Effects of Pb on Anatomy and Hypericin Content in Hypericum perforatum L.

Lead (Pb) is one of the most common heavy metal contaminants in the environment. The present study was therefore undertaken to determine the effects of Pb on structural characteristics and hypericin production in Hypericum perforatum. Mature plants were treated with contaminated soil in seven treatments (75, 150, 300, 600, 800, 1000, and 1500 mg/kg Pb in soil) with three repeats per treatment every 14 days. Maximum observed Pb content in shoot parts was observed in the treatments with 600 and 1500 mg/kg Pb. The Pb concentration in roots was higher than in shoot parts, enhanced with increasing Pb concentration in the soil. In this study, Pb treatment significantly influenced the morphology, anatomy, and hypericin content in the plant. Anatomical characteristics of leaf, stem, and root affected by Pb contamination, as well as scanning electron microscopy (SEM) studies, revealed structural changes in stomata and epicuticular waxes. Under Pb toxicity, anatomical symptoms occurred in leaves, including increase in sizes of epidermal cells, mesophyll tissue, and diameter of stems and roots, as well as amplified vascular bundles and pith area. This, therefore, indicated that metal contamination can change the chemical composition of this plant. Maximum hypericin content was observed in the treatment containing 600 mg/kg Pb in soil, which then decreased.     

Effect of organic and mineral fertilizers on N-use by wheat under different irrigation frequencies

A field trial was established in Errachidia, southern Morocco, to investigate the interaction between wheat residue management and mineral 15N-labelled ammonium sulphate, under different irrigation treatments, applied to wheat (Triticum durum var. Karim). In treatments I1, I2, I3 and I4, plots were irrigated every 10, 15, 21 and 30 days. Each plot contained three sub-plots that received three fertilization treatments: T1 received 42 kg N ha-1 of ammonium sulphate before seedling, 42 kg N ha-1 of ammonium sulphate labelled with 9.764 at % 15N excess at tillering and 84 N kg ha-1 of ammonium sulphate at flowering; T2 received 42 kg N ha-1 of ammonium sulphate labelled with 9.764 at % 15N excess at seedling, 42 kg N ha-1 at tillering and 42 kg N ha-1 at flowering; T3 received 4800 kg ha-1 of wheat residue labelled with 1.504 at % 15N excess and 42 kg N ha-1 of ammonium sulphate before seedling and 42 kg N ha-1 of ammonium sulphate at flowering. Nitrogen fertilization with 168 kg N ha-1 did no significantly increase grain and straw yields in comparison to the 126 kg N ha-1 application. The combination of the organic input and supplementary application of mineral fertilizer N has been found as a more attractive management option. For all irrigation treatments, the % recovery of N in the whole plant was higher in plants that received 15N at tillering (63%, 49% respectively for irrigation intervals between 10 and 30 d) than in plants that received 15N just after seeding (28% for irrigation each 10- and 30-d intervals). For the irrigation treatment each 10 and 15 days, the 15N was mainly recovered by the grain for all fertilization treatments, whereas for irrigation treatment each 30 days, the grain and straw recovered nearly equal amounts of fertilizer. For grain and straw of wheat, nitrogen in the plant derived from the fertilizer was low, while most of the N was derived from the soil for all irrigation and fertilization treatments. The % nitrogen in the plant derived from the fertilizer values showed no significant difference between the different plant parts. The results suggested a dominant influence of moisture availability on the fertilizer N uptake by wheat. Under dry conditions the losses of N can be allotted to denitrification and volatilisation.     

Performance of rose scented geranium (Pelargonium graveolens) in heavy metal polluted soil vis-à-vis phytoaccumulation of metals

An investigation was carried out to evaluate the effect of heavy metal toxicity on growth, herb, oil yield and quality and metal accumulation in rose scented geranium (Pelargonium graveolens) grown in heavy metal enriched soils. Four heavy metals (Cd, Ni, Cr, and Pb) each at two levels (10 and 20 mg kg–1 soil) were tested on geranium. Results indicated that Cr concentration in soil at 20 mg kg–1 reduced leaves, stem and root yield by 70, 83, and 45%, respectively, over control. Root growth was significantly affected in Cr stressed soil. Nickel, Cr, and Cd concentration and accumulation in plant increased with higher application of these metals. Chromium, nickel and cadmium uptake was observed to be higher in leaves than in stem and roots. Essential oil constituents were generally not significantly affected by heavy metals except Pb at 10 and 20 ppm, which significantly increased the content of citronellol and Ni at 20 ppm increased the content of geraniol. Looking in to the higher accumulation of toxic metals by geranium and the minimal impact of heavy metals on quality of essential oil, geranium can be commercially cultivated in heavy metal polluted soil for production of high value essential oil.