Fluxes of metals

Aogaki et al,63-77 first examined from both theoretical and experimental viewpoints the morphological instability in which the mass flux of metal ions produced by shifting of the electrode potential to the less noble... 

Flux of metal atoms (or of metal vacancies in reverse direction)... 

Figure 6.17. Relationships between the initial (the first day) fluxes of metals in the soluble plus exchangeable fraction and metal loading levels in Israeli soils. Soils received metal nitrates and were incubated in the saturated-paste (SP) and field capacity (FC) moisture regimes...

In forest ecosystems these symbols stand for CL(M) is critical load of a heavy metal (g ha-1 a-1) Mu is metal net uptake in wood biomass under critical loads conditions (g ha-1 a 1) Mle(crit) is critical leaching flux of metal with drainage water (from the uppermost 10 cm soil layer) (g ha-1 a-1). 

In the particular case dealt with now (fully labile complexation), due to the linearity of a combined diffusion equation for DmCm + DmlL ml, the flux in equation (65) can still be seen as the sum of the independent diffusional fluxes of metal and complex, each contribution depending on the difference between the surface and bulk concentration value of each species. But equation (66) warns against using just a rescaling factor for the total metal or for the free metal alone. In general, if the diffusion is coupled with some nonlinear process, the resulting flux is not proportional to bulk-to-surface differences, and this complicates the use of mass transfer coefficients (see ref. [II] or Chapter 3 in this volume). 

Hamilton-Taylor, J., M. Willis, and C. S. Reynolds (1984), "Depositional Fluxes of Metals and Phytoplankton in Windermere as Measured by Sediment Traps", Limnot. Oceanogr.24, 695-710. 

The estimation of the release fluxes of metals from a hypothetical glassfill and a hypothetical glassroad will be based on experimental results and theoretical but realistic considerations. 

On most corroding metals, the above reactions occur at an oxidized surface and, depending on the peroperties of the surface layer, passivation may occur by which the kinetics of metal dissolution are substantially supressed either by ohmic, ionic, or electronic transport at a surface passivating film or by electrocatalytic hindrance. In passivation phenomena, a steady state with a balance between the formation and dissolution of the surface film takes place. As a result, the ionic flux of metal ions dissolving through the passivating film is highly reduced. 

This equation shows the coupling effect between the metal ion [M] and the hydrogen ion [H] because both appear in the concentration term of the Fick s law expression linked by the equilibrium reaction constant K. Thus, there will be a positive uphill flux of metal ion from the downstream to the upstream solution (that is, in the direction l o) as long as... 

The habitats available were disparate. Examples include hydrothermal high-tempera-ture (>85 °C) settings moderate thermophile settings (—40 °C) on the fringes of hot areas, or in cooler, probably more alkaline springs very cool (—0 °C) water distal to hydrothermal vents but in the flux of metals and geochemical contrasts from hydrothermal plumes in tidal waters where... 

Buat-Menard, P. E. (1985) Fluxes of Metals Through the Atmosphere and Oceans. In Changing Metal Cycles and Human Health, J. O. Nriagu, Ed., Dahlem Konferen-zen. Springer-Verlag, Beriin, pp. 43-69. 

German, C.R. and Angel, M.V. (1995) Hydrothermal fluxes of metals to the oceans a comparison with anthropogenic discharge, in Hydrothermal Vents and Processes (eds L.M. Parson, C.L. Walker and D.R. Dixon), Geological Society Special Publication No. 87, pp. 365-372. 

A reference electrode scanned along the metal surface will measure the series of (E"x)n and (E"M)n interface potentials. From these values, solution potentials (t))s) at the metal/solution interface may be calculated (< )s = -E") and presented as in Fig. 4.6. When the anodic and cathodic sites are microscopic relative to the size and position of the reference electrode, identity of the anodic and cathodic sites on a macroscale is lost, and a single mixed or corrosion potential, Ecorr, is measured as discussed previously. There is essentially a uniform flux of metal ions from the surface, and cathodic reactants to the surface, which constitute anodic and cathodic currents. Since the relative areas to which these currents apply usually are not known, the total area is taken as the effective area for each reaction. It is these currents, however, that mutually polarize the anodic reaction potential from E M up to Ecorr and the cathodic reaction potential from E x down to Ecorr. 

Scaling the measured Pb atmospheric flux in the region to the total atmospheric flux of metals over the past 100 years as determined in a salt marsh, the relative contributions of atmospheric and stream and sewage supply of metals to the Sound sediment can be estimated. In two cores so analyzed, all of the lead is inferred to be of atmospheric origin and about half of the copper and zinc. These proportions can be expected to vary westward along the axis of the Sound as local source terms from municipal and industrial pollution become more important. 

Diffusion dialysis was initially applied in viscose rayon production to recover caustic soda using parchment paper as a membrane. Today the largest industrial utilization of diffusion dialysis is to recover acids or alkalis from waste acids and alkalis using anion or cation exchange membranes. Figure 6.28 shows the principle of diffusion dialysis for acid recovery from waste acid solution. The process and membrane performance are evaluated on the basis of the flux of acids or alkalis (dialysis coefficient) and the ratio of the flux of metal salt to that of acids or alkalis (separation coefficient). The total dialysis coefficient [molh-1 m 2 (moll-1)], Uo, is defined by... 

By way of example, let us consider the simple electrolytic cell of Fig. 6.1.1, containing a motionless dilute binary metal electrolyte. We wish to determine the current-voltage characteristic of the cell, that is, the concentration polarization. To do this, we must calculate the flux of metal ions (cations) arriving at the cathode and depositing on it. As noted above, we assume that the overall rate of... 

Table 1 Fluxes of metals to the atmosphere from natural and anthropogenic sources. The interference factor is the ratio of the anthropogenic flux to the natural flux. The generic term combustion refers to various combinations of coal, oil, and wood combustion and refuse incineration...

The flux of metal atoms in vacuum (Pd, Sn, Al, Ti, Zn), evaporated from a bulk sample condenses onto a cooled substrate together with the monomer. The condensate consists of nanoparticles of the metal and the monomer (Fig. 1). Upon heating the substrate to ambient temperature the monomer polymerises to PPX. The structure thus obtained is a porous matrix with dispersed nanoparticles in it. The properties of these nanocomposites containing metal and/or metal-oxide nanoparticles in the polymeric matrix are presented. Manipulation of the synthesis conditions, i.e., the distance between the vapour source and the substrate, the tilt angle of the beam, and the deposition time allowed for optimising the deposition regime. Measuring the electrical resistance of the condensate and composite permitted the control of the film formation in relation to the oxidation behaviour. 

Assume the electrolyte to be quiescent, and electrodes to be infinite planes. Then the problem may be reduced to determination of the flux of metal ions (cations) to the cathode. The electric current density is i = Fz+jl. Using expressions (5.85) for molar fluxes jf under the condition u = 0, we get ... 

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