Showing papers on "Copper published in 1983"

Effect of Soil pH on Adsorption of Lead, Copper, Zinc, and Nickel

Abstract: Lead, copper, nickel, and zinc adsorption by and desorption from pH-adjusted soils has been studied. Surface and subsurface horizon samples of two soils were equilibrated with varying amounts of Ca(OH)/sub 2/ prior to metal addition. The amount of all four metals retained was dependent upon pH of the soil sample, with retention dramatically increasing above pH 7.0 to 7.5. With the exception of Ni, at least 70 to 75% of the retained metal was extractable in 0.01N HCl. Nickel was somewhat less extractable, with that sorbed by the highest pH soils being the least extractable. Based on subsequent extractibility, the soils used appeared to have specific adsorption sites for Pb, Ni, and Cu but little or none for Zn. These studies cast some doubt on the concept of pH management for immobilizing heavy metals placed on the land in that sorbed metals were substantially extractable by 0.01M HCl, which has been used to estimate plant availability of soil ions.

Copper stress underlies the fundamental change in intracellular location of methane mono-oxygenase in methane-oxidizing organisms: Studies in batch and continuous cultures

Abstract: The intracellular location of methane mono-oxygenase (MMO) activity in the methanotroph Methylococcus capsulatus (Bath) has been shown to depend primarily on the availability of copper. MMO activity was observed in the particulate fraction of cell extracts under conditions of copper excess but switched to a soluble location in response to copper stress. The two activities could be differentiated by sensitivity to a range of inhibitors and by major changes in the polypeptide banding patterns on denaturing polyacrylamide gels. MMO activity concomitant with the oxidation of ethanol was only observed in cells with particulate MMO activity but could be lost independently in response to copper stress. Examination of other methanotrophs indicated that the copper effect could explain a similar switch in intracellular location observed in Methylosinus trichosporium OB3b but that some methanotrophs do not have the capacity to overcome copper stress in this way.

Distribution and forms of copper, zinc, cadmium, iron, and manganese in soils near a copper smelter1

Abstract: We examined the contamination of soil by copper, zinc, and cadmium with respect to distance from a copper smelter. The majority of contamination was in the immediate vicinity of the smelter. Between 30 to 60 percent of total Cd was exchangeable in MgCl2 solution, and the exchangeability was much greater than that of the other elements examined, including iron and manganese. Most of the Cu, Zn, and Mn were present in an oxalate-extractable fraction, but only small amounts were extractable by citrate-dithionite-bicarbonate (CDB) solution. This suggests that Cu, Zn, and Mn were more strongly associated with amorphous iron oxides, with only small amounts being occluded in crystalline iron oxides. Only Cu was appreciably associated with the soil organic fraction. The treatment of soils with sodium hyperchlorite prior to oxalate extraction appeared to be necessary to better estimate the amounts of Cu associated with the oxalate-extractable fraction. Without this pretreatment, the oxalate extraction could overestimate the amounts of Cu associated with this particular fraction possibly due to the dispersion of organically complexed Cu in the oxalate solution. The mobility of Cu, Zn, and Cd in the soils was limited, as evidenced by a sharp reduction in concentrations of the three elements with depth. Comparing subsoil concentrations of these elements with those from areas relatively unpolluted by smelter fallout revealed that Cd was more leachable than Cu or Zn under western Washington conditions.

Diffusion of metals in silicon dioxide

Abstract: The diffusion coefficient and solubilities of several metals (Ag, Cu, Au, Pd, and Ti) have been investigated by bias temperature stress (BTS) of (MOS) structures using the candidate metal as the electrode. Temperatures ranged from 250° to 600°C, and the electric fields ranged from +106 to −106 V/cm in ambients of vacuum (10−6 torr), nitrogen, and forming gas . In dry , the activation energy for silver diffusion is found to be 1.24 eV in the temperature range of 275°–365°C. The diffusion coefficient for silver at 300°C in silicon dioxide is . Copper diffusion has an activation energy of 1.82 eV in the temperature range of 350°–450°C in a forming gas environment and a diffusion coefficient in at 450°C of . A thermodynamic model to predict the activation energy of the solid solubility of these metals in and an interstitial diffusion model, that includes both strain and electrostatic energies, which predicts the diffusion activation energy, have been developed. Diffusion coefficients are estimated from a closed form solution of the diffusion equation and the observed behavior of the metal in .

Distribution of cadmium, zinc, copper, and lead in soils of industrial northwestern Indiana

Abstract: Five undisturbed locations of sandy Oakville and Plainfield soils under oak forest in the heavily industrialized region of northwestern Indiana were sampled at four depths, to assess the nature and extent of Cd, Zn, Cu, and Pb contamination. The litter layer and top 2.5 cm of soil at a site within 5 km of the center of the industrial complex were highly contaminated with Cd, Zn, Cu, and Pb. Levels of Cd and Zn decreased rapidly with distance to the south and east, while Cu and Pb decreased more erratically, with all metals reaching nearly background levels at 18 km. Samples taken deeper in the profiles (30 to 36 cm) did not show elevated metal levels compared with a rural site 67 km to the south. Sequential extraction methods applied to the top 2.5-cm soil samples showed large amounts of relatively labile metals associated with exchange sites (KNO/sub 3/-extractable: 23, 10, 1 and 8% of total Cd, Zn, Cu, and Pb, respectively), bound by soil organic matter (Na/sub 4/P/sub 2/O/sub 7/-extractable: 21, 33, 24, and 41% of the total Cd, Zn, Cu, and Pb), and associated with carbonates and/or noncrystalline Fe oxides (EDTA-extractable: 12, 8, 26, and 28% of themore » total Cd, Zn, Cu, and Pb). Minimal amounts of the metals were within the small amount of crystalline Fe and Mn oxides present in these soils. Non-extractable (residual) metals ammounted to 26, 32, 23, and 4% of the total Cd, Zn, Cu, and Pb.« less

Effect of composition on the structure and electrical properties of As‐Se‐Cu glasses

Abstract: As‐Se‐Cu glasses, with Cu content varying between 5 and 25 at. %, were produced by quenching from the melt. The values of resistivity and activation energy for conduction decreased continuously with increasing the copper content. Memory switching phenomena was observed in glasses containing Cu less than 20 at. %. Glasses containing higher Cu concentration showed a reverse switching cycle. Thermally induced changes in the structural properties have been examined using x‐ray diffraction, differential thermal analysis, and scanning electron microscopy. The results were discussed on the basis of thermally induced transformations.

Surface characterization of copper(II) oxide-zinc oxide methanol-synthesis catalysts by x-ray photoelectron spectroscopy. 1. Precursor and calcined catalysts

Abstract: A surface characterization of the precursor and calcined copper oxide-zinc oxide (CuO-ZnO) catalysts prepared both by coprecipitation and by impregnation methods was carried out by using x-ray photoelectron spectroscopy (XPS). Strong oxide-oxide interactions were found to result in the formation of several surface copper species in the coprecipitated catalysts. With the catalysts containing 80-30 wt % CuO, it is proposed that the CuO structure is distorted to produce amorphous copper oxide phases in the surface layer. The copper species in the catalysts with > 80 wt % CuO are composed of the Cu/sup 2 +/ ions in crystalline CuO and the amorphous phases. As for the catalysts containing less than 30 wt % CuO XPS results showed the presence of Cu/sup 2 +/ ions, which dissolved substitutionally in the ZnO lattice and formed highly covalent bondings with oxygen anions. In contrast to the coprecipitated catalysts, the impregnated catalysts showed no appreciable interactions between copper and zinc oxides. The surface copper species in the precursor catalysts were attributed to copper hydroxycarbonate in the high copper content catalysts and to the copper in zinc hydroxycarbonate in the low copper content catalysts. 5 figures, 3 tables.

Accumulation of copper, lead and arsenic in some Australian orchard soils

Abstract: A survey was made of copper, lead and arsenic in 98 surface soils from orchards in South Australia and Tasmania and the distribution of these elements in six representative soil profiles was studied. Copper, lead and arsenic have accumulated in the soils due to the use of sprays. Concentrations were found which were 25-35 times greater than background values. Investigation of the profiles indicated that copper and lead have been strongly retained in the upper parts of the profiles, but arsenic can be lost. Possible mechanisms for loss of arsenic are discussed. Copper and lead extracted by DTPA and EDTA were highly correlated with 'total' concentrations determined on aqua regia digests. No relationships were evident between the concentrations of copper, lead and arsenic in former orchard soils and the concentrations in ryegrass and white clover.

CRYSTAL STRUCTURE AND MAGNETIC PROPERTIES OF (μ-AZIDO)-(μ-HYDROXO)BIS((N,N,N′N′-TETRAMETHYLETHYLENEDIAMINE)COPPER(II)) PERCHLORATE, A COPPER(II) DINUCLEAR COMPLEX WITH A LARGE FERROMAGNETIC INTERACTION

Abstract: Cristallisation dans le groupe P4 2 /mnm avec a=9,50 et c=13,94 A, Z=2. Coordinence 4 des atomes de cuivre selon une geometrie plane. Etude des proprietes magnetiques de 2 a 300 K

The Olympic Dam copper-uranium-gold deposit, Roxby Downs, South Australia

Abstract: A new type of stratabound sediment-hosted ore deposit. The deposit is estimated to contain in excess of 2,000 million metric tons of mineralized material with an average grade of 1.6 percent copper, 0.06 percent uranium oxide, and 0.6 g/metric ton gold. Proterozoic. Graben fill sediments were deposited in an arid subaerial environment during rifting or strike-slip faulting. The stratabound sulfide mineralization is syngenetic or syndiagenetic and is probably related to local volcanism. Uranium and rare earths were deposited during and after the sulfide mineralizing phase. Unusual features are the association of copper, uranium, rare earths, and gold; the association of reduced sulfur species such as chalcocite and bornite with high hematite concentrations; and the occurrence of stratabound copper and uranium minerals in sedimentary rocks deposited in a very high-energy environment.--Modified journal abstract.

Surface characterization of copper(II) oxide-zinc oxide methanol-synthesis catalysts by x-ray photoelectron spectroscopy. 2. Reduced catalysts

Abstract: The surface state of the coprecipitated cupric oxide-zinc oxide (CuO-ZnO) catalysts reduced at 250/sup 0/C with H/sub 2/ was investigated by x-ray photoelectron spectroscopy (XPS). It was found that a monovalent copper species was present in the surface of the catalysts with low copper contents. It was revealed that two distinct types of copper metal species, both of them being negatively charged by electron transfer from ZnO, were produced in the catalyst surface upon the reduction. In the high copper content catalysts (> 25 wt % CuO), the predominant Cu metal species is described by well-dispersed metal particles, whereas in the low copper content catalysts (< 10 wt % CuO), the major copper metal species is best characterized by a two-dimensional epitaxial copper layer over ZnO. It is concluded that both the two-dimensional copper metal and Cu/sup +/ are formed from Cu/sup 2 +/ dissolved in a ZnO lattice, while the copper metal particles are originating mainly from crystalline and amorphous copper oxide phases. The two-dimensional copper metal species was found to be preferentially reoxidized to Cu/sup +/ when exposed to air at room temperature. The two-dimensional Cu/sup 0/-Cu/sup +/ species are suggested to be catalytically active for the methanolmore » synthesis at low temperature and pressure. The reduction of ZnO was observed only when reduced at 500/sup 0/C and in the presence of copper. In the case of the impregnated catalysts, no appreciable interactions were found between Cu metal and ZnO, in contrast to the coprecipitated catalysts. 7 figures, 2 tables.« less

DNA- and protein-scission activities of ascorbate in the presence of copper ion and a copper-peptide complex.

Abstract: L-Ascorbic acid, when combined with either copper(II) ion or a copper(II)-tripeptide complex, extensively cleaved several viral DNAs and proteins under in vitro conditions. Neither ascorbate nor copper tripeptide (Cu2+-diglycyl-L-histidine) alone caused any apparent changes on these molecules. Various transition metal ions and reducing agents were examined under comparable conditions to determine the basic requirements for both DNA degradation and protein scission activities. Copper and iron are the two most effective transition metal ions examined that exhibit these activities in the presence of ascorbate. The addition of catalase, but not superoxide dismutase, can partially inhibit the scission of DNA in vitro, suggesting that H2O2 may be involved in these activities. Among the various reducing agents tested, ascorbate was most effective in causing DNA scission and protein cleavage, corroborating the possible role of H2O2 in the cleavage reactions. One of the products of the reactions of copper/ascorbate is probably the hydroxyl radical generated from H2O2, which can be formed from the oxidation of ascorbate.

Bis(2,9-diphenyl-1,10-phenanthroline)copper(I): a copper complex with a long-lived charge-transfer excited state

Abstract: The title compound, [Cu(dpp)2]+(dpp = 2,9-diphenyl-1,10-phenanthroline), exhibits long-lived emission at room temperature in solution, and in contrast with copper(I) complexes of less bulky ligands, the emission persists in polar media; a water soluble derivative of [Cu(dpp)2]+ is luminescent at room temperature in aqueous solution and undergoes efficient redox photochemistry in the presence of electron acceptors.

Sensitivity of Natural Bacterial Communities to Additions of Copper and to Cupric Ion Activity: A Bioassy of Copper Complexation in Seawater

Abstract: Cupric ion bioassays with natural bacterial communities were conducted in seawater samples at five stations in the Gulf of Mexico, ranging from low-productivity oceanic to high-productivity coastal. In these bioassays, we measured the incorporation of 3H-labeled amino acids by marine microbial communities following serial additions of ionic copper (CuSO4) and cupric ion buffers (combinations of CuSO4 and nitrilotriacetic acid, a synthetic chelator). The bioassays were designed to yield relations between (1) amino acid incorporation and total copper concentration, (2) incorporation and cupric ion activity, and (3) cupric ion activity and total copper concentration.

On the Relationship between Protein-Forced Ligand Fields and the Properties of Blue Copper Centers

Abstract: The stable conformation of blue copper proteins forces the metal ion into a unique geometrical ligand arrangement. Spectroscopic data suggest that at least 70 kJmol−1 would be required to twist the protein into a conformation that would allow the cupric ion to occupy a square planar site. The observation that the γ S→ Cu(x2-y2) transition energy does not change with increasing ligand field strength is interpreted in terms of a model in which Cu(xz, yz)ligand back bonding enhances the splitting between the Cu(x2-y2 ) and Cu(xz, yz) levels in blue sites with high chemical reduction potentials, thereby providing an explanation of the special stability of the cuprous state.