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Sample records for pb cd zn

  1. Pb and Zn accumulation in a Cd-hyperaccumulator (Viola baoshanensis).

    PubMed

    Wu, Chuan; Liao, Bin; Wang, Sheng-Long; Zhang, Jun; Li, Jin-Tian

    2010-08-01

    Viola baoshanensis has been identified as a Cd-hyperaccumulator, however, its ability to accumulate Pb or Zn is less certain. Therefore, this study focused on determining whether or not V. baoshanensis can accumulate Pb or Zn, by means of field survey, hydroponic and pot experiments. In addition, we also tried to obtain further information on the Cd hyperaccumulating characteristics of this species. Under field conditions, V. baoshanensis accumulated on average 1090 mg Cd kg(-1), 1902 mg Pb kg(-1) and 3428 mg Zn kg(-1) in its shoots, respectively. In hydroponic and pot experiments, V. baoshanensis showed high tolerance to Cd, Pb, and Zn, as well as the ability to accumulate exceptionally high concentrations of the three elements in its shoots (> 2% Cd, > 1% Pb, and > 0.5% Zn on a dry matter basis). These results, taken together, suggested that V. baoshanensis is not only a Cd-hyperaccumulator, but also a strong accumulator of Pb and Zn. PMID:21166282

  2. Accumulation of Cd, Pb and Zn by 19 wetland plant species in constructed wetland.

    PubMed

    Liu, Jianguo; Dong, Yuan; Xu, Hai; Wang, Deke; Xu, Jiakuan

    2007-08-25

    Uptake and distribution of Cd, Pb and Zn by 19 wetland plant species were investigated with experiments in small-scale plot constructed wetlands, into which artificial wastewater dosed with Cd, Pb and Zn at concentrations of 0.5, 2.0 and 5.0mgl(-1) was irrigated. The results showed that the removal efficiency of Cd, Pb and Zn from the wastewater were more than 90%. Generally, there were tens differences among the 19 plant species in the concentrations and quantity accumulations of the heavy metals in aboveground part, underground part and whole plants. The distribution ratios into aboveground parts for the metals absorbed by plants varied also largely from about 30% to about 90%. All the plants accumulated, in one harvest, 19.85% of Cd, 22.55% of Pb and 23.75% of Zn that were added into the wastewater. Four plant species, e.g. Alternanthera philoxeroides, Zizania latifolia, Echinochloa crus-galli and Polygonum hydropiper, accumulated high amounts of Cd, Pb and Zn. Monochoria vaginalis was capable for accumulating Cd and Pb, Isachne globosa for Cd and Zn, and Digitaria sanguinalis and Fimbristylis miliacea for Zn. The results indicated that the plants, in constructed wetland for the treatment of wastewater polluted by heavy metals, can play important roles for removal of heavy metals through phytoextraction. Selection of plant species for use in constructed wetland will influence considerably removal efficiency and the function duration of the wetland. PMID:17353090

  3. Bioleaching mechanism of Zn, Pb, In, Ag, Cd and As from Pb/Zn smelting slag by autotrophic bacteria.

    PubMed

    Wang, Jia; Huang, Qifei; Li, Ting; Xin, Baoping; Chen, Shi; Guo, Xingming; Liu, Changhao; Li, Yuping

    2015-08-15

    A few studies have focused on release of valuable/toxic metals from Pb/Zn smelting slag by heterotrophic bioleaching using expensive yeast extract as an energy source. The high leaching cost greatly limits the practical potential of the method. In this work, autotrophic bioleaching using cheap sulfur or/and pyrite as energy matter was firstly applied to tackle the smelting slag and the bioleaching mechanisms were explained. The results indicated autotrophic bioleaching can solubilize valuable/toxic metals from slag, yielding maximum extraction efficiencies of 90% for Zn, 86% for Cd and 71% for In, although the extraction efficiencies of Pb, As and Ag were poor. The bioleaching performance of Zn, Cd and Pb was independent of leaching system, and leaching mechanism was acid dissolution. A maximum efficiency of 25% for As was achieved by acid dissolution in sulfursulfur oxidizing bacteria (S-SOB), but the formation of FeAsO4 reduced extraction efficiency in mixed energy source - mixed culture (MS-MC). Combined works of acid dissolution and Fe(3+) oxidation in MS-MC was responsible for the highest extraction efficiency of 71% for In. Ag was present in the slag as refractory AgPb4(AsO4)3 and AgFe2S3, so extraction did not occur. PMID:25996622

  4. Removal, redistribution, and potential risks of soil Cd, Pb, and Zn after washing with various extractants.

    PubMed

    Chen, Chunle; Chen, Yanhui; Xie, Tuanhui; Wang, Ming Kuang; Wang, Guo

    2015-11-01

    The effectiveness of four different washing extractants--HCl, FeCl3, citric acid, and EDTA--in removing Cd, Pb, and Zn from polluted soil was studied. The removal of these metals, their redistribution between fractions, and the potential risks posed by them, in soils washed with the tested extractants, were examined. Although all the rounds of washing removed Cd, Pb, and Zn from soil, the first round removed more metals than subsequent rounds. Each of the four extractants had different effects on the removal of the metals. At the end of the first round of washing, HCl, EDTA, and FeCl3 were the most effective in removing Zn, Pb, and Cd, respectively. Both the single round and five successive rounds of washing with various extractants resulted in significant increases in Pb in the exchangeable/acid extractable fraction. Washing with HCl, EDTA, and FeCl3 significantly reduced potential risks (calculated as the Potential Risk Index, PRI) posed by Cd in washed soil. The first round of washing, using all extractants, increased the risks posed by Pb and Zn. However, five successive rounds of washing with FeCl3 and EDTA reduced the risk posed by Pb, and washing with citric acid and FeCl3 increased the risks posed by Zn. EDTA and HCl were better for reducing Zn risks, and successive washing with EDTA and FeCl3 were more effective in reducing Pb risks than the other extractants. Finally, five successive rounds of washing, with all the extractants, effectively reduced the potential risks posed by Cd. Among the four reagents, EDTA was advised to be the alternative of the washing reagent by significantly reducing the PRI values of Cd, Pb, and Zn. PMID:26104899

  5. Simultaneous Incorporation of Cr, Zn, Cd, and Pb in the Goethite Structure

    SciTech Connect

    Kaur, Navdeep; Gräfe, Markus; Singh, Balwant; Kennedy, Brendan

    2009-10-21

    In order to improve our understanding of how the goethite crystal structure is affected by the incorporation of metals (and by variations in the amount of the incorporation), and to review any possible synergistic and antagonistic effects of co-metals, the present investigation focused on the incorporation of multiple (di-, tri-, and tetra-) metals, i.e. Cr, Zn, Cd, and Pb, in the goethite crystallographic structure. A series of single- and multi-metal M-Cr/Zn/Cd/Pb-substituted goethites with M/(M+Fe) molar ratios = 0.10 were prepared. The general sequence of metal entry in single-metal substituted goethites was Zn = Cr > Cd > Pb and in multi-metal-substituted goethites was Zn > Cr {ge} Cd > Pb. Simultaneous incorporation of Cr, Zn, Cd, and Pb up to 10.5 mole % was achieved in goethite. Synchrotron X-ray diffraction and extended X-ray absorption fine structure (EXAFS) techniques were employed to assess the structural characteristics of the synthesis products. Rietveld refinement of XRD data showed small changes in unit-cell parameters and Fe/M-Fe/M distances due to M substitution(s). A typical goethite-like crystalline structure remained intact, however. The unit-cell parameters were mutually, linearly correlated, though Fe/M-Fe/M distances were not, indicating that complex changes occurred at the local scale. In single-metal substituted goethites, incorporation of Cr reduced the unit-cell volume by 0.13% while that of Zn, Cd, and Pb increased it by 1.09, 3.58, and 0.56%, respectively. The changes in multi-metal-substituted goethites appeared to be the complex combination of that of the individually incorporated metals. The X-ray absorption near edge structure study of Pb-substituted goethites showed that the majority of associated Pb was Pb{sup 2+}, while Pb{sup 4+} was preferred over Pb{sup 2+} in the bulk structure. Measurements by EXAFS at the Fe K-edge indicated that the Fe polyhedra contracted in the presence of Cd{sup 2+} and Pb{sup 2+}, providing room for

  6. Accumulation of Pb, Cd, Cu and Zn in plants and hyperaccumulator choice in Lanping lead-zinc mine area, China.

    PubMed

    Yanqun, Zu; Yuan, Li; Schvartz, Christian; Langlade, Laurent; Fan, Liu

    2004-06-01

    A field survey of higher terrestrial plants growing on Lanping lead-zinc mine, China were conducted to identify species accumulating exceptionally large concentrations of Pb, Cd, Cu and Zn of 20 samples of 17 plant species. Concentrations of Pb and Zn in soil and in plant were higher than that of Cu and Cd. Significant difference was observed among the average concentrations of four heavy metals in plants (except Cd and Cu) and in soil (except Pb and Zn) (P<0.05). For the enrichment coefficient of the four heavy metals in plant, the order of average was Pb. Between four heavy metals, only significant difference was observed between the enrichment coefficient average of Cd and Cu (P<0.05). The enrichment coefficients were higher than 1 in Llex plyneura and Rhododendron annae in Paomaping for Pb, Salix cathayana, L. plyneura and R. annae in Paomaping for Cd, and R. annae in Paomaping for Zn, respectively. Concentrations and enrichment coefficient of Pb, Cd and Zn of Rhododendron were higher than that of Gramimeae. Enrichment coefficient of Pb, Cd and Zn were bush>tree>herbaceous, and herbaceous grew in soil with the highest concentrations of four heavy metals. In different areas, the concentrations of Pb, Cd, Cu and Zn in plants and soils and enrichment coefficient were different. Plants in Paomaping had more accumulating ability to Pb, Cd and Zn, and plants in Jinfeng River had more accumulating ability to Cu. Six plant species, i.e. S. cathayana, Lithocarpus dealbatus, L. plyneura, Fargesia dura, Arundinella yunnanensis and R. annae in Paomaping, had high accumulation capacity. R. annae in Paomaping had hyperaccumulating capacity to Pb, Cd and Zn, L. plyneura to Pb and Cd, and S. cathayana to Cd, respectively. PMID:15031017

  7. Concentrations of Cd, Pb, Mn and Zn in feathers and diet in heron chicks in Korea.

    PubMed

    Kim, Jungsoo; Oh, Jong-Min

    2015-01-01

    The feathers and diet items of grey heron (Ardea cinerea) and black-crowned night-heron (Nycticorax nycticorax) chicks were collected at the Pyeongtaek colony, Korea in 2002 and 2008, and Cd, Pb, Mn and Zn concentrations were measured. Cd and Zn concentrations were higher in both species in 2008 than 2002 and were higher in grey herons than black-crowned night-herons in 2002. In 2008, Cd concentrations were higher in black-crowned night-herons than grey herons; Zn concentrations did not differ between species. Pb and Mn concentrations did not differ between species; however, there were yearly differences. Cd, Pb and Zn concentrations of feathers and diet were significantly correlated when species and years were combined. However, the predictive power of these relationships was limited because of species and yearly differences. All heron chicks had concentrations of Cd (<2 μg/g dw) and Pb (<4 μg/g dw) consistent with background concentrations for wild birds. Mn and Zn concentrations were within the range reported for other heron and egret species. PMID:25398268

  8. [Leaching behavior of Pb, Cd and Zn from soil stabilized by lime stabilized sludge].

    PubMed

    Li, Xiang; Song, Yun; Liu, Yong-Bing

    2014-05-01

    Stabilization of Pb, Cd and Zn spiked soil by using lime-stabilized sewage sludge( LSS) as amendment was investigated in this study, and the effectiveness was evaluated by using leaching tests ( TCLP, SPLP and de-ionized water) and modified BCR sequential extraction procedure. The results of TCLP indicated that the concentrations of heavy metals in TCLP leachate reduced significantly with the increase of the mass percentage of the LSS and the leaching reduction rates were as high as 99. 54% for Zn, 99. 60% for Pb, 99. 85% for Cd at 40% of LSS addition. When evaluated by SPLP and de-ionized water leaching method, the concentrations of Zn and Pb in leachate decreased obviously at 10% and 20% of LSS additions, but subsequently increased at 30% and 40% because of redissolution of Zn and Pb at strong base condition. After pH value of LLS-stabilized soil was adjusted by ferrous sulfate and phosphoric acid for recovering soil plantation function, the pH value of the soil decreased effectively, in the meantime promoting the stabilization effectiveness of Pb and Zn. The BCR test revealed that compared with the spiked soil exchangeable proportion of Zn, Pb, Cd in the soil and the soils adjusted by ferrous sulfate obviously declined, which implied the migration for Pb, Cd and Zn of contaminated soil could be confined. This study results show that municipal LSS can be reused in the stabilization of heavy metal contaminated soils and physical and chemical properties of LLS-stabilized soil are improved for plantation. PMID:25055691

  9. Pollution, fractionation, and mobility of Pb, Cd, Cu, and Zn in garden and paddy soils from a Pb/Zn mining area.

    PubMed

    Lei, Ming; Zhang, Yong; Khan, Sardan; Qin, Pu-feng; Liao, Bo-han

    2010-09-01

    This study was conducted to investigate the pollution load index, fraction distributions, and mobility of Pb, Cd, Cu, and Zn in garden and paddy soils collected from a Pb/Zn mine in Chenzhou City, China. The samples were analyzed using Leleyter and Probst's sequential extraction procedures. Total metal concentrations including Pb, Cd, Cu, and Zn exceeded the maximum permissible limits for soils set by the Ministry of Environmental Protection of China, and the order of the pollution index was Cd > Zn > Pb > Cu, indicating that the soils from both sites seriously suffered from heavy metal pollution, especially Cd. The sums of metal fractions were in agreement with the total contents of heavy metals. However, there were significant differences in fraction distributions of heavy metals in garden and paddy soils. The residual fractions of heavy metals were the predominant form with 43.0% for Pb, 32.3% for Cd, 33.5% for Cu, and 44.2% for Zn in garden soil, while 51.6% for Pb, 40.4% for Cd, 40.3% for Cu, and 40.9% for Zn in paddy soil. Furthermore, the proportions of water-soluble and exchangeable fractions extracted by the selected analytical methods were the lowest among all fractions. On the basis of the speciation of heavy metals, the mobility factor values of heavy metals have the following order: Cd (25.2-19.8%) > Cu (22.6-6.3%) > Zn (9.6-6.0%) > Pb (6.7-2.5%) in both contaminated soils. PMID:19669583

  10. Behaviors of heavy metals (Cd, Cu, Ni, Pb and Zn) in soil amended with composts.

    PubMed

    Gusiatin, Zygmunt Mariusz; Kulikowska, Dorota

    2016-09-01

    This study investigated how amendment with sewage sludge compost of different maturation times (3, 6, 12 months) affected metal (Cd, Cu, Ni, Pb, Zn) bioavailability, fractionation and redistribution in highly contaminated sandy clay soil. Metal transformations during long-term soil stabilization (35 months) were determined. In the contaminated soil, Cd, Ni and Zn were predominately in the exchangeable and reducible fractions, Pb in the reducible fraction and Cu in the reducible, exchangeable and oxidizable fractions. All composts decreased the bioavailability of Cd, Ni and Zn for up to 24 months, which indicates that cyclic amendment with compost is necessary. The bioavailability of Pb and Cu was not affected by compost amendment. Based on the reduced partition index (IR), metal stability in amended soil after 35 months of stabilization was in the following order: Cu > Ni = Pb > Zn > Cd. All composts were more effective in decreasing Cd, Ni and Zn bioavailability than in redistributing the metals, and increasing Cu redistribution more than that of Pb. Thus, sewage sludge compost of as little as 3 months maturation can be used for cyclic amendment of multi-metal-contaminated soil. PMID:26853755

  11. Modelling atmospheric bulk deposition of Pb, Zn and Cd near a former Pb-Zn mine in West Greenland using transplanted Flavocetraria nivalis lichens.

    PubMed

    Søndergaard, Jens; Bach, Lis; Asmund, Gert

    2013-03-01

    Atmospheric deposition of lead (Pb), zinc (Zn) and cadmium (Cd) was investigated near the former Black Angel Pb-Zn mine in Maarmorilik, West Greenland during 2010-2011. Thalli of the lichen Flavocetraria nivalis were transplanted from an uncontaminated site into sites near the mine and collected the following year. At 20 of the total 21 sites, concentrations of Pb, Zn and Cd were significantly elevated in lichens after 1 year of transplantation compared to initial concentrations. Elevated concentrations were observed within a distance of approx. 20 km from the mining area. Concentrations decreased with increasing distance from the mine and the relation was well described using a power function with a negative exponent (r(2)=0.90; 0.83 and 0.83 for Pb; Zn and Cd). To examine the relation between metal concentrations/uptake in lichen transplants and atmospheric bulk deposition, 10 Bergerhoff dust samplers were placed near lichen transplants and samplers and lichens were collected after a 7-weeks exposure period. A significant linear correlation was observed between metal concentrations in lichen transplants and atmospheric bulk metal deposition (r(2)=0.94; 0.88 and 0.89 for Pb; Zn and Cd). Combining the results and including an area distribution within a defined metal deposition area, the "annual" deposition of Pb, Zn and Cd as dust was estimated during the 2010-2011 snow-free period (∼5 months). The results reveal that 20 years after mine closure, 770 kg Pb, 3700 kg Zn and 24 kg Cd were still being deposited as dust per year (snow-free period only) within a distance of 20 km from the mine. PMID:23211325

  12. Chemical behavior of Cu, Zn, Cd, and Pb in a eutrophic reservoir: speciation and complexation capacity.

    PubMed

    Tonietto, Alessandra Emanuele; Lombardi, Ana Teresa; Choueri, Rodrigo Brasil; Vieira, Armando Augusto Henriques

    2015-10-01

    This research aimed at evaluating cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) speciation in water samples as well as determining water quality parameters (alkalinity, chlorophyll a, chloride, conductivity, dissolved organic carbon, dissolved oxygen, inorganic carbon, nitrate, pH, total suspended solids, and water temperature) in a eutrophic reservoir. This was performed through calculation of free metal ions using the chemical equilibrium software MINEQL+ 4.61, determination of labile, dissolved, and total metal concentrations via differential pulse anodic stripping voltammetry, and determination of complexed metal by the difference between the total concentration of dissolved and labile metal. Additionally, ligand complexation capacities (CC), such as the strength of the association of metals-ligands (logK'ML) and ligand concentrations (C L) were calculated via Ruzic's linearization method. Water samples were taken in winter and summer, and the results showed that for total and dissolved metals, Zn > Cu > Pb > Cd concentration. In general, higher concentrations of Cu and Zn remained complexed with the dissolved fraction, while Pb was mostly complexed with particulate materials. Chemical equilibrium modeling (MINEQL+) showed that Zn(2+) and Cd(2+) dominated the labile species, while Cu and Pb were complexed with carbonates. Zinc was a unique metal for which a direct relation between dissolved species with labile and complexed forms was obtained. The CC for ligands indicated a higher C L for Cu, followed by Pb, Zn, and Cd in decreasing amounts. Nevertheless, the strength of the association of all metals and their respective ligands was similar. Factor analysis with principal component analysis as the extraction procedure confirmed seasonal effects on water quality parameters and metal speciation. Total, dissolved, and complexed Cu and total, dissolved, complexed, and labile Pb species were all higher in winter, whereas in summer, Zn was mostly present in the

  13. Assessing Pb,Zn,Cd contamination in stream sediments of south east Tehran (Iran)

    NASA Astrophysics Data System (ADS)

    Shahdadi, S.; Fayazi, F.; Yaghoobpour, A.; Rahmani, F.; Moslempour, M.

    2009-04-01

    Assessing Pb,Zn,Cd contamination in stream sediments of south east Tehran (Iran) 31 sediment samples collected from south east of Tehran around cement plant (Bibi shahrbanoo mountain) were analyzed by ICP for Pb, Zn, Cd. The samples were also investigated for mineralogy using X-ray analysis.The clay mineral assemblage encountered in the analyzed samples is composed of vermiculite, dickite, montmorillonite and kaolinite.The non-clay minerals of the mud-sized fraction are composed mainly of quartz and calcite and dolomite as major minerals with albite, hematite, muscovite as minor minerals. The measured metals correlated positively with the determined physiochemical factors such as pH, clay content, organic matter content, and carbonate content. According to the index of geoaccumulation, the sediments of the study area are considered to be strongly to very strongly polluted with respect to Pb, strongly polluted with respect to Zn, and moderatly to strongly polluted with recpect to Cd.The calculation of enrichment factors shows that the source of Pb and Zn is from antropogenic activites such as cement plant and vehicle exhausts and Cd from natural source.

  14. RESPONSE OF SOIL MICROBIOLOGICAL ACTIVITIES TO CD, PB, AND ZN SALT AMENDMENTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heavy metal pollution of soil has been recognized as a major factor impeding soil microbial processes. We studied responses of the soil biological activities to metal stress simulated by soil amendment with Zn, Pb and Cd chlorides. The amounts of heavy metal salts added to five metal polluted soils ...

  15. Concomitant Zn-Cd and Pb retention in a carbonated fluvio-glacial deposit under both static and dynamic conditions.

    PubMed

    Lassabatere, Laurent; Spadini, Lorenzo; Delolme, Cécile; Février, Laureline; Galvez Cloutier, Rosa; Winiarski, Thierry

    2007-11-01

    The chemical and physical processes involved in the retention of 10(-2)M Zn, Pb and Cd in a calcareous medium were studied under saturated dynamic (column) and static (batch) conditions. Retention in columns decreased in order: Pb>Cd approximately Zn. In the batch experiments, the same order was observed for a contact time of less than 40h and over, Pb>Cd>Zn. Stronger Pb retention is in accordance with the lower solubility of Pb carbonates. However, the equality of retained Zn and Cd does not fit the solubility constants of carbonated solids. SEM analysis revealed that heavy metals and calcareous particles are associated. Pb precipitated as individualized Zn-Cd-Ca- free carbonated crystallites. All the heavy metals were also found to be associated with calcareous particles, without any change in their porosity, pointing to a surface/lattice diffusion-controlled substitution process. Zn and Cd were always found in concomitancy, though Pb fixed separately at the particle circumferences. The Phreeqc 2.12 interactive code was used to model experimental data on the following basis: flow fractionation in the columns, precipitation of Pb as cerrusite linked to kinetically controlled calcite dissolution, and heavy metal sorption onto proton exchanging sites (presumably surface complexation onto a calcite surface). This model simulates exchanges of metals with surface protons, pH buffering and the prevention of early Zn and Cd precipitation. Both modeling and SEM analysis show a probable significant decrease of calcite dissolution along with its contamination with metals. PMID:17583773

  16. Role of Bound Zn(II) in the CadC Cd(II)/Pb(II)/Zn(II)-Responsive Repressor

    SciTech Connect

    Kandegedara, A.; Thiyagarajan, S; Kondapalli, K; Stemmler, T; Rosen, B

    2009-01-01

    The Staphylococcus aureus plasmid pI258 cadCA operon encodes a P-type ATPase, CadA, that confers resistance to Cd(II)/Pb(II)/Zn(II). Expression is regulated by CadC, a homodimeric repressor that dissociates from the cad operator/promoter upon binding of Cd(II), Pb(II), or Zn(II). CadC is a member of the ArsR/SmtB family of metalloregulatory proteins. The crystal structure of CadC shows two types of metal binding sites, termed Site 1 and Site 2, and the homodimer has two of each. Site 1 is the physiological inducer binding site. The two Site 2 metal binding sites are formed at the dimerization interface. Site 2 is not regulatory in CadC but is regulatory in the homologue SmtB. Here the role of each site was investigated by mutagenesis. Both sites bind either Cd(II) or Zn(II). However, Site 1 has higher affinity for Cd(II) over Zn(II), and Site 2 prefers Zn(II) over Cd(II). Site 2 is not required for either derepression or dimerization. The crystal structure of the wild type with bound Zn(II) and of a mutant lacking Site 2 was compared with the SmtB structure with and without bound Zn(II). We propose that an arginine residue allows for Zn(II) regulation in SmtB and, conversely, a glycine results in a lack of regulation by Zn(II) in CadC. We propose that a glycine residue was ancestral whether the repressor binds Zn(II) at a Site 2 like CadC or has no Site 2 like the paralogous ArsR and implies that acquisition of regulatory ability in SmtB was a more recent evolutionary event.

  17. Sources of Cu, Zn, Cd and Pb in rainwater at a subtropical islet offshore northern Taiwan

    NASA Astrophysics Data System (ADS)

    Cheng, Miao-Ching; You, Chen-Feng; Lin, Fei-Jan; Huang, Kuo-Fang; Chung, Chuan-Hsiung

    2011-02-01

    Pollutants derived from long-range transport and local emission impact significantly of heavy metal compositions in rainwater and aerosols. To identify their sources and relative contributions in rainwater, 47 monthly rainwater samples from January 1998 to December 2001, collected at Peng Chia Yu (PCY), a non-residential islet offshore Taiwan, were analyzed for heavy metals (i.e. Cu, Zn, Cd, and Pb) and Pb isotopic compositions. The dissolved metals concentrations of Al, Mn, Fe, Cu, Zn, Rb, Ba, and Pb in PCY rains are high in spring and winter, but low in summer. This can be understood in terms of pollutant source changes due to wind direction shifted seasonally. The average EF crust and EF seawater values calculated for Cu, Zn, Cd and Pb are far greater than 1500, suggesting their strong anthropogenic sources, also supported by the PCA results. The pollutants derived from long-range transport are the predominated heavy metals sources during the winter monsoon season, whereas local traffic emissions play the most important role during the summer monsoon period. Unique Pb isotopic fingerprints, similar to those of iron ore sinter dusts and oil combustion dusts from Shanghai and the traffic emissions from Taiwan were identified in PCY rainwater. A mixing model based on three typical end-member Pb isotopic compositions derived from Taiwan and China was applied to evaluate the pollutant sources variations.

  18. Biosorption of divalent Pb, Cd and Zn on aragonite and calcite mollusk shells.

    PubMed

    Du, Yang; Lian, Fei; Zhu, Lingyan

    2011-07-01

    The potential of using mollusk shell powder in aragonite (razor clam shells, RCS) and calcite phase (oyster shells, OS) to remove Pb(2+), Cd(2+) and Zn(2+) from contaminated water was investigated. Both biogenic sorbents displayed very high sorption capacities for the three metals except for Cd on OS. XRD, SEM and XPS results demonstrated that surface precipitation leading to crystal growth took place during sorption. Calcite OS displayed a remarkably higher sorption capacity to Pb than aragonite RCS, while the opposite was observed for Cd. However, both sorbents displayed similar sorption capacities to Zn. These could be due to the different extent of matching in crystal lattice between the metal bearing precipitate and the substrates. The initial pH of the solution, sorbent's dosage and grain size affected the removal efficiency of the heavy meals significantly, while the organic matter in mollusk shells affected the removal efficiency to a lesser extent. PMID:21550150

  19. Determining provenance of marine metal pollution in French bivalves using Cd, Zn and Pb isotopes

    NASA Astrophysics Data System (ADS)

    Shiel, Alyssa E.; Weis, Dominique; Cossa, Daniel; Orians, Kristin J.

    2013-11-01

    Cadmium, Zn and Pb isotopic compositions (MC-ICP-MS) and elemental concentrations (HR-ICP-MS) have been used to distinguish between natural and anthropogenic sources of these metals in bivalves collected from the coastlines of France (English Channel, Atlantic and Mediterranean coasts). The Cd isotopic signatures (δ114Cd = -1.08‰ to -0.52‰) exhibited by bivalves from the coastlines of France, excluding those from NE France, are within the range of those exhibited by bivalves from the USA East coast (δ114Cd = -1.20‰ to -0.54‰). This indicates the high prevalence of industry, as well as the low natural contributions of Cd from North Atlantic waters in both regions. Thus, the significance of anthropogenic Cd sources is similar. These significant anthropogenic contributions are identified for bivalves with a large range in tissue Cd concentrations. Importantly, French bivalves from the Gironde estuary and Marennes-Oléron basin (regions of historic and modern importance for oyster farming, respectively) exhibited the highest Cd levels of the study. Their Cd isotopic signatures indicate historical smelting emissions remain the primary Cd source despite the cessation of local smelting activities in 1986 and subsequent remedial efforts. No significant variability is observed in the δ66Zn values of the French bivalves (∼0.53‰), with the exception of the much heavier compositions exhibited by oysters from the polluted Gironde estuary (1.19-1.27‰). Lead isotopes do not fractionate during processing like Cd and Zn. They can, therefore, be used to identify emissions from industrial processes and the consumption of unleaded gasoline and diesel fuel as metal sources to French bivalves. Cadmium and Zn isotopes are successfully used here as tracers of anthropogenic processing emissions and are combined with Pb isotope "fingerprinting" techniques to identify metal sources.

  20. Removal of Cd, Cu, Pb, and Zn from aqueous solutions by biochars.

    PubMed

    Doumer, M E; Rigol, A; Vidal, M; Mangrich, A S

    2016-02-01

    Sorption and desorption of heavy metals (Cd, Cu, Pb, and Zn) was evaluated in biochars derived from sugarcane bagasse (SB), eucalyptus forest residues (CE), castor meal (CM), green coconut pericarp (PC), and water hyacinth (WH) as candidate materials for the treatment of contaminated waters and soils. Solid-liquid distribution coefficients depended strongly on the initial metal concentration, with K d,max values mostly within the range 10(3)-10(4) L kg(-1). For all biochars, up to 95 % removal of all the target metals from water was achieved. The WH biochar showed the highest K d,max values for all the metals, especially Cd and Zn, followed by CE (for Cd and Pb) and PC (for Cd, Pb, and Zn). Sorption data were fitted satisfactorily with Freundlich and linear models (in the latter case, for the low concentration range). The sorption appeared to be controlled by cationic exchange, together with specific surface complexation at low metal concentrations. The low desorption yields, generally less than 5 %, confirmed that the sorption process was largely irreversible and that the biochars could potentially be used in decontamination applications. PMID:26438367

  1. EFFECTS OF AQUEOUS AL, CD, CU, FE(II), NI, AND ZN ON PB IMMOBILIZATION BY HYDROXYAPATITE

    EPA Science Inventory

    The effects of aqueous Al, Cd, Cu, Fe(II), Ni, or Zn on Pb immobilization by hydroxyapatite (Ca10(PO4),(OH)2) were studied. ead was removed mainly via hydroxyapatite dissolution and hydroxypyromorphite (Pb10(PO4)6(OH)2) precipitation in the presence of these metals with a Pb remo...

  2. Mobility of Heavy Metals (Pb, Cd, Zn) in the Pampeano and Puelche Aquifers, Argentina: Partition and Retardation Coefficients.

    PubMed

    Jakomin, L M; Marbán, L; Grondona, S; Glok Galli, M; Martínez, D E

    2015-09-01

    The prediction about metals behaviour in soil requires knowledge on their solid-liquid partitioning. Usually it is expressed with an empirical distribution coefficient or Kd, which gives the ratio of the metal concentration in the solid phase to that in the solution. Kd values have been determined for Zn, Pb and Cd from samples representing the two most exploited aquifers in Argentina, Pampeano and Puelche, at three different locations in the province of Buenos Aires. The Pampeano aquifer presented higher Kd values than the Puelche aquifer. Comparing Kd values, different relationships could be observed: (a) Pampeano aquifer: Pb > Zn > Cd, and (b) Puelche aquifer: Pb > Cd > Zn. Kd for Cd seems to be linked to cationic exchange capacity, but solid phases precipitation can be more determining for Pb and Zn. PMID:26183386

  3. Spectroscopy study of Zn, Cd, Pb and Cr ions immobilization on C-S-H phase

    NASA Astrophysics Data System (ADS)

    Żak, Renata; Deja, Jan

    2015-01-01

    Calcium silicate hydrates (C-S-H) have a large number of structural sites available for cations and anions to bind. The C-S-H phases are materials which have ability to toxic ions immobilization. Immobilization mechanisms for C-S-H include sorption, phase mixing, substitution and precipitation of insoluble compounds. This study presents the C-S-H (prepared with C/S ratios 1.0) phase as absorbent for immobilization of Zn, Cd, Pb and Cr ions. The C-S-H spectra before and after incorporation of heavy metals ions into the C-S-H structure were obtained. The effect of added heavy metals ions on the hydration phenomena was studied by means of X-ray diffractions analysis. FTIR spectra was measured. The microstructure and phase composition of C-S-H indicate that they can play an essential role in the immobilization of heavy metals. The properties of C-S-H in the presence of Zn, Cd, Pb and Cr cations were studied. The leaching ML test was used to evaluate the level of immobilization of heavy metals in C-S-H. The leached solutions are diluted and analyzed using atomic absorption spectrometry (AAS) and the activated solid particles are separated, washed, desiccated and analyzed by Fourier transform infrared (FTIR) spectroscopy. It was found that the degree of Cd, Zn, Pb and Cr cations immobilization was very high (exceeding 99.96%).

  4. Spectroscopy study of Zn, Cd, Pb and Cr ions immobilization on C-S-H phase.

    PubMed

    Żak, Renata; Deja, Jan

    2015-01-01

    Calcium silicate hydrates (C-S-H) have a large number of structural sites available for cations and anions to bind. The C-S-H phases are materials which have ability to toxic ions immobilization. Immobilization mechanisms for C-S-H include sorption, phase mixing, substitution and precipitation of insoluble compounds. This study presents the C-S-H (prepared with C/S ratios 1.0) phase as absorbent for immobilization of Zn, Cd, Pb and Cr ions. The C-S-H spectra before and after incorporation of heavy metals ions into the C-S-H structure were obtained. The effect of added heavy metals ions on the hydration phenomena was studied by means of X-ray diffractions analysis. FTIR spectra was measured. The microstructure and phase composition of C-S-H indicate that they can play an essential role in the immobilization of heavy metals. The properties of C-S-H in the presence of Zn, Cd, Pb and Cr cations were studied. The leaching ML test was used to evaluate the level of immobilization of heavy metals in C-S-H. The leached solutions are diluted and analyzed using atomic absorption spectrometry (AAS) and the activated solid particles are separated, washed, desiccated and analyzed by Fourier transform infrared (FTIR) spectroscopy. It was found that the degree of Cd, Zn, Pb and Cr cations immobilization was very high (exceeding 99.96%). PMID:25106815

  5. Atmospheric deposition of heavy metals (Cu, Zn, Cd and Pb) in Varanasi City, India.

    PubMed

    Sharma, Rajesh Kumar; Agrawal, Madhoolika; Marshall, Fiona M

    2008-07-01

    Rapid growth in urbanization and industrialization in developing countries may significantly contribute in heavy metal contamination of vegetables through atmospheric depositions. In the present study, an assessment was made to investigate the spatial and seasonal variations in deposition rates of heavy metals and its contribution to contamination of palak (Beta vulgaris). Samples of bulk atmospheric deposits and Beta vulgaris for analysis of Cu, Zn, Cd and Pb were collected from different sampling locations differing in traffic density and land use patterns. The results showed that the sampling locations situated in industrial or commercial areas with heavy traffic load showed significantly elevated levels of Cu, Zn and Cd deposition rate as compared to those situated in residential areas with low traffic load. The deposition rates of Cu, Zn and Cd were significantly higher in summer and winter as compared to rainy season, however, Pb deposition rate was significantly higher in rainy and summer seasons as compared to winter season. Atmospheric depositions have significantly elevated the levels of heavy metals in B. vulgaris collected during evening as compared to those collected in morning hours. The study further showed that local population has maximum exposure to Cd contamination through consumption of B. vulgaris. The present study clearly points out the urban and industrial activities of a city have potential to elevate the levels of heavy metals in the atmospheric deposits, which may consequently contaminate the food chain and thus posing health risk to the local population. PMID:17879134

  6. Valorization of biosorbent obtained from a forestry waste: Competitive adsorption, desorption and transport of Cd, Cu, Ni, Pb and Zn.

    PubMed

    Cutillas-Barreiro, Laura; Paradelo, Remigio; Igrexas-Soto, Alba; Núñez-Delgado, Avelino; Fernández-Sanjurjo, María José; Álvarez-Rodriguez, Esperanza; Garrote, Gil; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

    2016-09-01

    Bark from Pinus pinaster is one of the most abundant forestry wastes in Europe, and among the proposed technologies for its reutilization, the removal of heavy metals from wastewater has been gaining increasing attention. In this work, we have studied the performance of pine bark for heavy metal biosorption on competitive systems. Pb, Cu, Ni, Zn and Cd sorption and desorption at equilibrium were studied in batch experiments, whereas transport was studied in column experiments. Batch experiments were performed adding simultaneously different concentrations (0.08-3.15mM) of two or more metals in solution to pine bark samples. Column experiments were performed with 10mM solutions of two metals or a 5mM solution of the five metals. In general, the results under competitive conditions were different to those obtained in monoelemental experiments. The multi-metal batch experiments showed the adsorption sequence Pb≈Cu>Cd>Zn>Ni for lower metal doses, Pb>Cu>Cd>Zn>Ni for intermediate doses, and Pb>Cu>Cd≈Zn≈Ni for high metal doses. Desorption followed the sequence PbPbPb suffered the highest retention, with high capacity to displace Cd, Ni and Zn from adsorption sites on pine bark. The transport experiments produced comparable results to those obtained in the batch experiments, with pine bark retention capacity following the sequence Pb>Cu>Zn>Cd>Ni. The presence of a second metal affected the transport of all the elements studied except Pb, and confirmed the strong influence of Pb and Cu on the retention of the other metals. These results can help to appropriately design decontamination systems using this forestry waste. PMID:27232204

  7. Conventional crops and organic amendments for Pb, Cd and Zn treatment at a severely contaminated site.

    PubMed

    Pichtel, J; Bradway, D J

    2008-03-01

    The ability of selected plants and amendments to treat Pb, Cd and Zn accumulations from a metalliferous waste disposal site was studied both in the greenhouse and field. Spinach (Spinacea oleracea), cabbage (Brassica oleracea), and a grass-legume mix (red fescue, Festuca rubra; ryegrass, Lolium perenne); and bean (Vicia faba) were grown in the greenhouse on blast furnace slag or baghouse dust amended with composted peat (CP). All plant species accumulated Pb, Cd and Zn to varying degrees. Total soil metal concentrations had a marked influence on plant uptake. Topdressing versus incorporating CP had a significant (p<0.05) effect on spinach and cabbage tissue metal concentrations. Soil Pb and Zn tended to shift towards less bioavailable forms after treatment with CP. Field plots were treated with CP, farmyard manure (FYM), or inorganic fertilizer. Dry matter production of spinach, cabbage and a grass-legume mix was greatest on either the CP or FYM treatments. Phytostabilization in combination with organic amendments may be the most appropriate technology to ensure stabilization of soil metals at this site. PMID:17475483

  8. Electrokinetic enhancement on phytoremediation in Zn, Pb, Cu and Cd contaminated soil using potato plants.

    PubMed

    Aboughalma, Hanssan; Bi, Ran; Schlaak, Michael

    2008-07-01

    The use of a combination of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. Potato tubers were planted in plastic vessels filled with Zn, Pb, Cu and Cd contaminated soil and grown in a greenhouse. Three of these vessels were treated with direct current electric field (DC), three with alternative current (AC) and three remained untreated as control vessels. The soil pH varied from anode to cathode with a minimum of pH 3 near the anode and a maximum of pH 8 near the cathode in the DC treated soil profile. There was an accumulation of Zn, Cu and Cd at about 12 cm distance from anode when soil pH was 5 in the DC treated soil profile. There was no significant metal redistribution and pH variation between anode and cathode in the AC soil profile. The biomass production of the plants was 72% higher under AC treatment and 27% lower under DC treatment compared to the control. Metal accumulation was generally higher in the plant roots treated with electrical fields than the control. The overall metal uptake in plant shoots was lower under DC treatment compared to AC treatment and control, although there was a higher accumulation of Zn and Cu in the plant roots treated with electrical fields. The Zn uptake in plant shoots under AC treatment was higher compared to the control and DC treatment. Zn and Cu accumulation in the plant roots under AC and DC treatment was similar, and both were higher comparing to control. Cd content in plant roots under all three treatments was found to be higher than that in the soil. The Pb accumulation in the roots and the uptake into the shoots was lower compared to its content in the soil. PMID:18569305

  9. Sources and build up of Zn, Cd, Cr and Pb in the sludge of Gaza.

    PubMed

    Shomar, Basem

    2009-08-01

    A comprehensive monitoring program was conducted for the sludge of Gaza between 2001 and 2006. All 32 tested parameters except zinc and adsorbable organic halogens were within the allowable values for sludge to be applied in agriculture. Average concentrations of zinc (Zn) in the sludge from the Gaza Strip for the 4 years 2002-2005 reached 2,000 mg/kg which represents a major limiting factor for sludge application in agriculture. This study aimed to measure levels of Zn in the wastewater and sludge in December 2006 and to identify the sources and the build up of Zn in the sludge in Gaza. Cd, Cr and Pb were also assessed for their relationship to sources and buildup of Zn. The results showed that there is no significant fluctuation in the concentration of Cd, Cr and Pb in the different stages of wastewater treatment. Zn, however, is concentrated inside the treatment plant by processes of precipitation and/or absorption, particularly in the aerobic facilities. Although the plant receives wastewater with Zn concentrations of only 9 microg/l, this concentration increased 18-fold inside the aerobic lagoon of the treatment plant, before dropping to an average of 14 microg/l in the effluent wastewater. The sludge from the first sedimentation pond showed a Zn concentration of 567 mg/kg and increased in the effluent polishing pond to 1,643 mg/kg. The Zn concentration in 3-month-old sludge averaged 592 mg/kg. There was no correlation between the Zn concentrations in the sludge and the wastewater at the same location. However, there was a strong correlation between Zn and Pb in the sludge. The electroplating and galvanization industries are the major Zn producing industries in Gaza, with an average Zn of 2,995 and 1,557 microg/l, respectively in their effluent wastewater. These values do not represent a significant Zn pollution load to the treatment plant because these industries are limited in size and number, and their effluents are diluted before entering the treatment

  10. Sorption behavior of Cd, Cu, Pb, and Zn and their interactions in phytoremediated soil.

    PubMed

    Trakal, L; Komárek, M; Száková, J; Tlustos, P; Tejnecký, V; Drábek, O

    2012-09-01

    The aim of our study was to compare the sorption properties of a contaminated soil before and after two types of phytoremediation (natural phytoextraction vs. phytostabilization with dolomite limestone (DL) application). Soil from a pot experiment in controlled greenhouse conditions performed for two vegetation periods was used for the study. Lead, as the main contaminant in the studied soil, was easily desorbed by Cu, especially due to the increased affinity of Cu for soil organic matter; hence input of Cu to the studied soil can present another environmental risk in soils contaminated with other metals (such as Pb). In addition, the sorption behavior of chosen metals from single-element solutions differed from multielement solutions. The obtained results proved the different sorption behavior of metals in the single-element solution compared to the multi-element ones. Soil sorption behavior of Cd, Cu, and Zn decreased with the presence of the competitive metals; nevertheless, Pb sorption potential was not influenced by other competitive metals. Natural phytoextraction showed no significant effect on the sorption of Cd, Cu, Pb, and Zn onto the soil On the other hand, phytostabilization associated with DL application improved the soil sorption efficiency of all chosen metals, especially of Cu. PMID:22908646

  11. Accumulation of Sb, Pb, Cu, Zn and Cd by various plants species on two different relocated military shooting range soils.

    PubMed

    Evangelou, Michael W H; Hockmann, Kerstin; Pokharel, Rasesh; Jakob, Alfred; Schulin, Rainer

    2012-10-15

    Annually, more than 400 t Pb and 10 t Sb enter Swiss soils at some 2000 military shooting ranges. After the decommission of military shooting ranges, heavily contaminated soils (>2000 mg kg(-1) Pb) are landfilled or processed by soil washing, whereas for soils with less contamination, alternate strategies are sought. Although the use of military shooting ranges for grazing in Switzerland is common practice, no assessment has been done about the uptake of Sb in plants and its subsequent potential intake by grazing animals. We determined the uptake of Sb, Pb, Cu, Zn and Cd in the aboveground biomass of nine plant species growing on a calcareous (Chur) and a weakly acidic (Losone) military shooting range soil in order to assess if grazing would be safe to employ on decommissioned military shooting ranges. The two soils did not differ in their total concentrations of Cu, Zn, Sb and Cd, they differed however in the total concentration of Pb. Additionally, their physical and chemical properties were significantly different. The accumulation of Zn, Cu, Cd and Pb in the shoots of all nine plant species remained below the Swiss tolerance values for fodder plants (150 mg kg(-1) Zn, 15-35 mg kg(-1) Cu, 40 mg kg(-1) Pb, and 1 mg kg(-1) Cd DW), with the only exception of Pb in Chenopodium album shoots which reached a concentration of 62 mg kg(-1) DW. Antimony concentrations were 1.5-2.6-fold higher in plants growing on the calcareous soil than on the weakly acidic soil. Considering Cu, Zn, Pb, Sb and Cd, all plants, with the exception C. album, would be suitable for grazing on similar shooting range soils. PMID:22659605

  12. Distribution of Cd, Pb, Zn, Mo, and S in juvenile and mature Brassica napus L. var. napus.

    PubMed

    Romih, N; Grabner, B; Lakota, M; Ribaric-Lasnik, C

    2012-03-01

    The study was conducted at three locations in the Savinjska region of Slovenia, where soil is contaminated with heavy metals due to the zinc industry (Cinkarna Celje). In Ponikva the soil to a depth of 30 cm contains 0.8 mg kg(-1) Cd, 32.2 mg kg(-1) Pb, and 86 mg Zn kg(-1), in Medlog 1.4 mg kg(-1) Cd, 37.4 mg kg(-1) Pb, and 115 mg kg(-1) Zn and in Skofja vas 10.9 mg kg(-1) Cd, 239.7 mg kg(-1) Pb, and 1356 mg kg(-1) Zn. The pH at the selected sites was between 7.3 and 7.6. In the beginning of September 2006 two hybrids of Brassica napus L. var. napus, PR45 D01 and PR46 W31 suitable for production of biodiesel obtained from Pioneer Seeds Holding GmbH, were sown. After 96 days juvenile and after 277 days mature plants were collected. Parts of plants (root, shoot and seed) were separated and Cd, Pb, Zn, Mo, and S determined by ultra-trace ICP-MS. We compared the uptake of Cd, Pb, Zn, Mo and S in different parts of juvenile and mature plants of the two different hybrids, TF (translocation factor), BAF (bioaccumulation factor), and PP (phytoextraction potential) were calculated. The mature hybrid PR46 W31 had higher shoot/root ratio and higher PP for metals (Cd, Pb, and Zn) and lower PP for the micronutrient (Mo) and macronutrient (S) on the polluted site. The study demonstrated the potential use of oilseed rape on multiply polluted soils for production of 1st and 2nd generation biofuels. The potential restoration of degraded land could also disburden the use of agricultural land. PMID:22567712

  13. Geospatial Mapping of Pb, Cr, Cu, Zn, Cd, and Sb in Urban Soil, Cd. Juarez, Chihuahua, Mexico

    NASA Astrophysics Data System (ADS)

    Amaya, M. A.; Grimida, S. E.; Elkekli, A. R.; Aldouri, R. K.; Benedict, B. A.; Pingitore, N. E., Jr.

    2015-12-01

    Population-based random stratified sampling of the city of Cd. Juarez, Chihuahua, Mexico provided 500 city blocks for study. We collected soil from the public space (where present) in front of each house on a selected block; equal measured small volumes of these were combined to produce a composite sample for analysis. Such composite samples (1) decrease, by an order of magnitude, laboratory processing and analysis costs, and (2) smooth the data to represent blocks as averages of individual houses. Retention of the unanalyzed samples of the individual houses permits their later analysis should the composites suggest further study of individual houses on an anomalous block. Elemental analysis of 10 mg pressed powders was performed on a Panalytical Epsilon5 EDS-XRF, via 8 secondary targets and 12 USGS and NIST multi-element rock standards. The mean and (range) of concentration for Pb was 43 (13-550) ppm; for Cr, 31 (1.8-76); for Cu, 22 (6-550); for Zn 84 (42-415) ppm; for Cd, 1.9 (0.1-6.2); and for Sb, 5.9 (2.7-29). The old urban core of Cd. Juarez was marked by high levels of Pb, Cr, Cu, and Zn, and, to a smaller degree, of Cd and Sb. This pattern mirrors that of contiguous El Paso, Texas, USA, directly across the narrow Rio Grande. Businesses, industrial facilities, transportation (both railroads and highways), traditional "downtown" shopping, and old residential districts cluster in this urban core. A Pb-Cu-Zn smelter, which operated for more than a century until 1999, is present in the US adjacent to the Rio Grande, about two km away from downtown Cd. Juarez. Thus the city has been subject to both traditional metal sources (e.g., leaded gasoline, highway debris) and smelter emissions. The poplation of Cd. Juarez has exploded in the last few decades to some 1.5 million inhabitants due both to natural growth and in-migration from rural districts for economic opportunity. Most of this growth has been accommodated by radial expansion of the city into the surrounding

  14. Heavy metal (Cu, Zn, Cd and Pb) contamination of vegetables in urban India: a case study in Varanasi.

    PubMed

    Sharma, Rajesh Kumar; Agrawal, Madhoolika; Marshall, Fiona M

    2008-07-01

    The contributions of heavy metals in selected vegetables through atmospheric deposition were quantified in an urban area of India. Deposition rate of Zn was recorded maximum followed by Cu, Cd and Pb. The concentrations of Zn and Cu were highest in Brassica oleracea, Cd in Abelmoschus esculentus and B. oleracea, while Pb was highest in Beta vulgaris. Heavy metal pollution index showed that B. oleracea was maximally contaminated with heavy metals followed by A. esculentus and then B. vulgaris. The results of washing showed that atmospheric deposition has contributed to the increased levels of heavy metals in vegetables. Both Cu and Cd posed health risk to local population via test vegetables consumption, whereas Pb posed the same only through B. oleracea. The study concludes that atmospheric depositions can elevate the levels of heavy metals in vegetables during marketing having potential health hazards to consumers. PMID:18031880

  15. Comparison of As, Ni, Zn, Cd, and Pb removals using treatment agents.

    PubMed

    Choi, Jaeyoung; Yang, Jung-Seok; Park, Young Tae; Kim, Jong-Oh; Kim, Ki-Jun; Shim, Yon-Sik; Kwon, Hyun-Ho; Khan, Moonis Ali; Park, Jae-Woo; Um, Jeong-Gi; Jeon, Byong-Hun

    2012-01-01

    The removal of heavy metals, such as As, Ni, Zn, Cd and Pb, onto limestone, starfish, black shale and concrete from wastewater was studied. These materials, with a high capacity for heavy metals, can be obtained and employed as alternative low-cost substitutes. Various parameters, such as the neutralization capacity, changes in pH, redox potential and electric conductivity as a function of time, were quantified. Of the studied treatment agents, concrete showed high neutralization efficiency for acid mine drainage and maintained a pH value above 11. The adsorption of heavy metals was influenced by the compositions of the treatment agents. The experimental results of leaching revealed no significant follow-up release from any of the treatment agents. The results suggest that concrete could be used successfully for the treatment of mixed metal-contaminated wastes. PMID:22629616

  16. Impact of spiked concentrations of Cd, Pb, As and Zn in growth medium on elemental uptake of Nasturtium officinale (Watercress).

    PubMed

    Gounden, Denisha; Kisten, Kimona; Moodley, Roshila; Shaik, Shakira; Jonnalagadda, Sreekantha B

    2016-01-01

    This study is aimed at investigating the impact of water quality on the uptake and distribution of three non-essential and toxic elements, namely, As, Cd and Pb in the watercress plant to assess for metal toxicity. The plant was hydroponically cultivated under greenhouse conditions, with the growth medium being spiked with varying concentrations of As, Cd and Pb. Plants that were harvested weekly for elemental analysis showed physiological and morphological symptoms of toxicity on exposure to high concentrations of Cd and Pb. Plants exposed to high concentrations of As did not survive and the threshold for As uptake in watercress was established at 5 ppm. Translocation factors were low in all cases as the toxic elements accumulated more in the roots of the plant than the edible leaves. The impact of Zn on the uptake of toxic elements was also evaluated and Zn was found to have an antagonistic effect on uptake of both Cd and Pb with no notable effect on uptake of As. The findings indicate that phytotoxicity or death of the watercress plant would prevent it from being a route of human exposure to high concentrations of As, Cd and Pb in the environment. PMID:26479037

  17. Metal arsonate polymers of Cd, Zn, Ag and Pb supported by 4-aminophenylarsonic acid

    SciTech Connect

    Lesikar-Parrish, Leslie A.; Neilson, Robert H.; Richards, Anne F.

    2013-02-15

    The coordination preferences of 4-aminophenylarsonic acid, 4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H{sub 2}, (p-arsanilic acid) with CdCl{sub 2}{center_dot}2.5H{sub 2}O, ZnCl{sub 2}, Ag(SO{sub 3}CF{sub 3}) and Pb(NO{sub 3}){sub 2} have been investigated affording five new metal arsonate polymers. The reaction between 4-aminophenylarsonic acid and CdCl{sub 2}{center_dot}2.5H{sub 2}O resulted in a one-dimensional polymer, [{l_brace}Cd(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3}H)(Cl){sub 2}{r_brace}(H{sub 2}O){sub 2}]{sub n}, 1, in which the polymeric chain is propagated by bridging chlorides. Exchange of CdCl{sub 2} for ZnCl{sub 2} afforded [{l_brace}Zn{sub 2}(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3})(Cl){sub 2}{r_brace}(H{sub 2}O){sub 2}(Cl)]{sub n}, 2, featuring interlinked 6- and 8-membered [Zn-O-As] ring systems. The reaction of Ag(SO{sub 3}CF{sub 3}) with 4-aminophenylarsonic acid, afforded polymeric 3, [Ag(4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H)(4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H{sub 2})]{sub n} where coordination of the amino group to the silver center is observed and [{l_brace}Ag{sub 2}(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3}H)(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3})({mu}2-SO{sub 3}CF{sub 3}){sub 2}{r_brace}(SO{sub 3}CF{sub 3}){sub 2}]{sub n}, 4. By comparison, the reaction of p-arsanilic acid with Pb(NO{sub 3}){sub 2} yielded a polymeric chain [Pb(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3}H)(NO{sub 3}){sub 2}]{sub n}, 5 of similar topology to 1. The structures of 1-5 have been indiscriminately characterized by single crystal X-ray diffraction and their composition supported by relevant spectroscopic techniques. A comparison of the structural features of these polymers is used to determine the coordination preference of the ligand and factors influencing structural motifs, for example, the role of the anion. - Graphical abstract: The reaction of 4-aminophenylarsonic acid, 4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H{sub 2}, with cadmium, zinc, silver, and lead have resulted in

  18. Ion beam synthesis of CdS, ZnS, and PbS compound semiconductor nanocrystals

    SciTech Connect

    White, C.W.; Budai, J.D.; Meldrum, A.L.

    1997-12-01

    Sequential ion implantation followed by thermal annealing has been used to form encapsulated CdS, ZnS, and PbS nanocrystals in SiO{sub 2} and Al{sub 2}O{sub 3} matrices. In SiO{sub 2}, nanoparticles are nearly spherical and randomly oriented, and ZnS and PbS nanocrystals exhibit a bimodal size distribution. In Al{sub 2}O{sub 3}, nanoparticles are faceted and coherent with the matrix. Initial photoluminescence (PL) results are presented.

  19. Testing WHAM-FTOX with laboratory toxicity data for mixtures of metals (Cu, Zn, Cd, Ag, Pb).

    PubMed

    Tipping, Edward; Lofts, Stephen

    2015-04-01

    The Windermere humic aqueous model using the toxicity function (WHAM-FTOX ) describes cation toxicity to aquatic organisms in terms of 1) accumulation by the organism of metabolically active protons and metals at reversible binding sites, and 2) differing toxic potencies of the bound cations. Cation accumulation (νi , in mol g(-1) ) is estimated through calculations with the WHAM chemical speciation model by assuming that organism binding sites can be represented by those of humic acid. Toxicity coefficients (αi ) are combined with νi to obtain the variable FTOX (= Σ αi νi ) which, between lower and upper thresholds (FTOX,LT , FTOX,UT ), is linearly related to toxic effect. Values of αi , FTOX,LT , and FTOX,LT are obtained by fitting toxicity data. Reasonable fits (72% of variance in toxic effect explained overall) were obtained for 4 large metal mixture acute toxicity experiments involving daphnids (Cu, Zn, Cd), lettuce (Cu, Zn, Ag), and trout (Zn, Cd, Pb). Strong nonadditive effects, most apparent in results for tests involving Cd, could be explained approximately by purely chemical competition for metal accumulation. Tentative interpretation of parameter values obtained from these and other experimental data suggests the following order of bound cation toxicity: H < Al < (Cu Zn Pb UO2 ) < (Cd Ag). Another trend is a strong increase in Cd toxicity relative to that of Zn as organism complexity increases (from bacteria to fish). PMID:25318827

  20. Zn-, Cd-, and Pb-transcription factor IIIA: properties, DNA binding, and comparison with TFIIIA-finger 3 metal complexes

    PubMed Central

    Huang, Meilin; Krepkiy, Dmitriy; Hu, Weining; Petering, David H.

    2012-01-01

    Properties of the metal ion binding sites of Zn-transcription factor IIIA (TFIIIA) were investigated to understand the potential of this type of zinc finger to undergo reactions that remove Zn2+ from the protein. Zn–TFIIIA was purified from E. coli containing the cloned sequence for Xenopus laevis oocyte TFIIIA and its stoichiometry of bound Zn2+ was shown to depend on the details of the isolation process. The average dissociation constant of Zn2+ in Zn-TFIIIIA was 10−7. The dissociation constant for Zn-F3, the third finger from the N-terminus of TFIIIA, was 1.0 × 10−8. The reactivity of Zn–TFIIIA with a series of metal binding ligands, including 2-carboxy-2′-hydroxy-5′-sulfoformazylbenzene (zincon), 4-(2-pyridylazo)-resorcinol (PAR), and 3-ethoxy-2-oxo-butyraldehyde-bis-(N4-dimethylthiosemicarbazone) (H2KTSM2) revealed similar kinetics. The reactivity of PAR with Zn–TFIIIA declined substantially when the protein was bound to the internal control region (ICR) of the 5S ribosomal DNA. Both Cd2+ and Pb2+ disrupt TFIIIA binding to its cognate DNA sequence. The Pb2+ dissociation constant of Pb-F3 was measured as 2.5 × 10−8. According to NMR spectroscopy, F3 does not fold into a regular conformation in the presence of Pb2+. PMID:15134923

  1. Colonisation of a Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen with indigenous arbuscular mycorrhizal fungal mixture induces changes in heavy metal and nutrient uptake.

    PubMed

    Vogel-Mikus, Katarina; Pongrac, Paula; Kump, Peter; Necemer, Marijan; Regvar, Marjana

    2006-01-01

    Plants of the Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen (Brassicaceae) inoculated or not with indigenous arbuscular mycorrhizal (AM) fungal mixture were grown in a highly Cd, Zn and Pb contaminated substrate in order to evaluate the functionality of symbiosis and assess the possible impact of AM colonisation on heavy metal uptake and tolerance. The results suggest AM development in the metal hyperaccumulating T. praecox is favoured at elevated nutrient demands, e.g. during the reproductive period. AM colonisation parameters positively correlated with total soil Cd and Pb. Colonised plants showed significantly improved nutrient and a decreased Cd and Zn uptake as revealed by TRXRF, thus confirming the functionality of the symbiosis. Reduced heavy metal uptake, especially at higher soil metal contents, indicates a changed metal tolerance strategy in colonised T. praecox plants. This is to our knowledge the first report on AM colonisation of the Zn, Cd and Pb hyperaccumulator T. praecox in a greenhouse experiment. PMID:15998561

  2. Trace metals (Cd, Pb, Cu, Zn and Ni) in sediment of the submarine pit Dragon ear (Soline Bay, Rogoznica, Croatia)

    NASA Astrophysics Data System (ADS)

    Kljaković-Gašpić, Zorana; Bogner, Danijela; Ujević, Ivana

    2009-08-01

    Vertical profiles of trace metal (Cd, Pb, Zn, Cu, Ni) concentrations, organic matter content, carbonate content and granulometric composition were determined in two sediment cores from the submarine pit Dragon Ear (Middle Adriatic). Concentrations of the analyzed metals (Cd: 0.06-0.12 mg kg-1, Pb: 28.5-67.3 mg kg-1, Zn: 17.0-65.4 mg kg-1, Cu: 21.1-51.9 mg kg-1, Ni: 27.8-40.2 mg kg-1) were in usual range for Adriatic carbonate marine sediments. Nevertheless, concentrations of Cu, Zn, and especially Pb in the upper layer of sediments (top 12 cm) were higher than in bottom layer, while Cd and Ni concentration profiles were uniform. Regression analysis and principal component analysis were used to interpret distribution of trace metals, organic matter and carbonate content in sediment cores. Results of both analysis showed that concentrations of all trace metals in the core below the entrance to the pit were significantly positively correlated with organic matter and negatively correlated with carbonate, while in the core more distant from the entrance only Pb showed significant positive correlation with organic matter. Obtained results indicated that, except for lead which was enriched in surface sediment, in the time of sampling (before the building of the nautical marina) investigated area belonged to unpolluted areas.

  3. Relation of pH and other soil variables to concentrations of Pb, Cu, Zn, Cd, and Se in earthworms

    USGS Publications Warehouse

    Beyer, W.N.; Hensler, G.L.; Moore, J.

    1987-01-01

    Various soil treatments (clay, composted peat, superphosphate, sulfur, calcium carbonate, calcium chloride, zinc chloride, selenous acid) were added to experimental field plots to test the effect of different soil variables on the concentrations of 5 elements in earthworms (Pb, Cu, Zn, Cd, Se). Concentrations of the 5 elements were related to 9 soil variables (soil Pb, soil Cu, soil Zn, pH, organic matter, P, K, Mg, and Ca) with linear multiple regression. Lead concentrations in earthworms were positively correlated with soil Pb and soil organic matter, and negatively correlated with soil pH and soil Mg, with an R2 of 64%. Se concentrations were higher in earthworms from plots amended with Se, and Zn concentrations were higher in earthworms from plots amended with Zn. However, none of the other soil variables had important effects on the concentrations of Cu, Zn, Cd and Se in earthworms. Although some significant statistical relations were demonstrated, the values of r2 of all relations (> 20%) were so low that they had little predictive value.

  4. Use of bone meal amendments to immobilise Pb, Zn and Cd in soil: A leaching column study.

    PubMed

    Sneddon, I R; Orueetxebarria, M; Hodson, M E; Schofield, P F; Valsami-Jones, E

    2006-12-01

    The aim of this study is to test the stabilisation of metals in contaminated soils via the formation of low-solubility metal phosphates. Bone apatite, in the form of commercially available bone meal, was tested as a phosphate source on a mine waste contaminated made-ground with high levels of Pb, Zn and Cd. Triplicate leaching columns were set up at bone meal to soil ratios of 1:25 and 1:10, in addition to unamended controls, and were run for 18 months. The columns were irrigated daily with a synthetic rain solution at pH of 2, 3, and 4.4. After 100 days, the leachate Pb, Zn and Cd concentrations of all amended columns were significantly reduced. For 1:10 treatments, release of these metals was suppressed throughout the trial. For 1:25 treatments, Zn and Cd concentrations in the leachates began to increase after 300 days. DTPA and water extractions showed that Pb and Cd were more strongly held in the amended soils. This study concludes that the complexity of soil processes and the small quantities of metals sequestered precluded determination of a metal immobilisation mechanism. PMID:16584820

  5. Fifty-year sedimentary record of heavy metal pollution (Cd, Zn, Cu, Pb) in the Lot River reservoirs (France).

    PubMed

    Audry, Stéphane; Schäfer, Jörg; Blanc, Gérard; Jouanneau, Jean-Marie

    2004-12-01

    The Lot-Garonne fluvial system is known for its historic heavy metal pollution resulting from mining and smelting activities since the late 19th century. Here, we report 137Cs activities and heavy metal (Cd, Zn, Cu, Pb and V) concentration-depth profiles from sediment cores retrieved in 2001 from three reservoirs in the Lot River. High mean sedimentation rates of 2.4-2.8 cm a(-1) are indicated by 137Cs dating. The reservoir sediments have recorded the heavy metal deposition and thus allow establishing a connection between the temporal evolution of the heavy metal pollution and historical changes in smelting and waste-treatment proceedings. Based on heavy metal concentrations in sediments upstream of the anthropogenic inputs and bottom-sediments of the furthest downstream core (interpreted as old soil or riverbed), concentrations of approximately 17, approximately 82, approximately 0.33 and approximately 28 mg kg(-1) for Cu, Zn, Cd and Pb, respectively, are proposed as natural background values for the Lot fluvial system. The geoaccumulation index (Igeo [Müller, G., 1979. Schwermetalle in den Sedimenten des Rheins-Veränderungen seit. Umschav 79, 133-149.]) revealed that the Lot River sediments must be considered as "severely polluted" in Cd and Zn. Moreover, despite remediation efforts undertaken in the former smelting site, the Lot River is still "severely" (Igeo approximately 4) and "moderately to severely" (Igeo>2) impacted by Cd and Zn inputs, respectively. PMID:15325457

  6. Biosorption of Cu2+, Cd2+, Pb2+, and Zn2+ using dried marine green macroalga Caulerpa lentillifera.

    PubMed

    Pavasant, Prasert; Apiratikul, Ronbanchob; Sungkhum, Vimonrat; Suthiparinyanont, Prateep; Wattanachira, Suraphong; Marhaba, Taha F

    2006-12-01

    The sorption of Cu2+, Cd2+, Pb2+, and Zn2+ by a dried green macroalga Caulerpa lentillifera was investigated. The removal efficiency increased with pH. The analysis with FT-IR indicated that possible functional groups involved in metal sorption by this alga were O-H bending, N-H bending, N-H stretching, C-N stretching, C-O, SO stretching, and S-O stretching. The sorption of all metal ions rapidly reached equilibrium within 20min. The sorption kinetics of these metals were governed by external mass transfer and intraparticle diffusion processes. The sorption isotherm followed the Langmuir isotherm where the maximum sorption capacities was Pb2+>Cu2+>Cd2+>Zn2+. PMID:16330209

  7. Mineral transformations and Zn, Pb, As, Cd mobility in soils developed on Zn non-sulfide mining wastes near Olkusz, S Poland

    NASA Astrophysics Data System (ADS)

    Jerzykowska, Irena; Michalik, Marek

    2014-05-01

    To estimate the degree of threat posed by heavy metals and other environmentally harmful elements it is necessary to determine forms in which these elements occur and their stability in the weathering environment. The aim of this work was to (1) describe mineral transformations occurring in soils developed on Zn non-sulfide mining wastes near Olkusz (S Poland), (2) identify forms of occurrence of Zn, Pb, As, Cd; and (3) predict potential mobility of these elements. Studied samples come from soil profiles developed on four dumps after mining of non-sulfide Zn ores from the end of the XIX century until 1985. Two types of approaches were used: mineralogical methods (optical and electron microscopy with in situ elemental analysis, X-ray diffraction) and geochemical methods (selective sequential extraction and bulk elemental analysis). Zn in studied samples is present in smithsonite or hemimorphite, Zn aluminosilicates (smectite and kaolinite groups) and absorbed on Fe-oxide. The largest amounts of Pb is encountered in Mn-oxides and less in cerrusite, Fe-oxides and dolomite. As dominates as the ions absorbed on goethite and Cd as an impurity in carbonates, silicates and Zn-aluminosilicates, and in the form of exchangeable ions. Most important mineral transformations due to weathering observed in the samples are dissolution of dolomite, goethite, smithsonite, hemimorphite and precipitation of Zn-aluminosilicates, Mn-oxides and secondary Fe-oxides. The study has shown that Cd occurring in the form of exchangeable ions, potentially available to living organisms, pose the greatest threat to the environment. Cd is the most mobile in surface horizons of the soils developed on the oxidized ores dumps. Zn and Pb can be released from their forms in the event of a change of pH of the environment to a more acidic and As in case of changing conditions to more reductive.

  8. A survey of Pb, Cu, Zn, Cd, Cr, As, and Se in earthworms and soil from diverse sites

    USGS Publications Warehouse

    Beyer, W.N.; Cromartie, E.J.

    1987-01-01

    Earthworms and soils were collected from 20 diverse sites in Maryland, Pennsylvania, and Virginia, and were analyzed for Pb, Cu, Zn, Cd, Cr, As, and Se. Correlation coefficients relating Iconcentrations of the elements in earthworms to concentrations in soil were low (-0.20Pb (2100 ppm), Zn (1600 ppm), Cd (23 ppm) and Se (7.6 ppm) detected in earthworms were in the range reported to be toxic to animals fed diets containing these elements; however, even in the absence of any environmental contamination, some species of earthworms may contain high concentrations of Pb, Zn, and Se. Earthworms of the genus Eisenoides, for example, were exceptional in their ability to concentrate Pb. When earthworms are used as indicators of environmental contamination, it is important to identify the species, to report the soil characteristics, and to collect similar earthworms from very similar but uncontaminated soil.

  9. Geochemical and mineralogical evolution of the Zn-Cd-Pb bearing tailings from the Saint-Salvy mine, France

    NASA Astrophysics Data System (ADS)

    Munoz, M.; Courjault-Radé, P.; Castet, S.; Martin, F.; Tollon, F.

    2003-05-01

    4 million tonnes of waste generated by the treatment plant of the Saint-Salvy Zn mine have been dumped in a storage dam. Sulphides (3.5%) and Mn-siderite (20%) oxydize and dissolve. Drainage water exports most of SO4 and Mn released. According to geochemical modelling taking into account slightly acidic pH and slightly reducing conditions within the tailings, ferrihydrite precipitates in situ inducing partial immobilization of Fe, and partial retention of Zn, Pb and Cd. Time required for site inertization is estimated around a century.

  10. Characterization of bacteria in the rhizosphere soils of Polygonum pubescens and their potential in promoting growth and Cd, Pb, Zn uptake by Brassica napus.

    PubMed

    Jing, Yuan Xiao; Yan, Jun Lan; He, Huai Dong; Yang, Dan Jing; Xiao, Li; Zhong, Ting; Yuan, Ming; Cai, Xin De; Li, Shu Bin

    2014-01-01

    Microbe-enhanced phytoremediation has been considered as a promising measure for the remediation of metal-contaminated soils. In this study, two bacterial strains JYX7 and JYX10 were isolated from rhizosphere soils of Polygonum pubescens grown in metal-polluted soil and identified as of Enterobacter sp. and Klebsiella sp. based on 16S rDNA sequences, respectively. JYX7 and JYX10 showed high Cd, Pb and Zn tolerance and increased water-soluble Cd, Pb and Zn concentrations in culture solution and metal-added soils. Two isolates produced plant growth-promoting substances such as indole acetic acid, siderophore, 1-aminocyclopropane-1-carboxylic deaminase, and solubilized inorganic phosphate. Based upon their ability in metal tolerance and solubilization, two isolates were further studied for their effects on growth and accumulation of Cd, Pb, and Zn in Brassica napus (rape) by pot experiments. Rapes inoculated with JYX7 and JYX10 had significantly higher dry weights, concentrations and uptakes of Cd, Pb, Zn in both above-ground and root tissues than those without inoculation grown in soils amended with Cd (25 mg kg(-1)), Pb (200 mg kg(-1)) or Zn (200 mg kg(-1)). The present results demonstrated that JYX7 and JYX10 are valuable microorganism, which can improve the efficiency of phytoremediation in soils polluted by Cd, Pb, and Zn. PMID:24912234

  11. A comparative study of the most effective amendment for Pb, Zn and Cd immobilization in contaminated soils.

    PubMed

    Szrek, Dominik; Bajda, Tomasz; Manecki, Maciej

    2011-01-01

    The problem of an extensive contamination of soils with metals can be resolved using an in situ chemical immobilization technology. Five substances (natural zeolite, bog iron ore, "Polifoska 15" fertilizer, triple superphosphate, diammonium phosphate) were tested to determine their efficiency to immobilize Zn, Pb and Cd in smelter-contaminated soil in the Upper Silesia region. Soil samples were collected at three sites located in the vincity of a Pb-Zn smelter and a sludge landfill near the town of Bukowno. Effective reduction of leachable and fitoavailable Zn, Pb and Cd concentrations in soil was observed after addition of diammonium phosphate, "Polifoska 15" fertilizer and bog iron ore amendments. Additional test proved that immobilization effect gained by these amendments sustains at low-temperature conditions. It was noticed that phosphate addition resulted in lowering pH and mobilization of As(V) in soils. Good immobilization effectiveness and lack of major adverse effects of bog iron application suggest that this is the method of choice. PMID:21961559

  12. Impact of multi-metals (Cd, Pb and Zn) exposure on the physiology of the yeast Pichia kudriavzevii.

    PubMed

    Mesquita, Vanessa A; Machado, Manuela D; Silva, Cristina F; Soares, Eduardo V

    2015-07-01

    Metal contamination of the environment is frequently associated to the presence of two or more metals. This work aimed to study the impact of a mixture of metals (Cd, Pb and Zn) on the physiology of the non-conventional yeast Pichia kudriavzevii. The incubation of yeast cells with 5 mg/l Cd, 10 mg/l Pb and 5 mg/l Zn, for 6 h, induced a loss of metabolic activity (assessed by FUN-1 staining) and proliferation capacity (evaluated by a clonogenic assay), with a small loss of membrane integrity (measured by trypan blue exclusion assay). The staining of yeast cells with calcofluor white revealed that no modification of chitin deposition pattern occurred during the exposure to metal mixture. Extending for 24 h, the exposure of yeast cells to metal mixture provoked a loss of membrane integrity, which was accompanied by the leakage of intracellular components. A marked loss of the metabolic activity and the loss of proliferation capacity were also observed. The analysis of the impact of a single metal has shown that, under the conditions studied, Pb was the metal responsible for the toxic effect observed in the metal mixture. Intracellular accumulation of Pb seems to be correlated with the metals' toxic effects observed. PMID:25794581

  13. Potential hyperaccumulation of Pb, Zn, Cu and Cd in endurant plants distributed in an old smeltery, northeast China

    NASA Astrophysics Data System (ADS)

    Cui, Shuang; Zhou, Qixing; Chao, Lei

    2007-01-01

    The absorption and accumulation of Pb, Zn, Cu and Cd in some endurant weed plant species that survived in an old smeltery in Liaoning, China, were systematically investigated. Potential hyperaccumulative characteristics of these species were also discussed. The results showed that metal accumulation in plants differed with species, tissues and metals. Endurant weed plants growing in this contaminated site exhibited high metal adaptability. Both the metal exclusion and detoxification tolerance strategies were involved in the species studied. Seven species for Pb and four species for Cd were satisfied for the concentration time level standard for hyperaccumulator. Considering translocation factor (TF) values, one species for Pb, seven species for Zn, two species for Cu and five species for Cd possessed the characteristic of hyperaccumulator. Particularly, Abutilon theophrasti Medic, exhibited strong accumulative ability to four heavy metals. Although enrichment coefficients of all samples were lesser than 1 and the absolute concentrations didn’t reach the standard, species mentioned above were primarily believed to be potential hyperaccumulators.

  14. Can the shell of the green-lipped mussel Perna viridis from the west coast of Peninsular Malaysia be a potential biomonitoring material for Cd, Pb and Zn?

    NASA Astrophysics Data System (ADS)

    Yap, C. K.; Ismail, A.; Tan, S. G.; Abdul Rahim, I.

    2003-07-01

    The distributions of Cd, Pb and Zn in the total soft tissues and total shells of the green-lipped mussel Perna viridis were studied in field collected samples as well as from laboratory experimental samples. The results showed that Cd, Pb and Zn were readily accumulated in the whole shells. In mussels sampled from 12 locations along the west coast of Peninsular Malaysia, the ratios of the shell metals to the soft tissue metals were different at each sampling site. Nevertheless, the Cd and Pb levels in the shells were always higher than those in the soft tissues, while the Zn level was higher in the soft tissues than in the shells. In comparison with soft tissues, the degrees of variability for Pb and Cd concentrations in the shells were lower. The lower degrees of variability and significant ( P<0.05) correlation coefficients of Cd and Pb within the shells support the use of the mussel shell as a suitable biomonitoring material for the two metals rather than the soft tissue since this indicated that there is more precision (lower CV) in the determination of metal concentrations in the shell than in the soft tissue. Experimental work showed that the pattern of depuration in the shell was not similar to that of the soft tissue although their patterns of accumulation were similar. This indicated that the depuration of heavy metals in the shell was not affected by the physiological conditions of the mussels. Although Zn could be regulated by the soft tissue, the incorporated Cd, Pb and Zn remained in the shell matrices. The present results support the use of the total shell of P. viridis as a potential biomonitoring material for long-term contamination of Cd, Pb and Zn.

  15. Conversion of the trace elements Zn, Cd, and Pb in the combustion of near-Moscow coals

    SciTech Connect

    E.V. Samuilov; L.N. Lebedeva; L.S. Pokrovskaya; M.V. Faminskaya

    2008-10-15

    A model for the conversion of trace elements in the combustion of near-Moscow coals based on a complex approach combining the capabilities of geochemistry, chemical thermodynamics, phase analysis, and chemical kinetics is proposed. The conversion of the trace elements Zn, Cd, and Pb as the constituents of near-Moscow coal in the flow of coal combustion products along the line of the P-59 boiler at the Ryazanskaya Thermal Power Plant was calculated. Experimental data were used in the development of the model and in calculations.

  16. Bioacumulation and ultrastructural effects of Cd, Cu, Pb and Zn in the moss Scorpiurum circinatum (Brid.) Fleisch. & Loeske.

    PubMed

    Basile, A; Sorbo, S; Pisani, T; Paoli, L; Munzi, S; Loppi, S

    2012-07-01

    This paper tested if culturing the moss Scorpiurum circinatum (Brid.) Fleisch. & Loeske with metal solutions (Cd, Cu, Pb and Zn) for 30 days causes metal bioaccumulation and ultrastructural changes. The results showed that despite the high heavy metal concentrations in treatment solutions, treated samples did not show severe ultrastructural changes and cells were still alive and generally well preserved. Bioaccumulation highlighted that moss cells survived to heavy metal toxicity by immobilizing most toxic ions extracellularly, likely in binding sites of the cell wall, which is the main site of metal detoxification. PMID:22516710

  17. Monitoring air pollution at Mohammedia (Morocco): Pb, Cd and Zn in the blood of pigeons (Columba livia).

    PubMed

    Kouddane, N; Mouhir, L; Fekhaoui, M; Elabidi, A; Benaakame, R

    2016-05-01

    The concentrations of Pb, Cd and Zn were investigated in the blood of pigeons (Columba livia) in order to assess the degree of pollution by heavy metal. For this, wild city pigeons were caught at four different locations in Mohammedia classified according to their industrial activity and road traffic density. Significant difference in heavy metal concentrations were observed between sites studied, the highest lead and cadmium levels were found in industrial area and center town, while the highest zinc level was found in the less contaminated area. These results indicate that the industrial activities and the road traffic are the most important source of pollution. PMID:26903169

  18. Toxicities and tolerances of Cd, Cu, Pb and Zn in a primary producer (Isochrysis galbana) and in a primary consumer (Perna viridis).

    PubMed

    Yap, C K; Ismail, A; Omar, H; Tan, S G

    2004-02-01

    Studies on toxicities and tolerances of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in the brown alga Isochrysis galbana and in the green-lipped mussel Perna viridis were conducted by short-term bioassays using endpoints growth production and mortality, respectively. The 5-day EC(50) and 24-h LC(50) of these heavy metals were determined in the brown alga and mussel, respectively. The EC(50) values calculated for the alga were 0.74 mg/l for Cd, 0.91 mg/l for Cu, 1.40 mg/l for Pb and 0.60 mg/l for Zn. The LC(50) values for the mussels were 1.53 mg/l for Cd, 0.25 mg/l for Cu, 4.12 mg/l for Pb and 3.20 mg/l for Zn. These LC(50) values were within the concentration ranges as reported by other authors who used P. viridis as the test organism. Based on these EC(50) and LC(50) values, the alga was most sensitive to Zn, followed by Cd, Cu and Pb while the mussel was most sensitive to Cu, followed by Cd, Zn and Pb. Differences in the trophic levels, metal handling strategies, biology and ecology of the primary producer (brown alga) and the primary consumer (mussel) are believed to be the plausible causes for the different toxicities and tolerances of the metals studied. PMID:14680893

  19. Organic acid enhanced soil risk element (Cd, Pb and Zn) leaching and secondary bioconcentration in water lettuce (Pistia stratiotes L.) in the rhizofiltration process.

    PubMed

    Veseý, Tomás; Tlustos, Pavel; Száková, Jirina

    2012-04-01

    The use of natural chelates to enhance risk element mobility combined with rhizofiltration by free floating macrophytes have not been thoroughly studied in recent years. The aim of this study was to investigate the efficiency of organic acids in soil by conducting flushing experiments to enhance the mobility of Cd, Pb, and Zn from soil to solution. In addition, the bioaccumulation of Cd, Pb, and Zn, in water lettuce (Pistia stratiotes L.) will be studied as they affect the biomass in the rhizofiltration process. The results revealed that citric and tartaric acids mobilised the highest amount of all risk elements. In comparison to control, citric acid mobilised 71%, 181%, and 112% of Cd, Pb, and Zn while tartaric acid mobilised 70%, 155%, and 135% of Cd, Pb, and Zn respectively. The bioconcentration factor was approximately 2-5 times higher for juvenile plants than mature plants for all treatments as well as for both parts (leaves and roots). The risk element translocation into aerial parts decreased with increased time. Juvenile and mature plants proved a high accumulation potential and a 3 week growth period was observed as a sufficient time period to remove more than 80% of Cd, Pb, and Zn. PMID:22567715

  20. Activated carbon and biochar from agricultural by-products in the adorption of Cd, Pb and Zn under laboratory conditions

    NASA Astrophysics Data System (ADS)

    Coscione, Aline; Zini, Barbara

    2015-04-01

    The immobilization of inorganic contaminants by using biochar in soils has played an increasingly important role and it is seen as an attractive alternative for the remediation of heavy metals. Although, the production of activated carbon (CA) from agricultural by-products has received special attention, the activation of the the organic source has been studied in order to increase its porposity, surface area and chemical polarity, resulting in higher adsorption of metals. Therefore, this study aimed to evaluate the effectiveness of BC and CA samples, obtained from a eucalyptus husks and cane sugar bagasse after activation with 20% phosphoric acid and pyrolyzed at 450oC in the retention of Zn, Cd and Pb using contaminated individual solutions. The experiment was performed using samples of activated carbon of eucalyptus husk (CCA), eucalyptus husk biochar (BC), activated carbon of sugar cane bagasse (CBA) and sugar cane bagasse biochar (BB), treated with Zn, Cd (range of tested solution from 0.1 up to 12 mmol L-1) and Pb (from 0.1 up 50 mmol L-1) and the adjustemento of Langmuir adsorption isotherms. Samples obtained from bagasse presented higher adsoprtion of the metals tested then eucalyptus. Also the activation process had not the expected effect on either eucalyptus and bagasse samples The maxmum adsorption capacyty of samples were as follws, in mmol g-1: for Cd - 0.36 for BC; 0.32 for CCA; 0.40 for BB; 0.31 for CBA. For Zn- 0.14 for BC; no adsorbed by CCA; 0.35 5 for BB; 0.06 for CBA. For Pb - 1.24 for BC; 0.40 for CCA; 0,45 for BB; 0,03 for CBA. However, it was also observed that due to the activation with phosphoric acid, the pH of the activated carbon (CCA and CBA) were 2.4 and 2.5 in comparison with the biochars not activated (BC and BB) 9.7 and 7.0 respectively. Thus, it is yet not possible to state if the calculate capacity is due exclusively to the complexation of chemical groups in the surface of samples or to which extent there is a contribution of

  1. The spatial and temporal trends of Cd, Cu, Hg, Pb and Zn in Seine River floodplain deposits (1994-2000)

    USGS Publications Warehouse

    Grosbois, C.; Meybeck, M.; Horowitz, A.; Ficht, A.

    2006-01-01

    Fresh floodplain deposits (FD), from 11 key stations, covering the Seine mainstem and its major tributaries (Yonne, Marne and Oise Rivers), were sampled from 1994 to 2000. Background levels for Cd, Cu, Hg, Pb, and Zn were established using prehistoric FD and actual bed sediments collected in small forested sub-basins in the most upstream part of the basin. Throughout the Seine River Basin, FD contain elevated concentrations of Cd, Cu, Hg, Pb and Zn compared to local background values (by factors > twofold). In the Seine River Basin, trace element concentrations display substantial downstream increases as a result of increasing population densities, particularly from Greater Paris (10 million inhabitants), and reach their maxima at the river mouth (Poses). These elevated levels make the Seine one of the most heavily impacted rivers in the world. On the other hand, floodplain-associated trace element levels have declined over the past 7 years. This mirrors results from contemporaneous suspended sediment surveys at the river mouth for the 1984-1999 period. Most of these temporal declines appear to reflect reductions in industrial and domestic solid wastes discharged from the main Parisian sewage plant (Seine Aval). ?? 2005 Elsevier B.V. All rights reserved.

  2. Red mud and fly ash for remediation of mine sites contaminated with As, Cd, Cu, Pb and Zn.

    PubMed

    Bertocchi, Anna F; Ghiani, Marcello; Peretti, Roberto; Zucca, Antonio

    2006-06-30

    The paper presents the results of a laboratory investigation conducted for assessing the feasibility of immobilising the heavy metals (As, Cd, Cu, Pb and Zn) contained in a disused mine tailings dam. Samples of tailings were mixed with relatively small proportions of bauxite red mud and power station fly ash. The sorption capacity of these two materials, already determined for Cd, Cu, Pb and Zn, has been determined here for arsenic by means of batch experiments on purposely prepared solutions. The results of this preliminary investigation show that sorption capacity is strongly influenced by pH. While the red mud performs better at low pH, the ability of fly ash to adsorb As increases with increasing pH. Tests carried out in leach columns containing tailings alone and tailings mixed with 15% by weight neutralized red mud or fly ash demonstrate the heavy metal sorption potential of the two materials, the red mud proving to be the more effective. PMID:16326004

  3. Utilization of biochar and activated carbon to reduce Cd, Pb and Zn phytoavailability and phytotoxicity for plants.

    PubMed

    Břendová, Kateřina; Zemanová, Veronika; Pavlíková, Daniela; Tlustoš, Pavel

    2016-10-01

    In the present study, the content of risk elements and content of free amino acids were studied in spinach (Spinacia oleracea L.) and mustard (Sinapis alba L.) subsequently grown on uncontaminated and contaminated soils (5 mg Cd/kg, 1000 mg Pb/kg and 400 mg Zn/kg) with the addition of activated carbon (from coconut shells) or biochar (derived from local wood residues planted for phytoextaction) in different seasons (spring, summer and autumn). The results showed that activated carbon and biochar increased biomass production on contaminated site. Application of amendments decreased Cd and Zn uptake by spinach plants. Mustard significantly increased Pb accumulation in the biomass as well in subsequently grown autumn spinach. Glutamic acid and glutamine were major free amino acids in leaves of all plants (15-34% and 3-45%) from total content. Application of activated carbon and biochar increased content of glutamic acid in all plants on uncontaminated and contaminated soils. Activated carbon and biochar treatments also induced an increase of aspartic acid in spinach plants. Biochar produced from biomass originated from phytoextraction technologies promoted higher spinach biomass yield comparing unamended control and showed a tendency to reduce accumulation of cadmium and zinc and thus it is promising soil amendment. PMID:27544477

  4. Bioaccumulation of Cd, Pb and Zn in the edible and inedible tissues of three sturgeon species in the Iranian coastline of the Caspian Sea.

    PubMed

    Mashroofeh, Abdulreza; Bakhtiari, Alireza Riyahi; Pourkazemi, Mohammad; Rasouli, Sana

    2013-01-01

    The accumulations of Cd, Pb and Zn were determined in edible and inedible tissues of Persian sturgeon (Acipenser persicus; n=27), stellate sturgeon (Acipenser stellatus; n=5) and beluga (Huso huso; n=4) collected from coastal waters of the South Caspian Sea from March to April 2011. Concentrations of metals evaluated in the caviar, muscle, liver, kidney, gills, ovary and heart of the three species of sturgeons have been assessed using the flame and graphite furnace atomic absorption spectrophotometer. Concentrations of Zn, Pb and Cd in the edible and inedible tissues were apparently different among the three species of sturgeons. Especially, beluga heart showed the highest concentrations of Zn and Pb and Cd in Persian sturgeon liver. The analyzed metals were found in the caviar and muscle samples of Persian sturgeon and likewise muscle samples two other sturgeon species at mean concentrations under the permissible limits proposed by MAFF (2000). PMID:22990022

  5. Cylindrospermopsis raciborskii (Cyanobacteria) exudates: chemical characterization and complexation capacity for Cu, Zn, Cd and Pb.

    PubMed

    Tonietto, Alessandra Emanuele; Lombardi, Ana Teresa; Vieira, Armando Augusto Henriques; Parrish, Christopher C; Choueri, Rodrigo Brasil

    2014-02-01

    Cylindrospermopsis raciborskii is a cosmopolitan and potentially toxic planktonic Cyanobacteria that produces and exudes copious amounts of dissolved organic materials. This organism dominates the eutrophic reservoir Barra Bonita (Brazil), where it normally blooms throughout the year. This investigation focused on the characterization of such exudates analyzing their capacity to complex copper, zinc, lead and cadmium through the determination of ligand concentration (CL) and conditional stability constant (logK'ML), as well as elemental composition (C, H, N and S), the content of carbohydrates, proteins, lipids and dissolved organic carbon (DOC). The dissolved organic material was fractionated into 3 molecular weights (>30 kDa; 30-10 kDa; 10-3 kDa) and each fraction was analyzed. The results showed that in the >30 kDa and 30-10 kDa fractions carbohydrates dominate over proteins and lipids. Different CL and logK'ML were obtained for the different molecular weight fractions of the excreted organic materials, suggesting high diversity of ligands. In the >30 kDa, there were more complexing sites (CL) for Cu, but higher affinity (K') for Zn. In the 30-10 kDa fraction, the higher CL was for Cd, but the greatest affinities were for Cu and Zn. In the 10-3 kDa fraction, higher CL was obtained for Cd and Zn, while Cu and Cd had the highest strengths of association. In the environment, such diversity of ligands and strengths of association can result in a displacement of metals weakly bound to the EOM, and increase metal buffering capacity of the environment, supporting higher metal inputs before toxic effects are detected in the biota. PMID:24169513

  6. Characterization of endophytic Rahnella sp. JN6 from Polygonum pubescens and its potential in promoting growth and Cd, Pb, Zn uptake by Brassica napus.

    PubMed

    He, Huaidong; Ye, Zhihong; Yang, Danjing; Yan, Junlan; Xiao, Li; Zhong, Ting; Yuan, Ming; Cai, Xinde; Fang, Zhanqiang; Jing, Yuanxiao

    2013-02-01

    Microbe-assisted phytoremediation has been considered as a promising measure for the remediation of heavy metal-polluted soils. In this study, a metal-tolerance and plant growth-promoting endophytic bacterium JN6 was firstly isolated from roots of Mn-hyperaccumulator Polygonum pubescens grown in metal-contaminated soil and identified as Rahnella sp. based on 16S rDNA gene sequence analysis. Strain JN6 showed very high Cd, Pb and Zn tolerance and effectively solubilized CdCO(3), PbCO(3) and Zn(3)(PO(4))(2) in culture solution. The isolate produced plant growth-promoting substances such as indole-3-acetic acid, siderophore, 1-aminocyclopropane-1-carboxylic deaminase, and also solubilized inorganic phosphate. Based upon its ability in metal tolerance and solubilization, the isolate JN6 was further studied for its effects on the growth and accumulation of Cd, Pb and Zn in Brassica napus (rape) by pot experiments. Rape plants inoculated with the isolate JN6 had significantly higher dry weights, concentrations and uptake of Cd, Pb and Zn in both above-ground and root tissues than those without inoculation grown in soils amended with Cd (25 mg kg(-1)), Pb (200 mg kg(-1)) or Zn (200 mg kg(-1)). The isolate also showed a high level of colonization in tissue interior of rapes. The present results demonstrated that Rahnella sp. JN6 is a valuable microorganism, which can cost-effectively improve the efficiency of phytoremediation in soils contaminated by Cd, Pb and Zn. PMID:23177711

  7. Using isotopic dilution to assess chemical extraction of labile Ni, Cu, Zn, Cd and Pb in soils.

    PubMed

    Garforth, J M; Bailey, E H; Tye, A M; Young, S D; Lofts, S

    2016-07-01

    Chemical extractants used to measure labile soil metal must ideally select for and solubilise the labile fraction, with minimal solubilisation of non-labile metal. We assessed four extractants (0.43 M HNO3, 0.43 M CH3COOH, 0.05 M Na2H2EDTA and 1 M CaCl2) against these requirements. For soils contaminated by contrasting sources, we compared isotopically exchangeable Ni, Cu, Zn, Cd and Pb (EValue, mg kg(-1)), with the concentrations of metal solubilised by the chemical extractants (MExt, mg kg(-1)). Crucially, we also determined isotopically exchangeable metal in the soil-extractant systems (EExt, mg kg(-1)). Thus 'EExt - EValue' quantifies the concentration of mobilised non-labile metal, while 'EExt - MExt' represents adsorbed labile metal in the presence of the extractant. Extraction with CaCl2 consistently underestimated EValue for Ni, Cu, Zn and Pb, while providing a reasonable estimate of EValue for Cd. In contrast, extraction with HNO3 both consistently mobilised non-labile metal and overestimated the EValue. Extraction with CH3COOH appeared to provide a good estimate of EValue for Cd; however, this was the net outcome of incomplete solubilisation of labile metal, and concurrent mobilisation of non-labile metal by the extractant (MExtEValue). The Na2H2EDTA extractant mobilised some non-labile metal in three of the four soils, but consistently solubilised the entire labile fraction for all soil-metal combinations (MExt ≈ EExt). Comparison of EValue, MExt and EExt provides a rigorous means of assessing the underlying action of soil chemical extraction methods and could be used to refine long-standing soil extraction methodologies. PMID:27153236

  8. Decrease of Zn, Cd and Pb concentrations in marine fish species over a decade as response to reduction of anthropogenic inputs: the example of Tagus estuary.

    PubMed

    Raimundo, Joana; Pereira, Patrícia; Caetano, Miguel; Cabrita, Maria Teresa; Vale, Carlos

    2011-12-01

    Concentrations of Zn, Cd and Pb were measured in muscle of pelagic, demersal and benthic fishes, captured in the coastal area adjoining the Tagus estuary (Portugal), in 1998 and 2010. Additionally, Pb and Cd were determined in estuarine waters, showing a pronounced decrease between 1999 and 2010. Accordingly, specimens captured in 2010 presented significantly lower metal concentrations than individuals caught in 1998. Reductions were more evident for Pb (reduction of 59-99%) than for Cd (14-93%) and Zn (17-54%). Values in pelagic and demersal species exhibited higher reductions than in benthic species. Decrease of metal concentrations in fish appears thus to reflect the improvement of estuarine water quality as anthropogenic sources have been reduced or eliminated. Furthermore, it emphasises the usefulness of the descriptor "Contaminants in Fish" to assess the efficiency of measures to achieve a good environmental status, in the scope of the Marine Strategy Framework Directive. PMID:21986541

  9. Behaviour of Cd, Cr, Mn, Ni, Pb, and Zn in sewage sludge incineration by fluidised bed furnace

    SciTech Connect

    Marani, D.; Braguglia, C.M.; Mininni, G.; Maccioni, F

    2003-07-01

    Cd, Cr, Mn, Ni, Pb, and Zn behaviour during sewage sludge incineration was investigated in seven pilot tests using a circulating fluidised bed furnace. Dewatered sludge at a solids concentration of 15-18% was fed to the furnace either alone (two tests) or spiked with chlorinated organic compounds (five tests). The behaviour of metals in the fluidised bed furnace was studied by comparing metal concentrations in the two main ash streams: ash separated from the cyclone immediately following the fluidised bed furnace, and fly ash recovered in the final bag filter. A metal enrichment factor was defined as the ratio of metal concentration between filter ash and cyclone ash. Only Cd and Pb showed any significant enrichment. Their enrichment factors were mainly affected by chlorine concentration in the feed sludge. To check whether simple equilibrium models may explain and predict metal behaviour, experimental data were compared with percentage of the metal vaporisation in the combustion chamber predicted using a thermodynamic model. Discrepancies between model predictions and experimental results are accounted for by considering that kinetics may be a limiting factor in the formation of metal chloride gaseous species. Due to the very short sludge residence time in the fluidised bed furnace, the gaseous compounds have little chance to evolve completely.

  10. Toxicity Induced by a Metal Mixture (Cd, Pb and Zn) in the Yeast Pichia kudriavzevii: The Role of Oxidative Stress.

    PubMed

    Mesquita, Vanessa A; Silva, Cristina F; Soares, Eduardo V

    2016-05-01

    The present work aims to contribute for the elucidation of the role of oxidative stress in the toxicity associated with the exposure of Pichia kudriavzevii to multi-metals (Cd, Pb and Zn). Cells of the non-conventional yeast P. kudriavzevii exposed for 6 h to the action of multi-metals accumulated intracellular reactive oxygen species (ROS), evaluated through the oxidation of the probe 2',7'-dichlorodihydrofluorescein diacetate. A progressive loss of membrane integrity (monitored using propidium iodide) was observed in multi-metal-treated cells. The triggering of intracellular ROS accumulation preceded the loss of membrane integrity. These results suggest that the disruption of membrane integrity can be attributed to the oxidative stress. The exposure of yeast cells to single metal showed that, under the concentrations tested, Pb was the metal responsible for the induction of the oxidative stress. Yeast cells coexposed to an antioxidant (ascorbic acid) and multi-metals did not accumulate intracellular ROS, but loss proliferation capacity. Together, the data obtained indicated that intracellular ROS accumulation contributed to metal toxicity, namely for the disruption of membrane integrity of the yeast P. kudriavzevii. It was proposed that Pb toxicity (the metal responsible for the toxic symptoms under the conditions tested) result from the combination of an ionic mechanism and the intracellular ROS accumulation. PMID:26781618

  11. Increased ability of transgenic plants expressing the bacterial enzyme ACC deaminase to accumulate Cd, Co, Cu, Ni, Pb, and Zn.

    PubMed

    Grichko, V P; Filby, B; Glick, B R

    2000-07-28

    Transgenic tomato plants Lycopersicon esculentum (Solanaceae) cv. Heinz 902 expressing the bacterial gene 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, under the transcriptional control of either two tandem 35S cauliflower mosaic virus promoters (constitutive expression), the rolD promoter from Agrobacterium rhizogenes (root specific expression) or the pathogenesis related PRB-1b promoter from tobacco, were compared to non-transgenic tomato plants in their ability to grow in the presence of Cd, Co, Cu, Mg, Ni, Pb, or Zn and to accumulate these metals. Parameters that were examined include metal concentration and ACC deaminase activity in both plant shoots and roots; root and shoot development; and leaf chlorophyll content. In general, transgenic tomato plants expressing ACC deaminase, especially those controlled by the PRB-1b promoter, acquired a greater amount of metal within the plant tissues, and were less subject to the deleterious effects of the metals on plant growth than were non-transgenic plants. PMID:10936659

  12. CORRELATION OF THE PARTITIONING OF DISSOLVED ORGANIC MATTER FRACTIONS WITH THE DESORPTION OF CD, CU, NI, PB AND ZN FROM 18 DUTCH SOILS

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was also concentrated onto a macroreticular resin and fractionation into three operationally defined fract...

  13. Heavy Metals (Cd, Cu, Cr, Pb and Zn) in Meretrix meretrix Roding, Water and Sediments from Estuaries in Sabah, North Borneo

    ERIC Educational Resources Information Center

    Abdullah, Mohd. Harun; Sidi, Jovita; Aris, Ahmad Zaharin

    2007-01-01

    Concentrations of heavy metals (Cd, Cu, Cr, Pb and Zn) in tissues of Meretrix meretrix Roding (M. meretrix R.), water and sediments from two estuaries were determined. One estuary is located in an urban area of Kota Kinabalu (Likas estuary) and the other in a rural district of Kota Belud (Kota Belud estuary), where both are in Sabah, North of…

  14. Distribution, mobility, and pollution assessment of Cd, Cu, Ni, Pb, Zn, and Fe in intertidal surface sediments of Sg. Puloh mangrove estuary, Malaysia.

    PubMed

    Udechukwu, Bede Emeka; Ismail, Ahmad; Zulkifli, Syaizwan Zahmir; Omar, Hishamuddin

    2015-03-01

    Sungai Puloh mangrove estuary supports a large diversity of macrobenthic organisms and provides social benefits to the local community. Recently, it became a major recipient of heavy metals originating from industries in the hinterland as a result of industrialization and urbanization. This study was conducted to evaluate mobility and pollution status of heavy metals (Cd, Cu, Ni, Pb, Zn, and Fe) in intertidal surface sediments of this area. Surface sediment samples were collected based on four different anthropogenic sources. Metals concentrations were analyzed using an atomic absorption spectrophotometer (AAS). Results revealed that the mean concentrations were Zn (1023.68 ± 762.93 μg/g), Pb (78.8 ± 49.61 μg/g), Cu (46.89 ± 43.79 μg/g), Ni (35.54 ± 10.75 μg/g), Cd (0.94 ± 0.29 μg/g), and Fe (7.14 ± 0.94%). Most of the mean values of analyzed metals were below both the interim sediment quality guidelines (ISQG-low and ISQG-high), except for Pb concentration (above ISQG-low) and Zn concentration (above ISQG-high), thus suggesting that Pb and Zn may pose some environmental concern. Cadmium, Pb, and Zn concentrations were above the threshold effect level (TEL), indicating seldom adverse effect of these metals on macrobenthic organisms. Pollution load index (PLI) indicated deterioration and other indices revealed the intertidal surface sediment is moderately polluted with Cd, Pb, and Zn. Therefore, this mangrove area requires urgent attention to mitigate further contamination. Finally, this study will contribute to data sources for Malaysia in establishing her own ISQG since it is a baseline study with detailed contamination assessment indices for surface sediment of intertidal mangrove area. PMID:25292304

  15. Heavy metal (Pb, Zn, Cd, Fe, and Cu) contents of plant foliage near the Anvil Range lead/zinc mine, Faro, Yukon Territory.

    PubMed

    Pugh, Rachel E; Dick, David G; Fredeen, Arthur L

    2002-07-01

    Mining and processing of lead (Pb)/zinc (Zn) ore at the Anvil Range mine occurred near the town of Faro in the Yukon Territory, Canada, for approximately 30 years, beginning in 1968. A study was undertaken to examine whether the mining activities had left a detectable "footprint" on the environment in the way of heavy metal phytoaccumulation. Foliage of three native plant species was sampled: bog blueberry (Vaccinium uliginosum), Labrador tea (Ledum groenlandicum), and willow (Salix sp.), at approximately 0.25, 2.5, 12, 30, and 200 (control) km distant from the mill (ore-processing facility at the mine). Foliage samples were oven-dried, wet- or dry-ashed, and analyzed for metal content using ICP-AES. In addition to Pb and Zn, the primary ore constituents, copper (Cu), iron (Fe), and cadmium (Cd), were also assayed. As expected, foliar Pb and Zn concentrations were elevated in plants at the sites closest to the mill, i.e., 0.25 and 2.5 km from the mine facility. Copper and Fe, both essential nutrients for plants, were also elevated in foliage at the sites closest to the mill, but not to a level that would be of concern. Foliar Cd levels were highest in Salix relative to the other species but were not affected by proximity to the mill. Results suggest that Ledum may be the best indicator of high environmental concentrations of Pb, while Salix may be the best indicator of elevated Zn and Cd. PMID:12297090

  16. Effect of soil properties and a synthetic municipal landfill leachate on the retention of Cd, Ni, Pb, and Zn in soil and sediment materials

    SciTech Connect

    LaBauve, J.M.; Kotuby-Amacher, J.; Gambrell, R.P.

    1988-03-01

    Batch equilibrium metal immobilization studies were conducted using seven soils and sediment materials spiked with varying concentrations of Cd, Ni, Pb, and Zn. The objective was to examine the potential mobility of metals in subsoils of metals-contaminated sites. Soil pH influenced metal immobilization more than other properties. The inclusion of other property values improved correlation of retention and concentration. Among the metals, Pb was most strongly retained, while Ni was the most mobile. The presence of a synthetic municipal landfill leachate enhanced the dissolved levels of two metals studied (Cd, Ni) in all soil materials.

  17. Cd, Cr, Cu, Pb, and Zn concentrations in Ulva lactuca, Codium fragile, Jania rubens, and Dictyota dichotoma from Rabta Bay, Jijel (Algeria).

    PubMed

    Laib, Essaid; Leghouchi, Essaid

    2012-03-01

    Concentrations of Cd, Cr, Cu, Pb, and Zn were determined in algae samples collected from the Rabta Bay in the Mediterranean Sea, Algeria. The levels of heavy metals in the macroalgae, Ulva lactuca, Codium fragile (green algae), Jania rubens (red algae), and Dictyota dichotoma (brown algae) recorded high concentrations except for Cd. Moreover, Zn was the most predominant metal in the seaweeds. The obtained HM contents indicate that different species demonstrate various degree of metal accumulation and the obtained higher values in site 1 of the studied zone can be attributed to the discharge influence of two rivers (Mouttas and Larayeche Rivers), entering the Mediterranean Sea and local pollutant emissions. The abundance of heavy metal concentrations in the macroalgae samples was found in the order below: Zn > Cu > Pb > Cr > Cd from the studied zone. The highest amounts of heavy metals in algae samples were Cd, Cu, and Pb in brown algae, and Cr and Zn in green and brown algae from the studied zone (Rabta Bay). PMID:21755430

  18. Effect of biochar on the extractability of heavy metals (Cd, Cu, Pb, and Zn) and enzyme activity in soil.

    PubMed

    Yang, Xing; Liu, Jingjing; McGrouther, Kim; Huang, Huagang; Lu, Kouping; Guo, Xi; He, Lizhi; Lin, Xiaoming; Che, Lei; Ye, Zhengqian; Wang, Hailong

    2016-01-01

    Biochar is a carbon-rich solid material derived from the pyrolysis of agricultural and forest residual biomass. Previous studies have shown that biochar is suitable as an adsorbent for soil contaminants such as heavy metals and consequently reduces their bioavailability. However, the long-term effect of different biochars on metal extractability or soil health has not been assessed. Therefore, a 1-year incubation experiment was carried out to investigate the effect of biochar produced from bamboo and rice straw (at temperatures ≥500 °C) on the heavy metal (cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn)) extractability and enzyme activity (urease, catalase, and acid phosphatase) in a contaminated sandy loam paddy soil. Three rates (0, 1, and 5%) and two mesh sizes (<0.25 and <1 mm) of biochar applications were investigated. After incubation, the physicochemical properties, extractable heavy metals, available phosphorus, and enzyme activity of soil samples were analyzed. The results demonstrated that rice straw biochar significantly (P < 0.05) increased the pH, electrical conductivity, and cation exchange capacity of the soil, especially at the 5% application rate. Both bamboo and rice straw biochar significantly (P < 0.05) decreased the concentration of CaCl2-extractable heavy metals as biochar application rate increased. The heavy metal extractability was significantly (P < 0.01) correlated with pH, water-soluble organic carbon, and available phosphorus in soil. The 5% application rate of fine rice straw biochar resulted in the greatest reductions of extractable Cu and Zn, 97.3 and 62.2%, respectively. Both bamboo and rice straw biochar were more effective at decreasing extractable Cu and Pb than removing extractable Cd and Zn from the soil. Urease activity increased by 143 and 107% after the addition of 5% coarse and fine rice straw biochars, respectively. Both bamboo and rice straw biochars significantly (P < 0.05) increased catalase

  19. Distribution of Cd, Pb, Zn and Cu and their chemical speciations in soils from a peri-smelter area in northeast China

    NASA Astrophysics Data System (ADS)

    Du, Ping; Xue, Nandong; Liu, Li; Li, Fasheng

    2008-07-01

    An exploratory study on soil contamination of heavy metals was carried out surrounding Huludao zinc smelter in Liaoning province, China. The distribution of total heavy metals and their chemical speciations were investigated. The correlations between heavy metal speciations and soil pH values in corresponding sites were also analyzed. In general, Cd, Zn, Pb, Cu and As presented a significant contamination in the area near the smelter, comparied with Environmental Quality Standards for Soils in China. The geoaccumulation index showed the degree of contamination: Cd > Zn > Pb > Cu > As. There was no obvious pollution of Cr and Ni in the studied area. The speciation analysis showed that the dominant fraction of Cd and Zn was the acid soluble fraction, and the second was the residual fraction. Pb was mostly associated with the residual fraction, which constituted more than 50% of total concentration in all samples. Cu in residual fraction accounted for a high percentage (40-80%) of total concentration, and the proportion of Cu in the oxidizable fraction is higher than that of other metals. The distribution pattern of Pb and Zn was obviously affected by soil pH. It seemed that Pb and Zn content in acid solution fraction increased with increasing soil pH values, while Cd content in acid soluble fraction accounted for more proportion in neutral and alkaline groups than acidic one. The fraction distribution patterns of Cu in three pH groups were very similar and independent of soil pH values. And the residual fraction of Cu took a predominant part (50%) of the total content.

  20. Effect of large additions of Cd, Pb, Cr, Zn, to cement raw meal on the composition and the properties of the clinker and the cement

    SciTech Connect

    Murat, M.; Sorrentino, F.

    1996-03-01

    The utilization of hydraulic binders to solidify and to stabilize industrial wastes and municipal garbage is presently recognized as one of the solutions to the problem of environment protection. Te addition of important quantities of Cd, Pb, Cr, Zn to raw meals of Portland and calcium aluminate cement modifies the mineralogical composition and the properties of the final cement. Portland cement can absorb a large amount of Cd and Zn. This absorption leads to an increase of setting time and a decrease of strengths of the cement. It also can trap chromium with a short setting time and high strengths. Calcium aluminate cements easily trap Cd and Cr with a delayed setting and good strength but also Pb with normal setting time and strengths. Large quantities of zinc oxide have a deleterious effect on calcium aluminate strengths.

  1. Immobilization of Pb, Cd, and Zn in a contaminated soil using eggshell and banana stem amendments: metal leachability and a sequential extraction study.

    PubMed

    Ashrafi, Mehrnaz; Mohamad, Sharifah; Yusoff, Ismail; Shahul Hamid, Fauziah

    2015-01-01

    Heavy-metal-contaminated soil is one of the major environmental pollution issues all over the world. In this study, two low-cost amendments, inorganic eggshell and organic banana stem, were applied to slightly alkaline soil for the purpose of in situ immobilization of Pb, Cd, and Zn. The artificially metal-contaminated soil was treated with 5% eggshell or 10% banana stem. To simulate the rainfall conditions, a metal leaching experiment for a period of 12 weeks was designed, and the total concentrations of the metals in the leachates were determined every 2 weeks. The results from the metal leaching analysis revealed that eggshell amendment generally reduced the concentrations of Pb, Cd, and Zn in the leachates, whereas banana stem amendment was effective only on the reduction of Cd concentration in the leachates. A sequential extraction analysis was carried out at the end of the experiment to find out the speciation of the heavy metals in the amended soils. Eggshell amendment notably decreased mobility of Pb, Cd, and Zn in the soil by transforming their readily available forms to less accessible fractions. Banana stem amendment also reduced exchangeable form of Cd and increased its residual form in the soil. PMID:25060308

  2. Toxic Metals (Pb and Cd) and Their Respective Antagonists (Ca and Zn) in Infant Formulas and Milk Marketed in Brasilia, Brazil

    PubMed Central

    De Castro, Clarissa S. P.; Arruda, Andréa F.; Da Cunha, Leandro R.; SouzaDe, Jurandir R.; Braga, Jez W. B.; Dórea, José G.

    2010-01-01

    In non-ideal scenarios involving partial or non-breastfeeding, cow’s milk-based dairy products are mainstream in infant feeding. Therefore, it is important to study the concentrations of potentially neurotoxic contaminants (Pb and Cd) and their respective counteracting elements (Ca and Zn) in infant dairy products. Fifty-five brands of infant formulas and milk sold in Brasilia, Brazil were analyzed. The dairy products came from areas in the central-west (26%), southeast (29%) and south of Brazil (36%) extending as far as Argentina (7%) and the Netherlands (2%). For toxic Pb and Cd, median concentrations in powdered samples were 0.109 mg/kg and 0.033 mg/kg, respectively; in fluid samples median Pb concentration was 0.084 mg/kg, but median Cd concentration was below the limit of detection and overall values were below reference safety levels. However, 62% of these samples presented higher Pb concentration values than those established by FAO/WHO. Although the inverse correlation between Cd and Zn (Spearman r = −0.116; P = 0.590) was not statistically significant, the positive correlation between Ca and Pb was (Spearman r = 0.619; P < 0.0001). Additionally, there was a significant correlation between Pb and Cd. Furthermore, the study also revealed that provision of the essential trace element Zn in infant formulas can provide adequate amounts of the recommended daily requirements. Infant formulas and milk sold for consumption by infants and children can be an efficient tool to monitor neurotoxic metal risk exposure among young children. PMID:21139877

  3. The two-phase leaching of Pb, Zn and Cd contaminated soil using EDTA and electrochemical treatment of the washing solution.

    PubMed

    Finzgar, Neza; Lestan, Domen

    2008-11-01

    The feasibility of a novel two-phase method for remediation of Pb (1374 mg kg(-1)), Zn (1007 mg kg(-1)), and Cd (9.1 mg kg(-1)) contaminated soil was evaluated. In the first phase we used EDTA for leaching heavy metals from the soil. In the second phase we used an electrochemical advanced oxidation process (EAOP) for the treatment and reuse of washing solution for soil rinsing (removal of the soil-retained, chelant-mobilized metallic species). In EAOP, a boron-doped diamond anode was used for the generation of hydroxyl radicals and oxidative decomposition of EDTA-metal complexes at a constant current density (15 mA cm(-2)). The released metals were removed from the solution by filtration as insoluble participate and by electro-deposition on the cathode. Four consecutive additions of 5.0 mm ol kg(-1) EDTA (total 20 mmol kg(-1)) removed 44% Pb, 14% Zn and 35% Cd from the soil. The mobility of the Pb, Zn and Cd (Toxicity Characteristic Leaching Procedure) left in the soil after remediation was reduced by 1.6, 3.4 and 1.5 times, respectively. The Pb oral availability (Physiologically Based Extraction Test) in the simulated stomach phase was reduced by 2.4 and in the intestinal phase by 1.7 times. The discharge solution was clear, almost colorless, with pH 7.73 and 0.47 mg L(-1) Pb, 1.03 mg L(-1) Zn, bellow the limits of quantification of Cd and 0.023 mM EDTA. The novel method enables soil leaching with small water requirements and no wastewater generation or other emissions into the environment. PMID:18762318

  4. Retention efficiency of Cd, Pb and Zn from agricultural by-products activated carbon and biochar under laboratory conditions

    NASA Astrophysics Data System (ADS)

    Coscione, Aline; Ramos, Barbara

    2015-04-01

    The immobilization of inorganic contaminants by using biochar in soils has played an increasingly important role and it is seen as an attractive alternative for the remediation of heavy metals. Although, the production of activated carbon (CA) from agricultural by-products has received special attention, the activation of the the organic source has been studied in order to increase its porposity, surface area and chemical polarity, resulting in higher adsorption of metals. Therefore, this study aimed to evaluate the effectiveness of BC and CA samples, obtained from a eucalyptus husks and cane sugar bagasse after activation with 20% phosphoric acid and pyrolyzed at 450oC in the retention of Zn, Cd and Pb using contaminated individual solutions. The experiment was performed using samples of activated carbon of eucalyptus husk (CCA), eucalyptus husk biochar (BC), activated carbon of sugar cane bagasse (CBA) and sugar cane bagasse biochar (BB) previously treated with Zn, Cd (range of tested solution from 0.1 up to 12 mmol L-1) and Pb (from 0.1 up 50 mmol L-1) which were submitted to stirring with ammonium acetate solution at pH 4.9 for 48 h. The results obtained were adjusted with Langmuir desorptiom isotherms. The pH of the resulting solution, were the meatls were analyse, was measure and remained in the range 4.9 - 5.0. The lower pH found in activated samples (range 2.4-2.5) resulted in larger desorption of metals than the biochar samples (pH of 9.7 for BC and 7.0 for BB). This result is surprising since for the biochar samples it was expected that any precipated metals were dissolved by the desorption solution in addition to metals released by ion exchange. Although the desorption results of activated samoels is still unclear, hich we belive may be explaibed by some adicitonal insterumental analysis, biochar samples showed better potential for application in contaminated soils than the previous.

  5. Modeling removal of Cd, Cu, Pb, and Zn in acidic groundwater during neutralization by ambient surface waters and groundwaters

    USGS Publications Warehouse

    Paulson, A.J.; Balistrieri, L.

    1999-01-01

    Removal of Pb, Cu, Zn, and Cd during neutralization of acid rock drainage is examined using model simulations of field conditions and laboratory experiments involving mixing of natural drainage and surface waters or groundwaters. The simulations consider sorption onto hydrous Fe and Al oxides and particulate organic carbon, mineral precipitation, and organic and inorganic solution complexation of metals for two physical systems where newly formed oxides and particulate organic matter are either transported or retained along the chemical pathway. The calculations indicate that metal removal is a strong function of the physical system. Relative to direct discharge of ARD into streams, lower metal removals are observed where ARD enters streamwaters during the latter stages of neutralization by ambient groundwater after most of the Fe has precipitated and been retained in the soils. The mixing experiments, which represent the field simulations, also demonstrated the importance of dissolved metal to particle Fe ratios in controlling dissolved metal removal along the chemical pathway. Finally, model calculations indicate that hydrous Fe oxides and particulate organic carbon are more important than hydrous Al oxides in removing metals and that both inorganic and organic complexation must be considered when modeling metal removal from aquatic systems that are impacted by sulfide oxidation.Removal of Pb, Cu, Zn, and Cd during neutralization of acid rock drainage is examined using model simulations of field conditions and laboratory experiments involving mixing of natural drainage and surface waters or groundwaters. The simulations consider sorption onto hydrous Fe and Al oxides and particulate organic carbon, mineral precipitation, and organic and inorganic solution complexation of metals for two physical systems where newly formed oxides and particulate organic matter are either transported or retained along the chemical pathway. The calculations indicate that metal

  6. Simultaneous determination of Cd(II), Cu(II), Pb(II), and Zn(II) in citrus essential oils by derivative potentiometric stripping analysis.

    PubMed

    La Pera, Lara; Saitta, Marcello; Di Bella, Giuseppa; Dugo, Giacomo

    2003-02-26

    Citrus essential oils are widely used in the food, cosmetics, and pharmaceutical industries, so the determination of heavy metals content is of great importance to guarantee their quality. The present work deals with the quantification of Cd(II), Cu(II), Pb(II), and Zn(II) in different varieties of citrus essential oils, using derivative potentiometric stripping analysis. Two different metals extraction procedures, involving concentrated hydrochloric acid treatment and acid-alcoholic dissolution, are tested on lemon, mandarin, sweet orange, and bergamot essential oils, and they give very similar results. Cd(II), Cu(II), Pb(II), and Zn(II) recovery tests spanned from 95 to 100.50%, providing evidence that metals quantification remained unaffected by the cleanup steps of the two procedures. The repeatability of the hydrochloric acid extraction method, applied on different varieties of essential oils, is >95.00% for Cd(II), Cu(II), Pb(II), and Zn(II), whereas the repeatability of the acid-alcoholic dissolution method is >93.00% for Cu and Cd only in lemon oil. Detection limits obtained for the four analytes, using both procedures, ranged from 0.10 to 0.98 ng g(-)(1) in lemon, mandarin, sweet orange, and bergamot essential oils. PMID:12590445

  7. The transfer and fate of Pb from sewage sludge amended soil in a multi-trophic food chain: a comparison with the labile elements Cd and Zn.

    PubMed

    Dar, Mudasir Irfan; Khan, Fareed Ahmad; Green, Iain D; Naikoo, Mohd Irfan

    2015-10-01

    The contamination of agroecosystems due to the presence of trace elements in commonly used agricultural materials is a serious issue. The most contaminated material is usually sewage sludge, and the sustainable use of this material within agriculture is a major concern. This study addresses a key issue in this respect, the fate of trace metals applied to soil in food chains. The work particularly addresses the transfer of Pb, which is an understudied element in this respect, and compares the transfer of Pb with two of the most labile metals, Cd and Zn. The transfer of these elements was determined from sludge-amended soils in a food chain consisting of Indian mustard (Brassica juncea), the mustard aphid (Lipaphis erysimi) and a predatory beetle (Coccinella septempunctata). The soil was amended with sludge at rates of 0, 5, 10 and 20 % (w/w). Results showed that Cd was readily transferred through the food chain until the predator trophic level. Zn was the most readily transferred element in the lower trophic levels, but transfer to aphids was effectively restricted by the plant regulating shoot concentration. Pb had the lowest level of transfer from soil to shoot and exhibited particular retention in the roots. Nevertheless, Pb concentrations were significantly increased by sludge amendment in aphids, and Pb was increasingly transferred to ladybirds as levels increased. The potential for Pb to cause secondary toxicity to organisms in higher trophic levels may have therefore been underestimated. PMID:26070738

  8. Optimization of Ultrasound-Assisted Extraction of Cr, Cu, Zn, Cd, and Pb from Sediment, Followed by FAAS and GFAAS Analysis.

    PubMed

    Mimura, Aparecida M S; Oliveira, Marcone A L; Ciminelli, Virginia S T; Silva, Julio C J

    2016-01-01

    An ultrasound method for simultaneous extraction of Cr, Cu, Zn, Cd, and Pb from sediment, and determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) was proposed. The experimental results obtained using analytical curves and the method of standard additions agreed at a confidence level of 95% for all the analytes, as determined by FAAS and GFAAS, indicating no significant matrix effects. Recoveries ranged from 80.1 to 93.7% (certified reference material) and from 89 to 107% (spike tests). The LOD and LOQ results from the method were consistent with the techniques used (FAAS and GFAAS), with high analytical throughput. The proposed method was then used to determine Cr, Cu, Zn, Cd, and Pb in river sediment samples from Rio Doce, Minas Gerais, Brazil. The results indicated levels below those permitted by Brazilian legislation for all the analytes, with the exception of Cr. PMID:26851077

  9. Behavior of Zn2+, Cd2+, Ba2+ and Pb2+ cations in ferromanganese crusts from the Marcus Wake seamount (Pacific Ocean) in aqueous solutions of metal salts

    NASA Astrophysics Data System (ADS)

    Novikov, G. V.; Bogdanova, O. Yu.; Melnikov, M. E.; Lobus, N. V.; Drozdova, A. N.; Shulga, N. A.

    2016-01-01

    The behavior of heavy-metal cations in ore minerals of cobalt-rich ferromanganese crusts from the Marcus Wake seamount in aqueous solutions of metal salts was studied in experiments. The Zn2+ and Cd2+ cations showed high reactivity and Ba2+ and Pb2+ showed low reactivity. It was found that Zn2+ and Cd2+ cations within the ore mineral composition are mainly absorbed (up to 66%) whereas Pb2+ and Ba2+ are chemically bound (up to 70%). Ore minerals in the crusts are characterized by sorption properties and high ionexchange capacity by these cations (1.94-2.62 mg-equiv/g). The capacity values by heavy-metal cations for ore minerals of the crusts from different areas of the Marcus Wake seamount are close to each other.

  10. Evaluation of the effectiveness of phosphate treatment for the remediation of mine waste soils contaminated with Cd, Cu, Pb, and Zn.

    PubMed

    Mignardi, Silvano; Corami, Alessia; Ferrini, Vincenzo

    2012-01-01

    The effectiveness of phosphate treatment for Cd, Cu, Pb, and Zn immobilization in mine waste soils was examined using batch conditions. Application of synthetic hydroxyapatite (HA) and natural phosphate rock (FAP) effectively reduced the heavy metal water solubility generally by about 84-99%. The results showed that HA was slightly superior to FAP for immobilizing heavy metals. The possible mechanisms for heavy metal immobilization in the soil involve both surface complexation of the metal ions on the phosphate grains and partial dissolution of the phosphate amendments and precipitation of heavy metal-containing phosphates. HA and FAP could significantly reduce Cd, Cu, Pb, and Zn availability in terms of water solubility in contaminated soils while minimizing soil acidification and potential risk of eutrophication associated with the application of highly soluble phosphate sources. PMID:22024096

  11. Distribution and speciation of metals (Cu, Zn, Cd, and Pb) in agricultural and non-agricultural soils near a stream upriver from the Pearl River, China.

    PubMed

    Yang, Silin; Zhou, Dequn; Yu, Huayong; Wei, Rong; Pan, Bo

    2013-06-01

    The distribution and chemical speciation of typical metals (Cu, Zn, Cd and Pb) in agricultural and non-agricultural soils were investigated in the area of Nanpan River, upstream of the Pearl River. The investigated four metals showed higher concentrations in agricultural soils than in non-agricultural soils, and the site located in factory district contained metals much higher than the other sampling sites. These observations suggested that human activities, such as water irrigation, fertilizer and pesticide applications might have a major impact on the distribution of metals. Metal speciation analysis presented that Cu, Zn and Cd were dominated by the residual fraction, while Pb was dominated by the reducible fraction. Because of the low mobility of the metals in the investigated area, no remarkable difference could be observed between upstream and downstream separated by the factory site. PMID:23466733

  12. Risk assessment for Cd, Cu, Pb and Zn in urban soils: chemical availability as the central concept.

    PubMed

    Rodrigues, S M; Cruz, N; Coelho, C; Henriques, B; Carvalho, L; Duarte, A C; Pereira, E; Römkens, Paul F A M

    2013-12-01

    To assess the geochemical reactivity and oral bioaccessibility of Cd, Cu, Pb and Zn in urban soils from the Porto area, four extractions were performed including Aqua Regia (AR; pseudototal), 0.43 M HNO3 (reactive), 0.01 M CaCl2 (available), and 0.4 M glycine at pH = 1.5, SBET method (oral bioaccessible pool). Oral bioaccessibility in urban soils was higher than in samples from rural, industrial and mining areas which is most likely related to sources of metals and parent materials of corresponding soils. The availability and reactivity were described well by non-linear Freundlich-type equations when considering differences in soil properties. The resulting empirical models are able to predict availability and reactivity and can be used to improve the accuracy of risk assessment. Furthermore, a close 1:1 relationship exists between results from the 0.43 M HNO3 method and the SBET method which substantially facilitates risk assessment procedures and reduces analytical costs. PMID:23194645

  13. Immobilization of heavy metals (Pb, Cu, Cr, Zn, Cd, Mn) in the mineral additions containing concrete composites.

    PubMed

    Giergiczny, Zbigniew; Król, Anna

    2008-12-30

    The presented work determines the level of heavy metals (Pb+2, Cu+2, Zn+2, Cr+6, Cd+2, Mn+2) immobilization in the composites produced using Ordinary Portland Cement (OPC) as well as of binders containing large amount of mineral additives in its composition-siliceous fly ash (FA), fluidized bed combustion ash (FFA) and ground granulated blast furnace slag (GGBFS). Heavy metals were introduced to cementitious materials in the form of soluble salts as well as components of hazardous wastes (medical ash, metallurgical dust). It has been stated, that the level of heavy metals immobilization is combined with composites composition. Majority of analyzed heavy metals, added to binders' composition in the form of heavy metal salts achieves high level of immobilization, in mortar based on binder with 85% GGBFS and 15% OPC. The lowest immobilization level was reached for chromium Cr+6 added to hardening mortars as Na2Cr2O72H2O. The level ranges from 85.97% in mortars made on blended binder (20% OPC, 30% FFA and 50% GGBFS) to 93.33% in mortar produced on OPC. The increase of the so-called immobilization degree with time of hardened material maturing was found. This should be attributed to the pozzolanic or pozzolanic/hydraulic properties of components used; their effect on microstructure of hardened material is also important. Mineral additions enter the hydration reactions in the mixtures and favor the formation of specific microstructure promoting the immobilization of hazardous elements. PMID:18423859

  14. Contamination by Cd, Cu, Pb, and Zn in mine wastes from abandoned metal mines classified as mineralization types in Korea.

    PubMed

    Jung, Myung Chae

    2008-06-01

    The objective of this study was to investigate heavy metal contamination and geochemical characteristics of mine wastes, including tailings, from 38 abandoned mines classified as five mineralization types. Mine waste materials including tailings and soils were sampled from the mines and the physical and chemical characteristics of the samples were analyzed. The particle size of tailings was in the range of 10-100 microm. The pH of the waste covered a wide range, from 1.73 to 8.11, and was influenced by associated minerals and elevated levels of Cd, Cu, Pb, and Zn, extracted by a Korean Standard Method (digestion with 0.1 mol L(-1) HCl), which were found in the wastes. Half of the samples contained heavy metals at levels above those stipulated by the Soil Environmental Conservation Act (SECA) in Korea. In addition, extremely high concentrations of the metals were also found in mine wastes extracted by aqua regia, especially those from mines associated with sulfide minerals. Thus, it can be expected that trace elements in mine wastes may be dispersed both downstream and downslope through water and wind. Eventually they may pose a potential health risk to residents in the vicinity of the mine. It is necessary to control mine wastes by using a proper method for their reclamation, such as neutralization of the mine wastes using a fine-grained limestone. PMID:17687627

  15. Simultaneous determination of Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ by using second-derivative spectrophotometry method

    NASA Astrophysics Data System (ADS)

    Han, Yanyan; Li, Yan; Si, Wei; Wei, Dong; Yao, Zhenxing; Zheng, Xianpeng; Du, Bin; Wei, Qin

    2011-09-01

    A new method of simultaneous determination of Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ is proposed here by using the second-derivative spectrophotometry method. In pH = 10.35 Borax-NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal-porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0-0.60, 0-0.60, 0-0.40, 0-0.80 and 0-0.48 μg mL -1 for Cu 2+, Zn 2+, Cd 2+, Hg 2+ and Pb 2+, respectively. The molar absorptivity of these color systems were 1.38 × 10 5, 1.01 × 10 5, 3.24 × 10 5, 1.07 × 10 5 and 1.29 × 10 5 L mol -1 cm -1. The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results.

  16. Sensitive electrochemical sensor using a graphene-polyaniline nanocomposite for simultaneous detection of Zn(II), Cd(II), and Pb(II).

    PubMed

    Ruecha, Nipapan; Rodthongkum, Nadnudda; Cate, David M; Volckens, John; Chailapakul, Orawon; Henry, Charles S

    2015-05-18

    This work describes the development of an electrochemical sensor for simultaneous detection of Zn(II), Cd(II), and Pb(II) using a graphene-polyaniline (G/PANI) nanocomposite electrode prepared by reverse-phase polymerization in the presence of polyvinylpyrrolidone (PVP). Two substrate materials (plastic film and filter paper) and two nanocomposite deposition methods (drop-casting and electrospraying) were investigated. Square-wave anodic stripping voltammetry currents were higher for plastic vs. paper substrates. Performance of the G/PANI nanocomposites was characterized by scanning electron microscopy (SEM) and cyclic voltammetry. The G/PANI-modified electrode exhibited high electrochemical conductivity, producing a three-fold increase in anodic peak current (vs. the unmodified electrode). The G/PANI-modified electrode also showed evidence of increased surface area under SEM. Square-wave anodic stripping voltammetry was used to measure Zn(II), Cd(II), and Pb(II) in the presence of Bi(III). A linear working range of 1-300 μg L(-1) was established between anodic current and metal ion concentration with detection limits (S/N=3) of 1.0 μg L(-1) for Zn(II), and 0.1 μg L(-1) for both Cd(II) and Pb(II). The G/PANI-modified electrode allowed selective determination of the target metals in the presence of common metal interferences including Mn(II), Cu(II), Fe(III), Fe(II), Co(III), and Ni(II). Repeat assays on the same device demonstrated good reproducibility (%RSD<11) over 10 serial runs. Finally, this system was utilized for determining Zn(II), Cd(II), and Pb(II) in human serum using the standard addition method. PMID:25910444

  17. Simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ by using second-derivative spectrophotometry method.

    PubMed

    Han, Yanyan; Li, Yan; Si, Wei; Wei, Dong; Yao, Zhenxing; Zheng, Xianpeng; Du, Bin; Wei, Qin

    2011-09-01

    A new method of simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ is proposed here by using the second-derivative spectrophotometry method. In pH=10.35 Borax-NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal-porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0-0.60, 0-0.60, 0-0.40, 0-0.80 and 0-0.48 μg mL(-1) for Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+, respectively. The molar absorptivity of these color systems were 1.38×10(5), 1.01×10(5), 3.24×10(5), 1.07×10(5) and 1.29×10(5)Lmol(-1)cm(-1). The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results. PMID:21664176

  18. Accumulation of Al, Mn, Fe, Cu, Zn, Cd and Pb by the bryophyte Scapania undulata in three upland waters of different pH.

    PubMed

    Vincent, C D; Lawlor, A J; Tipping, E

    2001-01-01

    Measurements were made of the contents of Al, Mn, Fe, Cu, Zn, Cd and Pb in Scapania undulata in three streams (D2, D5, D11) in the English Lake District. The stream waters had average pH values of 5.35 (D2), 5.81 (D5) and 7.26 (D11), the main differences in other major chemical components being in Mg, Al, Ca and alkalinity. There was generally more metal accumulation in the older parts of the plants, but this was not significant in all cases. Extents of accumulation varied with stream pH and dissolved metal concentration. For Al, accumulation was greatest in streams D2 and D5. Mn accumulated most in D5 and Fe was without preference. Cu, Zn and Cd accumulated mostly in the plants in stream D11 and Pb accumulated more in D5 and D11. In terms of enrichment factors (amount of metal in the plants divided by stream water concentration) the sequence was Zn < Cd < Cu < Mn < Pb < Al < Fe. Laboratory experiments supported the findings of the field data, providing evidence that uptake increases with pH at constant total metal concentration. The results are interpreted qualitatively in terms of the chemical speciation of the metals in the stream water and competition between metal ions and protons at the plant-water interface. It is suggested that Al, Cu, Zn, Cd and Pb behave according to chemical complexation, whereas redox processes and/or colloidal interactions may be significant for Mn and Fe. PMID:11444010

  19. Predicting the mobility of Zn, Fe, Cu, Pb, Cd from roasted sulfide (pyrite) residues -- A case study of wastes from the sulfuric acid industry in Sweden

    SciTech Connect

    Lin, Z.; Qvarfort, U.

    1996-12-31

    Leachates from roasted sulfide residues, which are the wastes from the production of sulfuric acid at Falun, Sweden, have low pH and high concentrations of Zn, Fe, and SO{sub 4}. The minerals are mainly hematite and maghemite and, because the various sulfides in the feed behave differently during the roasting process, the residual sulfides minerals are pyrrhotite and sphalerite. Oxidation of the residual sulfides contributes acidity, Zn, Fe, Cu, Cd, and sulfate to the effluents from the waste deposits. The dissolution of sphalerite is most likely accelerated in acid solution rich in Fe(III). The formation of Pb-sulfate coatings on galena may provide an armoring effect which slows the oxidation of the galena. Residual sulfides are source phases controlling long-term contaminant release. Other source minerals for Zn, Fe, Pb, Cu, Cd and SO{sub 4} in the effluents are iron oxides which retained percentage quantities of SO{sub 4}, roast-derived alteration rims of Zn oxides on sphalerite, altered silicates formed during the roasting process, and secondary minerals (e.g., Zn, Fe, Cu sulfates, iron hydroxides) that were precipitated by in-site oxidation in the waste dumps. The Zn, Fe, and Cu sulfates most likely control short-term changes in the chemistry of the leachate, while Pb concentration in the leachates may be controlled predominantly by Pb-release from the altered silicates. The mineralogical and geochemical data provide fundamental information essential for the remedial management of this type of industrial waste.

  20. Bioaccumulation and associated dietary risks of Pb, Cd, and Zn in amaranth (Amaranthus cruentus) and jute mallow (Corchorus olitorius) grown on soil irrigated using polluted water from Asa River, Nigeria.

    PubMed

    Ogunkunle, Clement Oluseye; Ziyath, Abdul M; Adewumi, Faderera Esther; Fatoba, Paul Ojo

    2015-05-01

    Dietary uptake of heavy metals through the consumption of vegetables grown on polluted soil can have serious human health implications. Thus, the study presented in this paper investigated the bioaccumulation and associated dietary risks of Pb, Zn, and Cd present in vegetables widely consumed in Nigeria, namely amaranth and jute mallow, grown on soil irrigated with polluted water from Asa River. The study found that the soil was polluted with Zn, Pb, and Cd with Pb and Cd being contributed by polluted river, while Zn was from geogenic sources. The metal concentration in amaranth and jute mallow varied in the order of Zn > Pb > Cd and Zn > Pb ≈ Cd, respectively. Jute mallow acts as an excluder plant for Pb, Cd, and Zn. Consequently, the metal concentrations in jute mallow were below the toxic threshold levels. Furthermore, non-cancer human health risk of consuming jute mallow from the study site was not significant. In contrast, the concentrations of Pb and Cd in amaranth were found to be above the recommended safe levels and to be posing human health risks. Therefore, further investigation was undertaken to identify the pathways of heavy metals to amaranth. The study found that the primary uptake pathway of Pb and Cd by amaranth is foliar route, while root uptake is the predominant pathway of Zn in amaranth. PMID:25899541

  1. Pine bark as bio-adsorbent for Cd, Cu, Ni, Pb and Zn: batch-type and stirred flow chamber experiments.

    PubMed

    Cutillas-Barreiro, L; Ansias-Manso, L; Fernández-Calviño, D; Arias-Estévez, M; Nóvoa-Muñoz, J C; Fernández-Sanjurjo, M J; Álvarez-Rodríguez, E; Núñez-Delgado, A

    2014-11-01

    The objective of this work was to determine the retention of five metals on pine bark using stirred flow and batch-type experiments. Resulting from batch-type kinetic experiments, adsorption was rapid, with no significant differences for the various contact times. Adsorption was between 98 and 99% for Pb(2+), 83-84% for Cu(2+), 78-84% for Cd(2+), 77-83% for Zn(2+), and 70-75% for Ni(2+), and it was faster for low concentrations, with Pb suffering the highest retention, followed by Cu, Cd, Ni and Zn. The fitting to the Freundlich and Langmuir models was satisfactory. Desorption increased in parallel to the added concentrations, with Pb always showing the lowest levels. Stirred flow chamber experiments showed strong hysteresis for Pb and Cu, sorption being mostly irreversible. The differences affecting the studied heavy metals are mainly due to different affinity for the adsorption sites. Pine bark can be used to effectively remove Pb and Cu from polluted environments. PMID:24973614

  2. Molecular beam epitaxy and characterizations of PbTe grown on GaAs(211) substrates using CdTe/ZnTe buffers

    NASA Astrophysics Data System (ADS)

    Shu, Tianyu; Lu, Pengqi; Zhang, Bingpo; Wang, Miao; Chen, Lu; Fu, Xiangliang; Xu, Gangyi; Wu, Huizhen

    2015-06-01

    Narrow-gap semiconductor PbTe has exhibited versatility in both mid-infrared optoelelctronics and thermoelectrics. However, the absence of commercially obtainable PbTe crystal substrates limits its wide applications. In this paper, heteroepitaxy of high-quality PbTe crystal on GaAs(211) using CdTe/ZnTe buffers by molecular beam epitaxy is presented for the first time. Optimal growth parameters have been obtained by both in-situ and ex-situ characterizations. In-situ reflection high-energy electron diffraction observed a transition of growth mode from 2D to 3D, which is in agreement with the results of atomic force microscope and scanning electron microscope characterizations. High resolution X-ray diffraction revealed that the growth of PbTe crystal is along [531] direction which is different from the [211] substrate orientation. Multiple phonon modes related to PbTe were observed by Raman scattering while mid-infrared light emission from epitaxial PbTe is observed at a peak of 3.5 μm by photoluminescence. Different from PbTe grown on BaF2(111), n-type conductivity with electron densities of ~5×1017 cm-3 and mobilities of 675 cm2/V s at room temperature and 4300 cm2/V s at 2 K is observed. The high quality PbTe grown on GaAs(211) substrates using CdTe/ZnTe buffers renders promising applications in both optoelectronics and thermoelectrics.

  3. Predicting the solubility and lability of Zn, Cd, and Pb in soils from a minespoil-contaminated catchment by stable isotopic exchange

    NASA Astrophysics Data System (ADS)

    Marzouk, E. R.; Chenery, S. R.; Young, S. D.

    2013-12-01

    The Rookhope catchment of Weardale, England, has a diverse legacy of contaminated soils due to extensive lead mining activity over four centuries. We measured the isotopically exchangeable content of Pb, Cd and Zn (E-values) in a large representative subset of the catchment soils (n = 246) using stable isotope dilution. All three metals displayed a wide range of %E-values (c. 1-100%) but relative lability followed the sequence Cd > Pb > Zn. A refinement of the stable isotope dilution approach also enabled detection of non-reactive metal contained within suspended sub-micron (<0.22 μm) colloidal particles (SCP-metal). For most soils, the presence of non-labile SCP-metal caused only minor over-estimation of E-values (<2%) but the effect was greater for soils with particularly large humus or carbonate contents. Approximately 80%, 53% and 66% of the variability in Zn, Cd and Pb %E-values (respectively) could be explained by pH, loss on ignition and total metal content. E-values were affected by the presence of ore minerals at high metal contents leading to an inconsistent trend in the relationship between %E-value and soil metal concentration. Metal solubility, in the soil suspensions used to measure E-values, was predicted using the WHAM geochemical speciation model (versions VI and VII). The use of total and isotopically exchangeable metal as alternative input variables was compared; the latter provided significantly better predictions of solubility, especially in the case of Zn. Lead solubility was less well predicted by either version of WHAM, with over-prediction at low pH and under-prediction at high soil pH values. Quantify the isotopically exchangeable fractions of Zn, Cd and Pb (E-values), and assess their local and regional variability, using multi-element stable isotope dilution, in a diverse range of soil ecosystems within the catchment of an old Pb/Zn mining area. Assess the controlling influences of soil properties on metal lability and develop

  4. Chemical speciation of Fe, Mn, Pb, Zn, Cd, Cu, Co, Ni and Cr in the suspended particulate matter off the Mejerda River Delta (Gulf of Tunis, Tunisia)

    NASA Astrophysics Data System (ADS)

    Helali, Mohamed Amine; Oueslati, Walid; Zaaboub, Noureddine; Added, Ayed; Aleya, Lotfi

    2016-06-01

    Fluxes of suspended particulate matter (SPM) and their associated metals were performed off the Mejerda River Delta during both the wet (March) and the dry (July) seasons in 2012, using sediment traps at study stations at depths of 10, 20 and 40 m. Fluxes nearest to the Mejerda outlet were more significant, especially during winter (36 g m-2 day-1), but dissipated further offshore, 24.5-6 g m-2 day-1 at the 20 m and 21.8-4.8 g m-2 day-1 at the 40 m stations. Many variations observed in seasonal and spatial metal fluxes are similar to those of SPM, in particular Pb and Zn, probably because they are associated with the mining activity characteristic of the Mejerda catchment. Chemical speciation reveals that most of the metals (20-100%) are bound to the residual fraction. The most toxic metals (Pb, Zn) are bound in part to the exchangeable fraction (20-50% for Pb and 5-15% for Zn) making them relatively bioavailable and therefore potentially toxic. While Cu and Cd fluxes are not always clearly established according to season, both metals are apparently sequestered deep in the sediment, bound especially to clays (40-80% for Cd and up to 100% for Cu).

  5. [Uptake effect of Cd and Pb by rape under single Cd/Pb and Cd-Pb combined stress].

    PubMed

    Wu, Wen-Fei; Nan, Zhong-Ren; Wang, Sheng-Li; Zhao, Zhuan-Jun; Zhou, Ting

    2012-09-01

    This paper investigated the effects of single Cd/Pb and Cd-Pb combined pollution of desert grey soils from the oasis regions on the uptake and translocation of Cd and Pb by rape (Brassica campestris L.), and analyzed the interaction between Cd and Pb. The results of pot experiment showed that the concentration of Cd or Pb was promoted when the concentration of Cd in soil was less than 7.0 mg x kg(-1) and the concentration of Pb in soil was less than 1 500 mg x kg(-1) in single Cd/Pb and Cd-Pb combined pollution. There was an obvious antagonism between Cd and Pb in Cd-Pb combined pollution. As the concentration of Cd in soil increased in single Cd pollution, the enrichment and translocation ability of Cd in rape was firstly improved and then reduced. As the concentration of Pb in soil increased in single Pb pollution, the enrichment and translocation ability of Pb in rape was reduced continuously. The Cd-Pb combined stress reduced the enrichment capacity of Cd and Pb as well as the migration ability of Pb, but improved the migration ability of Cd. The enrichment and translocation ability of Cd was greater than that of Pb. Models of uptake and translocation of Cd and Pb in rape under single Cd/Pb and Cd-Pb combined stress were both well fitted to quadratic equations. PMID:23243889

  6. Removal Efficiency of the Heavy Metals Zn(II), Pb(II) and Cd(II) by Saprolegnia delica and Trichoderma viride at Different pH Values and Temperature Degrees

    PubMed Central

    Hashem, Mohamed

    2007-01-01

    The removal efficiency of the heavy metals Zn, Pb and Cd by the zoosporic fungal species Saprolegnia delica and the terrestrial fungus Trichoderma viride, isolated from polluted water drainages in the Delta of Nile in Egypt, as affected by various ranges of pH values and different temperature degrees,was extensively investigated. The maximum removal efficiency of S. delica for Zn(II) and Cd(II) was obtained at pH 8 and for Pb(II) was at pH 6 whilst the removal efficiency of T. viride was found to be optimum at pH 6 for the three applied heavy metals. Regardless the median lethal doses of the three heavy metals, Zn recorded the highest bioaccumulation potency by S. delica at all pH values except at pH 4, followed by Pb whereas Cd showed the lowest removal potency by the fungal species and vice versa in case of T. viride. The optimum biomass dry weight production by S. delica was found when the fungus was grown in the medium treated with the heavy metal Pb at pH 6, followed by Zn at pH 8 and Cd at pH 8. The optimum biomass dry weight yield by T. viride amended with Zn,Pb and Cd was obtained at pH 6 for the three heavy metals with the maximum value at Zn. The highest yield of biomass dry weight was found when T. viride treated with Cd at all different pH values followed by Pb whilst Zn output was the lowest and this result was reversed in case of S. delica. The maximum removal efficiency and the biomass dry weight production for the three tested heavy metals was obtained at the incubation temperature 20℃ in case of S. delica while it was 25℃ for T. viride. Incubation of T. viride at higher temperatures (30℃ and 35℃) enhanced the removal efficiency of Pb and Cd than low temperatures (15℃ and 20℃) and vice versa in case of Zn removal. At all tested incubation temperatures, the maximum yield of biomass dry weight was attained at Zn treatment by the two tested fungal species. The bioaccumulation potency of S. delica for Zn was higher than that for Pb at all

  7. Impact of temperature on the dynamics of organic matter and on the soil-to-plant transfer of Cd, Zn and Pb in a contaminated agricultural soil.

    PubMed

    Cornu, Jean-Yves; Denaix, L; Lacoste, J; Sappin-Didier, V; Nguyen, C; Schneider, A

    2016-02-01

    Predicting the soil-to-plant transfer of metals in the context of global warming has become a major issue for food safety. It requires a better understanding of how the temperature alters the bioavailability of metals in cultivated soils. This study focuses on one agricultural soil contaminated by Cd, Zn and Pb. DGT measurements were performed at 10, 20 and 30 °C to assess how the bioavailability of metals was affected by a rise in soil temperature. A lettuce crop was cultivated in the same conditions to determine if the soil-to-plant transfer of metals increased with a rise in soil temperature. A gradual decline in Cd and Zn bioavailability was observed from 10 to 30 °C, which was attributed to more intense complexation of metals in the pore water at higher temperatures. Together with its aromaticity, the affinity of dissolved organic matter (DOM) for metals was indeed suspected to increase with soil temperature. One main output of the present work is a model which satisfactorily explains the thermal-induced changes in the characteristics of DOM reported in Cornu et al. (Geoderma 162:65-70, 2011) by assuming that the mineralization of initial aliphatic compounds followed a first-order reaction, increased with soil temperature according to the Arrhenius law, and due to a priming effect, led to the appearance of aromatic molecules. The soil-to-plant transfer of Cd and Zn was promoted at higher soil temperatures despite a parallel decrease in Cd and Zn bioavailability. This suggests that plant processes affect the soil-to-plant transfer of Cd and Zn the most when the soil temperature rises. PMID:26452657

  8. Pb8M(BO3)6 (M = Zn, Cd): Two new isostructural lead borates compounds with two-dimensional ∞[Pb8B6O18]2- layer structure

    NASA Astrophysics Data System (ADS)

    Huang, Zhenjun; Pan, Shilie; Yang, Zhihua; Yu, Hongwei; Dong, Xiaoyu; Zhao, Wenwu; Dong, Lingyun; Su, Xin

    2013-01-01

    Single crystals of Pb8M(BO3)6 (M = Zn, Cd) have been successfully synthesized by high temperature solution method and their structures are determined by single-crystal X-ray diffraction methods. The compounds crystallize in the trigonal space group R3¯ (No. 148) with unit-cell parameters a = 9.505(6) Å, c = 18.162(9) Å, V = 1421(2) Å3 for the Zn compound and a = 9.5584(16) Å, c = 18.670(3) Å, V = 1477.2(6) Å3 for the Cd compound. Both of the materials represent a new two-dimensional (2D) ∞[Pb8B6O18]2- layer, which is composed of BO3 and PbOx (x = 4, 6) polyhedra. The layers are further bridged by the M2+ (Zn2+, Cd2+) ions, giving rise to a three-dimensional (3D) framework. Thermal analysis, IR spectroscopy, UV-Vis-NIR diffuse reflectance spectra, and band structure calculations are performed on the reported compounds.

  9. Predicting As, Cd, Cu, Pb and Zn levels in grasses (Agrostis sp. and Poa sp.) and stinging nettle (Urtica dioica) applying soil-plant transfer models.

    PubMed

    Boshoff, Magdalena; De Jonge, Maarten; Scheifler, Renaud; Bervoets, Lieven

    2014-09-15

    The aim of this study was to derive regression-based soil-plant models to predict and compare metal(loid) (i.e. As, Cd, Cu, Pb and Zn) concentrations in plants (grass Agrostis sp./Poa sp. and nettle Urtica dioica L.) among sites with a wide range of metal pollution and a wide variation in soil properties. Regression models were based on the pseudo total (aqua-regia) and exchangeable (0.01 M CaCl2) soil metal concentrations. Plant metal concentrations were best explained by the pseudo total soil metal concentrations in combination with soil properties. The most important soil property that influenced U. dioica metal concentrations was the clay content, while for grass organic matter (OM) and pH affected the As (OM) and Cu and Zn (pH). In this study multiple linear regression models proved functional in predicting metal accumulation in plants on a regional scale. With the proposed models based on the pseudo total metal concentration, the percentage of variation explained for the metals As, Cd, Cu, Pb and Zn were 0.56%, 0.47%, 0.59%, 0.61%, 0.30% in nettle and 0.46%, 0.38%, 0.27%, 0.50%, 0.28% in grass. PMID:25000582

  10. Nonequilibrium leaching behavior of metallic elements (Cu, Zn, As, Cd, and Pb) from soils collected from long-term abandoned mine sites.

    PubMed

    Kim, Juhee; Hyun, Seunghun

    2015-09-01

    Leaching of metallic elements (Cu, Zn, As, Cd, and Pb) from two mine-impacted soils (DY and BS) was evaluated by batch decant-refill and seepage flow experiments. During eight consecutive leaching steps, aqueous As concentrations remained relatively constant (approx. 1.6 and 0.1 mg L(-)(1) for DY and BS, respectively), while Cu (0.01-3.2 mg L(-1)), Zn (0.2-42 mg L(-1)), and Cd (0.004-0.3 mg L(-1)) were quickly reduced. The reduction of Pb concentration (0.007-0.02 mg L(-1) and 0.2-0.9 mg L(-1) for DY and BS, respectively) was much lesser. This pattern was well-explained by the biphasic leaching model by allocating a large fast leaching fraction (ffast>0.2) for Cu, Zn, and Cd while a negligible ffast for As and Pb (<0.001). For all elements in column effluents, mass export through first-flush and steady-state concentration were elevated under slow seepage, with the greatest impact observed for As. Element export was enhanced after flow interruption, especially under fast seepage. A transient drop in As export in slow seepage was likely due to sorption back to soil phase during the quiescent period. The ratio of Fe(2+)/Fe(3+) and SO4(2-) concentration, related to the dissolution of sulfide minerals, were also seepage rate-dependent. The results of batch and column studies imply that the leachate concentration will be enhanced by initial seepage and will be perturbed after quiescent wetting period. The conversion from kinetically leachable pool to readily leachable pool is likely responsible for nonequilibrium metal leaching from the long-term abandoned mine soils. PMID:25935604

  11. Assessment of metal pollution in a former mining area in the NW Tunisia: spatial distribution and fraction of Cd, Pb and Zn in soil.

    PubMed

    Othmani, Mohamed Ali; Souissi, Fouad; Durães, Nuno; Abdelkader, Moussi; da Silva, Eduardo Ferreira

    2015-08-01

    This study aims to evaluate the impact of the former mining Touiref district (NW Tunisia) on the spatial distribution of metal contamination. In order to characterize the metal content of the tailings and to assess how far the soils from the district could be impacted by metals, a sampling campaign was conducted. According to the spatial distribution concentration maps of potential toxic elements (PTE), the highest concentrations occur near the flotation tailings and in mining facilities and decrease abruptly with distance. These results confirm that wind is the main agent capable of dispersing metals in a W-E direction, with concentrations exceeding the standards of soil quality for Cd, Pb and Zn over several hundred metres away from the source, facilitated by the small-size fraction and low cohesion of tailings particles. Chemical fractionation showed that Pb and Cd were mainly associated with the acid-soluble fraction (carbonates) and Fe-(oxy) hydroxides, while Zn was mainly associated with Fe-(oxy) hydroxides but also with sulphides. Thus, the immobilization of metals in solution may be favoured by the alkaline conditions, promoted by carbonates dissolution. However, being carbonate important-bearing phases of Cd and Pb (but also for Zn), the dissolution facility of these minerals may enhance the release of metals, particularly far away from the mine where the physicochemical conditions can be different. Also, the metal uptake by plants in these alkaline conditions may be favoured, especially if secondary phases with high sorption ability are reduced at this site. A remediation plan to this area is needed, with particularly attention in the confinement of the tailings. PMID:26205279

  12. Analysis of Zn, Cd, As, Cu, Pb, and Fe in snails as bioindicators and soil samples near traffic road by ICP-OES.

    PubMed

    Massadeh, Adnan M; Alomary, Ahmed A; Mir, Sayeeda; Momani, Fouad A; Haddad, Hazem I; Hadad, Yazen A

    2016-07-01

    Snails are used as biological indicators of the environment pollution for heavy metals. Living snail samples were collected from different sites at the city of Irbid-Jordan and classified according to their morphological features including Helix pelasga, Eobania vermiculata, Xeropicta derbentina, Oychilus, Xerocrassa seetzenii, Xerocrassa simulata, and Pila. Zn, Cd, As, Cu, Pb, and Fe levels were measured by inductively coupled plasma-optical emission spectroscopy. Results indicated that metal concentrations in all snail shell samples were with an average and range for Zn 22.4 (6.5-105.5) μg g(-1), Cd 7.8 (0.4-48.1) μg g(-1), As 25.9 (0.7-248.5) μg g(-1), Cu 15.1 (1.6-69.0) μg g(-1), Pb 0.4 (0.2-1.7) μg g(-1), and Fe 119.6 (14.0-1102.0) μg g(-1), whereas, in soil samples, the average and range for Zn 204.0 (12.0-709.0) μg g(-1), Cd 5.7 (0.2-39.5) μg g(-1), As 3.2 (1.8-5.2) μg g(-1), Cu 22.1 (2.3-77.4) μg g(-1), Pb 0.2 (0.1-0.3) μg g(-1), and Fe 242.4 (25.0-680.0) μg g(-1). PMID:27026544

  13. Can the byssus of green-lipped mussel Perna viridis (Linnaeus) from the west coast of Peninsular Malaysia be a biomonitoring organ for Cd, Pb and Zn? Field and laboratory studies.

    PubMed

    Yap, C K; Ismail, A; Tan, S G

    2003-07-01

    Concentrations of cadmium (Cd), lead (Pb) and zinc (Zn) in total soft tissues (ST) and byssus (BYS) of the green-lipped mussel Perna viridis from 11 different geographical locations off the west coast of Peninsular Malaysia were determined. The metal concentrations distributed between the BYS and ST were compared. The results of this study indicated that higher levels of Cd (1.31 microg/g), Pb (38.49 microg/g) and Zn (206.52 microg/g) were accumulated in the BYS than in the total ST (Cd: 0.29 microg/g; Pb: 8.27 microg/g; Zn: 102.6 microg/g). Semi-static and short period controlled laboratory experiments were also conducted for the accumulation and depuration of Cd, Pb and Zn in the total ST and BYS of P. viridis. The ratios (BYS/ST) for Pb and Cd from the laboratory experiments showed that the total ST accumulated more metals than the BYS. Therefore, these laboratory results disagreed with those found for the field samples. However, the laboratory results for the Zn ratio (BYS/ST) agreed with those of the field samples. It was evident that when compared to the ST, the BYS was a more sensitive biomonitoring organ for Zn while it could be a complementary organ for Cd and Pb in the total ST. Since total ST of P. viridis had been reported to have regulative mechanism for Zn, its BYS can be used as a biomonitoring organ for the identification of coastal areas exposed to Zn pollution. PMID:12705949

  14. Comparative study of the bioaccumulation and elimination of trace metals (Cd, Pb, Zn, Mn and Fe) in the digestive gland, gills and muscle of bivalve Pinna nobilis during a field transplant experiment.

    PubMed

    Jebali, Jamel; Chouba, Lassaad; Banni, Mohamed; Boussetta, Hamadi

    2014-04-01

    The purpose of this study was to investigate the long-term bioaccumulation and elimination of Cd, Pb, Mn, Zn and Fe by Pinna nobilis tissues after their 90 day-transplantation period at Téboulba fishing harbor. During the transplantation period, the Cd, Pb, Mn, Zn and Fe concentrations in the different tissues of the mussels were measured before and after exposure period. Metal (Cd, Pb, Mn, Zn and Fe) accumulation in P. nobilis mussels varied depending on the analyzed tissue and the caging times. Notable differences in Cd, Pb, Mn, Zn and Fe accumulation patterns within the digestive gland, gills and muscle were found and may be due to the ability of each tissue to accumulate metals. During the depuration phase, the elimination of Cd, Pb, Mn, Zn and Fe depended on the target tissue and the metal speciation. Cd, Pb, Mn and Fe were eliminated rapidly from one organ and increased in other when compared to those of 90 day transplanted mussels. The increase of metal loads during the elimination phase is not clear and particularly what kind of processes is responsible for such response. However, it is reasonable to assume that metals increase is related to the existence of an accumulation/detoxification mechanism, which involves the transport of metals from an organ to another. The data obtained indicate that because of the significantly high quantities of Cd, Pb, Mn, Zn and Fe accumulated during the exposure phase, the transplanted mussels are suitable bioindicators for monitoring trace metals in marine ecosystem. PMID:24439521

  15. Correlations between speciation of Cd, Cu, Pb And Zn in sediment and their concentrations in total soft tissue of green-lipped mussel Perna viridis from the west coast of Peninsular Malaysia.

    PubMed

    Yap, C K; Ismail, A; Tan, S G; Omar, H

    2002-04-01

    Total concentrations and speciation of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in surface sediment samples were correlated with the respective metal measured in the total soft tissue of the green-lipped mussel Perna viridis, collected from water off the west coast of Peninsular Malaysia. The aim of this study is to relate the possible differences in the accumulation patterns of the heavy metals in P. viridis to those in the surface sediment. The sequential extraction technique was employed to fractionate the sediment into 'freely leachable and exchangeable' (EFLE), 'acid-reducible,' 'oxidisable-organic' and 'resistant' fractions. The results showed that significant (P<.05) correlations were observed between Cd in P. viridis and Cd in the sediment (EFLE fraction and total Cd), Cu in P viridis and Cu in the sediment (EFLE and 'acid-reducible' fractions and total Cu) and Pb in P viridis and Pb in the sediment ('oxidisable-organic' fraction and total Pb). No significant correlation (P > .05) was found between Zn in P viridis and all the sediment geochemical fractions of Zn and total Zn in the sediment. This indicated that Zn was possibly regulated from the soft tissue of P. viridis. The present results supported the use of P viridis as a suitable biomonitoring agent for Cd, Cu and Pb. PMID:12046948

  16. Characterization of Cd-, Pb-, Zn-resistant endophytic Lasiodiplodia sp. MXSF31 from metal accumulating Portulaca oleracea and its potential in promoting the growth of rape in metal-contaminated soils.

    PubMed

    Deng, Zujun; Zhang, Renduo; Shi, Yang; Hu, Li'ao; Tan, Hongming; Cao, Lixiang

    2014-02-01

    The aim of this study was to characterize the features of a Cd-, Pb-, and Zn-resistant endophytic fungus Lasiodiplodia sp. MXSF31 and to investigate the potential of MXSF31 to remove metals from contaminated water and soils. The endophytic fungus was isolated from the stem of Portulaca oleracea growing in metal-contaminated soils. The maximum biosorption capacities of MXSF31 were 3.0 × 10(3), 1.1 × 10(4), and 1.3 × 10(4) mg kg(-1) for Cd, Pb, and Zn, respectively. The biosorption processes of Cd, Pb, and Zn by MXSF31 were well characterized with the pseudo-second-order kinetic model. The biosorption isotherm processes of Pb and Zn by the fungus were fitted better with the Langmuir model, while the biosorption processes of Cd was better fitted with the Freundlich model. The biosorption process of MXSF31 was attributed to the functional groups of hydroxyl, amino, carbonyl, and benzene ring on the cell wall. The active biomass of the strain removed more Cd, Pb, and Zn (4.6 × 10(4), 5.6 × 10(5), and 7.0 × 10(4) mg kg(-1), respectively) than the dead biomass. The inoculation of MXSF31 increased the biomass of rape (Brassica napus L.), the translocation factor of Cd, and the extraction amount of Cd by rape in the Cd+Pb-contaminated soils. The results indicated that the endophytic fungus strain had the potential to remove heavy metals from water and soils contaminated by multiple heavy metals, and plants accumulating multiple metals might harbor diverse fungi suitable for bioremediation of contaminated media. PMID:24062066

  17. Accumulation of Trace Metal Elements (Cu, Zn, Cd, and Pb) in Surface Sediment via Decomposed Seagrass Leaves: A Mesocosm Experiment Using Zostera marina L.

    PubMed Central

    Konuma, Susumu; Nakamura, Yoshiyuki

    2016-01-01

    Accumulation of Cu, Zn, Cd, and Pb in the sediment of seagrass ecosystems was examined using mesocosm experiments containing Zostera marina (eelgrass) and reference pools. Lead was approximately 20-fold higher in the surface sediment in the eelgrass pool than in eelgrass leaves and epiphytes on the eelgrass leaves, whereas zinc and cadmium were significantly lower in the surface sediment than in the leaves, with intermediate concentrations in epiphytes. Copper concentrations were similar in both the surface sediment and leaves but significantly lower in epiphytes. Carbon and nitrogen contents increased significantly with increasing δ13C in surface sediments of both the eelgrass and reference pools. Copper, Zn, Cd, and Pb also increased significantly with increasing δ13C in the surface sediment in the eelgrass pool but not in the reference pool. By decomposition of eelgrass leaves with epiphytes, which was examined in the eelgrass pool, copper and lead concentrations increased more than 2-fold and approximately a 10-fold, whereas zinc and cadmium concentrations decreased. The high copper and lead concentrations in the surface sediment result from accumulation in decomposed, shed leaves, whereas zinc and cadmium remobilized from decomposed shed leaves but may remain at higher concentrations in the leaves than in the original sediments. The results of our mesocosm study demonstrate that whether the accumulation or remobilization of trace metals during the decomposition of seagrass leaves is trace metal dependent, and that the decomposed seagrass leaves can cause copper and lead accumulation in sediments in seagrass ecosystems. PMID:27336306

  18. Effect of EDTA, EDDS, NTA and citric acid on electrokinetic remediation of As, Cd, Cr, Cu, Ni, Pb and Zn contaminated dredged marine sediment.

    PubMed

    Song, Yue; Ammami, Mohamed-Tahar; Benamar, Ahmed; Mezazigh, Salim; Wang, Huaqing

    2016-06-01

    In recent years, electrokinetic (EK) remediation method has been widely considered to remove metal pollutants from contaminated dredged sediments. Chelating agents are used as electrolyte solutions to increase metal mobility. This study aims to investigate heavy metal (HM) (As, Cd, Cr, Cu, Ni, Pb and Zn) mobility by assessing the effect of different chelating agents (ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS), nitrilotriacetic acid (NTA) or citric acid (CA)) in enhancing EK remediation efficiency. The results show that, for the same concentration (0.1 mol L(-1)), EDTA is more suitable to enhance removal of Ni (52.8 %), Pb (60.1 %) and Zn (34.9 %). EDDS provides effectiveness to increase Cu removal efficiency (52 %), while EDTA and EDDS have a similar enhancement removal effect on As EK remediation (30.5∼31.3 %). CA is more suitable to enhance Cd removal (40.2 %). Similar Cr removal efficiency was provided by EK remediation tests (35.6∼43.5 %). In the migration of metal-chelate complexes being directed towards the anode, metals are accumulated in the middle sections of the sediment matrix for the tests performed with EDTA, NTA and CA. But, low accumulation of metal contamination in the sediment was observed in the test using EDDS. PMID:26782321

  19. Corrosion Behavior of Alloy 625 in PbSO4-Pb3O4-PbCl2-ZnO-10 Wt Pct CdO Molten Salt Medium

    NASA Astrophysics Data System (ADS)

    Mohammadi Zahrani, E.; Alfantazi, A. M.

    2012-08-01

    Corrosion behavior and degradation mechanisms of alloy 625 under a 47.288 PbSO4-12.776 Pb3O4-6.844PbCl2-23.108ZnO-10CdO (wt pct) molten salt mixture under air atmosphere were studied at 873 K, 973 K, and 1073 K (600 °C, 700 °C, and 800 °C). Electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) measurements, and potentiodynamic polarization techniques were used to evaluate the degradation mechanisms and characterize the corrosion behavior of the alloy. Morphology, chemical composition, and phase structure of the corrosion products and surface layers of the corroded specimens were studied by scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) and X-ray map analyses. Results confirmed that during the exposure of alloy 625 to the molten salt, chromium was mainly dissolved through an active oxidation process as CrO3, Cr2O3, and CrNbO4, while nickel dissolved only as NiO in the system. Formation of a porous and nonprotective oxide layer with low resistance is responsible for the weak protective properties of the barrier layer at high temperatures of 973 K and 1073 K (700 °C and 800 °C). There were two kinds of attack for INCONEL 625, including general surface corrosion and pitting. Pitting corrosion occurred due to the breakdown of the initial oxide layer by molten salt dissolution of the oxide or oxide cracking.

  20. Flowing Liquid Anode Atmospheric Pressure Glow Discharge as an Excitation Source for Optical Emission Spectrometry with the Improved Detectability of Ag, Cd, Hg, Pb, Tl, and Zn.

    PubMed

    Greda, Krzysztof; Swiderski, Krzysztof; Jamroz, Piotr; Pohl, Pawel

    2016-09-01

    A novel atmospheric pressure glow discharge generated in contact with a flowing liquid anode (FLA-APGD) was developed as the efficient excitation source for the optical emission spectrometry (OES) detection. Differences in the appearance and the electrical characteristic of the FLA-APGD and a conventional system operated with a flowing liquid cathode (FLC-APGD) were studied in detail and discussed. Under the optimal operating conditions for the FLA-APGD, the emission from the analytes (Ag, Cd, Hg, Pb, Tl, and Zn) was from 20 to 120 times higher as compared to the FLC-APGD. Limits of detections (LODs) established with a novel FLA-APGD system were on average 20 times better than those obtained for the FLC-APGD. A further improvement of the LODs was achieved by reducing the background shift interferences and, as a result, the LODs for Ag, Cd, Hg, Pb, Tl, and Zn were 0.004, 0.040, 0.70, 1.7, 0.035, and 0.45 μg L(-1), respectively. The precision of the FLA-APGD-OES method was evaluated to be within 2-5% (as the relative standard deviation of the repeated measurements). The method found its application in the determination of the content of Ag, Cd, Hg, Pb, Tl, and Zn in a certified reference material (CRM) of Lobster hepatopancreas (TORT-2), four brass samples as well as mineral water and tea leaves samples spiked with the analytes. In the case of brass samples, a reference method, i.e., inductively coupled plasma optical emission spectrometry (ICP-OES) was used. A good agreement between the results obtained with FLA-APGD-OES and the certified values for the CRM TORT-2 as well as the reference values obtained with ICP-OES for the brass samples was revealed, indicating the good accuracy of the proposed method. The recoveries obtained for the spiked samples of mineral water and tea leaves were within the range of 97.5-102%. PMID:27476678

  1. Historical perspective of heavy metals contamination (Cd, Cr, Cu, Hg, Pb, Zn) in the Seine River basin (France) following a DPSIR approach (1950-2005).

    PubMed

    Meybeck, Michel; Lestel, Laurence; Bonté, Philippe; Moilleron, Régis; Colin, Jean Louis; Rousselot, Olivier; Hervé, Daniel; de Pontevès, Claire; Grosbois, Cécile; Thévenot, Daniel R

    2007-04-01

    The Driver-Pressures-State-Impact-Response approach is applied to heavy metals in the Seine River catchment (65,000 km(2); 14 million people of which 10 million are aggregated within Paris megacity; 30% of French industrial and agricultural production). The contamination pattern at river mouth is established on the particulate material at different time scales: 1930-2000 for floodplain cores, 1980-2003 for suspended particulate matter (SPM) and bed-sediments, 1994-2003 for atmospheric fallout and annual flood deposits. The Seine has been among the most contaminated catchments with maximum contents recorded at 130 mg kg(-1) for Cd, 24 for Hg, 558 for Pb, 1620 for Zn, 347 for Cu, 275 for Cr and 150 for Ni. Today, the average levels for Cd (1.8 mg kg(-1)), Hg (1.08), Pb (108), Zn (370), Cu (99), Cr (123) and Ni (31) are much lower but still in the upper 90% of the global scale distribution (Cr and Ni excepted) and well above the natural background values determined on pre-historical deposits. All metal contents have decreased at least since 1955/65, well before metal emission regulations that started in the mid 1970's and the metal monitoring in the catchment that started in the early 1980's. In the last 20 y, major criteria changes for the management of contaminated particulates (treated urban sludge, agricultural soils, dredged sediments) have occurred. In the mid 1990's, there was a complete shift in the contamination assessment scales, from sediment management and water usage criteria to the good ecological state, now required by the 2000 European Directive. When comparing excess metal outputs, associated to river SPM, to the average metal demand within the catchment from 1950 to 2000, the leakage ratios decrease exponentially from 1950 to 2000 for Cd, Cr, Cu, Pb and Zn, meanwhile, a general increase of the demand is observed: the rate of recycling and/or treatment of metals within the anthroposphere has been improved ten-fold. Hg environmental trajectory is very

  2. Atmospheric concentrations and size distributions of aircraft-sampled Cd, Cu, Pb and Zn over the southern bight of the North Sea

    NASA Astrophysics Data System (ADS)

    Injuk, J.; Otten, Ph.; Laane, R.; Maenhaut, W.; Van Grieken, R.

    In an effort to assess the atmospheric input of heavy metals to the Southern Bight of the North Sea, aircraft-based aerosol samplings in the lower troposphere were performed between September 1988 and October 1989. Total atmospheric particulate and size-differentiated concentrations of Cd, Cu, Pb and Zn were determined as a function of altitude, wind direction, air-mass history and season. The obtained data are compared with results of ship-based measurements carried out previously and with literature values of Cu, Pb and Zn, for the marine troposphere of the southern North Sea. The results point out the high variability of the concentrations with the meterological conditions, as well as with time and location. The experimentally found particle size distribution are bimodal with a significant difference in fractions of small and large particles. These large aerosol particles have a direct and essential impact on the air-to-sea transfer of anthropogenic trace metals, in spite of their low numerical abundance and relatively low heavy metal content.

  3. Chemical fractionation of Cu, Zn, Cd, Cr, and Pb in sewage sludge amended soils at the end of 65-d sorghum-sudan grass growth.

    PubMed

    Sivapatham, Paramasivam; Lettimore, Jon M; Alva, Ashok K; Jayaraman, Kuppuswamy; Harper, Legia M

    2014-09-19

    Heavy metals are potentially toxic to human life and the environment. Metal toxicity depends on chemical associations in soil. Understanding the chemical association of trace elements in soils amended with biosolids is very important since it determines their availability within rhizosphere and mobility beyond the rhizosphere. A sequential extraction method was used to determine the various chemical associations [labile (exchangeable + sorbed), organic, carbonates, and sulfides] of Cu, Zn, Cd, Cr, and Pb at the end of sorghum-sudan grass growth (65d) in Candler fine sand (pH = 6.8) and in Ogeechee loamy sand (pH = 5.2) amended with wastewater treatment sludge (WWTS) obtained from two different sources at application rates of 0, 24.7, 49.4, 98.8, and 148.2 Mg ha(-1). Results of this study indicated that irrespective of the soil type, Cu, Cd, Cr, and Pb in the labile fractions (exchangeable + sorbed) were in the range of 0-3.0 mg kg(-1) and the amount for Zn was in the range of 0.2-6.6 mg kg(-1). Therefore, their availability to plants and mobility beyond rhizosphere would be substantially low unless further transformations occur from other fractions. Results also indicated that the presence of substantial amounts of trace elements studied were in sulfide (HNO3) fraction and in organic (NaOH) fraction irrespective of soil type with the exception of Pb which was mainly present as carbonate (Na2EDTA) fraction and the remaining Pb equally as sulfide (HNO3) and organic (NaOH) fractions. Furthermore, results indicated that Cd was mainly present as carbonate (Na2EDTA) fraction. Irrespective of soil type, source and rate of WWTS application, summation of quantities of various fractions of all the trace elements studied through sequential extraction procedure were 1 to 25 % lower than that of total recoverable quantities of these trace elements determined on acid digestion described by US EPA method 3050 B. It was further evident that growing sorghum sudan grass for 65-d

  4. Wet and dry deposition of particles associated metals (Cd, Pb, Zn, Ni, Hg) in a rural wetland site, Marais Vernier, France

    NASA Astrophysics Data System (ADS)

    Connan, O.; Maro, D.; Hébert, D.; Roupsard, P.; Goujon, R.; Letellier, B.; Le Cavelier, S.

    2013-03-01

    Atmospheric transport plays an important role in the transfer of pollutants to ecosystems. During such transport, the atmospheric aerosol is one of the key factors in terms of deposition. Over 18 months, we studied the concentrations of Zn, Pb, Ni, Cd, Hg in air and precipitations in a wetland site in the north west of France. The objective of this study was to characterise the quantities transferred by dry and wet deposition. An eddy correlation technique was used to measure dry deposition velocities and determine the dry deposition fluxes from atmospheric concentration. In this site, wet deposition is almost always preponderant, except for Pb and Cd over several months. Measurements in the air and in rainwater are low and show that the site is protected from important anthropogenic influences, with levels that can be considered as background levels. In terms of deposition fluxes, the configuration of the site and the meteorological conditions (low wind speeds, low thermal fluxes) lead to low dry depositions. Wet depositions, although more important are also relatively low compared to the literature, directly linked to the pluviometry during the study period.

  5. Design of Three-shell Icosahedral Matryoshka Clusters A@B12@A20 (A = Sn, Pb; B = Mg, Zn, Cd, Mn)

    PubMed Central

    Huang, Xiaoming; Zhao, Jijun; Su, Yan; Chen, Zhongfang; King, R. Bruce

    2014-01-01

    We propose a series of icosahedral matryoshka clusters of A@B12@A20 (A = Sn, Pb; B = Mg, Zn, Cd), which possess large HOMO-LUMO gaps (1.29 to 1.54 eV) and low formation energies (0.06 to 0.21 eV/atom). A global minimum search using a genetic algorithm and density functional theory calculations confirms that such onion-like three-shell structures are the ground states for these A21B12 binary clusters. All of these icosahedral matryoshka clusters, including two previously found ones, i.e., [As@Ni12@As20]3− and [Sn@Cu12@Sn20]12−, follow the 108-electron rule, which originates from the high Ih symmetry and consequently the splitting of superatom orbitals of high angular momentum. More interestingly, two magnetic matryoshka clusters, i.e., Sn@Mn12@Sn20 and Pb@Mn12@Pb20, are designed, which combine a large magnetic moment of 28 µB, a moderate HOMO-LUMO gap, and weak inter-cluster interaction energy, making them ideal building blocks in novel magnetic materials and devices. PMID:25376938

  6. Design of Three-shell Icosahedral Matryoshka Clusters A@B12@A20 (A = Sn, Pb; B = Mg, Zn, Cd, Mn)

    NASA Astrophysics Data System (ADS)

    Huang, Xiaoming; Zhao, Jijun; Su, Yan; Chen, Zhongfang; King, R. Bruce

    2014-11-01

    We propose a series of icosahedral matryoshka clusters of A@B12@A20 (A = Sn, Pb; B = Mg, Zn, Cd), which possess large HOMO-LUMO gaps (1.29 to 1.54 eV) and low formation energies (0.06 to 0.21 eV/atom). A global minimum search using a genetic algorithm and density functional theory calculations confirms that such onion-like three-shell structures are the ground states for these A21B12 binary clusters. All of these icosahedral matryoshka clusters, including two previously found ones, i.e., [As@Ni12@As20]3- and [Sn@Cu12@Sn20]12-, follow the 108-electron rule, which originates from the high Ih symmetry and consequently the splitting of superatom orbitals of high angular momentum. More interestingly, two magnetic matryoshka clusters, i.e., Sn@Mn12@Sn20 and Pb@Mn12@Pb20, are designed, which combine a large magnetic moment of 28 µB, a moderate HOMO-LUMO gap, and weak inter-cluster interaction energy, making them ideal building blocks in novel magnetic materials and devices.

  7. Succulent species differ substantially in their tolerance and phytoextraction potential when grown in the presence of Cd, Cr, Cu, Mn, Ni, Pb, and Zn.

    PubMed

    Zhang, Chengjun; Sale, Peter W G; Clark, Gary J; Liu, Wuxing; Doronila, Augustine I; Kolev, Spas D; Tang, Caixian

    2015-12-01

    Plants for the phytoextraction of heavy metals should have the ability to accumulate high concentrations of such metals and exhibit multiple tolerance traits to cope with adverse conditions such as coexistence of multiple heavy metals, high salinity, and drought which are the characteristics of many contaminated soils. This study compared 14 succulent species for their phytoextraction potential of Cd, Cr, Cu, Mn, Ni, Pb, and Zn. There were species variations in metal tolerance and accumulation. Among the 14 succulent species, an Australian native halophyte Carpobrotus rossii exhibited the highest relative growth rate (20.6-26.6 mg plant(-1) day(-1)) and highest tolerance index (78-93%), whilst Sedum "Autumn Joy" had the lowest relative growth rate (8.3-13.6 mg plant(-1) day(-1)), and Crassula multicava showed the lowest tolerance indices (<50%). Carpobrotus rossii and Crassula helmsii showed higher potential for phytoextraction of these heavy metals than other species. These findings suggest that Carpobrotus rossii is a promising candidate for phytoextraction of multiple heavy metals, and the aquatic or semiterrestrial Crassula helmsii is suitable for phytoextraction of Cd and Zn from polluted waters or wetlands. PMID:26201657

  8. Mixture toxicity and tissue interactions of Cd, Cu, Pb and Zn in earthworms (Oligochaeta) in laboratory and field soils: a critical evaluation of data.

    PubMed

    Weltje, L

    1998-05-01

    Soil organisms inhabiting contaminated field sites are usually exposed to mixtures of toxicants. In such mixtures, toxicants can interact to express enhanced or weakened toxicity. Therefore, mixture effects should be considered in risk assessment methods for polluted soils. Data on mixture toxicity to soil organisms are scarce, however. In this paper, data on sublethal toxicity and tissue concentrations of Cd. Cu, Pb and Zn mixtures in earthworms are evaluated and compared with data on other organisms. Toxic effects were mainly antagonistic for total soil concentrations and nearly concentration-additive for 0.01 M CaCl2-extractable soil concentrations. Evidence to support concentration-additive behaviour of metals was found in interaction patterns within earthworm tissues. A method is proposed to assess the sublethal toxicity of metal mixtures in field soils to earthworms, based on single metal experiments from the laboratory. Finally, suggestions are made on how to incorporate mixture toxicity in risk assessment for polluted soils. PMID:9570111

  9. Removal of divalent heavy metals (Cd, Cu, Pb, and Zn) and arsenic(III) from aqueous solutions using scoria: kinetics and equilibria of sorption.

    PubMed

    Kwon, Jang-Soon; Yun, Seong-Taek; Lee, Jong-Hwa; Kim, Soon-Oh; Jo, Ho Young

    2010-02-15

    Kinetic and equilibrium sorption experiments were conducted on removal of divalent heavy metals (Pb(II), Cu(II), Zn(II), Cd(II)) and trivalent arsenic (As(III)) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The removal efficiencies of Pb, Cu, Zn, Cd, and As by the scoria (size=0.1-0.2mm, dose=60gL(-1)) were 94, 70, 63, 59, and 14%, respectively, after a reaction time of 24h under a sorbate concentration of 1mM and the solution pH of 5.0. A careful examination on ionic concentrations in sorption batches suggested that sorption behaviors of heavy metals onto scoria are mainly controlled by cation exchange. On the other hand, arsenic appeared to be sensitive to specific sorption onto hematite (a minor constituent of scoria). Equilibrium sorption tests indicated that the removal efficiency for heavy metals increases with increasing pH of aqueous solutions, which is resulted from precipitation as hydroxides. Similarly, multi-component systems containing heavy metals and arsenic showed that the arsenic removal increases with increasing pH of aqueous solutions, which can be attributed to coprecipitation with metal hydroxides. The empirically determined sorption kinetics were well fitted to a pseudo-second order model, while equilibrium sorption data for heavy metals and arsenic onto scoria were consistent with the Langmuir and Freundlich isotherms, respectively. Natural scoria studied in this work is an efficient sorbent for concurrent removal of divalent heavy metals and arsenic. PMID:19828237

  10. Influence of an upwelling filament on the distribution of labile fraction of dissolved Zn, Cd and Pb off Cape São Vicente, SW Iberia

    NASA Astrophysics Data System (ADS)

    Monteiro, Carlos Eduardo; Cardeira, Sara; Cravo, Alexandra; Bebianno, Maria João; Sánchez, Ricardo F.; Relvas, Paulo

    2015-02-01

    Under northerly winds upwelling is recurrent at the Cape São Vicente, SW Iberia, and plays a major role on the distribution of dissolved nutrients and metals. The aim of this work was to characterize the dissolved metals distribution of zinc (Zn), cadmium (Cd) and lead (Pb), associated with a filament of upwelled water that stretches seaward from the Cape. Additionally, the relationships between labile metals and other oceanographic parameters, such as current velocity and wind field patterns, temperature and salinity, nutrients, chlorophyll a and suspended solids were evaluated. The mass transport of the dissolved metals exported offshore was estimated, after a period of relatively strong and persistent upwelling. At the end of October 2004 a total of 42 CTD Rosette casts up to 400 dbar were sampled, distributed on an almost regular grid, together with along-track Acoustic Doppler Current Profile (ADCP) velocities. Seawater samples from two transects across the filament were analysed: one closest to the shore, where upwelling was intense and phytoplankton noticeably grew; and another further offshore where the filament was still well defined, but narrower and less marked despite with the maximum velocity currents. Labile dissolved metals were determined using anodic stripping voltammetry (ASV). The range of the metals recorded at the transect closest to the coast recorded was 0.26-3.8 nM (mean: 0.8 nM) for Zn, 2-11 pM (mean: 3 pM) for Cd and 8-60 pM (mean: 13 pM) while for the offshore transect was: 0.26-5.1 nM (mean: 1.2 nM) for Zn, 2-26 pM (mean 4 pM) for Cd and 8-74 pM (mean: 15 pM). Zinc recorded the highest concentrations, similar at both transects, and like Cd the lowest concentrations were found at near-surface depths. In opposition, the highest Pb concentrations were found at the near-surface depths at the northern stations in both transects. The filament exported more material in the offshore transect than in the transect closest to the coast

  11. Determination of Cd, Cr, Cu, Pb and Zn in human semen by graphite furnace atomic absorption spectrometry after microwave sample dissolution.

    PubMed

    Alvarado, J; Moreno, R; Cristiano, A R

    1991-09-01

    Human semen samples were analyzed by graphite furnace atomic absorption spectrometry, using L'vov platforms and the method of standard additions, to determine their Cd, Cr, Cu, Pb and Zn content. The samples were analyzed directly and after conventional and microwave wet acid dissolution. Matrix modification, using magnesium and palladium nitrates and ammonium biphosphate solutions, was evaluated for the analysis of the microwave-digested samples. The best results were obtained for Cr, Cu and Zn using Pd(NO3)2, and a mixture of Mg(NO3)2 and Pd(NO3)2 solutions. The direct analysis of water-diluted semen produced inaccurate results with unacceptably high standard deviations. The results obtained for the microwave-dissolved samples showed relative standard deviation values within the range 0.63-8.4%. The analysis of spiked semen solutions showed recoveries of the added analytes ranging from 96 to 104%. The accuracy of the measurements was checked against the NIST 1,577a, bovine liver, standard reference material. Sample dissolution time was drastically reduced from 3-4 hours, using the conventional method, to approximately 8 minutes using the microwave-assisted wet acid digestion procedure. PMID:1821719

  12. Environmental behaviors and potential ecological risks of heavy metals (Cd, Cr, Cu, Pb, and Zn) in multimedia in an oilfield in China.

    PubMed

    Hu, Yan; Wang, Dazhou; Li, Yu

    2016-07-01

    The environmental behaviors of five heavy metals (Cd, Cr, Cu, Pb, and Zn) in a Chinese oilfield were investigated using a steady-state multimedia aquivalence (SMA) model. The modeling results showed good agreement with the actual measured values, with average residual errors of 0.69, 0.83, 0.35, 0.16, and 0.54 logarithmic units for air, water, soil, sediment, and vegetation compartments, respectively. Model results indicated that most heavy metals were buried in sediment, and that transfers between adjacent compartments were mainly deposition from the water to the sediment compartment (48.59 %) and from the air to the soil compartment (47.74 %) via atmospheric dry/wet deposition. Sediment and soil were the dominant sinks, accounting for 68.80 and 25.26 % of all the heavy metals in the multimedia system, respectively. The potential ecological risks from the five heavy metals in the sediment and soil compartments were assessed by the potential ecological risk index (PERI). The assessment results demonstrate that the heavy metals presented low levels of ecological risk in the sediment compartment, and that Cd was the most significant contributor to the integrated potential ecological risk in the oilfield. The SMA model provided useful simulations of the transport and fate of heavy metals and is a useful tool for ecological risk assessment and contaminated site management. PMID:27040543

  13. Geochemical position of Pb, Zn and Cd in soils near the Olkusz mine/smelter, South Poland: effects of land use, type of contamination and distance from pollution source.

    PubMed

    Chrastný, Vladislav; Vaněk, Aleš; Teper, Leslaw; Cabala, Jerzy; Procházka, Jan; Pechar, Libor; Drahota, Petr; Penížek, Vít; Komárek, Michael; Novák, Martin

    2012-04-01

    The soils adjacent to an area of historical mining, ore processing and smelting activities reflects the historical background and a mixing of recent contamination sources. The main anthropogenic sources of metals can be connected with historical and recent mine wastes, direct atmospheric deposition from mining and smelting processes and dust particles originating from open tailings ponds. Contaminated agriculture and forest soil samples with mining and smelting related pollutants were collected at different distances from the source of emission in the Pb-Zn-Ag mining area near Olkusz, Upper Silesia to (a) compare the chemical speciation of metals in agriculture and forest soils situated at the same distance from the point source of pollution (paired sampling design), (b) to evaluate the relationship between the distance from the polluter and the retention of the metals in the soil, (c) to describe mineralogy transformation of anthropogenic soil particles in the soils, and (d) to assess the effect of deposited fly ash vs. dumped mining/smelting waste on the mobility and bioavailability of metals in the soil. Forest soils are much more affected with smelting processes than agriculture soils. However, agriculture soils suffer from the downward metal migration more than the forest soils. The maximum concentrations of Pb, Zn, and Cd were detected in a forest soil profile near the smelter and reached about 25 g kg(- 1), 20 g kg(- 1) and 200 mg kg(- 1) for Pb, Zn and Cd, respectively. The metal pollutants from smelting processes are less stable under slightly alkaline soil pH then acidic due to the metal carbonates precipitation. Metal mobility ranges in the studied forest soils are as follows: Pb > ZnCd for relatively circum-neutral soil pH (near the smelter), Cd > Zn > Pb for acidic soils (further from the smelter). Under relatively comparable pH conditions, the main soil properties influencing metal migration are total organic carbon and cation exchange

  14. The Uptake Mechanism of Cd(II), Cr(VI), Cu(II), Pb(II), and Zn(II) by Mycelia and Fruiting Bodies of Galerina vittiformis

    PubMed Central

    Damodaran, Dilna; Balakrishnan, Raj Mohan; Shetty, Vidya K.

    2013-01-01

    Optimum concentrations of heavy metals like copper, cadmium, lead, chromium, and zinc in soil are essential in carrying out various cellular activities in minimum concentrations and hence help in sustaining all life forms, although higher concentration of these metals is lethal to most of the life forms. Galerina vittiformis, a macrofungus, was found to accumulate these heavy metals into its fleshy fruiting body in the order Pb(II) > Cd(II) > Cu(II) > Zn(II) > Cr(VI) from 50 mg/kg soil. It possesses various ranges of potential cellular mechanisms that may be involved in detoxification of heavy metals and thus increases its tolerance to heavy metal stress, mainly by producing organic acids and phytochelatins (PCs). These components help in repairing stress damaged proteins and compartmentalisation of metals to vacuoles. The stress tolerance mechanism can be deduced by various analytical tools like SEM-EDX, FTIR, and LC-MS. Production of two kinds of phytochelatins was observed in the organism in response to metal stress. PMID:24455671

  15. Different membrane modifications revealed by atomic force/lateral force microscopy after doping of human pancreatic cells with Cd, Zn, or Pb.

    PubMed

    Girasole, Marco; Cricenti, Antonio; Generosi, Renato; Longo, Giovanni; Pompeo, Giuliano; Cotesta, Simona; Congiu-Castellano, Agostina

    2007-10-01

    The interaction of the cytotoxic metals cadmium, zinc, and lead with pancreatic cells was studied by atomic force/lateral Force microscopy (AFM/LFM), an approach that provides both topographic (with nanometer scale lateral resolution) and chemical information on the membrane. Different morphological modifications of the overall cell shape and roughness took place as consequence of 100 muM metal-dependent treatment. Furthermore, after exposure to Cd(Cl(2)) and Zn(Cl(2)), but not Pb(Cl(2)), the LFM images revealed several areas of the cell's surface showing lateral friction contrasts that have been interpreted as marker of different alterations of the cell physiology induced by the metal loading. Thus, the coupling of LFM detection to topographic AFM characterization allows to distinguish, through a nondestructive and surface characterising approach, between different metal-induced cytotoxic effects on cells. In this framework, the role of the LFM as an important tool to discriminate between different alteration of a biological system has to be highlighted. PMID:17726693

  16. Synthesis and characterization of an azo dibenzoic acid Schiff base and its Ni(II), Pb(II), Zn(II) and Cd(II) complexes

    NASA Astrophysics Data System (ADS)

    Kakanejadifard, Ali; Esna-ashari, Fatemeh; Hashemi, Payman; Zabardasti, Abedin

    2013-04-01

    The new Schiff base 4,4'-(1E,1'E)-(3,3'-(1E,1'E)-(pyridine-2,6-diylbis(azan-1-yl-1-ylid ene))bis(methan-1-yl-1-ylidene)bis(4-hydroxy-3,1-phenylene))bis(diazene-2,1-diyl)dibenzoic acid (1) was prepared from the condensation reaction of 2,6-diaminopyridine with 4-((3-formyl-4-hydroxyphenyl)diazenyl)benzoic acid in methanol. The compound 1 is potentially an N, O multidentate chelating ligand which could form stable complexes with metal ions in 1:1 up to 1:3 mol ratio of metal to ligand. The 1:1 complexes of Schiff base 1 with Ni(II), Pb(II), Zn(II) and Cd(II) have been synthesized by its condensation reaction with appropriate salts of metal ions. Structures of Schiff base (1) as well as its complexes with abovementioned metal ions were characterized by elemental analysis, mass, IR, UV-vis., 1H and 13С NMR spectroscopy.

  17. Modelling removal mechanisms of Pb, Cu, Zn and Cd in acidic groundwater during the neutralization by ambient surface and ground waters

    USGS Publications Warehouse

    Paulson, Anthony J.; Balistrieri, Laurie S.

    1999-01-01

    Removal of Pb, Cu, Zn, and Cd during neutralization of acid rock drainage is examined using model simulations of field conditions and laboratory experiments involving mixing of natural drainage and surface waters or groundwaters. The simulations consider sorption onto hydrous Fe and Al oxides and particulate organic carbon, mineral precipitation, and organic and inorganic solution complexation of metals for two physical systems where newly formed oxides and particulate organic matter are either transported or retained along the chemical pathway. The calculations indicate that metal removal is a strong function of the physical system. Relative to direct discharge of ARD into streams, lower metal removals are observed where ARD enters streamwaters during the latter stages of neutralization by ambient groundwater after most of the Fe has precipitated and been retained in the soils. The mixing experiments, which represent the field simulations, also demonstrated the importance of dissolved metal to particle Fe ratios in controlling dissolved metal removal along the chemical pathway. Finally, model calculations indicate that hydrous Fe oxides and particulate organic carbon are more important than hydrous Al oxides in removing metals and that both inorganic and organic complexation must be considered when modeling metal removal from aquatic systems that are impacted by sulfide oxidation.

  18. Ultrafine particle and fine trace metal (As, Cd, Cu, Pb and Zn) pollution episodes induced by industrial emissions in Huelva, SW Spain

    NASA Astrophysics Data System (ADS)

    Fernández-Camacho, R.; Rodríguez, S.; de la Rosa, J.; Sánchez de la Campa, A. M.; Alastuey, A.; Querol, X.; González-Castanedo, Y.; Garcia-Orellana, I.; Nava, S.

    2012-12-01

    Urban air quality impairment by ultrafine particles has become a matter of concern due to the adverse effects on human health. Most of the studies of ultrafine particles in urban air quality have focused on vehicle exhaust emissions. We studied how industrial emissions contribute to ultrafine particle concentrations in downwind urban ambient air. This research is based on experimental data collected in the ambient air of the industrial city of Huelva (SW Spain) over April 2008-December 2009 period (particle number, gaseous pollutants and black carbon concentrations and levels and chemical composition of PM10 and PM2.5 with daily and hourly resolution). This city is affected by emissions from the second largest Cu-smelter in Europe, phosphoric acid and fertilizer production plants and an oil refinery and petrochemical plant. Industrial emissions are the main cause of ultrafine particle episodes. When vehicle exhaust emissions are the main source, ultrafine particles typically show (24-h mean) concentrations within the range 14,700-5000 cm-3 (50th-1st), with 60% of these linked to this source and 30% to industrial emissions. In contrast, when daily mean levels of N are within the range 50,000-25,500 cm-3 (100th-70th), industrial and vehicle exhaust emissions accounted for 49 and 30%, respectively. High concentrations of toxic trace metals (As, Cu, Cd, Zn and Pb) were recorded when the study city suffered fumigations of the Cu-smelter plumes (e.g. 10-25 ng m-3 As, 1-2 ng m-3 Cd and >105 cm-3 of ultrafine particles). Because of these industrial emissions, ultrafine particle concentrations during daylight are about two times higher than those observed in other European cities. Recently, ultrafine particle emissions in vehicle exhausts have been subject to limit values in a recent stage of the EURO standards. Industrial emissions should also be considered.

  19. 210Po Activity and concentrations of selected trace elements (As, Cd, Cu, Hg, Pb, Zn) in the muscle tissue of tunas Thunnus albacares and Katsuwonus pelamis from the Eastern Pacific Ocean.

    PubMed

    Ruelas-Inzunza, Jorge; Soto-Jiménez, Martín Federico; Ruiz-Fernández, Ana Carolina; Bojórquez-Leyva, Humberto; Pérez-Bernal, Hascibe; Páez-Osuna, Federico

    2012-12-01

    Daily mineral intake (DMI) of Cu and Zn, percentage weekly intake (PWI) of As, Cd, Hg, Pb, and doses of (210)Po were estimated by using their elemental concentration in muscle of two tuna species and the average tuna consumption in Mexico. Skipjack tuna Katsuwonus pelamis had significantly (p < 0.05) higher levels of As (1.38 μg g(-1) dw) and Cu (1.85 μg g(-1) dw) than yellowfin tuna Thunnus albacares, whereas Pb concentrations (0.18 μg g(-1) dw) were significantly (p < 0.05) higher in T. albacares. The sequence of elemental concentrations in both species was Zn > Cu > As > Hg > Pb > Cd. In T. albacares, concentrations of Cd and Pb in muscle tissue were positively correlated (p < 0.05) with weight of specimens, while Cu was negatively correlated. DMI values were below 10 %. PWI figures (<2 %) are not potentially harmful to human health. (210)Po concentration in T. albacares and K. pelamis accounts for 13.5 to 89.7 % of the median individual annual dose (7.1 μSv) from consumption of marine fish and shellfish for the world population. PMID:22684512

  20. Metallophytes in biotopes polluted by waste dumps rich in Zn-Pb, Cd (Olkusz region) - review of previous and planned research

    NASA Astrophysics Data System (ADS)

    Rożek, Dorota

    2013-09-01

    The aim of that publication was the presentation of previous and planned research concerning selected vascular plants and soils near Olkusz (Southern Poland). The extremely high concentration of heavy metals in soils from that region was caused by the natural geochemical aureoles of dispersed metals (due to weathering of Zn-Pb-Fe ore sulphides) and mining and processing of shallowly occurring metalliferous deposits (containing Ag-Pb and Zn-Pb ores) since XII century. The condition of stress in metals, shortage of water and some plant nutrition led to formation of some adaptable vegetation features by plants growing in that region. Some species called metallophytes have been already detailed investigated. Moreover some geochemical and pedological research of soil have been already done. However the conditions of habitat of pioneering species such as Koeleria glauca and Corynephorus canescens are not still recognized.

  1. Trends in the spatial and temporal distribution of metals (Cd, Cu, Zn and Pb) and organic compounds (PCBs and PAHs) in Dutch coastal zone sediments from 1981 to 1996: a model case study for Cd and PCBs

    NASA Astrophysics Data System (ADS)

    Laane, R. W. P. M.; Sonneveldt, H. L. A.; Van der Weyden, A. J.; Loch, J. P. G.; Groeneveld, G.

    1999-03-01

    The spatial and temporal distribution of trace metals (Cd, Pb, Zn and Cu), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) was studied to assess trends in the sediment of the Dutch coastal zone (<63-μm fraction) from 1981 to 1996. In general, the distributions showed a distinct zonation, with highest concentrations close to the coast near freshwater outlets and where dredged material had been dumped. Over time, the zone with high concentrations narrowed and moved towards the coast. The median of the percentage of the <63-μm fraction in the surface sediments did not change significantly in the Dutch coastal zone between 1981 and 1996. In that period, the median concentrations of Cd, Cu, Zn and Pb fell by 71, 38, 49 and 53%, respectively, in the area close to the coast (<20 km) north of the outlet of the Rhine. South of this outlet the median Cd, Cu and Zn concentrations fell by 45, 29 and 17%, respectively, and in the open sea area (>20 km offshore) the median concentrations for Cu and Zn fell by 35 and 18%, respectively. The largest reduction (80%) of the median concentration of PCBs occurred in the surface sediment in the open sea area (>20 km offshore) between 1986 and 1996. During this period the median PCBs concentration fell by nearly 70% close to the coast. The median PAH concentration fell by only 26% north of the outlet of the Rhine (<20 km from the coast) between 1986 and 1996. In the other areas there was no significant change. Possible reasons are that the main sources of PAHs are in the North Sea itself and that the load of PAHs from dredged material dumped in the Dutch coastal zone increased during the period studied. The reduction of the concentrations of metals and organic micropollutants in the surface sediments of the Dutch coastal zone is explained by a conservative physical mixing model, in which the previously polluted silt fraction in the surface sediments is replaced by less polluted suspended matter. There is a

  2. Long-term environmental exposure to metals (Cu, Cd, Pb, Zn) activates the immune cell stress response in the common European sea star (Asterias rubens).

    PubMed

    Matranga, V; Pinsino, A; Randazzo, D; Giallongo, A; Dubois, P

    2012-05-01

    The common sea star Asterias rubens represents a key-species of the North-Eastern Atlantic macro benthic community. The cells of their immune system, known as coelomocytes, are the first line of defence against environmental hazards. Here, we report the results of investigations on the immune cells response of sea stars exposed to marine environmental pollution for long periods. We show that levels of the heat shock cognate protein 70 (HSC70) in coelomocytes from A. rubens, which were collected during a field study in the Sǿrfjord (North Sea, SW coast of Norway) along a contamination gradient, are directly associated with the long-term accumulation of Cd, Cu heavy metals exclusively in the tegument. Conversely, Pb and Zn accumulation in the tegument did not relate to HSC70 levels and none of the metals were found accumulated in the pyloric coeca. In addition the coelomocytes from A. rubens, collected in high and low metal impacted stations were examined by a proteomic approach using two-dimensional electrophoresis (2DE). By comparison of the proteomic maps, we observed that 31 protein spots differed in their relative abundance, indicating a gene expression response to the metal mixture exposure. All together, our results confirm that the echinoderm immune cells are a suitable model for the assessment of long-term exposure to environmental pollution, moreover that the increased level of HSC70 can be considered a signal of an acquired tolerance within a large spectrum of protein profile changes occurring in response to metal contamination. PMID:22000270

  3. Distribution of P, K, Ca, Mg, Cd, Cu, Fe, Mn, Pb and Zn in wood and bark age classes of willows and poplars used for phytoextraction on soils contaminated by risk elements.

    PubMed

    Zárubová, Pavla; Hejcman, Michal; Vondráčková, Stanislava; Mrnka, Libor; Száková, Jiřina; Tlustoš, Pavel

    2015-12-01

    Fast-growing clones of Salix and Populus have been studied for remediation of soils contaminated by risk elements (RE) using short-rotation coppice plantations. Our aim was to assess biomass yield and distributions of elements in wood and bark of highly productive willow (S1--[Salix schwerinii × Salix viminalis] × S. viminalis, S2--Salix × smithiana clone S-218) and poplar (P1--Populus maximowiczii × Populus nigra, P2--P. nigra) clones with respect to aging. The field experiment was established in April 2008 on moderately Cd-, Pb- and Zn- contaminated soil. Shoots were harvested after four seasons (February 2012) and separated into annual classes of wood and bark. All tested clones grew on contaminated soils, with highest biomass production and lowest mortality exhibited by P1 and S2. Concentrations of elements, with exception of Ca and Pb, decreased with age and were higher in bark than in wood. The Salix clones were characterised by higher removal of Cd, Mn and Zn compared to the Populus clones. Despite generally higher RE content in young shoots, partly due to lower wood/bark ratios and higher RE concentrations in bark, the overall removal of RE was higher in older wood classes due to higher biomass yield. Thus, longer rotations seem to be more effective when phytoextraction strategy is considered. Of the four selected clones, S1 exhibited the best removal of Cd and Zn and is a good candidate for phytoextraction. PMID:26201656

  4. Bioaccumulation of Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in trophosome and vestimentum of the tube worm Riftia pachyptila from Guaymas basin, Gulf of California

    NASA Astrophysics Data System (ADS)

    Ruelas-Inzunza, J.; Páez-Osuna, F.; Soto, Luis A.

    2005-07-01

    Twenty two specimens of vestimentiferan tube worms Riftia pachyptila were collected from Guaymas Basin. The distribution of ten trace metals in trophosome and vestimentum was investigated. Highest mean concentrations of Co, Cu and Fe were detected in the trophosome; while higher mean levels of Cd, Hg, Mn, Ni, Pb and Zn were measured in the vestimentum. However, the t-student test resulted in significant differences (p<0.05) only in the case of Co. Cd and Fe concentrations in vestimentum increased accordingly with the size of specimens. With respect to vent fluids, extreme uptake seems to be a characteristic of R. pachyptila in the case of Cu and Zn but not for the rest of the analyzed metals. Studies concerning accumulation mechanisms of trace metals in R. pachyptila are needed, particularly on the capacity of this organism to tolerate elevated levels of elements considered as non-essential.

  5. Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d'Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models

    USGS Publications Warehouse

    Balistrieri, L.S.; Blank, R.G.

    2008-01-01

    In order to evaluate thermodynamic speciation calculations inherent in biotic ligand models, the speciation of dissolved Cd, Cu, Pb, and Zn in aquatic systems influenced by historical mining activities is examined using equilibrium computer models and the diffusive gradients in thin films (DGT) technique. Several metal/organic-matter complexation models, including WHAM VI, NICA-Donnan, and Stockholm Humic model (SHM), are used in combination with inorganic speciation models to calculate the thermodynamic speciation of dissolved metals and concentrations of metal associated with biotic ligands (e.g., fish gills). Maximum dynamic metal concentrations, determined from total dissolved metal concentrations and thermodynamic speciation calculations, are compared with labile metal concentrations measured by DGT to assess which metal/organic-matter complexation model best describes metal speciation and, thereby, biotic ligand speciation, in the studied systems. Results indicate that the choice of model that defines metal/organic-matter interactions does not affect calculated concentrations of Cd and Zn associated with biotic ligands for geochemical conditions in the study area, whereas concentrations of Cu and Pb associated with biotic ligands depend on whether the speciation calculations use WHAM VI, NICA-Donnan, or SHM. Agreement between labile metal concentrations and dynamic metal concentrations occurs when WHAM VI is used to calculate Cu speciation and SHM is used to calculate Pb speciation. Additional work in systems that contain wide ranges in concentrations of multiple metals should incorporate analytical speciation methods, such as DGT, to constrain the speciation component of biotic ligand models. ?? 2008 Elsevier Ltd.

  6. Modulation of Zn/Cd P(1B2)-ATPase activities in Arabidopsis impacts differently on Zn and Cd contents in shoots and seeds.

    PubMed

    Cun, Pierre; Sarrobert, Catherine; Richaud, Pierre; Chevalier, Anne; Soreau, Paul; Auroy, Pascaline; Gravot, Antoine; Baltz, Anthony; Leonhardt, Nathalie; Vavasseur, Alain

    2014-11-01

    Zn is an essential microelement for all living cells and Zn deficiency is widespread in world's population. At the same time, high Zn concentration and low Cd concentration are toxic to the environment. Both Zn and Cd are transported in planta via Zn/Cd HMA transporters. Engineering of HMAs expression in plants may provide a way for Zn biofortification of food as well as phytoremediation of polluted soils. In the present study we have assessed the impact of Zn/Cd HMAs invalidation/overexpression in Arabidopsis thaliana on Zn and Cd translocation from the roots to the shoots and in Zn grain filling. Overexpression of AtHMA4 had a large impact on Zn and Cd translocation and resulted in a 3-fold higher potential of Cd and Zn extraction from an industrial soil highly contaminated by Zn, Pb and Cd. Despite AtHMA4 overexpressing lines presenting a higher Zn concentration in the shoot, the Zn content in the seeds was found to be lower than in wild type plants. Our results indicate that AtHMA4 overexpression is an efficient tool to increase the root to shoot translocation of Zn and Cd in plants. Concerning biofortification of seeds, this study underlines the need for specific promoters to drive an expression pattern of the transporters in favour of Zn grain filling. PMID:25272315

  7. Health hazard prospecting by modeling wind transfer of metal-bearing dust from mining waste dumps: application to Jebel Ressas Pb-Zn-Cd abandoned mining site (Tunisia).

    PubMed

    Ghorbel, Manel; Munoz, Marguerite; Solmon, Fabien

    2014-10-01

    This work presents a modeling approach to simulate spatial distribution of metal contamination in aerosols with evaluation of health hazard. This approach offers the advantage to be non-intrusive, less expensive than sampling and laboratory analyses. It was applied to assess the impact of metal-bearing dust from mining wastes on air quality for a nearby community and agricultural lands in Jebel Ressas (Tunisia) locality. Dust emission rates were calculated using existing parameterization adapted to the contamination source composed of mining wastes. Metal concentrations were predicted using a Gaussian model (fugitive dust model) with, as input: emission rates, dump physical parameters and meteorological data measured in situ for 30 days in summertime. Metal concentration maps were built from calculated PM10 particle concentrations. They evidence the areas where Pb and Cd concentrations exceeded WHO guidelines (0.5 and 0.005 µg/m(3), respectively). Maximum concentrations of Pb and Cd in PM10 are, respectively, of 5.74 and 0.0768 µg/m(3) for measured wind speed values up to 22 m/s. Preferential areas of contamination were determined in agricultural lands to the NW from the source dump where Pb and Cd exceeded guidelines up to a distance of 1,200 m. The secondary spreading directions were SW and E, toward the village. Health hazard prospecting shown that a major part of the village was exposed to contaminated dust and that daily hazard quotient (HQ) values reached locally 118 and 158, respectively, for Pb and Cd during the study period. However, HQ variations in the village are high, both temporally and geographically. PMID:24760620

  8. Distribution and accumulation of Cd, Cu, Hg, Pb and Zn in the surface sediments of El Tobari Lagoon, central-East Gulf of California: An ecosystem associated with agriculture and aquaculture activities.

    PubMed

    Jara-Marini, M E; Tapia-Alcaraz, J N; Dumer-Gutiérrez, J A; García-Rico, L; García-Hernández, J; Páez-Osuna, F

    2013-01-01

    The purpose of this research is to provide a comprehensive assessment of the concentration levels and spatial variability of cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb) and zinc (Zn) in El Tobari Lagoon in surface sediments during two seasons for several geochemical variables that could explain the observed heavy metal variability. Seventy-two surface sediments samples were collected in 12 different sites of the El Tobari Lagoon. Sediment samples were dried and subjected to acid extraction using a microwave system and five metals (Cd, Cu, Hg, Pb and Zn) were measured using atomic adsorption spectrometry. A certificate sediment material and blanks were used as quality control purposes. The enrichment factor (EF) and the index of geoaccumulation (Igeo) were calculated as index of metals contamination for the sediments, using aluminum as the conservative element. The five metals examined in sediments from El Tobari Lagoon exhibited a linear correlation with Al as result of the large specific surface areas of these sediment components and the chemical affinities between them. The metals contents in sites of the El Tobari Lagoon were variable, and Cd, Cu and Hg presented a seasonal behavior. The enrichment factor and index of geoaccumulation analysis indicated that Cd and Hg exhibited a certain extent (EF for Cd ranged from 4.10 to 10.29; EF for Hg ranged from 2.77 to 12.89) of anthropogenic pollution, while Cu showed sporadic (EF ranged from 0.43 to 2.54) anthropogenic contamination. The highest concentrations of Cd, Cu and Hg were found in the sites that regularly received discharge effluents from agriculture and aquaculture. PMID:24007439

  9. A rapid, partial leach and organic separation for the sensitive determination of Ag, Bi, Cd, Cu, Mo, Pb, Sb, and Zn in surface geologic materials by flame atomic absorption

    USGS Publications Warehouse

    Viets, J.G.; Clark, J.R.; Campbell, W.L.

    1984-01-01

    A solution of dilute hydrochloric acid, ascorbic acid, and potassium iodide has been found to dissolve weakly bound metals in soils, stream sediments, and oxidized rocks. Silver, Bi, Cd, Cu, Mo, Pb, Sb, and Zn are selectively extracted from this solution by a mixture of Aliquat 336 (tricaprylyl methyl ammonium chloride) and MIBK (methyl isobutyl ketone). Because potentially interfering major and minor elements do not extract, the organic separation allows interference-free determinations of Ag and Cd to the 0.05 ppm level, Mo, Cu, and Zn to 0.5 ppm, and Bi, Pb, and Sb to 1 ppm in the sample using flame atomic absorption spectroscopy. The analytical absorbance values of the organic solution used in the proposed method are generally enhanced more than threefold as compared to aqueous solutions, due to more efficient atomization and burning characteristics. The leaching and extraction procedures are extremely rapid; as many as 100 samples may be analyzed per day, yielding 800 determinations, and the technique is adaptable to field use. The proposed method was compared to total digestion methods for geochemical reference samples as well as soils and stream sediments from mineralized and unmineralized areas. The partial leach showed better anomaly contrasts than did total digestions. Because the proposed method is very rapid and is sensitive to pathfinder elements for several types of ore deposits, it should be useful for reconnaissance surveys for concealed deposits. ?? 1984.

  10. Solution and laser ablation inductively coupled plasma-mass spectrometry measurements of Br, I, Pb, Mn, Cd, Zn, and B in the organic skeleton of soft corals and black corals

    NASA Astrophysics Data System (ADS)

    Williams, B.; Grottoli, A. G.

    2011-03-01

    Proxy records can be derived from soft corals and black corals using minor and trace element measurements of the organic skeleton of these corals. Here, concentrations of Br, I, Pb, Mn, Cd, Zn, and B in the organic skeleton were determined using solution inductively coupled plasma-mass spectrometry (ICP-MS) in one black coral from 5 m depth and two soft corals from 85 and 105 m depth collected from a reef offshore of Palau in the western tropical Pacific. Solution ICP-MS results indicate that concentrations of some elements vary as expected with depth (Cd and Mn) while others are taxa specific (I) or colony specific (Br, Pb, Zn, and B). The intensities of the same elements normalized to 13C were also measured at high resolution using laser ablation (LA) ICP-MS along radial transects covering the lifespan of the colonies. The results here indicate that high-resolution LA ICP-MS elemental records in black corals could be more fully developed for paleoceanographic reconstructions. In contrast, results of the laser transects from the two soft corals were not reproducible for any of the elements, and no discernible patterns were detected that could be developed into reliable proxy records using the current LA ICP-MS method.

  11. Measurements of labile Cd, Cu, Ni, Pb, and Zn levels at a northeastern Brazilian coastal area under the influence of oil production with diffusive gradients in thin films technique (DGT).

    PubMed

    de Souza, João M; Menegário, Amauri A; de Araújo Júnior, Marcus A G; Francioni, Eleine

    2014-12-01

    In this work, the ability of the diffusive gradients in thin films technique (DGT) was evaluated for monitoring the concentrations, and estimating the availability, of metals at a northeastern Brazilian coastal area under the influence of oil production. Three sites with an average distance between 0m (EM-1), 100 m (EM-2), and 1,000 m (EM-3) of a submarine outfall-I (Guamaré-RN, Brazil) and another site (GA-1) with an average distance of 12,000 m east of Outfall I, near the city of Galinhos, were studied. DGT units were deployed at the same sites in three campaigns from July, 2010 to June, 2011. Effects on the accuracy of analytical results regarding the deployment time, gel porosity, and thickness were evaluated. There was no difference between the measurements obtained with two sets of DGT devices, those assembled with open or restrictive pore gel, respectively, showing that organic metallic species are not present near the submarine outlet. After 21 day deployments in a region (near Submarine Outfall I) that receives produced waters that have been treated, there was evidence of biofilm formation on DGT membranes. However, it was demonstrated that the biofilm interference with DGT measurements was negligible. Data found in this work show that total concentrations of Cd, Cu, Pb, Ni, and Zn in seawater samples collected at sites GA-1 and EM-1 in two campaigns were below 0.33, 1.67, 0.47, 0.70, 2.86 ng mL(-1) respectively. For the first time, labile levels of Cd, Cu, Pb, Ni, and Zn in an area under the influence of oil production were determined. DGT measurements allowed the verification of the effects of temporal variation on levels of Zn and Ni. There were no effects of spatial variations on levels of Cd, Cu, Ni, Pb, and Zn at the four studied sites, suggesting no contamination of these metals at the northeastern Brazilian coastal area investigated in this work. PMID:25237789

  12. Distribution of selected essential (Co, Cu, Fe, Mn, Mo, Se, and Zn) and nonessential (Cd, Pb) trace elements among protein fractions from hepatic cytosol of European chub (Squalius cephalus L.).

    PubMed

    Krasnići, Nesrete; Dragun, Zrinka; Erk, Marijana; Raspor, Biserka

    2013-04-01

    Association of selected essential (Co, Cu, Fe, Mn, Mo, Se, and Zn) and nonessential (Cd, Pb) trace elements with cytosolic proteins of different molecular masses was described for the liver of European chub (Squalius cephalus) from weakly contaminated Sutla River in Croatia. The principal aim was to establish basic trace element distributions among protein fractions characteristic for the fish living in the conditions of low metal exposure in the water. The fractionation of chub hepatic cytosols was carried out by size exclusion high performance liquid chromatography (SE-HPLC; Superdex™ 200 10/300 GL column), and measurements were performed by high resolution inductively coupled plasma mass spectrometry (HR ICP-MS). Elution profiles of essential elements were mostly characterized by broad peaks covering wide range of molecular masses, as a sign of incorporation of essential elements in various proteins within hepatic cytosol. Exceptions were Cu and Fe, with elution profiles characterized by sharp, narrow peaks indicating their probable association with specific proteins, metallothionein (MT), and ferritin, respectively. The main feature of the elution profile of nonessential metal Cd was also single sharp, narrow peak, coinciding with MT elution time, and indicating almost complete Cd detoxification by MT under the conditions of weak metal exposure in the water (dissolved Cd concentration ≤0.3 μg L(-1)). Contrary, nonessential metal Pb was observed to bind to wide spectrum of proteins, mostly of medium molecular masses (30-100 kDa), after exposure to dissolved Pb concentration of ~1 μg L(-1). The obtained information within this study presents the starting point for identification and characterization of specific metal/metalloid-binding proteins in chub hepatic cytosol, which could be further used as markers of metal/metalloid exposure or effect on fish. PMID:22886752

  13. Availability of heavy metals (Cd, Pb, And Cr) in agriculture from commercial fertilizers.

    PubMed

    Nacke, H; Gonçalves, A C; Schwantes, D; Nava, I A; Strey, L; Coelho, G F

    2013-05-01

    The purpose of this study was to investigate the availability of the heavy metals cadmium (Cd), lead (Pb), and chromium (Cr) to soil and maize plants fertilized with different sources and doses of zinc (Zn) in a Rhodic Eutrudox soil. For that purpose, concentrations of Cd, Pb, and Cr were evaluated in leaf tissue and grains of maize plants and in 0-20 and 20-40 cm soil layers after fertilization with four doses of Zn from eight different sources of fertilizer. There was no accumulation of Cd, Pb, and Cr in maize grain and Cd and Cr in leaf tissue of the plants; nevertheless, there was accumulation of Pb in leaf tissue, showing its availability throughout different sources of Zn and consequent uptake by plants. Regarding the soil, it was observed that fertilizer from the different sources made Cd, Pb, and Cr available at increasing amounts proportional to increased Zn doses. Under experimental conditions, fertilization with Zn increased concentrations of heavy metals Cd, Pb and Cr in soil, further highlighting the importance of conducting more studies related to the application of mineral fertilizers for micronutrient supply and the availability of heavy metals. PMID:23361451

  14. A transferable force field for CdS-CdSe-PbS-PbSe solid systems

    SciTech Connect

    Fan, Zhaochuan; Vlugt, Thijs J. H.; Koster, Rik S.; Fang, Changming; Huis, Marijn A. van; Wang, Shuaiwei; Yalcin, Anil O.; Tichelaar, Frans D.; Zandbergen, Henny W.

    2014-12-28

    A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., “Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth,” Nano Lett. 14, 3661–3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

  15. Responses of different water spinach cultivars and their hybrid to Cd, Pb and Cd-Pb exposures.

    PubMed

    Xin, Junliang; Huang, Baifei; Yang, Zhongyi; Yuan, Jiangang; Dai, Hongwen; Qiu, Qiu

    2010-03-15

    A pot experiment was conducted to investigate the stability of Cd and/or Pb accumulation in shoot of Cd and Pb pollution-safe cultivars (PSCs), the hereditary pattern of shoot Cd accumulation, and the transfer potentials of Cd and Pb in water spinach (Ipomoea aquatica Forsk.). A typical Cd-PSC, a typical non-Cd-PSC (Cd accumulative cultivar), a hybrid from the former two cultivars, and two typical Cd+Pb-PSCs were grown in seven soils with different concentrations of Cd and Pb. The results showed that concentrations of Cd and Pb in shoot of the PSCs were always lower than the non-PSC and the highest Cd and Pb transfer factors were also always observed in the non-PSC, indicating the stability of the PSCs in Cd and Pb accumulation. Shoot Cd concentration seemed to be controlled by high Cd dominant gene(s) and thus crossbreeding might not minimize Cd accumulation in water spinach. Interaction between Cd and Pb in soils affected the accumulations of the metals in shoot of water spinach. Under middle Cd and Pb treatments, the presence of higher Pb promoted the accumulation of Cd. However, under high Pb treatment, accumulations of Cd and Pb were both restricted. PMID:19875230

  16. An ICP-MS procedure to determine Cd, Co, Cu, Ni, Pb and Zn in oceanic waters using in-line flow-injection with solid-phase extraction for preconcentration.

    PubMed

    O'Sullivan, Jeanette E; Watson, Roslyn J; Butler, Edward C V

    2013-10-15

    An automated procedure including both in-line preconcentration and multi-element determination by an inductively coupled plasma mass spectrometer (ICP-MS) has been developed for the determination of Cd, Co, Cu, Ni, Pb and Zn in open-ocean samples. The method relies on flow injection of the sample through a minicolumn of chelating (iminodiacetate) sorbent to preconcentrate the trace metals, while simultaneously eliminating the major cations and anions of seawater. The effectiveness of this step is tested and reliability in results are secured with a rigorous process of quality assurance comprising 36 calibration and reference samples in a run for analysis of 24 oceanic seawaters in a 6-h program. The in-line configuration and procedures presented minimise analyst operations and exposure to contamination. Seawater samples are used for calibration providing a true matrix match. The continuous automated pH measurement registers that chelation occurs within a selected narrow pH range and monitors the consistency of the entire analytical sequence. The eluent (0.8M HNO3) is sufficiently strong to elute the six metals in 39 s at a flow rate of 2.0 mL/min, while being compatible for prolonged use with the mass spectrometer. Throughput is one sample of 7 mL every 6 min. Detection limits were Co 3.2 pM, Ni 23 pM, Cu 46 pM, Zn 71 pM, Cd 2.7 pM and Pb 1.5 pM with coefficients of variation ranging from 3.4% to 8.6% (n=14) and linearity of calibration established beyond the observed concentration range of each trace metal in ocean waters. Recoveries were Co 96.7%, Ni 102%, Cu 102%, Zn 98.1%, Cd 92.2% and Pb 97.6%. The method has been used to analyse ~800 samples from three voyages in the Southern Ocean and Tasman Sea. It has the potential to be extended to other trace elements in ocean waters. PMID:24054694

  17. Influence of the application renewal of glutamate and tartrate on Cd, Cu, Pb and Zn distribution between contaminated soil and Paulownia tomentosa in a pilot-scale assisted phytoremediation study.

    PubMed

    Doumett, S; Fibbi, D; Azzarello, E; Mancuso, S; Mugnai, S; Petruzzelli, G; Del Bubba, M

    2011-01-01

    The influence of repeated applications of tartrate (TAR) and glutamate (GLU) at 50-mmol kg(-1) of soil on Cd, Cu, Pb, and Zn distribution between a contaminated soil and Paulownia tomentosa was investigated. TAR and GLU were applied by a single or a double dosage, the latter carried out with an interval between the two applications of thirty days. The comparison of the differences in mean amounts of metals accumulated in the whole plant at the end of single and double TAR and GLU application experiments indicated the positive effect of repeated GLU applications on the accumulation of Cu, Pb, and Zn by Paulownia tomentosa as compared to untreated controls. A similar effect was not observed for the TAR treatments. When soil treated with either TAR or GLU was compared with untreated controls, no significant effect on heavy-metal concentrations in the soil solution was observed 30 days after treatment, suggesting the absence of an increase of the long-term leaching risk of heavy metals in aquifers and surface waters due to the ligand application. A cost analysis of the treatment is also reported. PMID:21598764

  18. Band alignment of type I at (100)ZnTe/PbSe interface

    NASA Astrophysics Data System (ADS)

    Konovalov, Igor; Emelianov, Vitali; Linke, Ralf

    2016-06-01

    A junction of lattice-matched cubic semiconductors ZnTe and PbSe results in a band alignment of type I so that the narrow band gap of PbSe is completely within the wider band gap of ZnTe. The valence band offset of 0.27 eV was found, representing a minor barrier during injection of holes from PbSe into ZnTe. Simple linear extrapolation of the valence band edge results in a smaller calculated band offset, but a more elaborate square root approximation was used instead, which accounts for parabolic bands. PbSe was electrodeposited at room temperature with and without Cd2+ ions in the electrolyte. Although Cd adsorbs at the surface, the presence of Cd in the electrolyte does not influence the band offset.

  19. A numerical transport model for predicting the distributions of Cd, Cu, Ni, Pb and Zn in the southern North Sea: the sensitivity of model results to the uncertainties in the magnitudes of metal inputs

    NASA Astrophysics Data System (ADS)

    Tappin, A. D.; Burton, J. D.; Millward, G. E.; Statham, P. J.

    1997-10-01

    A new transport model for metals (named NOSTRADAMUS) has been developed to predict concentrations and distributions of Cd, Cu, Ni, Pb and Zn in the southern North Sea. NOSTRADAMUS is comprised of components for water, inorganic and organic suspended particulate matter transport; a primary production module contributes to the latter component. Metal exchange between dissolved (water) and total suspended particulate matter (inorganic + organic) phases is driven by distribution coefficients. Transport is based on an existent 2-D vertically integrated model, incorporating a 35 × 35 km grid. NOSTRADAMUS is largely driven by data obtained during the Natural Environment Research Council North Sea Project (NERC NSP). The sensitivity of model predictions to uncertainties in the magnitudes of metal inputs has been tested. Results are reported for a winter period (January 1989) when plankton production was low. Simulated ranges in concentrations in regions influenced by the largest inflows, i.e. the NE English coast and the Southern Bight, are similar to the ranges in the errors of the concentrations estimated at the northern and southern open sea boundaries of the model. Inclusion of uncertainties with respect to atmospheric (up to ± 54%) and riverine (± 30%) inputs makes little difference to the calculated concentrations of both dissolved and particulate fractions within the southern North Sea. When all the errors associated with the inputs are included there is good agreement between computed and observed concentrations, and that for dissolved and particulate Cd, Cu and Zn, and dissolved Ni and Pb, many of the observations fall within, or are close to, the range of values generated by the model. For particulate Pb, model simulations predict concentrations of the right order, but do not reproduce the large scatter in actual concentrations, with simulated concentrations showing a bias towards lower values compared to those observed. A factor which could have contributed

  20. The influence of metal speciation in combustion waste on the efficiency of Cu, Pb, Zn, Cd, Ni and Cr bioleaching in a mixed culture of sulfur-oxidizing and biosurfactant-producing bacteria.

    PubMed

    Karwowska, Ewa; Wojtkowska, Małgorzata; Andrzejewska, Dorota

    2015-12-15

    Metal leachability from ash and combustion slag is related to the physico-chemical properties, including their speciation in the waste. Metals speciation is an important factor that influences the efficiency of metal bioleaching from combustion wastes in a mixed culture of acidophilic and biosurfactant-producing bacteria. It was observed that individual metals tended to occur in different fractions, which reflects their susceptibility to bioleaching. Cr and Ni were readily removed from wastes when present with a high fraction bound to carbonates. Cd and Pb where not effectively bioleached when present in high amounts in a fraction bound to organic matter. The best bioleaching results were obtained for power plant slag, which had a high metal content in the exchangeable, bound to carbonates and bound to Fe and Mg oxides fractions- the metal recovery percentage for Zn, Cu and Ni from this waste exceeded 90%. PMID:26073519

  1. Spectroscopic characterization and biological activity of Zn(II), Cd(II), Sn(II) and Pb(II) complexes with Schiff base derived from pyrrole-2-carboxaldehyde and 2-amino phenol

    NASA Astrophysics Data System (ADS)

    Singh, Bibhesh K.; Prakash, Anant; Rajour, Hemant K.; Bhojak, Narendar; Adhikari, Devjani

    2010-08-01

    A new Schiff base 2-aminophenol-pyrrole-2-carboxaldehyde and its Zn(II), Cd(II), Sn(II) and Pb(II) complexes have been synthesized and characterized by various physicochemical studies. Spectral studies (IR and 1H NMR) indicate deprotonation and coordination of phenolic oxygen along with binding of pyrrole nitrogen, azomethine nitrogen and anion with metal ions. The presence of lattice water molecule(s) has also been confirmed by TG/DTA studies. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The bio-efficacy of the ligand and their complexes has been examined against the growth of bacteria in vitro to evaluate their antimicrobial potential. Molecular structures of the complexes have been optimized by MM2 calculations and suggest a tetrahedral geometry around metal ions.

  2. Concentration of Cu, Zn, Cr, Ni, Cd, and Pb in soil, sugarcane leaf and juice: residual effect of sewage sludge and organic compost application.

    PubMed

    Moretti, Sarah Mello Leite; Bertoncini, Edna Ivani; Vitti, André César; Alleoni, Luís Reynaldo Ferracciú; Abreu-Junior, Cassio Hamilton

    2016-03-01

    Many researchers have evaluated the effects of successive applications of sewage sludge (SS) on soil plant-systems, but most have not taken into account the residual effect of organic matter remaining from prior applications. Furthermore, few studies have been carried out to compare the effects of the agricultural use of SS and sewage sludge compost (SSC). Therefore, we evaluated the residual effect of SS and SSC on the heavy metal concentrations in soil and in sugarcane (Saccharum spp.) leaves and juice. The field experiment was established after the second harvesting of unburned sugarcane, when the organic materials were applied. The SS and SSC rates were (t ha(-1), dry base): 0, 12.5, 25, and 50; and 0, 21, 42, and 84, respectively. All element concentrations in the soil were below the standards established by São Paulo State environmental legislation. SS promoted small increases in Zn concentrations in soil and Cu concentrations in leaves. However, all heavy metals concentrations in the leaves were lower than the limits established for toxic elements and were in accordance with the limits established for micronutrients. There were reductions in the concentrations of Ni and Cu in soil and the concentration of Pb in juice, with increasing rates of SSC. The heavy metal concentrations were very low in the juice. Under humid tropical conditions and with short-term use, SS and SSC containing low heavy metal concentrations did not have negative effects on plants and soil. PMID:26879984

  3. Zn/Cd ratios and cadmium isotope evidence for the classification of lead-zinc deposits

    PubMed Central

    Wen, Hanjie; Zhu, Chuanwei; Zhang, Yuxu; Cloquet, Christophe; Fan, Haifeng; Fu, Shaohong

    2016-01-01

    Lead-zinc deposits are often difficult to classify because clear criteria are lacking. In recent years, new tools, such as Cd and Zn isotopes, have been used to better understand the ore-formation processes and to classify Pb-Zn deposits. Herein, we investigate Cd concentrations, Cd isotope systematics and Zn/Cd ratios in sphalerite from nine Pb-Zn deposits divided into high-temperature systems (e.g., porphyry), low-temperature systems (e.g., Mississippi Valley type [MVT]) and exhalative systems (e.g., sedimentary exhalative [SEDEX]). Our results showed little evidence of fractionation in the high-temperature systems. In the low-temperature systems, Cd concentrations were the highest, but were also highly variable, a result consistent with the higher fractionation of Cd at low temperatures. The δ114/110Cd values in low-temperature systems were enriched in heavier isotopes (mean of 0.32 ± 0.31‰). Exhalative systems had the lowest Cd concentrations, with a mean δ114/110Cd value of 0.12 ± 0.50‰. We thus conclude that different ore-formation systems result in different characteristic Cd concentrations and fraction levels and that low-temperature processes lead to the most significant fractionation of Cd. Therefore, Cd distribution and isotopic studies can support better understanding of the geochemistry of ore-formation processes and the classification of Pb-Zn deposits. PMID:27121538

  4. Tellurium antisites in CdZnTe

    NASA Astrophysics Data System (ADS)

    Chu, Muren; Terterian, Sevag; Ting, David; James, Ralph B.; Erickson, Jay C.; Yao, H. Walter; Lam, Terrance T.; Szawlowski, Marek; Szczebiot, Richard W.

    2001-12-01

    The n-type conduction of CdTe and Cd0.96Zn0.04Te crystals grown from melts with excess tellurium indicates that the origin of the donors with an energy level at 0.01 eV below the conduction band are most likely singly ionized tellurium antisites instead of cadmium interstitials. Based on this model, the deep level at 0.75 eV below the conduction band is therefore doubly ionized tellurium antisites. After increasing the zinc content over 7%, CdZnTe turns to p-type. The conduction type variation of CdZnTe crystals as a function of zinc contents is explained by the compensation between the donors of Te-antisites and the acceptors of Cd vacancies. High resitivity Cd0.9Zn0.1Te crystals are produced by compensating the p-type crystals with indium at a low doping level of 1- 5x1015 cm-3. At room temperature, the high yield CdZnTe radiation detectors can resolve the six low energy peaks from the Am241 source, a performance comparable to the best reported CdZnTe detectors.

  5. Localisation and quantification of elements within seeds of Cd/Zn hyperaccumulator Thlaspi praecox by micro-PIXE.

    PubMed

    Vogel-Mikus, Katarina; Pongrac, Paula; Kump, Peter; Necemer, Marijan; Simcic, Jure; Pelicon, Primoz; Budnar, Milos; Povh, Bogdan; Regvar, Marjana

    2007-05-01

    Cd, Zn and Pb accumulation, spatial distribution within seeds and germinating seedlings, and seeds fitness of metal hyperaccumulating Thlaspi praecox were investigated in order to gain more knowledge on plant reproductive success at metal polluted sites. The seeds contained up to 1351 microg g-1 (dry weight) of Cd, 121 microg g-1 of Zn and 17 microg g-1 of Pb. Seed fitness was negatively influenced by seed Cd hyperaccumulation. Nevertheless, the viability of seeds was decreased by maximally 20%, indicating very efficient tolerance of the plant embryos to Cd. Localisation by micro-PIXE revealed preferential storage of most elements in the embryonic axis. Cd and Zn were preferentially localised in the epidermis of cotyledons. The restriction of seed Pb and Zn uptake and hyperaccumulation of Cd, accompanied by partitioning of Cd in the epidermal tissues of cotyledons, may enable the survival of T. praecox embryos and seedlings in Cd polluted environments. PMID:17070633

  6. Primary charge carrier dynamics of water-solubilized CdZnS/ZnS core/shell and CdZnS/ZnS·Pd nanoparticle adducts

    NASA Astrophysics Data System (ADS)

    Busby, Erik; Thibert, Arthur; Page, Leah E.; Jawaid, Ali M.; Snee, Preston T.; Larsen, Delmar S.

    2013-06-01

    The primary photodynamics of 5-nm CdZnS core, CdZnS/ZnS core/shell, and CdZnS/ZnS·Pd nanoparticle adducts are characterized with broadband ultrafast transient absorption spectroscopy. Photogenerated excitons in the CdZnS and CdZnS/ZnS nanoparticles exhibit long-lived (>20 ns) lifetimes and further functionalizing of the type-I CdZnS/ZnS core/shells with Pd nanoparticles resulted in rapid exciton quenching (<250 ps) due to the transfer of electrons from the CdZnS core into the Pd nanocrystals via tunneling through the insulating ZnS shell. The shell-induced surface trap passivation and near-unity charge carrier injection efficiency into a platinum-group metal nanoparticle shows potential for enhanced colloidal photocatalytic applications, while enhancing photostability.

  7. Robust Pb2+ sensor based on flexible ZnO/ZnS core-shell nanoarrays

    NASA Astrophysics Data System (ADS)

    Zhao, Zhenfu; Jiang, Chunyan; Pu, Xiong; Du, Chunhua; Li, Linxuan; Ma, Bei; Hu, Weiguo

    2016-04-01

    We designed a flexible robust sensor with ZnO/ZnS core-shell nanoarrays to detect Pb2+ ions. This device is powered by electrical energy transferred from the environmental mechanical energy and senses Pb2+ ions with the cation exchange reaction between ZnS shell and Pb2+ ions (ZnS (s) + Pb2+ (aq) ↔ PbS (s) + Zn2+(aq)). The high density intrinsic carriers in PbS diffuse into the ZnO core to partly screen the piezopotential, which results in an exponential relationship between the concentrations of Pb2+ ions and the piezo-voltages. The detected limit is as low as 1 ppm. This sensor also exhibits a very high selectivity towards Pb2+ ions due to the limitation of energy band and solubility, which has potential applications in environmental protection and pollutant surveillance.

  8. Primary minerals of Zn-Pb mining and metallurgical dumps and their environmental behavior at Plombières, Belgium

    NASA Astrophysics Data System (ADS)

    Kucha, H.; Martens, A.; Ottenburgs, R.; de Vos, W.; Viaene, W.

    1996-02-01

    The primary phases and minerals of the Plombières dumps include typical smelting furnace products such as metallic Fe, Pb, Cu, Zn, Fe-Zn alloys, carbides, phosphides, sulfides of Fe, Zn, Pb, Cu, Mn (alabandite), and FeAs. Spinels, mainly of Fe and Al, are common constituents of the primary assemblage; substitution by Zn, V, Cr, Ti, Mg, and Ca occurs. Primary phases also include the most common Zn-rich fayalite, Zn-rich Ca-Fe silicates, melilite, corundum, and apatite. Most of the Zn is incorporated in iron silicates, ZnO and ZnS. Lead occurs mainly as PbS, metallic lead, and is also present in coal residues. Cadmium is found mainly in metallic zinc and its alloys and in ZnO. The dumps also contain mining wastes composed of pyrite, melnikovite, and iron oxides produced by natural weathering of Zn-Pb ores. Melnikovite and iron oxides are rich in As, Pb, and Zn and possess an increased content of Tl. Leaching tests carried out on the surfaces of polished sections indicate that acid rain (solutions I and II) will mobilize mainly Zn and Cd and, to a much smaller extent, Pb and Sb. Leaching of metals by sulfate-chloride fluids present in the pore network of dumps (solutions III, IV, and V) depends on the pH, which in the dumps is controlled by the proportion of carbonates to sulfides. The more acid fluids leach both sulfides and silicates.

  9. Synthesis of near-infrared-emitting CdTe/CdSe/ZnSe/ZnS heterostructure.

    PubMed

    Yang, Ping

    2014-04-01

    Near-infrared-emitting quantum dots (QDs) were fabricated via organic synthesis strategies through constructing CdTe/CdSe/ZnSe/ZnS multishell heterostructure. An effective shell-coating route was developed for multishell growth on CdTe cores. Core/shell growth was monitored by absorption and photoluminescence (PL) spectroscopy and transmission electron microscopy observation. Yellow emitting CdTe cores were coated with a CdSe shell to generate type II structure. This yields core/shell QDs with red photoluminescence. The passivation by the ZnSe shell having a substantially wide bandgap confines the excitons within the CdTe/CdSe interface and isolates them from the solution environment and consequently improves the stability of the heterostructure. An additional ZnS shell was deposited around the outer layer of CdTe/CdSe/ZnSe QDs to form a heterostructure through the reaction between zinc oleate and trioctylphosphine sulfur in the crude CdTe/CdSe/ZnSe solution. By varying CdTe core size and each shell thickness, the PL wavelength of the obtained heterostructure can span from 580 to 770 nm. The PL efficiency is quenched in CdTe QDs in diluted solution but increases substantially up to 24% for CdTe/CdSe core/shell QDs. The PL efficiency of CdTe/CdSe/ZnSe/ZnS QDs with average diameter of 5.4 nm and a PL peak wavelength of 770 nm is 20%. PMID:24734747

  10. Impacts of anthropogenic pressures on the water quality of the Gironde Estuary (SW France) from the Urban Agglomeration of Bordeaux: spatial characterization and inputs of trace metal elements (Ag, As, Cd, Cu, Pb and Zn)

    NASA Astrophysics Data System (ADS)

    Kessaci, Kahina; Coynel, Alexandra; Blanc, Gérard; Deycard, Victoria N.; Derriennic, Hervé; Schäfer, Jörg

    2014-05-01

    Recent European legislation (2000/60/CE) has listed eight trace metal elements as priority toxic substances for water quality. Urban metal inputs into hydrosystems are of increasing interest to both scientists and managers facing restrictive environmental protection policies, population increase and changing metal applications. The Gironde Estuary (SW France; 625 km2) is known for its metal/metalloid pollution originating from industrial (e.g. Cd, Zn, Cu, As, Ag, Hg) or agricultural sources (e.g. Cu) in the main fluvial tributaries (Garonne and Dordogne Rivers). However, little peer-reviewed scientific work has addressed the impact of urban sources on the Gironde Estuary, especially the Urban Agglomeration of Bordeaux (~1 million inhabitants) located on the downstream branch of the Garonne River. In this study, a snapshot sampling campaign was performed in 2011 for characterizing the spatial distribution of dissolved and particulate metal/metalloid (As, Ag, Cd, Pb, Zn, Cu) concentrations in three suburban watersheds: the Jalle of Blanquefort (330 km2), Eau Bourde (140 km2), and Peugue (112 km2). Furthermore, particulate metal Enrichment Factors (EF) were calculated using local geochemical background measured at the bottom of a sediment core (492 cm). Results indicated that metal concentrations displayed a high spatial variability depending on the suburban watershed and the studied element. Local concentrations anomalies were observed for: (i) As in the Eau Bourde River in dissolved (4.2 μg/l) and particulate phases (246 mg/kg; EF= 20) and attributed to a nearby industrial incinerator; (ii) Zn in the Peugue River with maximum dissolved and particulate concentrations of 87 μg/l and 1580 mg/kg (EF=17), respectively, probably due to urban habitation runoff; (iii) Ag in the Jalle of Blanquefort River with high dissolved (74 ng/l) and particulate concentrations (33.7 mg/kg; EF=117) due to industrial activities in the downstream part. Based on hydro

  11. The accumulation of elements in plants growing spontaneously on small heaps left by the historical Zn-Pb ore mining.

    PubMed

    Stefanowicz, Anna M; Stanek, Małgorzata; Woch, Marcin W; Kapusta, Paweł

    2016-04-01

    The study evaluated the levels of nine metals, namely Ca, Cd, Fe, K, Mg, Mn, Pb, Tl, and Zn, in soils and tissues of ten plant species growing spontaneously on heaps left by historical mining for Zn-Pb ores. The concentrations of Cd, Pb, Tl, and Zn in heap soils were much higher than in control soils. Plants growing on heaps accumulated excessive amounts of these elements in tissues, on average 1.3-52 mg Cd kg(-1), 9.4-254 mg Pb kg(-1), 0.06-23 mg Tl kg(-1) and 134-1479 mg Zn kg(-1) in comparison to 0.5-1.1 mg Cd kg(-1), 2.1-11 mg Pb kg(-1), 0.02-0.06 mg Tl kg(-1), and 23-124 mg Zn kg(-1) in control plants. The highest concentrations of Cd, Pb, and Zn were found in the roots of Euphorbia cyparissias, Fragaria vesca, and Potentilla arenaria, and Tl in Plantago lanceolata. Many species growing on heaps were enriched in K and Mg, and depleted in Ca, Fe, and Mn. The concentrations of all elements in plant tissues were dependent on species, organ (root vs. shoot), and species-organ interactions. Average concentrations of Ca, K, and Mg were generally higher in shoots than in roots or similar in the two organs, whereas Cd, Fe, Pb, Tl, and Zn were accumulated predominantly in the roots. Our results imply that heaps left by historical mining for Zn-Pb ores may pose a potential threat to the environment and human health. PMID:26635220

  12. Voltammetric determination of Pb, Cd, Zn, Cu and Se in milk and dairy products collected from Iran: An emphasis on permissible limits and risk assessment of exposure to heavy metals.

    PubMed

    Shahbazi, Yasser; Ahmadi, Farhad; Fakhari, Farnoosh

    2016-02-01

    This study was carried out to determine the concentrations of some heavy metals in dairy products, collected from five industrial regions in Iran (n = 250 samples) during winter and summer in 2013. The samples were analyzed using the differential pulse anodic and cathodic stripping voltammetry technique. The obtained ranges of mean Pb, Cd, Cu, Zn and Se were as follow: in raw milk 14.0, 1.11, 427, 571, 2.19 μg kg(-1), in pasteurized milk 9.59, 1.0, 378, 447, 1.78 μg kg(-1), in cheese 14.5, 1.25, 428, 586, 1.68 μg kg(-1), in yoghurt 7.54, 0.99, 399, 431, 1.23 μg kg(-1) and in doogh 7.2, 0.84, 320, 369, 0.99 μg kg(-1), respectively. In nearly all cases the concentrations of the metals were below the international permissible limits and do not pose a health concern for the consumption of milk and dairy products in Iran. PMID:26304448

  13. Determination of trace Cd, Cu, Fe, Pb and Zn in diesel and gasoline by inductively coupled plasma mass spectrometry after sample clean up with hollow fiber solid phase microextraction system

    NASA Astrophysics Data System (ADS)

    Nomngongo, Philiswa N.; Ngila, J. Catherine

    2014-08-01

    This study reports a simple and efficient method for the determination of trace Cd, Cu, Fe, Pb and Zn in diesel and gasoline samples by inductively coupled plasma mass spectrometry after matrix removal and analyte pre-concentration using hollow fiber-solid phase microextraction (HF-SPME). The optimization of HF-SPME procedure was carried out using two-level full factorial and central composite designs. Four factors (variables), that are, sample solution pH, acceptor phase amount, extraction time and eluent concentration were optimized. Under the optimized experimental conditions, the precision was ≤ 3% (C = 10 μg L- 1, n = 15), limits of detection and quantification ranged from 0.1 to 0.3 μg L- 1 and 0.3-0.9 μg L- 1, respectively, and the maximum preconcentration factor was 30. The HF-SPME method was applied for the determination of trace metals in real gasoline and diesel samples.

  14. Spectroscopic properties of some new azo-azomethine ligands in the presence of Cu2+, Pb2+, Hg2+, Co2+, Ni2+, Cd2+ and Zn2+ and their antioxidant activity

    NASA Astrophysics Data System (ADS)

    Shaghaghi, Zohreh

    2014-10-01

    Due to their potential applicability as selective receptors in optical sensors, two novel azo Schiff-base derivatives I and II are synthesized and characterized with FT-IR, 1H NMR and elemental analysis techniques. The optical response of azo groups of I and II towards Ni2+, Co2+, Cu2+, Pb2+, Hg2+, Zn2+ and Cd2+ metal ions is studied in DMSO by UV-vis spectroscopy. The absorption spectra of both compounds with cations show marked changes. In solution, azo Schiff-base I produces a cation induced 95 nm blue shift for Cu2+ ion from 555 nm to 460 nm with remarkable color change from red to yellow. Whereas no significant color change is observed upon addition of studied metal cations to the solution of ligand II or other metal ions to the solution of ligand I. Furthermore, Job's plot indicate 1:1 binding-stoichiometry for I with Cu2+ ion and Benesi-Hildebrand plot is used for the determination of its association constant. Therefore receptor I is highly specific for copper ions in DMSO solution. Finally, the study of antioxidant properties of I and II with DPPH method reveals high and significant activities.

  15. Spectroscopic properties of some new azo-azomethine ligands in the presence of Cu(2+), Pb(2+), Hg(2+), Co(2+), Ni(2+), Cd(2+) and Zn(2+) and their antioxidant activity.

    PubMed

    Shaghaghi, Zohreh

    2014-10-15

    Due to their potential applicability as selective receptors in optical sensors, two novel azo Schiff-base derivatives I and II are synthesized and characterized with FT-IR, (1)H NMR and elemental analysis techniques. The optical response of azo groups of I and II towards Ni(2+), Co(2+), Cu(2+), Pb(2+), Hg(2+), Zn(2+) and Cd(2+) metal ions is studied in DMSO by UV-vis spectroscopy. The absorption spectra of both compounds with cations show marked changes. In solution, azo Schiff-base I produces a cation induced 95nm blue shift for Cu(2+) ion from 555nm to 460nm with remarkable color change from red to yellow. Whereas no significant color change is observed upon addition of studied metal cations to the solution of ligand II or other metal ions to the solution of ligand I. Furthermore, Job's plot indicate 1:1 binding-stoichiometry for I with Cu(2+) ion and Benesi-Hildebrand plot is used for the determination of its association constant. Therefore receptor I is highly specific for copper ions in DMSO solution. Finally, the study of antioxidant properties of I and II with DPPH method reveals high and significant activities. PMID:24820324

  16. Study on the relationship between speciation of heavy metals and their ecotoxicity. I. Toxicity of Cu, Cd, Pb and Zn in seawater to three marine algae in the presence of different complexation agents

    NASA Astrophysics Data System (ADS)

    Zhang, Manping; Wang, Juying; Bao, Junbo

    1992-09-01

    Heavy metal is a main pollutant in the marine ecosystem, so study on the effect of heavy metal on phytoplankton is important. Algae ( Chaetoceros sp., Dunaliella sp., Dicrateria zhanjiangenis Hu. var. sp.) were laboratory cultured to observe the effect of heavy metals on their growth. The effect of different metal ion concentration, the detoxication effect of complexation agents and the growth of algae in different media and different nutrition levels were studied to evaluate the effect of metal speciation. It is proved that trace amount of heavy metals can stimulate the growth of algae cells but that high concentration is lethal. The sequence of toxicity is Cd2+>Zn2+>Pb2+. In ordinary nutrition conditions, the detoxication sequence of complexation agents to Chaetoceros sp. is EDTA >sodium salicylate>sodium oxalate >sodium citrate>sulfanilic acid>O-phenanthroline. This is in good conformity with the stability constant sequence of these agents with copper and good evidence that toxicity of metal ion is related to its activity and not to its total concentration.

  17. Chitosan film loaded with silver nanoparticles-sorbent for solid phase extraction of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II).

    PubMed

    Djerahov, Lubomir; Vasileva, Penka; Karadjova, Irina; Kurakalva, Rama Mohan; Aradhi, Keshav Krishna

    2016-08-20

    The present study describes the ecofriendly method for the preparation of chitosan film loaded with silver nanoparticles (CS-AgNPs) and application of this film as efficient sorbent for separation and enrichment of Al(III), Cd(II), Cu(II), Co(II), Fe(III), Ni(II), Pb(II) and Zn(II). The stable CS-AgNPs colloid was prepared by dispersing the AgNPs sol in chitosan solution at appropriate ratio and further used to obtain a cast film with very good stability under storage and good mechanical strength for easy handling in aqueous medium. The incorporation of AgNPs in the structure of CS film and interaction between the polymer matrix and nanoparticles were confirmed by UV-vis and FTIR spectroscopy. The homogeneously embedded AgNPs (average diameter 29nm, TEM analysis) were clearly observed throughout the film by SEM. The CS-AgNPs nanocomposite film shows high sorption activity toward trace metals under optimized chemical conditions. The results suggest that the CS-AgNPs nanocomposite film can be feasibly used as a novel sorbent material for solid-phase extraction of metal pollutants from surface waters. PMID:27178907

  18. Abandoned PbZn mining wastes and their mobility as proxy to toxicity: A review.

    PubMed

    Gutiérrez, Mélida; Mickus, Kevin; Camacho, Lucy Mar

    2016-09-15

    Lead and zinc (PbZn) mines are a common occurrence worldwide; and while approximately 240 mines are active, the vast majority have been abandoned for decades. Abandoned mining wastes represent a serious environmental hazard, as Pb, Zn and associated metals are continuously released into the environment, threatening the health of humans and affecting ecosystems. Iron sulfide minerals, when present, can form acid mine drainage and increase the toxicity by mobilizing the metals into more bioavailable forms. Remediation of the metal waste is costly and, in the case of abandoned wastes, the responsible party(ies) for the cleanup can be difficult to determine, which makes remediation a complex and lengthy process. In this review, we provide a common ground from a wide variety of investigations about concentrations, chemical associations, and potential mobility of Pb, Zn and cadmium (Cd) near abandoned PbZn mines. Comparing mobility results is a challenging task, as instead of one standard methodology, there are 4-5 different methods reported. Results show that, as a general consensus, the metal content of soils and sediments vary roughly around 1000mg/kg for Zn, 100 for Pb and 10 for Cd, and mobilities of Cd>Zn>Pb. Also, mobility is a function of pH, particle size, and formation of secondary minerals. New and novel remediation techniques continue to be developed in laboratories but have seldom been applied to the field. Remediation at most of the sites has consisted of neutralization (e.g. lime,) for acid mine discharge, and leveling followed by phytostabilization. In the latter, amendments (e.g. biochar, fertilizers) are added to boost the efficiency of the treatment. Any remediation method has to be tested before being implemented as the best treatment is site-specific. Potential treatments are described and compared. PMID:27179321

  19. High temperature continuous flow synthesis of CdSe/CdS/ZnS, CdS/ZnS, and CdSeS/ZnS nanocrystals.

    PubMed

    Naughton, Matt S; Kumar, Vivek; Bonita, Yolanda; Deshpande, Kishori; Kenis, Paul J A

    2015-10-14

    Continuous flow reactors show great promise for large-scale synthesis of quantum dots. Here, we discuss results for the synthesis of multi-layered Cd-based hybrid nanocrystals - CdSe/CdS/ZnS, CdS/ZnS, and CdSeS/ZnS - in a continuous flow reactor. The simple reactor design and liquid-phase chemistry obviate the need for preheating or in-line mixing, and the chosen reactor dimensions and operating conditions allow for high flow rates (∼10 mL min(-1)). Additionally, the simple reactor design is well suited for scale-up. The CdSe/CdS/ZnS particles synthesized at elevated temperatures in the reactor exhibit quantum yields of over 60% at longer wavelengths (red region). The shell growth for these particles is conducted without the need for complex dropwise addition or SILAR shell growth procedures used in batch reactors. CdS-based particles were shown to have a higher performance when using octadecene-S instead of TOP-S, which improved the quality of shell growth. In addition, stoichiometric synthesis of the alternate CdSeS/ZnS alloy particles was conducted, removing the need for a large excess of S to offset the lower S reactivity. CdSeS/ZnS alloy nanoparticles exhibit quantum yields of about 50% in the intermediate wavelength range (500-600 nm). PMID:26361342

  20. Concentrations, spatial distribution, and risk assessment of soil heavy metals in a Zn-Pb mine district in southern China.

    PubMed

    Qi, Jianying; Zhang, Hailong; Li, Xiangping; Lu, Jian; Zhang, Gaosheng

    2016-07-01

    China is one of the largest producers and consumers of lead and zinc in the world. Lead and zinc mining and smelting can release hazardous heavy metals such as Cd, Pb, Zn, and As into soils, exerting health risks to human by chronic exposure. The concentrations of Cd, Zn, Pb, and As in soil samples collected from a Pb-Zn mining area with exploitation history of 60 years were investigated. Health risks of the heavy metals in soil were evaluated using US Environmental Protection Agency (US EPA) recommended method. A geo-statistical technique (Kriging) was used for the interpolation of heavy metals pollution and Hazard Index (HI). The results indicated that the long-term Pb/Zn mining activities caused the serious pollution in the local soil. The concentrations of Cd, As, Pb, and Zn in topsoil were 40.3 ± 6.3, 103.7 ± 37.3, 3518.4 ± 896.1, and 10,413 ± 2973.2 mg/kg dry weight, respectively. The spatial distribution of the four metals possessed similar patterns, with higher concentrations around Aayiken (AYK), Maseka (MSK), and Kuangshan (KS) area and more rapidly dropped concentrations at upwind direction than those at downwind direction. The main pollutions of Cd and Zn were found in the upper 60 cm, the Pb was found in the upper 40 cm, and the As was in the upper 20 cm. The mobility of metals in soil profile of study area was classed as Cd > Zn ≫ Pb > As. Results indicated that there was a higher health risk (child higher than adult) in the study area. Pb contributed to the highest Hazard Quotient (57.0 ~ 73.9 %) for the Hazard Index. PMID:27315126

  1. Pb and Zn release from crustal sediments during metamorphism

    NASA Astrophysics Data System (ADS)

    Hammerli, Johannes; Spandler, Carl; Oliver, Nick; Sossi, Paolo; Dipple, Greg

    2015-04-01

    Our understanding of the genesis of Pb-Zn ore systems is currently limited by a lack of knowledge about from where these metals are sourced. While it is generally agreed that the temperature and salinity of fluids play a crucial role in mobilizing metals, the importance of the composition of the source lithologies is poorly constrained. Furthermore, fluid-rock processes that lead to element mobility are yet to be fully understood, especially in metamorphic environments. To address these gaps in our knowledge we examine metal distribution and mobility in rocks from a prograde metamorphic sequence of the Mt Lofty Ranges, South Australia, where temperatures range from ~300 to 700˚C at ~3.5 to 5 kbar. This regional metamorphic belt underwent regional up-temperature fluid flow, which allowed for favourable conditions for enhanced element mobility. By studying the distribution and concentration of Pb and Zn on both bulk-rock and mineral scales, in combination with bulk rock Zn-isotope data, we can monitor the behaviour of these elements during pressure and temperature changes. Our results show that in staurolite-absent siliciclastic metasedimentary rocks, biotite contains >80% of the bulk rock Zn, as well as a considerable proportion of the total Pb, irrespective of the metamorphic grade. Pervasive fluid flow during metamorphism through these metasedimentary rocks led to a continuous depletion of Pb and Zn on a mineral and bulk-rock scale, resulting in a mobilization of ~80% of the bulk-rock Zn and ~50% of the bulk-rock Pb, mainly through reactions involving biotite. We calculated that a minimum of 2.7Mt of Pb and 27Mt of Zn was mobilized/lost in the high-grade metamorphic zone (200 km2). Halogen contents of apatite and biotite and bulk-rock Zn isotope data provide evidence that Cl-rich metamorphic fluids were important for metal transport. Hence, fluid flow accompanying metamorphism of typical sedimentary rocks can mobilize base metals to the degree required to form

  2. Solar paint of ZnO/CdS and ZnO/CdSe based on commercial ZnO

    NASA Astrophysics Data System (ADS)

    Guo, Yi; Zhang, Xiang; Li, Yanhong; Li, Yanmei; Hu, Chunli; Zhou, Xingfu

    2016-03-01

    We report a facile and cheap route to the fabrication of ZnO/CdS and ZnO/CdSe based on commercial ZnO particles. The obtained product can be directly brush printed as solar paint. The results show that the solar cell based on the mixture of ZnO/CdS and ZnO/CdSe have a better light absorption and electron transport ability, and a high power conversion efficiency (PCE) of 1.36% was obtained, which is the highest PCE reported for inorganic paint-based solar cells to date. This method greatly simplifies the process of the solar cell fabrication and opens a door toward the cheap and printable solar paint based on commercial available materials.

  3. Resistive switching properties in CdZnTe films

    SciTech Connect

    Zha, Gangqiang; Lin, Yun; Tan, Tingting; Jie, Wanqi; Zeng, Dongmei

    2015-02-09

    The ternary II–VI compound semiconductor cadmium zinc telluride (CdZnTe) has bi-stable conduction characteristics. In this letter, CdZnTe films are grown on indium tin oxide (ITO) substrates by radio frequency magnetron sputtering. The current-voltage characteristics show that there is resistive switching in a structure consisting of an 800-nm-thick CdZnTe film, an Au Schottky contact, and an ITO bottom electrode. The electroresistance in Au/CdZnTe/ITO may be related to the polarization of the CdZnTe film and the Schottky contact.

  4. Geogenic and Anthropogenic Moss Responsiveness to Element Distribution Around a Pb-Zn Mine, Toranica, Republic of Macedonia.

    PubMed

    Angelovska, Svetlana; Stafilov, Trajče; Šajn, Robert; Balabanova, Biljana

    2016-04-01

    Moss species (Homalothecium lutescens, Hypnum cupressiforme, Brachythecium glareosum, and Campthotecium lutescens) were used as suitable sampling media for biomonitoring the origin of heavy-metal pollution in the lead-zinc (Pb-Zn) mine "Toranica" near the Kriva Palanka town, Eastern Macedonia. The contents of 20 elements-silver (Ag), aluminum (Al), arsenic (As), barium (Ba), calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), potassium (K), lithium (Li), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), Pb, strontium (Sr), vanadium (V), and (Zn) were determined by atomic emission spectrometry with inductively coupled plasma. Data processing was applied with combinations of multivariate statistical methods: factor analysis, principal component analysis, and cluster analysis. Moss' responsiveness to the atmospheric distribution of the selected elements was investigated in correlation to the specific geology of the region (soil dusting). Lithogenic distribution was characterized with the distribution of three dominant geochemical associations: F1: Al-Li-V-Cr-Ni-Co, F2: Ba-Ca-Sr, and F3: Cd-Zn-Pb-Cu. Spatial distribution was constructed for visualization of the factor deposition. Furthermore, air distribution (passive biomonitoring) versus soil geochemistry of the analyzed elements was examined. Significant correlations were singled out for Pb, Zn, and Cd and for Mg(moss)/Na(soil). Characteristic lithological anomaly characterized the presence of the oldest geological volcanic rocks. Zone 1 (Pb-Zn mine surrounding) presents a unique area with hydrothermal action of Pb-Zn mineralization leading to polymetallic enrichments in soil. This phenomenon strongly affects the environment, which is a natural geochemical imprint in this unique area (described with the strong dominance of the geochemical association Cd-Zn-Pb-Cu). PMID:26888226

  5. High temperature continuous flow synthesis of CdSe/CdS/ZnS, CdS/ZnS, and CdSeS/ZnS nanocrystals

    NASA Astrophysics Data System (ADS)

    Naughton, Matt S.; Kumar, Vivek; Bonita, Yolanda; Deshpande, Kishori; Kenis, Paul J. A.

    2015-09-01

    Continuous flow reactors show great promise for large-scale synthesis of quantum dots. Here, we discuss results for the synthesis of multi-layered Cd-based hybrid nanocrystals - CdSe/CdS/ZnS, CdS/ZnS, and CdSeS/ZnS - in a continuous flow reactor. The simple reactor design and liquid-phase chemistry obviate the need for preheating or in-line mixing, and the chosen reactor dimensions and operating conditions allow for high flow rates (~10 mL min-1). Additionally, the simple reactor design is well suited for scale-up. The CdSe/CdS/ZnS particles synthesized at elevated temperatures in the reactor exhibit quantum yields of over 60% at longer wavelengths (red region). The shell growth for these particles is conducted without the need for complex dropwise addition or SILAR shell growth procedures used in batch reactors. CdS-based particles were shown to have a higher performance when using octadecene-S instead of TOP-S, which improved the quality of shell growth. In addition, stoichiometric synthesis of the alternate CdSeS/ZnS alloy particles was conducted, removing the need for a large excess of S to offset the lower S reactivity. CdSeS/ZnS alloy nanoparticles exhibit quantum yields of about 50% in the intermediate wavelength range (500-600 nm).Continuous flow reactors show great promise for large-scale synthesis of quantum dots. Here, we discuss results for the synthesis of multi-layered Cd-based hybrid nanocrystals - CdSe/CdS/ZnS, CdS/ZnS, and CdSeS/ZnS - in a continuous flow reactor. The simple reactor design and liquid-phase chemistry obviate the need for preheating or in-line mixing, and the chosen reactor dimensions and operating conditions allow for high flow rates (~10 mL min-1). Additionally, the simple reactor design is well suited for scale-up. The CdSe/CdS/ZnS particles synthesized at elevated temperatures in the reactor exhibit quantum yields of over 60% at longer wavelengths (red region). The shell growth for these particles is conducted without the need

  6. Photoluminescence study of ZnS and ZnS:Pb nanoparticles

    SciTech Connect

    Virpal, Hastir, Anita; Kaur, Jasmeet; Singh, Gurpreet; Singh, Ravi Chand

    2015-05-15

    Photoluminescence (PL) study of pure and 5wt. % lead doped ZnS prepared by co-precipitation method was conducted at room temperature. The prepared nanoparticles were characterized by X-ray Diffraction (XRD), UV-Visible (UV-Vis) spectrophotometer, Photoluminescence (PL) and Raman spectroscopy. XRD patterns confirm cubic structure of ZnS and PbS in doped sample. The band gap energy value increased in case of Pb doped ZnS nanoparticles. The PL spectrum of pure ZnS was de-convoluted into two peaks centered at 399nm and 441nm which were attributed to defect states of ZnS. In doped sample, a shoulder peak at 389nm and a broad peak centered at 505nm were observed. This broad green emission peak originated due to Pb activated ZnS states.

  7. Photoluminescence study of ZnS and ZnS:Pb nanoparticles

    NASA Astrophysics Data System (ADS)

    Virpal, Hastir, Anita; Kaur, Jasmeet; Singh, Gurpreet; Singh, Ravi Chand

    2015-05-01

    Photoluminescence (PL) study of pure and 5wt. % lead doped ZnS prepared by co-precipitation method was conducted at room temperature. The prepared nanoparticles were characterized by X-ray Diffraction (XRD), UV-Visible (UV-Vis) spectrophotometer, Photoluminescence (PL) and Raman spectroscopy. XRD patterns confirm cubic structure of ZnS and PbS in doped sample. The band gap energy value increased in case of Pb doped ZnS nanoparticles. The PL spectrum of pure ZnS was de-convoluted into two peaks centered at 399nm and 441nm which were attributed to defect states of ZnS. In doped sample, a shoulder peak at 389nm and a broad peak centered at 505nm were observed. This broad green emission peak originated due to Pb activated ZnS states.

  8. Ethanol gas sensing by Zn-doped CdS/CdTe nanoparticles

    NASA Astrophysics Data System (ADS)

    Prabhu, M.; Manikandan, V. S.; Soundararajan, N.; Ramachandran, K.

    2016-05-01

    Zn-doped CdS/CdTe nanoparticles (NPs) were synthesized and studied here for gas sensing. The crystallographic properties of the samples were studied by X-ray diffraction (XRD), which shows cubic structure for CdS and CdTe NPs. The three longitudinal optical phonon modes at 298, 595 and 895 cm-1 were obtained from Raman spectrum and this also reveals the cubic structure of CdS NPs. The band gap for Zn-doped CdS/CdTe NPs increased slightly when compared with pure sample. The ethanol gas sensing in CdS/CdTe NPs shows an enhancement on Zn substitution.

  9. Limitation of Pb and Cd uptake by pine

    SciTech Connect

    Ostrowska, A.; Porebska, G.; Szczubialka, Z.

    2006-07-15

    Model experiments were carried out using 1-year-old pine plants grown in water cultures with the aim of investigating whether and to what extent the accumulation of Pb and Cd in plants can be decreased through decreasing the nutrient solution concentration, supplementing with forest soil, supplementing with calcium carbonate, and addition of brown coal. It was found that with increased doses of Pb and Cd in water cultures pine plants take up more of those elements. Whereas Pb accumulates mainly in the roots, about half of the Cd is transported to the above-ground part of the plants. Addition of Pb, Cd, and forest soil to the nutrition medium increased Pb uptake by pine plants compared to the control treatment. The effect of soil addition was not that evident in the case of Cd uptake. Furthermore, it was observed that addition of brown coal resulted in a slight increase of Pb accumulation in the shoots and in a considerable decrease of its accumulation in roots. A higher increase of Cd accumulation in the shoots was observed after brown coal was added to the nutrient solution. The amounts of Cd and Pb accumulated in plants, mainly in the shoots, decreased following the addition of CaCO{sub 3}. When CaCO{sub 3} and brown coal were added jointly, this effect was markedly more pronounced. The decrease of nutrient supply (down to one-quarter of the original concentration) increased the content of Pb, especially in the roots; for Cd, changes in its content in pine were not univocal.

  10. How phytohormone IAA and chelator EDTA affect lead uptake by Zn/Cd hyperaccumulator Picris divaricata.

    PubMed

    Du, Rui-Jun; He, Er-Kai; Tang, Ye-Tao; Hu, Peng-Jie; Ying, Rong-Rong; Morel, Jean-Louis; Qiu, Rong-Liang

    2011-01-01

    In this paper, the effects of indole-3-acetic acid (IAA) and/or ethylenediaminetetraacetic acid (EDTA) on lead uptake by a Zn/Cd hyperaccumulator Picris divaricata were studied. P. divaricata responded to Pb by better root system and increased biomass in presence of phytohormone IAA, which was able to reduce the inhibiting effects of Pb on transpiration without reducing the uptake of Pb The application of 100 microM IAA increased plant transpiration rate by about 20% and Pb concentration in leaves by about 37.3% as compared to treatment exposed to Pb alone. The enhanced phytoextraction efficiency could be attributed to the mechanisms played by IAA through alleviating Pb toxicity, creating better root system and plant biomass, promoting a higher transpiration rate as well as regulating the level of nutrient elements. On the contrary, inefficiency of phytoextraction was found with EDTA or the combination of IAA and EDTA probably because most Pb was in the form of Pb-EDTA complex which blocked the uptake by P. divaricata. The present study demonstrated that IAA was able to enhance the phytoextraction of Pb by Zn/Cd hyperaccumulator P. divaricata, providing a feasible method for the phytoremediation of polymetallic contaminated soils. PMID:21972569

  11. Long-term changes of metal contents in two metallophyte species (Olkusz area of Zn-Pb ores, Poland).

    PubMed

    Kicińska, Alicja; Gruszecka-Kosowska, Agnieszka

    2016-06-01

    The authors present the changes of the As, Cd, Fe, Mn, Pb and Zn contents in two plant-considered metallophytes: common bent Agrostis capillaris (blades) and birch Betula pendula (leaves and seeds), recorded in a Zn-Pb industrial region of Olkusz (Poland) in 1994 and 2014. The highest amounts of Cd (12 ppm) and Zn (2524 ppm) in the common bent occur in the vicinity of the mining and metallurgical works 'Bolesław' in Bukowno. However, these values are significantly lower than those in 1994: Cd by 87 % and Zn by 52 %. The highest contents of Fe (2674 ppm), Mn (130 ppm) and Pb (334 ppm) in this grass species are in the vicinity of the closed Olkusz mine. These contents have increased in comparison with the 1994 figures: Fe by 56 %, Mn by 120 % and Pb by 6 %. In the birch leaves, the metal contents averaged for four sites are the following: As 2.1, Cd 6.5, Fe 261, Mn 110, Pb 70 and Zn 1657 ppm, being lower from the figures in 1994. The highest As, Fe and Pb contents of birch leaves occur in the habitat closest to the former Olkusz mine, while those of Cd, Mn and Zn in the habitat distant at 100 m from the active plant in Bukowno. The common bent grass generates better resistance mechanisms against the metals than does the birch. In the birch leaves, the contents of the metals are significantly lower than those of the grass blades, but higher from those of the birch seeds collected from the same tree individuals. It is a proof of good functioning of the mechanisms preventing excessive metal amounts from the cell metabolism and of the presence of physiological barriers protecting birch seeds as the generative organs. PMID:27165603

  12. The differentially-expressed proteome in Zn/Cd hyperaccumulator Arabis paniculata Franch. in response to Zn and Cd.

    PubMed

    Zeng, Xiao-Wen; Qiu, Rong-Liang; Ying, Rong-Rong; Tang, Ye-Tao; Tang, Lu; Fang, Xiao-Hang

    2011-01-01

    The Zn/Cd hyperaccumulator Arabis paniculata is able to tolerate high level of Zn and Cd. To clarify the molecular basis of Zn and Cd tolerance, proteomic approaches were applied to identify proteins involved in Zn and Cd stress response in A. paniculata. Plants were exposed to both low and high Zn or Cd levels for 10 d. Proteins of leaves in each treatment were separated by 2-DE (two-dimensional electrophoresis). Nineteen differentially-expressed proteins upon Zn treatments and 18 proteins upon Cd treatments were observed. Seventeen out of 19 of Zn-responsive proteins and 16 out of 18 of Cd-responsive proteins were identified using MALDI-TOF/TOF-MS (matrix-assisted laser desorption/ionization time of flight mass spectrometry). The most of identified proteins were known to function in energy metabolism, xenobiotic/antioxidant defense, cellular metabolism, protein metabolism, suggesting the responses of A. paniculata to Zn and Cd share similar pathway to certain extend. However, the different metal defense was also revealed between Zn and Cd treatment in A. paniculata. These results indicated that A. paniculata against to Zn stress mainly by enhancement of energy metabolism including auxin biosynthesis and protein metabolism to maintain plant growth and correct misfolded proteins. In the case of Cd, plants adopted antioxidative/xenobiotic defense and cellular metabolism to keep cellular redox homeostasis and metal-transportation under Cd stress. PMID:21074242

  13. Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings.

    PubMed

    Huang, Longbin; Li, Xiaofang; Nguyen, Tuan A H

    2015-01-01

    Elevated inorganic phosphate (Pi) concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu)-lead (Pb)-zinc (Zn) mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7), the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5), EHM-TD (fresh Cu-stream, high magnetite content) and local soil (weathered shale and schist), respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed), oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2), ankerite (Ca(Fe Mg)(CO3)2 and siderite (FeCO3), as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,Fe)S, ZnS, (Zn,Cd)S)) may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal. PMID

  14. Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings

    PubMed Central

    Huang, Longbin; Li, Xiaofang; Nguyen, Tuan A. H.

    2015-01-01

    Elevated inorganic phosphate (Pi) concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu)-lead (Pb)-zinc (Zn) mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7), the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5), EHM-TD (fresh Cu-stream, high magnetite content) and local soil (weathered shale and schist), respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed), oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2), ankerite (Ca(Fe Mg)(CO3)2 and siderite (FeCO3), as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,Fe)S, ZnS, (Zn,Cd)S)) may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal. PMID

  15. Sulphide and supergene nonsulphide Zn-Pb deposits of the southern Kootenay Arc, British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Paradis, S.; Simandl, G. J.

    2009-05-01

    The Kootenay Arc (KA) hosts a large number of carbonate-hosted base metal (Zn-Pb) deposits. These deposits occur mainly within the dolomitized limestone of the Lower Cambrian Badshot Formation (or its equivalent the Reeves Member of the Laib Formation), and the Upper Cambrian to Lower Ordovician Nelway Formation. They range in size from 6-10 million tonnes with average grades of 3-4% Zn, 1-2% Pb, 0.4% Cd and traces of Ag. The deposits, their dolomitic envelopes, and the limestone hostrock lie within secondary isoclinal folds along the limbs of regional anticlinal structures. Most of the deposits are stratabound lenticular concentrations of sphalerite, galena, pyrite, local pyrrhotite and rare arsenopyrite in isoclinally folded dolomitized or silicified carbonate layers. Brecciated zones are common within the more massive sulphide mineralization. Several deposits are past producers (e.g., Reeves MacDonald, Jersey, and HB) and others are advanced prospects. They are interpreted as metamorphosed MVT- or Irish-type Pb-Zn deposits. The main concentrations of these deposits define the Salmo and Duncan camps. The near-surface portions of these carbonate-hosted sulphide deposits are weathered and strongly oxidized (supergene environment). They consist of extensive Zn- and Pb-bearing iron oxide gossans and base metal-bearing nonsulphide mineralization. The most common nonsulphide minerals are goethite, hematite, hemimorphite, smithsonite, cerussite, anglesite, and hydrozincite. The Reeves MacDonald, Jersey-Emerald, Lomond, and Oxide group of deposits are the best examples of carbonate-hosted nonsulphide base metal (CHNSBM) deposits in the KA. The shape, mineralogy and paragenesis of the known CHNSBM deposits are indicative of direct-replacement of sulphides by nonsulphide base metal-bearing minerals. Zn-rich (low Pb) CHNSBM deposits commonly form by interaction of Zn-rich fluids with carbonate wallrock (replacement process). Such deposits (consisting of "white ore") may

  16. ZnSe-ZnMnSe and CdTe-CdMnTe superlattices

    NASA Astrophysics Data System (ADS)

    Gunshor, R. L.; Kolodziejski, L. A.; Otsuka, N.; Datta, S.

    1986-08-01

    We report the growth and characterization of superiattices of a new wide-gap, zincblende material system, Zn 1 - xMn xSe. ZnSe exhibiting dominant free excitonic emission in photoluminescence (PL) is the well material, while wider-band-gap Zn 1 - xMn xSe (0.23 < x < 0.66) forms the barrier material. PL measurements show greatly enhanced quantum efficiency compared to films of the ZnSe well material, while transmission electron microscopy shows extremely abrupt interfaces by the presence of seventh-order satellite spots. Previously reported superiattices in the CdTe-CdMnTe material system were grown with the (111) orientation, and exhibit unique excitonic properties believed related to the (111) interfaces. Using various techniques to select (111) or (100) heteroepitaxy of CdTe on (100) GaAs, we report the first (100) superlattices of this material, and compare the optical properties to the previous (111) structures.

  17. Electronic properties of aluminum/CdZnTe interfaces

    NASA Astrophysics Data System (ADS)

    Bai, Xuxu; Jie, Wanqi; Zha, Gangqiang; Zhang, Wenhua; Zhu, Junfa; Wang, Tao; Qian, Dong; Liu, Ying; Jia, Jinfeng

    2013-05-01

    Understanding complex correlations between the macroscopic device performance and the contact formation on the atomic level in CdZnTe radiation detectors remains an enormous challenge. In this work, an effort towards bridging that macro-nano knowledge gap is made by systematic study of the electronic structures in the interface of Al/CdZnTe(111)A and Al/CdZnTe(111)B with Al coverage from sub-monolayer to multilayers using photoemission spectroscopy. Remarkable difference of the electronic states was found in these two interfaces. A strong interaction between Al and CdZnTe(111)A was observed at room temperature and thick interface layers (>12 nm) formed. In contrast, an intermix layer with a thickness of about one atomic layer (˜0.3 nm) was formed at Al/CdZnTe(111)B interface.

  18. Characterization of cadmium biosorption by Exiguobacterium sp. isolated from farmland soil near Cu-Pb-Zn mine.

    PubMed

    Park, Jin Hee; Chon, Hyo-Taek

    2016-06-01

    Bacteria have the ability to bind heavy metals on their cell wall. Biosorption is a passive and energy-independent mechanism to adsorb heavy metals. The efficiency of heavy metal biosorption can vary depending on several factors such as the growth phase of bacteria, solution pH, and existence of competitive heavy metals. In this study, Exiguobacterium sp. isolated from farmland soil near a mine site were used, and optimal conditions for Cd biosorption in solution were investigated. As bacterial growth progressed, Cd biosorption increased, which is attributed to changes in the structure and composition of the cell wall during bacterial growth. The biosorption process was rapid and was completed within 30 min. Cadmium biosorption was highest at pH 7 due to the dissociation of hydrogen ions and the increase of negative charges with increasing pH. In the mixed metal solution of Cd, Pb, and Zn, the amount of biosorption was in the order of Pb>Cd>Zn while in a single metal solution, the order was Cd≥Pb>Zn. The maximum adsorption capacity for Cd by the isolated bacteria was 15.6 mg/g biomass, which was calculated from the Langmuir isotherm model. Different adsorption efficiencies under various environmental conditions indicate that, to control metal mobility, the conditions for biosorption should be optimized before applying bacteria. The results showed that the isolated bacteria can be used to immobilize metals in metal-contaminated wastewater. PMID:26951224

  19. Optical behavior and sensor activity of Pb ions incorporated ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Kannadasan, N.; Shanmugam, N.; Sathishkumar, K.; Cholan, S.; Ponnguzhali, R.; Viruthagiri, G.

    2015-05-01

    We present the synthesis and characterization of nanocrystalline ZnO doped with Pb in different concentrations. The structural and chemical compositions of the products are characterized by XRD, XPS, EDS and FT-IR spectroscopy. The observed results suggest that Pb ions (Pb2+ and Pb4+) are successfully incorporated into the lattice position of Zn2+ ions in ZnO. The optical properties of the products are studied by UV-Vis and room temperature PL measurements. The PL emission spectra of ZnO:Pb, show the intensity quenching for both the UV and visible emissions. The influence of Pb on controlling the size and morphology of ZnO is studied by FESEM and confirmed by HRTEM. Amperometric response shows that ZnO incorporated with 0.075 M of Pb ions has enhanced sensor activity for H2O2 than the undoped product.

  20. ZnCdMgSe-Based Semiconductors for Intersubband Devices

    SciTech Connect

    Tamargo, Maria C.

    2008-11-13

    This paper presents a review of recent results on the application of ZnCdMgSe-based wide bandgap II-VI compounds to intersubband devices such as quantum cascade lasers and quantum well infrared photodetectors operating in the mid-infrared region. The conduction band offset of ZnCdSe/ZnCdMgSe quantum well structures was determined from contactless electroreflectance measurements to be as high as 1.12 eV. FT-IR was used to measure intersubband absorption in multi-quantum well structures in the mid-IR range. Electroluminescence at 4.8 {mu}m was observed from a quantum cascade emitter structure made from these materials. Preliminary results are also presented on self assembled quantum dots of CdSe on ZnCdMgSe, and novel quantum well structures with metastable binary MgSe barriers.

  1. Characterization of CdTe, (Cd,Zn)Te, and Cd(Te,Se) single crystals by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Rai, R. S.; Mahajan, S.; McDevitt, S.; Johnson, C. J.

    1991-10-01

    CdTe, (Cd,Zn)Te, and Cd(Te,Se) crystals grown by the Bridgman technique have been characterized by transmission electron microscopy. Results indicate that the Te precipitates are seen in all the crystals, but their density and size are lowest and largest in the case of Cd(Te,Se) crystals. In addition, dislocations, stacking faults, and microtwins are observed in as-grown CdTe, (Cd,Zn)Te, and Cd(Te,Se) crystals. Arguments have been developed to rationalize these observations and their ramifications on crystal perfection are discussed.

  2. Palaeomagnetism of the Howards Pass Zn-Pb deposits, Yukon, Canada

    NASA Astrophysics Data System (ADS)

    Kawasaki, K.; Symons, D. T. A.

    2012-07-01

    The Howards Pass district is located in the Selwyn Basin, Yukon. The district consists of >15 laminated clastic-dominated (CD) sphalerite-galena (Zn-Pb) deposits in the 'zinc corridor' that trends northwest-southeast and extends for ˜35 km. The stratiform mineralized zone, the Active Member, is hosted in carbonaceous cherts and black shales of the Early Silurian Road River Group. Using mostly thermal and then alternating field step demagnetization isolated a stable characteristic remanent magnetization (ChRM) by the core-magnetization-angle method from 18 sites (339 specimens) in 18 variably oriented exploration drill hole cores from 6 Zn-Pb mineralized panels. Rock magnetic analyses show that the main remanence carriers are single- or pseudosingle-domain pyrrhotite and titanomagnetite. The deposits' mean ChRM direction yields a pole position of either ˜170 Ma on the North American apparent polar wander path or ˜162 Ma on a corrected path for the Intermontane Belt (IMB) terranes. A negative palaeomagnetic fold test indicates that the mineralization's ChRM is post-folding, setting a minimum age for regional metamorphic deformation of ˜170 ± 20 Ma and supporting an Early Jurassic arrival for the IMB's collision and accretion to North America. An autochthonous or para-autochthonous North American tectonic model is favoured for the ChRM of the metamorphosed Selwyn Basin strata rather than an allochthonous IMB model. Further, the palaeomagnetic age indicates that the coarse-grained Zn-Pb mineralization in fine fractures that cut the laminated fine-grained Zn-Pb mineralization at Howards Pass at least was formed by remobilization during Middle Jurassic metamorphism.

  3. Matrix Effects on the MC-ICPMS Analysis of Zn and Cd Isotopes

    NASA Astrophysics Data System (ADS)

    Shiel, A. E.; Weis, D.; Barling, J.; Orians, K. J.

    2006-12-01

    In order to understand fractionation in heavy stable isotope systems, matrix and auto-matrix effects need to be carefully monitored as they have a major impact on the precision and accuracy of isotope measurement by MC-ICP-MS. Understanding their impact for any given isotopic system is an important aspect of method development. In this study we look at auto-matrix and matrix effects for Zn (Cu mass bias correction) and Cd (Ag mass bias correction). Zn and Cd have similarly high ionization potentials, 9.4 and 9.0 respectively, and ionization potentials for Cu and Ag are similar, 7.7 and 7.6 respectively, making for an interesting comparison. All experiments were performed on a Nu Plasma MC-ICP-MS with 5x molar concentration of matrix elements. Experiments were also performed at concentrations more representative of those likely to be found in purified samples. In addition, we tested auto-matrix effects for Cd and Zn by varying the concentration of the analyte and mass bias correcting element. Cd sensitivity is enhanced in the presence of Rb and Pb, and is suppressed in the presence of Al, Sr and Cs. Spiked Cd runs are isotopically lighter than un-spiked runs, as light as 0.4‰/amu. Ag sensitivity was enhanced by all matrix elements. Cu sensitivity is enhanced by Al, Sr and Ba, and Zn sensitivity is enhanced by the latter two and Pb. Zn spiked with Al, Sr and Pb, or with poorly matched Cu intensities is isotopically lighter than un-spiked standards, as light as 1.0‰/amu. Auto-matrix effects for Cd and Ag, if present, are within the analytical error. We demonstrate that the presence of matrix elements or differences in concentration of analyte and mass bias correcting element between sample and standard can produce fractionation that is not true. The matrix effect is also found to be variable, as replicate analyses do not always agree. Cd and Zn react differently to different matrix elements, demonstrating the need for independent evaluation of each isotopic system

  4. Selective transport of Pb2+ and Cd2+ across a phospholipid bilayer by a cyclohexanemonocarboxylic acid-capped 15-crown-5 ether.

    PubMed

    Hamidinia, Shawn A; Steinbaugh, Gregory E; Erdahl, Warren L; Taylor, Richard W; Pfeiffer, Douglas R

    2006-03-01

    A cyclohexanemonocarboxylic acid-capped 15-crown-5 ether was synthesized and found to be effective as an ionophore for Pb2+ and Cd2+, transporting them across a phospholipid bilayer membrane. Transport studies were carried out using 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylcholine (POPC) vesicles containing the chelating indicator 2-([2-bis(carboxymethyl)amino-5-methylphenoxy]methyl)-6-methoxy-8-bis(carboxymethyl)aminoquinoline (Quin-2). Data obtained at pH 7.0 using this system, show that the synthetic ionophore transports divalent cations with the selectivity sequence Pb2+ > Cd2+ > Zn2+ > Mn2+ > Co2+ > Ni2+ > Ca2+ > Sr2+. Selectivity factors, based on the ratio of individual initial cation transport rates, are 280 (Pb2+/Ca2+), 62 (Pb2+/Zn2+), 68 (Cd2+/Ca2+), and 16 (Cd2+/Zn2+). Plots of log initial rate versus logM(n+) or log ionophore concentration suggest that Pb2+ and Cd2+ are transported primarily as a 1:1 cation-ionophore complex, but that complexes with other stoichiometries may also be present. The ionophore transports Pb2+ and Cd2+ by a predominantly electrogenic mechanism, based upon an enhanced rate of transport that is produced by agents which dissipate transmembrane potentials. The rate of Pb2+ transport shows a biphasic pH dependence with the maximum occurring at pH approximately 6.5. The high selectivity for Pb2+ and Cd2+ displayed by the cyclohexanecarboxylic acid-capped 15-crown-5 ether suggests potential applications of this ionophore for the treatment of Pb and Cd intoxication, and removal of these heavy metals from wastewater. PMID:16488017

  5. Noise properties of Pb/Cd-free thick film resistors

    NASA Astrophysics Data System (ADS)

    Witold Stadler, Adam; Kolek, Andrzej; Zawiślak, Zbigniew; Mleczko, Krzysztof; Jakubowska, Małgorzata; Rafał Kiełbasiński, Konrad; Młożniak, Anna

    2010-07-01

    Low-frequency noise spectroscopy has been used to examine noise properties of Pb/Cd-free RuO2- and CaRuO3-based thick films screen printed on alumina substrates. Experiments were performed in the temperature range 77-300 K and the frequency range 0.5-5000 Hz with multiterminal devices. The measured noise has been recognized as resistance noise that consists of background 1/f noise and components generated by several thermally activated noise sources (TANSs) of different activation energies. The total noise has been composed of the contributions generated in the resistive layer and in the resistive/conductive layers interface. These noise sources are non-uniformly distributed in the resistor volume. Noise intensity of new-resistive layers has been described by the noise parameter Cbulk. Pb/Cd-free layers turned out to be noisier than their Pb-containing counterparts; however, the removal of Pb and Cd from resistive composition is hardly responsible for the increase in the noise. In the case of RuO2 layers noise increases most likely due to larger grain size of RuO2 powder used to prepare resistive pastes. Information on the quality of the resistive-to-conductive layers interface occurred to be stored in the values of noise parameter Cint. Pb/Cd-free RuO2-based resistive pastes form well-behaved interfaces with various Ag-based conductive pastes. In contrast, CaRuO3-based paste forms bad contacts with AgPd terminations because the density of TANSs increases in the interface area.

  6. Effect of the interface on UV-vis-IR photodetection performance of PbS/ZnO nanocomposite photocatalysts

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Li, Yuanzhi; Yang, Yi; Bai, Jilin; Zhao, Xiujian

    2015-12-01

    Two PbS/ZnO nanocomposites with the same Pb/Zn molar ratio of 1:12 and different PbS/ZnO interface were prepared by depositing PbS nanocrystals on nano ZnO with the reaction between Pb(NO3)2 and Na2S through changing the sequence of adding Pb(NO3)2 and Na2S to the nano ZnO suspension: (A) first adding Pb(NO3)2 followed by adding Na2S (denoted PbS/ZnO-A); (B) first adding Na2S followed by adding Pb(NO3)2 (denoted PbS/ZnO-B). The PbS/ZnO nanocomposites are characterized by XRD, BET, Raman, TEM, XPS, and UV-vis-IR. The characterizations indicate that PbS/ZnO-A has an interface of PbS nanocrystal closely contacted to ZnO nanocrystal while PbS/ZnO-B has an interface of a disordered layer between PbS nanocrystal and ZnO nanocrystal. It is found for the first time that the PbS/ZnO interface plays an important role in their photodetection performance. PbS/ZnO-A exhibits much higher photoresponse current and lower rise and recovery time than both PbS/ZnO-B and a mixture of nano PbS and ZnO with the same Pb/Zn molar ratio as PbS/ZnO-A for visible and near-infrared photodetection. PL and the impedance measurement in dark and irradiation reveal that the superior photodetection performance of PbS/ZnO-A over PbS/ZnO-B is attributed to its lower e-h recombination and migration resistance under the irradiation of visible and infrared light due to its very good PbS/ZnO interface of PbS nanocrystals closely attached ZnO nanocrystals, through which photogenerated electrons inject efficiently from the conduction band of PbS to that of ZnO. In contrast, the defect sites in the disordered layer between PbS nanocrystal and ZnO nanocrystal for PbS/ZnO-B act as e-h recombination centers, significantly decreasing the e-h separation efficiency.

  7. Enriching rice with Zn and Fe while minimizing Cd risk

    PubMed Central

    Slamet-Loedin, Inez H.; Johnson-Beebout, Sarah E.; Impa, Somayanda; Tsakirpaloglou, Nikolaos

    2015-01-01

    Enriching iron (Fe) and zinc (Zn) content in rice grains, while minimizing cadmium (Cd) levels, is important for human health and nutrition. Natural genetic variation in rice grain Zn enables Zn-biofortification through conventional breeding, but limited natural Fe variation has led to a need for genetic modification approaches, including over-expressing genes responsible for Fe storage, chelators, and transporters. Generally, Cd uptake and allocation is associated with divalent metal cations (including Fe and Zn) transporters, but the details of this process are still unknown in rice. In addition to genetic variation, metal uptake is sometimes limited by its bioavailability in the soil. The availability of Fe, Zn, and Cd for plant uptake varies widely depending on soil redox potential. The typical practice of flooding rice increases Fe while decreasing Zn and Cd availability. On the other hand, moderate soil drying improves Zn uptake but also increases Cd and decreases Fe uptake. Use of Zn- or Fe-containing fertilizers complements breeding efforts by providing sufficient metals for plant uptake. In addition, the timing of nitrogen fertilization has also been shown to affect metal accumulation in grains. The purpose of this mini-review is to identify knowledge gaps and prioritize strategies for improving the nutritional value and safety of rice. PMID:25814994

  8. Enriching rice with Zn and Fe while minimizing Cd risk.

    PubMed

    Slamet-Loedin, Inez H; Johnson-Beebout, Sarah E; Impa, Somayanda; Tsakirpaloglou, Nikolaos

    2015-01-01

    Enriching iron (Fe) and zinc (Zn) content in rice grains, while minimizing cadmium (Cd) levels, is important for human health and nutrition. Natural genetic variation in rice grain Zn enables Zn-biofortification through conventional breeding, but limited natural Fe variation has led to a need for genetic modification approaches, including over-expressing genes responsible for Fe storage, chelators, and transporters. Generally, Cd uptake and allocation is associated with divalent metal cations (including Fe and Zn) transporters, but the details of this process are still unknown in rice. In addition to genetic variation, metal uptake is sometimes limited by its bioavailability in the soil. The availability of Fe, Zn, and Cd for plant uptake varies widely depending on soil redox potential. The typical practice of flooding rice increases Fe while decreasing Zn and Cd availability. On the other hand, moderate soil drying improves Zn uptake but also increases Cd and decreases Fe uptake. Use of Zn- or Fe-containing fertilizers complements breeding efforts by providing sufficient metals for plant uptake. In addition, the timing of nitrogen fertilization has also been shown to affect metal accumulation in grains. The purpose of this mini-review is to identify knowledge gaps and prioritize strategies for improving the nutritional value and safety of rice. PMID:25814994

  9. Exploration of Zn resonance levels and thermoelectric properties in I-doped PbTe with ZnTe nanostructures.

    PubMed

    Rawat, P K; Paul, B; Banerji, P

    2014-03-26

    Motivated by the theoretically predicted Zn resonant states in the conduction band of PbTe, in the present work, we investigated the effect of Zn substitution on the thermoelectric properties in I-doped n-type PbTe. The room temperature thermopower values show good agreement with the theoretical Pisarenko plot of PbTe up to a carrier concentration of 4.17 × 10(19) cm(-3); thus, the presence of Zn resonance levels is not observed. Because of the low solubility of Zn in PbTe, a second phase of coherent ZnTe nanostructures is observed within the PbTe host matrix, which is found to reduce the lattice thermal conductivity. The reduced lattice thermal conductivity in PbTe by ZnTe nanostructures leads to notable enhancement in the figure of merit with a maximum value of 1.35 at 650 K. In contrast to the recent literature, the carrier mobility is not found to be affected by the band offset between ZnTe nanostructures and PbTe. This is explained by the quantum tunneling of the charge carrier through the narrow offset barrier and depletion width and coherent nature of the interface boundary between the two phases, i.e., ZnTe and PbTe. PMID:24575978

  10. Interaction of Cu(2+), Pb (2+), Zn (2+) with trypsin: what is the key factor of their toxicity?

    PubMed

    Zhang, Tong; Zhang, Hao; Liu, Guiliang; Gao, Canzhu; Liu, Rutao

    2014-11-01

    Heavy metals possess great endangerment to environment even human health because of their indissolubility and bioaccumulation. The toxicity of heavy metal ions (Cu(2+), Pb(2+), Zn(2+)) to trypsin was investigated by fluorescence, synchronous fluorescence, UV-vis absorption, circular dichroism (CD) spectroscopy, isothermal titration calorimetry (ITC), and enzyme activity assay. The experimental results showed that toxic effect of heavy metal ions was due to their own characteristic, rather than the electric charges of the ion. Zn(2+) could not show the obvious toxicity to trypsin, while the structure and function of trypsin was damaged when the enzyme explored to Cu(2+) and Pb(2+). From the spectra results, we found that Cu(2+) would bind with trypsin, which lead to the fluorescence quenched and hydrophobicity increased. Pb(2+) could also change the structure and reduce the activity of trypsin in high concentration. In vitro measurement, the toxicity order of heavy metal ions to trypsin is: Cu(2+) > Pb(2+) > Zn(2+). In addition, isothermal titration calorimetry analysis proved that the interactions between Cu(2+), Pb(2+), Zn(2+) and trypsin were all spontaneous and exothermic, which indicated the adverse effect of these heavy metal ions to trypsin. PMID:25323557

  11. Characterization of pbt genes conferring increased Pb2+ and Cd2+ tolerance upon Achromobacter xylosoxidans A8.

    PubMed

    Hložková, Kateřina; Suman, Jáchym; Strnad, Hynek; Ruml, Tomas; Paces, Vaclav; Kotrba, Pavel

    2013-12-01

    The cluster of pbtTFYRABC genes is carried by plasmid pA81. Its elimination from Achromobacter xylosoxidans A8 resulted in increased sensitivity towards Pb(2+) and Cd(2+). Predicted pbtTRABC products share strong similarities with Pb(2+) uptake transporter PbrT, transcriptional regulator PbrR, metal efflux P1-ATPases PbrA and CadA, undecaprenyl pyrophosphatase PbrB and its signal peptidase PbrC from Cupriavidus metallidurans CH34. Expression of pbtABC or pbtA in a metal-sensitive Escherichia coli GG48 rendered the strain Pb(2+)-, Cd(2+)- and Zn(2+)-tolerant and caused decreased accumulation of the metal ions. Accumulation of Pb(2+), but not of Cd(2+) or Zn(2+), was promoted in E. coli expressing pbtT. Additional genes of the pbt cluster are pbtF and pbtY, which encode the cation diffusion facilitator (CDF)-like transporter and a putative fatty acid hydroxylase of unknown function, respectively. Expression of pbtF did not confer increased metal tolerance upon E. coli GG48, although the protein showed measurable Pb(2+)-efflux activity. Unlike the pbtT promoter, promoters of pbtABC, pbtF and pbtY contain features characteristic of promoters controlled by metal-responsive transcriptional regulators of the MerR family. Upregulation of pbtABC, pbtF and pbtY upon Pb(2+), Cd(2+) and Zn(2+) exposure was confirmed in wild-type Achromobacter xylosoxidans A8. Gel shift assays proved binding of purified PbtR to the respective promoters. PMID:24125695

  12. Analysis of Etched CdZnTe Substrates

    NASA Astrophysics Data System (ADS)

    Benson, J. D.; Bubulac, L. O.; Jaime-Vasquez, M.; Lennon, C. M.; Arias, J. M.; Smith, P. J.; Jacobs, R. N.; Markunas, J. K.; Almeida, L. A.; Stoltz, A.; Wijewarnasuriya, P. S.; Peterson, J.; Reddy, M.; Jones, K.; Johnson, S. M.; Lofgreen, D. D.

    2016-06-01

    State-of-the-art as-received (112)B CdZnTe substrates have been examined for surface impurity contamination and polishing residue. Two 4 cm × 4 cm and one 6 cm × 6 cm (112)B state-of-the-art as-received CdZnTe wafers were analyzed. A maximum surface impurity concentration of Al = 1.7 × 1015 atoms cm-2, Si = 3.7 × 1013 atoms cm-2, Cl = 3.12 × 1015 atoms cm-2, S = 1.7 × 1014 atoms cm-2, P = 1.1 × 1014 atoms cm-2, Fe = 1.0 × 1013 atoms cm-2, Br = 1.2 × 1014 atoms cm-2, and Cu = 4 × 1012 atoms cm-2 was observed on the as-received CdZnTe wafers. CdZnTe particulates and residual SiO2 polishing grit were observed on the surface of the as-received (112)B CdZnTe substrates. The polishing grit/CdZnTe particulate density on CdZnTe wafers was observed to vary across a 6 cm × 6 cm wafer from ˜4 × 107 cm-2 to 2.5 × 108 cm-2. The surface impurity and damage layer of the (112)B CdZnTe wafers dictate that a molecular beam epitaxy (MBE) preparation etch is required. The contamination for one 4 cm × 4 cm and one 6 cm × 6 cm CdZnTe wafer after a standard MBE Br:methanol preparation etch procedure was also analyzed. A maximum surface impurity concentration of Al = 2.4 × 1015 atoms cm-2, Si = 4.0 × 1013 atoms cm-2, Cl = 7.5 × 1013 atoms cm-2, S = 4.4 × 1013 atoms cm-2, P = 9.8 × 1013 atoms cm-2, Fe = 1.0 × 1013 atoms cm-2, Br = 2.9 × 1014 atoms cm-2, and Cu = 5.2 × 1012 atoms cm-2 was observed on the MBE preparation-etched CdZnTe wafers. The MBE preparation-etched surface contamination consists of Cd(Zn)Te particles/flakes. No residual SiO2 polishing grit was observed on the (112)B surface.

  13. Analysis of Etched CdZnTe Substrates

    NASA Astrophysics Data System (ADS)

    Benson, J. D.; Bubulac, L. O.; Jaime-Vasquez, M.; Lennon, C. M.; Arias, J. M.; Smith, P. J.; Jacobs, R. N.; Markunas, J. K.; Almeida, L. A.; Stoltz, A.; Wijewarnasuriya, P. S.; Peterson, J.; Reddy, M.; Jones, K.; Johnson, S. M.; Lofgreen, D. D.

    2016-09-01

    State-of-the-art as-received (112)B CdZnTe substrates have been examined for surface impurity contamination and polishing residue. Two 4 cm × 4 cm and one 6 cm × 6 cm (112)B state-of-the-art as-received CdZnTe wafers were analyzed. A maximum surface impurity concentration of Al = 1.7 × 1015 atoms cm-2, Si = 3.7 × 1013 atoms cm-2, Cl = 3.12 × 1015 atoms cm-2, S = 1.7 × 1014 atoms cm-2, P = 1.1 × 1014 atoms cm-2, Fe = 1.0 × 1013 atoms cm-2, Br = 1.2 × 1014 atoms cm-2, and Cu = 4 × 1012 atoms cm-2 was observed on the as-received CdZnTe wafers. CdZnTe particulates and residual SiO2 polishing grit were observed on the surface of the as-received (112)B CdZnTe substrates. The polishing grit/CdZnTe particulate density on CdZnTe wafers was observed to vary across a 6 cm × 6 cm wafer from ˜4 × 107 cm-2 to 2.5 × 108 cm-2. The surface impurity and damage layer of the (112)B CdZnTe wafers dictate that a molecular beam epitaxy (MBE) preparation etch is required. The contamination for one 4 cm × 4 cm and one 6 cm × 6 cm CdZnTe wafer after a standard MBE Br:methanol preparation etch procedure was also analyzed. A maximum surface impurity concentration of Al = 2.4 × 1015 atoms cm-2, Si = 4.0 × 1013 atoms cm-2, Cl = 7.5 × 1013 atoms cm-2, S = 4.4 × 1013 atoms cm-2, P = 9.8 × 1013 atoms cm-2, Fe = 1.0 × 1013 atoms cm-2, Br = 2.9 × 1014 atoms cm-2, and Cu = 5.2 × 1012 atoms cm-2 was observed on the MBE preparation-etched CdZnTe wafers. The MBE preparation-etched surface contamination consists of Cd(Zn)Te particles/flakes. No residual SiO2 polishing grit was observed on the (112)B surface.

  14. Biosorption of Cu(II), Zn(II), Cd(II) and Pb(II) by dead biomasses of green alga Ulva lactuca and the development of a sustainable matrix for adsorption implementation.

    PubMed

    Areco, María Mar; Hanela, Sergio; Duran, Jorge; Afonso, María dos Santos

    2012-04-30

    Many industries have high heavy metals concentrations in their effluents that should be treated before disposal in drains or natural watercourses. When adsorption process is evaluated to generate and implement an efficient, economical and sustainable method suitable for heavy metals removal from contaminated effluents, it is necessary to develop an experimental setup that contains the adsorbent. Ulva lactuca, a marine green alga, was studied as a natural biosorbent for heavy metals at acid pH conditions. Adsorption experiments were carried out in glass columns and in batch where the alga was suspended or fixed in an agar matrix. Langmuir and Freundlich models were applied to the experimental results. Langmuir model best describes the adsorption isotherms in all analyzed cases. The adsorption capacity increases with pH. Kinetic studies demonstrate that, in most studied cases, the adsorption follows a pseudo second order kinetics model. Removal efficiencies of the biomaterial supported in agar or fixed in columns were: fixed in columns>suspended in batch mode>fixed in agar. Finally, the effect of the presence of two sorbates, Cd and Pb, in the solution was measured and results demonstrate that adsorption of both metals are diminished by co/adsorption. PMID:22342902

  15. Concentrations of Pb, Zn, and Cu in Taraxacum spp. in relation to urban pollution

    SciTech Connect

    Cook, C.M.; Lanaras, T.; Sgardelis, S.P.; Pantis, J.D. )

    1994-08-01

    The combustion of petroleum fuel and exhaust emissions are major sources of atmospheric pollution in cities which result in the deposition of toxic substances, particularly heavy metals, in the surface layers of soils. Lead in particular enters the environment from the use of tetraethyl lead as an antiknock agent for petrol engines constituting 21% of fine particles emitted from cars burning leaded petrol. Antiwear protectants incorporated in lubricants often contain Cd, Cr, Cu, Hg, Ni, Pb and/or Zn which are also released into the environment by inefficient engines and irresponsible dumping of engine oils. Zn from tyre wear and Cu from diesel engines also add considerably to the environmental metal burden. Lowering of the permitted lead content of petrol and the growing use of unleaded fuel are expected to lead to reductions in the environmental lead burden, however, until unleaded fuel becomes universally accepted lead contamination, particularly of roadside soils and vegetation is a major cause for concern. A direct relationship between car exhaust, the Pb content of needles of Abies alba and reduced growth has been observed and can extend hundreds of metres from major highways. Lead tolerance has been observed in higher plants growing mine waste soils and to a lesser extent on lead-contaminated roadside soils. Automobiles which are responsible for line sources of pollution emissions in rural and suburban areas have a more far-reaching impact on roadside vegetation, already under considerable stress, in urban areas. Information on heavy metal effects on vegetation in urban environments however, are scarce. Modeling and multivariate analysis of a few of the factors involved have provided only limited data related to plant performance in these complex environments. Therefore in this study, the extent of heavy metal pollution by Pb, Zn, Cu and Cd in soils and in dandelion plants in the city of Thessaloniki has been examined. 20 refs., 2 figs., 3 tabs.

  16. A Research on CdZnTe Array Detector

    NASA Astrophysics Data System (ADS)

    Cai, M. S.; Guo, J. H.; Xie, M. G.; Zheng, C. X.

    2013-09-01

    The CdZnTe array detector is a new type of semiconductor detector, and it has been developing rapidly in recent years. It has some characteristics of high spatial resolution, high energy resolution, and it can work at room temperature. This article describes the physical characteristics and the working principle of the CdZnTe detector. It also introduces the production process of the CdZnTe array detector, including the pretreatment of the chips, passivation, ohmic electrode production, array template selection, and array package process selection (micro-interconnect). For evaluating the performance of the detector, the authors produced a 4 pixel × 4 pixel CdZnTe array and an 8 pixel × 8 pixel CdZnTe array (The thicknesses are 5 mm and 2 mm, respectively.The pixel size is 2 mm × 2 mm. The gaps are 0.15 mm and 0.2 mm, respectively.) with cooperation partner successfully. A multi-channel electronic readout system based on the ASIC (Application Specific Integrated Circuit) chip is used for the charge measurement of the 4 pixel × 4 pixel array of CdZnTe. The 16-pixel spectrum and the corresponding energy resolution are obtained with the ^{137}Cs radiation source. Among the results of each pixel, the best resolution is 4.8%@662 keV.

  17. CdZnTe technology for gamma ray detectors

    NASA Astrophysics Data System (ADS)

    Stahle, Carl; Shi, Jack; Shu, Peter; Barthelmy, Scott; Parsons, Ann; Snodgrass, Steve

    1998-01-01

    CdZnTe detector technology has been developed at NASA Goddard for imaging and spectroscopy applications in hard x-ray and gamma ray astronomy. A CdZnTe strip detector array with capabilities for arc second imaging and spectroscopy has been built as a prototype for a space flight gamma ray burst instrument. CdZnTe detectors also have applications for medical imaging, environmental protection, transportation safety, nuclear safeguards and safety, nuclear non-proliferation, and national security. This can be accomplished from space and also from portable detectors on earth. One of the great advantages of CdZnTe is that the detectors can be operated at room temperature which eliminates the need for cryogenic cooling. CdZnTe detectors have good energy resolution (3.6 keV at 60 keV) and excellent spatial resolution (<100 microns). NASA Goddard has developed the fabrication technology to make a variery of planar, strip, and pixel detectors and integrated these detectors to high density electronics. We have built a 2×2 and a large area (60 cm2, 36 detectors) 6×6 strip detector array. This paper will summarize the CdZnTe detector fabrication and packaging technology developed at Goddard.

  18. Lead zinc borate, PbZn2(BO3)2.

    PubMed

    Chen, Xue An; Zhao, Ying Hua; Chang, Xin An; Zhang, Li; Xue, Hai Ping

    2006-01-01

    PbZn2(BO3)2 crystallizes in the space group Pccn, with the Pb cation at a site with imposed twofold symmetry. The compound represents a new structure type in which ZnBO3 layers are bridged by Pb2+ cations, giving rise to a three-dimensional framework. Channels parallel to the [010] direction accommodate the stereochemically active lone pairs of the Pb2+ cations. PMID:16397327

  19. Optical and structural characterization of CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles.

    PubMed

    Murugadoss, G; Kumar, M Rajesh

    2014-09-01

    Core-shell CdS/ZnS (Zn 0.025-0.125 M) and CdS:Cu(2+) (1%)/ZnS nanoparticles were successfully synthesized using a chemical method. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR TEM), photoluminescence (PL) and UV/Visible (UV/Vis) techniques were used to characterize the novel CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles. All absorption peaks of the synthesized samples were highly blue-shifted from the bulk CdS and ZnS. Very narrow and symmetric PL emission was observed in the yellow region for core-shell CdS/ZnS. Furthermore, the PL emission of CdS/ZnS was tuned into orange region by incorporate the Cu ion into the core CdS lattice. PMID:24254232

  20. Synthesis, characterization and thermochemistry of synthetic Pb-As, Pb-Cu and Pb-Zn jarosites

    NASA Astrophysics Data System (ADS)

    Forray, Ferenc Lázár; Smith, A. M. L.; Navrotsky, A.; Wright, K.; Hudson-Edwards, K. A.; Dubbin, W. E.

    2014-02-01

    The enthalpy of formation from the elements of well characterized Pb-As, Pb-Cu, and Pb-Zn synthetic jarosites, corresponding to chemical formulas (H3O)0.68±0.03Pb0.32±0.002Fe2.86±0.14(SO4)1.69±0.08(AsO4)0.31±0.02(OH)5.59±0.28(H2O)0.41±0.02, (H3O)0.67±0.03Pb0.33±0.02Fe2.71±0.14Cu0.25±0.01(SO4)2±0.00(OH)5.96±0.30(H2O)0.04±0.002 and (H3O)0.57±0.03Pb0.43±0.02Fe2.70±0.14Zn0.21±0.01(SO4)2±0.00(OH)5.95±0.30(H2O)0.05±0.002, was measured by high temperature oxide melt solution calorimetry and gave ΔH°f = -3691.2 ± 8.6 kJ/mol, ΔH°f = -3653.6 ± 8.2 kJ/mol, and ΔH°f = -3669.4 ± 8.4 kJ/mol, respectively. Using estimated entropies, the standard Gibbs free energy of formation from elements at 298 K ΔG°f of the three compounds were calculated to be -3164.8 ± 9.1, -3131.4 ± 8.7, and -3153.6 ± 8.9 kJ/mol, respectively. Based on these free energies, their log Ksp values are -13.94 ± 1.89, -4.38 ± 1.81 and -3.75 ± 1.80, respectively. For this compounds, a log10{Pb2+}-pH diagram is presented. The diagram shows that the formation of Pb-As jarosite may decrease aqueous arsenic and lead concentrations to meet drinking water standards. The new thermodynamic data confirm that transformation of Pb-As jarosite to plumbojarosite is thermodynamically possible.

  1. ZnTe-CdS thin film photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Pfisterer, F.; Schock, H. W.

    1982-09-01

    ZnTe-CdS heterojunctions, developed for photovoltaic tandem systems, have been fabricated by evaporating ZnTe on polycrystalline CdS films. The CdS films are vacuum deposited onto glass substrates with silver metallization. The deposition of p-type ZnTe is performed by coevaporation of ZnTe and dopants (Cu, Ag, Te) from two individually controlled evaporation boats. The properties of the ZnTe films have been investigated by means of optical transmission, cathodoluminescence, and resistivity measurements. For the characterization of the heterojunction measurements of the I-V characteristics, the spectral response, the electron beam induced current (EBIC), and the photocapacitance have been carried out. The measurements indicate that the largest part of the photocurrent is generated in the CdS layer. The open circuit voltage ranges from 0.5 to 0.93 V with most of the cells near 0.75 V. Short circuit current densities of about 3 mA/cm 2 have been obtained. The I-V characteristics commonly show a "flat-spot" or "broken-knee" effect. The theoretical model assumes multistep tunnelling and recombination processes for carrier transport and, probably in grain boundaries, the formation of Cu 2S(low barrier, low open circuit voltage) and ZnCdTe (high barrier, high open circuit voltage) in some parts of the cells.

  2. Soil-plant abstract of heavy metals in Pb-Zn mining sites from Alcudia Valley (South Spain)

    NASA Astrophysics Data System (ADS)

    López-Berdonces, Miguel; Higueras, Pablo; Esbrí, Jose Maria; González-Corrochano, Beatríz; García-Noguero, Eva Mª; Martínez-Coronado, Alba; Fernandez-Calderón, Sergio; García-Noguero, Carolina

    2013-04-01

    Soil-plant transfer of heavy metals in Pb-Zn mining sites from Alcudia Valley (South Spain). Authors: Miguel A. López-Berdonces¹; Pablo Higueras¹; Jose María Esbrí¹; Beatriz González-Corrochano¹; Eva Mª García- Noguero¹; Alba Martínez Coronado¹; Sergio Fernández-Calderón¹; Carolina García-Noguero¹ ¹Instituto de Geología Aplicada, Universidad Castilla la Mancha, Pza. Manuel Meca, 1. 13400 Almadén, Spain. Alcudia Valley is a vast territory recently declared Natural Park, located in South of Spain. It is an area rich in mineral deposits of Zn and Pb and mining exists since the first millennium BC., having its highest ore production between mid-nineteenth century and the middle of the twentieth. This area has been selected because has more than 120 abandoned mines without remediation actions, with dumps and tailings with high contents of zinc and lead sulfides, and Cu, Ag, Cd, As, Sb in minor concentrations. In this study we determinate the transfer rate of these metals from soils to plants represented by oak leaves (Quercus ilex), because this specie is common within the selected area. To evaluate the soil-plant transfer were studied the correlation of contents, total and extractable, in soil-leaves. Extractable fraction was done by for different methods in water, EPA 1312 sulfuric acid: nitric acid 60:40 v., Ammonium Acetate and EDTA. To establish the correlation between heavy metals from soils to plants is necessary to know the contents of these and bioavailable content in soil. Three areas (S. Quintín, Romanilla, Bombita) were selected, taking 24 samples of soils and leaves. Analyzed leaves by XRF showed that Mn, Pb, Zn and Mo in S.Quintin and Romanilla, Mn, Pb in Bombita, exceeded the toxicity threshold. The same samples analyzed by ICP show us the toxicity threshold is exceeded Pb, Zn and Hg in S.Quintin, and Pb in Romanilla. The heavy metal content in leaves compared between two techniques analytical gives an acceptable correlation Zn - Pb

  3. Effect of annealing temperature on the optical property of high Cd content CdZnO films

    NASA Astrophysics Data System (ADS)

    Liu, Teren; Wang, Dongbo; Guo, Fengyun; Jiao, Shujie; Wang, Jinzhong; Liu, Yuhang; Luan, Chunyang; Cao, Wenwu; Zhao, Liancheng

    2016-09-01

    CdZnO films with high Cd contents (59%) have been deposited on quartz substrate by radio-frequency (RF) magnetron sputtering. The as-deposited CdZnO films can hardly show detectable photoluminescence (PL). However, once subjected to suitable annealing temperature, the CdZnO films exhibit pronounced PL. Furthermore, when the annealing temperature at 300 °C and above, that the CdZnO are changed from the single phase of the rs structure to involving w, zb, and rs phases. Consequently, reliable formation and optical property improvement of the CdZnO layers are achieved through annealing temperature at 300 °C.

  4. Photorefractivity in a Titanium Doped ZnCdTe Crystal

    NASA Technical Reports Server (NTRS)

    Davis, M.; Collins, L.; Dyer, K.; Tong, J.; Ueda, A.; Chen, H.; Chen, K.-T.; Burger, A.; Pan, Z.; Morgan, S. H.

    1997-01-01

    Single crystals of Zn(.04)Cd(.96)Te was grown by horizontal physical vapor transport (PVT) method and doped by annealing with TiTe2 powder at 600 C for six days. Photorefractive two-beam coupling, along with photoluminescence and absorption spectroscopy, were used to characterize the ZnCdTe:Ti crystal. At 1.32 micrometers, the photorefractive gain has been measured as a function of the grating period. A gain of about 0.16/cm was obtained at an intensity of about 0.1 W/sq cm. The results of this titanium doped ZnCdTe crystal are compared to that of vanadium-doped CdTe crystals reported previously.

  5. Lack of Zn inhibition of Cd accumulation by rice (Oryza sativa L.) supports non-Zn transporter uptake of Cd

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice (Oryza sativa L.) grown on Cd contaminated soils has been linked to health problems in subsistence rice farmers in Japan and China. For other crops, normal geogenic Zn inhibits the increased uptake of Cd on contaminated soils. A study was conducted using a multi-chelator buffered nutrient sol...

  6. Optical phonons in PbTe/CdTe multilayer heterostructures

    SciTech Connect

    Novikova, N. N.; Yakovlev, V. A.; Kucherenko, I. V.; Karczewski, G.; Aleshchenko, Yu. A.; Muratov, A. V.; Zavaritskaya, T. N.; Melnik, N. N.

    2015-05-15

    The infrared reflection spectra of PbTe/CdTe multilayer nanostructures grown by molecular-beam epitaxy are measured in the frequency range of 20–5000 cm{sup −1} at room temperature. The thicknesses and high-frequency dielectric constants of the PbTe and CdTe layers and the frequencies of the transverse optical (TO) phonons in these structures are determined from dispersion analysis of the spectra. It is found that the samples under study are characterized by two TO phonon frequencies, equal to 28 and 47 cm{sup −1}. The first frequency is close to that of TO phonons in bulk PbTe, and the second is assigned to the optical mode in structurally distorted interface layers. The Raman-scattering spectra upon excitation with the radiation of an Ar{sup +} laser at 514.5 nm are measured at room and liquid-nitrogen temperatures. The weak line at 106 cm{sup −1} observed in these spectra is attributed to longitudinal optical phonons in the interface layers.

  7. Saturating refractive nonlinearities and optical bistability in ZnSe/CdZnSe MQWs at room temperature

    NASA Astrophysics Data System (ADS)

    Li, Hongyu; Shen, De Z.; Zhang, Jiying; Wang, Shumei; Yang, Baojun; Yu, Guangyou

    1998-08-01

    The excitonic nonlinear refractive index was calculated by using Kramers-Kronig relation and the saturating absorption of ZnSe/CdZnSe multiple quantum wells (MQWs) was studied under different pump intensities. The maximum nonlinear refractive index change is about -6.19 X 10-3. Excitonic optical bistability in ZnSe/CdZnSe MQWs is investigated at room temperature. The result indicates that the threshold and contrast ratio for the optical bistability in ZnSe/CdZnSe MQWs are about 210Kw/cm2 and 2:1, respectively. On the basis of the excitonic nonlinear theories and excitonic absorption spectra in the ZnSe/CdZnSe MQWs, we attribute the major nonlinear mechanism of the optical bistability in the ZnSe/CdZnSe MQWs to the phase space filling of excitonic states and excitonic band broadening due to exciton-exciton interactions.

  8. Geochemistry of the Patricia Zn-Pb-Ag Deposit (paguanta, NE Chile)

    NASA Astrophysics Data System (ADS)

    Chinchilla Benavides, D.; Merinero Palomares, R.; Piña García, R.; Ortega Menor, L.; Lunar Hernández, R.

    2013-12-01

    The Patricia Zn-Pb-Ag ore deposit is located within the Paguanta mining project, situated at the northern end of the Andean Oligocene Porphyry Copper Belt of Chile. The sulfide mineralization occurs as W-E oriented veins hosted in volcanic rocks, mainly andesite (pyroclastic, ash and lavas), of Upper Cretaceous to Middle Tertiary age. The ore mineralogy (obtained by EMPA analyses) comprises in order of abundance, pyrite, sphalerite (5.5 - 10.89 wt % Fe, 9.8-19 % molar FeS and 0.52 wt % Cd), galena, arsenopyrite, chalcopyrite and Ag-bearing sulfosalts. The veins show a zoned and banded internal structure with pyrite at the edges and sphalerite in the center. The Ag occurs mostly as Ag-Cu-Sb sulfosalts, in order of abundance: series freibergite - argentotennantite -polybasite and stephanite. Other minor Ag phases such as argentite, pyrargirite and diaphorite were also identified. These Ag phases are typically associated with the base-metal sulfides. Freibergite occurs filling voids within sphalerite, chalcopyrite and at the contact between sphalerite and galena. Polybasite, stephanite, pyrargirite and argentite are mostly in close association with freibergite. In the case of diaphorite, it commonly occurs filling voids between galena crystals or as inclusions within galena. Some minor Ag-bearing sulfosalts are also identified between pyrite crystals. The alteration minerals are dominated by chlorite, illite and kaolinite. The gangue minerals consist of quartz and carbonates identified by XRD as kutnahorite. We obtained linear correlation statistically significant only for Ag, As Au, Cd, Cu, Pb, Sb and Zn and therefore we generated an enhanced scatter plot matrix of these elements. Bulk rock analyses (ICP/MS and XRF) of drill cores show that Ag is strongly and positively correlated with Pb and As, moderately with Cd, Sb, Au and Zn and weakly with Cu, while Au is moderately and positively correlated with Ag, As, Cd, Sb and Zn and weakly with Cu and Pb. These results

  9. Tunable zinc interstitial related defects in ZnMgO and ZnCdO films

    SciTech Connect

    Li, Wanjun; Qin, Guoping; Fang, Liang E-mail: kchy@163.com; Ye, Lijuan; Wu, Fang; Ruan, Haibo; Zhang, Hong; Kong, Chunyang E-mail: kchy@163.com; Zhang, Ping

    2015-04-14

    We report tunable band gap of ZnO thin films grown on quartz substrates by radio frequency magnetron sputtering. The zinc interstitial (Zn{sub i}) defects in ZnO films were investigated by X-ray diffraction, Raman scattering, Auger spectra, first-principle calculations, and Hall measurement. Undoped ZnO film exhibits an anomalous Raman mode at 275 cm{sup −1}. We first report that 275 cm{sup −1} mode also can be observed in ZnO films alloyed with Mg and Cd, whose Raman intensities, interestingly, decrease and increase with increasing Mg and Cd alloying content, respectively. Combined with the previous investigations, it is deduced that 275 cm{sup −1} mode is attributed to Zn{sub i} related defects, which is demonstrated by our further experiment and theoretical calculation. Consequently, the concentration of Zn{sub i} related defects in ZnO can be tuned by alloying Mg and Cd impurity, which gives rise to different conductivity in ZnO films. These investigations help to further understand the controversial origin of the additional Raman mode at 275 cm{sup −1} and also the natural n-type conductivity in ZnO.

  10. A Study on the CdZnTe Array Detector

    NASA Astrophysics Data System (ADS)

    Cai, Ming-sheng; Guo, Jian-hua; Xie, Ming-gang; Zheng, Chun-xiao

    2014-04-01

    The CdZnTe array detector is a new type of semiconductor detector being rapidly developed in recent years. It possesses a high spatial resolution and a high energy resolution, and it can work at room temperatures. This paper describes the physical properties and working principle of the CdZnTe array detector, as well as the manufacturing technology, including the chip pretreatment, passivation, ohmic electrode preparation, array template selection, and array packaging technology (micro-interconnection). For evaluating the perfor-mance of the detector, the authors have developed successfully a 4 pixel×4 pixel CdZnTe array and an 8 pixel×8 pixel CdZnTe array (with the thicknesses of 5 mm and 2 mm, the pixel size of 2 mm×2 mm, and the gaps of 0.15 mm and 0.2 mm, respectively) in cooperation with the partner. A multi-channel electronic readout system based on the ASIC (Application Specific Integrated Circuit) chip is devel-oped independently for the charge measurement of the 4 pixel×4 pixel CdZnTe array. The energy spectra and corresponding energy resolutions of the 16 pixels are obtained with the 137Cs radiative source, among them the best resolution is 4.8%@662 kev.

  11. Characterization of CdZnTe co-doped with indium and lead

    NASA Astrophysics Data System (ADS)

    Zaman, Yasir; Jie, Wanqi; Wang, Tao; He, Yihui; Xu, Lingyan; Guo, Rongrong; Xu, Yadong; Zha, Gangqiang

    2015-01-01

    Indium and lead co-doped Cd0.9Zn0.1Te (CZT:(In,Pb)) were characterized by using I-V measurement, thermally stimulated current (TSC) spectroscopy and time-of-flight (TOF). The concentration of doping level of In and Pb was 10 ppm and 2 ppm, respectively. I-V curves showed that CZT:(In,Pb) possessed the resistivity as high as 1.8×1010 Ω cm, and the mobility (μ) of about 868 cm2/V s, which is considered acceptable for detector's fabrication. However, the carrier life time (τ) was only 9.44×10-7 s. Therefore, the μτ (mobility life time product) value was low. TSC results showed thirteen different trap levels, which were much more than that in Indium doped CZT crystal. Several special traps associated with lead were found, which might be the reason for the low carrier life time.

  12. [Stabilization Treatment of Pb and Zn in Contaminated Soils and Mechanism Studies].

    PubMed

    Xie, Wei-qiang; Li, Xiao-mingi; Chen, Can; Chen, Xun-feng; Zhong, Yu; Zhong, Zhen-yu; Wan, Yong; Wang, Yan

    2015-12-01

    In the present work, the combined application of potassium dihydrogen phosphate, quick lime and potassium chloride was used to immobilize the Pb and Zn in contaminated soils. The efficiency of the process was evaluated through leaching tests and Tessier sequential extraction procedure. The mechanism of stabilization was analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) to reveal the mechanism of stabilization. The results showed that the stabilizing efficiency of Pb contaminated soils was above 80% and the leaching concentrations of Pb, Zn were far below the threshold when the ratio of exogenous P and soil (mol · mol⁻¹) was 2:1-4: 1, the dosing ratio of CaO was 0.1%-0.5% ( mass fraction) and the dosage of potassium chloride was 0.02-0. 04 mol. Meanwhile, Pb and Zn in soil were transformed from the exchangeable fraction into residual fraction, which implied that the migration of Pb, Zn in soil could be confined by the stabilization treatment. XRD and SEM analysis revealed that Ca-P-Pb precipitation, lead orthophosphate [PbHP0₄, Pb₃ (PO₄)₂], pyromorphite (Pb-PO₄-Cl/OH) and mixed heavy metal deposits (Fe-PO₄- Ca-Pb-Zn-OH) could be formed after solidification/stabilization in which Pb and Zn could be wrapped up to form a solidified composition and to prevent leaching. PMID:27012000

  13. Kinetic Isotopic Fractionation of Cd and Zn During Condensation

    NASA Astrophysics Data System (ADS)

    Cloquet, C.; Carignan, J.; Libourel, G.

    2005-12-01

    The development of MC-ICPMS allowed to measure precisely isotopic compositions of transitional metals with a resolution generally better than +/- 0.15 per mil per atomic mass unit. The isotopic composition of such metals (Zn, Cd, Cu) varies in terrestrial and extra-terrestrial samples resulting most probably from phase transformations (solid-gas-solid) and/or biogenic fractionation. Up to now, very few experiments were conducted in order to document isotope fractionation during evaporation and condensation of metals. In this study, we report Cd and Zn elemental and isotopic variations measured in fly ashes collected from an urban waste combustor (UWC) equipped with various ash and flue gas filtration devices, including a heat transfer system. In the evacuation system, temperature drop from ca. 900 to 250 degree Celsius. This temperature range allows the evaporation and then condensation of Cd and Zn and probably fusion and oxido-reduction reactions. Indeed, the composition of combustion residues clearly indicates that most of the cadmium and part of the zinc were evacuated in the flue gases. Chemical analysis of the fly ashes collected along the thermal gradient suggest a massive condensation of semi-volatile elements such as Cd and Zn just above the heat transfer plate, which behave as a cold point in the evacuation system. As a first approximation, Cd and Zn contents are directly related to the amount metal condensates on more refractory particles. Leaching experiments on different fly ashes thermodynamic calculations confirmed the occurrence of soluble Cd and Zn salt condensates. The cadmium and Zn isotopic composition of bulk, leachate and residue samples provided variations as large as 1 per mil for delta 114Cd (114Cd/110Cd ratio) and up to 0.5 per mil for delta 66Zn (66Zn/64Zn ratio). Both Cd and Zn delta values are positively correlated to concentrations. According to the position of samples in the thermal gradient of the evacuation system, we suggest that

  14. Effect of Ground Rubber vs. ZnSO4 on Spinach Accumulation of Cd from Cd-Mineralized California Soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Certain soils derived from marine shale in Salinas Valley, CA, USA, contain significant levels of natural Cd but normal levels of Zn, all derived from the soil parent materials. Crops grown on these soils contain high levels of Cd, and because of the high Cd:Zn, this Cd is highly bioavailable and a...

  15. Mechanism for radiative recombination in ZnCdO alloys

    SciTech Connect

    Buyanova, I. A.; Bergman, J. P.; Pozina, G.; Chen, W. M.; Rawal, S.; Norton, D. P.; Pearton, S. J.; Osinsky, A.; Dong, J. W.

    2007-06-25

    Temperature dependent cw- and time-resolved photoluminescence combined with absorption measurements are employed to evaluate the origin of radiative recombination in ZnCdO alloys grown by molecular-beam epitaxy. The near-band-edge emission is attributed to recombination of excitons localized within band tail states likely caused by nonuniformity in Cd distribution. Energy transfer between the tail states is argued to occur via tunneling of localized excitons. The transfer is shown to be facilitated by increasing Cd content due to a reduction of the exciton binding energy and, therefore, an increase of the exciton Bohr radius in the alloys with a high Cd content.

  16. Photoluminescence study of the substitution of Cd by Zn during the growth by atomic layer epitaxy of alternate CdSe and ZnSe monolayers

    SciTech Connect

    Hernández-Calderón, I.; Salcedo-Reyes, J. C.

    2014-05-15

    We present a study of the substitution of Cd atoms by Zn atoms during the growth of alternate ZnSe and CdSe compound monolayers (ML) by atomic layer epitaxy (ALE) as a function of substrate temperature. Samples contained two quantum wells (QWs), each one made of alternate CdSe and ZnSe monolayers with total thickness of 12 ML but different growth parameters. The QWs were studied by low temperature photoluminescence (PL) spectroscopy. We show that the Cd content of underlying CdSe layers is affected by the exposure of the quantum well film to the Zn flux during the growth of ZnSe monolayers. The amount of Cd of the quantum well film decreases with higher exposures to the Zn flux. A brief discussion about the difficulties to grow the Zn{sub 0.5}Cd{sub 0.5}Se ordered alloy (CuAu-I type) by ALE is presented.

  17. A Quaternary ZnCdSeTe Nanotip Photodetector

    PubMed Central

    2009-01-01

    The authors report the growth of needle-like high density quaternary Zn0.87Cd0.13Se0.98Te0.02nanotips on oxidized Si(100) substrate. It was found that average length and average diameter of the nanotips were 1.3 μm and 91 nm, respectively. It was also found that the as-grown ZnCdSeTe nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. Furthermore, it was found that the operation speeds of the fabricated ZnCdSeTe nanotip photodetector were fast with turn-on and turn-off time constants both less than 2 s. PMID:20652144

  18. Heat-induced transformation of CdSe-CdS-ZnS core-multishell quantum dots by Zn diffusion into inner layers.

    PubMed

    Yalcin, Anil O; Goris, Bart; van Dijk-Moes, Relinde J A; Fan, Zhaochuan; Erdamar, Ahmet K; Tichelaar, Frans D; Vlugt, Thijs J H; Van Tendeloo, Gustaaf; Bals, Sara; Vanmaekelbergh, Daniël; Zandbergen, Henny W; van Huis, Marijn A

    2015-02-25

    In this work, we investigate the thermal evolution of CdSe-CdS-ZnS core-multishell quantum dots (QDs) in situ using transmission electron microscopy (TEM). Starting at a temperature of approximately 250 °C, Zn diffusion into inner layers takes place together with simultaneous evaporation of particularly Cd and S. As a result of this transformation, CdxZn1-xSe-CdyZn1-yS core-shell QDs are obtained. PMID:25431813

  19. CdS and CdS/CdSe sensitized ZnO nanorod array solar cells prepared by a solution ions exchange process

    SciTech Connect

    Chen, Ling; Gong, Haibo; Zheng, Xiaopeng; Zhu, Min; Zhang, Jun; Yang, Shikuan; Cao, Bingqiang

    2013-10-15

    Graphical abstract: - Highlights: • CdS and CdS/CdSe quantum dots are assembled on ZnO nanorods by ion exchange process. • The CdS/CdSe sensitization of ZnO effectively extends the absorption spectrum. • The performance of ZnO/CdS/CdSe cell is improved by extending absorption spectrum. - Abstract: In this paper, cadmium sulfide (CdS) and cadmium sulfide/cadmium selenide (CdS/CdSe) quantum dots (QDs) are assembled onto ZnO nanorod arrays by a solution ion exchange process for QD-sensitized solar cell application. The morphology, composition and absorption properties of different photoanodes were characterized with scanning electron microscope, transmission electron microscope, energy-dispersive X-ray spectrum and Raman spectrum in detail. It is shown that conformal and uniform CdS and CdS/CdSe shells can grow on ZnO nanorod cores. Quantum dot sensitized solar cells based on ZnO/CdS and ZnO/CdS/CdSe nanocable arrays were assembled with gold counter electrode and polysulfide electrolyte solution. The CdS/CdSe sensitization of ZnO can effectively extend the absorption spectrum up to 650 nm, which has a remarkable impact on the performance of a photovoltaic device by extending the absorption spectrum. Preliminary results show one fourth improvement in solar cell efficiency.

  20. Synthesis and spectroscopic investigations of Cu- and Pb-doped colloidal ZnS nanocrystals.

    PubMed

    Ehlert, Oliver; Osvet, Andres; Batentschuk, Miroslaw; Winnacker, Albrecht; Nann, Thomas

    2006-11-23

    A novel organometallic synthesis method for the preparation of colloidal ZnS nanoparticles is presented. This method enables the synthesis of undoped ZnS nanocrystals as well as doping with Cu, Pb, or both. The particles can be covered with an undoped layer of ZnS, forming core/shell-type particles with the ZnS:Pb, ZnS:Cu, or ZnS:Cu,Pb cores. The particles were characterized via TEM, XRD, dynamic light scattering, and optical spectroscopy. We investigated the extrinsic surface defects and their coverage with an additional ZnS layer in detail by temperature-dependent luminescence and luminescence lifetime spectroscopy. PMID:17107162

  1. Stable and Metastable Equilibria in the Pb-Cd System

    NASA Astrophysics Data System (ADS)

    Chuang, Ying-Yu; Paik, J.-S.; Zhang, C.; Perepezko, J. H.; Chang, Y. A.

    2013-07-01

    Thermodynamic and phase diagram data in the Pb-Cd system are reevaluated. A substitutional solution model is used for the liquid and fcc and hcp phases. The stable and metastable equilibria of this system are calculated using the thermodynamic equations derived from equilibrium data. Besides the well-established eutectic reaction at 521 K (248 °C), one stable monotectic reaction at 548 K (275 °C) is found due to the existence of a stable liquid miscibility gap. The stable monotectic reaction has been missed in all previous evaluations. Experimental verifications of the stable and metastable phase equilibria are provided using droplet samples and undercooled liquid alloys. A differential thermal analysis (DTA) method is applied to determine the phase reaction temperatures using both traditional heating and cooling processes and a specially designed cycling process. Additional microstructural evidence is used to elucidate the nature of the phase reactions. The refined thermodynamic descriptions are based upon both the thermochemical and phase diagram stable and metastable data. The agreement between the calculated and experimental data is good. All experimental stable and metastable results are well explained by the new Pb-Cd phase diagram calculations within the experimental accuracy limits. Combined experimental and thermodynamic modeling procedures developed for determining the stable and metastable phase equilibria yield a highly reliable overall phase diagram assessment and a quantitative basis for the interpretation of non-equilibrium solidification processing.

  2. Overcoming Zn segregation in CdZnTe with the temperature gradient annealing

    NASA Astrophysics Data System (ADS)

    Kim, K.; Bolotnikov, A. E.; Camarda, G. S.; Hossain, A.; James, R. B.

    2016-05-01

    The availability of large volume crystals with the same energy gap in melt-grown CdZnTe (CZT) is restricted due to the Zn segregation in CdTe hosts. We observed the migration of Zn in the solid phase along the positive temperature gradient direction both in situ and post-growth temperature gradient annealing (TGA) of CZT. Diffusivity of Zn obtained from the in situ TGA was approximately 10-5 cm2/s order and completely different mechanism with that of post-growth. The CZT ingots obtained through in situ TGA have uniform Zn and resistivity of 1010 Ω cm orders. The CZT detectors fabricated from in situ TGA applied ingots exhibit 10% of energy resolution for 59.5 keV peak of 241Am.

  3. Quantifying the signature of the industrial revolution from Pb and Cd isotopes in the Susquehanna Shale Hills Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Ma, L.; Herndon, E.; Jin, L.; Sanchez, D.; Brantley, S. L.

    2013-12-01

    Anthropogenic forcings have dominated metal cycling in many environments. During the period of the industrial revolution, mining and smelting of ores and combustion of fossil fuels released non-negligible amounts of potentially toxic metals such as Pb, Cd, Mn, and Zn into the environment. The extent and fate of these metal depositions in soils during that period however, have not been adequately evaluated. Here, we combine Pb isotopes with Cd isotopes to trace the sources of metal pollutants in a small temperate watershed (Shale Hills) in Pennsylvania. Previous work has shown that Mn additions to soils in central PA was caused by early iron production, as well as coal burning and steel making upwind. Comparison of the Pb and Cd concentrations in the bedrock and soils from this watershed show that Pb and Cd in soils at Shale Hills are best characterized by addition profiles, consistent with atmospheric additions. Three soil profiles at Shale Hills on the same hillslope have very similar anthropogenic Pb inventories. Pb isotope results further reveal that the extensive use of local coals during iron production in early 19th century in Pennsylvania is most likely the anthropogenic Pb source for the surface soils at Shale Hills. Pb concentrations and isotope ratios were used to calculate mass balance and diffusive transport models in soil profiles. The model results further reveal that during the 1850s to 1920s, coal burning in local iron blasting furnaces significantly increased the Pb deposition rates to 8-14 μg cm-2 yr-1, even more than modern Pb deposition rates derived from the use of leaded gasoline in the 1940s to 1980s. Furthermore, Cd has a low boiling point (~760 °C) and easily evaporates and condenses. The evaporation and condensation processes could generate systematic mass-dependent isotope fractionation between Cd in coal burning products and the naturally occurring Cd in the sulfide minerals of coals. This fractionation indicates that Cd isotopes can

  4. Sulfidation Roasting of Hemimorphite with Pyrite for the Enrichment of Zn and Pb

    NASA Astrophysics Data System (ADS)

    Min, Xiao-Bo; Xue, Ke; Ke, Yong; Zhou, Bo-Sheng; Li, Yang-Wen-Jun; Wang, Qing-Wei

    2016-06-01

    With the increasing consumption of zinc and the depletion of zinc sulfide ores, the exploitation of low-grade zinc oxide ores may be important for the sustainability of the zinc industry. Hemimorphite, a zinc hydroxyl silicate hydrate, is a significant source of Zn and Pb. It is difficult to obtain Zn and Pb from the hemimorphite using traditional technology. In this work, for the first time, sulfidation roasting of hemimorphite with pyrite was studied for the enrichment of Zn and Pb by a flotation process. Four stages of sulfidation roasting were determined based on x-ray diffraction and thermogravimetry analysis. Then, the effects of sulfidation temperature, pyrite dosage and reaction time on the sulfidation percentages were investigated at the laboratory scale. The experimental results showed that the sulfidation percentages of Pb and Zn were as high as 98.08% and 90.55% under optimum conditions, respectively. Finally, a flotation test was performed to enrich Zn and Pb in the sulfidation product. A flotation concentrate with 8.78% Zn and 9.25% Pb was obtained, and the recovery of Zn and Pb reached 56.14% and 75.94%, respectively.

  5. Synthesis of CdSe/ZnS and CdTe/ZnS Quantum Dots: Refined Digestive Ripening

    DOE PAGESBeta

    Cingarapu, Sreeram; Yang, Zhiqiang; Sorensen, Christopher M.; Klabunde, Kenneth J.

    2012-01-01

    We report synthesis of CdSe and CdTe quantum dots (QDs) from the bulk CdSe and CdTe material by evaporation/co-condensation using the solvated metal atom dispersion (SMAD) technique and refined digestive ripening. The outcomes of this new process are (1) the reduction of digestive ripening time by employing ligands (trioctylphosphine oxide (TOPO) and oleylamine (OA)) as capping agent as well as digestive ripening solvent, (2) ability to tune the photoluminescence (PL) from 410 nm to 670 nm, (3) demonstrate the ability of SMAD synthesis technique for other semiconductors (CdTe), (4) direct comparison of CdSe QDs growth with CdTe QDs growth based on digestivemore » ripening times, and (5) enhanced PL quantum yield (QY) of CdSe QDs and CdTe QDs upon covering with a ZnS shell. Further, the merit of this synthesis is the use of bulk CdSe and CdTe as the starting materials, which avoids usage of toxic organometallic compounds, eliminates the hot injection procedure, and size selective precipitation processes. It also allows the possibility of scale up. These QDs were characterized by UV-vis, photoluminescence (PL), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and powder XRD.« less

  6. Heavy metals and health risk assessment of arable soils and food crops around Pb-Zn mining localities in Enyigba, southeastern Nigeria

    NASA Astrophysics Data System (ADS)

    Obiora, Smart C.; Chukwu, Anthony; Davies, Theophilus C.

    2016-04-01

    This study determined the heavy metals concentration in arable soils and associated food crops around the Pb-Zn mines in Enyigba, Nigeria, and metal transfer factors were calculated. Air-dried samples of the soils and food crops were analyzed for 8 known nutritional and toxic heavy metals by Inductively Coupled Plasma - Mass Spectrometer (ICP-MS) method. Eighty seven percent of all the 20 sampled soils contain Pb in excess of the maximum allowable concentration (MAC) set by Canadian Environmental Quality Guideline (CCME) and European Union (EU) Standard, while Zn in thirty-one percent of the samples exceeded the CCME for MAC of 200 mg/kg. All the food crops, with the exception of yam tuber, contain Pb which exceeded the 0.43 mg/kg and 0.3 mg/kg MAC standards of EU and WHO/FAO respectively, with the leafy vegetables accumulating more Pb than the tubers. The metal transfer factors in the tubers and the leafy vegetables were in the order: Mo > Cu > Zn > Mn > As > Cd > Cr > Ni > Pb and Cd > Cu > Zn > Mn > Mo > As > Ni > Pb > Cr, respectively. Risk assessment studies revealed no health risk in surrounding populations for most of the heavy metals. However, Pb had a high health risk index (HRI) of 1.1 and 1.3, in adults and children, respectively for cassava tuber; Pb had HRI > 1 in lemon grass while Mn also had HRI > 1 in all the leafy vegetables for both adult and children. This high level of HRI for Pb and Mn is an indication that consumers of the food crops contaminated by these metals are at risk of health problems such as Alzheimers' disease and Manganism, associated with excessive intake of these metals. Further systematic monitoring of heavy metal fluxes in cultivable soils around the area of these mines is recommended.

  7. Optical investigation of CdSe/ZnSe quantum nanostructures

    NASA Astrophysics Data System (ADS)

    Valakh, M. Ya; Ivanov, S. V.; Mestres, N.; Pascual, J.; Shubina, T. V.; Sorokin, S. V.; Streltchuk, V. V.; Pozina, G.; Monemar, B.

    2002-02-01

    We have used resonant and non-resonant Raman scattering as well as photoluminescence and cathodoluminescence experiments to study the structure and composition properties of CdxZn1-xSe formed by migration enhanced epitaxy of CdSe layers on ZnSe buffers. The spectral change of the photoluminescence maximum correlates with the increase of the Cd content, depending on the nominal CdSe thickness in the 1.5-3.0 ML range. The inhomogeneous broadening of the photoluminescence band is caused by the composition difference between the two-dimensional mixed CdxZn1-xSe layer and the inserted islands with larger Cd concentration. This is confirmed by phonon frequency changes in resonant Raman scattering for samples with different nominal CdSe thicknesses as well as in Stokes and anti-Stokes frequency changes observed in the 1.5 ML sample. Attention is paid to the role of defects on Raman scattering and photoluminescence for the 3.15 ML sample.

  8. On the interplay of point defects and Cd in non-polar ZnCdO films

    SciTech Connect

    Zubiaga, A.; Reurings, F.; Tuomisto, F.; Plazaola, F.; Kuznetsov, A. Yu.; Egger, W.; Zuniga-Perez, J.; Munoz-Sanjose, V.

    2013-01-14

    Non-polar ZnCdO films, grown over m- and r-sapphire with a Cd concentration ranging between 0.8% and 5%, have been studied by means of slow positron annihilation spectroscopy (PAS) combined with chemical depth profiling by secondary ion mass spectroscopy and Rutherford back-scattering. Vacancy clusters and Zn vacancies with concentrations up to 10{sup 17} cm{sup -3} and 10{sup 18} cm{sup -3}, respectively, have been measured inside the films. Secondary ion mass spectroscopy results show that most Cd stays inside the ZnCdO film but the diffused atoms can penetrate up to 1.3 {mu}m inside the ZnO buffer. PAS results give an insight to the structure of the meta-stable ZnCdO above the thermodynamical solubility limit of 2%. A correlation between the concentration of vacancy clusters and Cd has been measured. The concentration of Zn vacancies is one order of magnitude larger than in as-grown non-polar ZnO films and the vacancy cluster are, at least partly, created by the aggregation of smaller Zn vacancy related defects. The Zn vacancy related defects and the vacancy clusters accumulate around the Cd atoms as a way to release the strain induced by the substitutional Cd{sub Zn} in the ZnO crystal.

  9. Pb and Cd Contents in Soil, Water, and Trees at an Afforestation Site, South China.

    PubMed

    Pei, Nancai; Chen, Bufeng; Liu, Shuguang

    2015-11-01

    Pb and Cd contents in 13 plantation tree species (leaf and branch components), soil, water (groundwater and river water) at a young (3-5 year-old) seashore afforestation stand were investigated in Nansha district, Guangzhou city in southern China. The results showed that (1) soil, rather than water or trees, had the highest content of both Pb (averagely 48.79 mg/kg) and Cd (0.50 mg/kg), demonstrating that soil might function as a major reservoir for extraneously derived heavy metals; (2) Pb content was higher in branches than in leaves, but Cd content appeared similar in both components, implying possibly different accumulation mechanisms in trees; (3) Pb and Cd appeared to accumulate differently among some tree taxa, whereas almost no significant difference was detected between introduced and indigenous species. The study indicated that trees were potentially useful to remediate sites contaminated with Pb and Cd in the urbanized areas. PMID:26242803

  10. Photoluminescence properties of ZnS nanoparticles co-doped with Pb 2+ and Cu 2+

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Lü, Mengkai; Xü, Dong; Yuan, Duolong; Zhou, Guangjun

    2001-03-01

    Nanometer-scale ZnS, ZnS:Cu, ZnS:Pb, and ZnS co-doped with Cu 2+ and Pb 2+ have been synthesized using a chemical precipitation method. X-ray diffraction analysis shows that the diameter of the particles is 2-4 nm. These nanocrystals can be doped with copper and lead during the synthesis without altering the X-ray diffraction pattern. However, doping has shifted the luminescence to 530 nm (Cu 2+-doped) and 500-550 nm (co-doped with Cu 2+ and Pb 2+). In the case of ZnS:Pb nanocrystals, a relatively broad emission band (color range from blue to yellow) has been observed and its excitation wavelength shows a red shift. The photoluminescence intensity increases as the ZnS nanoparticles co-doped with Pb 2+ and Cu 2+. The results strongly suggest that doped ZnS nanocrystals, especially two kinds of metals activated ZnS nanocrystals, form a new class of luminescent materials.

  11. Distribution of Pb, Cd and Ba in soils and plants of two contaminated sites.

    PubMed

    Pichtel, J; Kuroiwa, K; Sawyerr, H T

    2000-10-01

    Evaluation of metal accumulation in soils and plants is of environmental importance due to their health effects on humans and other biota. Soil material and plant tissue were collected along transects in two heavily contaminated facilities, a Superfund site and a lead-acid battery dump, and analyzed for metal content. Soil lead (Pb), cadmium (Cd) and barium (Ba) concentrations for the Superfund site averaged 55,480, 8.5 and 132.3 mg/kg, respectively. Soil Pb occurred primarily in the carbonate, sulfide/residual and organic chemical fractions (41.6, 28.6 and 16.7%, respectively). Soil Pb, Cd and Ba concentrations for the dump site averaged 29,400, 3.9 and 1130 mg/kg, respectively. Soil Pb occurred mostly in the organic and carbonate fractions as 48.5 and 42.5%, respectively. Pb uptake in the two sites ranged from non-detectable (Agrostemma githago, Plantago rugelii, Alliaria officinalis shoots), to 1800 mg/kg (Agrostemma githago root). Cd uptake was maximal in Taraxacum officinale at 15.4 mg/kg (Superfund site). In the majority > or =65%) of the plants studied, root Pb and Cd content was higher than that for the shoots. Tissue Pb correlated slightly with exchangeable and soluble soil Pb; however, tissue Cd was poorly correlated with soil Cd species. None of the sampled plants accumulated measurable amounts of Ba. Those plants that removed most Pb and Cd were predominantly herbaceous species, some of which produce sufficient biomass to be practical for phytoremediation technologies. Growth chamber studies demonstrated the ability of T. officinale and Ambrosia artemisiifolia to successfully remove soil Pb and Cd during repeated croppings. Tissue Pb was correlated with exchangeable soil Pb at r(2)=0.68 in Ambrosia artemisiifolia. PMID:15092867

  12. CdZnSe/ZnSe strained layer superlattices disordered by germanium diffusion

    SciTech Connect

    Yokogawa, T.; Floyd, P.D.; Merz, J.L.

    1994-03-01

    We have investigated the phenomenon of layer disordering in CdZnSe/ZnSe strained layer superlattices (SLSs) by Ge diffusion and have fabricated CdZnSe/ZnSe optical waveguides using the Ge-induced disordering. Both the as-grown sample and the sample annealed without a Ge layer showed several orders of well-resolved double crystal x-ray satellite peaks due to SLS periodic structure. However, the satellite peaks completely disappeared in the Ge-diffused sample, indicating that the SLS structure was disordered by the Ge diffusion and not caused by the annealing process. Photoluminescence (PL) measurements at 1.4K of both the as-grown and the annealed samples without Ge diffusion show intense, sharp excitonic emission around 483 nm in CdZnSe/ZnSe SLS. After Ge diffusion, the PL peaks shift to higher energy confirming the layer disordering of the SLS. The blue shift due to disordering was also observed in the PL at room temperature (RT). The optical guided mode in the SLS guiding layer confined by the disordered alloy was confirmed. Lateral optical confinement in the stripe geometry laser was also confirmed by observing the RT stimulated emission produced by optical pumping. 12 refs., 6 figs.

  13. Critical elements in sediment-hosted deposits (clastic-dominated Zn-Pb-Ag, Mississippi Valley-type Zn-Pb, sedimentary rock-hosted Stratiform Cu, and carbonate-hosted Polymetallic Deposits): A review: Chapter 12

    USGS Publications Warehouse

    Marsh, Erin; Hitzman, Murray W.; Leach, David L.

    2016-01-01

    Some sediment-hosted base metal deposits, specifically the clastic-dominated (CD) Zn-Pb deposits, carbonate-hosted Mississippi Valley-type (MVT) deposits, sedimentary-rock hosted stratiform copper deposits, and carbonate-hosted polymetallic (“Kipushi type”) deposits, are or have been important sources of critical elements including Co, Ga, Ge, and Re. The generally poor data concerning trace element concentrations in these types of sediment-hosted ores suggest that there may be economically important concentrations of critical elements yet to be recognized.

  14. Cancer Cell Targeting Using Folic Acid/Anti-HER2 Antibody Conjugated Fluorescent CdSe/CdS/ZnS-MPA and CdTe-MSA Quantum Dots.

    PubMed

    Singh, Gurpal; Kumar, Manoj; Soni, Udit; Arora, Vikas; Bansal, Vivek; Gupta, Dikshi; Bhat, Madhusudan; Dinda, Amit K; Sapra, Sameer; Singh, Harpal

    2015-12-01

    CdSe/CdS/ZnS and CdTe quantum dots (QDs) were synthesized by successive ion layer adsorption and reaction (SILAR) technique and direct aqueous synthesis respectively using thiol stabilizers. Synthesized CdSe/CdS/ZnS and CdTe QDs stabilized with 3-mercaptopropionic acid (MPA) and mercaptosuccinic acid (MSA) were used as fluorescent labels after conjugation with folic acid (FA) and anti-HER2 antibodies. Photoluminescence quantum yield of folated CdSe/CdS/ZnS-MPA and CdTe-MSA QDs was 59% and 77% than that of non-folated hydrophilic QDs. The folate receptor-mediated delivery of folic acid-conjugated CdTe-MSA and CdSe/CdS/ZnS-MPA QDs showed higher cellular internalization as observed by confocal laser scanning microscopic studies. Folated and non-folated CdTe-MSA QDs were highly toxic and exhibited only 10% cell viability as compared to > 80% cell viability with CdSe/CdS/ZnS-MPA QDs over the concentration ranging from 3.38 to 50 pmoles. Immunohistochemistry (IHC) results of human breast cancer tissue samples showed positive results with anti-HER2 antibody conjugated CdSe/CdS/ZnS-MPA QDs with better sensitivity and specificity as compared to conventional IHC analysis using diaminobenzedene staining. PMID:26682358

  15. Accumulation of Zn, Cu and Cd by crabs and barnacles

    NASA Astrophysics Data System (ADS)

    Rainbow, P. S.

    1985-11-01

    The crab Carcinus maenas (L.) and the barnacle Elminius modestus Darwin were exposed to a range of dissolved concentrations of Zn, Cu and Cd for 21 days in artificial seawater. Accumulation of Zn and Cu by crabs has been interpreted in terms of the presence of a regulation mechanism to maintain constant body concentrations (83·2 ± 19·4 μg Zn g -1 dry wt.; 39·8 ± 9·8 μg Cu g -1 dry wt.) under varying external dissolved metal levels, until a threshold dissolved metal concentration ( c. 400 μg Zn l -1; c. 170 μg Cu l -1) beyond which net accumulation of metal begins. Cadium appears to be accumulated by C. maenas at all exposures with no evidence for regulation of body cadmium concentrations. Exposure of E. modestus to Zn, Cu or Cd caused net accumulation of the respective metal in the bodies of the barnacles, with no evidence for regulation of body metal concentrations.

  16. n-(CdMgTe/CdTe)/(p-(CdTe/ZnCdTe/ZnTe)/p-GaAs heterostructure diode for photosensor applications

    NASA Astrophysics Data System (ADS)

    Yahia, I. S.; AlFaify, S.; Abutalib, M. M.; Chusnutdinow, S.; Wojtowicz, T.; Karczewski, G.; Yakuphanoglu, F.; Al-Bassam, A.; El-Naggar, A. M.; El-Bashir, S. M.

    2016-05-01

    High quality n-(CdMgTe:I/n-CdTe:I)/(p-CdTe:N/p-ZnCdTe:N/p-ZnTe:N)/p-GaAs heterojunction diodes have been fabricated by molecular beam epitaxial growth. The illumination effect on the complex impedance and conductivity of heterostructure diode was investigated. The illumination intensities were taken up to the 200 mW/cm2 with frequency range of 42 Hz to 1 MHz. The observed real and imaginary parts of the complex impedance were strongly dependent on the illumination frequency. The inverse relation was observed between the illumination intensity and the complex impedance. The relaxation mechanism of the diode was analyzed by the Cole-Cole plots. The radius of the Cole-Cole curve decreases with increasing illumination intensity. This suggests a mechanism of illumination dependent on the relaxation process. It is also found that the conductivity increases linearly with increasing the illumination intensity. We can conclude that the new design heterostructure diode in our work is a good candidate in photodetector and optoelectronic applications.

  17. Genesis of the Bangbule Pb-Zn-Cu polymetallic deposit in Tibet, western China: Evidence from zircon U-Pb geochronology and S-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Kan, Tian; Zheng, Youye; Gao, Shunbao

    2016-04-01

    The Banbule Pb-Zn-Cu skarn deposit is located in the Longger-Gongbujiangda volcanic magma arc in the Gangdese-Nyainqentanglha Plate. It is the only lead-zinc polymetallic deposit discovered in the westernmost Nyainqentanglha metallogenic belt. The measured and indicated resources include 0.9 Mt of Pb+Zn (4.77% Pb and 4.74% Zn, respectively), 6499 t of Cu, and 178 t of Ag (18.75g/t Ag). The orebodies mainly occur as lenses, veins and irregular shapes in the contact zone between the quartz-porphyry and limestone of the Upper Permian Xiala Formation, or in the boundaries between limestone and sandstone. Pb-Zn-Cu mineralization in the Banbule deposit is closely associated with skarns. The ore minerals are dominated by galena, sphalerite, chalcopyrite, bornite, and magnetite, with subordinate pyrite, malachite, and azurite. The gangue minerals are mainly garnet, actinolite, diopside, quartz, and calcite. The ore-related quartz-porphyry displays LA-ICP-MS zircon U-Pb age of 77.31±0.74 Ma. The δ34S values of sulfides define a narrow range of -0.8 to 4.7‰ indicating a magmatic source for the ore-forming materials. Lead isotopic systematics yield 206Pb/204Pb of 18.698 to 18.752, 207Pb/204Pb of 15.696 to 15.760, and 208Pb/204Pb of 39.097 to 39.320. The data points are constrained around the growth curves of upper crust and orogenic belt according to the tectonic discrimination diagrams. The calculated Δβ ‑ Δγ values plot within the magmatic field according to the discrimination diagram of Zhu et al. (1995). The S-Pb isotopic data suggest that Bangbule is a typical skarn deposit, and the Pb-Zn-Cu mineralization is genetically related to the quartz-porphyry in the mining district. The discovery of the Bangbule deposit indicates that there is metallogenic potential in the westernmost Nyainqentanglha belt, which is of great importance for the exploration work in this area.

  18. CdZnTe arrays for nuclear medicine imaging

    SciTech Connect

    Barber, H.B.

    1996-12-31

    In nuclear medicine, a gamma-ray-emitting radiotracer is injected into the body, and the resulting biodistribution is imaged using a gamma camera. Current gamma cameras use a design developed by Anger. An Anger camera makes use of a slab of scintillation detector that is viewed by an array of photomultiplier tubes and uses an analog position estimation technique to determine the position of the gamma ray`s interaction. The image-forming optics is usually a multi-bore collimator made of lead. Such cameras are characterized by poor, system spatial resolution ({approximately}1 cm) due to poor detector resolution ({approximately}0.4 cm) and poor collimator performance. Arrays of semiconductor detectors are an attractive alternative to scintillators for use in gamma cameras. Semiconductor detectors have excellent energy resolution. High spatial resolution is also possible because large semiconductor detector arrays with small pixel sizes can be produced using photolithography techniques. A new crystal growth technique (high-pressure vertical Bridgman) allows production of detector grade CdTe and CdZnTe in multikilogram ingots. Although the cost of CdZnTe detectors has come down substantially in the last few years, in part because of economies of scale, costs are still more than an order of magnitude higher than those required for a commercial camera ($20--$50/gram). High detector costs are perhaps the major stumbling block to developing a semiconductor gamma camera. The photolithography techniques required to make large CdZnTe arrays have already been demonstrated. This paper discusses the recent developments made in CdZnTe detectors.

  19. The plumbide CeZnPb - Structure, magnetism, and chemical bonding

    NASA Astrophysics Data System (ADS)

    Hermes, Wilfried; Rodewald, Ute Ch.; Chevalier, Bernard; Matar, Samir F.; Eyert, Volker; Pöttgen, Rainer

    2010-05-01

    The plumbide CeZnPb was synthesized from the elements in a sealed tantalum ampoule. Its YPtAs-type structure was refined on the basis of single-crystal X-ray diffraction data: P6 3/ mmc, a = 463.7(2) and c = 1669.6(6) pm, w R2 = 0.1161, 189 F2 values, and 12 variables. CeZnPb crystallizes with a superstructure of AlB 2. The zinc and lead atoms form puckered [Zn 3Pb 3] hexagons, which are stacked in a sequence ABB' A'. The Zn-Pb distances within the layers are 278 pm. The shortest interlayer distance occurs between the zinc atoms of adjacent layers (305 pm). Susceptibility measurements of CeZnPb show Curie-Weiss behavior with an experimental magnetic moment of 2.47(1) μB/mol CeZnPb. CeZnPb shows two antiferromagnetic transitions at TN1 = 3.8 K and TN2 = 2.6 K. Magnetization measurements at 2 K show two metamagnetic transitions at critical fields of approximately 1.1 and 7.0 kOe, underlining the antiparallel spin alignment at zero field. The electronic and magnetic structure is discussed based on scalar relativistic computations using the augmented spherical wave (ASW) method within density functional theory (DFT). As a result, our calculations employing the generalized gradient approximation (GGA) reveal a delicate competition of ferro and antiferromagnetic interactions. Only after properly taking into account the electronic correlations present in CeZnPb via a GGA + U treatment we are able to correctly describe the antiferromagnetic ground state. In addition, our calculations give a clue to the metamagnetic transitions as being due to the inherent geometric frustration of the cerium spin system.

  20. High performance p-i-n CdTe and CdZnTe detectors

    NASA Astrophysics Data System (ADS)

    Khusainov, A. Kh; Dudin, A. L.; Ilves, A. G.; Morozov, V. F.; Pustovoit, A. K.; Arlt, R. D.

    1999-06-01

    A breakthrough in the performance of p-i-n CdTe and CdZnTe detectors is reported. The detector stability has been significantly improved, allowing their use in precise gamma and XRF applications. Detectors with energy resolution close to Si and Ge were produced operating with only -30--35°C cooling (by a Peltier cooler of 15×15×10 mm size and a consumed power less than 5 W). Presently detectors with volume of up to 300 mm 3 are available. In terms of photoelectric effect efficiency it corresponds to HPGe detectors with volumes of about 1.5 cm 3. The possibilities of further improvement of CdTe and CdZnTe detector characteristics are discussed in this paper.

  1. Increase of glutathione in mine population of Sedum alfredii: a Zn hyperaccumulator and Pb accumulator.

    PubMed

    Sun, Q; Ye, Z H; Wang, X R; Wong, M H

    2005-11-01

    Phytochelatins (PCs) have been induced in a large range of plant species, but their role in heavy metal tolerance is unclear. Sedum alfredii is a new zinc (Zn) hyperaccumulator and lead (Pb) accumulator found in an old Pb/Zn mine in the Zhejiang Province of China. Until now, the mechanisms of its hyperaccumulation/accumulation and tolerance were poorly understood. The aim of this work was to investigate whether PCs were differentially produced in mine populations of S. alfredii compared with a non-mine control of the same species. The results showed that plants from the mine site were more tolerant to increasing Zn and Pb concentrations than those from the control site. No PCs and cysteine (Cys) were detected by pre-column derivatization with HPLC fluorescence in any tissues of two populations at any treatment, which in turn indicated they were not responsible for Zn and Pb tolerance in the mine population. Instead, Zn and Pb treatments resulted in the increase of glutathione (GSH) for both populations in a tissue-dependent manner. Significant increases were observed in leaf, stem and root tissues of plants grown on the mine site. The results suggest that GSH, rather man PCs, may be involved in Zn and Pb transport, hyperaccumulation/accumulation and tolerance in mine population of S. alfredii. PMID:16225897

  2. Forest Gaps Inhibit Foliar Litter Pb and Cd Release in Winter and Inhibit Pb and Cd Accumulation in Growing Season in an Alpine Forest

    PubMed Central

    He, Jie; Yang, Wanqin; Li, Han; Xu, Liya; Ni, Xiangyin; Tan, Bo; Zhao, Yeyi; Wu, Fuzhong

    2015-01-01

    Aims The release of heavy metals (such as Pb and Cd) from foliar litter play an important role in element cycling in alpine forest ecosystems. Although natural forest gaps could play important roles in the release of heavy metals from foliar litter by affecting the snow cover during the winter and solar irradiation during the growing season, few studies have examined these potential roles. The objectives of this study were to document changes in Pb and Cd dynamics during litter decomposition in the center of gaps and under closed canopies and to investigate the factors that controlled these changes during the winter and growing seasons. Methods Senesced foliar litter from six dominant species, including Kangding willow (Salix paraplesia), Masters larch (Larix mastersiana), Mingjiang fir (Abies faxoniana), Alpine azalea (Rhododendron lapponicum), Red birch (Betula albosinensis) and Mourning cypress (Sabina saltuaria), was placed in litterbags and incubated between the gap center and closed canopy conditions in an alpine forest in the eastern region of the Tibetan Plateau. The litterbags were sampled at the snow formation stage, snow coverage stage, snow melt stage and during the growing season. The Pb and Cd concentrations in the sampled foliar litter were determined by acid digestion (HNO3/HClO4). Important findings Over one year of decomposition, Pb accumulation and Cd release from the foliar litter occurred, regardless of the foliar litter species. However, Pb and Cd were both released from the foliar litter during the winter and accumulated during the growing season. Compared with the gap center and the canopy gap edge, the extended gap edge and the closed canopy showed higher Pb and Cd release rates in winter and higher Pb and Cd accumulation rates during the growing season, respectively. Statistical analyses indicate that the dynamics of Pb were significantly influenced by frequent freeze–thaw cycles in winter and appropriate hydrothermal conditions during

  3. Translocation analysis and safety assessment in two water spinach cultivars with distinctive shoot Cd and Pb concentrations.

    PubMed

    Huang, Baifei; Xin, Junliang; Dai, Hongwen; Liu, Aiqun; Zhou, Wenjing; Liao, Kebing

    2014-10-01

    A pot experiment was conducted to investigate the translocation of cadmium (Cd) and lead (Pb) and assess the safety of edible parts in two cultivars of water spinach (Ipomoea aquatica Forsk.) contrasting in shoot Cd and Pb concentrations. A low-Cd-Pb cultivar (QLQ) and a high-Cd-Pb cultivar (T308) were grown in five soils with different concentrations of Cd and Pb. The results showed that QLQ had lower Cd and Pb concentrations in stems and leaves and higher root Cd concentration than T308 did. Root Pb concentration of T308 dramatically increased with increasing soil Pb concentration and was higher than that of QLQ in the highest Pb treatment. The root-to-stem Cd translocation ability in T308 was 2.3-3.0-fold higher than that in QLQ. Nevertheless, there was no significant difference in root-to-stem Pb translocation between QLQ and T308. The bioconcentration factors (BCFs) for Cd and Pb in the two cultivars remained stable in different Cd or Pb treatments, which were attributable to the homeostatic control mechanisms of Cd and Pb in water spinach. PMID:25028323

  4. Stable and luminescent wurtzite CdS, ZnS and CdS/ZnS core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Kumar, Hitanshu; Kumar, Manoj; Barman, P. B.; Singh, Ragini Raj

    2014-06-01

    This article presents first report on the highly stable and luminescent wurtzite CdS, ZnS and CdS/ZnS quantum dots (QDs) where the role of precursor selection at room temperature is the key. X-ray diffraction (XRD), optical absorbance spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy have been employed in order to characterize these QDs. XRD indicates the formation of wurtzite CdS, ZnS and CdS/ZnS system. Broadening in XRD peaks revealed the reduction in particle size such as 4.2, 5.2 and 5.8 nm for CdS, ZnS and CdS/ZnS, respectively, compared to their bulk counterparts. Blue shift in absorbance has been observed in each case as particles size decreases. The photoluminescence intensity emission of CdS/ZnS core/shell was strongly superior from that observed in individual CdS and ZnS nanoparticles. We also propose that the core and shell interface leads to favourable conditions that instigate photoluminescence emission in CdS/ZnS core/shell system. One notable result of this work obtained from the photoluminescence analysis is the significant reduction in full width at half maxima, in emission peak of core/shell structure which shows the enhanced monochromaticity. We have found that OH, CH2 and C-O functional groups are present on the QDs surface and that is why these QDs can be easily attachable to biomolecules. TEM analysis has been employed for confirmation of particle size and found to be 5.3, 5.8 and 6.2 nm for CdS, ZnS and CdS/ZnS structures, respectively.

  5. Point Defect Characterization in CdZnTe

    SciTech Connect

    Gul,R.; Li, Z.; Bolotnikov, A.; Keeter, K.; Rodriguez, R.; James, R.

    2009-03-24

    Measurements of the defect levels and performance testing of CdZnTe detectors were performed by means of Current Deep Level Transient Spectroscopy (I-DLTS), Transient Charge Technique (TCT), Current versus Voltage measurements (I-V), and gamma-ray spectroscopy. CdZnTe crystals were acquired from different commercial vendors and characterized for their point defects. I-DLTS studies included measurements of defect parameters such as energy levels in the band gap, carrier capture cross sections, and defect densities. The induced current due to laser-generated carriers was measured using TCT. The data were used to determine the transport properties of the detectors under study. A good correlation was found between the point defects in the detectors and their performance.

  6. Arabis gemmifera is a hyperaccumulator of Cd and Zn.

    PubMed

    Kubota, Hiroshi; Takenaka, Chisato

    2003-01-01

    Hyperaccumulators are essential for phytoremediation of heavy metals. In Europe and North America, many studies have been conducted to find more effective plants for phytoremediation of various pollutants. In Japan, this field of research has just recently come more into focus. A type of fern in Japan, Athyrium yokoscense, is well known as a hyperaccumulator of Cd and Zn. However, it is not suitable for phytoremediation because it is a summer green and grows slowly. Therefore, in order to find hyperaccumulators other than from A. yokoscense, we surveyed plants growing at polluted sites in Japan. We found that the Brassicae Arabis gemmifera is a hyperaccumulator of Cd and Zn, with phytoextraction capacities almost equal to Thlaspi caerulescens. PMID:14750427

  7. CdZnTe solid-state gamma cameras

    SciTech Connect

    Butler, J.F.; Lingren, C.L.; Friesenhahn, S.J.

    1998-06-01

    The authors report the development of a CdZnTe gamma ray imager whose advantages over the conventional Anger camera include (1) improved contrast resulting from superior energy resolution and unambiguous position determination and (2) the small size and weight and high reliability inherent in an all-solid-state construction. It provides high energy resolution and peak efficiency by incorporating Digirad`s new SpectrumPlus{trademark} detector technology. The new imager employs a modular design, in which each 1 inch x 1 inch module incorporates a monolithic 64-element CdZnTe detector array and ASIC-based circuitry that provides signal conditioning for every channel, identification of valid events and addressing functions. Imagers with a wide range of sizes and shapes can be assembled by tiling modules together on a specially designed signal routing board.

  8. Interplay Between Expression of Sulfur Assimilation Pathway Genes and Zn(2+) and Pb(2+) Stress in Acidithiobacillus ferrooxidans.

    PubMed

    Zheng, Chunli; Chen, Minjie; Wang, Dan; Zhang, Li; Wang, JianYing; Zhang, Xuefeng

    2016-10-01

    We have previously demonstrated that in Acidithiobacillus ferrooxidans, resistance to the highly toxic divalent cation Cd(2+) is mediated in part by the sulfur assimilation pathway (SAP) and enhanced intracellular concentrations of cysteine and glutathione(GSH) (Zheng et al., Extremophiles 19:429-436, 2015). In this paper, we investigate the interplay between Zn(2+) and Pb(2+) resistances, SAP gene expression, and thiol-containing metabolite levels. Cells grown in the presence of 300 mM Zn(2+) had enhanced activities of the following enzymes: adenosylphosphosulphate reductase (APR, 40-fold), serine acetyltransferase (SAT, 180-fold), and O-acetylserine (thiol) lyase (OAS-TL, 230-fold). We investigated the concentrations of mRNA transcripts of the genes encoding these enzymes in cells grown in the presence of 600 mM Zn(2+): transcripts for 4 SAP genes-ATPS(ATP sulphurylase), APR, SiR(sulfite reductase), SAT, and OAS-TL-each showed a more than three-fold increase in concentration. At the metabolite level, concentrations of intracellular cysteine and glutathione (GSH) were nearly doubled. When cells were grown in the presence of 10 mM Pb(2+), SAP gene transcript concentrations, cysteine, and GSH concentrations were all decreased, as were SAP enzyme activities. These results suggested that Zn(2+) induced SAP pathway gene transcription, while Pb(2+) inhibited SAP gene expression and enzyme activities compared to the pathway in most organisms. Because of the detoxification function of thiol pool, the results also suggested that the high resistance of A. ferrooxidans to Zn(2+) may also be due to regulation of GSH and the cysteine synthesis pathway. PMID:27376536

  9. Photoluminescence Spectroscopy of CdZnTe/CdTe Single Strained Quantum Wells

    NASA Astrophysics Data System (ADS)

    Reno, J. L.; Jones, E. D.

    1991-12-01

    We have grown strained Cd1-xZnxTe/CdTe single strained quantum wells by molecular beam epitaxy. The Zn concentration was varied from 10 to 60% and the well widths were systematically increased until the critical thickness was exceeded. Low-temperature (liquid helium) photoluminescence spectroscopy was used to characterize the films. The energy of the quantum well luminescence is consistent with a simple square well model when strain is included. The critical layer thickness for the CdTe quantum wells was found to be in agreement with the model of Matthews and Blakeslee.

  10. The long-term variation of Cd and Zn hyperaccumulation by Noccaea spp and Arabidopsis halleri plants in both pot and field conditions.

    PubMed

    Tlustoš, Pavel; Břendová, Kateřina; Száková, Jiřina; Najmanová, Jana; Koubová, Kateřina

    2016-01-01

    Three Cd and Zn hyperaccumulating plant species Noccaea caerulescens Noccaea praecox and Arabidopsis halleri (Brassicacceae) were cultivated in seven subsequent vegetation seasons in both pot and field conditions in soil highly contaminated with Cd, Pb, and Zn. The results confirmed the hyperaccumulation ability of both plant species, although A. halleri showed lower Cd uptake compared to N. caerulescens. Conversely, Pb phytoextraction was negligible for both species in this case. Because of the high variability in plant yield and element contents in the aboveground biomass of plants, great variation in Cd and Zn accumulation was observed during the experiment. The extraction ability in field conditions varied in the case of Cd from 0.2 to 2.9 kg ha(-1) (N. caerulescens) and up to 0.15 kg ha(-1) (A. halleri), and in the case of Zn from 0.2 to 6.4 kg ha(-1) (N. caerulescens) and up to 13.8 kg.ha(-1) (A. halleri). Taking into account the 20 cm root zone of the soil, the plants were able to extract up to 4.1% Cd and 0.2% Zn in one season. However, cropping measures should be optimized to improve and stabilize the long-term phytoextraction potential of these plants. PMID:26280307

  11. The Role of Crop Cd Bioavailability in Potential for Transfer of Soil Cd Risk to Humans and Wildlife

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cd is a common contaminant in soils affected by mining and smelting of Zn, Pb, Cu and Ag ores and where biosolids, composts and manures are applied. Zn is usually present at 100-200 times higher concentrations than Cd. Because of this relationship of Cd and Zn in ores and contaminated soils, Zn is...

  12. Growth of CdZnTe Crystals the Bridgman Technique with Controlled Overpressures of Cd

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hu; Lehoczky, S. L.

    2008-01-01

    Cd(1-x)Zn(x)Te crystals with x = 0.15 and 0.20, were grown in this study by closed-ampoule directional solidification (Bridgman) technique with a controlled Cd overpressure. The growth ampoule was made of quartz with inner diameter from 20 to 40 mm and a tapered length of 2.5 cm at the growth tip. Both unseeded and seeded growths were performed with total material charges up to 400 g. After the loading of starting CdZnTe material, a typical amount of 2 g of Cd was also loaded inside a Cd reservoir basket, which was attached beneath the seal-off cup. The ampoule was sealed off under a vacuum below lxl0(exp -5) Torr. The sealed ampoule was placed inside a 4-zone Bridgman furnace - a Cd reservoir zone with a heat-pipe furnace liner on the top, followed by a hot zone, a booster heating zone and a cold zone at the bottom. The Cd zone was typically 300 to 400 C below the hot zone setting. High resistivity material has been obtained without any intentional dopants but has been reproducibly obtained with In doping. The crystalline and the electrical properties of the crystals will be reported.

  13. Optical and Structural Properties of Zn-Cd-Mn-Se Double Quantum Well Systems

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takashi; Ohmori, Kenta; Kodama, Kazuki; Hishikawa, Masao; Fukasawa, Sakyo; Iwasaki, Fumiaki; Muranaka, Tsutomu; Nabetani, Yoichi

    2011-05-01

    Double quantum well (DQW) structures consisting of a ZnCdSe well and a ZnCdMnSe well separated by a ZnSe barrier are grown with molecular beam epitaxy (MBE). The DQW structures are characterized by using X-ray diffraction measurement and simulation. Thickness of each well layer is designed so that the lowest energy level of ZnCdMnSe well is close to the excited level of the ZnCdSe well. Optical properties of the DQWs are studied with photoluminescence (PL) and reflection spectra in external magnetic fields up to 8 T in the Faraday geometry. Exciton transfer from ZnCdMnSe well to ZnCdSe well is observed in magneto PL with energy selective photoexcitation. Exciton energies in ground and excited states are estimated from PL excitation spectra and reflection spectra.

  14. XAFS Determination of Pb and Cd Speciation with Siderophores and the Metal/Siderophore/Kaolinite System

    SciTech Connect

    Mishra, Bhoopesh; Haack, Elizabeth A.; Vasconcelos, Igor F.; Maurice, Patricia A.; Bunker, Bruce A.

    2008-06-16

    We provide evidence for hexadentate complexes of Pb{sup 2+} and Cd{sup 2+} with the trihydroxamate siderophore desferrioxamine B (DFO-B) at pH 7.5, and 9.0, respectively. Analysis of the species of Pb{sup 2+} and Cd{sup 2+} adsorbed at the surface of kaolinite clay under the same pH conditions and in the presence of DFO-B indicate that Pb{sup 2+} is sorbed as a metal-siderophore complex while Cd{sup 2+} is not.

  15. Growth and characterization of Cd1-xZnxTe/ZnO heterostructures from furnace-annealed CdTe/Zn multi-stacks

    NASA Astrophysics Data System (ADS)

    Chakraborty, Monisha; Bhattacharyya, Sugata

    2015-10-01

    Cd1-xZnxTe/ZnO hetero-structures were grown on glass substrates by furnace annealing of stack-deposited CdTe/Zn/CdTe/Zn thin film multi-layers in air. The multilayered structures were annealed in furnace at various temperatures in between 350 and 600 °C. XRD results revealed that while growth of Cd1-xZnxTe compound reached saturation by 500 °C, ZnO growth geared up in between 550 and 600 °C. The band-gap values of the composite structures were less than either standard Cd1-xZnxTe or ZnO. It was because of large presence of free Zn and Cd and staggered type-II band alignment. An exponential growth was observed for the Cd1-xZnxTe particle sizes against annealing temperature. Next SEM images showed reduced surface granularity with increasing Zn percentage in Cd1-xZnxTe. SEM micrographs further revealed growth of fiber like formations of ZnO on film surface with increasing annealing temperature. ImageJ software was further used to analyse the SEM micrographs and compositional characteristics from EDX results were co-related with structural, optical and morphological results.

  16. Divalent Cu, Cd, and Pb Biosorption in Mixed Solvents

    PubMed Central

    Al-Qunaibit, M. H.

    2009-01-01

    Dead dried Chlorella vulgaris was studied in terms of its performance in binding divalent copper, cadmium, and lead ions from their aqueous or 50% v/v methanol, ethanol, and acetone solutions. The percentage uptake of cadmium ions exhibited a general decrease with decrease in dielectric constant values, while that of copper and lead ions showed a general decrease with increase in donor numbers. Uptake percentage becomes less sensitive to solvent properties the larger the atomic radius of the biosorbed ion, and uptake of copper was the most affected. FT-IR analyses revealed stability of the biomass in mixed solvents and a shift in vibrations of amide(I) and (II), carboxylate, glucose ring, and metal oxygen upon metal binding in all media. ΔνCOO values (59–69 cm−1) confirmed bidentate metal coordination to carboxylate ligands. The value of νasCOO increased slightly upon Cu, Cd, and Pb biosorption from aqueous solutions indicating lowering of symmetry, while a general decrease was noticed in mixed solvents pointing to the opposite. M–O stretching frequencies increased unexpectedly with increase in atomic mass as a result of solvent effect on the nature of binding sites. Lowering polarity of the solvent permits variations in metal-alga bonds strengths; the smaller the metal ion, the more affected. PMID:19688108

  17. Origin of luminescence from ZnO/CdS core/shell nanowire arrays.

    PubMed

    Wang, Zhiqiang; Wang, Jian; Sham, Tsun-Kong; Yang, Shaoguang

    2014-08-21

    Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little. PMID:25008783

  18. Incorporation of V, Zn and Pb into the crystalline phases of Portland clinker

    SciTech Connect

    Andrade, F.R.D.; Maringolo, V.; Kihara, Y

    2003-01-01

    Burning of industrial wastes in cement kilns has an increasing environmental importance, brought about by the incorporation of potentially hazardous elements into clinker crystalline phases and partial substitution of primary fuel and raw materials. In this study, experimental clinkers were synthesized, with the addition of V, Zn and Pb to a standard raw meal, from which a control clinker was obtained for comparison. The three metals were chosen as they are present in the alternative fuel petcoke (V) and in industrial wastes (Zn, Pb) commonly burned in cement kilns. Electron microprobe and scanning electron microscope analysis revealed the preferential partition of these metals among the clinker crystalline phases. It was observed that V has shown a preferential partition towards C{sub 2}S. Zn appears in higher amounts in periclase, and C{sub 3}S has higher Zn contents than C{sub 2}S. Pb concentrates in minute spherules and partitions toward C{sub 3}S in small amounts.

  19. Effects of the Microbial Siderophore DFO-B on Pb and Cd Speciation in Aqueous Solution

    SciTech Connect

    Mishra, Bhoopesh; Haack, Elizabeth A.; Maurice, Patricia A.; Bunker, Bruce A.

    2009-04-08

    This study investigates the complexation environments of aqueous Pb and Cd in the presence of the trihydroxamate microbial siderophore, desferrioxamine-B (DFO-B) as a function of pH. Complexation of aqueous Pb and Cd with DFO-B was predicted using equilibrium speciation calculation. Synchrotron-based X-ray absorption fine structure (XAFS) spectroscopy at Pb L(III) edge and Cd K edge was used to characterize Pb and Cd-DFO-B complexes at pH values predicted to best represent each of the metal-siderophore complexes. Pb was not found to be complexed measurably by DFO-B at pH 3.0, but was complexed by all three hydroxamate groups to form a totally 'caged' hexadentate structure at pH 7.5-9.0. At the intermediate pH value (pH 4.8), a mixture of Pb-DFOB complexes involving binding of the metal through one and two hydroxamate groups was observed. Cd, on the other hand, remained as hydrated Cd{sup 2+} at pH 5.0, occurred as a mixture of Cd-DFOB and inorganic species at pH 8.0, and was bound by three hydroxamate groups from DFO-B at pH 9.0. Overall, the solution species observed with EXAFS were consistent with those predicted thermodynamically. However, Pb speciation at higher pH values differed from that predicted and suggests that published constants underestimate the binding constant for complexation of Pb with all three hydroxamate groups of the DFO-B ligand. This molecular-level understanding of metal-siderophore solution coordination provides physical evidence for complexes of Pb and Cd with DFO-B, and is an important first step toward understanding processes at the microbial- and/or mineral-water interface in the presence of siderophores.

  20. Cyclotron resonance excitation spectroscopy of CdTe and of CdTe/CdZnTe quantum wells

    NASA Astrophysics Data System (ADS)

    Lavigne, B.; Cox, R. T.

    1990-04-01

    Photoconductivity spectra for II-VI semiconductor samples were obtained without any need for electrical contacts by measuring the wavelength dependence of free-carrier cyclotron resonance at 35 GHz. For bulk CdTe, the surprisingly efficient creation of free electrons for h v below the bandgap energy is attributed to exciton-impurity interactions. Auger recombination and inelastic polariton-donor scattering are considered. Preliminary results for CdTe.CdZnTe quantum wells show sharp peaks corresponding to quantized states of free excitons in the well.

  1. CdCl{sub 2} treatment related diffusion phenomena in Cd{sub 1−x}Zn{sub x}S/CdTe solar cells

    SciTech Connect

    Kartopu, G. Clayton, A. J.; Barrioz, V.; Lamb, D. A.; Irvine, S. J. C.; Taylor, A. A.

    2014-03-14

    Utilisation of wide bandgap Cd{sub 1−x}Zn{sub x}S alloys as an alternative to the CdS window layer is an attractive route to enhance the performance of CdTe thin film solar cells. For successful implementation, however, it is vital to control the composition and properties of Cd{sub 1−x}Zn{sub x}S through device fabrication processes involving the relatively high-temperature CdTe deposition and CdCl{sub 2} activation steps. In this study, cross-sectional scanning transmission electron microscopy and depth profiling methods were employed to investigate chemical and structural changes in CdTe/Cd{sub 1−x}Zn{sub x}S/CdS superstrate device structures deposited on an ITO/boro-aluminosilicate substrate. Comparison of three devices in different states of completion—fully processed (CdCl{sub 2} activated), annealed only (without CdCl{sub 2} activation), and a control (without CdCl{sub 2} activation or anneal)—revealed cation diffusion phenomena within the window layer, their effects closely coupled to the CdCl{sub 2} treatment. As a result, the initial Cd{sub 1−x}Zn{sub x}S/CdS bilayer structure was observed to unify into a single Cd{sub 1−x}Zn{sub x}S layer with an increased Cd/Zn atomic ratio; these changes defining the properties and performance of the Cd{sub 1−x}Zn{sub x}S/CdTe device.

  2. IR spectroscopy of lattice vibrations and comparative analysis of the ZnTe/CdTe quantum-dot superlattices on the GaAs substrate and with the ZnTe and CdTe buffer layers

    SciTech Connect

    Kozyrev, S. P.

    2009-07-15

    A comparative analysis of multiperiod ZnTe/CdTe superlattices with the CdTe quantum dots grown by molecular beam epitaxy on the GaAs substrate with the ZnTe and CdTe buffer layers is carried out. The elastic-stress-induced shifts of eigenfrequencies of the modes of the CdTe- and ZnTe-like vibrations of materials forming similar superlattices but grown on different buffer ZnTe and CdTe layers are compared. The conditions of formation of quantum dots in the ZnTe/CdTe superlattices on the ZnTe and CdTe buffer layers differ radically.

  3. Variation of grain Cd and Zn concentrations of 110 hybrid rice cultivars grown in a low-Cd paddy soil.

    PubMed

    Shi, Jing; Li, Lianqing; Pan, Genxing

    2009-01-01

    Enhanced Cd uptake and Zn depletion in rice grains and high potential for food Cd exposure by the high-yielding hybrid cultivars of China had been addressed. A field experiment was conducted in 2006 to determine the difference in grain Cd and Zn between cultivars. Total 110 cultivars including super rice and common hybrid rice cultivars were grown on a single paddy soil (Entic Haplaquept) with a neutral reaction and low total Cd content. Grain Cd and Zn concentrations were determined with graphite atomic adsorption spectrophotometer (GFAAS) and flame atomic adsorption spectrophotometer (AAS) respectively. Wide variation of Cd content in grain was found in a range of 0.004-0.057 mg/kg, while the Zn content in a range of 10.25-30.06 mg/kg among the cultivars. Higher Cd but lower Zn concentration in grains of super rice cultivars was observed compared to the common hybrid ones. A highly significant positive linear correlation of grain Cd/Zn with grain Cd was found for super rice and common hybrid cultivars, meanwhile much higher slope for these hybrid cultivars than the reported non-hybrid cultivars was also observed. Using the limit value of the Chinese chemical guidelines for foods (MOHC and SSC, 2005), calculated potential risk of food Cd exposure with "Zn hungry" through diet intake was prominent with all the studied 110 hybrid rice cultivars, possessing high potential health problems for rice production in South China using the super rice cultivars. Breeding of genotypes of rice cultivars with low grain Cd and low Cd/Zn ratio is needed for rice production in acidic red soils where Cd bioavailability is prevalently high. PMID:19402417

  4. Pb isotopic constraints on the formation of the Dikulushi Cu-Pb-Zn-Ag mineralisation, Kundelungu Plateau (Democratic Republic of Congo)

    NASA Astrophysics Data System (ADS)

    Haest, Maarten; Schneider, Jens; Cloquet, Christophe; Latruwe, Kris; Vanhaecke, Frank; Muchez, Philippe

    2010-04-01

    Base metal-Ag mineralisation at Dikulushi and in other deposits on the Kundelungu Plateau (Democratic Republic of Congo) developed during two episodes. Subeconomic Cu-Pb-Zn-Fe polysulphide ores were generated during the Lufilian Orogeny (c. 520 Ma ago) in a set of E-W- and NE-SW-oriented faults. Their lead has a relatively unradiogenic and internally inhomogeneous isotopic composition (206Pb/204Pb = 18.07-18.49), most likely generated by mixing of Pb from isotopically heterogeneous clastic sources. These sulphides were remobilised and enriched after the Lufilian Orogeny, along reactivated and newly formed NE-SW-oriented faults into a chalcocite-dominated Cu-Ag mineralisation of high economic interest. The chalcocite samples contain only trace amounts of lead and show mostly radiogenic Pb isotope signatures that fall along a linear trend in the 207Pb/204Pb vs. 206Pb/204Pb diagram (206Pb/204Pb = 18.66-23.65; 207Pb/204Pb = 15.72-16.02). These anomalous characteristics reflect a two-stage evolution involving admixture of both radiogenic lead and uranium during a young fluid event possibly c. 100 Ma ago. The Pb isotope systematics of local host rocks to mineralisation also indicate some comparable young disturbance of their U-Th-Pb systems, related to the same event. They could have provided Pb with sufficiently radiogenic compositions that was added to less radiogenic Pb remobilised from precursor Cu-Pb-Zn-Fe polysulphides, whereas the U most likely originated from external sources. Local metal sources are also suggested by the 208Pb/204Pb-206Pb/204Pb systematics of combined ore and rock lead, which indicate a pronounced and diversified lithological control of the immediate host rocks on the chalcocite-dominated Cu-Ag ores. The Pb isotope systematics of polysulphide mineralisation on the Kundelungu Plateau clearly record a diachronous evolution.

  5. Geologic, geochemical, and isotopic studies of a carbonate- and siliciclastic-hosted Pb-Zn deposit at Lion Hill, Vermont

    USGS Publications Warehouse

    Foley, Nora K.; Clark, Sandra H.B.; Woodruff, Laurel G.; Mosier, Elwin L.

    1995-01-01

    The prospect of an Irish-type sedimentary-exhalative origin for stratabound Pb-Zn deposits of the Paleozoic shelf of North America is of considerable importance to understanding the timing of mineralization relative to platform evolution and for evaluating the mineral resource potential of the region. Our study of the Lion Hill deposit indicates a potential for Irish-type Pb-Zn deposits in platform rocks of western Vermont; however, at Lion Hill they contain enrichments of Pb, Zn, and Cu rather than a Pb, Zn, and Ag association.

  6. EMPIRICAL MODELS OF PB AND CD PARTITIONING USING DATA FROM 13 SOILS, SEDIMENTS AND AQUIFER MATERIALS

    EPA Science Inventory

    Lead (Pb) and cadmium (Cd) are two of the most common toxicants found in contaminated environments. Because solubilization of these metallic elements from the solid phase can influence their fate, transport and bioavailability, the partitioning coefficient (Kd) for these metals ...

  7. Zn, Cd, S and trace metal bioaccumulation in willow (Salix spp.) cultivars grown hydroponically.

    PubMed

    McBride, M B; Martinez, C E; Kim, B

    2016-12-01

    Willows (Salix spp.) can be used to phytoremediate soils contaminated by Zn and Cd under certain conditions. In this study, the ability of 14 Salix cultivars to concentrate Cd, Zn and S in leaves was measured in hydroponic culture with 10 and 200 µM Cd and Zn, respectively, in the nutrient medium. The cultivars showed a wide range of biomass yields, tolerance to metals, and foliar concentrations of Zn and Cd, with some cultivars accumulating up to 1000 mg kg(-1) Zn, 70 mg kg(-1) Cd and 10,000 mg kg(-1) S with only mild phytotoxicity symptoms attributable to excess Zn. Cultivars with higher foliar Zn concentrations tended to have higher foliar Cd concentrations as well, and competition between Zn and Cd for uptake was observed. Exposure of Salix cultivars to Cd and Zn did not affect foliar concentrations of secondary metabolites such as polyphenols, but trace metal concentrations in leaves were significantly reduced (Fe and Cu) or increased (Mn) by exposure to excess Zn and Cd. Sulfur-XANES spectroscopy showed foliar S to be predominantly in highly oxidized (sulfate plus sulfonate) and reduced (thiol) forms, with oxidized S more prevalent in willows with the highest total S content. PMID:27216699

  8. High resolution photoemission study of CdSe and CdSe/ZnS core-shell nanocrystals

    NASA Astrophysics Data System (ADS)

    Borchert, H.; Talapin, D. V.; McGinley, C.; Adam, S.; Lobo, A.; de Castro, A. R. B.; Möller, T.; Weller, H.

    2003-07-01

    Colloidally prepared CdSe and CdSe/ZnS core-shell nanocrystals passivated with trioctylphosphine/trioctylphosphine oxide and hexadecylamine have been studied by photoelectron spectroscopy with tuneable synchrotron radiation. High-resolution spectra of the Se 3d level in CdSe nanocrystals indicate the bonding of organic ligands not only to surface Cd but also to surface Se atoms. The investigation of the CdSe/ZnS core-shell nanocrystals allows us to determine the average thickness of the ZnS shell and to study the interface between the two semiconductor nanomaterials. The photoemission spectra indicate a rather well ordered interface. No evidence for interfacial bonds other than Cd-S and Se-Zn is found.

  9. Research on Root Responses to Pb and Zn Combined Stress of Carex putuoshan.

    PubMed

    Hu, Yong-Lin; Tan, Jia-Lang; Wang, Cheng-Long; Yang, Zhan-Biao; Yang, Yuan-Xiang; Chen, Zhang; Lin, Li-Jin; Wang, Ying-Jun; Sun, Gang; Zhu, Xue-Mei; Shao, Ji-Rong; Zhou, Mei-Liang

    2016-01-01

    Pb hyper-accumulated Carex putuoshan was taken as experimental material and subjected to combined stress of Pb and Zn. The differential expression of proteins in their roots were analyzed by Proteomic Approach. The protein that was directly involved in the cellular defense under the Pb and Zn combined stress was separated, and expression of those genes was analyzed with Carex Evergold as control. The results were obtained by MALDI-TOF/MS analysis. After applying Pb and Zn combined stress, the expression of 9 protein spots (including 7 different proteins, 2 identical proteins, 1 unknown protein) in Carex putuoshan root was found to be significantly up-regulated. Five proteins were obtained from the 9 proteins related to carbohydrate metabolism, including malate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, frutose-1,6-bisphosphate aldolase, enolase, and 6- phosphogluconate dehydrogenase. Two proteins were related to protein biosynthesis, including isoflavone reductase and phytochelatin synthase (PCS). From these proteins, the most important protein is PCS, which is a key enzyme in the synthesis of phytochelatins (PCs) and plays an important role in chelation. It is directly involved in cellular defense under Pb and Zn stress. After Pb and Zn combined stress, the CpPCS in Carex putuoshan was cloned. The full length of cDNA is 1461 bps, and it encodes 486 amino acids with molecular weight of 53.86 kD and pI value of 6.12. Two typical phytochelatin synthase subfamily domains constitute CpPCS protein, which includes three adjacent Cys-Cys elements in the C-terminal region. Phylogenetic analysis of PCS proteins from different species showed that it had the closest relationship with the Oryza sativa and Triticum aestivum. Real-time quantitative PCR analysis indicated that CpPCS and CePCS (Carex Evergold) genes were expressed in the root. The CpPCS and CePCS genes were up-regulated by Pb and Zn treatments. The expression of CpPCS was higher than that of Ce

  10. EDTA-Decorated Nanostructured ZnO/CdS Thin Films for Oxygen Gas Sensing Applications

    NASA Astrophysics Data System (ADS)

    Arunraja, L.; Thirumoorthy, P.; Karthik, A.; Rajendran, V.; Edwinpaul, L.

    2016-08-01

    ZnO/CdS and ZnO/CdS-EDTA nanostructured thin films were prepared on a glass substrate using spin-coating and used for oxygen gas sensor applications. The structural properties of both ZnO/CdS and ZnO/CdS-EDTA nanostructured composites were comparatively characterized. The nanostructure thin film was found in a hexagonal structure with an average crystallite size reduced from 77 nm to 29 nm due to the influence of the EDTA. The optical absorption, photo luminescence, functional groups and surface morphology of the nanostructured thin films were comprehensively investigated. Oxygen was suitably tailored to verify the sensor response over a concentration range of 10-50 ppm at room temperature. Thus, the sensor studies reveal that the performance, response, and recovery time were enhanced in ZnO/CdS-EDTA nanostructured thin film compared with ZnO/CdS.

  11. Bioaccessibility of As, Cd, Cu, Ni, Pb, and Sb in toys and low-cost jewelry.

    PubMed

    Guney, Mert; Zagury, Gerald J

    2014-01-21

    Children can be exposed to toxic elements in toys and jewelry following ingestion. As, Cd, Cu, Ni, Pb, and Sb bioavailability was assessed (n = 24) via the in vitro gastrointestinal protocol (IVG), the physiologically based extraction test (PBET), and the European Toy Safety Standard protocol (EN 71-3), and health risks were characterized. Cd, Cu, Ni, and Pb were mobilized from 19 metallic toys and jewelry (MJ) and one crayon set. Bioaccessible Cd, Ni, or Pb exceeded EU migratable concentration limits in four to six MJ, depending on the protocol. Using two-phase (gastric + intestinal) IVG or PBET might be preferable over EN 71-3 since they better represent gastrointestinal physiology. Bioaccessible and total metal concentrations were different and not always correlated, indicating that bioaccessibility measurement may provide more accurate risk characterization. More information on impacts of multiple factors affecting metals mobilization from toys and jewelry is needed before recommending specific tests. Hazard index (HI) for Cd, Ni, or Pb were >1 for all six MJ exceeding the EU limits. For infants (6-12 mo old), 10 MJ had HI > 1 for Cd, Cu, Ni, or Pb (up to 75 for Cd and 43 for Pb). Research on prolonged exposure to MJ and comprehensive risk characterization for toys and jewelry exposure is recommended. PMID:24345102

  12. Plasmon-Coupled CdSe/ZnS and CdTe/CdS/ZnS Coreshells for Hybrid Light Emitting Devices.

    PubMed

    Rice, Quinton; Hayes, Anderson; Jung, Sungsoo; Wang, Andrew; Cho, Hyoyoung; Kim, Wan-Joong; Abdel-Fattah, Mahmoud; Tabibi, Bagher; Seo, Jaetae

    2016-02-01

    Plasmon-coupled CdSe/ZnS and CdTe/CdS/ZnS coreshells are investigated for their optoelectronic applications because of their high color purity, wide optical tunability, large PL enhancement, and compact and easy integration into electronic devices. The quantum confinement of carriers within quantum dots (QDs) with sizes near the exciton Bohr radius (CdSe ~ 5.8 nm, CdTe ~ 7 nm) exhibits the features of discrete energy states and blue-shift from the bulk bandgap (CdSe ~718 nm, CdTe ~ 863 nm) in the optical spectrum. While the fluorescence from the QDs is attributable to the exciton carrier recombination, large PL enhancement and fast emission time is achieved through plasmon-exciton coupling via the Coulomb interaction. Large PL enhancement of QDs in the vicinity of plasmonic particles was observed and attributed to the reduction of the non-radiative decay rate and large local field enhancement. The large PL enhancement and wide optical tunability along with high color purity from plasmon-coupled QDs enables the realization of hybrid LEDs. PMID:27433706

  13. Control of Cd concentrations in a coastal diatom by interactions among free ionic Cd, Zn, and Mn in seawater

    SciTech Connect

    Sunda, W.G.; Huntsman, S.A.

    1998-10-01

    Cadmium and phosphate concentrations in seawater are closely correlated, suggesting that Cd distributions, like those of PO{sub 4}, are controlled by algal uptake and regeneration. But the factors controlling Cd levels in phytoplankton are poorly known. Experiments in metal ion buffer systems with a coastal diatom Thalassiosira pseudonana revealed that cellular Cd:C ratios within the Cd ion concentration ([Cd{sup 2+}]) range in seawater were generally proportional to [Cd{sup 2+}] and inversely related to concentrations of Zn and Mn ions ([Zn{sup 2+}] and [Mn{sup 2+}]) and specific growth rate. The effects of Mn and Zn reflect cellular uptake of Cd by two inducible transport systems: the Mn system whose capacity (V{sub max}) is enhanced at low [Mn{sup 2+}] and a separate system induced at low cellular zinc. At the low [Zn{sup 2+}] of surface oceanic waters ({le}10{sup {minus}11.0} M), Cd uptake is controlled by this latter system and, therefore, is inversely related to ionic zinc levels. However, at the higher [Zn{sup 2+}] range of coastal waters, Cd uptake by this system is strongly suppressed and Cd instead is taken up by the Mn system; as a result it is inversely related to [Mn{sup 2+}] and largely independent of variations in [Zn{sup 2+}]. Because of the suppression of Cd uptake by high [Zn{sup 2+}] and [Mn{sup 2+}] in coastal waters, algal Cd concentrations may be lower in these waters than in the ocean despite the presence of higher coastal [Cd{sup 2+}].

  14. A proposal of "core enzyme" bioindicator in long-term Pb-Zn ore pollution areas based on topsoil property analysis.

    PubMed

    Yang, JinShui; Yang, FengLong; Yang, Yang; Xing, GuanLan; Deng, ChunPing; Shen, YaTing; Luo, LiQiang; Li, BaoZhen; Yuan, HongLi

    2016-06-01

    To study the effects of long-term mining activities on the agricultural soil quality of Mengnuo town in Yunnan province, China, the heavy metal and soil enzyme activities of soil samples from 47 sites were examined. The results showed that long-term mining processes led to point source heavy metal pollution and Pb, Cd, Zn and As were the primary metal pollutants. Polyphenoloxidase was found the most sensitive soil enzyme activity and significantly correlated with almost all the metals (P < 0.05). Amylase (for C cycling), acid phosphatase (for P cycling) and catalase (for redox reaction) activities showed significantly positive correlations (P < 0.05) with Pb, Cd, Zn and As contents. The correlations between soil enzymes activities and Cd, Pb and Zn contents were verified in microcosm experiments, it was found that catalase activity had significant correlations (P < 0.05) with these three metals in short-term experiments using different soils under different conditions. Based on both field investigation and microcosm simulation analysis, oxidoreductases activities (rather than a specific enzyme activity) were suggested to be used as "core enzyme", which could simply and universally indicate the heavy metal pollution degrees of different environments. And hydrolases (for C, N, P and S recycling) could be used as a supplement to improve correlation accuracy for heavy metal indication in various polluted environments. PMID:27038207

  15. Growth and characterization of CdTe single quantum wells confined by Cd 1- xZn xTe alloy and short period CdTe/ZnTe superlattice

    NASA Astrophysics Data System (ADS)

    Magnea, N.; Lentz, G.; Mariette, H.; Feuillet, G.; Dal'bo, F.; Tuffigo, H.

    1989-02-01

    A comparative study of structural and optical properties of CdTe single quantum wells has been performed. Very efficient CdTe-Cd 1-xZn xTe (x Zn ≤ 0.2) wells have been grown and short period superlattices appear as a promising substitute of the alloy.

  16. [In situ immobilization of Pb and Cd in orchard soil using soil ameliorants].

    PubMed

    Tang, Min; Zhang, Jin-Zhong; Zhang, Dan; Chen, Shun; Zhang, Xun; Liu, Wan-Ping; Yu, Jian

    2012-10-01

    In situ immobilization of Pb and Cd in soil of two gardens in Golden Orchard of Chongqing was studied using soil ameliorants, which included eight treatments: control, quicklime, superphosphate, organic manure, quicklime + superphosphate, quicklime + organic manure, superphosphate + organic manure, and quicklime + superphosphate + organic manure. The results showed that all ameliorant treatments could decrease soil acidity in both the loquat garden and peach garden except the superphosphate treatment. Compared with the control, the soil pH in the two gardens increased by 0. 93 and 0. 79 with quicklime treatment for 120 d, respectively. Ameliorant treatments could decrease the bioavailability of Pb and Cd in the soil, and thus reduce the contents of Pb and Cd in the fruits. The available Pb contents in the soil of loquat garden and peach garden significantly decreased after the 150 d treatment with quicklime and superphosphate, by 3.46% and 3.56%, respectively, and the Pb contents in loquat and peach decreased by 18.3% and 14.44%, respectively. The available Cd content in the soil of loquat garden decreased by 10. 95% after the 150 d treatment with quicklime. The available Cd content in the soil of peach garden decreased by 7.09% after the 150 d treatment with quicklime, superphosphate and organic manure. Ameliorant treatments could further decrease the Cd content in loquat, and the Cd contents in loquat and peach decreased by 30.91% and 24.62% with quicklime treatment, respectively. PMID:23233990

  17. Distribution, origin, and transformation of metal and metalloid pollution in vegetable fields, irrigation water, and aerosols near a Pb-Zn mine.

    PubMed

    Luo, Liqiang; Chu, Binbin; Liu, Ying; Wang, Xiaofang; Xu, Tao; Bo, Ying

    2014-01-01

    Pollution of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) in vegetable fields was investigated near a Pb-Zn mine that has been exploited for over 50 years without a tailing reservoir. A total of 205 water, soil, and aerosol samples were taken and quantified by combined chemical, spectrometric, and mineral analytical methods. The pollution origins were identified by Pb isotopes and the pathways of transformation and transport of the elements and minerals was studied. The data showed that the vegetable fields were seriously polluted by As, Cd, and Pb. Some concentrations in the samples were beyond the regulatory levels and not suitable for agricultural activities. This study revealed that: (1) particulate matter is a major pollution source and an important carrier of mineral particles and pollutants; (2) the elements from the polluted water and soils were strongly correlated with each other; (3) Pb isotope ratios from the samples show that Pb minerals were the major pollution sources in the nearby vegetable fields, and the aerosols were the main carrier of mining pollution; (4) the alkaline, rich-carbonate, and wet conditions in this area promoted the weathering and transformation of galena into the secondary minerals, anglesite and cerussite, which are significant evidence of such processes; (5) the soil and the aerosols are a recycled secondary pollution source for each other when being re-suspended with wind.Highlights• Mining activities generated heavy metal pollution in fields around a Pb-Zn mine• The elements from water and soils are strongly correlated• Anglesite and cerussite are evidence of galena transformation into secondary minerals• Particulate matter is an important transport carrier of pollution. PMID:24687780

  18. Experimental study of {sup 113}Cd {beta} decay using CdZnTe detectors

    SciTech Connect

    Goessling, C.; Kiel, H.; Muenstermann, D.; Oehl, S.; Junker, M.; Zuber, K.

    2005-12-15

    A search for the fourfold forbidden {beta} decay of {sup 113}Cd has been performed with CdZnTe semiconductors. With 0.86 kg {center_dot} d of statistics a half-life for the decay of T{sub 1/2}=[8.2{+-}0.2(stat.){sub -1.0}{sup +0.2}(sys.)]x10{sup 15} yr has been obtained. This is in good agreement with published values. A comparison of the spectral shape with the one given on the Table of Isotopes Web page shows a severe deviation.

  19. Sorption selectivity of birnessite particle edges: a d-PDF analysis of Cd(ii) and Pb(ii) sorption by δ-MnO2 and ferrihydrite.

    PubMed

    van Genuchten, Case M; Peña, Jasquelin

    2016-08-10

    Birnessite minerals (layer-type MnO2), which bear both internal (cation vacancies) and external (particle edges) metal sorption sites, are important sinks of contaminants in soils and sediments. Although the particle edges of birnessite minerals often dominate the total reactive surface area, especially in the case of nanoscale crystallites, the metal sorption reactivity of birnessite particle edges remains elusive. In this study, we investigated the sorption selectivity of birnessite particle edges by combining Cd(ii) and Pb(ii) adsorption isotherms at pH 5.5 with surface structural characterization by differential pair distribution function (d-PDF) analysis. We compared the sorption reactivity of δ-MnO2 to that of the nanomineral, 2-line ferrihydrite, which exhibits only external surface sites. Our results show that, whereas Cd(ii) and Pb(ii) both bind to birnessite layer vacancies, only Pb(ii) binds extensively to birnessite particle edges. For ferrihydrite, significant Pb(ii) adsorption to external sites was observed (roughly 20 mol%), whereas Cd(ii) sorption was negligible. These results are supported by bond valence calculations that show comparable degrees of saturation of oxygen atoms on birnessite and ferrihydrite particle edges. Therefore, we propose that the sorption selectivity of birnessite edges follows the same order of that reported previously for ferrihydrite: Ca(ii) < Cd(ii) < Ni(ii) < Zn(ii) < Cu(ii) < Pb(ii). PMID:27183472

  20. Speciation and mobility of Zn, Cu and Pb in a truck farming soil contaminated by sewage irrigation

    NASA Astrophysics Data System (ADS)

    Kirpichtchikova, T.; Manceau, A.; Lanson, B.; Marcus, M. A.; Jacquet, T.

    2003-05-01

    The forrns and mobility of Cu (290 mg/kg), Zn (1103 mg/kg), and Pb (535 mg/kg) in a soil used for intensive truck farining from the Region Ile-de-France, and which has been irrigated for more than a century with sewage water ftom the city of Paris, have been studied by chemical treatments and advanced x-ray techniques. Elemental associations and forms of metals were determined qualitatively and quantitatively by a combination of physical techniques, including μPIXE (Cu, Zn, Pb), μSXRF (Cu, Zn), μEXAFS (Zn) and powder EXAFS (Zn). The nature, number, and relative proportion of Zn species were obtained by principal component analysis and decomposition of Zn K-edge EXAFS spectra. These data collectively indicate that Cu is associated mainly with organic matter, and that Zn and Pb are bound essentially to mineral constituents. Four Zn-containing species were positively identified: Zn-phosphate and phyllosilicate as dominant species, and Zn-Fe oxyhydroxide and willemite (Zn2SiO4) as minor species. Studies are underway to determine the structural forms of Cu and Pb. Depending on the chemical treatment, up to 70% Cu, ~50% Zn, and ~85% Pb can be removed in a few days with citrate and EDTA. Citrate is generally at least as efficient as EDTA, and it has the advantage ofbeing easily biodegradable and, hence, less harmful to ecosystems.

  1. Pb(core)/ZnO(shell) nanowires obtained by microwave-assisted method

    PubMed Central

    2011-01-01

    In this study, Pb-filled ZnO nanowires [Pb(core)/ZnO(shell)] were synthesized by a simple and novel one-step vapor transport and condensation method by microwave-assisted decomposition of zinc ferrite. The synthesis was performed using a conventional oven at 1000 W and 5 min of treatment. After synthesis, a spongy white cotton-like material was obtained in the condensation zone of the reaction system. HRTEM analysis revealed that product consists of a Pb-(core) with (fcc) cubic structure that preferentially grows in the [111] direction and a hexagonal wurtzite ZnO-(Shell) that grows in the [001] direction. Nanowire length was more than 5 μm and a statistical analysis determined that the shell and core diameters were 21.00 ± 3.00 and 4.00 ± 1.00 nm, respectively. Experimental, structural details, and synthesis mechanism are discussed in this study. PMID:21985637

  2. Metal speciation in agricultural soils adjacent to the Irankuh Pb-Zn mining area, central Iran

    NASA Astrophysics Data System (ADS)

    Mokhtari, Ahmad Reza; Roshani Rodsari, Parisa; Cohen, David R.; Emami, Adel; Dehghanzadeh Bafghi, Ali Akbar; Khodaian Ghegeni, Ziba

    2015-01-01

    Mining activities are a significant potential source of metal contamination of soils in surrounding areas, with particular concern for metals dispersed into agricultural area in forms that are bioavailable and which may affect human health. Soils in agricultural land adjacent to Pb-Zn mining operations in the southern part of the Irankuh Mountains contain elevated concentrations for a range of metals associated with the mineralization (including Pb, Zn and As). Total and partial geochemical extraction data from a suite of 137 soil samples is used to establish mineralogical controls on ore-related trace elements and help differentiate spatial patterns that can be related to the effects of mining on the agricultural land soils from general geological and environmental controls. Whereas the patterns for Pb, Zn and As are spatially related to the mining operations they display little correlation with the distribution of secondary Fe + Mn oxyhydroxides or carbonates, suggesting dispersion as dust and in forms with limited bioavailability.

  3. Synthesis and photocatalytic activity of three-dimensional ZnS/CdS composites

    SciTech Connect

    Liu, Shuling Li, Honglin; Yan, Lu

    2013-09-01

    Graphical abstract: - Highlights: • 3D urchin-like ZnS/CdS composites were synthesized via a two-step method. • The CdS nanoparticles were assembled on the thorns of 3D ZnS urchins. • The ZnS/CdS composites show excellent photocatalytic degradation activities. • The modification of CdS on ZnS is responsible for the enhanced property. - Abstract: Urchin-like ZnS/CdS semiconductor composites were successfully synthesized by combining solvothermal route with homogeneous precipitation process. The as-obtained samples were characterized by means of XRD, EDX, TEM, HR-TEM, ED and FE-SEM techniques. The results show that the as-obtained composites were comprised of the hexagonal structure ZnS and CdS, and CdS nanoparticles were assembled on the surfaces of the thorns of urchin-like ZnS. In addition, the optical properties and photocatalytic activities of the as-prepared ZnS/CdS composites toward some organic dyes (such as Methyl Orange, Pyronine B, Rhodamine B and Methylene Blue) were separately investigated. It is found that the ZnS/CdS composites exhibit excellent photocatalytic degradation activity for these dyes under UV irradiation, as compared to corresponding pure ZnS urchins and commercial anatase TiO{sub 2} (P-25). This enhanced activity may be related to the modification of CdS nanoparticles on the surfaces of thorns of ZnS urchins and a tentative mechanism for the enhanced photocatalytic degradation activities of the ZnS/CdS composite catalyst was proposed.

  4. Immobilization of Cu, Pb and Zn in mine-contaminated soils using reactive materials.

    PubMed

    Navarro, Andrés; Cardellach, Esteve; Corbella, Mercé

    2011-02-28

    Immobilization processes were used to chemically stabilize soil contaminated with Cu, Pb and Zn from mine tailings and industrial impoundments. We examined the effectiveness of ordinary Portland cement (OPC), phosphoric acid and MgO at immobilizing Cu, Pb and Zn in soil contaminated by either mine tailings or industrial and mine wastes. The effectiveness was evaluated using column leaching experiments and geochemical modelling, in which we assessed possible mechanisms for metal immobilization using PHREEQC and Medusa numerical codes. Experimental results showed that Cu was mobilized in all the experiments, whereas Pb immobilization with H(3)PO(4) may have been related to the precipitation of chloropyromorphite. Thus, the Pb concentrations of leachates of pure mining and industrial contaminated soils (32-410 μg/l and 430-1000 μg/l, respectively) were reduced to 1-60 and 3-360 μg/l, respectively, in the phosphoric acid experiment. The mobilization of Pb at high alkaline conditions, when Pb(OH)(4)(-) is the most stable species, may be the main obstacle to the use of OPC and MgO in the immobilization of this metal. In the mining- and industry-contaminated soil, Zn was retained by OPC but removed by MgO. The experiments with OPC showed the Zn decrease in the leachates of mining soil from 226-1960 μg/l to 92-121 μg/l. In the industrial contaminated soil, the Zn decrease in the leachates was most elevated, showing >2500 μg/l in the leachates of contaminated soil and 76-173 μg/l in the OPC experiment. Finally, when H(3)PO(4) was added, Zn was mobilized. PMID:21190796

  5. CdSeS/ZnS alloyed nanocrystal lifetime and blinking studies under electrochemical control.

    PubMed

    Qin, Wei; Shah, Raman A; Guyot-Sionnest, Philippe

    2012-01-24

    Alloyed CdSeS nanocrystals allow tuning between the CdSe and CdS band edges while remaining relatively small. The CdSeS cores also lead to a reduced electron confinement energy and a slower biexciton decay rate compared to CdSe cores of similar sizes. A ZnS shell synthesis procedure allows stable CdSeS/ZnS colloidal quantum dots (QDs) suitable for single dot imaging. These are compared to CdSe/ZnS of similar core size. The blinking off-exponents of the CdSeS/ZnS dots in air and on a glass substrate were slightly larger. Using electrochemistry with ensemble and single dot measurements, the trion lifetime of CdSeS/ZnS dot is resolved to be ~0.75 ns, while it is about 0.15 ns for CdSe/ZnS. In addition, the blinking behavior of single CdSeS/ZnS QDs is largely suppressed when in the trion state. PMID:22191620

  6. Phytoextraction of Pb and Cd from a superfund soil: effects of amendments and croppings.

    PubMed

    Bricker, T J; Pichtel, J; Brown, H J; Simmons, M

    2001-01-01

    In a growth chamber, maize (Zea mays) and Indian mustard (Brassica juncea) were grown over two croppings in soil from a Superfund site (PbTotal = 65,200 mg/kg and CdTotal = 52mg/kg). Soil treatments consisted of ethylenediaminetetraacetic acid, sodium citrate and composted sewage sludge, each at two rates (EDTA .05%, EDTA .2%, citrate .05%, citrate .2%, CSS 5% and CSS 10%, respectively). In most cases, the EDTA and citrate treatments were superior in terms of solubilizing soil Pb for root uptake and translocation into above-ground biomass. In the first maize crop, the EDTA .2% treatment resulted in 2,435 and 9,389mg/kg Pb in shoot and root tissues, respectively. The CSS treatments typically resulted in lowest Pb and Cd removal efficiencies. Lead remaining in the soil after two croppings was mainly associated with the carbonate, organic, and residual fractions, which represent the less bioavailable forms. Soil Cd was generally more mobile for plant uptake than soil Pb. The EDTA .2% and citrate treatments were most successful in promoting Cd uptake by both maize and mustard. Although Pb concentrations (mg/kg tissue) were lower for maize than mustard, the former removed more total Pb (0.2 mg per pot, mean over all treatments), compared to mustard (0.03 mg), by virtue of its higher biomass production. PMID:11688677

  7. Aqueous CdPbS quantum dots for near-infrared imaging

    NASA Astrophysics Data System (ADS)

    Au, Giang H. T.; Y Shih, Wan; Tseng, S.-Ja; Shih, Wei-Heng

    2012-07-01

    Quantum dots (QDs) are semiconducting nanocrystals that have photoluminescent (PL) properties brighter than fluorescent molecules and do not photo-bleach, ideal for in vivo imaging of diseased tissues or monitoring of biological processes. Near-infrared (NIR) fluorescent light within the window of 700-1000 nm, which is separated from the major absorption peaks of hemoglobin and water, has the potential to be detected several millimeters under the surface with minimal interference from tissue autofluorescence. Here we report the synthesis and bioimaging demonstration of a new NIR QDs system, namely, CdPbS, made by an aqueous approach with 3-mercaptopropionic acid (MPA) as the capping molecule. The aqueous-synthesized, MPA-capped CdPbS QDs exhibited an NIR emission in the range of 800-950 nm with xi ≥ 0.3, where xi denotes the initial Pb molar fraction during the synthesis. Optimal PL performance of the CdPbS QDs occurred at xi = 0.7, which was about 4 nm in size as determined by transmission electron microscopy, had a rock salt structure and a quantum yield of 12%. Imaging of CdPbS QDs was tested in membrane staining and transfection studies. Cells transfected with CdPbS QDs were shown to be visible underneath a slab of chicken muscle tissue of up to 0.7 mm in thickness without the use of multiple-photon microscopy.

  8. Biomonitoring potential of five sympatric Tillandsia species for evaluating urban metal pollution (Cd, Hg and Pb)

    NASA Astrophysics Data System (ADS)

    Sánchez-Chardi, Alejandro

    2016-04-01

    The present study quantifies non essential heavy metals highly toxic for biological systems (Pb, Hg and Cd) in five autochthonous epiphytic plants from Tillandsia genus (T. recurvata, T. meridionalis, T. duratii, T. tricholepis, T. loliacea) according to different traffic levels (reference, low, medium and high polluted sites) in Asunción (Paraguay). The three metals increased in polluted sites following Pb (till 62.99 ppm in T. tricholepis) > Cd (till 1.35 ppm in T. recurvata) > Hg (till 0.36 ppm in T. recurvata) and Pb and Cd levels were directly related to traffic flow. Although the species showed similar bioaccumulation pattern (namely, higher levels of metals in polluted sites), enrichment factors (maximum EF values 37.00, 18.16, and 11.90 for Pb, Hg, and Cd, respectively) reported T. tricholepis as the most relevant bioindicator due to its wide distribution and abundance in study sites, low metal content in control site and high metal contents in polluted sites, and significant correlations with traffic density of Pb and Cd. This study emphasizes the necessity of biomonitoring air pollution in areas out of air monitoring control such as Asunción, where the high levels of metal pollution especially Pb, may represent an increment of risk for the human population inhabiting this urban area.

  9. ZnO@CdS Core-Shell Heterostructures: Fabrication, Enhanced Photocatalytic, and Photoelectrochemical Performance

    NASA Astrophysics Data System (ADS)

    Ding, Meng; Yao, Nannan; Wang, Chenggang; Huang, Jinzhao; Shao, Minghui; Zhang, Shouwei; Li, Ping; Deng, Xiaolong; Xu, Xijin

    2016-04-01

    ZnO nanorods and ZnO@CdS heterostructures have been fabricated on carbon fiber cloth substrates via hydrothermal and electrochemical deposition. Their photocatalytic properties were investigated by measuring the degradation of methylene blue under ultraviolet light irradiation. The result illustrated that the photodegradation efficiency of ZnO@CdS heterostructures was better than that of pure ZnO nanorods, in which the rate constants were about 0.04629 and 0.02617 min-1. Furthermore, the photocurrent of ZnO@CdS heterostructures achieved 102 times enhancement than pure ZnO nanorods, indicating that more free carriers could be generated and transferred in ZnO@CdS heterostructures, which could be responsible for the increased photocatalytic performance.

  10. ZnO@CdS Core-Shell Heterostructures: Fabrication, Enhanced Photocatalytic, and Photoelectrochemical Performance.

    PubMed

    Ding, Meng; Yao, Nannan; Wang, Chenggang; Huang, Jinzhao; Shao, Minghui; Zhang, Shouwei; Li, Ping; Deng, Xiaolong; Xu, Xijin

    2016-12-01

    ZnO nanorods and ZnO@CdS heterostructures have been fabricated on carbon fiber cloth substrates via hydrothermal and electrochemical deposition. Their photocatalytic properties were investigated by measuring the degradation of methylene blue under ultraviolet light irradiation. The result illustrated that the photodegradation efficiency of ZnO@CdS heterostructures was better than that of pure ZnO nanorods, in which the rate constants were about 0.04629 and 0.02617 min(-1). Furthermore, the photocurrent of ZnO@CdS heterostructures achieved 10(2) times enhancement than pure ZnO nanorods, indicating that more free carriers could be generated and transferred in ZnO@CdS heterostructures, which could be responsible for the increased photocatalytic performance. PMID:27090656

  11. Characterization of Aerosols Containing Zn, Pb, and Cl from an Industrial Region of Mexico City

    SciTech Connect

    Moffet, Ryan C; Desyaterik, Yury; Hopkins, Rebecca J; Tivanski, Alexei V; Gilles, Marry K; Wang, Yan A; Shutthanandan, V; Molina, Luisa T; Abraham, Rodrigo G; Johnson, Kirsten S; Mugica, Violeta; Molina, Mario J; Laskin, Alexander; Prather, Kimberly A

    2008-10-01

    During the March, 2006 MILAGRO campaign, measurements in the Northern Mexico City Metropolitan Area revealed the frequent appearance of particles with a characteristically high content of internally mixed Zn, Pb, Cl, and P. A comprehensive study of the chemical and physical properties of these particles was performed using a complementary combination of aerosol measurement techniques. Individual particles were analyzed using Aerosol Time-of-Flight Mass Spectrometry (ATOFMS) and Computer Controlled Scanning Electron Microscopy/Energy Dispersive X-Ray spectroscopy (CCSEM/EDX). Proton Induced X-Ray Emission (PIXE) analysis of bulk aerosol samples provided time-resolved mass concentrations of individual elements. The PIXE measurements indicated that Zn is more strongly correlated with Cl than with any other element and that Zn concentrations are higher than other non-ferrous transition metals. The Zn- and Pb - containing particles have both spherical and non-spherical morphologies. Many metal rich particles had needle-like structures and were found to be composed of ZnO and/or Zn(NO3)2∙6H2O as indicated by scanning transmission x-ray microscopy/near edge X-ray absorption spectroscopy (STXM/NEXAFS). The Zn and Pb rich particles were primarily in the submicron size range and internally mixed with elemental carbon. The unique chemical associations most closely match signatures acquired for garbage incineration. This unique combination of complementary analytical techniques has allowed for a comprehensive evaluation of Zn- and Pb- containing particles in a complex urban environment, highlighting unique characteristics that give powerful insight into their origin.

  12. Engineering Zn1-xCdxS/CdS Heterostructures with Enhanced Photocatalytic Activity.

    PubMed

    Li, Kui; Chen, Rong; Li, Shun-Li; Xie, Shuai-Lei; Dong, Long-Zhang; Kang, Zhen-Hui; Bao, Jian-Chun; Lan, Ya-Qian

    2016-06-15

    Various porous Zn1-xCdxS/CdS heteorostructures were achieved via in situ synthesis method with organic amines as the templates. Because of the larger radius of Cd(2+) than that of Zn(2+), CdS quantum dots are formed and distributed uniformly in the network of Zn1-xCdxS. The Zn1-xCdxS/CdS heterostructure with small Cd content (10 at%) derived from ethylenediamine shows very high H2-evolution rate of 667.5 μmol/h per 5 mg photocatalyst under visible light (λ ≥ 420 nm) with an apparent quantum efficiency of 50.1% per 5 mg at 420 nm. Moreover, this Zn1-xCdxS/CdS heterostructure photocatalyst also shows an excellent photocatalytic stability over 100 h. PMID:27172231

  13. Interrelationships between Cd, Zn and birth weight in neonates of women who smoke

    SciTech Connect

    Kuhnert, B.R.; Kuhnert, P.M.; Groh-Margo, S.; Webster, S.; Erhard, P.

    1986-03-05

    A study was designed to test the hypothesis that the increased cadmium level in pregnant women who smoke alters the metabolism of zinc in the maternal-fetal unit, and that this altered Zn metabolism may contribute to lower birth weight infants. One hundred-thirty mother/infant pairs were studied. Maternal whole blood and placental Cd were analyzed by graphite furnace atomic absorption spectrophotometry; maternal and fetal plasma, red blood cell and placental Zn by flame atomic absorption spectroscopy. Maternal plasma thiocyanate (SCN) levels were used as an index of smoking status. Zn intake was estimated by diet history in a subgroup of 34 patients. The data were analyzed using t-tests, correlation and stepwise multiple regression techniques. No differences in Zn intake were found between pregnant women who smoked and those who did not. The average daily intake of Zn was 10.2 +/- 5 mg; this is less than the RDA for Zn during pregnancy. The data show that there are significant positive correlations between SCN levels and levels of whole blood Cd, placental Cd, and placental Zn. Cord vein samples from infants of mothers who smoked had decreased red blood cell Zn. This was particularly true in nulliparous patients. In all patients, maternal whole blood Cd was found to be negatively related to birth weight and cord vein red blood cell Zn was positively related to birth weight. The results support the hypothesis of a Cd-Zn interaction in pregnant women who smoke. Additional findings suggest an effect of parity on the interaction between Cd and Zn. Placental Cd was found to be negatively related to birth weight in nulliparous patients (n=21). In multiparous patients (n=109) placental Zn was inversely related to birth weight. In patients with parity 2 or greater (n=54), placental Cd was directly predictive of placental Zn. These results may reflect a less favorable Zn nutritional status with increasing parity.

  14. Direct characterization of polymer encapsulated CdSe/CdS/ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Zorn, Gilad; Dave, Shivang R.; Weidner, Tobias; Gao, Xiaohu; Castner, David G.

    2016-06-01

    Surface engineering advances of semiconductor quantum dots (QDs) have enabled their application to molecular labeling, disease diagnostics and tumor imaging. For biological applications, hydrophobic core/shell QDs are transferred into aqueous solutions through the incorporation of water-solubility imparting moieties, typically achieved via direct exchange of the native surface passivating ligands or indirectly through the adsorption of polymers. Although polymeric encapsulation has gained wide acceptance, there are few reports addressing the characterization of the adsorbed polymers and existing theoretical analyses are typically based on simple geometric models. In this work, we experimentally characterize and quantify water-soluble QDs prepared by adsorption of amphiphilic poly(maleic anhydride-alt-1-tetradecene) (PMAT, MW ~ 9000) onto commercially available CdSe/CdS/ZnS (CdSe/CdS/ZnS-PMAT). Using X-ray photoelectron spectroscopy (XPS) we determined that ~ 15 PMAT molecules are adsorbed onto each QD and sum frequency generation (SFG) vibrational spectra were utilized to investigate the mechanism of interaction between PMAT molecules and the QD surface. Importantly, when employed together, these techniques constitute a platform with which to investigate any polymer-nanoparticle complex in general.

  15. Optical properties of CdS and CdS/ZnS quantum dots synthesized by reverse micelle method

    NASA Astrophysics Data System (ADS)

    Lien, Vu Thi Kim; Viet Ha, Chu; Tien Ha, Le; Nhu Dat, Nguyen

    2009-09-01

    The CdS and CdS/ZnS semiconductor quantum dots have been synthesized by reverse micelle method using sodium bis (2-ethylhexyl) sulfosuccinate (AOT) surfactant agent. The quantum dot diameter is about 2.5 to 4 nm depending on the concentration of the surfactant agent. It is interesting that, in contrast to other colloidal methods, the size of quantum dots does not depend on the growth time. The absorption spectra of CdS quantum dots show the narrow size distribution. The photoluminescence (PL) spectra include two bands, the intrinsic emission of CdS nanocrystals and the emission of surface states. There is noticeable increase of the PL intensity and subsequent photostability of CdS/ZnS core-shell quantum dots in comparison with CdS quantum dots without the ZnS shell.

  16. Purification of CdZnTe by Electromigration

    DOE PAGESBeta

    Kim, K.; Kim, Sangsu; Hong, Jinki; Lee, Jinseo; Hong, Taekwon; Bolotnikov, A. E.; Camarda, G. S.; James, R. B.

    2015-04-14

    Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 lm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. Furthermore, a CZT detector fabricated from the middle portion of themore » electromigrated CZT boule showed an improved mobility-lifetime product of 0.91 10-2 cm2 /V, compared to that of 1.4 10-3 cm2 /V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.« less

  17. Purification of CdZnTe by Electromigration

    SciTech Connect

    Kim, K.; Kim, Sangsu; Hong, Jinki; Lee, Jinseo; Hong, Taekwon; Bolotnikov, A. E.; Camarda, G. S.; James, R. B.

    2015-04-14

    Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 lm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. Furthermore, a CZT detector fabricated from the middle portion of the electromigrated CZT boule showed an improved mobility-lifetime product of 0.91 10-2 cm2 /V, compared to that of 1.4 10-3 cm2 /V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.

  18. Purification of CdZnTe by electromigration

    SciTech Connect

    Kim, K.; Kim, Sangsu; Hong, Jinki; Lee, Jinseo; Hong, Taekwon; Bolotnikov, A. E.; Camarda, G. S.; James, R. B.

    2015-04-14

    Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 μm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. A CZT detector fabricated from the middle portion of the electro-migrated CZT boule showed an improved mobility-lifetime product of 0.91 × 10{sup −2} cm{sup 2}/V, compared with that of 1.4 × 10{sup −3} cm{sup 2}/V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.

  19. Evidence for microbial activity in the formation of carbonate-hosted Zn-Pb deposits

    NASA Astrophysics Data System (ADS)

    Kucha, H.; Raith, J.

    2009-04-01

    *Kucha H **Raith J *University of Mining and Metallurgy, Faculty of Geology, Geophysics and Environmental Protection, Mickiewicza 30, PL-30-059 Krakow, Poland. ** University of Leoben, Department of Applied Geosciences and Geophysics, A-8700 Leoben, Peter Tunner Str. 5, Austria Evidence for microbial activity in the formation of carbonate-hosted Zn-Pb deposits To date evaluation of bacterial processes in the formation of carbonate-hosted Zn-Pb deposits is largely based on sulphur isotope evidence. However, during a past few years, textural criteria, have been established, which support the bacterial origin of many of these deposits. This has received a strong support from micro-, and nano-textures of naturally growing bacterial films in a flooded tunnel within carbonates that host the Piquette Zn-Pb deposit (Druschel et al., 2002). Bacterial textures, micro- and nano textures found in carbonate-hosted Zn-Pb deposits are: i)wavy bacterial films up to a few mm thick to up to a few cm long composed of peloids, ii)semimassive agglomeration of peloids in the carbonate matrix, and iii)solitary peloids dispersed in the carbonate matrix. Peloids are usually composed of a distinct 50-90um core most often made up of Zn-bearing calcite surrounded by 30-60um thick dentate rim composed of ZnS. Etching of Zn-carbonate cores reveals 1 - 2um ZnS filaments, and numerous 15 to 90nm large ZnS nano-spheres (Kucha et al., 2005). In massive ore composite Zn-calcite - sphalerite peloids are entirely replaced by zinc sulphide, and form peloids ghosts within banded sulphide layers. Bacterially derived micro- and nano-textures have been observed in the following carbonate-hosted Zn-Pb deposits: 1)Irish-type Zn-Pb deposits. In the Navan deposit the basic sulphur is isotopically light bacteriogenic S (Fallick at al., 2001). This is corroborated by semimassive agglomerations of composite peloids (Zn-calcite-ZnS corona or ZnS core-melnikovite corona). Etching of Zn-calcite core reveals globular

  20. CdTe and ZnTe metal interface formation and Fermi-level pinning

    NASA Technical Reports Server (NTRS)

    Wahi, A. K.; Carey, G. P.; Chiang, T. T.; Lindau, I.; Spicer, W. E.

    1989-01-01

    Interfacial morphology and Fermi-level pinning behavior at the interfaces of Al, Ag, and Pt with UHV-cleaved CdTe and ZnTe are studied using X-ray photoelectron and ultraviolet photoemission spectroscopies. Results are compared to metal/HgCdTe interface formation. For Al/CdTe, a case is found where significantly greater intermixing occurs in CdTe than seen on HgCdTe. The Al/ZnTe interface is also more abrupt than Al/CdTe. Band bending results for interfaces of all three metals with p-CdTe and p-ZnTe are presented and implications for metal/HgZnTe interface formation are considered.

  1. Synthesis and characterization of quasi-aligned ZnCdO nanorods

    NASA Astrophysics Data System (ADS)

    Wang, F. Z.; Ye, Z. Z.; Ma, D. W.; Zhu, L. P.; Zhuge, F.; He, H. P.

    2005-10-01

    Quasi-aligned ZnCdO single-crystal nanorods were prepared for the first time by using thermal evaporation of Zn and CdCl2 on a Si substrate with the presence of Au catalyst. The maximum Cd content was up to about 16.7at.%, which was significantly larger than the thermodynamic solid solubility limits. The ZnCdO nanorods have uniform flat hexagonal crystallographic planes with diameters of about 150nm. Notably, with the Cd content increasing, the ultraviolet near-band-edge emission was redshifted to 407nm(3.04eV ) from 386nm(3.21eV). The direct modulation of the band gap caused by Cd substitution is responsible for the redshift. The possible growth mechanism of the ZnCdO nanorods was discussed.

  2. Cd and Te-based ohmic contact materials to p-Type ZnSe

    NASA Astrophysics Data System (ADS)

    Hashimoto, K.; Koide, Y.; Tadanaga, O.; Oku, T.; Teraguchi, N.; Tomomuea, Y.; Suzuki, A.; Murakami, Masanori

    1996-12-01

    In order to explore a possibility of forming an intermediate semiconductor layer with low Schottky barrier by the conventional deposition and annealing technique, the electrical properties of Cd and Te-based contacts on the nitrogendoped ZnSe substrates have been investigated. Cd in the Cd/W contact reacted with the ZnSe substrate after annealing at temperatures above 250°C and formed epitaxial Ccx}Zn1-xSe layers, leading to reduction of the “turn-on” voltage (VT) from about 11 to 6 V (here, a slash “/” between Cd and W means the deposition sequence). The reduction of the Vn} value by annealing at elevated temperatures was also observed for the Bi-Cd/W and In-Cd/W contacts. The average Cd composition (x) in the Cdn}Zn1-xSe layers was measured to be larger than 0.9, which agreed with the values estimated from the calculated Cd-Zn-Se phase diagrams. The ohmic behavior was strongly influenced by the thickness of the CdxZn1-xSe layer, the density of misfit dislocations formed at the interface between the Cdx Zn1-x Se and the ZnSe, and/or the total area of the Cd Zn. Se layers covering the ZnSe surface. The present result suggests that formation of the large-areal CcxZn1-xSe layers with thin thickness is crucial to achieve further reduction of the VT value by the conventional deposition and annealing technique. Also, the VT reduction was not obtained for the Te/W contact even after annealing at temperatures close to 300°C, which was explained to be due to absence of ternary ZnSe1-xTen intermediate layers.

  3. Investigation of CdZnTe for Thin-Film Tandem Solar Cell Applications: Preprint

    SciTech Connect

    Dhere, R.; Gessert, T.; Zhou, J.; Asher, S.; Pankow, J.; Moutinho, H.

    2003-04-01

    Modeling of two-junction tandem devices shows that for optimal device performance, the bandgap of the top cell should be around 1.6-1.8 eV. CdZnTe alloys can be tailored to yield bandgaps in the desired range. In this study, we considered were used to fabricate these films, using close-spaced sublimation (CSS) and radio-frequency sputtering (RFS) techniques. In the first approach, we used mixed powders of CdTe and ZnTe as the source for film deposition by CSS. Even for the ZnTe/CdTe (95:5 ratio) source material, the deposited films were entirely CdTe due to higher vapor pressure of CdTe. In the second approach, we used pre-alloyed CdZnTe powders (CERAC, Inc.) as the source. Due to the lower sticking coefficient of Zn, even for the source composition of 75% Zn, these films contained very low quantities of Zn (~5%). We tried unsuccessfully to increase the Zn content in the films by confining Zn vapor by enclosing the region between the source and substrate, reducing the substrate temperature to 400C, and adjusting the source/substance distance. Finally, we used thin-film couples consisting of 300-nm-thick CdTe deposited by CSS and 300-nm-thick ZnTe deposited by RFS; the samples were then heat-treated in cadmium chloride vapor. Compositional analysis of the samples showed extensive interdiffusion of Cd and Zn for the annealed samples. We will present the data on the various stack configurations of CdTe and ZnTe, the effect of different post-deposition anneals, the effect of oxygen on the interdiffusion and alloy formation and its possible correlation to the device performance degradation.

  4. Formation of core@multi-shell CdSe@CdZnS-ZnS quantum dot heterostructure films by pulse electrophoresis deposition

    NASA Astrophysics Data System (ADS)

    Raj, Sudarsan; Yun, Jin Hyeon; Adilbish, Ganpurev; Ch, Rama Krishna; Lee, In Hwan; Lee, Min Sang; Yu, Yeon-Tae

    2015-07-01

    CdSe@CdZnS-ZnS core@multi-shell quantum dot (QD) heterostructures were deposited on fluorine doped tinoxide (FTO) glass substrate by pulse electrophoresis deposition (EPD). Field emissions scanning electron microscopy (FESEM) images reveal that the number of QDs deposited on the substrate increased with prolonged deposition time. Ethanol is the better solution medium as compared to 2-propanol for pulse electrophoresis deposition. For longer deposition time the intensity of photo luminescence (PL) peak increased.

  5. Stable core/shell CdTe/Mn-CdS quantum dots sensitized three-dimensional, macroporous ZnO nanosheet photoelectrode and their photoelectrochemical properties.

    PubMed

    Li, Weili; Sheng, Pengtao; Feng, Hongyan; Yin, Xuehua; Zhu, Xuewei; Yang, Xu; Cai, Qingyun

    2014-08-13

    A novel photoelectrode based on ZnS/CdTe/Mn-CdS/ZnS-sensitized three-dimensional macroporous ZnO nanosheet (NS) has been prepared by electrodeposition and successive ion layer adsorption and reaction (SILAR) method. The photoelectrode performances were significantly improved through the coupling of the core/shell CdTe/Mn-CdS quantum dots (QDs) with ZnO NS, and the introduction of the ZnS layer as a potential barrier. The photocurrent density systematically increases from ZnO NS (0.45 mA/cm(2)), CdTe/Mn-CdS/ZnO NS (4.98 mA/cm(2)), to ZnS/CdTe/Mn-CdS/ZnS/ZnO (6.23 mA/cm(2)) under the irradiation of AM 1.5G simulated sunlight. More important, the ZnS/CdTe/Mn-CdS/ZnS-sensitized ZnO NS photoelectrode provides a remarkable photoelectrochemical cell efficiency of 4.20% at -0.39 V vs Ag/AgCl. PMID:25010851

  6. Timing of foliar Zn application plays a vital role in minimizing Cd accumulation in wheat.

    PubMed

    Saifullah; Javed, Hina; Naeem, Asif; Rengel, Zed; Dahlawi, Saad

    2016-08-01

    Due to chemical and biochemical similarities between cadmium (Cd) and zinc (Zn), application of Zn may minimize Cd uptake by plants and ameliorate its toxicity. However, there is poor understanding of the comparative effectiveness of the foliar Zn application at different growth stages on Cd toxicity and accumulation in wheat. The present study was carried out to compare the effectiveness of foliarly applied Zn at different stages of plant growth to minimize Cd accumulation in wheat grains. Wheat (cv AARI-2011) was grown at three levels of soil Cd (0, 2.5, and 5.0 mg kg(-1)). Foliar application of Zn was carried out at either tillering, jointing, booting, heading, or grain filling stage using 0.05 % w/v aqueous solution of ZnSO4 · 7H2O. Increasing soil Cd had a negative effect on growth and yield attributes, including tiller production, root length and dry weight, plant height, 100-grain weight and grain and straw yield. Zinc foliar spray increased grain yield by increasing tiller production; importantly, an application at booting was more effective than at other stages. Foliarly applied Zn decreased Cd concentration in the roots, straw, and grain. Similar to grain yield, the largest decrease (74 %) in Cd concentration was associated with Zn foliar spray at booting. Grain yield was negatively related to grain Cd concentration which in turn showed a negative relationship with Zn concentration in leaves and grains. It is concluded that the booting stage is the suitable time for foliar application of Zn to (i) effectively minimize a Cd-induced loss in grain yield and (ii) decrease grain Cd concentration. PMID:27164881

  7. The distribution of heavy metals including Pb, Cd and Cr in Kendari Bay surficial sediments.

    PubMed

    Armid, Alrum; Shinjo, Ryuichi; Zaeni, Ahmad; Sani, Asrul; Ruslan, Ruslan

    2014-07-15

    The surficial coastal sediments in Kendari Bay are sampled in the field to determine the concentration and pollution level of three heavy metals (Pb, Cd and Cr). Twenty-five sampling points ranging from the inner (Wanggu River) to the outer area of the bay have been chosen. The physicochemical properties, such as temperature, pH, salinity and TDS of the overlying water, as well as the sediment type and TOC of the surficial sediments, are also measured. The total concentrations of the Pb, Cd and Cr in the sediment samples are quantified using inductively-coupled plasma mass spectrometry (ICP-MS). The concentrations of the heavy metals (Pb, Cd and Cr) ranged from 0.84 to 17.02 μg/g, 0.02 to 0.17 μg/g and 1.92 to 40.11 μg/g (dry weight), respectively, following the Cr>Pb>Cd sequence. To assess the degree of contamination, a geoaccumulation index (Igeo) is measured. Kendari Bay is not a contaminated area regarding Pb, Cd and Cr. PMID:24880681

  8. An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration.

    PubMed

    Liu, Jingyong; Fu, Jiewen; Ning, Xun'an; Sun, Shuiyu; Wang, Yujie; Xie, Wuming; Huang, Shaosong; Zhong, Sheng

    2015-09-01

    The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4. PMID:26354691

  9. Study on structure and properties of CuZn40Pb alloy

    NASA Astrophysics Data System (ADS)

    Achiţei, D. C.; Minciună, M. G.; Vizureanu, P.; Sandu, A. V.; Cimpoeşu, R.; Istrate, B.

    2016-06-01

    The paper shows aspects about the behavior of Cu-Zn-Pb alloys a subjected to the temperatures variation and corrosion resistance in saline medium (sea water). The chemical composition was determined by spectral analysis on optical spectrometer, type Foundry Masters. The experiments are completed by a microstructure analysis made on scanning electronic microscope.

  10. Syntheses, crystal structure and physical properties of new Zintl phases Ba3T2As4 (T=Zn, Cd)

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Xia, Sheng-Qing; Tao, Xu-Tang

    2013-02-01

    Through high temperature Pb-flux reactions, two new arsenide Zintl compounds, Ba3Zn2As4 and Ba3Cd2As4, were successfully obtained and their structures were accurately determined with Single-Crystal X-ray Diffraction. Both compounds are isotypic to Ba3Cd2Sb4 and crystallize in the monoclinic space group C2/m (No=12) with cell parameters of a=16.916(4)/17.089(3) Å, b=4.497(1)/4.6076(7) Å, c=7.225(2)/7.304(1) Å and β=113.147(2)/112.312(1) ° for Ba3Zn2As4 and Ba3Cd2As4, respectively. Electrical resistivity measurement on Ba3Cd2As4 reveals semiconducting behavior between 10 and 100 K, which results in a very small band gap of 0.01 eV. According to TG/DSC analyses, Ba3Cd2As4 exhibits good thermal stability and does not decompose below 950 K.

  11. Investigation of transport properties of ZnO/PbS heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Cheng, Yang; Whitaker, Michael D. C.; Whiteside, Vincent R.; Bumm, Lloyd A.; Sellers, Ian R.

    Lead sulfide (PbS) and lead selenide (PbSe) colloidal quantum dots (CQDs) are considered as a potential candidate material for solar cell applications due to their large band gap tunability range (0.5 to 1.7 eV) and cost-effective solution based processing. A series of Glass/ITO/ZnO/PbS/MoO3/Au heterojunction solar cells were processed and analyzed. A stable (reproducible) 2% conversion efficiency under 1-sun is achieved based on the result of J - V measurements. Absorbance and external quantum efficiency (EQE) measurements clearly show photo-generated carrier extraction from PbS active layers in the solar cell. However, a non-ideal J - V behavior is observed in current-voltage measurements. This behavior may be attributed to a high density of trap states at the QD surface or defect states at the PbS/ZnO or ITO/ZnO interfaces. C-V and Impedance spectroscopy measurements are used to study this unusual behavior. These techniques could also help probe the transport properties and limitation of these heterojunction solar cells. This research is funded through NASA EPSCoR program Award # NNX13AN101A.

  12. Formation of highly luminescent Zn1-xCdxSe nanocrystals using CdSe and ZnSe seeds

    NASA Astrophysics Data System (ADS)

    Zhang, Ruili; Yang, Ping

    2013-05-01

    High-quality colloidal Zn1-xCdxSe nanocrystals (NCs) with tunable photoluminescence (PL) from blue to orange were synthesized using oleic acid as a capping agent. The Zn1-xCdxSe NCs were prepared through two approaches: using CdSe or ZnSe seeds. In the case of CdSe NCs as seeds, Zn1-xCdxSe NCs were fabricated by the reaction of Zn, Cd, and Se precursors in the coordinating solvent system at high temperature. The Zn1-xCdxSe NCs revealed orange emitting. A significant blue-shift of absorption and PL spectra were observed with time, indicating the formation of ternary NCs. In contrast, Zn1-xCdxSe NCs revealed blue to green PL for ZnSe NCs as seeds. This is ascribed to an embryonic nuclei-induced alloying process. With increasing time, the Zn1-xCdxSe NCs exhibited a red-shift both in their absorption and PL spectra. This is attributed to the engineering in band gap energy via the control of NC composition. The PL properties of as-prepared alloyed NCs are comparable or even better than those for the parent binary systems. The PL peak wavelength of the Zn1-xCdxSe NCs depended strongly on reaction time and the molar ratio of Cd/Zn. The Zn1-xCdxSe NCs revealed a spherical morphology and exhibited a wurtzite structure according to transmission electron microscopy observation and an X-ray diffraction analysis.

  13. Interdiffusion of CdS and Zn2SnO4 layers and its application in CdS/CdTe polycrystalline thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Wu, X.; Asher, S.; Levi, D. H.; King, D. E.; Yan, Y.; Gessert, T. A.; Sheldon, P.

    2001-04-01

    In this work, we found that the interdiffusion of the CdS and Zn2SnO4 (ZTO) layers can occur either at high temperature (550-650 °C) in Ar or at lower temperature (400-420 °C) in a CdCl2 atmosphere. By integrating a Zn2SnO4 film into a CdS/CdTe solar cell as a buffer layer, this interdiffusion feature can solve several critical issues and improve device performance and reproducibility of both SnO2-based and Cd2SnO4-based CdTe cells. Interdiffusion consumes the CdS film from both the ZTO and CdTe sides during the device fabrication process and improves quantum efficiency at short wavelengths. The ZTO film acts as a Zn source to alloy with the CdS film, which results in increases in the band gap of the window layer and in short-circuit current density Jsc. Interdiffusion can also significantly improve device adhesion after CdCl2 treatment, thus providing much greater process latitude when optimizing the CdCl2 process step. The optimum CdCl2-treated CdTe device has high quantum efficiency at long wavelength, because of its good junction properties and well-passivated CdTe film. We have fabricated a Cd2SnO4/Zn2SnO4/CdS/CdTe cell demonstrating an NREL-confirmed total-area efficiency of 15.8% (Voc=844.3 mV, Jsc=25.00 mA/cm2, and fill factor=74.82%). This high-performance cell is one of the best thin-film CdTe solar cells in the world.

  14. Molecular Beam Epitaxy Growth of HgCdTe on Large-Area Si and CdZnTe Substrates

    NASA Astrophysics Data System (ADS)

    Reddy, M.; Peterson, J. M.; Vang, T.; Franklin, J. A.; Vilela, M. F.; Olsson, K.; Patten, E. A.; Radford, W. A.; Bangs, J. W.; Melkonian, L.; Smith, E. P. G.; Lofgreen, D. D.; Johnson, S. M.

    2011-08-01

    This paper presents the status of HgCdTe growth on large-area Si and CdZnTe substrates at Raytheon Vision Systems (RVS). The different technological tools that were used to scale up the growth from 4 inch to 6 inch diameter on Si and from 4 cm × 4 cm to 8 cm × 8 cm on CdZnTe without sacrificing the quality of the layers are described. Extremely high compositional uniformity and low macrodefect density were achieved for single- and two-color HgCdTe layers on both Si and CdZnTe substrates. Finally, a few examples of detector and focal-plane array results are included to highlight the importance of high compositional uniformity and uniformly low macrodefect density of the epitaxial layers in obtaining high operability and low cluster outages in single- and two-color focal-plane arrays (FPAs).

  15. Comparison of essential and non-essential element distribution in leaves of the Cd/Zn hyperaccumulator Thlaspi praecox as revealed by micro-PIXE.

    PubMed

    Vogel-Mikus, Katarina; Simcic, Jure; Pelicon, Primoz; Budnar, Milos; Kump, Peter; Necemer, Marijan; Mesjasz-Przybyłowicz, Jolanta; Przybyłowicz, Wojciech J; Regvar, Marjana

    2008-10-01

    A detailed localization of elements in leaf tissues of the field-collected Cd/Zn hyperaccumulator Thlaspi praecox (Brassicaceae) growing at a highly metal-polluted site was determined by micro-proton-induced X-ray emission (micro-PIXE) in order to reveal and compare nutrient and non-essential element accumulation patterns in the case of multiple metal accumulation within particular leaf tissues, including the detailed distribution between apoplast and symplast regions. On the larger scans, the highest concentrations of metals were observed in the epidermis, S and Ca in the palisade mesophyll, Cl in the spongy mesophyll and vascular bundles, and P and K in the vascular bundles. On the more detailed scans, the highest Cd, Pb, Cl and K concentrations were observed in vascular bundle collenchyma. The relative element distribution (%) was calculated based on concentrations of elements in particular leaf tissues and their relative weight portions, indicating that most of the accumulated Zn was located in epidermises, while the majority of Cd and Pb was distributed within the mesophyll. Detailed scans of epidermal/mesophyll tissues revealed that Zn was mainly accumulated and detoxified in the symplast of large vacuolated epidermal cells, Cd in the mesophyll symplast, and Pb in the mesophyll symplast and apoplast. PMID:18643900

  16. Effect of Zn-Cd interdiffusion on the band structure and spontaneous emission of ZnO/Zn1-xCdxO/ZnO quantum wells

    NASA Astrophysics Data System (ADS)

    Shtepliuk, I.; Khranovskyy, V.; Yakimova, R.

    2015-09-01

    Needs in more-efficient visible light sources based on quantum wells (QWs) requires the diversification of traditional optoelectronics' materials as well as development of the cost-effective approaches for reliable quantum confinement engineering. Interdiffusion approach has a great potential to become a simple method for controlling the optical properties of QWs and diminishing the quantum confined Stark effect (QCSE). In this work we theoretically study the effect of Zn-Cd interdiffusion in ZnCdO/ZnO QWs on their band structure, optical matrix elements and spontaneous emission properties. The QW intermixing leads to improving both the transverse electric (TE) and transverse magnetic (TM) optical matrix elements due to enhancement of the overlap integral between electron and hole wave functions and modification of the confinement potential from triangle-shaped to parabolic-like. The optimized diffusion length 4 Å provided by the annealing at 700 K during 60 s was determined for 2 nm-thick Zn0.85Cd0.15O QW, which offers higher spontaneous emission rate in comparison to conventional QW. The reasonable interpretation of the interdiffusion effect on the optical properties of QWs is proposed in terms of low diffusion length and high diffusion length regimes. Thus, suitable combination of annealing duration and annealing temperature with the geometrical/compositional parameters of QWs can be the efficient way for improving the optical performance of ZnO-based QWs.

  17. Carbonate-hosted nonsulphide Zn-Pb mineralization of southern British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Paradis, Suzanne; Keevil, Halley; Simandl, George J.; Raudsepp, Mati

    2015-12-01

    Many carbonate-hosted sulphide deposits in the Salmo district of southern British Columbia have near-surface Zn- and Pb-bearing iron oxide-rich gossans. The gossans formed when carbonate-hosted, base metal sulphides were subjected to intense supergene weathering processes and metals were liberated by the oxidation of sulphide minerals. Two types of supergene carbonate-hosted nonsulphide deposits, direct replacement (`red ore') and wallrock replacement (`white ore'), are present in the Salmo district. The direct replacement deposits formed by the oxidation of primary sulphides; the base metals passed into solution and were redistributed and trapped within the space occupied by the oxidized portion of the sulphide protore. Depending on the extent of replacement of the sulphides by Zn-, Pb- and Fe-bearing oxides, silicates, carbonates and phosphates, the resulting ore can be called `mixed' (sulphides and nonsulphides) or simply `nonsulphide'. The wallrock replacement deposits formed when base metals liberated by the oxidation of sulphides were transported by circulating supergene solutions down and/or away from the sulphides to form wallrock replacement deposits. The direct replacement nonsulphide zones of the Salmo district overlay the sulphide bodies in which they replaced the sulphides and carbonates, forming large irregular replacement masses, encrustations and open-space fillings. They consist predominantly of hematite, goethite, hemimorphite [Zn4Si2O7(OH)2·H2O], minor hydrozincite [Zn5(CO3)2(OH)6], cerussite [PbCO3] and traces of willemite [Zn2SiO4]. The wallrock replacement zones consist mainly of hemimorphite with local occurrences of iron oxides, hopeite [Zn3(PO4)2·4H2O] and tarbuttite [Zn2(PO4)(OH)]. No remnants of sulphides were observed in the replacement zones. The Salmo nonsulphide deposits were formed by prolonged weathering of Mississippi Valley-type (MVT) mineralization that underwent dissolution and oxidation of the pyrite, sphalerite and galena

  18. Thallium transformation and partitioning during Pb-Zn smelting and environmental implications.

    PubMed

    Liu, Juan; Wang, Jin; Chen, Yongheng; Xie, Xiaofan; Qi, Jianying; Lippold, Holger; Luo, Dinggui; Wang, Chunlin; Su, Longxiao; He, Lucheng; Wu, Qiwei

    2016-05-01

    Thallium (Tl) is a toxic and non-essential heavy metal. Raw Pb-Zn ores and solid smelting wastes from a large Pb-Zn smelting plant - a typical thallium (Tl) pollution source in South China, were investigated in terms of Tl distribution and fractionation. A modified IRMM (Institute for Reference Materials and Measurement, Europe) sequential extraction scheme was applied on the samples, in order to uncover the geochemical behavior and transformation of Tl during Pb-Zn smelting and to assess the potential environmental risk of Tl arising from this plant. Results showed that the Pb-Zn ore materials were relatively enriched with Tl (15.1-87.7 mg kg(-1)), while even higher accumulation existed in the electrostatic dust (3280-4050 mg kg(-1)) and acidic waste (13,300 mg kg(-1)). A comparison of Tl concentration and fraction distribution in different samples clearly demonstrated the significant role of the ore roasting in Tl transformation and mobilization, probably as a result of alteration/decomposition of related minerals followed by Tl release and subsequent deposition/co-precipitation on fine surface particles of the electrostatic dust and acidic waste. While only 10-30% of total Tl amounts was associated with the exchangeable/acid-extractable fraction of the Pb-Zn ore materials, up to 90% of total Tl was found in this fraction of the electrostatic dust and acidic waste. Taking into account the mobility and bioavailability of this fraction, these waste forms may pose significant environmental risk. PMID:26840520

  19. Total reflection X-ray fluorescence and energy-dispersive X-ray fluorescence analysis of runoff water and vegetation from abandoned mining of Pb Zn ores

    NASA Astrophysics Data System (ADS)

    Marques, A. F.; Queralt, I.; Carvalho, M. L.; Bordalo, M.

    2003-12-01

    The present work reports on the heavy metal content: Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd and Pb in running waters and vegetation around abandoned mining areas. Two species of mosses ( Dicranum sp. and Pleurocarpus sp.) and three different species of wild grass ( Bromus sp., Rumex sp. and Pseudoavena sp.) growing on the surrounding areas of old lead-zinc mines (Aran Valley, Pyrenees, NE Spain) have been analyzed. Both water and vegetation were collected in two different sampling places: (a) near the mine gallery water outlets and (b) on the landfill close to the abandoned mineral concentration factories. For the heavy metal content determination, two different techniques were used: total reflection X-ray fluorescence for water analysis and energy-dispersive X-ray fluorescence for vegetation study. Surface waters around mine outlets exhibit anomalous content of Co, Ni, Zn, Cd. Stream waters running on mining landfills exhibit higher Cu, Zn, Cd and Pb than those of the waters at the mine gallery outlets. The results allow us to assess the extent of the environmental impact of the mining activities on the water quality. The intake of these elements by vegetation was related with the sampling place, reflecting the metal water content and the substrate chemistry. Accumulation of metals in mosses is higher than those exhibited in wild grasses. Furthermore, different levels of accumulation were found in different wild grass. Rumex sp. presented the lowest metal concentrations, while Pseudoavena sp. reported the highest metal content.

  20. Multichannel CdZnTe gamma ray spectrometer

    NASA Astrophysics Data System (ADS)

    Doty, F. P.; Lingren, C. L.; Apotovsky, B. A.; Brunsch, J.; Butler, J. F.; Collins, T.; Conwell, R. L.; Friesenhahn, S.; Gormley, J.; Pi, B.; Zhao, S.; Augustine, F. L.; Bennett, B. A.; Cross, E.; James, R. B.

    1999-02-01

    A 3 cm 3 multichannel gamma spectrometer for DOE applications is under development by Digirad Corporation. The device is based on a position sensitive detector packaged in a compact multi-chip module (MCM) with integrated readout circuitry. The modular, multichannel design will enable identification and quantitative analysis of radionuclides in extended sources, or sources containing low levels of activity. The MCM approach has the advantages that the modules are designed for imaging applications, and the sensitivity can be arbitrarily increased by increasing the number of pixels, i.e. adding modules to the instrument. For a high sensitivity probe, the outputs for each pixel can be corrected for gain and offset variations, and summed digitally. Single pixel results obtained with discrete low noise readout indicate energy resolution of 3 keV can be approached with currently available CdZnTe. The energy resolution demonstrated to date with MCMs for 511 keV gamma rays is 10 keV.

  1. Photoresponse asymmetry of CdZnTe crystals

    SciTech Connect

    But, A. V. Mygal, V. P.; Phomin, A. S.

    2011-02-15

    It is shown that transformation of photoelectric characteristics of sensors based on Cd{sub 1-x}Zn{sub x}Te (x = 0.05-0.15) crystals into parametric spectral I({lambda})-dI/d{lambda}, kinetic I(t)-dI/dt, and dynamic U-I({Delta}y){sub f,{lambda}} signatures (I({lambda}) is the photocurrent, U is the voltage, f is the frequency, t is the time, and y is the coordinate) makes it possible to reveal integrative photoresponse features caused by the photoresponse asymmetry and nonlinearity. Indices of asymmetry and balance of dynamic and energy photoinduced states are suggested; these indices represent systematically the effect of multiscale fields on photoelectronic processes. Using these indices, the ranges of external effects at which systematic features of photoresponse of sensors are minimal or maximal are determined, which makes it possible to increase the efficiency of purposeful selection and treatment of sensors.

  2. Modelling the leaching of Pb, Cd, As, and Cr from cementitious waste using PHREEQC.

    PubMed

    Halim, Cheryl E; Short, Stephen A; Scott, Jason A; Amal, Rose; Low, Gary

    2005-10-17

    A leaching model was developed using the United States Geological Survey public domain PHREEQC geochemical package to simulate the leaching of Pb, Cd, As, and Cr from cementitious wastes. The model utilises both kinetic terms and equilibrium thermodynamics of key compounds and provides information on leachate and precipitate speciation. The model was able to predict the leaching of Pb, Cd, As, and Cr from cement in the presence of both simple (0.1 and 0.6M acetic acid) and complex municipal landfill leachates. Heavy metal complexation by the municipal landfill leachate was accounted for by the introduction of a monoprotic organic species into the model. The model indicated Pb and As were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd was seen to exist as discrete particles in the cement pores and Cr (VI) existed mostly as free CrO4(2-) ions. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. At high pH values, the concentration of As in the leachate was governed by the solubility of Ca3(AsO4)2 with the presence of carbonate alkalinity competing with arsenate for Ca ions. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution. The reduction of As and Cr in municipal landfill leachate was crucial for determining aqueous speciation, with typical municipal landfill conditions providing the reduced forms of As and Cr. PMID:16043281

  3. As-Received CdZnTe Substrate Contamination

    NASA Astrophysics Data System (ADS)

    Benson, J. D.; Bubulac, L. O.; Jaime-Vasquez, M.; Lennon, C. M.; Smith, P. J.; Jacobs, R. N.; Markunas, J. K.; Almeida, L. A.; Stoltz, A.; Arias, J. M.; Wijewarnasuriya, P. S.; Peterson, J.; Reddy, M.; Vilela, M. F.; Johnson, S. M.; Lofgreen, D. D.; Yulius, A.; Carmody, M.; Hirsch, R.; Fiala, J.; Motakef, S.

    2015-09-01

    State-of-the-art as-received (112)B CdZnTe substrates were examined for surface impurity contamination, polishing damage, and tellurium precipitates/inclusions. A maximum surface impurity concentration of Al = 7.5 × 1014, Si = 3.7 × 1013, Cl = 3.12 × 1015, S = 1.7 × 1014, P = 7.1 × 1013, Fe = 1.0 × 1013, Br = 1.9 × 1012, and Cu = 4 × 1012 atoms cm-2 was observed on an as-received 6 × 6 cm wafer. As-received CdZnTe substrates have scratches and residual polishing grit on the (112)B surface. Polishing scratches are 0.3 nm in depth and 0.1 μm wide. The polishing grit density was observed to vary from wafer-to-wafer from ˜5 × 106 to 2 × 108 cm-2. Te precipitate/inclusion size and density was determined by near-infrared automated microscopy. A Te precipitate/inclusion diameter histogram was obtained for the near-surface (top ~140 μm) of a 6 × 6 cm substrate. The average areal Te precipitate/inclusion density was observed to be fairly uniform. However, there was a large density of Te precipitates/inclusions with a diameter significantly greater than the mean. Te precipitate/inclusion density >10 μm diameter = 2.8 × 103 cm-3. The large Te precipitates/inclusions are laterally non-uniformly distributed across the wafer.

  4. [The impact of ZnS/CdS composite window layer on the quantun efficiency of CdTe solar cell in short wavelength].

    PubMed

    Zhang, Li-xiang; Feng, Liang-huan; Wang, Wen-wu; Xu, Hang; Wu, Li-li; Zhang, Jing-quan; Li, Wei; Zeng, Guang-gen

    2015-02-01

    ZnS/CdS composite window layer was prepared by magnetron sputtering method and then applied to CdTe solar cell. The morphology and structure of films were measured. The data of I-V in light and the quantum efficiency of CdTe solar cells with different window layers were also measured. The effect of ZnS films prepared in different conditions on the performance of CdTe solar cells was researched. The effects of both CdS thickness and ZnS/CdS composite layer on the transmission in short wavelength were studied. Particularly, the quantum efficiency of CdTe solar cells with ZnS/CdS window layer was measured. The results show as follows. With the thickness of CdS window layer reducing from 100 to 50 nm, the transmission increase 18.3% averagely in short wavelength and the quantum efficiency of CdTe solar cells increase 27.6% averagely. The grain size of ZnS prepared in 250 degrees C is smaller than prepared at room temperature. The performance of CdTe solar cells with ZnS/CdS window layer is much better if ZnS deposited at 250 degrees C. This indicates grain size has some effect on the electron transportation. When the CdS holds the same thickness, the transmission of ZnS/CdS window layer was improved about 2% in short wavelength compared with CdS window layer. The quantum efficiency of CdTe solar cells with ZnS/CdS window layer was also improved about 2% in short wavelength compared with that based on CdS window layer. These indicate ZnS/CdS composite window layer can increase the photon transmission in short wavelength so that more photons can be absorbed by the absorbent layer of CdTe solar cells. PMID:25970885

  5. Growth and characterization of non-linear optical crystal Cd{sub 3}Zn{sub 3}B{sub 4}O{sub 12}

    SciTech Connect

    Zhang Fan Shen Dezhong Shen Guangqiu; Wang Xiaoqing

    2008-12-01

    Cd{sub 3}Zn{sub 3}B{sub 4}O{sub 12} polycrystals were synthesized by solid-state and wet chemical reaction methods. Cd{sub 3}Zn{sub 3}B{sub 4}O{sub 12} single crystals with millimeter grade were grown from the self-flux B{sub 2}O{sub 3} (Cd:Zn:B = 1:1:1.5); and larger crystals were obtained from the PbO-0.85PbF{sub 2} fluxes easily. As-grown crystals were characterized by differential scanning calorimetry and thermogravimetric, X-ray diffraction, infrared and Raman spectral analysis, respectively. The non-linear optical coefficient of the Cd{sub 3}Zn{sub 3}B{sub 4}O{sub 12} crystal is 2.6 times as large as that of KH{sub 2}PO{sub 4} crystal. Chemical etching shows that this crystal is very stable in neutral solution and not hygroscopic in air at room temperature.

  6. Core-shell ITO/ZnO/CdS/CdTe nanowire solar cells

    SciTech Connect

    Williams, B. L.; Phillips, L.; Major, J. D.; Durose, K.; Taylor, A. A.; Mendis, B. G.; Bowen, L.

    2014-02-03

    Radial p-n junction nanowire (NW) solar cells with high densities of CdTe NWs coated with indium tin oxide (ITO)/ZnO/CdS triple shells were grown with excellent heterointerfaces. The optical reflectance of the devices was lower than for equivalent planar films by a factor of 100. The best efficiency for the NW solar cells was η = 2.49%, with current transport being dominated by recombination, and the conversion efficiencies being limited by a back contact barrier (ϕ{sub B} = 0.52 eV) and low shunt resistances (R{sub SH} < 500 Ω·cm{sup 2})

  7. Proton irradiation of MWIR HgCdTe/CdZnTe

    NASA Astrophysics Data System (ADS)

    Fahey, Stephen; Velicu, Silviu; Bommena, Ramana; Zhao, Jun; Cowan, Vincent; Morath, Christian; Sivananthan, Sivalingam

    2015-09-01

    High performance infrared sensors are vulnerable to slight changes in defect densities and locations. For example in a space application where such sensors are exposed to proton irradiation capable of generating point defects the sensors are known to suffer performance degradation. The degradation can generally be observed in terms of dark current density and responsivity degradations. Here we report results of MWIR HgCdTe/CdZnTe single element diodes dark current densities before and after exposure to 63MeV protons at room temperature to a total ionizing dose of 100 kRad(Si). We find the irradiated diodes as a group show some signs of proton-induced damage in dark current.

  8. Phonon blocking by two dimensional electron gas in polar CdTe/PbTe heterojunctions

    SciTech Connect

    Zhang, Bingpo; Cai, Chunfeng; Zhu, He; Wu, Feifei; Ye, Zhenyu; Chen, Yongyue; Li, Ruifeng; Kong, Weiguang; Wu, Huizhen

    2014-04-21

    Narrow-gap lead telluride crystal is an important thermoelectric and mid-infrared material in which phonon functionality is a critical issue to be explored. In this Letter, efficient phonon blockage by forming a polar CdTe/PbTe heterojunction is explicitly observed by Raman scattering. The unique phonon screening effect can be interpreted by recent discovery of high-density two dimensional electrons at the polar CdTe/PbTe(111) interface which paves a way for design and fabrication of thermoelectric devices.

  9. Accumulation and transport of Cd, Cu, and Pb in an estuarine salt marsh surface microlayer

    SciTech Connect

    Lion, L.W.; Leckie, J.O.

    1982-01-01

    Dissolved and particulate Cd, Cu, and Pb were measured in bulk solution and surface microlayer samples from an intertidal salt marsh in south San Francisco Bay. The phase distribution (dissolved vs. particulate) of metals was consistent with their calculated speciation in computer-simulated sea-salt matrices. Trace metal enrichment at the microlayer corresponded with physical events at the sample site. Advective exchange of Cd, Cu, and Pb between the estuary and marsh systems was dominated by transport of bulk suspended particulate metals, with an apparent net export from the marsh to the bay.

  10. The effect of Pb addition on the morphology of CdSe quantum dot

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Cho, Young-Sang; Chung, Kookchae; Choi, Chul-Jin

    2010-08-01

    CdSe quantum dots had been synthesized with a hot injection method. It was shown that the addition of Pb ions in the initial precursor solution changed the morphology of CdSe nanocrystals from slightly prolate ellipsoid to branched rod. Photoluminescence (PL) of the branched nanocrystals showed rapid depression of emission intensity due to the morphological development to the branched nanocrystal induced by Pb addition. Low temperature PL spectrum indicated that the surface recombination of charge carrier resulted in the large depression of emission from the branched nanocrystal.

  11. Classification of Broken Hill-Type Pb-Zn-Ag Deposits: A Refinement

    NASA Astrophysics Data System (ADS)

    Spry, P. G.; Teale, G. S.; Steadman, J. A.

    2009-05-01

    Broken Hill Hill-type Pb-Zn-Ag (BHT) deposits constitute some of the largest ore deposits in the world. The Broken Hill deposit is the largest accumulation of Pb, Zn, and Ag on Earth and the Cannington deposit is currently the largest silver deposit. Characteristic features of BHT deposits include: 1. high Pb+Zn+Ag values with Pb > Zn; 2. Metamorphism to amphibolite-granulite facies; 3. Paleo-to Mesoprotoerozoic clastic metasedimentary host rocks; 4. Sulfides that are spatially associated with bimodal (felsic and mafic) volcanic rocks, and stratabound gahnite- and garnet-bearing rocks and iron formations, 5. Stacked orebodies with characteristic Pb:Zn:Ag ratios and skarn-like Fe-Mn-Ca-F gangue assemblages, and the presence of Cu, Au, Bi, As, and Sb; and 6. Sulfur-poor assemblages. Broken Hill (Australia) has a prominent footwall feeder zone whereas other BHT deposits have less obvious alteration zones (footwall garnet spotting and stratabound alteration haloes). Deposits previously regarded in the literature as BHT deposits are Broken Hill, Cannington, Oonagalabie, Menninie Dam, and Pegmont (Australia), Broken Hill, Swartberg, Big Syncline, and Gamsberg (South Africa), Zinkgruvan (Sweden), Sullivan, Cottonbelt, and Foster River (Canada), and Boquira (Brazil). Of these deposits, only the Broken Hill (Australia, South Africa), Pinnacles, Cannington, Pegmont, and Swartberg deposits are BHT deposits. Another BHT deposit includes the Green Parrot deposit, Jervois Ranges (Northern Territory). The Foster River, Gamsberg, and Sullivan deposits are considered to be "SEDEX deposits with BHT affinities", and the Oonagalabie, Green Mountain (Colorado), and Zinkgruvan are "VMS deposits with BHT affinities". In the Broken Hill area (Australia), Corruga-type Pb-Zn-Ag deposits occur in calc-silicate rocks and possess some BHT characteristics; the Big Syncline, Cottonbelt, Menninie Dam, and Saxberget deposits are Corruga-type deposits. SEDEX deposits with BHT affinities, VMS

  12. Direct determination of Cd, Pb and Cr in honey by slurry sampling electrothermal atomic absorption spectrometry.

    PubMed

    de Andrade, Camila Kulek; dos Anjos, Vanessa Egéa; Felsner, Maria Lurdes; Torres, Yohandra Reyes; Quináia, Sueli Pércio

    2014-03-01

    Slurry sampling electrothermal atomic absorption spectrometry was used for direct determination of Cr, Pb and Cd in honey without sample pretreatment. The honey slurries were prepared in aqueous solution containing hydrogen peroxide and nitric acid. The slurries were directly introduced in the pyrolytic graphite tubes. Pd-Mg was used as a chemical modifier only for Cd determination. Analytical curves were performed with aqueous standards for Pb and Cr and with addition of fructose for Cd. The quantification limits for Cd, Pb and Cr were 2.0, 5.4 and 9.4ngg(-1), respectively. Acceptable precision of the methodology was obtained through repeatability and intermediate precision. In the accuracy study, recoveries were satisfactory (94-101%) for the three elements. The methodology was applied in honey from Paraná (Brazil). The concentrations of Pb, Cd and Cr ranged from 141 to 228ngg(-1), <2.0 to 8ngg(-1) and 83 to 94ngg(-1), respectively. PMID:24176328

  13. Optical Properties of CdSe/ZnS Nanocrystals

    PubMed Central

    Gaigalas, Adolfas K; DeRose, Paul; Wang, Lili; Zhang, Yu-Zhong

    2014-01-01

    Measurements are presented of the absorbance, fluorescence emission, fluorescence quantum yield, and fluorescence lifetime of CdSe/ZnS nanocrystals, also known as quantum dots (QDs). The study included three groups of nanocrystals whose surfaces were either passivated with organic molecules, modified further with carboxyl groups, or conjugated with CD14 mouse anti-human antibodies. The surface modifications had observable effects on the optical properties of the nanocrystals. The oscillator strength (OS) of the band edge transition was about 1.0 for the nanocrystals emitting at 565 nm, 605 nm, and 655 nm. The OS could not be determined for QDs with emission at 700 nm and 800 nm. The fluorescence lifetimes varied from 26 ns for nanocrystals emitting near 600 nm to 150 ns for nanocrystals emitting near 800 nm. The quantum yield ranged between 0.4 and 0.9 for the nanocrystals in this study. A brightness index (BI) was used to evaluate the suitability of the nanocrystal labels for flow cytometer measurements. Most QD labels are at least as bright as fluorescein for applications in flow cytometer assays with 488 nm excitation. For optimal brightness the QDs should be excited with 405 nm light. We observed a strong dependence of the QD absorbance at 250 nm on the surface modification of the QD. PMID:26601047

  14. Charge transfer and optical properties of wurtzite-type ZnS/(CdS/ZnS){sub n} (n = 2, 4, 8) superlattices

    SciTech Connect

    Zeng, Xianghua Zhang, Wei; Cui, Jieya; Zhou, Min; Chen, Haitao

    2014-02-01

    Graphical abstract: (a) Normalized temperature-dependent PL spectra of ZnS/(CdS/ZnS){sub 4} superlattices from 5 to 300 K and (b) schematic of charge transfer at CdS/ZnS interface. - Highlights: • Wurtzite ZnS/(CdS/ZnS){sub n} superlattices were prepared at 100 °C by pulsed laser deposition. • Surface phonon of ZnS and multiple phonons modes of ZnS and CdS were observed. • The charge transfer of electrons from CdS electron to ZnS holes by excitation energy was found. - Abstract: ZnS/(CdS/ZnS){sub n} (n = 2, 4, 8) superlattices were deposited on sapphire substrate by pulsed laser deposition (PLD) with alternate cadmium sulfide (CdS) and zinc sulfide (ZnS) crystals at 100 °C. The prepared samples with an average thickness of ∼30 nm for ZnS layer and ∼60 nm for CdS layer have a wurtzite-type structure. Surface phonon of ZnS and multiple phonons modes for ZnS and CdS were observed from Raman spectra. PL spectra show a strong green emission at ∼496 nm, two weak emission bands at ∼400 and ∼577 nm, where the emission band at 400 nm was attributed to the recombination of surface defects states to valence, the emission band at 577 nm as the recombination of Cd{sub i}–V{sub Cd} centers, and the strong emission at ∼496 nm is from the charge transfer of electrons from CdS electron to ZnS holes by excitation energy.

  15. Rujevac Sb-Pb-Zn-As polymetallic deposit, Boranja orefield, Western Serbia: native arsenic and arsenic mineralization

    NASA Astrophysics Data System (ADS)

    Radosavljević, Slobodan A.; Stojanović, Jovica N.; Radosavljević-Mihajlović, Ana S.; Vuković, Nikola S.

    2014-02-01

    Rujevac is a low-temperature hydrothermal polymetallic Sb-Pb-Zn-As vein-type ore deposit, hosted within a volcanogenic-sedimentary zone situated in the Rujevac-Crvene Stene-Brezovica Diabase-Chert Formation (DCF) of the Podrinje Metallogenic District (PMD), Serbia. It is located several kilometers SE from the Boranja contact aureole, which is an integral part of the PMD in Western Serbia. Genetically related to the Tertiary granodioritic magma, the mineral assemblages are characterized by specific features. The mineral association of this deposit consists of sulfides, Pb-Sb(As) sulfosalts, native metals, oxides, hydroxides and gangue minerals. Chemical composition of the ore is very complex, where contents of valuable metals range as follows: Sb (0.17-24.31 wt.%), Zn (0.21-6.29 wt.%), Pb (0.15-6.33 wt.%), As (0.06-1.28 wt.%), Cd (25-747 ppm), Ag (7-408 ppm), Hg (13-473 ppm), and Tl (<1-29 ppm). Electron Probe Microanalyses (EPMA) of native arsenic from both the Rujevac and Stragari deposits showed contents of As up to 98.8 and 97.1 wt.%, with impurity contents of Sb up to 1.3 and 6.6 wt.%, and Tl up to 2 and 1.3 wt.%, respectively. Rhombohedral unit-cell parameters for native arsenic from Rujevac and Stragari deposits amount to: a = 3.760(2), c = 10.555(3) Å, V = 129.23(7) Å3 and a = 3.763(1), c = 10.560(5) Å, V = 129.48(8) Å3, respectively. Mineral assemblages, deposition order and genesis of the Rujevac polymetallic deposit were also discussed in detail. Native arsenic mineralization here has been additionally compared with similar well-known global deposits.

  16. Rujevac Sb-Pb-Zn-As polymetallic deposit, Boranja orefield, Western Serbia: native arsenic and arsenic mineralization

    NASA Astrophysics Data System (ADS)

    Radosavljević, Slobodan A.; Stojanović, Jovica N.; Radosavljević-Mihajlović, Ana S.; Vuković, Nikola S.

    2013-05-01

    Rujevac is a low-temperature hydrothermal polymetallic Sb-Pb-Zn-As vein-type ore deposit, hosted within a volcanogenic-sedimentary zone situated in the Rujevac-Crvene Stene-Brezovica Diabase-Chert Formation (DCF) of the Podrinje Metallogenic District (PMD), Serbia. It is located several kilometers SE from the Boranja contact aureole, which is an integral part of the PMD in Western Serbia. Genetically related to the Tertiary granodioritic magma, the mineral assemblages are characterized by specific features. The mineral association of this deposit consists of sulfides, Pb-Sb(As) sulfosalts, native metals, oxides, hydroxides and gangue minerals. Chemical composition of the ore is very complex, where contents of valuable metals range as follows: Sb (0.17-24.31 wt.%), Zn (0.21-6.29 wt.%), Pb (0.15-6.33 wt.%), As (0.06-1.28 wt.%), Cd (25-747 ppm), Ag (7-408 ppm), Hg (13-473 ppm), and Tl (<1-29 ppm). Electron Probe Microanalyses (EPMA) of native arsenic from both the Rujevac and Stragari deposits showed contents of As up to 98.8 and 97.1 wt.%, with impurity contents of Sb up to 1.3 and 6.6 wt.%, and Tl up to 2 and 1.3 wt.%, respectively. Rhombohedral unit-cell parameters for native arsenic from Rujevac and Stragari deposits amount to: a = 3.760(2), c = 10.555(3) Å, V = 129.23(7) Å3 and a = 3.763(1), c = 10.560(5) Å, V = 129.48(8) Å3, respectively. Mineral assemblages, deposition order and genesis of the Rujevac polymetallic deposit were also discussed in detail. Native arsenic mineralization here has been additionally compared with similar well-known global deposits.

  17. Efficient Z-scheme charge separation in novel vertically aligned ZnO/CdSSe nanotrees.

    PubMed

    Li, Zhengxin; Nieto-Pescador, Jesus; Carson, Alexander J; Blake, Jolie C; Gundlach, Lars

    2016-04-01

    A new tree-like ZnO/CdSSe nanocomposite with CdSSe branches grown on ZnO nanowires prepared via a two-step chemical vapor deposition is presented. The nanotrees (NTs) are vertically aligned on a substrate. The CdSSe branches result in strong visible light absorption and form a type-II heterojunction with the ZnO stem that facilitates efficient electron transfer. A combination of photoluminescence spectroscopy and lifetime measurements indicates that the NTs are promising materials for applications that benefit from a Z-scheme charge transfer mechanism. Vertically aligned branched ZnO nanowires can provide direct electron transport pathways to substrates and allow for efficient charge separation. These advantages of nanoscale hierarchical heterostructures make ZnO/CdSSe NTs a promising semiconductor material for solar cells, and other opto-electronic devices. PMID:26894995

  18. Efficient Z-scheme charge separation in novel vertically aligned ZnO/CdSSe nanotrees

    NASA Astrophysics Data System (ADS)

    Li, Zhengxin; Nieto-Pescador, Jesus; Carson, Alexander J.; Blake, Jolie C.; Gundlach, Lars

    2016-04-01

    A new tree-like ZnO/CdSSe nanocomposite with CdSSe branches grown on ZnO nanowires prepared via a two-step chemical vapor deposition is presented. The nanotrees (NTs) are vertically aligned on a substrate. The CdSSe branches result in strong visible light absorption and form a type-II heterojunction with the ZnO stem that facilitates efficient electron transfer. A combination of photoluminescence spectroscopy and lifetime measurements indicates that the NTs are promising materials for applications that benefit from a Z-scheme charge transfer mechanism. Vertically aligned branched ZnO nanowires can provide direct electron transport pathways to substrates and allow for efficient charge separation. These advantages of nanoscale hierarchical heterostructures make ZnO/CdSSe NTs a promising semiconductor material for solar cells, and other opto-electronic devices.

  19. Low-temperature synthesis of ZnO/CdS hierarchical nanostructure for photovoltaic application.

    PubMed

    Chen, Xue-Yan; Ling, Tao; Du, Xi-Wen

    2012-09-21

    Hierarchical nanostructures involving primary wide-band-gap nanowires and secondary narrow-band-gap branches are promising for photovoltaic application due to their excellent properties for light harvesting and fast carrier transport. In the present work, we developed a low-temperature process for facile synthesis of ZnO/CdS hierarchical nanowires, where the primary ZnO nanowires were first prepared via a hydrothermal route and then the secondary single-crystal CdS tips were grown on the ZnO nanowires by electrochemical deposition. The as-grown hierarchical ZnO/CdS nanowires are superior in charge separation as well as carrier transport, thus achieving higher open circuit voltage, short circuit current and final conversion efficiency than the common coaxial nanocables with CdS nanocrystal shell on core ZnO nanowires. PMID:22743779

  20. Optical engineering by the nanocomposites of ZnO-CdS/TiO2

    NASA Astrophysics Data System (ADS)

    Irimpan, Litty; Nampoori, V. P. N.; Radhakrishnan, P.

    2011-06-01

    In this article we present the bandgap engineering and spectral properties of ZnO-CdS and ZnO-TiO2 nanocomposites prepared by colloidal chemical synthesis. The optical bandgap (Eg) of the material is tunable between 2.62 and 4.12 eV. Emission peaks of ZnO-CdS change from 385 to 520 nm and those of ZnO-TiO2 change from 340 to 385 nm almost in proportion to the changes in Eg. It is possible to obtain a desired luminescence color from UV to green by simply adjusting the composition. ZnO-CdS and ZnO-TiO2 are potential nanocomposite materials for the tunable light emission.

  1. Use of cattails in treating wastewater from a Pb/Zn mine

    NASA Astrophysics Data System (ADS)

    Lan, Chongyu; Chen, Guizhu; Li, Liuchun; Wong, M. H.

    1992-01-01

    This article describes the use of a combined treatment system, which includes an aquatic treatment pond with Typha latifolia Linn. (Typhaceae) as the dominant species and a stabilization pond, to treat the wastewater from a Pn/Zn mine at Shaoguan, Guangdong Province, China. In 1983, it was noted that T. latifolia bloomed in areas affected by the wastewater emitted from the mine, hence a combined purification system was subsequently built. The influent contained high levels of total suspended solids (4635 mg/liter), chemical oxygen demand (14.5 mg/liter) as well as Pb (1.6 mg/liter) and Zn (1.9 mg/liter). The results of the effluent after treatment showed that the total suspended solids, chemical oxygen demand, Pb, and Zn had been reduced by 99%, 55%, 95%, and 80% respectively. The results of plant tissue analysis indicled that T. latifolia assimilated significant amounts of Pb and Zn, especially in the root portion. During 1986 several species of algae and fish were present in the pond, usually with a higher density in areas containing lower metal concentrations in the water.

  2. CdZnTe Background Measurements at Balloon Altitudes with PoRTIA

    NASA Technical Reports Server (NTRS)

    Parsons, A.; Barthelmy, S.; Bartlett, L.; Gehrels, N.; Naya, J.; Stahle, C. M.; Tueller, J.; Teegarden, B.

    2003-01-01

    Measurements of the CdZnTe internal background at balloon altitudes are essential to determine which physical processes make the most important background contributions. We present results from CdZnTe background measurements made by PoRTIA, a small CdZnTe balloon instrument that was flown three times in three different shielding configurations. PoRTIA was passively shielded during its first flight from Palestine, Texas and actively shielded as a piggyback instrument on the GRIS balloon experiment during its second and third flights from Alice Springs, Australia, using the thick GRIS Nal anticoincidence shield. A significant CdZnTe background reduction was achieved during the third flight with PoRTIA placed completely inside the GRIS shield and blocking crystal, and thus completely surrounded by 15 cm of Nal. A unique balloon altitude background data set is provided by CdZnTe and Ge detectors simultaneously surrounded by the same thick anticoincidence shield; the presence of a single coxial Ge detector inside the shield next to PoRTIA allowed a measurement of the ambient neutron flux inside the shield throughout the flight. These neutrons interact with the detector material to produce isomeric states of the Cd, Zn and Te nuclei that radiatively decay; calculations are presented that indicate that these decays may explain most of the fully shielded CdZnTe background.

  3. A surface complexation and ion exchange model of Pb and Cd competitive sorption on natural soils

    NASA Astrophysics Data System (ADS)

    Serrano, Susana; O'Day, Peggy A.; Vlassopoulos, Dimitri; García-González, Maria Teresa; Garrido, Fernando

    2009-02-01

    The bioavailability and fate of heavy metals in the environment are often controlled by sorption reactions on the reactive surfaces of soil minerals. We have developed a non-electrostatic equilibrium model (NEM) with both surface complexation and ion exchange reactions to describe the sorption of Pb and Cd in single- and binary-metal systems over a range of pH and metal concentration. Mineralogical and exchange properties of three different acidic soils were used to constrain surface reactions in the model and to estimate surface densities for sorption sites, rather than treating them as adjustable parameters. Soil heterogeneity was modeled with >FeOH and >SOH functional groups, representing Fe- and Al-oxyhydroxide minerals and phyllosilicate clay mineral edge sites, and two ion exchange sites (X - and Y -), representing clay mineral exchange. An optimization process was carried out using the entire experimental sorption data set to determine the binding constants for Pb and Cd surface complexation and ion exchange reactions. Modeling results showed that the adsorption of Pb and Cd was distributed between ion exchange sites at low pH values and specific adsorption sites at higher pH values, mainly associated with >FeOH sites. Modeling results confirmed the greater tendency of Cd to be retained on exchange sites compared to Pb, which had a higher affinity than Cd for specific adsorption on >FeOH sites. Lead retention on >FeOH occurred at lower pH than for Cd, suggesting that Pb sorbs to surface hydroxyl groups at pH values at which Cd interacts only with exchange sites. The results from the binary system (both Pb and Cd present) showed that Cd retained in >FeOH sites decreased significantly in the presence of Pb, while the occupancy of Pb in these sites did not change in the presence of Cd. As a consequence of this competition, Cd was shifted to ion exchange sites, where it competes with Pb and possibly Ca (from the background electrolyte). Sorption on >SOH

  4. Cross-Sectional Study of Macrodefects in MBE Dual-Band HgCdTe on CdZnTe

    NASA Astrophysics Data System (ADS)

    Reddy, M.; Lofgreen, D. D.; Jones, K. A.; Peterson, J. M.; Radford, W. A.; Benson, J. D.; Johnson, S. M.

    2013-11-01

    HgCdTe dual-band mid-wave infrared/long-wave infrared focal-plane arrays on CdZnTe are a key component in advanced electrooptic sensor applications. Molecular beam epitaxy (MBE) has been used successfully for growth of dual-band layers on larger CdZnTe substrates. However, the macrodefect density, which is known to reduce the pixel operability and its run-to-run variation, is larger when compared with layers grown on Si substrate. This paper reports the macrodefect density versus size signature of a well-optimized MBE dual-band growth and a cross-sectional study of a macrodefect that represents the most prevalent class using focused ion beam, scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The results show that the macrodefect originates from a void, which in turn is associated with a pit on the CdZnTe substrate.

  5. ZnO nanoflower-based photoelectrochemical DNAzyme sensor for the detection of Pb2+.

    PubMed

    Zhang, Bintian; Lu, Lili; Hu, Qichang; Huang, Feng; Lin, Zhang

    2014-06-15

    Lead contamination is now widespread, and exposure to lead may cause adverse effects on human beings. In this study, a photoelectrochemical sensor based on flower-like ZnO nanostructures was developed for Pb(2+) detection, using a Pb(2+)-dependent DNAzyme as the recognition unit and a double-strand DNA intercalator, Ru(bpy)2(dppz)(2+) (bpy=2,2'-bipyridine, dppz=dipyrido[3,2-a:2',3'-c] phenazine) as the photoelectrochemical signal reporter. The ZnO nanoflower was fabricated on an indium tin oxide (ITO) electrode by the convenient hydrothermal decomposition method. The morphology and photoelectrochemical property of the ZnO nanoflowers were characterized by SEM, XRD and photocurrent measurements. DNAzyme-substrate duplex was assembled on an ITO/ZnO electrode through electrostatic adsorption. In the presence of Pb(2+), RNA-cleavage activity of the DNAzyme was activated and its substrate strand was cleaved, resulting in the release of Ru(bpy)2(dppz)(2+) from the DNA film and the concomitant photocurrent decrease. The detection principle was verified by fluorescence measurements. Under the optimized conditions, a linear relationship between photocurrent and Pb(2+) concentration was obtained over the range of 0.5-20 nM, with a detection limit of 0.1 nM. Interference from other common metal ions was found negligible. Applicability of the sensor was demonstrated by analyzing lead level in human serum and Pb(2+) spiked water samples. This facile and economical sensor system showed high sensitivity and selectivity, thus can be potentially applied for on-site monitoring of lead contaminant. PMID:24508815

  6. Leaching potential of pervious concrete and immobilization of Cu, Pb and Zn using pervious concrete

    NASA Astrophysics Data System (ADS)

    Solpuker, U.; Sheets, J.; Kim, Y.; Schwartz, F. W.

    2014-06-01

    This paper investigates the leaching potential of pervious concrete and its capacity for immobilizing Cu, Pb and Zn, which are common contaminants in urban runoff. Batch experiments showed that the leachability of Cu, Pb and Zn increased when pH < 8. According to PHREEQC equilibrium modeling, the leaching of major ions and trace metals was mainly controlled by the dissolution/precipitation and surface complexation reactions, respectively. A 1-D reactive transport experiment was undertaken to better understand how pervious concrete might function to attenuate contaminant migration. A porous concrete block was sprayed with low pH water (pH = 4.3 ± 0.1) for 190 h. The effluent was highly alkaline (pH ~ 10 to 12). In the first 50 h, specific conductance and trace-metal were high but declined towards steady state values. PHREEQC modeling showed that mixing of interstitial alkaline matrix waters with capillary pore water was required in order to produce the observed water chemistry. The interstitial pore solutions seem responsible for the high pH values and relatively high concentrations of trace metals and major cations in the early stages of the experiment. Finally, pervious concrete was sprayed with a synthetic contaminated urban runoff (10 ppb Cu, Pb and Zn) with a pH of 4.3 ± 0.1 for 135 h. It was found that Pb immobilization was greater than either Cu or Zn. Zn is the most mobile among three and also has the highest variation in the observed degree of immobilization.

  7. Leaching potential of pervious concrete and immobilization of Cu, Pb and Zn using pervious concrete.

    PubMed

    Solpuker, U; Sheets, J; Kim, Y; Schwartz, F W

    2014-06-01

    This paper investigates the leaching potential of pervious concrete and its capacity for immobilizing Cu, Pb and Zn, which are common contaminants in urban runoff. Batch experiments showed that the leachability of Cu, Pb and Zn increased when pH<8. According to PHREEQC equilibrium modeling, the leaching of major ions and trace metals was mainly controlled by the dissolution/precipitation and surface complexation reactions, respectively. A 1-D reactive transport experiment was undertaken to better understand how pervious concrete might function to attenuate contaminant migration. A porous concrete block was sprayed with low pH water (pH=4.3±0.1) for 190 h. The effluent was highly alkaline (pH~10 to 12). In the first 50 h, specific conductance and trace-metal were high but declined towards steady state values. PHREEQC modeling showed that mixing of interstitial alkaline matrix waters with capillary pore water was required in order to produce the observed water chemistry. The interstitial pore solutions seem responsible for the high pH values and relatively high concentrations of trace metals and major cations in the early stages of the experiment. Finally, pervious concrete was sprayed with a synthetic contaminated urban runoff (10 ppb Cu, Pb and Zn) with a pH of 4.3±0.1 for 135 h. It was found that Pb immobilization was greater than either Cu or Zn. Zn is the most mobile among three and also has the highest variation in the observed degree of immobilization. PMID:24748027

  8. Deep electronic levels in high-pressure Bridgman Cd{sub 1-x}Zn{sub x}Te

    SciTech Connect

    Szeles, C.; Shan, Y.Y.; Lynn, K.G.; Eissler, E.E.

    1995-12-01

    The behavior of deep electronic levels was studied as a function of Zn concentration in CdZnTe crystals grown by the high-pressure Bridgman technique using thermoelectric effect spectroscopy. A significant increase of the thermal ionization energies of hole traps was observed with the increasing Zn content of the ternary compound. The effect explains the stronger hole trapping and the resulting much shorter hole lifetime usually observed in CdZnTe as compared to CdTe. The behavior also suggests increased carrier recombination and explains the strong deterioration of electron collection in detectors fabricated from CdZnTe of high Zn concentration.

  9. Binding strength-associated toxicity reduction by birnessite and hydroxyapatite in Pb and Cd contaminated sediments.

    PubMed

    Lee, Seungbae; An, Jinsung; Kim, Young-Jin; Nam, Kyoungphile

    2011-02-28

    In situ stabilization of sediment-bound heavy metals has been proposed as an alternative to ex situ treatment due to the concerns on ecosystem disturbance and remediation cost. The present study was conducted to test the performance of birnessite, hydroxyapatite, and zeolite as stabilizing agents for Pb and Cd in sediment. The heavy metal binding capacity and strength of the stabilizing agents were determined by analyzing Langmuir model parameters. The three agents showed the similar binding capacity (i.e., maximum monolayer sorption constant, K(a)) ranging from 1.13 to 3.62×10(5) mg/kg for Pb and 1.07 to 1.33×10(5) mg/kg for Cd. In contrast, binding strength (i.e., binding energy constant, b) of birnessite and hydroxyapatite was about one order higher than that of zeolite. This is further supported by five-step sequential extraction data: more than 99 and 70% of freshly spiked Pb and Cd were present as not-readily extractable fractions in birnessite and hydroxyapatite, respectively while the fractions were 17.9 and 14.1% in zeolite. Toxicity Characteristic Leaching Procedure (TCLP) test was also conducted to verify the effectiveness of the heavy metal-stabilizing ability of birnessite and hydroxyapatite. Birnessite successfully retained both Pb and Cd against the leaching solution, satisfying the TCLP extract concentration limits (i.e., 5 and 1 mg/L, respectively). However, hydroxyapatite released about 223.7 mg/L of Cd into the solution, which greatly exceeded the limit. The toxicity test with Hyalella azteca showed that their survival rate increased by 92.5-100% when birnessite or hydroxyapatite was added to Pb- or Cd-spiked sediment as a stabilizing agent. Our data demonstrate the potential use of birnessite and hydroxyapatite as an effective in situ remediation means for heavy metal-contaminated sediment with minimal risk to the aquatic ecosystem. PMID:21255927

  10. Nanoscale morphology of multilayer PbTe/CdTe heterostructures and its effect on photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Karczewski, G.; Szot, M.; Kret, S.; Kowalczyk, L.; Chusnutdinow, S.; Wojtowicz, T.; Schreyeck, S.; Brunner, K.; Schumacher, C.; Molenkamp, L. W.

    2015-03-01

    We study nanoscale morphology of PbTe/CdTe multilayer heterostuctures grown by molecular beam epitaxy on hybrid GaAs/CdTe (100) substrates. Nominally, the structures consist of 25 repetitions of subsequently deposited CdTe and PbTe layers with comparable thicknesses of 21 and 8 nm, respectively. However, the morphology of the resulting structures crucially depends on the growth temperature. The two-dimensional layered, superlattice-like character of the structures remains preserved only when grown at low substrate temperatures, such as 230 °C. The samples grown at the slightly elevated temperature of 270 °C undergo a morphological transformation to structures consisting of CdTe and PbTe pillars and columns oriented perpendicular to the substrate. Although the pillar-like objects are of various shapes and dimensions these structures exhibit exceptionally strong photoluminescence in the near infrared spectral region. At the higher growth temperature of 310 °C, PbTe and CdTe separate completely forming thick layers oriented longitudinally to the substrate plane. The observed topological transformations are driven by thermally activated atomic diffusion in the solid state phase. The solid state phase remains fully coherent during the processes. The observed topological transitions leading to the material separation in PbTe/CdTe system could be regarded as an analog of spinodal decomposition of an immiscible solid state solution and thus they can be qualitatively described by the Cahn-Hillard model as proposed by Groiss et al (2014 APL Mater. 2 012105).

  11. Study of Soil Washing for Remediation of Pb and Zn Contaminated Coastal Landfill

    NASA Astrophysics Data System (ADS)

    Park, S.; Kim, S.; Lee, M.

    2013-12-01

    As a result of analyzing the pre-treatment process of Pb, Zn in contaminated coastal landfill soil presented by Korean Soil Analysis Method, the each concentration was presented 577.00mg/kg, 3894.34mg/kg. This soil was critically contaminated with Pb and Zn because it was exceeded the Standard of soil contamination(2area: Pb-400mg/kg, Zn-600mg/kg). Soil remediation efficiency of the soil washing process for the removal of Pb and Zn was determined to be consistent with the results. The batch experiment on the several washing solutions(HCl, HNO3), washing solutions concentrations(0.1-0.8M) and the ratio of soil vs. solution for soil washing(1:3, 1:5 and 1:10) was performed. The results of experiments, washing time was appropriate in 30 minutes. The removal efficiency of soil washing increased as the ratio of soil vs. washing solution increased. But, in the case of heavy metals, the soil vs. solution for soil washing was determined as the optimal ratio of 1 : 5. Five consecutive soil washing with 0.5M of HCl and HNO3 solutions were performed. Results of experiments, in case of Pb was removed by target removal efficiency from soil on the twice washing. With in case of Zn was over on the first washing by target removal efficiency, but suggesting that twice consecutive soil washing is desirable as stability at field. Results of consecutive soil washing experiments, the removal efficiency maintained lower than 10 % after the 4th washing. From the results, demanding consecutive washing is not recommended. Results about the heavy metal contaminated soil washing experiments of the coastal landfill, in the case of HCl with more than 0.5 M of solution was performed at 1:5 of soil ratio vs. solution, 30 minutes of washing time and 2-3 consecutive soil washing. And in the case of HNO3 with 0.8 M of solution was performed various ratios of soil vs. washing solution, suggesting that 2-3 consecutive soil washing was reached to Pb and Zn target removal efficiency. Key words

  12. Development of electrodeposited ZnTe layers as window materials in ZnTe/CdTe/CdHgTe multi-layer solar cells

    SciTech Connect

    Islam, A.B.M.O. Chaure, N.B.; Wellings, J.; Tolan, G.; Dharmadasa, I.M.

    2009-02-15

    Zinc telluride (ZnTe) thin films have been deposited on glass/conducting glass substrates using a low-cost electrodeposition method. The resulting films have been characterized using various techniques in order to optimize growth parameters. X-ray diffraction (XRD) has been used to identify the phases present in the films. Photoelectrochemical (PEC) cell and optical absorption measurements have been performed to determine the electrical conductivity type, and the bandgap of the layers, respectively. It has been confirmed by XRD measurement that the deposited layers mainly consist of ZnTe phases. The PEC measurements indicate that the ZnTe layers are p-type in electrical conduction and optical absorption measurements show that their bandgap is in the range 2.10-2.20 eV. p-Type ZnTe window materials have been used in CdTe based solar cell structures, following new designs of graded bandgap multi-layer solar cells. The structures of FTO/ZnTe/CdTe/metal and FTO/ZnTe/CdTe/CdHgTe/metal have been investigated. The results are presented in this paper using observed experimental data.

  13. Effects of Pb plus Cd mixtures on toxicity, and internal electrolyte and osmotic balance in the rainbow trout (Oncorhynchus mykiss).

    PubMed

    Clemow, Yvonne H; Wilkie, Michael P

    2015-04-01

    The physiological and toxicological effects of Cd and Pb have been thoroughly studied, but relatively little work has been done to determine how mixtures of these metals affect fishes in soft (<100 μmol L(-1)Ca(2+)) slightly acidic (pH ∼6) waters typical of many lakes in the Canadian Shield and other regions. Recently, it has been suggested that acute exposure to Cd plus Pb mixtures (3h) had greater than additive effects on both Ca(2+) and Na(+) influx, which could potentially exacerbate disturbances to ion balance and result in greater toxicity in rainbow trout (Oncorhynchus mykiss). The goal of the present study was to test this hypothesis by assessing the physiological and toxicological effects of Cd plus Pb mixtures over longer time periods (3-5 days), but at relatively low, more environmentally relevant concentrations of these metals. Accordingly, toxicity and measurements of blood acid-base regulation (PaO2, pHa), hematology (Ht, Hb, MCHC, and Protein), ionic composition (body ions and plasma Ca(2+), Na(+), Cl(-), osmolality), unidirectional Na(+) fluxes and branchial Na(+)/K(+)-ATPase activity were measured in rainbow trout exposed to Cd plus Pb mixtures. Experiments on rainbow trout, implanted with dorsal aortic catheters for repetitive blood sampling, demonstrated that exposure to Pb alone (26 nmol PbL(-1)) was less toxic than Cd alone (6 nmol CdL(-1)), which was much less toxic to the fish than a Cd plus Pb mixture (7 nmol CdL(-1) plus 45 nmol PbL(-1)), which led to greater than additive 80% mortality by 5d. Both Cd and Pb inhibited Na(+) influx over 3d exposure to the metals, which was partially offset by decreases in the diffusive efflux (outflux) of Na(+) across the gill. Despite an absence of detectable effects of Pb alone on plasma ion balance, Cd plus Pb mixtures exacerbated Cd-induced reductions in plasma Ca(2+) concentration, and resulted in pronounced reductions in plasma Na(+), Cl(-), and osmolality. No effects on Na(+)/K(+)-ATPase activity

  14. The chemical fractionation and potential source identification of Cu, Zn and Cd on urban watershed.

    PubMed

    Zhang, Jin; Hua, Pei; Krebs, Peter

    2015-01-01

    This study showcases the chemical fractionation and primary source identification of Cu, Zn and Cd in road-deposited sediment. Results show that Zn and Cd were identified as easily mobilised and biologically available metals that pose high risks to the receiving aquatic environments. However, Cu was released in substantial amounts only under relatively extreme conditions. With the assistance of principal component analysis and chemical fractionation, two primary contributors to heavy metals in road-deposited sediment were tentatively identified as vehicle-related sources (especially, auto brake pad erosion for Cu and tyre debris for Zn) and atmospheric deposition (especially for Cd). PMID:26465315

  15. Photo-induced currents in CdZnTe crystals as a function of illumination wavelength

    NASA Astrophysics Data System (ADS)

    Teague, L. C.; L, Washington A., II; Duff, M. C.; Groza, M.; Buliga, V.; Burger, A.

    2012-03-01

    We report variations in the currents of CdZnTe semiconductor crystals during exposure to a series of light emitting diodes of various wavelengths ranging from 470 to 950 nm. The changes in the steady-state current of one CdZnTe crystal with and without illumination along with the time dependence of the illumination effects are discussed. Analysis of the de-trapping and transient bulk currents during and after optical excitation yield insight into the behaviour of charge traps within the crystal. Similar behaviour is observed for illumination of a second CdZnTe crystal suggesting that the overall illumination effects are not crystal dependent.

  16. Removal of Cd, Cr, and Pb from aqueous solution by unmodified and modified agricultural wastes.

    PubMed

    Mahmood-Ul-Hassan, Muhammad; Suthor, Vishandas; Rafique, Ejaz; Yasin, Muhammad

    2015-02-01

    The adsorption of cadmium (Cd), chromium (Cr), and lead (Pb), widely detected in wastewater, by unmodified and modified banana stalks, corn cob, and sunflower achene was explored. The three agricultural wastes were chemically modified with sodium hydroxide (NaOH), in combination with nitric acid (HNO3) and sulfuric acid (H2SO4), in order to improve their adsorptive binding capacity. The experiments were conducted as a function of contact time and initial metal ion concentrations. Of the three waste materials, corn cob had the highest adsorptive capacity for Pb than Cr and Cd. The NaOH-modified substrates had higher adsorptive capacity than the acid modified samples. The chemical treatment invariably increased the adsorption capacity between 10 and 100 %. The Langmuir maximum sorption capacity (q m) of Pb was highest (21-60 mg g(-1) of banana, 30-57 mg g(-1) of corn cob, and 23-28 mg g(-1) of sunflower achene) and that of Cd was least (4-7 mg g(-1) of banana, 14-20 mg g(-1) of corn cob, and 11-16 mg g(-1) of sunflower achene). The q m was in the order of Pb > Cr > Cd for all the three adsorbents. The results demonstrate that the agricultural waste materials used in this study could be used to remediate water polluted with heavy metals. PMID:25626568

  17. Occurrence of toxic metals (Hg, Cd and Pb) in fresh and canned tuna: public health implications.

    PubMed

    Storelli, Maria M; Barone, Grazia; Cuttone, Giuseppe; Giungato, Daniele; Garofalo, Rita

    2010-11-01

    Hg, Pb and Cd levels in fresh and canned tuna were determined and assessed by comparing element levels in these samples with maximum permissible limits set by European legislation. The estimated weekly intakes by human consuming both fresh and canned tuna were also evaluated for possible consumer health risks. Among tested metals, Hg had the highest concentrations, followed by Pb and Cd either in fresh tuna or canned tuna. None of the tested samples surpassed the European regulatory limits fixed for Cd and Pb, whereas 8.9% of the tuna cans and 20% of fresh tuna samples exceeded standard for Hg. The size of tuna was a determining factor of Hg burden. A high intake of Hg surpassing the toxicological reference value established by WHO, was associated with consumption of larger size tuna specimens. Also canned tuna consumption with Hg concentrations higher than 1 μg kg(-1), strongly increased the consumer exposure. In contrast, Cd and Pb weekly intakes through consumption either of fresh tuna or canned tuna did not exceed the toxicological reference values established by WHO, and consequently there was no human health risk. A continuous surveillance system of Hg content in these fishery products is crucial for consumer protection. PMID:20728500

  18. CdS/ZnS nanocomposites: from mechanochemical synthesis to cytotoxicity issues.

    PubMed

    Baláž, Peter; Baláž, Matej; Dutková, Erika; Zorkovská, Anna; Kováč, Jaroslav; Hronec, Pavol; Kováč, Jaroslav; Čaplovičová, Mária; Mojžiš, Ján; Mojžišová, Gabriela; Eliyas, Alexander; Kostova, Nina G

    2016-01-01

    CdS/ZnS nanocomposites have been prepared by a two-step solid-state mechanochemical synthesis. CdS has been prepared from cadmium acetate and sodium sulfide precursors in the first step. The obtained cubic CdS (hawleyite, JCPDS 00-010-0454) was then mixed in the second step with the cubic ZnS (sphalerite, JCPDS 00-005-0566) synthesized mechanochemically from the analogous precursors. The crystallite sizes of the new type CdS/ZnS nanocomposite, calculated based on the XRD data, were 3-4 nm for both phases. The synthesized nanoparticles have been further characterized by high-resolution transmission electron microscopy (HRTEM) and micro-photoluminescence (μPL) spectroscopy. The PL emission peaks in the PL spectra are attributed to the recombination of holes/electrons in the nanocomposites occurring in depth associated with Cd, Zn vacancies and S interstitials. Their photocatalytic activity was also measured. In the photocatalytic activity tests to decolorize Methyl Orange dye aqueous solution, the process is faster and its effectivity is higher when using CdS/ZnS nanocomposite, compared to single phase CdS. Very low cytotoxic activity (high viability) of the cancer cell lines (selected as models of living cells) has been evidenced for CdS/ZnS in comparison with CdS alone. This fact is in a close relationship with Cd(II) ions dissolution tested in a physiological solution. The concentration of cadmium dissolved from CdS/ZnS nanocomposites with variable Cd:Zn ratio was 2.5-5.0 μg.mL(-1), whereas the concentration for pure CdS was much higher - 53 μg.ml(-1). The presence of ZnS in the nanocrystalline composite strongly reduced the release of cadmium into the physiological solution, which simulated the environment in the human body. The obtained CdS/ZnS quantum dots can serve as labeling media and co-agents in future anti-cancer drugs, because of their potential in theranostic applications. PMID:26478399

  19. Optical fiber amplifiers based on PbS/CdS QDs modified by polymers.

    PubMed

    Sun, Xiaolan; Xie, Libin; Zhou, Wei; Pang, Fufei; Wang, Tingyun; Kost, Alan R; An, Zesheng

    2013-04-01

    Optical fiber amplifiers based on PbS/CdS semiconductor quantum dots (QDs) modified by an amphiphilic polymer were demonstrated. Well-defined QDs and an amphiphilic copolymer were first prepared and the amphiphilic copolymer was then used to disperse the QDs into silica sol to allow uniform and reproducible incorporation of QDs into the silica coating of the optical fibers. QD-doped silica sol was deposited on the fusion tapered fiber coupler via dip-coating. A 1550 nm semiconductor light emitting diode as the signal source and a 980 nm laser diode as the pump source were injected into the fiber coupler simultaneously. Through evanescent wave excitation, a signal gain as high as 8 dB was obtained within the wavelength range between 1450 and 1650 nm. In addition, the optical fiber amplifiers based on PbS/CdS QDs showed enhanced thermal stability when compared to amplifiers based on PbS QDs. PMID:23571911

  20. Numerical study of the influence of ZnTe thickness on CdS/ZnTe solar cell performance

    NASA Astrophysics Data System (ADS)

    Skhouni, Othmane; El Manouni, Ahmed; Mari, Bernabe; Ullah, Hanif

    2016-05-01

    At present most of II-VI semiconductor based solar cells use the CdTe material as an absorber film. The simulation of its performance is realized by means of various numerical modelling programs. We have modelled a solar cell based on zinc telluride (ZnTe) thin film as absorber in substitution to the CdTe material, which contains the cadmium element known by its toxicity. The performance of such photovoltaic device has been numerically simulated and the thickness of the absorber layer has been optimized to give the optimal conversion efficiency. A photovoltaic device consisting of a ZnTe layer as absorber, CdS as the buffer layer and ZnO as a window layer was modelled through Solar Cell Capacitance Simulator Software. Dark and illuminated I-V characteristics and the results for different output parameters of ZnO/CdS/ZnTe solar cell were analyzed. The effect of ZnTe absorber thickness on different main working parameters such as: open-circuit voltage Voc, short-circuit current density Jsc, fill factor FF, photovoltaic conversion efficiency η was intensely studied in order to optimize ZnTe film thickness. This study reveals that increasing the thickness of ZnTe absorber layer results in higher efficiency until a maximum value and then decreases slightly. This maximum was found to be 10% at ZnTe optimum thickness close to 2 µm. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  1. Impact of Tellurium Precipitates in CdZnTe Substrates on MBE HgCdTe Deposition

    NASA Astrophysics Data System (ADS)

    Benson, J. D.; Bubulac, L. O.; Smith, P. J.; Jacobs, R. N.; Markunas, J. K.; Jaime-Vasquez, M.; Almeida, L. A.; Stoltz, A.; Wijewarnasuriya, P. S.; Brill, G.; Chen, Y.; Peterson, J.; Reddy, M.; Vilela, M. F.; Johnson, S. M.; Lofgreen, D. D.; Yulius, A.; Bostrup, G.; Carmody, M.; Lee, D.; Couture, S.

    2014-11-01

    State-of-the-art (112)B CdZnTe substrates were examined for near-surface tellurium precipitate-related defects. The Te precipitate density was observed to be fairly uniform throughout the bulk of the wafer, including the near-surface region. After a molecular beam epitaxy (MBE) preparation etch, exposed Te precipitates, small pits, and bumps on the (112)B surface of the CdZnTe wafer were observed. From near-infrared and dark field microscopy, the bumps and small pits on the CdZnTe surface are associated with strings of Te precipitates. Raised bumps are Te precipitates near the surface of the (112)B CdZnTe where the MBE preparation etch has not yet exposed the Te precipitate(s). An exposed Te precipitate sticking above the etched CdZnTe surface plane occurs when the MBE preparation etch rapidly undercuts a Te precipitate. Shallow surface pits are formed when the Te precipitate is completely undercut from the surrounding (112)B surface plane. The Te precipitate that was previously located at the center of the pit is liberated by the MBE preparation etch process.

  2. Temperature dependence of surface and structure properties of ZnCdO film

    NASA Astrophysics Data System (ADS)

    Lei, Hong-Wen; Yan, Da-Wei; Zhang, Hong; Wang, Xue-Min; Yao, Gang; Wu, Wei-Dong; Zhao, Yan

    2014-12-01

    Zn1-xCdxO films are grown on c-sapphire substrates by laser molecular beam epitaxy (LMBE) at different temperatures. Their crystallographic structures, compositions, surface electronic structures are investigated. The a-axis lattice constant of Zn0.95Cd0.05O is 3.20 Å. Moreover, the epitaxial relationship shows a 30°-in-plane rotation of the film with respect to the c-sapphire substrate. When the substrate temperatures arrives at 500°C, the in situ reflection high-energy electron diffraction (RHEED) pattern of ZnCdO film shows sharp streaky pattern. The maximum Cd content of ZnCdO film grown at low substrate temperatures increases up to about 29.6 at.%, which is close to that of the ceramic target. In situ ultraviolet photoelectron spectroscopy (UPS) measurements demonstrate that ZnCdO film exhibits intense peaks at 4.7 eV and 10.7 eV below the Fermi level, which are assigned to the O 2p and Zn 3p states. Energetic distance between Zn 3d and Cd 4d is 0.60 eV. Above 470 nm, the thin film shows excellent optical transmission.

  3. Dual emission in asymmetric ``giant'' PbS/CdS/CdS core/shell/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Zhao, Haiguang; Sirigu, Gianluca; Parisini, Andrea; Camellini, Andrea; Nicotra, Giuseppe; Rosei, Federico; Morandi, Vittorio; Zavelani-Rossi, Margherita; Vomiero, Alberto

    2016-02-01

    Semiconducting nanocrystals optically active in the infrared region of the electromagnetic spectrum enable exciting avenues in fundamental research and novel applications compatible with the infrared transparency windows of biosystems such as chemical and biological optical sensing, including nanoscale thermometry. In this context, quantum dots (QDs) with double color emission may represent ultra-accurate and self-calibrating nanosystems. We present the synthesis of giant core/shell/shell asymmetric QDs having a PbS/CdS zinc blende (Zb)/CdS wurtzite (Wz) structure with double color emission close to the near-infrared (NIR) region. We show that the double emission depends on the excitation condition and analyze the electron-hole distribution responsible for the independent and simultaneous radiative exciton recombination in the PbS core and in the CdS Wz shell, respectively. These results highlight the importance of the driving force leading to preferential crystal growth in asymmetric QDs, and provide a pathway for the rational control of the synthesis of double color emitting giant QDs, leading to the effective exploitation of visible/NIR transparency windows.Semiconducting nanocrystals optically active in the infrared region of the electromagnetic spectrum enable exciting avenues in fundamental research and novel applications compatible with the infrared transparency windows of biosystems such as chemical and biological optical sensing, including nanoscale thermometry. In this context, quantum dots (QDs) with double color emission may represent ultra-accurate and self-calibrating nanosystems. We present the synthesis of giant core/shell/shell asymmetric QDs having a PbS/CdS zinc blende (Zb)/CdS wurtzite (Wz) structure with double color emission close to the near-infrared (NIR) region. We show that the double emission depends on the excitation condition and analyze the electron-hole distribution responsible for the independent and simultaneous radiative exciton

  4. Possible Mesozoic age of Ellenville Zn-Pb-Cu(Ag) deposit, Shawangunk Mountains, New York

    USGS Publications Warehouse

    Friedman, J.D.; Conrad, J.E.; McKee, E.H.; Mutschler, F.E.; Zartman, R.E.

    1994-01-01

    Ore textures, epithermal open-space filling of Permian structures of the Alleghanian orogeny, and largely postorogenic mineralization of the Ellenville, New York, composite Zn-Pb-Cu(Ag) vein system, provide permissive evidence for post-Permian mineralization. Isochron ages determined by 40Ar/39Ar laser-fusion techniques for K-bearing liquid inclusions in main-stage quartz from the Ellenville deposit additionally suggest a Mesozoic time of mineralization, associated with extensional formation of the Newark basin. The best 40Ar/39Ar total-fusion age range is 165 ?? 30 to 193 ?? 35 Ma. The Mesozoic 40Ar/39Ar age agrees with that of many other dated northern Appalachian Zn-Pb-Cu(Ag) deposits with near-matching lead isotope ratios, and adds new evidence of Jurassic tectonism and mineralization as an overprint to Late Paleozoic tectonism at least as far north as Ellenville (lat. 41??43???N). ?? 1994 Springer-Verlag.

  5. The Adsorption and Desorption of Pb(2+) and Cd(2+) in Freeze-Thaw Treated Soils.

    PubMed

    Li, Linhui; Ma, Jincai; Xu, Meng; Li, Xu; Tao, Jiahui; Wang, Guanzhu; Yu, Jitong; Guo, Ping

    2016-01-01

    Adsorption and desorption are important processes that influence the potential toxicity and bioavailability of heavy metals in soils. However, information regarding adsorption and desorption behavior of heavy metals in soils subjected to freeze-thaw cycles is poorly understood. In the current study, the effect of freeze-thaw cycles with different freezing temperature (-15, -25, -35°C) on soil properties was investigated. Then the adsorption and desorption behavior of Pb(2+) and Cd(2+) in freeze-thaw treated soils was studied. The adsorption amounts of Pb(2+) and Cd(2+) in freeze-thaw treated soils were smaller than those in unfrozen soils (p < 0.05), due to the fact that pH, cation exchange capacity, organic matter content, free iron oxide content, and CaCO3 content in freeze-thaw treated soils were smaller than those in unfrozen soils. The adsorption amounts of Pb(2+) and Cd(2+) in soils treated with lower freezing temperatures were higher than those in soils treated with higher freezing temperatures. Desorption percentages of Pb(2+) and Cd(2+) in unfrozen soils were smaller than those in freeze-thaw treated soils (p < 0.05). The desorption percentages of Pb(2+) and Cd(2+) were smaller in soils treated with lower freezing temperatures than those in soils treated with higher freezing temperatures. The results obtained highlight the change of the adsorption and desorption behavior of typical heavy metals in freeze-thaw treated soils located in seasonal frozen soils zone in northeast China. PMID:26644028

  6. Thickness-Dependent Charge Carrier Dynamics in CdSe/ZnSe/CdS Core/Barrier/Shell Nanoheterostructures.

    PubMed

    Yadav, Sushma; Chowdhury, Apurba; Sapra, Sameer

    2016-03-01

    We report the synthesis of CdSe/ZnSe/CdS heterostructures composed of type I and type II band alignments, where ZnSe acts as a barrier for charge carriers between the CdSe core and the CdS shell as well as being an active component of the type I (CdSe/ZnSe) and type II (ZnSe/CdS) structure simultaneously. We investigated the effect of the thickness of the barrier and the shell on the charge carrier dynamics by using UV/Vis absorbance, photoluminescence (PL), and time-resolved fluorescence techniques. The experimental data are supported by simple theoretical calculations based on effective mass approximation (EMA). PL results indicate the emission from both type I and type II structures. Time-resolved fluorescence studies show that the lifetime of the core emission decreases with increasing barrier width, owing to a greater confinement of the exciton to the core, whereas it increases with shell width because of the tunneling of charge carriers, primarily electrons, delaying the recombination of the exciton. The lifetime of the shell emission decreases with shell width as well as barrier width and height, with a larger effect being observed for the barrier width and negligible for the associated changes in the barrier height. PMID:26511899

  7. Stability Assessment on a 3% Bilayer PbS/ZnO Quantum Dot Heterojunction Solar Cell

    SciTech Connect

    Luther, Joseph M; Gao, Jianbo; Lloyd, Matthew T.; Semonin, Octavi Escala; Beard, Matthew C; Nozik, Arthur J

    2010-08-20

    We provide the first NREL-certified efficiency measurement on an all-inorganic, solution-processed, nanocrystal solar cell. The 3% efficient device is composed of ZnO nanocrystals and 1.3 eV PbS quantum dots with gold as the top contact. This configuration yields a stable device, retaining 95% of the starting efficiency after a 1000-hour light soak in air without encapsulation.

  8. Uptake and toxicity of Cd, Cu and Pb mixtures in the isopod Asellus aquaticus from waterborne exposure.

    PubMed

    Van Ginneken, M; De Jonge, M; Bervoets, L; Blust, R

    2015-12-15

    The present study evaluated interactions of waterborne Cd, Cu and Pb mixtures on metal uptake rates in the isopod Asellus aquaticus and related this to mixture effects on toxicity. Secondly, it was assessed whether observed mixture effects were better related to isopod body concentrations compared to exposure concentrations. Isopods were exposed for 10 days to single, binary and tertiary mixtures including five different concentrations of Cd (0.107 to 277 μg L(-1)), Cu (3.35 to 2117 μg L(-1)) and Pb (0.782 to 443 μg L(-1)). Mortality was assessed every day while isopod body concentrations, growth (biomass) and energy reserves (glycogen, lipid and protein reserves) were assessed at the end of the experiment. Synergistic interactions of combined Cd and Pb exposure on Cd and Pb uptake as well as on growth rates and mortality rates were observed. Mixture effects of combined Cd and Pb exposure on toxicity endpoints were directly related to increased Cd uptake in the Cd+Pb treatment. No mixture interactions of Cu on Cd or Pb uptake (and vice versa), nor on toxicity endpoints were observed. All toxicity endpoints were related to body concentrations. However, mixture effects disappeared when growth and mortality rates were expressed on body concentrations instead of exposure concentrations. By combining information of mixture effects on metal uptake with mixture toxicity data, the present study provides more insight in the way metal mixtures interfere with aquatic organisms and how they can induce toxic effects. PMID:26282750

  9. Fast evolution of tropospheric Pb- and Zn-rich particles in the vicinity of a lead smelter

    NASA Astrophysics Data System (ADS)

    Choël, M.; Deboudt, K.; Flament, P.; Lecornet, G.; Perdrix, E.; Sobanska, S.

    Dusts collected on air filters at a Pb-Zn refinery located in northern France were sampled in 1997, 1999 and 2002. The low temporal variability in major elements (Pb, Zn and S) abundances suggested chemical composition of particulate emissions was stable over time. In July 2001 and March 2002, atmospheric aerosols were sampled in the vicinity of the Pb-Zn refinery upwind and downwind from the smelters. Bulk concentrations of major elements (Al, Fe, Pb and Zn) and hydrosoluble ions (Na +, NH 4+, Mg 2+, K +, Ca 2+, Cl - NO 3- and SO 42-) were, respectively, determined by atomic absorption spectrometry and ion chromatography. Elemental and molecular individual particle analyses were, respectively, performed by automated SEM-EDX and Raman microspectrometry. Continental air masses (campaign 2001) were characterized by low Na + and high SO 42-, NO 3- and NH 4+ contents upwind from the smelters. Individual particle analysis of Pb- and Zn-rich airborne particles collected downwind from the refinery indicated elemental associations and molecular speciation were similar to those obtained at the emission: Pb compounds were mainly identified as oxides, sulfates and oxy-sulfates whereas Zn compounds were identified as sulfides. Marine air masses (campaign 2002) were characterized by high Na + contents upwind from the smelters. Individual particle analysis of Pb- and Zn-rich particles collected downwind from the refinery pointed out a systematic association with Na, not emitted by the refinery, suggesting internal mixing of marine aerosols with heavy-metals dusts emitted by the refinery. Such fast evolution of airborne particles chemical composition in the vicinity of the refinery was further proven by SEM-EDX and Raman microspectrometry mappings showing physical evolution by aggregation or coagulation of Zn- and Pb-rich particles with aged sea-salts.

  10. Interactions of aqueous Cu2+, Zn2+ and Pb2+ ions with crushed concrete fines.

    PubMed

    Coleman, Nichola J; Lee, William E; Slipper, Ian J

    2005-05-20

    The crushing of reclaimed concrete-based demolition waste to produce recycled aggregate gives rise to a large volume of cement-rich fine material for which market development would be beneficial. It was envisaged that this fine fraction may prove to be an effective sorbent for aqueous heavy metal species by virtue of its ion exchangeable phases and high pH. A batch sorption study confirmed that crushed concrete, in the particle size range 1-2 mm, successfully excluded Cu2+ (35 mg g(-1)), Zn2+ (33 mg g(-1)) and Pb2+ (37 mg g(-1)) from aqueous media. Subsequent distilled water leaching of the metal-laden concrete particles indicated that 1.9, 0.9 and 0.2% of the bound metals, Cu2+, Zn2+ and Pb2+, respectively, were readily soluble. Scanning electron microscopy revealed that the removal of Cu2+ and Zn2+ arose from surface precipitation reactions, whereas, the principal mechanism of uptake of Pb2+ was found to be by diffusion into the cement matrix. The metal ion removal efficiency of crushed concrete fines is compared with those of other low cost sorbents and potential applications which may exploit this sorptive property are also discussed. PMID:15885423

  11. Reactive flow models of the Anarraaq Zn-Pb-Ag deposit, Red Dog district, Alaska

    USGS Publications Warehouse

    Schardt, C.; Garven, G.; Kelley, K.D.; Leach, D.L.

    2008-01-01

    The Red Dog ore deposit district in the Brooks Range of northern Alaska is host to several high-grade, shale-hosted Zn + Pb deposits. Due to the complex history and deformation of these ore deposits, the geological and hydrological conditions at the time of formation are poorly understood. Using geological observations and fluid inclusion data as constraints, numerical heat and fluid flow simulations of the Anarraaq ore deposit environment and coupled reactive flow simulations of a section of the ore body were conducted to gain more insight into the conditions of ore body formation. Results suggest that the ore body and associated base metal zonation may have formed by the mixing of oxidized, saline, metal-bearing hydrothermal fluids (<200??C) with reducing, HS-rich pore fluids within radiolarite-rich host rocks. Sphalerite and galena concentrations and base metal sulfide distribution are primarily controlled by the nature of the pore fluids, i.e., the extent and duration of the HS- source. Forward modeling results also predict the distribution of pyrite and quartz in agreement with field observations and indicate a reaction front moving from the initial mixing interface into the radiolarite rocks. Heuristic mass calculations suggest that ore grades and base metal accumulation comparable to those found in the field (18% Zn, 5% Pb) are predicted to be reached after about 0.3 My for initial conditions (30 ppm Zn, 3 ppm Pb; 20% deposition efficiency). ?? Springer-Verlag 2008.

  12. Determination of Zn, Pb, Cu, and Hg in soils of Ekpan, Nigeria

    SciTech Connect

    Omgbu, J.A.; Kokogho, M.A. )

    1993-01-01

    The concentrations of zinc, lead, copper, and mercury in solids in Ekpan were determined in order to assess the impact of petroleum-refining activities. Twenty soil samples were collected 100 m apart (10 topsoils 0 to 15 cm and 10 bottom soils 15 to 30 cm). Sample solutions prepared were analyzed using the atomic absorption spectrophotometry technique. Results show that top-soil samples contain as much as 7.13 to 13.10 [mu]g/g Zn, 55.13 to 65.50 [mu]g/g Pb, 3.47 to 5.27 [mu]g/g Cu, and 4.00 to 6.50 [mu]g.g Hg. Bottom soil samples contain as much as 7.17 to 13.77 [mu]g/g Zn, 54.97 to 63.23 [mu]g/g Pb, 3.57 to 6.50 [mu]/g Cu, and 4.57 to 6.63 [mu]g/g Hg. The levels reported had an abundance ratio in the order Pb > Zn > Hg > Cu in the soil samples. It is recommended that appropriate measures be put in place by the companies to treat waste effluent before discharging them to the immediate environment. 8 refs., 2 tabs.

  13. Fractal structures in two-metal electrodeposition systems I: Pb and Zn

    SciTech Connect

    Nakouzi, Elias; Sultan, Rabih

    2011-12-15

    Pattern formation in two-metal electrochemical deposition has been scarcely explored in the chemical literature. In this paper, we report new experiments on zinc-lead fractal co-deposition. Electrodeposits are grown in special cells at a fixed large value of the zinc ion concentration, while that of the lead ion is increased gradually. A very wide diversity of morphologies are obtained and classified. Most of the deposited domains are almost exclusively Pb or Zn. But certain regions originating at the base cathode, ranging from a short grass alley to dense, grown-up bushes or shrubs, manifest a combined Pb-Zn composition. Composition is determined using scanning electron microscopy/energy dispersive x ray measurements as well atomic absorption spectroscopy. Pb domains are characterized by shiny leaf-like and dense deposits as well as flowers with round, balloon-like corollas. The Zn zones display a greater variety of morphologies such as thick trunks and thin and fine branching, in addition to minute ''cigar flower'' structures. The various morphologies are analyzed and classified from the viewpoint of fractal nature, characterized by the box-count fractal dimension. Finally, macroscopic spatial alternation between two different characteristic morphologies is observed under certain conditions.

  14. Unseeded growth of CdZnTe:In by THM technique

    NASA Astrophysics Data System (ADS)

    Roy, Utpal N.; Weiller, Stephen; Stein, Juergen; Gueorguiev, Andrey

    2009-08-01

    Travelling heater method (THM) has been a great success lately for the growth of large CdZnTe crystals. In this presentation, indium doped CdZnTe crystals have been grown adapting travelling heater method (THM) in vertical configuration, using three zone custom designed muffle furnace. Crystals have been grown with different ampoule diameter and size to study the grain growth. Seedless single crystalline CdZnTe:In crystals have been gown with 4 cm diameter weighing about 650 grams. Crystals have been characterized by near IR imaging, both microscopic and full wafer. The average resistivity along the length of the ingot was found to be about 109 ohm-cm. A resolution 3.2% was obtained at 662 keV. The effect of annealing of the whole wafer in Cd-Zn alloyed vapor on the resistivity and on the Te precipitations will be discussed.

  15. Photoluminescence spectra of CdSe/ZnS quantum dots in solution.

    PubMed

    Ibnaouf, K H; Prasad, Saradh; Hamdan, A; Alsalhi, M; Aldwayyan, A S; Zaman, M B; Masilamani, V

    2014-01-01

    The spectral properties of CdSe/ZnS core-shell quantum dots (QDs) of 3 nm size have been studied under different organic solvents, concentrations and temperatures. Our results showed that the absorption spectra of CdSe/ZnS in benzene have two humps; one around 420 nm and another at 525 nm, with a steady increase in absorption along UV region, and the absorption spectral profile under a wide range of concentrations did not change. On the other hand, the photoluminescence (PL) spectra of CdSe/ZnS in benzene showed two bands one around 375 nm and the other around 550 nm. It could be seen that the band at 375 nm is due to the interaction between the shell (ZnS) with the solvent species in high excited state, and the band at 550 nm is due to core alone (CdSe). PMID:24270709

  16. Synthesis, characterization and studies on optical properties of hierarchical ZnO–CdS nanocomposites

    SciTech Connect

    Sharma, Manu; Jeevanandam, P.

    2012-07-15

    Highlights: ► Hierarchical ZnO–CdS nanocomposites have been synthesized by a simple solution based method at room temperature. ► The optical properties of the nanocomposites depend on the structures. ► The band gap of the ZnO–CdS nanocomposites is tunable. -- Abstract: Cadmium sulfide coated zinc oxide hierarchical nanocomposites have been synthesised at room temperature by a simple solution based method. CdS nanoparticles were deposited on the surface of ZnO without using any surfactant, ligand or chelating agents. The nanocomposites were synthesised using different concentrations of thioacetamide, cadmium salts, and also by varying the reaction time. After characterization of the nanocomposites, optical properties were investigated by UV–visible diffuse reflectance and photoluminescence spectroscopy techniques. It was found that band gap of the ZnO–CdS nanocomposites is tunable between 2.42 and 3.17 eV.

  17. First-Principles Study on Cd Doping in Cu2ZnSnS4 and Cu2ZnSnSe4

    NASA Astrophysics Data System (ADS)

    Maeda, Tsuyoshi; Nakamura, Satoshi; Wada, Takahiro

    2012-10-01

    To quantitatively evaluate the substitution energies of Cd atom for Cu, Zn, or Sn atom in indium-free photovoltaic semiconductors Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe), first-principles pseudopotential calculations using plane-wave basis functions were performed. The substitution energies of Cd atom in kesterite-type CZTS and CZTSe were calculated in consideration of the atomic chemical potentials of the constituent elements of Cu, Zn, Sn, and the doping atom of Cd. During the chemical bath deposition (CBD) of the CdS layer on the CZTS or CZTSe layer, Cu, Zn, and Cd atoms dissolved in the ammonia aqueous solution and formed [Cu(NH3)2]+, [Zn(NH3)4]2+, and [Cd(NH3)4]2+ complex ions. Therefore, the chemical potentials of Cu, Zn, and Cd atoms in [Cu(NH3)2]+, [Zn(NH3)4]2+, and [Cd(NH3)4]2+ complex ions were calculated. We found that the substitution energies of n-type CdCu and charge-neutral CdZn in CZTS and CZTSe are smaller than that of p-type CdSn. The substitution energies of CdCu in CZTS and CZTSe are smaller than that in chalcopyrite-type CuInSe2 (CIS). However, the substitution energies of CdCu, CdZn, and CdSn are positive values. The formation energy of charge-neutral Cd doping with the Cu vacancy (CdCu + VCu) pair is a negative value and greatly smaller than those of donor-type CdCu and neutral CdZn in CZTS and CZTSe. These results indicate that the charge-neutral (CdCu + VCu) vacancy pair is easily formed during the CBD of the CdS layer on the CZTS or CZTSe layer. A small amount of n-type CdCu and neutral CdZn would also be formed.

  18. RF Sputtered ZnTe:N as CdS/CdTe Solar Cell Back-Contact Material

    NASA Astrophysics Data System (ADS)

    Ma, X.

    1999-04-01

    The most frequently used electrical contact to CdTe thin-film polycrystalline solar cells on glass involves the use of copper. However, Cu is known to be a fast diffuser in many semiconductors and is suspected of leading to some deterioration of performance of CdTe solar cells under extreme conditions. In this work we report on the development of a reactively sputtered ZnTe:N back contact on solar cells. Promising low-resistive nitrogen-doped ZnTe films were obtained. Efficiencies up to 10.8 percent were obtained for solar cells fabricated with a ZnTe:N/Au back contact scheme. Comparison of cell performances using ZnTe:N and Cu/Au back-contacts is presented.

  19. Bioaccessibility of Ba, Cu, Pb, and Zn in urban garden and orchard soils.

    PubMed

    Cai, Meifang; McBride, Murray B; Li, Kaiming

    2016-01-01

    Exposure of young children to toxic metals in urban environments is largely due to soil and dust ingestion. Soil particle size distribution and concentrations of toxic metals in different particle sizes are important risk factors in addition to bioaccessibility of these metals in the particles. Analysis of particle size distribution and metals concentrations for 13 soils, 12 sampled from urban gardens and 1 from orchard found that fine particles (<105 μm) comprised from 22 to 66% by weight of the tested soils, with Ba, Cu, Pb and Zn generally at higher concentrations in the finer particles. However, metal bioaccessibility was generally lower in finer particles, a trend most pronounced for Ba and Pb. Gastric was higher than gastrointestinal bioaccessibility for all metals except Cu. The lower bioaccessibility of Pb in urban garden soils compared to orchard soil is attributable to the higher organic matter content of the garden soils. PMID:26477581

  20. Invariant bandwidth of erbium in ZnO-PbO-tellurite glasses: Local probe/model

    SciTech Connect

    Ramamoorthy, Raj Kumar; Bhatnagar, Anil K.

    2014-04-24

    A series of [(70TeO{sub 2}−(30−x)ZnO−xPbO){sub 0.99}−(Er{sub 2}O{sub 3}){sub 0.01}; where x = 5, 10, 15 and 20] tellurite glasses, were prepared using the melt quenching technique. Crucial emission bandwidth of erbium at 1.5 μm has been derived and found to be the same for all the glasses, irrespective of PbO content. This identical bandwidth in all tellurite glasses is attributed to the presence of erbium in tellurium rich disordered environments. This result has been complemented through XANES spectra and the obtained invariant first shell of 6.5 oxygen atoms, confirm the unchanged environment in these glasses for all PbO content.

  1. Photosensitization of ZnO Crystals with Iodide-Capped PbSe Quantum Dots.

    PubMed

    King, Laurie A; Parkinson, B A

    2016-07-21

    Lead selenide (PbSe) quantum dots (QDs) are an attractive material for application in photovoltaic devices due to the ability to tune their band gap, efficient multiple exciton generation, and high extinction coefficients. However, PbSe QDs are quite unstable to oxidation in air. Recently there have been multiple studies detailing postsynthetic halide treatments to stabilize lead chalcogenide QDs. We exploit iodide-stabilized PbSe QDs in a model QD-sensitized solar cell configuration where zinc oxide (ZnO) single crystals are sensitized using cysteine as a bifunctional linker molecule. Sensitized photocurrents stable for >1 h can be measured in aqueous KI electrolyte that is usually corrosive to QDs under illumination. The spectral response of the sensitization extended out to 1700 nm, the farthest into the infrared yet observed. Hints of the existence of multiple exciton generation and collection as photocurrent, as would be expected in this system, are speculated and discussed. PMID:27398873

  2. The theoretical calculation of the phase diagram of infrared detector materials (Hg,Zn)Te and (Cd,Zn)Te

    NASA Astrophysics Data System (ADS)

    Li, Chi; Huang, Xingliang

    1989-05-01

    A technique for constructing the phase diagrams of Te-based pseudobinary IR detector materials on the basis of thermodynamics theory is described and demonstrated. The fundamental principles of the segregation-coefficient and shape-statement methods are reviewed; the computational procedure is explained; and results are presented for HgTe-ZnTe and CdTe-ZnTe. The temperatures in the diagrams are found to be within 0.6 and 15 C, respectively, of the experimentally measured values.

  3. Extended defects in as-grown CdZnTe

    SciTech Connect

    Xu, L.; Bolotnikov, A.E.; Hossain, A.; Kim, K-H.; Gul, R.; Yang, G.; Camarda, G.S.; Marchini, L.; Cui, Y.; James, R.B.; Xu, Y.; Wang, T.; Jie, W.

    2010-08-01

    We characterized samples cut from different locations in as-grown CdZnTe (CZT) ingots, using Automated Infrared (IR) Transmission Microscopy and White Beam X-ray Diffraction Topography (WBXDT), to locate and identify the extended defects in them. Our goal was to define the distribution of these defects throughout the entire ingot and their effects on detectors’ performance as revealed by the pulse-height spectrum. We found the highest- and the lowest- concentration of Te inclusions, respectively, in the head and middle part of the ingot, which could serve as guidance in selecting samples. Crystals with high concentration of Te inclusions showed high leakage current and poor performance, because the accumulated charge loss around trapping centers associated with Te inclusions distorts the internal electric field, affects the carrier transport properties inside the crystal, and finally degrades the detector’s performance. In addition, other extended defects revealed by the WBXDT measurements severely reduced the detector’s performance, since they trap large numbers of electrons, leading to a low signal for the pulse-height spectrum, or none whatsoever. Finally, we fully correlated the detector’s performance with our information on the extended defects gained from both the IR- and the WBXDT-measurements.

  4. Development of CdZnTe radiation detectors

    NASA Astrophysics Data System (ADS)

    Bolotnikov, Aleksey; Camarda, Giuseppe; Hossain, Anwar; Kim, Ki Hyun; Yang, Ge; Gul, Rubi; Cui, Yonggang; James, Ralph B.

    2011-08-01

    Cadmium Zinc Telluride (CdZnTe or CZT) is a very attractive material for room-temperature semiconductor detectors because of its wide band-gap and high atomic number. Despite these advantages, CZT still presents some material limitations and poor hole mobility. In the past decade most of the efforts developing CZT detectors focused on designing different electrode configurations, mainly to minimize the deleterious effect due to the poor hole mobility. A few different electrode geometries were designed and fabricated, such as pixelated anodes and Frisch-grid detectors developed at Brookhaven National Lab (BNL). However, crystal defects in CZT materials still limit the yield of detector-grade crystals, and, in general, dominate the detector's performance. In the past few years, our group's research extended to characterizing the CZT materials at the micro-scale, and to correlating crystal defects with the detector's performance. We built a set of unique tools for this purpose, including infrared (IR) transmission microscopy, X-ray micro-scale mapping using synchrotron light source, X-ray transmission- and reflection- topography, current deep level transient spectroscopy (I-DLTS), and photoluminescence measurements. Our most recent work on CZT detectors was directed towards detailing various crystal defects, studying the internal electrical field, and delineating the effects of thermal annealing on improving the material properties. In this paper, we report our most recent results.

  5. A Diffusive Gradient-in-Thin-Film Technique for Evaluation of the Bioavailability of Cd in Soil Contaminated with Cd and Pb

    PubMed Central

    Wang, Peifang; Wang, Teng; Yao, Yu; Wang, Chao; Liu, Cui; Yuan, Ye

    2016-01-01

    Management of heavy metal contamination requires accurate information about the distribution of bioavailable fractions, and about exchange between the solid and solution phases. In this study, we employed diffusive gradients in thin-films (DGT) and traditional chemical extraction methods (soil solution, HOAc, EDTA, CaCl2, and NaOAc) to determine the Cd bioavailability in Cd-contaminated soil with the addition of Pb. Two typical terrestrial species (wheat, Bainong AK58; maize, Zhengdan 958) were selected as the accumulation plants. The results showed that the added Pb may enhance the efficiency of Cd phytoextraction which is indicated by the increasing concentration of Cd accumulating in the plant tissues. The DGT-measured Cd concentrations and all the selected traditional extractants measured Cd concentrations all increased with increasing concentration of the addition Pb which were similar to the change trends of the accumulated Cd concentrations in plant tissues. Moreover, the Pearson regression coefficients between the different indicators obtained Cd concentrations and plants uptake Cd concentrations were further indicated significant correlations (p < 0.01). However, the values of Pearson regression coefficients showed the merits of DGT, CaCl2, and Csol over the other three methods. Consequently, the in situ measurement of DGT and the ex situ traditional methods could all reflect the inhibition effects between Cd and Pb. Due to the feature of dynamic measurements of DGT, it could be a robust tool to predict Cd bioavaiability in complex contaminated soil. PMID:27271644

  6. Purification, growth, and characterization of Zn(x)Cd(1-x)Se crystals

    NASA Technical Reports Server (NTRS)

    Silberman, E.; Burger, A.; Chen, W.; Henderson, D. O.; Morgan, S. H.; Springer, John M.; Yao, Y.

    1989-01-01

    The purification of starting materials which were used in the growth of Zn(x)Cd(1-x)Se (x = 0.2) single crystals using the traveling solution method (TSM) is reported. Up to 13 cm long single crystals and as grown resistivities of 6 x 10(exp 12) ohm/cm could be achieved. Infrared and Raman spectra of Zn(0.2)Cd(0.8)Se are also presented and discussed.

  7. Temperature dependent performance of Al/ZnCdS Schottky diode and charge transport analysis

    NASA Astrophysics Data System (ADS)

    Das, Mrinmay; Datta, Joydeep; Dey, Arka; Jana, Rajkumar; Ray, Partha Pratim

    2016-05-01

    Here we report the temperature dependent behaviour of Al/ZnCdS interface. In this regard, ZnCdS nanocomposite was synthesized by hydrothermal technique. Detailed study of schottky parameters including rectification ratio, ideality factor, series resistance and barrier height was performed. We explored the underlying charge transport phenomena through the Metal-semiconductor (MS) interface with the help of space charge limited current(SCLC) theory. A compartive analysis of carrier mobility and diffusion length was done.

  8. Reduced leakage currents of CdZnTe radiation detectors with HgTe/HgCdTe superlattice contacts

    NASA Astrophysics Data System (ADS)

    Chang, Y.; Grein, C. H.; Becker, C. R.; Huang, J.; Ghosh, S.; Aqariden, F.; Sivananthan, S.

    2012-10-01

    Room-temperature-operating CdZnTe radiation detectors have high energy resolution, linear energy response and are capable of operating in normal counting and spectroscopic modes, hence are highly desirable for medical diagnosis, nondestructive industrial evaluations, homeland security, counterterrorism inspections and nuclear proliferation detection to ensure national and international nuclear safety. HgTe/HgCdTe superlattices can be designed to selectively transport one carrier species while hindering transport of the other. Specifically, one designs a large carrier effective mass for undesired carriers in the electric field direction, which results in low carrier velocities, and yet a density of states for undesired carrier that is lower than that of a comparable bulk semiconductor, which results in low carrier concentrations, hence a low current density under an electric field. The opposite carrier species can be designed to have a large velocity and high density of states, hence producing a large current density. By employing HgTe/HgCdTe superlattices as contact layers intermediate between CdZnTe absorbers and metal contacts, leakage currents under high electric fields are reduced and improved x-ray and γ-ray detector performance is anticipated. Pixilated CdZnTe radiation detectors arrays were fabricated and characterized to evaluate the effectiveness of HgTe/HgCdTe superlattices in reducing leakage currents. Current-voltage characteristics show that HgTe/HgCdTe superlattice contact layers consistently result in significantly reduced leakage currents relative to detectors with only metal contacts.

  9. Facile synthesis of composition-tuned ZnO/Zn x Cd1- x Se nanowires for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Luo, Qiang; Wu, Zhiming; He, Jialun; Cao, Yiyan; Bhutto, Waseem Ahmed; Wang, Weiping; Zheng, Xuanli; Li, Shuping; Lin, Shengquan; Kong, Lijing; Kang, Junyong

    2015-04-01

    ZnO/Zn x Cd1- x Se coaxial nanowires (NWs) have been successfully synthesized by combining chemical vapor deposition with a facile alternant physical deposition method. The shell composition x can be precisely tuned in the whole region (0 ≤ x ≤ 1) by adjusting growth time ratio of ZnSe to CdSe. As a result, the effective bandgaps of coaxial nanowires were conveniently modified from 1.85 eV to 2.58 eV, almost covering the entire visible spectrum. It was also found that annealing treatment was in favor of forming the mixed crystal and improving crystal quality. An optimal temperature of 350°C was obtained according to our experimental results. Additionally, time resolved photo-luminescence spectra revealed the longest carrier lifetime in ZnO/CdSe coaxial nanowires. As a result, the ZnO/CdSe nanowire cell acquired the maximal conversion efficiency of 2.01%. This work shall pave a way towards facile synthesis of ternary alloys for photovoltaic applications.

  10. Facile synthesis of composition-tuned ZnO/Zn x Cd1-x Se nanowires for photovoltaic applications.

    PubMed

    Luo, Qiang; Wu, Zhiming; He, Jialun; Cao, Yiyan; Bhutto, Waseem Ahmed; Wang, Weiping; Zheng, Xuanli; Li, Shuping; Lin, Shengquan; Kong, Lijing; Kang, Junyong

    2015-01-01

    ZnO/Zn x Cd1-x Se coaxial nanowires (NWs) have been successfully synthesized by combining chemical vapor deposition with a facile alternant physical deposition method. The shell composition x can be precisely tuned in the whole region (0 ≤ x ≤ 1) by adjusting growth time ratio of ZnSe to CdSe. As a result, the effective bandgaps of coaxial nanowires were conveniently modified from 1.85 eV to 2.58 eV, almost covering the entire visible spectrum. It was also found that annealing treatment was in favor of forming the mixed crystal and improving crystal quality. An optimal temperature of 350°C was obtained according to our experimental results. Additionally, time resolved photo-luminescence spectra revealed the longest carrier lifetime in ZnO/CdSe coaxial nanowires. As a result, the ZnO/CdSe nanowire cell acquired the maximal conversion efficiency of 2.01%. This work shall pave a way towards facile synthesis of ternary alloys for photovoltaic applications. PMID:25977654

  11. Environmental geochemistry of shale-hosted Ag-Pb-Zn massive sulfide deposits in northwest Alaska: Natural background concentrations of metals in water from mineralized areas

    USGS Publications Warehouse

    Kelley, K.D.; Taylor, C.D.

    1997-01-01

    Red Dog, Lik and Drenchwater are shale-hosted stratiform Ag-Pb-Zn massive sulfide deposits in the northwestern Brooks Range. Natural background concentrations of metals in waters from the undisturbed (unmined) Drenchwater prospect and Lik deposit were compared to pre-mining baseline studies conducted at Red Dog. The primary factors affecting water chemistry are the extent of exposure of the deposits, the grade of mineralization, the presence of carbonate reeks in the section, and the proportion of Fe-sulfide in the ore. Surface water samples from the Drenchwater prospect, which has pyrite-dominant mineralization exposed in outcrop, have pH values as low as 2.8 and high dissolved concentrations of metals including as much as 95 mg 1-1 Al, 270 mg 1-1 Fe, 8 ??1-1 Cd, 10 ??1-1 Pb, and 2600 ??1-1 Zn, with As up to 26 ??g1-1. Surface waters from the Red Dog deposit prior to mining were also acidic and metal-rich, however, dissolved metal concentrations in Red Dog waters were many times greater. The higher metal concentrations in Red Dog waters reflect the high Zn grades and the abundant sphalerite, pyrite, and galena that were present in outcrop prior to mining. In contrast, despite significant mineralization at the Lik deposit, carbonate rocks in the section buffer the system, resulting in less acidic, mostly near-neutral pH values with low concentrations of most metals except Zn.

  12. Strain compensated CdSe/ZnSe/ZnCdMgSe quantum wells as building blocks for near to mid-IR intersubband devices

    NASA Astrophysics Data System (ADS)

    De Jesus, Joel; Chen, Guopeng; Hernandez-Mainet, Luis C.; Shen, Aidong; Tamargo, Maria C.

    2015-09-01

    In order to increase the conduction band offset of the ZnCdMgSe-based material system we studied the incorporation of strained CdSe layers to obtain deeper quantum wells for shorter wavelength intersubband transitions than those obtained in lattice-matched structures. Five CdSe/ZnSe/ZnCdMgSe multi-quantum wells (QW) samples grown by molecular beam epitaxy are studied in detail by transmission electron microscopy (TEM), X-ray diffraction (XRD), cw-photoluminescence (PL), and Fourier Transform Infrared (FTIR) absorption experiments. TEM and XRD results confirmed good structural quality of the samples. All the multi-QW PL energies were below the ZnCdSe lattice-matched to InP alloy bandgap (2.1 eV), which serves as first evidence of having achieved deeper quantum wells. FTIR absorptions from 3.83 to 2.56 μm were measured, shorter than those achieved by the lattice matched system. Simulations based on these results predict that absorptions as low as 2.18 μm can be obtained with these materials.

  13. Crystal orientation effects on electronic and optical properties of wurtzite ZnO/CdZnO quantum well lasers

    NASA Astrophysics Data System (ADS)

    Hebal, Hamza; Abid, Hamza

    2014-11-01

    The study of electronic and optical properties of ZnO/CdZnO quantum well (QW) structures, considering the crystal orientation dependence and Gaussian line shape function for optical gain are explored including many body effects and spontaneous-piezoelectric built-in field. Results are confronted with those for GaN-based QW structures. The effect of internal field in the c-plane oriented ZnO/CdZnO QW structure is relatively small compared to that of GaN/InGaN QW structure and thus, a larger optical gain is shown while it disappears in the a- and m-planes for both QW structures where the optical gain as a result is match larger. Energy dispersion, transition strength and the average hole effective masses are anisotropic in non-polar structures. The bandgap transition wavelength of the QW structure with a-plane orientation is smaller than that of m-plane orientation by 2 nm in ZnO/CdZnO QW while it is 10 nm in the case of GaN/InGaN QW structure.

  14. Negatively charged excitons in semimagnetic CdSe/ZnSe/ZnMnSe quantum dots

    SciTech Connect

    Brichkin, A. S. Chernenko, A. V.; Chekhovich, E. A.; Dorozhkin, P. S.; Kulakovskii, V. D.; Ivanov, S. V.; Toropov, A. A.

    2007-08-15

    Low-temperature (T = 1.6 K) photoluminescence (PL) of individual CdSe/ZnSe/ZnMnSe quantum dots (QDs) with different magnitudes of the sp-d exchange interaction between the magnetic impurity ions and charge carriers has been studied in a magnetic field up to 12 T applied in the Faraday and Voigt geometry. The magnitude of the interaction was controlled by changing the fraction ({eta}{sub e,h}) of the squared wave function of charge carriers in the semimagnetic barrier by means of variation of the nonmagnetic (ZnSe) layer thickness. It is established that the sp-d exchange interaction leads to a change in the sign of the effective hole g factor even for {eta}{sub e,h} {approx} 5%, while further increase in the interaction magnitude is accompanied by a rapid growth in the magnitude of spin splitting for both electrons and holes. The quantum yield of PL exhibits a significant decrease due to nonradiative Auger recombination with the excitation of Mn ions only for {eta}{sub e,h} {approx} 12%, while the rate of the holes spin relaxation starts growing only for still higher {eta}{sub e,h} values. In a strong magnetic field perpendicular to the sample plane, the alignment of Mn spins leads to suppression of the Auger recombination only in the excited spin state. For a small rate of the hole spin relaxation, this leads to a rather unusual result: the emission from an excited trion state predominates in strong magnetic fields.

  15. Pb(II)-promoted amide cleavage: mechanistic comparison to a Zn(II) analogue.

    PubMed

    Elton, Eric S; Zhang, Tingting; Prabhakar, Rajeev; Arif, Atta M; Berreau, Lisa M

    2013-10-01

    Two new Pb(II) complexes of the amide-appended nitrogen/sulfur epppa (N-((2-ethylthio)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) chelate ligand, [(epppa)Pb(NO3)2] (4-NO3) and [(epppa)Pb(ClO4)2] (4-ClO4), were prepared and characterized. In the solid state, 4-NO3 exhibits κ(5)-epppa chelate ligand coordination as well as the coordination of two bidentate nitrate ions. In acetonitrile, 4-NO3 is a 1:1 electrolyte with a coordinated NO3(-), whereas 4-ClO4 is a 1:2 electrolyte. Treatment of 4-ClO4 with 1 equiv Me4NOH·5H2O in CH3CN:CH3OH (3:5) results in amide methanolysis in a reaction that is akin to that previously reported for the Zn(II) analogue [(epppa)Zn](ClO4)2 (3-ClO4). (1)H NMR kinetic studies of the amide methanolysis reactions of 4-ClO4 and 3-ClO4 as a function of temperature revealed free energies of activation of 21.3 and 24.5 kcal/mol, respectively. The amide methanolysis reactions of 4-ClO4 and 3-ClO4 differ in terms of the effect of the concentration of methanol (saturation kinetics for 4-ClO4; second-order behavior for 3-ClO4), the observation of a small solvent kinetic isotope effect (SKIE) only for the reaction of the Zn(II)-containing 3-ClO4, and the properties of an initial intermediate isolated from each reaction upon treatment with Me4NOH·5H2O. These experimental results, combined with computational studies of the amide methanolysis reaction pathways of 4-ClO4 and 3-ClO4, indicate that the Zn(II)-containing 3-ClO4 initially undergoes amide deprotonation upon treatment with Me4NOH·5H2O. Subsequent amide protonation from coordinated methanol yields a structure containing a coordinated neutral amide and methoxide anion from which amide cleavage can then proceed. The rate-determining step in this pathway is either amide protonation or protonation of the leaving group. The Pb(II)-containing 4-ClO4 instead directly forms a neutral amide-containing, epppa-ligated Pb(II)-OH/Pb(II)-OCH3 equilibrium mixture upon treatment

  16. Predicting As, Cd and Pb uptake by rice and vegetables using field data from China.

    PubMed

    Zhang, Hongzhen; Luo, Yongming; Song, Jing; Zhang, Haibo; Xia, Jiaqi; Zhao, Qiguo

    2011-01-01

    Plant uptake factor (PUF), single-variable regression of natural log-transformed concentrations in rice grain/vegetables versus natural log-transformed concentrations in soil and multiple-variable regression with soil concentrations and pH, was derived, validated and compared based on the paired crop and soil data collected from studies regarding As, Cd and Pb contaminated croplands in China. Results showed that the median value of PUF did not present deterministic prediction. But after natural logarithm transformation, the PUF followed Gaussian distribution which could be useful in risk assessment. The single-variable regression models were significant for As, Cd and Pb uptake both by rice and vegetables; however, the standard errors of all the regressions were comparatively large. Soil pH as a variable was generally significant but it only contributed positively to model fit for Cd uptake. After model comparison and selection, the upper 95% prediction limits of the multiple regression model for Cd uptake by rice was recommended to calculate screening value of Cd for paddy soil based on the limit for Cd concentration in rice grain. PMID:21476343

  17. Dip coated nanocrystalline CdZnS thin films for solar cell application

    NASA Astrophysics Data System (ADS)

    Dongre, J. K.; Chaturvedi, Mahim; Patil, Yuvraj; Sharma, Sandhya; Jain, U. K.

    2015-07-01

    Nanocrystalline cadmium sulfide (CdS) and zinc cadmium sulfide (ZnCdS) thin films have been grown via simple and low cost dip coating technique. The prepared films are characterized by X-ray diffraction (XRD), atomic force microscopic (AFM) and UV-VIS spectrophotometer techniques to reveal their structural, morphological and optical properties. XRD shows that both samples grown have zinc blende structure. The grain size is calculated as 6.2 and 8 nm using Scherrer's formula. The band gap value of CdS and CdZnS film is estimated to be 2.58 and 2.69 eV respectively by UV-vis spectroscopy. Photoelectrochemical (PEC) investigations are carried out using cell configuration as n-CdZnS/(1M NaOH + 1M Na2S + 1M S)/C. The photovoltaic output characteristic is used to calculate fill-factor (FF) and solar conversion efficiency (η).

  18. Optical characterization of ZnS coated CdS nanorods embedded in liquid crystals

    NASA Astrophysics Data System (ADS)

    Roy, J. S.; Majumder, T. Pal; Dabrowski, R.

    2016-05-01

    The photoluminescence (PL) emission intensity of ZnS coated CdS nanorods, represented by CdS/ZnS system, have been enhanced in presence of liquid crystals (LC) and the enhancement strongly depends on concentration of LC. The highly light scattering liquid crystalline phase causes the enhancement in PL intensity. It is also observed that the PL intensity of CdS nanorods enhances with the coating of ZnS material. This enhancement in PL intensity is ascribed by the fact that the high optical band gap ZnS material prevents the tunneling of the charge carriers from the core CdS nanorods and passivated nonradiative recombination sites which are existed on the core surfaces. Finally, 5 fold enhancements in PL intensity of CdS nanorods have been observed by coating with ZnS material and then embedding in LC. We have also observed the red shift in emission energy band of CdS/ZnS system embedded in LC. This study will provide a possible way to develop smart optoelectronics devices.

  19. Preparation, structural and linear optical properties of Zn doped CdS nanopowders

    NASA Astrophysics Data System (ADS)

    Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.

    2015-02-01

    A series of Zn doped cadmium sulfide (CdS:Zn) nanopowders were prepared by a simple co-precipitation method at room temperature by mixing the stoichiometric amount of reactants in a Milli Q water solvent. The composition of nanopowders was accurately adjusted by controlling the molar ratio of Cd, Zn acetate in the mixed reactants. Spectroscopic studies on as prepared nanopowders were investigated by using XRD, Raman, UV-Vis absorption, FE- SEM-EDAX and photoluminescence. Extremely broad reflections of XRD peaks of as prepared powders establish the nanometer scale dimensions and cubic structure. Doping with Zn in CdS does not lead to any structural phase transformation but introduces a decrease in the lattice constants. Two characteristics of LO phonon peaks were observed in pure and Zn doped CdS samples. Raman peaks of Zn doped CdS nanopowders shifts slightly towards higher energy side compared to the pure CdS nanopowders. Exciton-phonon confinement factor (S) varies in between 0.3-0.4. At lower wavelength excitation we observed a broad emission peak maximum centered at 404 nm is attributed to localized band edge emission.

  20. The first report of Pb and Zn accumulation in some native plants from the Peruvian Andes

    NASA Astrophysics Data System (ADS)

    Bech, Jaume; Duran, Paola; Poma, Wilfredo; Sánchez, Isidoro; Barceló, Juan; Roca, Núria; Boluda, Rafael; Roca-Pérez, Luís.; Poschenrieder, Charlotte

    2010-05-01

    Until recent decades little has been known about the remediation of mining sites using metalophytes in Latin America. Metal mining has helped to create severe and diverse environmental problems. The present study proposed to identify and characterize spontaneously growing heavy metal tolerant plant species in the area around the polimetalic mine in Hualgayoc (Cajamarca, Peru). These species are potentially useful for phytorremediation. Plant and soils from their rhizosphere were sampled and analized for concentration of As, Fe, Mn, Pb and Zn. Translocation Factor (TF) defined the metals concentrations ratio between shoots and root biomass and Shoot Accumulation Factor (SAF) the metal concentration ratio between shoot and soil concentration were determined and used to measure the effectiveness of a plant in concentrating metals into its biomass. The soils were neutral pH (7,4±0,5) with variable content of organic carbon (2,4±1,1) and loam texture: sand (42,9±10,8) and clay (16,7±4,6). According to the total metals, all samples exceeded toxicity thresholds, high Pb (20016 ± 32559 mg•kg-1) and Zn (22512 ± 13056 mg•kg-1) concentrations were detected. High shoot Pb and Zn concentrations were found in Plantaginaceae Plantago orbignyana (6998 and 9617 μg/g); Brassicaceae Lepidium bipinnatifidum (6886 and 5034 mg•kg-1) and Asteraceae Senecio sp (4253 and 3870 mg•kg-1) and Baccharis latifolia (2554 and 1284 mg•kg-1 respectively). The high values of TFs indicates that the plants effectively traslocated metales. Lepidium bipinnatifidum shows the highest TFs values (143 in Pb and 21,5 in Zn). The SAF values were much lower than those reported for other species such as Paspalum sp in the Peruvian copper mine, which may be due to a high top soil Pb and Zn concentrations. These species can surely be considered as interesting for phytoextraction, due not only to its accumulative capacity but also since they showed an elevated transfer factor and grew in the

  1. Subcellular compartmentalization of Cd and Zn in two bivalves. II. Significance of trophically available metal (TAM)

    USGS Publications Warehouse

    Wallace, W.G.; Luoma, S.N.

    2003-01-01

    This paper examines how the subcellular partitioning of Cd and Zn in the bivalves Macoma balthica and Potamocorbula amurensis may affect the trophic transfer of metal to predators. Results show that the partitioning of metals to organelles, 'enzymes' and metallothioneins (MT) comprise a subcellular compartment containing trophically available metal (TAM; i.e. metal trophically available to predators), and that because this partitioning varies with species, animal size and metal, TAM is similarly influenced. Clams from San Francisco Bay, California, were exposed for 14 d to 3.5 ??g 1-1 Cd and 20.5 ??g 1-1 Zn, including 109Cd and 65Zn as radiotracers, and were used in feeding experiments with grass shrimp Palaemon macrodatylus, or used to investigate the subcellular partitioning of metal. Grass shrimp fed Cd-contaminated P. amurensis absorbed ???60% of ingested Cd, which was in accordance with the partitioning of Cd to the bivalve's TAM compartment (i.e. Cd associated with organelles, 'enzymes' and MT); a similar relationship was found in previous studies with grass shrimp fed Cd-contaminated oligochaetes. Thus, TAM may be used as a tool to predict the trophic transfer of at least Cd. Subcellular fractionation revealed that ???34% of both the Cd and Zn accumulated by M. balthica was associated with TAM, while partitioning to TAM in P. amurensis was metal-dependent (???60% for TAM-Cd%, ???73% for TAM-Zn%). The greater TAM-Cd% of P. amurensis than M. balthica is due to preferential binding of Cd to MT and 'enzymes', while enhanced TAM-Zn% of P. amurensis results from a greater binding of Zn to organelles. TAM for most species-metal combinations was size-dependent, decreasing with increased clam size. Based on field data, it is estimated that of the 2 bivalves, P. amurensis poses the greater threat of Cd exposure to predators because of higher tissue concentrations and greater partitioning as TAM; exposure of Zn to predators would be similar between these species.

  2. Formation of ZnTe:Cu/Ti Contacts at High Temperature for CdS/CdTe Devices: Preprint

    SciTech Connect

    Gessert, T. A.; Asher, S.; Johnston, S.; Duda, A.; Young, M. R.; Moriarty, T.

    2006-05-01

    We study the performance of CdS/CdTe thin-film devices contacted with ZnTe:Cu/Ti of various thickness at a higher-than-optimum temperature of {approx}360 C. At this temperature, optimum device performance requires the same thickness of ZnTe:Cu as for similar contacts formed at a lower temperature of 320 C. C-V analysis indicates that a ZnTe:Cu layer thickness of {approx}< 0.5 mu m does not yield the degree of CdTe net acceptor concentration necessary to reduce space charge width to its optimum value for n-p device operation. The thickest ZnTe:Cu layer investigated (1 mu m) yields the highest CdTe net acceptor concentration, lowest value of Jo, and highest Voc. However, performance is limited for this device by poor fill factor. We suggest poor fill factor is due to Cu-related acceptors compensating donors in CdS.

  3. Numerical analysis of CdS/PbSe room temperature mid-infrared heterojunction photovoltaic detectors

    NASA Astrophysics Data System (ADS)

    Weng, Binbin; Qiu, Jijun; Ge, Wanyin; Shi, Zhisheng

    2015-06-01

    Numerical analysis of a CdS/PbSe room-temperature heterojunction photovoltaic detector is discussed as to provide guidelines for practical improvement, based on the previous experimental exploration [1]. In our experiment work, the polycrystalline CdS film was prepared in hydro-chemical method on top of the single crystalline PbSe grown by molecular beam epitaxy method. The preliminary results demonstrated a 5.48×108 Jones peak detectivity at λ=4.7μm under zero-bias. However, the influence of some material and device parameters such as carrier concentration, interface recombination velocity remains uncertain. These parameters affect the built-in electric field and the carriers' transportation properties, and consequently could have detrimental effect on the device performance of the CdS/PbSe detector. In this work, therefore, the numerical analysis is performed based on these parameters. The simulation results suggest that the device performance can be improved at least 4 times by increasing CdS concentration for two orders of magnitudes, and the device performance will degrade severely if the interface recombination speed is over 104 cm/s.

  4. Epitaxial growth and photoluminescence excitation spectroscopy of CdSe quantum dots in (Zn,Cd)Se barrier

    NASA Astrophysics Data System (ADS)

    Piwowar, J.; Pacuski, W.; Smoleński, T.; Goryca, M.; Bogucki, A.; Golnik, A.; Nawrocki, M.; Kossacki, P.; Suffczyński, J.

    2016-05-01

    Design, epitaxial growth, and resonant spectroscopy of CdSe Quantum Dots (QDs) embedded in an innovative (Zn,Cd)Se barrier are presented. The (Zn,Cd)Se barrier enables shifting of QDs energy emission down to 1.87 eV, that is below the energy of Mn$^{2+}$ ions internal transition (2.1 eV). This opens a perspective for implementation of epitaxial CdSe QDs doped with several Mn ions as, e. g., the light sources in high quantum yield magnetooptical devices. Polarization resolved Photoluminescence Excitation measurements of individual QDs reveal sharp ($\\Gamma <$ 150 $\\mu$eV) maxima and transfer of optical polarization to QD confining charged exciton state with efficiency attaining 26 %. The QD doping with single Mn$^{2+}$ ions is achieved.

  5. Photoluminescence of localized excitons in ZnCdO thin films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, T. Y.; Huang, Y. S.; Hu, S. Y.; Lee, Y. C.; Tiong, K. K.; Chang, C. C.; Shen, J. L.; Chou, W. C.

    2016-07-01

    We have investigated the luminescence characteristics of Zn1-xCdxO thin films with different Cd contents grown by molecular beam epitaxy system. The temperature-dependent photoluminescence (PL) and excitation power-dependent PL spectra were measured to clarify the luminescence mechanisms of the Zn1-xCdxO thin films. The peak energy of the Zn1-xCdxO thin films with increasing the Cd concentration is observed as redshift and can be fitted by the quadratic function of alloy content. The broadened full-width at half-maximum (FWHM) estimated from the 15 K PL spectra as a function of Cd content shows a larger deviation between the experimental values and theoretical curve, which indicates that experimental FWHM values are affected not only by alloy compositional disorder but also by localized excitons occupying states in the tail of the density of states. The Urbach energy determined from an analysis of the lineshape of the low-energy side of the PL spectrum and the degree of localization effect estimated from the temperature-induced S-shaped PL peak position described an increasing mean exciton-localization effects in ZnCdO films with increasing the Cd content. In addition, the PL intensity and peak position as a function of excitation power are carried out to clarify the types of radiative recombination and the effects of localized exciton in the ZnCdO films with different Cd contents.

  6. CdSe/Cd(x)Zn1-xS core/shell nanocrystals: core morphology and luminescent property.

    PubMed

    Yang, Ping; Yang, Jie; Cao, Yongqiang; Ma, Qian; Zhang, Aiyu; Wang, Jianrong; Shi, Ruixia; Zhu, Yuanna

    2012-06-01

    CdSe cores with rod (an aspect ratio of 1.8, d-5 nm) and spherical (an aspect ratio of 1, d-5 nm) morphologies were fabricated by two kinds of organic approaches through adjusting growth processes. Because of large difference of size and morphology, two kinds of cores revealed different absorption spectra. However, these cores exhibited almost same photoluminescence (PL) spectra with a red-emitting PL peak of around 625 nm. This is ascribed that they have a similar size in diameter. A graded Cd(x)Zn1-xS shell of larger band gap was grown around CdSe rods and spheres using oleic acid as a capping agent. Based on the growth kinetics of CdS and ZnS, interfacial segregation was created to preferentially deposit CdS near the core, providing relaxation of the strain at the core/shell interface. For spherical CdSe cores, the homogeneous deposition of the Cd(x)Zn1-xS shell created spherical core/shell nanocrystals (NCs) with a size of 7.1 nm in diameter. In the case of using CdSe cores with rod morphology, the anisotropic aggregation behaviors of CdS monomers on CdSe rods led to the size (approximately 10 nm in diameter) of spherical CdSe/Cd(x)Zn1-xS core/shell NCs with a small difference to the length of the CdSe rod (approximately 8.9 nm). The resulting spherical core/shell NCs created by the rod and spherical cores exhibited almost same PL peak wavelength (652 and 653 nm for using rod and spherical cores, respectively), high PL efficiency up to 50%, and narrow PL spectra (36 and 28 nm of full with at half maximum of PL spectra for the core/shell NCs with CdSe spheres and rods, respectively). These core/shell NCs provide an opportunity for the study of the evolution of PL properties as the shape of semiconductor NCs. PMID:22905515

  7. Molecular interaction investigation between three CdTe:Zn(2+) quantum dots and human serum albumin: A comparative study.

    PubMed

    Huang, Shan; Qiu, Hangna; Liu, Yi; Huang, Chusheng; Sheng, Jiarong; Su, Wei; Xiao, Qi

    2015-12-01

    Water-soluble Zn-doped CdTe quantum dots (CdTe:Zn(2+) QDs) have attracted great attention in biological and biomedical applications. In particular, for any potential in vivo application, the interaction of CdTe:Zn(2+) QDs with human serum albumin (HSA) is of greatest importance. As a step toward the elucidation of the fate of CdTe:Zn(2+) QDs introduced to organism, the molecular interactions between CdTe:Zn(2+) QDs with three different sizes and HSA were systematically investigated by spectroscopic techniques. Three CdTe:Zn(2+) QDs with maximum emission of 514 nm (green QDs, GQDs), 578 nm (yellow QDs, YQDs), and 640 nm (red QDs, RQDs) were tested. The binding of CdTe:Zn(2+) QDs with HSA was a result of the formation of HSA-QDs complex and electrostatic interactions played major roles in stabilizing the complex. The Stern-Volmer quenching constant, associative binding constant, and corresponding thermodynamic parameters were calculated. The site-specific probe competitive experiments revealed that the binding location of CdTe:Zn(2+) QDs with HSA was around site I. The microenvironmental and conformational changes of HSA induced by CdTe:Zn(2+) QDs were analyzed. These results suggested that the conformational change of HSA was dramatically at secondary structure level and the biological activity of HSA was weakened in the present of CdTe:Zn(2+) QDs with bigger size. PMID:26555713

  8. Formation of ZnTe:Cu/Ti Contacts at High Temperature for CdS/CdTe Devices (Presentation)

    SciTech Connect

    Gessert, T. A.; Asher, S.; Johnston, S.; Duda, A.; Young, M. R.; Moriarty, T.

    2006-05-01

    The conclusions of this report are that Cu diffusion from a ZnTe:Cu contact causes good and bad things. The good (Cu in CdS < low 10{sup 18} cm{sup -3})--increase in CdTe N{sub A}-N{sub D} that leads to V{sub oc} and FF improvement. The bad (Cu in CdS > low 10{sup 18} cm{sup -3})--(1) possibly decreased of shunt resistance (?); (2) depletion width in CdTe can become too narrow for optimum current collection at J{sub MPP}; (3) donor reduction in CdS (significant FF loss in LIV); and (4) excessive Cu diffusion into CdS readily observed by red-light bias QE.

  9. Varying effect of biochar on Cd, Pb and As mobility in a multi-metal contaminated paddy soil.

    PubMed

    Yin, Daixia; Wang, Xin; Chen, Can; Peng, Bo; Tan, Changyin; Li, Hailong

    2016-06-01

    Cd, Pb and As stand as the most prominent contaminants prevailing in Chinese soils. In the present study, biochars derived from water hyacinth (BCW) and rice straw (BCR) were investigated regarding their applicability and durability in soil Cd, Pb, and As immobilization under acid precipitation. Total Cd, Pb, and As in both BCs were below the maximum allowed threshold according to biochar toxicity standard recommended by International Biochar Initiative. To evaluate BCs effect on Cd, Pb, As bioavailability and mobility, CaCl2, KH2PO4 and SPLP extractions were firstly carried out. In neutral extraction with CaCl2 and KH2PO4, significantly reduced Cd/Pb concentrations in CaCl2 extract along with elevated KH2PO4-extractable As were recorded with either BC at 2% or 5%. In SPLP with simulated acid rainwater as extractant, comparable Cd, Pb and As levels were determined in SPLP extract with 2% BCW, while slight to significant increase in SPLP-Cd, Pb or As was recorded with other treatments. Longer-term leaching column test further confirmed the high durability of 2% BCW in Cd immobilization under continuous acid exposure. In parallel, little increase in As concentrations in eluate was determined with 2% BCW compared to no-biochar control, indicating a lowered risk of As mobilization with acid input. However, remarkably higher Pb in leachate from both BCW-only control and 2% BCW-amended soils were noticed at the initial stage of acid leaching, indicating a higher acid-solubility of Pb minerals in BCW (most probably PbO) than in tested soil (PbO2, PbAs2O6). Taken together, BCW exhibited important potential for soil Cd sequestration with little effect on As mobilization under acid precipitation. But it may simultaneously load highly acid-soluble Pb minerals into soils, resulting in elevated Pb mobility upon acid exposure. Therefore, more stringent threshold for Pb content in biochar need to be put forward to secure biochar application in soils subject to anthropogenic

  10. Spectral analysis of Cu(2+): B(2)O(3)--ZnO--PbO glasses.

    PubMed

    Lakshminarayana, G; Buddhudu, S

    2005-11-01

    A new series of heavy metal oxide (PbO) based zinc borate glasses in the chemical composition of (95-x)B(2)O(3)-5ZnO-xPbO (x=10, 15, 20, 25, 30, 35, 40, 45 and 50 mol%) have been prepared to verify their UV filtering performance. Both direct and indirect optical band gaps (E(opt)) have been evaluated for these glasses. For a reference glass of 45B(2)O(3)-5ZnO-50PbO, refractive indices at different wavelengths are measured and found the results satisfactorily correlated with the theoretical data upon the computation of Cauchy's constants of A=1.766029949, B=159531.024 nm(2) and C=-1.078 x 10(10) nm(4). Measurements concerning X-ray diffraction (XRD), FT-IR, differential scanning colorimeter (DSC) profiles have been carried out for this glass. The FT-IR profile has revealed that the glass has both BO(3) and BO(4) units. From DSC thermogram, glass transition temperature (T(g)), crystallization temperature (T(c)) and melting temperature (T(m)) have been located and from them, other related parameters of the glass have also been calculated. Visible absorption spectra of 45B(2)O(3)-5ZnO-(50-x)PbO-xCuO (x=0. 1, 0.2, 0.5 and 1.0 mol%) have revealed two absorption bands at around 400 nm ((2)B(1g)-->(2)E(g)) and 780 nm ((2)B(1g)-->(2)B(2g)) of Cu(2+) ions, respectively. Emission bands at 422 and 512 nm are found for the 1 mol % CuO doped glass with excitations at 306 and 332 nm. PMID:16257737

  11. Structuring effect of heteroepitaxial CdHgTe/CdZnTe systems under irradiation with silver ions

    NASA Astrophysics Data System (ADS)

    Sizov, F. F.; Savkina, R. K.; Smirnov, A. B.; Udovytska, R. S.; Kladko, V. P.; Gudymenko, A. I.; Safryuk, N. V.; Lytvyn, O. S.

    2014-11-01

    The characteristics of a damaged layer of p-CdxHg1 - xTe/CdZnTe ( x ˜ 0.223) heterostructures after implantation by 100-keV silver ions with the implantation dose Q = 3.0 × 1013 cm-2 have been obtained using X-ray diffraction, atomic force microscopy, and electron microscopy. It has been found that, as a result of the ion implantation and subsequent annealing (75°C), a uniform array of nanostructures is formed on the surface of Hg(Cd)Te/Zn(Cd)Te samples. The X-ray diffraction patterns of the structurized Hg(Cd)Te/Zn(Cd)Te sample indicate the formation of polycrystalline Hg(Cd)Te phases of cubic structure with a composition x ˜ 0.20 and also oxide Ag2O in the subsurface (<100 nm) region of the host material. The observed effects of transformation of the defect-impurity system and structuring of the surface of the heteroepitaxial film of the low-energy-gap semiconductor have been explained using a deformation model.

  12. Dual emission in asymmetric "giant" PbS/CdS/CdS core/shell/shell quantum dots.

    PubMed

    Zhao, Haiguang; Sirigu, Gianluca; Parisini, Andrea; Camellini, Andrea; Nicotra, Giuseppe; Rosei, Federico; Morandi, Vittorio; Zavelani-Rossi, Margherita; Vomiero, Alberto

    2016-02-21

    Semiconducting nanocrystals optically active in the infrared region of the electromagnetic spectrum enable exciting avenues in fundamental research and novel applications compatible with the infrared transparency windows of biosystems such as chemical and biological optical sensing, including nanoscale thermometry. In this context, quantum dots (QDs) with double color emission may represent ultra-accurate and self-calibrating nanosystems. We present the synthesis of giant core/shell/shell asymmetric QDs having a PbS/CdS zinc blende (Zb)/CdS wurtzite (Wz) structure with double color emission close to the near-infrared (NIR) region. We show that the double emission depends on the excitation condition and analyze the electron-hole distribution responsible for the independent and simultaneous radiative exciton recombination in the PbS core and in the CdS Wz shell, respectively. These results highlight the importance of the driving force leading to preferential crystal growth in asymmetric QDs, and provide a pathway for the rational control of the synthesis of double color emitting giant QDs, leading to the effective exploitation of visible/NIR transparency windows. PMID:26837955

  13. ZnO/Sn:In2O3 and ZnO/CdTe band offsets for extremely thin absorber photovoltaics

    SciTech Connect

    Kaspar, Tiffany C.; Droubay, Timothy C.; Jaffe, John E.

    2011-12-28

    Band alignments were measured by x-ray photoelectron spectroscopy for thin films of ZnO on polycrystalline Sn:In2O3 (ITO) and single crystal CdTe. Hybrid density functional theory calculations of epitaxial zinc blende ZnO(001) on CdTe(001) were performed to compare with experiment. A conduction band offset of -0.6 eV was measured for ZnO/ITO, which is larger than desired for efficient electron injection. For ZnO/CdTe, the experimental conduction band offset of 0.25 eV is smaller than the calculated value of 0.67 eV, likely due to the TeOx layer at the ZnO/CdTe interface. The measured conduction band offset for ZnO/CdTe is favorable for photovoltaic devices.

  14. Impaired leaf CO2 diffusion mediates Cd-induced inhibition of photosynthesis in the Zn/Cd hyperaccumulator Picris divaricata.

    PubMed

    Tang, Lu; Ying, Rong-Rong; Jiang, Dan; Zeng, Xiao-Wen; Morel, Jean-Louis; Tang, Ye-Tao; Qiu, Rong-Liang

    2013-12-01

    Mechanisms of cadmium (Cd)-induced inhibition of photosynthesis in the Zn/Cd hyperaccumulator Picris divaricata were investigated using photosynthesis limitation analysis. P. divaricata seedlings were grown in nutrient solution containing 0, 5, 10, 25, 50, or 75 μM Cd for 2 weeks. Total limitations to photosynthesis (TL) increased from 0% at 5 μM Cd to 68.8% at 75 μM Cd. CO2 diffusional limitation (DL) made the largest contribution to TL, accounting for 93-98% of TL in the three highest Cd treatments, compared to just 2-7% of TL attributable to biochemical limitation (BL). Microscopic imaging revealed significantly decreased stomatal density and mesophyll thickness in the three highest Cd treatments. Chlorophyll fluorescence parameters related to photosynthetic biochemistry (Fv/Fm, NPQ, ΦPSII, and qP) were not significantly decreased by increased Cd supply. Our results suggest that increased DL in leaves is the main cause of Cd-induced inhibition of photosynthesis in P. divaricata, possibly due to suppressed function of mesophyll and stomata. Analysis of chlorophyll fluorescence showed that Cd supply had little effect on photochemistry parameters, suggesting that the PSII reaction centers are not a main target of Cd inhibition of photosynthesis in P. divaricata. PMID:24077231

  15. The effect of semiconducting CdSe and ZnSe nanoparticles on the fluorescence of Sm3+ in lead borate glasses

    NASA Astrophysics Data System (ADS)

    Mallur, Saisudha; Fatokun, Stephen; Babu, P. K.

    2015-03-01

    We studied the fluorescence spectra of Sm3+ doped lead borate glasses containing zinc selenide (ZnSe) and cadmium selenide (CdSe) nanoparticles with the following compositions (x PbO: 96.5-x B2O3:0.5 Sm2O3:3ZnSe/CdSe, x =36.5 and 56.5 mol%). These glass samples are prepared using the melt-quenching technique. Each sample is annealed just below the glass transition temperature at 400°C for 3 hrs and 6 hrs. We have chosen PbO-B2O3 glasses to incorporate Sm3+ ions because they have large glass forming region, high refractive index, and good physical and thermal stability. Fluorescence spectra of these samples are obtained with the excitation wavelength at 477 nm. Four fluorescence transitions are observed at 563 nm, 598 nm, 646 nm and 708 nm. The transition at 646 nm is found to be a hypersensitive transition that strongly depends on the covalency of the Sm-O bond and the asymmetry of the crystal field at Sm site. The 646 nm/598 nm fluorescence intensity ratio has been studied for different annealing times and PbO concentration for both ZnSe and CdSe samples. The presence of CdSe nanoparticles is seen to produce the greatest influence on the fluorescence intensity ratio. This could be due to the size of the CdSe nanoparticles and covalency of the Sm-O bond.

  16. Cd{sup 2+} versus Zn{sup 2+} uptake by the ZIP8 HCO{sub 3}{sup -}-dependent symporter: Kinetics, electrogenicity and trafficking

    SciTech Connect

    Liu Zhiwei; Li Hong; Soleimani, Manoocher; Girijashanker, Kuppuswami; Reed, Jodie M.; He Lei; Dalton, Timothy P.; Nebert, Daniel W.

    2008-01-25

    The mouse Slc39a8 gene encodes the ZIP8 transporter, which has been shown to be a divalent cation/HCO{sub 3}{sup -} symporter. Using ZIP8 cRNA-injected Xenopus oocyte cultures, we show herein that: [a] ZIP8-mediated cadmium (Cd{sup 2+}) and zinc (Zn{sup 2+}) uptake have V{sub max} values of 1.8 {+-} 0.08 and 1.0 {+-} 0.08 pmol/oocyte/h, and K{sub m} values of 0.48 {+-} 0.08 and 0.26 {+-} 0.09 {mu}M, respectively; [b] ZIP8-mediated Cd{sup 2+} uptake is most inhibited by Zn{sup 2+}, second-best inhibited by Cu{sup 2+}, Pb{sup 2+} and Hg{sup 2+}, and not inhibited by Mn{sup 2+} or Fe{sup 2+}; and [c] electrogenicity studies demonstrate an influx of two HCO{sub 3}{sup -} anions per one Cd{sup 2+} (or one Zn{sup 2+}) cation, i.e. electroneutral complexes. Using Madin-Darby canine kidney (MDCK) polarized epithelial cells retrovirally infected with ZIP8 cDNA and tagged with hemagglutinin at the C-terminus, we show that-similar to ZIP4-the ZIP8 eight-transmembrane protein is largely internalized during Zn{sup 2+} homeostasis, but moves predominantly to the cell surface membrane (trafficking) under conditions of Zn{sup 2+} depletion.

  17. Distribution, bioavailability, and potential ecological risk of Cu, Pb, and Zn in soil in a potential groundwater source area.

    PubMed

    Teng, Yanguo; Feng, Dan; Wu, Jin; Zuo, Rui; Song, Liuting; Wang, Jinsheng

    2015-05-01

    In this study, we examined three horizontal and vertical soil profiles along a sewage drainage ditch in order to determine the spatial distribution of Cu, Pb, and Zn in soils and to assess the bioavailability and potential ecological risks associated with these metals in a potential groundwater source area. Results showed that the concentrations of Cu, Pb, and Zn were approximately at background level, suggesting that human activities (industrial and agricultural pollution) had a negligible influence on these metals in soil, and that the concentrations reflected the natural background levels in the study area. Cu, Pb, and Zn concentrations were slightly higher in topsoil (0-20 cm) than deeper in the soil profile. Using a modified BCR sequential extraction method to evaluate the mobility and bioavailability of metals showed that the potential bioavailability sequence of Cu, Pb, and Zn at three depths in the soil profile was in the order Cu ≈ Pb < Zn. The potential ecological risk from the metals was evaluated using risk assessment code, and the results suggest that Cu and Zn pose no or low risk, while there is a low or medium risk from Pb. Results from groundwater monitoring showed that the groundwater was not polluted by leaching from soil. PMID:25910722

  18. Ore geology and fluid inclusion geochemistry of the Tiemurt Pb-Zn-Cu deposit, Altay, Xinjiang, China: A case study of orogenic-type Pb-Zn systems

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zheng, Yi; Chen, YanJing

    2012-04-01

    The Tiemurt Pb-Zn-Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330-390 °C with low salinities of 0.8-11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118-205 °C, and salinities of 1.4-3.4 wt.% NaCl eqv. This indicates that the ore fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a boiling fluid system. These FIs homogenize at temperatures ranging from 270 to 330 °C, with two salinity clusters of 1.9-14.5 and 37.4-42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation

  19. Structural and chemical analysis of CdSe/ZnSe nanostructures by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Peranio, N.; Rosenauer, A.; Gerthsen, D.; Sorokin, S. V.; Sedova, I. V.; Ivanov, S. V.

    2000-06-01

    A transmission electron microscopy (TEM) study of the structure and chemical composition of 0.5 to 3.0 ML (monolayer) CdSe sheets that are buried in a ZnSe matrix is presented. The CdSe layers were grown by migration-enhanced epitaxy at a growth temperature of 280 °C. We find two-dimensional (2D) CdxZn1-xSe layers with a total thickness of approximately 3 nm for all samples independent of the nominal CdSe content that contain inclusions (islands) with an enlarged Cd concentration. Plan-view TEM revealed two types of islands: First, small 2D islands with a lateral size of less than 10 nm, and second, large 2D islands with a lateral size between 30 and 130 nm. The combination of two-beam dark-field imaging and the new composition evaluation by lattice fringe analysis (CELFA) procedure allow the precise measurement of the Cd-concentration profiles of the CdxZn1-xSe layers. The CELFA evaluation yields a full width at half maximum value of (10+/-1) ML. The most probable origin of the broadening is a strong interdiffusion of Cd and Zn with an additional contribution of the segregation of the Cd atoms. The diffusion length of the Cd diffusion in ZnSe during the growth of the ZnSe cap layer is LD=(3.6+/-0.8) ML and the segregation probability is estimated to be R=(0.6+/-0.2). It is shown that neither objective lens aberrations nor specimen tilt are the main sources for the observed enormous broadening of the CdSe interlayers.

  20. Preliminary Performance of CdZnTe Imaging Detector Prototypes

    NASA Technical Reports Server (NTRS)

    Ramsey, B.; Sharma, D. P.; Meisner, J.; Gostilo, V.; Ivanov, V.; Loupilov, A.; Sokolov, A.; Sipila, H.

    1999-01-01

    The promise of good energy and spatial resolution coupled with high efficiency and near-room-temperature operation has fuelled a large International effort to develop Cadmium-Zinc-Telluride (CdZnTe) for the hard-x-ray region. We present here preliminary results from our development of small-pixel imaging arrays fabricated on 5x5x1-mm and 5x5x2-mm spectroscopy and discriminator-grade material. Each array has 16 (4x4) 0.65-mm gold readout pads on a 0.75-mm pitch, with each pad connected to a discrete preamplifier via a pulse-welded gold wire. Each array is mounted on a 3-stage Peltier cooler and housed in an ion-pump-evacuated housing which also contains a hybrid micro-assembly for the 16 channels of electronics. We have investigated the energy resolution and approximate photopeak efficiency for each pixel at several energies and have used an ultra-fine beam x-ray generator to probe the performance at the pixel boundaries. Both arrays gave similar results, and at an optimum temperature of -20 C we achieved between 2 and 3% FWHM energy resolution at 60 keV and around 15% at 5.9 keV. We found that all the charge was contained within 1 pixel until very close to the pixels edge, where it would start to be shared with its neighbor. Even between pixels, all the charge would be appropriately shared with no apparently loss of efficiency or resolution. Full details of these measurements will be presented, together with their implications for future imaging-spectroscopy applications.

  1. Study of ICP-RIE etching on CdZnTe substrate

    NASA Astrophysics Data System (ADS)

    Xu, Pengxiao; Qiao, Hui; Wang, Ren; Lan, Tianyi; Liu, Shijia; Wang, Nili; Zhou, Qin; Xu, Bin; Liu, Xiujuan; Lu, Yidan; Wang, Li-wei; Chang, Chao; Zhang, Kefeng; Li, Xiangyang

    2014-11-01

    CdZnTe is the most suitable epitaxial substrate material of HgCdTe infrared detectors, because its lattice constant is able to achieve full match with HgCdTe's lattice constant. It is always needed to etch CdZnTe substrate during the process of device separation or when we want to fabricate micro optical device on CdZnTe substrate. This paper adopts the more advanced method, Inductive Coupled Plasma-Reactive Ion Etching(ICP-RIE). The etching conditions of ICP-RIE on CdZnTe substrate are explored and researched. First of all, a set of comparative experiments is designed. All of CdZnTe samples with the same component are polished by chemical mechanical polishing before etching. Then all samples are etched by different types of etching gases(CH4/H2/N2/Ar) and different ratios of gases as we designed. The etching time is all set to 30 minutes. After that, the surface roughness, etching rate, etching damage and the profile of etched mesas are tested and characterized by optical microscope, step profiler and confocal laser scanning microscope (CLSM), respectively. It is found that, Ar gas plays the role of physical etching, but the etching rate will decline when the concentration of Ar gas is too high. The results also show that, the introduction of N2 causes more etching damage. Finally, combination of CH4/H2/Ar is used to etch CdZnTe substrate. The ratio of these gases is 2sccm/2sccm/10sccm. The testing results of optimized etching show that, the maximum etching rate reaches up to 20μm/h and the etched CdZnTe surface is smooth with very low etching damage. At last, aimed at the shortcoming of photoresist's degeneration after long-time etching, the ICP etching process of CdZnTe deep mesa is studied. Double-layer or triple-layer photoresist are spin-coated on CdZnTe substrate during the process of lithography. Then ICP etching is carried out with the optimized condition. It is seen that there is no more phenomena of degeneration.

  2. Heavy metal concentrations (Cd, Cu and Pb) in five aquatic plant species in Tasik Chini, Malaysia

    NASA Astrophysics Data System (ADS)

    Ebrahimpour, M.; Mushrifah, I.

    2008-04-01

    The purpose of this study was to determine the levels of heavy metals namely cadmium (Cd), copper (Cu) and lead (Pb) in the five aquatic plants. For this purpose, the concentration of heavy metals were measured in water and in the five aquatic plant species, Lepironia articulata, Pandanus helicopus, Scirpus grossus, Cabomba furcata and Nelumbo nucifera, in 15 sites from Tasik Chini. The concentrations were different among the plant species as well as among the parts of plants. The highest concentration of heavy metals among the aquatic plants and plant parts was found in the roots of S. grossus. The concentrations of Cd in the leaves and stems of submerged aquatic plant, C . furcata, were higher than concentration of Cd in the leaves and stems of emergent aquatic plant and floating leaf plant. The concentration of Cu in the stem of C. furcata was greater than that in the leaf, while the concentration of Cd was more in the leaf than in the stem. The heavy metal contents of the aquatic plants were in descending order of Pb > Cu > Cd. The metal concentration quotient of leaves/roots and stems/roots (ML/MR and MS/MR) were calculated. The highest internal translocation was found in P. helicopus, while the lowest internal translocation was found in S. grossus.

  3. Phytoextraction of Cd and Zn as single or mixed pollutants from soil by rape (Brassica napus).

    PubMed

    Cojocaru, Paula; Gusiatin, Zygmunt Mariusz; Cretescu, Igor

    2016-06-01

    This paper analyses the capacity of the rape (Brassica napus) to extract Cd and Zn from the soil and the effect of these metals on the morphometric parameters of the plant (length, weight, surface area, fractal dimension of leaves). Rape plants were mostly affected by the combined toxicity of the Cd and Zn mixture that caused a significant reduction in the rate of seed germination, the plant biomass quantity and the fractal dimension. In the case of Cd soil pollution, the bioaccumulation factor (BAF), bioaccumulation coefficient (BAC) as well as the heavy metal root-to-stalk translocation factor (TF) were determined. The results showed that B. napus had a great potential as a cadmium hyperaccumulator but not as an accumulator of Zn or Cd + Zn mixture. The efficiency of phytoextraction rape was 0.8-1.22 % for a soil heavily polluted with cadmium. PMID:26884243

  4. Bioaccessibility of Cd and Pb in tailings from a zinc smelting in Brazil: implications for human health.

    PubMed

    Ono, F B; Penido, E S; Tappero, R; Sparks, D; Guilherme, L R G

    2016-10-01

    Soils and wastes enriched with heavy metals may present ecological and human health risks. A considerable number of mining areas exist in Brazil, where high levels of metals have been found. However, studies of bioaccessibility of metals in soils/tailings from these areas are scarce, despite their potential informational contribution concerning exposure risks of residents near these areas. This study evaluated tailings collected from four sites of a zinc smelting area located in Brazil with aims to: (1) evaluate the presence of metals of potential concern; (2) investigate Cd and Pb bioaccessibility; and (3) determine the desorption kinetics of Cd and Pb. High concentrations of total Cd and Pb (up to 1743 mg Cd kg(-1) and 8675 mg Pb kg(-1)) and great variability were found in the tailings, indicating the importance of adequate planning for their final disposal, in order to avoid contamination in the surrounding environment. Cadmium and Pb bioaccessibility percentages in the intestinal phase were less than 47 and 4 %, respectively, which represents significant fractions not available for absorption in the intestinal tract. However, this material has to be monitored since its bioaccessibility may increase with eventual physicochemical changes, releasing Cd and Pb. Desorption kinetics experiments revealed that Pb in the samples remained in less labile fractions, whereas Cd was found in more labile fractions, which is in accordance with the bioaccessibility results. PMID:26493831

  5. CdS/PbSe heterojunction for high temperature mid-infrared photovoltaic detector applications

    SciTech Connect

    Weng, Binbin E-mail: shi@ou.edu; Qiu, Jijun; Zhao, Lihua; Chang, Caleb; Shi, Zhisheng E-mail: shi@ou.edu

    2014-03-24

    n-CdS/p-PbSe heterojunction is investigated. A thin CdS film is deposited by chemical bath deposition on top of epitaxial PbSe film by molecular beam epitaxy on Silicon. Current-voltage measurements demonstrate very good junction characteristics with rectifying ratio of ∼178 and ideality factor of 1.79 at 300 K. Detectors made with such structure exhibit mid-infrared spectral photoresponse at room temperature. The peak responsivity R{sub λ} and specific detectivity D{sup *} are 0.055 A/W and 5.482 × 10{sup 8} cm·Hz{sup 1/2}/W at λ = 4.7 μm under zero-bias photovoltaic mode. Temperature-dependent photoresponse measurements show abnormal intensity variation below ∼200 K. Possible reasons for this phenomenon are also discussed.

  6. Use of flue gas desulfurization gypsum for leaching Cd and Pb in reclaimed tidal flat soil.

    PubMed

    Yang, Ping; Li, Xian; Tong, Ze-Jun; Li, Qu-Sheng; He, Bao-Yan; Wang, Li-Li; Guo, Shi-Hong; Xu, Zhi-Min

    2016-04-01

    A soil column leaching experiment was conducted to eliminate heavy metals from reclaimed tidal flat soil. Flue gas desulfurization (FGD) gypsum was used for leaching. The highest removal rates of Cd and Pb in the upper soil layers (0-30 cm) were 52.7 and 30.5 %, respectively. Most of the exchangeable and carbonate-bound Cd and Pb were removed. The optimum FGD gypsum application rate was 7.05 kg·m(-2), and the optimum leaching water amount for the application was 217.74 L·m(-2). The application of FGD gypsum (two times) and the extension of the leaching interval time to 20 days increased the heavy metal removal rate in the upper soil layers. The heavy metals desorbed from the upper soil layers were re-adsorbed and fixed in the 30-70 cm soil layers. PMID:26758303

  7. Effect of ZnSe and CdSe nanoparticles on the fluorescence and optical band gap of Sm3+ doped lead borate glasses

    NASA Astrophysics Data System (ADS)

    Fatokun, Stephen O.

    For the first part of this work, we prepared a series of Sm-doped lead borate (PbO-B2O3) glasses containing zinc selenide (ZnSe) and cadmium selenide (CdSe) nanoparticles (NPs) and studied the Sm 3+ fluorescence by varying the glass composition and size of the NPs. We have chosen these heavy metal oxide glasses to incorporate Sm3+ ions because they have large glass forming region, high refractive index, and good physical and thermal stability. Lead borate glasses with the following compositions xPbO:(96.5-x)B2O 3:0.5Sm2O3:3ZnSe/CdSe, x=36.5 and 56.5 mol%) are prepared using the melt-quenching method. Transmission electron microscopy characterization was done to confirm both nucleation and growth of the NPs for different annealing times. Fluorescence spectra of these samples are obtained with the excitation wavelengths at 403 and 477nm. Three fluorescence transitions are observed at 563 nm, 598 nm and 646 nm. The transition at 646 nm is a electric dipole (ED) transition that strongly depends on the covalency of the Sm-O bond and the asymmetry of the crystal field at the Sm3+ site. The 646 nm/598 nm fluorescence intensity ratio has been studied for different annealing times and PbO concentration for both ZnSe and CdSe samples. Longer annealing times tend to make the crystal field at the Sm3+ site more symmetric in nature for these glasses. The presence of CdSe NPs is seen to produce the greatest influence on the fluorescence intensity ratio. This is believed to be due to the larger size of the CdSe nanoparticles and its stronger influence on Sm3+ ions. The second part of this work was dedicated to the understanding of the optical band gap of samarium doped lead borate glasses with and without ZnSe/CdSe NPs. Optical absorption spectra for all these glass samples show their absorption edge in the ultraviolet region. Detailed analysis of the absorption edge was carried out using the Mott-Davis model and the optical band gap and the width of the tail in the band gap

  8. Chemical immobilization of Pb, Cu, and Cd by phosphate materials and calcium carbonate in contaminated soils.

    PubMed

    Huang, Guoyong; Su, Xiaojuan; Rizwan, Muhammad Shahid; Zhu, Yifei; Hu, Hongqing

    2016-08-01

    Soil contamination with toxic metals has increasingly become a global concern over the past few decades. Phosphate and carbonate compounds are good passivation materials for Pb immobilization, while the effect of phosphate and carbonate on the immobilization of multiple heavy metals (Pb, Cu, and Cd) in contaminated soils was seldom investigated. In this study, bone meal (BM), phosphate rock (PR), oxalic acid-activated phosphate rock (APR), super phosphate (SP), and calcium carbonate (CC) were added to the contaminated soils to evaluate the effect of phosphate materials and calcium carbonate on the immobilization of Pb, Cu, and Cd. The results showed that the pH of the treated soils increased 1.3-2.7, except SP which decreased 0.5 at most. Compared to the control treatment, all phosphates and calcium carbonate added to the polluted soils increased the fraction of residual metals, and the application of APR, PR, BM, and CC significantly reduced exchangeable and carbonate-bound fraction metals. PR and APR were the most effective for the immobilization of Pb, Cu, and Cd in the soils among these materials. Moreover, the concentrations of all metals in the toxicity characteristic leaching procedure (TCLP) leachate decreased with increasing amounts of amendments, and the concentrations of Pb in the TCLP leachate for soils treated with PR and APR were below the nonhazardous regulatory limit of 5 mg L(-1) (US Environmental Protection Agency). Based on our results, phosphate rock and oxalic acid-activated phosphate rock are effective in the immobilization of multiple metals by reducing their mobility in the co-contaminated soils. PMID:27197655

  9. Relationship between the cathodoluminescence emission and resistivity in In doped CdZnTe crystals

    SciTech Connect

    Rodriguez-Fernandez, J.; Carcelen, V.; Dieguez, E.; Hidalgo, P.; Piqueras, J.; Vijayan, N.; Sochinskii, N. V.; Perez, J. M.

    2009-08-15

    Cadmium zinc telluride, CdZnTe, bulk single crystals doped with 10{sup 19} at./cm{sup 3} of indium in the initial melt were grown by vertical Bridgman technique. The samples were investigated by energy dispersive spectroscopy, cathodoluminiscence (CL), and current-voltage behavior at room temperature. The results shows that Cd and Te vacancy concentration depend on the indium and zinc concentrations. CL measurements indicate a relationship between radiative centers associated to Cd and Te vacancies and resistivity values.

  10. Cancer Cell Targeting Using Folic Acid/Anti-HER2 Antibody Conjugated Fluorescent CdSe/CdS/ZnS-Mercaptopropionic Acid and CdTe-Mercaptosuccinic Acid Quantum Dots.

    PubMed

    Singh, Gurpal; Kumar, Manoj; Soni, Udit; Arora, Vikas; Bansal, Vivek; Gupta, Dikshi; Bhat, Madhusudan; Dinda, Amit K; Sapra, Sameer; Singh, Harpal

    2016-01-01

    CdSe/CdS/ZnS and CdTe quantum dots (QDs) were synthesized by successive ion layer adsorption and reaction (SILAR) technique and direct aqueous synthesis respectively using thiol stabilizers. Synthesized CdSe/CdS/ZnS and CdTe QDs stabilized with 3-mercaptopropionic acid (MPA) and mercaptosuccinic acid (MSA) were used as fluorescent labels after conjugation with folic acid (FA) and anti-HER2 antibodies. Photoluminescence quantum yield of folated CdSe/CdS/ZnS-MPA and CdTe-MSA QDs was 59% and 77% than that of non-folated hydrophilic QDs. The folate receptor-mediated delivery of folic acid-conjugated CdTe-MSA and CdSe/CdS/ZnS-MPA QDs showed higher cellular internalization as observed by confocal laser scanning microscopic studies. Folated and non-folated CdTe-MSA QDs were highly toxic and exhibited only 10% cell viability as compared to > 80% cell viability with CdSe/CdS/ZnS-MPA QDs over the concentration ranging from 3.38 to 50 pmoles. Immunohistochemistry (IHC) results of human breast cancer tissue samples showed positive results with anti-HER2 antibody conjugated CdSe/CdS/ZnS-MPA QDs with better sensitivity and specificity as compared to conventional IHC analysis using diaminobenzedene staining. PMID:27398438

  11. [Toxic effects of CdSe/ZnS QDs to zebrafish embryos].

    PubMed

    Chen, Mu-Fei; Huang, Cheng-Zhi; Pu, De-Yong; Zheng, Chao-Yi; Yuan, Kai-Mi; Jin, Xing-Xing; Zhang, Yao-Guang; Jin, Li

    2015-02-01

    The toxic effects of CdSe/ZnS QDs on zebrafish (Danio rerio) embryos at different developmental stages were investigated in this study. The voluntary movement frequency, body length, hatching rate, mortality and malformation rate, SOD activities, MDA contents, mRNA expression of metallothionein (MT) and heat stress protein 70 (Hsp70) were used as indicators. The results showed that the EC50 was 316.994 nmol x L(-1) for zebrafish embryos (72 hpf) when exposed to CdSe/ZnS QDs. After the CdSe/ZnS QDs exposure, the embryos showed a significant increase in mortality and malformation rate, a decrease in hatching rate and body length, an advance in hatching time, and a changing in the spontaneous movement frequency, and many other toxic effects, such as the condensation of embryonic eggs, the formation of pericardial cysts and curvature of the spine. Moreover, it was found that the MDA contents in the embryos in CdSe/ZnS QDs groups were significantly increased, and the SOD activities were changed. In addition, the mRNA expression level of MT and Hsp70 were up-regulated. All the information suggests that exposure of CdSe/ZnS QDs can cause toxic effects on zebrafish embryos, and the effects may be related to the releasing of Cd2+, particle size and oxidative stress. PMID:26031104

  12. Bioavailability of Cd, Cr, and Zn to bivalves in south San Francisco Bay

    SciTech Connect

    Lee, B.G.; Luoma, S.N.; Geen, A. van

    1995-12-31

    The bioavailability of Cd, Cr, and Zn to benthic bivalves (Potamocorbular amurensis and Macoma balthica) is affected by the type of natural particles the animals ingest, and the concentration and speciation of dissolved metals. During a spring phytoplankton bloom in south San Francisco Bay dissolved Cd and Zn concentrations decreased to about half of pre-bloom concentrations. The concentrations of particulate Cd and Zn concentrations increased due to preferential uptake of these metals by phytoplankton. Assimilation of Cd was more efficient when clams ate pure phytoplankton (80% for M. balthica and 29% for P. amurensis) than when they were exposed to inorganic-dominated particles. M. balthica and P. amurensis assimilated 72% and 42% of Zn associated with the particles during the bloom. Assimilation of Cr was low (<6%) and particle type had little effect on its availability. Accumulation of Cd via the dissolved route was low in high salinity waters (15 ppt). Metal bioaccumulation in the bivalves was modeled using the experimentally determined physiological parameters. The results were compared to metal concentrations in clams from the Bay. The model suggested that the clams accumulated Cd and Zn at higher rates during the phytoplankton bloom, although dissolved metal concentrations in the water column were reduced.

  13. Quantum dot cosensitized solar cell based on PMOT@CdSe@ZnO core shell nanostructures with dual emission

    NASA Astrophysics Data System (ADS)

    Sehgal, Preeti; Narula, Anudeep Kumar

    2016-01-01

    Quantum dot sensitized solar cell based on poly(3-methoxythiophene) (PMOT)@CdSe@ZnO core shell nanostructure were synthesized where PMOT serves as hole transport material, CdSe acts as a photosensitizer which enhances visible range absorption and also helps in injection of electrons from PMOT to ZnO where ZnO provides channel for efficient electron transport. The properties of the device were assessed with and without CdSe quantum dots and effect of annealing was also observed on the device. After the addition of CdSe QDs, the visible light absorption of PMOT@ZnO was enhanced due to increase in surface area. PMOT@CdSe@ZnO exhibited dual emission, where CdSe and ZnO exhibited visible and UV emission respectively. The interface formed between PMOT and CdSe improves the charge separation. The better photovoltaic measurement of PMOT@CdSe@ZnO over CdSe@ZnO indicates that PMOT efficiently dissociate excitons at interface and suppress the interfacial charge recombination. A power conversion efficiency of 0.989% was attained for the device PMOT@CdSe@ZnO with Voc=0.56 V and Jsc=2.5 mA/cm2. Upon annealing, the efficiency of the device was enhanced to 1.1609% with Voc=0.58, Jsc=3.2 mA/cm2.

  14. Solvothermal synthesis of nanorods of ZnO, N-doped ZnO and CdO

    SciTech Connect

    Varghese, Neenu; Panchakarla, L.S.; Hanapi, M.; Govindaraj, A.; Rao, C.N.R.

    2007-12-04

    ZnO nanorods with diameters in the 80-800 nm range are readily synthesized by the reaction of zinc acetate, ethanol and ethylenediamine under solvothermal conditions. The best products are obtained at 330 deg. C with a slow heating rate. Addition of the surfactant Triton -X 100 gave nanorods of uniform (300 nm) diameter. By adding a small amount of liquid NH{sub 3} to the reaction mixture, N-doped ZnO nanorods, with distinct spectroscopic features are obtained. CdO nanorods of 80 nm diameter have been prepared under solvothermal conditions using a mixture of cadmium cupferronate, ethylenediamine and ethanol at 330 deg. C. Similarly, Zn{sub 1-x}Cd{sub x}O nanorods of a 70 nm diameter are obtained under solvothermal conditions starting with a mixture of zinc acetate, cadmium cupferronate, ethanol and ethylenediamine.

  15. [Immobilization remediation of Cd and Pb contaminated soil: remediation potential and soil environmental quality].

    PubMed

    Sun, Yue-Bing; Wang, Peng-Chao; Xu, Ying-Ming; Sun, Yang; Qin, Xu; Zhao, Li-Jie; Wang, Lin; Liang, Xue-Feng

    2014-12-01

    A pot experiment was conducted to investigate the immobilization remediation effects of sepiolite on soils artificially combined contamination by Cd and Pb using a set of various pH and speciation of Cd and Pb in soil, heavy metal concentration in Oryza sativa L., and soil enzyme activity and microbial quantity. Results showed that the addition of sepiolite increased the soil pH, and the exchangeable fraction of heavy metals was converted into Fe-Mn oxide, organic and residual forms, the concentration of exchangeable form of Cd and Pb reduced by 1.4% - 72.9% and 11.8% - 51.4%, respectively, when compared with the control. The contents of heavy metals decreased with increasing sepiolite, with the maximal Cd reduction of 39.8%, 36.4%, 55.2% and 32.4%, respectively, and 22.1%, 54.6%, 43.5% and 17.8% for Pb, respectively, in the stems, leaves, brown rice and husk in contrast to CK. The addition of sepiolite could improve the soil environmental quality, the catalase and urease activities and the amount of bacteria and actinomycete were increased to some extents. Although the fungi number and invertase activity were inhibited compared with the control group, it was not significantly different (P > 0.05). The significant correlation between pH, available heavy metal content, urease and invertase activities and heavy metal concentration in the plants indicated that these parameters could be used to evaluate the effectiveness of stabilization remediation of heavy metal contaminated soil. PMID:25826946

  16. Determination of Cd, Cr and Pb in phosphate fertilizers by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Nunes, Lidiane Cristina; de Carvalho, Gabriel Gustinelli Arantes; Santos, Dario; Krug, Francisco José

    2014-07-01

    A validated method for quantitative determination of Cd, Cr, and Pb in phosphate fertilizers by laser-induced breakdown spectroscopy (LIBS) is presented. Laboratory samples were comminuted and homogenized by cryogenic or planetary ball milling, pressed into pellets and analyzed by LIBS. The experimental setup was designed by using a Q-switched Nd:YAG at 1064 nm with 10 Hz repetition rate, and the intensity signals from Cd II 214.441 nm, Cr II 267.716 nm and Pb II 220.353 nm emission lines were measured by using a spectrometer furnished with an intensified charge-coupled device. LIBS parameters (laser fluence, lens-to-sample distance, delay time, integration time gate, number of sites and number of laser pulses per site) were chosen after univariate experiments with a pellet of NIST SRM 695 (Trace Elements in Multi-Nutrient Fertilizer). Calibration and validation were carried out with 30 fertilizer samples from single superphosphate, triple superphosphate, monoammonium phosphate, and NPK mixtures. Good results were obtained by using 30 pulses of 50 J cm- 2 (750 μm spot size), 2.0 μs delay time and 5.0 μs integration time gate. No significant differences between Cd, Cr, and Pb mass fractions determined by the proposed LIBS method and by ICP OES after microwave-assisted acid digestion (AOAC 2006.03 Official Method) were found at 95% confidence level. The limits of detection of 1 mg kg- 1 Cd, 2 mg kg- 1 Cr and 15 mg kg- 1 Pb and the precision (coefficients of variation of results ranging from 2% to 15%) indicate that the proposed LIBS method can be recommended for the determination of these analytes in phosphate fertilizers.

  17. Blue electroluminescence from Sb-ZnO/Cd-ZnO/Ga-ZnO heterojunction diode fabricated by dual ion beam sputtering.

    PubMed

    Pandey, Sushil Kumar; Awasthi, Vishnu; Verma, Shruti; Mukherjee, Shaibal

    2014-12-15

    p-type Sb-doped ZnO/i-CdZnO/n-type Ga-doped ZnO was grown by dual ion beam sputtering deposition system. Current-voltage characteristics of the heterojunction showed a diode-like rectifying behavior with a turn-on voltage of ~5 V. The diode yielded blue electroluminescence emissions at around 446 nm in forward biased condition at room temperature. The emission intensity increased with the increase of the injection current. A red shifting of the emission peak position was observed with the increment of ambient temperature, indicating a change of band gap of the CdZnO active layer with temperature in low-temperature measurement. PMID:25607047

  18. Field evaluation of the effectiveness of three industrial by-products as organic amendments for phytostabilization of a Pb/Zn mine tailings.

    PubMed

    Yang, Shengxiang; Cao, Jianbing; Li, Fengmei; Peng, Xizhu; Peng, Qingjing; Yang, Zhihui; Chai, Liyuan

    2016-01-01

    Although the potential of industrial by-products as organic amendments for phytostabilization has long been recognized, most of the previous studies addressing this issue have been laboratory-based. In this study, a field trial was conducted to evaluate the effectiveness of three industrial by-products [sweet sorghum vinasse (SSV), medicinal herb residues (MHR) and spent mushroom compost (SMC)] as organic amendments for phytostabilization of abandoned Pb/Zn mine tailings. Our results showed the following: (i) when compared to the control tailings, the mean concentrations of diethylene-triamine-pentaacetic acid (DTPA)-extractable Cd, Cu, Pb and Zn in SSV, MHR and SMC treatments decreased by 20.8-28.0%, 41.6-49.1%, 17.7-22.7% and 9.5-14.7%, respectively; (ii) the mean values of organic C, ammonium-N and available P in SSV, MHR and SMC treatments increased by 1.7-2.8, 10.8-14.9 and 3.9-5.1 times as compared with the mine tailings; and (iii) the addition of SSV, MHR and SMC significantly enhanced soil respiration and microbial biomass being 1.5-1.8 and 1.3-1.6 fold higher than those in the control tailings. There were no significant differences in soil biochemical properties among the plots amended with these by-products, suggesting that they were almost equally effective in improving the biochemical conditions of the tailings. In addition, the application of these amendments promoted seed germination, seedling growth, and consequently increased the vegetation cover and its biomass. Moreover, concentrations of Cd, Cu, Pb and Zn in above-ground parts of the plants were below the toxicity limit levels for animals. The results obtained in this field study confirmed that the three organic-rich industrial by-products could be used as amendments for phytostabilization of some types of mine tailings. PMID:26611119

  19. Occurrence of heavy metals (Hg, Cd, and Pb) and polychlorinated biphenyls in salted anchovies.

    PubMed

    Storelli, M M; Giachi, L; Giungato, D; Storelli, A

    2011-05-01

    The most popular brands of salted anchovies (Engraulis encrasicolus) from the Mediterranean Sea and Atlantic Ocean were purchased from several Italian supermarkets and grocery stores. Heavy metal (Hg, Cd, and Pb) and polychlorinated biphenyl (PCB) levels were determined and assessed by comparing the concentrations in these samples with the maximum permissible limits set by the European Union (Reg EC 629/2008 and Reg EC 1881/2006 [Off. J. Eur. Union L 173:3-9 and 364:5-24, respectively]). The Hg and Cd levels were higher than those of Pb in all samples examined. For Hg and Pb, the concentrations recorded in this study were below the authorized limits, while an appreciable percentage of samples from both locations (Mediterranean Sea, 35%, and Atlantic Ocean, 25%) showed Cd levels exceeding the threshold recommended for human consumption. Concerning PCBs, the results of principal component analysis showed that samples from the two different marine areas appeared to be discriminate, with Mediterranean anchovies more contaminated than the others, in spite of their lower lipid content. However, anchovy samples from both locations had dioxinlike-PCB levels (Mediterranean Sea, 0.011 pg World Health Organization toxic equivalency [WHO-TEQ] g(-1), wet weight, and Atlantic Ocean, 0.007 pg WHO-TEQ g(-1), wet weight) that were below the WHO-TEQ maximum concentration set by European regulation. The results of this study will help in generating data needed for the assessment of heavy metal and PCB intake from this food. PMID:21549051

  20. Distribution Characteristics, Concentrations, and Sources of Cd and Pb in Laoxiawan Channel Sediments from Zhuzhou, China.

    PubMed

    Chen, Wen-Wen; Zhang, Jian-Xin; Abass, Olusegun-Kazeem; Wen, Xin-Yu; Huang, Huan-Fang; Qu, Cheng-Kai; Qi, Shi-Hua

    2016-06-01

    Twenty sediment cores encompassing surface (0-20 cm) and deeper (50-60 cm) sediment layers were retrieved from the 3000 m-long Laoxiawan Channel, which receives industrial effluents from Zhuzhou City (China). Analytical results showed that cadmium (Cd) concentrations ranged between 115.7-1126.7 and 108.8-2059.3 mg/kg while lead (Pb) values ranged between 234-3000 and 145-4292 mg/kg in the surface and bottom sediments, respectively. The results also indicated that high levels of Cd and Pb were present in the vicinity of the channel mouth and confluence area. Indices for potential ecological risk and geo-accumulation were used to evaluate the environmental effects and intensity of heavy metal pollution over time. High concentrations of Cd and Pb in the bottom sediments of Laoxiawan Channel were mainly associated with wastewater discharge (10(6) m(3)/year). Thus, the Laoxiawan Channel may be an important metal contaminant source for the Xiang River. PMID:27025765

  1. Enhanced visible light photocatalytic performance of ZnO nanowires integrated with CdS and Ag2S.

    PubMed

    Chen, Chienhua; Li, Zhengcao; Lin, Hehnan; Wang, Guojing; Liao, Jiecui; Li, Mingyang; Lv, Shasha; Li, Wei

    2016-02-18

    A series of ZnO-CdS-Ag2S ternary nanostructures with different amounts of Ag2S were prepared using simple and low-cost successive ionic layer adsorption and reaction (SILAR) and a chemical precipitation method. The ZnO nanowires, with a diameter of ∼100 nm and a length of ∼1 μm, were modified by coating CdS and Ag2S. CdS has a high absorption coefficient and can efficiently match with the energy levels of ZnO, which can enhance the light absorption ability of the nanostructures. In addition, Ag2S with a narrow band gap was used as the main light absorber and played an important role in increasing the light absorption in the visible light region. The photocatalytic activity of the ZnO-CdS-Ag2S ternary nanostructures was investigated using the degradation of methyl orange (MO) in an aqueous solution under visible light. The ZnO-CdS-Ag2S ternary nanostructures were found to be more efficient than ZnO nanowires, ZnO-CdS nanowires, and ZnO-Ag2S nanowires. There is 7.68 times more photocatalytic activity for MO degradation in terms of the rate constant for ZnO-CdS-Ag2S 15-cycle ternary nanostructure compared to the as-grown ZnO. Furthermore, the effect of the amount of Ag2S and CdS on the ZnO surface on the photocatalytic activity was analyzed. The superior photo-absorption properties and photocatalytic performance of the ZnO-CdS-Ag2S ternary nanostructures can be ascribed to the heterostructure, which enhanced the separation of the photo-induced electron-hole pairs. In addition, visible light could be absorbed by ZnO-CdS-Ag2S ternary nanostructures rather than by ZnO. PMID:26815888

  2. Geological, rare earth elemental and isotopic constraints on the origin of the Banbanqiao Zn-Pb deposit, southwest China

    NASA Astrophysics Data System (ADS)

    Li, Bo; Zhou, Jia-Xi; Huang, Zhi-Long; Yan, Zai-Fei; Bao, Guang-Ping; Sun, Hai-Rui

    2015-11-01

    The newly discovered Banbanqiao Zn-Pb deposit in the southeastern part of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province is located on the western Yangtze Block, southwest China. Ore bodies of the Banbanqiao deposit are stratiform type, host in dolomitic limestone and dolostone of the Lower Carboniferous Dapu Formation and occur within the NNE-trending Banbanqiao anticline. More than 1.5 million tones (Mt) Zn-Pb ores at grades of 0.26-10.32 wt.% Pb and 0.81-28.8 wt.% Zn have been controlled until now. δ13CPDB and δ18OSMOW values of calcite separates range from -2.8‰ to -0.7‰ (average -1.1‰) and +14.1‰ to +17.0‰ (average +15.5‰), respectively. The δ13CPDB values are similar to those of marine carbonate rocks, but higher than those of mantle and significantly different from those of sedimentary organic matter. However, the δ18OSMOW values are among those of mantle, marine carbonate rocks and sedimentary organic matter. δ34SCDT values of sulfide separates range from +3.2‰ to +9.9‰ (average +6.5‰), unlike mantle-derived sulfur (0 ± 3‰), whilst lower than evaporites (+22‰ to +28‰) within host strata. 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of country shale and dolostone whole-rock samples are 18.47, 15.66 and 38.70, and 18.44-18.60, 15.66-15.85 and 38.70-39.14, respectively. Sulfide separates have 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values ranging from 18.03 to 18.73, 15.65 to 15.78 and 38.15 to 39.14, respectively. These Pb isotopic data indicate a clearly crustal source of Pb in the plot of 207Pb/204Pb vs. 206Pb/204Pb. Total REE (ΣREE) contents of country shale and dolostone whole-rock samples are 2.63 ppm and 0.72-86.2 ppm with δEu values are 2.79 and 0.34-0.70, respectively. Pyrite, sphalerite, galena and calcite samples have ΣREE contents of 5.3-36.4 ppm, 0.29-3.39 ppm, 0.52 ppm and 22.0-41.1 ppm, respectively, and δEu values of 0.64-0.86, 0.94-2.86, 0.32 and 0.21-0.45, respectively. These rare earth

  3. Growth of CdZnTe Crystals for Radiation Detector Applications by Directional Solidification

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua

    2014-01-01

    Advances in Cadmium Zinc Telluride (Cd(sub 1-x)Zn(sub x)Te) growth techniques are needed for the production of large-scale arrays of gamma and x-ray astronomy. The research objective is to develop crystal growth recipes and techniques to obtain large, high quality CdZnTe single crystal with reduced defects, such as charge trapping, twinning, and tellurium precipitates, which degrade the performance of CdZnTe and, at the same time, to increase the yield of usable material from the CdZnTe ingot. A low gravity material experiment, "Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment", will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). One section of the flight experiment is the melt growth of CdZnTe ternary compounds. This talk will focus on the ground-based studies on the growth of Cd(sub 0.80)Zn(sub 0.20)Te crystals for radiation detector applications by directional solidification. In this investigation, we have improved the properties that are most critical for the detector applications (electrical properties and crystalline quality): a) Electrical resistivity: use high purity starting materials (with reproducible impurity levels) and controlled Cd over pressure during growth to reproducibly balance the impurity levels and Cd vacancy concentration b) Crystalline quality: use ultra-clean growth ampoule (no wetting after growth), optimized thermal profile and ampoule design, as well as a technique for supercool reduction to growth large single crystal with high crystalline quality

  4. Electronic structure and optical absorption spectra of CdSe covered with ZnSe and ZnS epilayers

    NASA Astrophysics Data System (ADS)

    Yun, So Jeong; Lee, Geunsik; Kim, Jai Sam; Shin, Seung Koo; Yoon, Young-Gui

    2006-02-01

    Using the first-principles methods we compute the electronic structure and the absorption spectra for a wurtzite CdSe (0001) slab covered with zincblende ZnSe and ZnS epilayers. For each structure we compute the DOS and the imaginary part of the dielectric function. We find that the semiconductor passivation shifts the 'near Fermi-level' states of the bare CdSe slab down to lower energy levels. The migration suggests the decrease of surface effects and energy loss. We observe the substantial reduction of the abnormal peaks in the absorption spectra of the bare CdSe slab, which seems to be a consequence of the DOS migration. This is consistent with the experimental results that a proper passivation enhance the luminescence efficiency. We also study the case that the epilayer surface is terminated with PH 3 and find the PH 3 passivation also reduces the surface state to some extent.

  5. Recombination control in high-performance quantum dot-sensitized solar cells with a novel TiO2/ZnS/CdS/ZnS heterostructure.

    PubMed

    Lee, Young-Seok; Gopi, Chandu V V M; Venkata-Haritha, Mallineni; Kim, Hee-Je

    2016-08-01

    Charge recombination occurring at the TiO2/QDs/electrolyte interface is a crucial factor that limits the power conversion efficiency (η) of quantum dot-sensitized solar cells (QDSSCs). This paper presents a new approach by inserting a ZnS layer between the TiO2 and CdS/ZnS to prepare a TiO2/ZnS/CdS/ZnS sensitized photoelectrode for QDSSC applications. The CdS QDs and ZnS passivation layers were deposited using a reproducible and controlled successive ionic layer adsorption and reaction method. The TiO2/ZnS/CdS/ZnS based QDSSCs exhibited a power conversion efficiency (η) value of 3.69%, which is significantly higher than the 3.02% and 2.09% observed for solar cells with a TiO2/CdS/ZnS device and without a passivation layer (TiO2/CdS), respectively. The elevated performance of the TiO2/ZnS/CdS/ZnS-based QDSSCs was attributed to the pre-assembled ZnS layer enhancing the light harvesting and acting as a blocking layer to shield the TiO2 core from the outer QDs and the electrolyte, thereby retarding the interfacial recombination of electrons from the TiO2