Copper uptake by Elsholtzia splendens and Silene vulgaris and assessment of copper phytoavailability in contaminated soils

Tolerance and metal uptake are two essential characteristics required for phytoextraction of metals from contaminated soils. We compared tolerance and Cu uptake of Elsholtzia splendens (reported previously to be a Cu hyperaccumulator) with Silene vulgaris (the Imsbach population, a well-known Cu-tolerant excluder species), using 30 soils varying widely in total Cu concentration (19-8645 mg kg(-1)). We further investigated the effectiveness of different soil testing methods for predicting plant metal uptake. The results showed that both Elsholtzia splendens and Silene vulgaris were tolerant to Cu, especially Silene vulgaris. However, Elsholtzia splendens did not hyperaccumulate Cu, but behaved as a typical Cu excluder like Silene vulgaris. The concentrations of Cu in both plants correlated more closely with 1 M NH4NO3 extractable Cu, soil solution Cu, or effective Cu concentration determined using DGT, than with soil total Cu, EDTA extractable Cu or free Cu2+ activity. The relationships between soil solution properties and root Cu concentrations were further investigated using multiple regression. The results showed that increasing soil solution pH increased root Cu concentration when free Cu2+ activity was held constant, suggesting a higher phytoavailability of free Cu2+ at a higher pH. Soil solution DOC appeared to play two contrasting roles on the phytoavailability of Cu: (1) reducing Cu availability by complexing Cu; and (2) increasing Cu availability at the same level of free Cu2+ activity by providing a strong buffer for free Cu2+. The results are consistent with the intensity/capacity concept for phytoavailability of metals in soils.     

Sorption of copper and nickel by spent animal bones

Animal bone is able to adsorb copper and nickel ions from their single aqueous solutions. It was noted that a decrease in the sorbent concentration with constant copper or nickel concentration, or an increase in the copper or nickel concentration with a constant sorbent concentration resulted in a higher metal loading per unit weight of the sorbent. Increase in the initial pH of the metal solution resulted in an increase in the metals uptake per unit weight of the sorbent. Freundlich isotherm model was found to be applicable for the experimental data of Cu2+ and Ni2+. The results showed that animals bones can be used for the adsorption of the Cu2+ and Ni2+ with higher affinity toward Cu2+ ions. The new sorbent was able to decrease copper concentration to a limit lower than the limit permitted by the environmental regulations.     

Modelling the extra and intracellular uptake and discharge of heavy metals in Fontinalis antipyretica transplanted along a heavy metal and pH contamination gradient

Samples of the aquatic bryophyte Fontinalis antipyretica Hedw. were transplanted to different sites with the aim of characterizing the kinetics of the uptake and discharge of heavy metals in the extra and intracellular compartments. The accumulation of metals in extracellular compartments, characterized by an initial rapid accumulation, then a gradual slowing down over time, fitted perfectly to a Michaelis-Menten model. The discharge of metals from the same compartment followed an inverse linear model or an inverse Michaelis-Menten model, depending on the metal. In intracellular sites both uptake and discharge occurred more slowly and progressively, following a linear model. We also observed that the acidity of the environment greatly affected metal accumulation in extracellular sites, even when the metals were present at relatively high concentrations, whereas the uptake of metals within cells was much less affected by pH.     

Euglena gracilis as a model for the study of Cu2+ and Zn2+ toxicity and accumulation in eukaryotic cells

We have observed the effect of copper and zinc on the biology of Euglena gracilis. The cells displayed different sensitivities to these metals, as the apparent LC50 for Cu2+ was 0.22 mM, and for Zn2+ it was 0.88 mM. While Zn2+ was able to increase cell proliferation even at 0.1 mM, the minimal CuCl2 concentration tested (0.02 mM) was sufficient to impair cell division. Higher concentrations of these metals not only inhibited cell division in a concentration-dependent manner, but also interfered with the metabolism of E. gracilis. A higher accumulation of proteins and lipids per cell was observed at the DI50 concentration for metal-treated cells. These results suggest that the test concentration of both metals leads to a failure in completing cell division. Ultrastructural analysis indicated a chloroplast disorganization in copper-treated cells, as well as the presence of electron dense granules with different shapes and sizes inside vacuoles. Microanalysis of these granules indicated an accumulation of copper, thus suggesting a detoxification role played by the vacuoles. These results indicate that E. gracilis is an efficient biological model for the study of metal poisoning in eukaryotic cells. They also indicate that copper and zinc (copper being more poisonous) had an overall toxic effect on E. gracilis and that part of the effect can be ascribed to defects in the structure of chloroplast membranes.     

改性γ-聚谷氨酸络合重金属离子性能

研究了不同控制条件(温度、Pb2+浓度、pH)对交联改性γ-聚合谷氨酸(γ-PGA)吸附重金属离子所形成的絮凝颗粒性质的影响,对于治理水中重金属污染的相关研究有一定参考价值。实验表明,C-L-γ-PGA絮凝吸附Pb2+的最佳温度段在30℃附近。随着交联度的增加,不同的Pb2+浓度影响絮凝颗粒的大小,当处于较低浓度时,静电引力成为影响絮凝颗粒粒径最主要的因素,当Pb2+浓度增加到一定程度时,重金属的吸附量成为絮凝颗粒的粒径的决定因素。溶液pH达到7附近时,能够形成粒径最大的絮凝颗粒,并出现了最大的Pb2+去除率。C-L-γ-PGA对其他重金属离子也有类似的吸附絮凝作用,且絮凝吸附强弱顺序为Cu2+>Cr3+>Pb2+>Hg2+。吸附絮凝颗粒的粒径反映了重金属被吸附之后分离的难易程度,因此研究不同条件对絮凝颗粒粒径的影响对重金属离子的吸附和去除有重要意义。     

Biokinetics of cadmium, selenium, and zinc in freshwater alga Scenedesmus obliquus under different phosphorus and nitrogen conditions and metal transfer to Daphnia magna

The uptake of Cd, Se(IV) and Zn by the freshwater alga Scenedesmus obliquus and the subsequent transfer and release budget in Daphnia magna were investigated under different nutrient additions and cell incubation conditions. An increase in ambient phosphate concentrations from 0.5 micromol l(-1) to 50 micromol l(-1) significantly increased the intracellular accumulation of Cd (by 18x) and Zn (by 5x), but decreased the accumulation of Se (by 126x) in the alga. The percentage of these metals distributing in the intracellular pool of algae also increased substantially with increasing ambient P concentrations. Nitrate addition from 5.0 to 200 micromol l(-1) did not influence the uptake of any of the three metals, although a significant decrease in the intracellular Se distribution was observed. Radiolabeled algae under different nutrient manipulations (semi-continuous culture, starvation, and P-pulse treatments) were used to measure trophic transfer assimilation efficiency (AE) in Daphnia. When the algal cells were grown in a semi-continuous culture, starved for N and P, or were treated with P-pulse, the AEs of Cd and Zn were generally independent of the nutritional conditions, but the Se AE was significantly affected by different P levels. The efflux rate constants, determined during 10 d depuration following 7 days of dietary uptake, decreased significantly for Cd and Zn, but were relatively constant for Se with increasing P concentration. N-addition caused no effect on the metal efflux rate constants. P- or N-additions did not influence the release budget (including molting, neonates, excretion and feces) for all three elements in Daphnia. Our study indicated that phosphate enrichment may substantially increase metal uptake in green alga S. obliquus. Responses of trophic transfer in Daphnia to nutrient enrichment were metal specific. P-enrichment can possibly lead to considerable decrease on Se transfer from algae to zooplankton.     

Spatial and seasonal variation in heavy metals in interstitial water of salt marsh soils

The composition of interstitial water collected from a salt marsh in NW Spain showed clear seasonal and spatial variations associated with redox cycles of Fe and S. In the summer, salinity increased in all soils as a consequence of the increase in evapotranspiration. The pH and concentrations of heavy metals also differed with season, but not all environments showed the same variations. Soils not colonized by plants had the highest pH and lowest heavy metal concentrations in the summer. These results support the idea that higher temperatures lead to an increase in the activity of sulfate-reducing bacteria, which in turn leads to an increase in alkalinity and concentration of sulfides in the water. Trace metals tend to precipitate with sulfides under these conditions and are removed from the interstitial water. In contrast, in the soils colonized by Spartina maritima, the oxidation of metal sulfides during the summer led to a decrease in pH and an increase in the metal concentrations in the interstitial water. The results obtained concur with those found for seasonal variations in metal sulfides in soils from the same salt marsh.     

Effects of Sphagnum moss and urban runoff on bioavailability of lead and zinc from acidic wetlands of the New Jersey pinelands

The effects of Sphagnum and urban runoff on the bioavailability of metals were tested by adding PbCl2 and ZnCl2 to laboratory microcosms constructed of peat substrate with or without live Sphagnum spp. and planted with Acer rubrum L. seedlings or Vaccinium macrocarpon Ait. shoots. We hypothesized that Sphagnum would increase bioavailability through its acidifying action, while urban runoff would decrease availability through increases in alkalinity. Metals were more available to the test plants treated with acidic swampwater than with alkaline runoff. Sphagnum moss caused increases in tissue concentrations in V. macrocarpon, but not in A. rubrum. The latter species took up more metals when grown on substrate from sites receiving runoff, whereas the former took up more metals from substrate from undisturbed sites, despite the lower substrate metal concentrations. Differences in uptake by the two species may reflect differences in their ability to root in the Sphagnum mat. The results demonstrate that Sphagnum spp. exerts strong species-specific effects on the uptake of metals by vascular plants, and that plant species native to acidic wetlands vary widely in their response to metals in the substrate.     

Impact of cadmium and nickel on ion homeostasis in the yeast Schizosaccharomyces pombe

Abstract

Toxicity of heavy metals to living organisms is a worldwide research topic. Although, much has been discovered about cadmium and nickel impact on biological systems, a lot still remains unclear. We used inductively coupled plasma – optical emission spectroscopy to address the question of the effect of two different heavy metals nickel, and cadmium on intracellular ion balance. Increase or decrease of the content of several essential cations including Ca²⁺, Na⁺, K⁺, Mg²⁺, Cu²⁺, Fe³⁺ in the yeast Schizosaccharomyces pombe was determined. Our results revealed that the cell exposure to high nickel and cadmium concentrations led to significant elevation of Ca²⁺, Na⁺, Mg²⁺, Cu²⁺, Fe³⁺ levels in the yeast cell, while the content of K⁺ decreased. Correlation analyses showing in the presence of nickel and cadmium strong positive correlation among each tested element (Ca²⁺, Na⁺, Cu²⁺, Mg²⁺ and Fe³⁺) except for K⁺, demonstrate the significant impact of heavy metal treatment to ion homeostasis of the cell. Our data indicate that acute nickel and cadmium contamination leads to substantial ionome misbalance in yeast.     

Removal of heavy metals from anaerobically digested sewage sludge by isolated indigenous iron-oxidizing bacteria

The removal of heavy metals (Cr, Cu, Zn, Ni and Pb) from anaerobically digested sludge from the Yuen Long wastewater treatment plant, Hong Kong, has been studied in a batch system using isolated indigenous iron-oxidizing bacteria. The inoculation of indigenous iron-oxidizing bacteria and the addition of FeSO4 accelerated the solubilization of Cr, Cu, Zn, Ni and Pb from the sludge. pH of the sludge decreased with an increase in Fe2+ concentrations and reached a low pH of 2-2.5 for treatments receiving both bacterial inoculation and FeSO4. After 16 days of bioleaching, the following heavy metal removal efficiencies were obtained: Cr 55.3%, Cu 91.5%, Zn 83.3%, Ni 54.4%, and Pb 16.2%. In contrast, only 2.6% of Cr, 42.9% of Cu, 72.1% of Zn, 22.8% of Ni and 0.56% of Pb were extracted from the control without the bacterial inoculation and addition of FeSO4. The residual heavy metal content in the leached sludge was acceptable for unrestricted use for agriculture. The experimental results confirmed the effectiveness of using the isolated iron-oxidizing bacteria for the removal of heavy metals from sewage sludge.     

Copper and zinc induction of lipid peroxidation and effects on antioxidant enzyme activities in the microalga Pavlova viridis (Prymnesiophyceae)

The metal-induced lipid peroxidation and response of antioxidative enzymes have been investigated in the marine microalga Pavlova viridis to understand the mechanisms of metal resistance in algal cells. We have analyzed superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) activities and glutathione (GSH) contents in microalgal cells grown at different concentrations of copper and zinc. In response to each metal, lipid peroxidation was enhanced with the increase of concentrations, as an indication of the oxidative damage caused by metal concentration assayed in the microalgae cells. Exposure of P. viridis to the two metals caused changes in enzyme activities in a different manner, depending on the metal assayed: after copper treatments, total SOD activity was enhanced, while it was reduced after zinc exposure. Copper and zinc stimulated the activities of CAT and GSH whereas GPX showed a remarkable increase in activity in response to copper treatments and decrease after zinc treatments. These results suggest that an activation of some antioxidant enzymes was enhanced to counteract the oxidative stress induced by the two metals.     

石灰干化污泥对土壤重金属稳定化处理的效果

以采自湖南省嘉禾县重金属复合污染土壤为研究对象,采用城市污水处理石灰干化污泥作为稳定剂,对污染土壤进行稳定化处理,并采用TCLP和BCR连续提取法对稳定化效果进行分析和评价。研究结果表明,单独使用石灰干化污泥,TCLP浸出浓度随着干化污泥质量分数的增加而显著减少,干化污泥的质量分数为40%时,稳定化率最大为Zn-98.92%、Cd-99.06%、Pb-96.84%;但是干化污泥的高pH值导致稳定后土壤中As的浸出增加。为了恢复植物生长功能,经过亚铁盐和磷酸调节pH后,石灰干化污泥稳定过的土壤pH有效降低,同时亚铁盐和磷酸有利于促进Pb和Zn的稳定效果;但是对Cd的稳定有负面影响;另外,亚铁盐的加入同时可以减少As的浸出浓度。经处理后土壤中重金属形态由不稳定态转为稳定态,使重金属的浸出浓度明显降低,减少了土壤重金属的浸出毒性。该研究结果表明,石灰干化污泥可以作为资源回收利用,应用于重金属污染土壤的修复中,并能改善稳定后土壤适宜植物生长的理化性质。     

Euglena gracilis as a model for the study of Cu and Zn toxicity and accumulation in eukaryotic cells

We have observed the effect of copper and zinc on the biology of Euglena gracilis. The cells displayed different sensitivities to these metals, as the apparent LC₅₀ for Cu²⁺ was 0.22 mM, and for Zn²⁺ it was 0.88 mM. While Zn²⁺ was able to increase cell proliferation even at 0.1 mM, the minimal CuCl₂ concentration tested (0.02 mM) was sufficient to impair cell division. Higher concentrations of these metals not only inhibited cell division in a concentration-dependent manner, but also interfered with the metabolism of E. gracilis. A higher accumulation of proteins and lipids per cell was observed at the DI₅₀ concentration for metal-treated cells. These results suggest that the test concentration of both metals leads to a failure in completing cell division. Ultrastructural analysis indicated a chloroplast disorganization in copper-treated cells, as well as the presence of electron dense granules with different shapes and sizes inside vacuoles. Microanalysis of these granules indicated an accumulation of copper, thus suggesting a detoxification role played by the vacuoles. These results indicate that E. gracilis is an efficient biological model for the study of metal poisoning in eukaryotic cells. They also indicate that copper and zinc (copper being more poisonous) had an overall toxic effect on E. gracilis and that part of the effect can be ascribed to defects in the structure of chloroplast membranes.     

淀粉基黄原酸盐处理重金属废水的条件优化研究

采用淀粉基黄原酸盐处理含重金属的电镀废水 ,对淀粉基黄原酸盐的用量、pH值和反应时间等条件进行了研究。结果发现 ,1L含氰电镀废水 (含Cr3+15mg/L、Cu2 +3mg/L、Ni2 +9.2mg/L和Zn2 +6mg/L) ,加入 1g淀粉基黄原酸盐 ,调节 pH为 8,搅拌 1h ,过滤 ,处理后的废水中Cr3+、Cu2 +、Zn2 +和Ni2 +残余浓度分别为 0 .0 8mg/L、0 .0 1mg/L、0 .1mg/L和 0 .0 8mg/L。含有重金属盐的残渣 ,可用硝酸处理 ,以回收重金属     

Quantitative assessment of the toxic effects of heavy metals on 1,2-dichloroethane biodegradation in co-contaminated soil under aerobic condition

1,2-Dichloroethane (1,2-DCA) is one of the most hazardous pollutant of soil and groundwater, and is produced in excess of 5.44 × 10⁹ kg annually. Owing to their toxicity, persistence and potential for bioaccumulation, there is a growing interest in technologies for their removal. Heavy metals are known to be toxic to soil microorganisms at high concentrations and can hinder the biodegradation of organic contaminants. In this study, the inhibitory effect of heavy metals, namely; arsenic, cadmium, mercury and lead, on the aerobic biodegradation of 1,2-DCA by autochthonous microorganisms was evaluated in soil microcosm setting. The presence of heavy metals was observed to have a negative impact on the biodegradation of 1,2-DCA in both soil samples tested, with the toxic effect being more pronounced in loam soil, than in clay soil. Generally, 75 ppm As³⁺, 840 ppm Hg²⁺, and 420 ppm Pb²⁺ resulted in 34.24%, 40.64%, and 45.94% increase in the half live (t_½) of 1,2-DCA, respectively, in loam soil, while concentrations above 127.5 ppm Cd²⁺, 840 ppm Hg²⁺ and 420 ppm of Pb²⁺ and less than 75 ppm As³⁺ was required to cause a >10% increase in the t_½ of 1,2-DCA in clay soil. A dose-dependent relationship between degradation rate constant (k₁) of 1,2-DCA and metal ion concentrations was observed for all the heavy metals tested, except for Hg²⁺. This study demonstrated that different heavy metals have different impacts on the degree of 1,2-DCA degradation. Results also suggest that the degree of inhibition is metal specific and is also dependent on several factors including; soil type, pH, moisture content and available nutrients.     

Sequential extraction of heavy metals during composting of sewage sludge

The major limitation of soil application of sewage sludge compost is the total heavy metal contents and their bioavailability to the soil-plant system. This study was conducted to determine the heavy metal speciation and the influence of changing the physico-chemical properties of the medium in the course of composting on the concentrations, bioavailability or chemical forms of Cu, Zn, Pb and Ni in sewage sludge. Principal physical and chemical properties and FTIR spectroscopical characterization of sludge compost during treatment show the stability and maturity of end product. The total metal contents in the final compost were much lower than the limit values of composts to be used as good soil fertilizer. Furthermore, it was observed by using a sequential extraction procedure in sludge compost at different steps of treatment, that a large proportion of the heavy metals were associated to the residual fraction (70-80%) and more resistant fractions to extraction X-NaOH, X-EDTA, X-HNO3 (12-29%). Less than 2% of metals bound to bioavailable fractions X-(KNO3+H2O). Heavy metal distribution and bioavailability show some changes during composting depending on the metal itself and the physico-chemical properties of the medium. Bioavailable fractions of all elements tend to decrease except Ni-H2O. Zn and mainly Cu present more affinity to organic and carbonate fractions. In contrast, Pb is usually preferentially bound to sulfide forms X-HNO3. Nickel shows a significant decrease of organic form. Significant degrees of correlation were found between heavy metal fractions and changes of some selected variables (e.g. pH, ash, organic matter, humic substance) during the course of composting. Mobile fractions of metals are poorly predictable from the total content. The R2 value was significantly increased by the inclusion of other variables such as the amount of organic matter (OM) and pH.     

Natural organic matter (NOM) in roof runoff and its impact on the Fe0 treatment system of dissolved metals

The present work investigates the impacts and mechanisms associated with natural organic matter (NOM) in the Fe0 treatment system of Cu2+ and Zn2+ under roof runoff conditions. The NOM in runoff waters was characterized using XAD-4/8 adsorption resins, copper complexation, acidic capacity and liquid chromatography with online carbon detection. Batch kinetic experiments and flow-through configurations were performed and the results of metal removal were elucidated taking into account the characteristics of NOM. Based on the findings, it is shown that NOM influences the removal of metals through several complex pathways. At an un-favored condition for adsorption of metals, i.e., on iron corrosion products, at pH相似文献   

Enhancement of phenanthrene adsorption on a clayey soil and clay minerals by coexisting lead or cadmium

Phenanthrene is commonly present together with heavy metals at many contaminated sites. This study investigated the influence of coexisting lead (Pb²⁺) or cadmium (Cd²⁺) on phenanthrene adsorption on soils. Batch experiments were conducted under different geochemical conditions including pH, mineral structure, organic matter content, and varying amounts of heavy metals. The results showed that the presence of heavy metals in solution at a fixed pH of 5.8 ± 0.1 enhanced phenanthrene adsorption, the extent of which was closely related to the concentrations and the electro-negativity of the metals. The enhancement on phenanthrene adsorption was positively correlated to the amount of adsorbed metals. Although Cd²⁺ is a softer Lewis acid, Pb²⁺ displayed a more significant effect as it was adsorbed to a greater extent on the soil surfaces. Thus, density of cation accumulation appears to be more influential than metal softness in enhancing phenanthrene adsorption. Moreover, with a portion of organic matter removed by heating at 550 °C, there was a stronger enhancement of phenanthrene adsorption by coexisting Pb²⁺, indicating an increasingly dominant mechanisms associated with Pb²⁺ at a lower organic matter content. Similar enhancement phenomenon was observed on bentonite and kaolinite, probably resulting from the cation-π bonding between the adsorbed soft metal cations and the aromatic ring of phenanthrene in solution. The desorption experiments further suggested that the bonding of phenanthrene adsorption was strengthened in the presence of Pb²⁺ and that a larger proportion of adsorbed phenanthrene remained on the soils (residual fraction) even after sequential methanol extractions. Further spectroscopic analyses and surface characterization are required to provide direct evidence of the formation and relative significance of cation-π bond for phenanthrene adsorption.     

微生物沥浸法去除底泥中的重金属

以硫酸亚铁盐为底物,培养以氧化亚铁硫杆菌为主要菌种的土著沥滤微生物,采用批式方法对湘江长沙段底泥进行微生物沥浸实验。实验结果表明,底物投加量与底泥固体浓度比(Sd/Sc)为1.5时已能满足底泥的微生物沥浸要求,进一步研究发现底泥固体浓度为13%、底物投加量为19.5 g/L、沥浸时间为6 d时,底泥中超标重金属Cd、Zn和Cu的去除率可分别达到83.1%、75.3%和61.2%;沥浸后底泥中大部分重金属以残渣态存在,且含量低于农用污泥中污染物控制标准,其中硫化物有机结合态Cu浸出较Zn、Cd需更低的pH,且Cu以间接机理浸出为主;以Fe2+为底物的沥浸体系中,黄铁矾的重吸附或共沉淀是沥浸实验后期重金属浸出率下降的原因之一。     

Cornmeal-induced resistance to ciprofloxacin and erythromycin in enterococci

Triclosan is used as an antibacterial agent in household items and personal care products. Since this compound is found in maternal milk of humans and bodies of wild animals, there is growing concern among some consumer groups and scientific community that triclosan is adverse for humans and wild animals. In order to estimate adverse actions of triclosan, the effects of triclosan on intracellular Zn²⁺ concentration and cellular thiol content were studied in rat thymocytes by the use of flow cytometer with appropriate fluorescent probes. Triclosan at 1-3 μM (sublethal concentrations) increased the intensity of FluoZin-3 fluorescence (intracellular Zn²⁺ concentration) and decreased the intensity of 5-chloromethylfluorescein (5-CMF) fluorescence (cellular thiol content). Negative correlation (r = −0.985) between triclosan-induced changes in FluoZin-3 and 5-CMF fluorescences was found. Removal of external Zn²⁺ did not significantly affect the triclosan-induced augmentation of FluoZin-3 fluorescence, suggesting an intracellular Zn²⁺ release by triclosan. These actions of triclosan were similar to those of H₂O₂ and triclosan significantly potentiated the cytotoxicity of H₂O₂. Therefore, the results may suggest that triclosan at sublethal concentrations induces oxidative stress that decreases cellular thiol content, resulting in an increase in intracellular Zn²⁺ concentration by Zn²⁺ release from intracellular store(s). Since recent studies show many physiological roles of intracellular Zn²⁺ in cellular functions, the triclosan-induced disturbance of cellular Zn²⁺ homeostasis may induce adverse actions on the cells.