Mass Of Cu Research Articles

Measurement and dynamic modeling of trace metal mobilization in soils using DGT and DIFS.

The technique of diffusive gradients in thin-films (DGT) accumulates metals on a Chelex resin after their diffusive transport through a hydrogel. It lowers metal concentrations in soil solution adjacent to the device and induces resupply of metal associated with the solid phase. DGT devices were deployed in an alluvial gley soil for 21 different time periods between 4 h and 19.5 d. The accumulated masses of Cu, Cd, Ni, and Zn were used to calculate the distribution coefficient for labile metal, Kdl, and adsorption and desorption rate constants. Calculations were performed using a dynamic numerical model of DGT-induced fluxes in soils (DIFS). It assumes first-order exchange between solid phase and solution and diffusional transport in both the soil solution and the hydrogel. The DIFS model fitted changes in accumulated mass with time very well. Values of Kdl calculated from DIFS of 100 (Cd), 250 (Cu), 150 (Ni), and 150 (Zn) were larger than values of distribution coefficients estimated by exchange with Ca(NO3)2 but similar to those estimated by isotopic exchange (Cd and Zn only). These results suggest that the solid-phase pool of metal affected by the removal of labile metal by DGT, which operates on a time scale of minutes, is similar to the solid-phase pool of metal that can isotopically exchange with solution on a time scale of 2 d. Response times of minutes were consistent with interaction rates with surfaces, and desorption rate constants agreed with other reported values. An appraisal of the DIFS model demonstrated the importance of the labile pool size in the solid phase for controlling supply to a sink, such as DGT or a plant. As values of Kdl and kinetic parameters are obtained using DGT with minimal soil disturbance and by a similar mechanism to that involved in plant uptake, they may be pertinent to bioavailability studies.

The influence of structural fluorine on biotite oxidation in copper-bearing, aqueous solutions at low temperatures and pressures

High-F (5.4 wt%) and low-F (0.8 wt%) biotites were reacted with aqueous (Cu, Na 2)Cl 2 solutions at ambient conditions to investigate biotite oxidation mechanisms at low temperatures and pressures and at atmospheric pO 2. The exchange of Cu +2 for interlayer cations increases the rate of biotite oxidation under these conditions. Solid reactants and products were characterized by Mössbauer spectroscopy, X-ray diffraction, and comprehensive bulk chemical analyses. Even though both biotites were pretreated with a sodium tetraphenylboron (NaTPB) solution, which rapidly exchanges Na for K, only about 50% of the interlayer K was exchanged during most of these experiments. As a result, the exchange reactions produced variably expanded phases with d(001) ranging from approximately 10 to 14 Å. Octahedral Fe +2 in samples of high- and low-F biotite was oxidized rapidly during Cu exchange. The degree of Fe +2 oxidation amounted to about 50% of the total Fe in most experiments and was nearly independent of the total mass of Cu introduced into the interlayer which ranged from 2.0 to 9.2 wt% CuO. The Mössbauer spectra also show that the Fe +2 in M(1) octahedra of the high-F biotite was oxidized more slowly than Fe +2 in M(2) sites, whereas in the low-F biotite experiments M(1) Fe +2 was oxidized at a slightly faster rate than the Fe +2 in M(2) sites. Our study suggests that the total amount of Fe oxidized was limited by the amount of K exchanged, and that preferred oxidation of Fe +2 at M(2) sites relative to M(1) sites was a function of the F content of these biotites. Charge transfer from octahedral Fe +2 to the interlayer may be facilitated by deprotonation. In exchange experiments conducted on the F-rich biotite, Fe +2 oxidation at M(1) sites was limited indicating that preferential substitution of F for OH might occur at the M(1) site. We used the Fe-F avoidance law to develop an F-OH ordering model that preferentially distributes F on selected trans positions of Fe-filled M(1) octahedra in Fe- and F-rich biotites. If charge transfer is facilitated by the presence of OH then the proposed F-OH ordering model could account for the selective deactivation of the Fe +2 oxidation mechanism at the M(1) site.

Sediment contaminants off the coast of Sydney, Australia: A model for their distribution

A baseline study of sediments along the continental shelf adjacent to Sydney was conducted in 1990–1991. The aims of this study were to identify the distribution patterns of a range of inorganic and organic contaminants and to place these distributions in the context of both local sources and sediment/contaminant relationships. The baseline study identified three spatially discrete, shore parallel zones of contaminants. Highest contaminant concentrations occurred in a zone 2–4 km offshore, with lower concentrations occurring in zones less than 2 km and more than 4 km from the coast. Stepwise multiple regression models were used to identify and quantify heavy-metal/geochemical associations. Heavy-metal distributions in sediments were principally related to Fe content, organic carbon content and water depth. Weaker associations were also found with Mn, carbonate content and fine-sized particles (<63 μm). Multiple regression models, limited to these six variables, accounted for up to 66% of the variability in the distribution of a number of metals, including Ph, Cr, Zn, Ni, Cu, As, Hg, Cd and Se. Using Cu and Cr as examples, model residuals are shown to highlight discharges from significant point sources such as sewage outfalls and urbanized estuaries. The cohesiveness of residual distribution for a range of metals, and the association of these residuals only with point sources, suggests they represent anthropogenic inputs for those metals. The total mass of Cu and Cr residuals have been calculated in an effort to identify the contribution of identified point sources to the total offshore contaminant budget compared to other identified coastal sources.

Direct introduction of powder samples for inductively coupled plasma atomic emission spectrometry: effect of particle size on emission intensity

The direct determination of trace elements in finely divided solids by ICP-AES and ICP-MS is subject to errors if the efficiency of the process leading to analyte volatilization, emission or ionization is a function of particle size. Direct transport of weighed quantities of powders into a plasma at constant total carrier gas flow is possible using a fluidized-bed powder delivery system. Emission intensity derived from known masses of Cu, Mn, Co, Ti and Cd carried to the plasma chelated (silica-immobilized 8-hydroxyquinoline) to 21, 24, 34 and 43 μm diameter particles was compared. Copper emission intensity was independent of particle size, and varied linearly with mass flow rate of powder. Copper was shown to be suitable as an internal standard element with which to monitor the particle-size dependence of the emission of several other elements. At constant rate of transport of powder to the plasma, the emission intensity of Si and Zn (particle matrix) appeared to be inversely related to the diameter of the particles, whereas the emission intensity of Co, Mn and Cd (constrained to surface) appeared to be a function of the surface concentration of analyte. These results were consistent with partial volatilization of the particles.

銅の光電効果及びその薄膜による光の吸収と,價電子エネルギー準位との關係について(第II, 2報)

In the previous paper, (this jour.), the relative positions of energy level, E1, E2, E3 and E4, in Cu, were determined from X-ray spectrum. In the present work, the above results were compared with the photoelectric effects and the light absorption in its thin film, and the results are as shown in the following table; similar results had previously been already obtained for Zn. _??_ From these results it was inferred that the threshold energies in the photoelectric effect for (100) and for (111), of Cu, are equal to the energy distances E2-E4 and E2-E3, respectively. Further, the result above inferred, was combined to the experimental result obtained by T. Fukuroi, saying that the threshold energy of fhe photoconductive effect of the thin film of metals, Zn, Cd and Hg, is equal to that of the ordinary photoelectric effect for the same element, it was inferred that, the high resistivity of the thin film of metals comes from the fact that, in such a film, the levels, E3 and E4 are rarely occupied by electrons while E1 and E2, constantly; accordingly E3 and E4 are conduction levels but not E1 and E2. Furthermore, it was taken as that, the thin surface layer of bulk mass of a metal has a similar electronic structure as above described. So, when the exciting energy amounts to its threshold value, the electron in E2 is elevated to E3 or E4 in both cases; and there occcurs electric conduction in the thin film, and photoelectron emission, from the surface layer of the bulk mass, of the metal. Therefor it was concluded that the mechanism of the releasing of electron from the level, E3 or E4, is the same in both cases, and so also in the case of electric conduction within the bulk mass of metals, asserting that, it is no other than the authoionization which is well observed in free atoms and in free molecules. Accordingly that within the bulk mass of Cu, valency electrons are in E1, E2, E3, and E4; but in its thin surface layer, E3, E4 are rarely and E1, E2 constantly, occupied by electrons.