Chelators effect on soil Cu extractability and uptake by Elsholtzia splendens

Phytoremediation is emerging as a potential cost-effective solution for remediation of contaminated soils, and bioavailability of metal in the soil for plant uptake is an important factor for successful phytoremediation. This study aimed at investigating the ability of EDTA and citric acid for enhancing soil bioavailability of Cu and phytoremediation by Elsholtzia splendens in two types of soils contaminated with heavy metals [i.e. mined soil from copper mining area (MS), and paddy soil (PS) polluted by copper refining]. The results showed that addition of 2.5 mmol/kg EDTA significantly increased the H2O extractable Cu concentration from 1.20 to 15.78 mg/kg in MS and from 0.26 to 15.72 mg/kg in PS, and that shoot Cu concentration increased 4-fold and 8-fold as compared to the control. There was no significant difference between the treatment with 5.0 mmol/kg EDTA and that with 2.5 mmol/kg EDTA, probably because that 2.5 mmol/kg EDTA was enough for elevating Cu bioavailability to the maximum level. As compared with the control, citric acid had no marked effect on both soil extractable Cu and shoot Cu concentration or accumulation. The results indicated that EDTA addition can increase the potential and efficiency of Cu phytoextraction by E. splendens in polluted soils.     

Chelators effect on soil Cu extractability and uptake byElsholtzia splendens

Phytoremediation is emerging as a potential cost-effective solution for remediation of contaminated soils, and bioavailability of metal in the soil for plant uptake is an important factor for successful phytoremediation. This study aimed at investigating the ability of EDTA and citric acid for enhancing soil bioavailability of Cu and phytoremediation by Elsholtzia splendens in two types of soils contaminated with heavy metals [i.e. mined soil from copper mining area (MS), and paddy soil (PS) polluted by copper refining]. The results showed that addition of 2.5 mmol/kg EDTA significantly increased the H₂O extractable Cu concentration from 1.20 to 15.78 mg/kg in MS and from 0.26 to 15.72 mg/kg in PS, and that shoot Cu concentration increased 4-fold and 8-fold as compared to the control. There was no significant difference between the treatment with 5.0 mmol/kg EDTA and that with 2.5 mmol/kg EDTA, probably because that 2.5 mmol/kg EDTA was enough for elevating Cu bioavailability to the maximum level. As compared with the control, citric acid had no marked effect on both soil extractable Cu and shoot Cu concentration or accumulation. The results indicated that EDTA addition can increase the potential and efficiency of Cu phytoextraction byE. splendens in polluted soils. Project supported by the National Natural Science Foundation of China (No. 29977017) and the Science and Technology Ministry of China (No. 2002CB410804)     

柠檬酸和草酸对茶园土壤铅生物有效形态的影响

为了探讨柠檬酸和草酸对茶园土壤中铅的化学形态的影响,采集无污染茶园土壤,喷施180mg/kg的硝酸铅,平衡后再添加不同浓度的柠檬酸或者草酸,分析土壤中水溶性铅和交换态铅含量的变化.结果表明,一定浓度的柠檬酸或者草酸对于土壤中水溶态铅和交换态铅的含量有降低作用,其效果与酸的类型和浓度有关.草酸对于土壤中有效性形态铅的降低作用优于柠檬酸,输入酸对于水溶态铅的降低作用强于对交换态铅的降低.当酸浓度达到0.2mmol/kg时,其降低作用最佳,之后随着输入酸浓度的升高,反而会增加土壤中有效性形态铅的含量.     

Changes of root morphology and Pb uptake by two species of Elsholtzia under Pb toxicity

Elsholtzia argyi and Elsholtzia splendens, which are Chinese endemic Pb/Zn mined and Cu mined ecotype respectively, were investigated on the aspect of their response to Pb toxicity in the presence or absence of EDTA addition. After 8 d's Pb treatment, root length, root surface area and root volume of E. splendens decreased much more than those ofE. argyi, and reduced considerably with increase of Pb, while no marked change was noted for root average diameter. Compared to E. argyi, length of root with diameter (D)＜0.2 mm was significantly reduced for E. splendens as Pb increased. D＜0.1 mm E. splendens root had cross-sectional surface area at Pb≥10 mg/L, while for E. argyi, it was at Pb＞25 mg/L. With increase ofPb, DW ofE. splendens decreased much more than that of E. argyi. E. argyi exhibited much more tolerance to Pb toxicity than E. splendens. Treatment with 100 mg/L Pb plus 50 mmol/L EDTA significantly decreased the length and surface area of D≤0.2 mm root, increased the length and surface area of 0.2≤D≤0.8 mm root for the case ofE. argyi, while for E. splendens, length and surface area of D＜0.6 mm root reduced, as compared to 100 mg/L Pb treatment, alone. At 100 mg/L Pb, shoot Pb accumulation in E. splendens and E. argyi were 27.9 and 89.0 μg/plant DW respectively, and much more Pb was uptaken by the root and translocated to the stem ofE. argyi as compared to E. splendens. Treatment of the plant with 100 mg/L Pb plus 50 mmol/L EDTA increased leaf Pb accumulation from 16.8 to 84.9 g/plant for E. splendens and from 18.8 to 52.5 g/plant for E. argyi, while both root and stem Pb pronouncedly reduced for both Elsholtzia species. The increased translocation of Pb to the leaf ofE. splendens being than that ofE. argyi after treatment with 100 mg/L Pb plus 50 mmol/L EDTA should be further investigated.     

BCR法研究铜矿区周边农田重金属形态分布

采用BCR(community bureau of reference)连续提取法对梅县玉水铜矿区周边农田土壤重金属Cu、Pb、Zn和Mn的形态分布及其生物有效性进行了分析.结果表明,矿区下游地区农田土壤重金属污染比上游严重,属于重污染区,而上游土壤属于轻度污染.矿区上游和下游农田土壤中,Pb的污染贡献最大.上游和下游土壤中Cu、Zn、Mn都主要分布在残渣态中,Pb主要分布在可还原态.上游和下游土壤中都以Pb的有效性最高,Zn的有效性最低.     

化学淋洗法修复重金属污染土壤效果研究

在国内外相关研究的基础上,文章研究化学淋洗修复技术在重金属污染土壤修复方面的运用．用浓酸消解土样并用火焰原子吸收法测定土壤中重金属含量,选用土壤柱作淋洗实验,分析去离子水和EDTA溶液两种淋洗剂对Cu、Zn、Pb、Cd四种重金属的淋洗效率,并对化学淋洗修复效果进行比较．     

Accumulation and ultrastructural distribution of copper in Elsholtzia splendens

Copper accumulation and intracellular distribution in Elsholtzia splendens, a native Chinese Cu-tolerant and accumulating plant species, was investigated by transmission electron microscope (TEM) and gradient centrifugation techniques.Copper concentrations in roots, stems and leaves of E. splendens increased with increasing Cu levels in solution. After exposure to 500 μmol/L Cu for 8 d, about 1000 mg/kg Cu were accumulated in the stem and 250 mg/kg Cu in the leaf of E. splendens. At 50μmol/L Cu, no significant toxicity was observed in the chloroplast and mitochondrion within its leaf cells, but separation appeared at the cytoplasm and the cell wall within the root cells. At ＞250 μmol/L Cu, both root and leaf organelles in E. splendens were damaged heavily by excessive Cu in vivo. Copper subcellular localization in the plant leaf after 8 days' exposure to 500 μmol/L Cu using gradient centrifugation techniques was found to be decreased in the order: chloroplast＞cell wall＞soluble fraction＞other organelles. The plant root cell wall was found to be the site of highest Cu localization. Increase of Cu exposure time from 8 d to 16d, increased slightly Cu concentration in cell wall fraction in roots and leaves, while that in the chloroplast fraction decreased in leaves of the plants grown in both 0.25 μmol/L and 500 μmol/L Cu. TEM confirmed that much more Cu localized in cell walls of E. splendens roots and leaves, but also more Cu localized in E. splendens' chloroplast when the plant is exposed to Cu levels＞250μmol/L, as compared to those in the plant grown in 0.25 μmol/L Cu. Copper treatment at levels＞250 μmol/L caused pronounced damage in the leaf chloroplast and root organelles. Copper localization in cell walls and chloroplasts could mainly account for the high detoxification of Cu in E. splendens.     

Review:Mycorrhizoremediation—an enhanced form of phytoremediation

INTRODUCTION Biosphere pollution by heavy metals and nu-cleotides was accelerated dramatically during the last few decades due to mining, smelting, manufacturing, treatment of agricultural soils with agro-chemicals and soil sludge, etc. Problems associated with the contamination of soil and water such as animal wel-fare, health, fatalities and disruptions of natural eco-systems are well documented (He et al., 2005). Heavy metals such as Pb, Cr, As, Cu, Cd, and Hg, being added to our so…     

Review: Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils

Heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. Rhizosphere, as an important interface of soil and plant, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria have received more and more attention. This article paper reviews some recent advances in effect and significance of rhizobacteria in phytoremediation of heavy metal contaminated soils. There is also a need to improve our understanding of the mechanisms involved in the transfer and mobilization of heavy metals by rhizobacteria and to conduct research on the selection of microbial isolates from rhizosphere of plants growing on heavy metal contaminated soils for specific restoration programmes.     

Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils

Heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. Rhizosphere, as an important interface of soil and plant, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria have re-ceived more and more attention. This article paper reviews some recent advances in effect and significance of rhizobacteria in phytoremediation of heavy metal contaminated soils. There is also a need to improve our understanding of the mechanisms in-volved in the transfer and mobilization of heavy metals by rhizobacteria and to conduct research on the selection of microbial isolates from rhizosphere of plants growing on heavy metal contaminated soils for specific restoration programmes.     

Mycorrhizoremediation an enhanced form of phytoremediation

Study of plant roots and the diversity of soil micro biota, such as bacteria, fungi and microfauna associated with them, is important for understanding the ecological complexities between diverse plants, microbes, soil and climates and their role in phytoremediation of contaminated soils. The arbuscular mycorrhizal fungi （AMF） are universal and ubiquitous rhizosphere mi- croflora forming symbiosis with plant roots and acting as biofertilizers, bioprotactants, and biodegraders. In addition to AMF, soils also contain various antagonistic and beneficial bacteria such as root pathogens, plant growth promoting rhizobacteria including free-living and symbiotic N-fixers, and mycorrhiza helping bacteria. Their potential role in phytoremediation of heavy metal （HM） contaminated soils and water is becoming evident although there is need to completely understand the ecological complexities of the plant-microbe-soil interactions and their better exploitation as consortia in remediation strategies employed for contaminated soils. These multitrophic root microbial associations deserve multi-disciplinary investigations using molecular, biochemical, and physiological techniques. Ecosystem restoration of heavy metal contaminated soils practices need to incorporate microbial biotechnology research and development. This review highlights the ecological complexity and diversity of plant-microbe-soil combinations, particularly AM and provides an overview on the recent developments in this area. It also discusses the role AMF play in phytorestoration of HM contaminated soils, i.e. mycorrhizoremediation.     

Spatial distribution of Cd and Cu in soils in Shenyang Zhangshi Irrigation Area （SZIA）, China

Heavy metal contamination of soils, derived from sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides, and so on, has been of wide concern in the last several decades. The Shenyang Zhangshi Irrigation Area (SZIA) in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years. This study investigated the spatial distribution and temporal variation of soil cadmium (Cd) and copper (Cu) contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd and Cu in soils was analyzed and then the spatial distribution and temporal variation of Cd and Cu in soils were modeled using Kriging methods. The results show that long-term sewage irrigation had caused serious Cd and Cu contamination in soils. The mean and the maximum of soil Cd are markedly higher than the levels in second grade standard soil (LSGSS) in China, and the maximum of soil Cu is close to the LSGSS in China in 2004 and is more than the LSGSS in China in 1990. The contamination magnitude of soil Cd and the soil extent of Cd con- tamination had evidently increased since sewage irrigation ceased in 1992. The contamination magnitude of soil Cu and the soil extent of Cu contamination had evidently increased in topsoil, but obviously decresed in subsoil. The soil contamination of Cd and Cu was mainly related to Cd and Cu reactivation of contaminated sediments in Shenyang Xi River and the import of Cd and Cu during irrigation. The eluviation of Cd and Cu in contaminated topsoil with rainfall and irrigation water was another factor of temporal-spatial variability of Cd and Cu contamination in soils.     

Effects of Hg and Cu on the activities of soil acid phosphatase

Comparative study on the activity and kinectic properties of acid phosphatase (ACPase) of three soils amended with Hg and Cu at constant temperature and humidity was carried out. The results indicated that the inhibition on ACPase of the three sample soils by Hg and Cu varied with the content of soil organic matter and pH, where, Soil 1 was the most seriously contami- nated due to its lowest content of organic matter and the lowest pH among three samples, Soil 2 took the second place, and Soil 3 was the least contaminated. Except Soil 3, the activity of soil ACPase tended to increase along with the contact time under the same type and the same concentration of heavy metal. In particular the Vmax values of ACPase in all three samples decreased with increasing Hg and Cu concentration, whereas the Km values were affected weakly. According to the change of Vmax and Km values, Cu and Hg had the same inhibition effect on soil ACPase. Both of them may be a type of compound of non-competitive and anti-competitive inhibition. Statistic analyses indicated that activities of soil ACPase and Vmax values could serve as bioindicator to partially denote the heavy metal Hg and Cu contamination degree.     

Phytoremediation potential of Cyperus rotundus for diesel-contaminated wetland

Oil spills may considerably damage sensitive coastal wetlands. The phytoremediation potential and restoration of a dominant coastal marsh plant, Cyperus rotundus, for diesel pollutant and its phytoremediation effectiveness were investigated in this open-air pot experiment. Cyperus rotundus was transplanted into soil contaminated with diesel at concentrations of 1 000, 5 000, 10 000, 15 000, 20 000 mg/kg. In order to better elucidate the biochemical and physiological responses to diesel pollutants, activity of the antioxidant enzymes peroxidase （POD）, catalase （CAT） and ascorbic acid oxidase （AAO） were determined in the plant tissue after 50 d treatment at the levels mentioned above. The results showed that CAT and AAO of stem and leaf exhibited peak enzyme activities on 15 000 mg/kg soil and 10 000 mg/kg soil respectively, and declined at higher concentrations. Additionally, the increment of biomass and the content of soluble protein, as well as chlorophyll content were affected by diesel. The highest restoration effectiveness appeared at the level of 5 000 mg/kg. Collectively, Cyperus rotundus is a potential plant which can be used for restoring the diesel-contaminated soil.     

豫灵冶炼厂周边土壤重金属污染及植物重金属累积特征研究

了解豫灵土壤污染现状和筛选重金属富集植物对污染土壤进行修复,采用火焰原子吸收光度法对豫灵冶炼厂周边土壤中重金属含量进行了测定,并对7种植物铅、镉的吸收和富集能力进行了研究,结果表明：豫灵冶炼厂周边土壤中Pb、Cd的含量严重超标,分别为821.574mg/kg和62.207mg/kg。采集的7种植物样品对Pb、Cd的吸收能力存在明显差异,苦荬菜、茵陈蒿和播娘蒿对Pb、Cd的吸收能力均较强,植物体内Pb的含量分别为423.95、358.275和303.5mg/kg,Cd的含量分别为54.60、49.425、55.175mg/kg。茵陈蒿和播娘蒿属于杂草,适应性强,利用其对矿区土壤进行修复,不经人工干预即可正常生长,成本较低,因此可作为该污染区土壤修复的选择物种。     

南京市城郊零散菜地土壤及青菜中重金属含量特征

采集了南京市城郊零散菜地土壤和青菜配对样品各18个,用原子吸收光谱仪测定了其中铜、锌、铅、镉的含量,结果表明:南京市城郊菜地土壤中Cu、Zn、Pb、Cd全量高于农区菜地土壤,Cu、Zn达到显著差异,重金属含量在土样之间有较大的变异性,反映了人为活动已对南京城郊土壤重金属产生了明显影响。城郊土壤上种植的青菜其可食部分重金属含量高于农区,尤其是对人体健康影响较大的Pb、Cd含量与农区相比存在显著差异,大大超过国家食品卫生标准。     

Aluminum extractability in red soils as influenced by land use patterns

This study on the effect of land use on soil quality in relation to forms and toxicity of aluminum in red soils (Ultisol) in southeast China showed that in general, the extractable order for soil active aluminum by four extractants was: NaOH 0.5 mol/L > HCl 1 mol/L > NH4Ac 1 mol/L > KCl 1 mol/L . Different uses of the red soils, developed from Quarternary red clay with the similar hydrogeological environment, greatly affected the amount of active aluminum, especially the exchangeable Al3+. The order of exchangeable Al3+ (Al mg/kg) in the red soils with different land uses was: barren land (740) > tea garden (663) > peach garden (432) > citrus garden (234) > paddy soil (127). The content of water soluble aluminum in the red soils was highly sensitive to soil acidity.     

Cadmium accumulation in different pakchoi cultivars and screening for pollution-safe cultivars

The selection and breeding of pollution-safe cultivars (PSCs) is a practicable and cost-effective approach to minimize the influx of heavy metal to the human food chain. In this study, both pot-culture and field experiments were conducted to identify and screen out cadmium pollution-safe cultivars (Cd-PSCs) from 50 pakchoi (Brassica rapa L. ssp. chinensis) cultivars for food safety. When treated with 1.0 or 2.5 mg/kg Cd, most of the pakchoi cultivars (>70%) showed greater or similar shoot biomass when compared with the control. This result indicates that pakchoi has a considerable tolerance to soil Cd stress. Cd concentrations in the shoot varied significantly (P<0.05) between cultivars: in two Cd treatments (1.0 and 2.5 mg/kg), the average values were 0.074 and 0.175 mg/kg fresh weight (FW), respectively. Cd concentrations in the shoots of 14 pakchoi cultivars were lower than 0.05 mg/kg FW. In pot-culture experiments, both enrichment factors (EFs) and translocation factors (TFs) of six pakchoi cultivars were lower than 1.0. The field studies further confirmed that the Hangzhouyoudonger, Aijiaoheiye 333, and Zaoshenghuajing cultivars are Cd-PSCs, and are therefore suitable for growth in low Cd-contaminated soils (≤1.2 mg/kg) without any risk to food safety.     

木薯渣饲用价值研究

木薯渣是淀粉厂和柠檬酸厂的下脚料,国内外每年废弃量相当大,严重污染了环境.本研究采用常规分析和原子吸收分光光度计等现代化先进仪器相结合,研究木薯渣的营养价值.经实验测得木薯渣各营养成分含量如下:粗蛋白4.92%,粗脂肪1.96%,粗纤维14.46%,粗灰份23.36%,无氮浸出物47.72%,消化能8.30(猪)兆焦/千克,代谢能(鸡)6.08兆焦/千克,元素Ca 8.45%,P 0.048%,Cu 24.02毫克/千克,Zn 47.30毫克/千克,Mn 66.20毫克/千克.木薯渣与三七糠相比具有较高的饲用价值.     

Competitive adsorption of Cd, Cu, Hg and Pb by agricultural soils of the Changjiang and Zhujiang deltas in China

Soils can often be contaminated simultaneously by more than one heavy metal. The sorption-desorption behavior of a metal in a soil will be affected by the presence of other metals. Therefore, selective retention and competitive adsorption of the soils to heavy metals can affect their availability and movement through the soils. In this study, the simultaneous competitive adsorption of four heavy metals (Cd, Cu, Hg, and Pb) on ten agricultural soils collected from the Changjiang and Zhujiang deltas, China was assessed. The results showed that the competition affected the behavior of heavy metal cations in such a way that the soils adsorbed less Cd and Hg, and more Pb and Cu with increasing total metal concentrations, regardless of the molar concen- tration applied. As the applied concentrations increased, Pb and Cu adsorption increased, while Cd and Hg adsorption decreased. The adsorption sequence most found was Pb>Cu>Hg>Cd. The maximum adsorption capacity for the heavy metal cations was calculated, and affected markedly by soil properties. The results suggest that Hg and Cd have higher mobility associated to the lower adsorption and that Pb and Cu present the opposite behavior. Significant correlations were found between the maximum adsorption capacity of the metals and pH value and exchangeable acid, suggesting that soil pH and exchangeable acid were key factors controlling the solubility and mobility of the metals in the agricultural soils.