Copper, speciation

Taking into account the physicochemical similarities between complexation and adsorption reaction mechanisms, one can conclude that divalent copper ions are the most strongly sorbing of the various trace metals. This species can sorb onto both inorganic and organic solids. Sorption of copper onto oxides and clays has been investigated extensively (see Box 1). 

Copper and zinc sorption in soil (after Pampura, 1997) 

In accordance with modern theories, the main mechanism of metal sorption in various soils is the heterogenic surface sorption of metals by soil particles. In the sorption process, the various metals react with different functional groups of various soil compounds, like clay minerals, organic matter, oxides of Fe, Mn, Al, Si, etc. Various mechanisms of Me sorption in soil and soil solution are connected with various forms of their existence in soil such as exchangeable, specifically sorbed, occluded by oxides and hydroxides, bounded with organic matter and included into interlayer spaces of silicon minerals. In this study Tessier et al (1979) s method has been 

Extractant Extraction duration, h Extracted metal forms 

H2O2/HNO3, pH 2 and then CH3COONH4 5.5 Organic matter bounded, Meo,g 

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Dumestre, A., Sauve, S., McBride, M., Baveye, P. and Berthelin, J. (1999). Copper speciation and microbial activity in long-term contaminated soils , Archives of Environmental Contamination and Toxicology, 36, 124-131. 

Ruzic [278 ] considered the theoretical aspects of the direct titration of copper in seawaters and the information this technique provides regarding copper speciation. The method is based on a graph of the ratio between the free and bound metal concentration versus the free metal concentration. The application of this method, which is based on a 1 1 complex formation model, is discussed with respect to trace metal speciation in natural waters. Procedures for interpretation of experimental results are proposed for those cases in which two types of complexes with different conditional stability constants are formed, or om which the metal is adsorbed on colloidal particles. The advantages of the method in comparison with earlier methods are presented theoretically and illustrated with some experiments on copper (II) in seawater. The limitations of the method are also discussed. 

Garcia-Monco Carra et al. [296] have described a hybrid mercury film electrode for the voltammetric analysis of copper (and lead) in acidified seawater. Mercury plating conditions for preparing a consistently reproducible mercury film electrode on a glassy carbon substrate in acid media are evaluated. It is found that a hybrid electrode , i.e., one preplated with mercury and then replated with mercury in situ with the sample, gives very reproducible results in the analysis of copper in seawater. Consistently reproducible electrode performance allows for the calculation of a cell constant and prediction of the slopes of standard addition plots, useful parameters in the study of copper speciation in seawater. 

Spokes, L.J., Campos, M.LA.M. and Jickells, T.D. (1996) The role of organic matter in controlling copper speciation in precipitation. Atmos. Environ., 30, 3959-3966. 

Bjorklund, L.B. and Morrison, G.M. (1997) Determination of copper speciation in freshwater samples through SPE-spectrophotometry.Amj/. Chim. Acta, 343, 259-266. 

Copper speciation in water was investigated by means of spectrophotometry of Cu+-bathocuprine complex formation (Bjoerklund and Morrison, 1997). The complex was separated by means of solid-phase extraction on PTFE-supported octadecyl (Qg) bonded silica discs. The discs provided rapid filtration and contributed low blanks. After filtration, the copper complex was eluted, and the copper concentration was measured by spectrophotometry. Total copper concentrations in the samples were measured after UV irradiation. The bathocuprine-available copper detection limits (for 500 ml samples) were 0.4 and 3.8 mg dm-3 copper for pure and polluted water, respectively. 

Titrations were performed on untreated, filtered, and UV-treated filtered river water samples at in situ and adjusted pH values. The effect of pH on copper speciation was investigated by titration of filtered Newport River water at pH 7.0 and filtered Newport and Neuse waters at pH 8.0. Newport River water was adjusted to pH 7.0 by decreasing the partial pressure of CO2 from the initial ambient value of about 10 times the atmospheric level. To adjust the pH to 8.0, sodium bicarbonate was added to bring the river water samples to a concentration of 0.5 mM with subsequent adjustment of Pc02 Titrations were also conducted at pH 7,0 in model solutions consisting of 0.01 KNO3 and 0.1 mM NaHC03 with and without the addition of 0.75 histidine to test electrode behavior in solutions of known chemistry. 

Chemical Speciation Models. Using the stability constants derived by us for copper complexes with hydroxo and carbonate ligands (Table I) and for natural organic ligands (Table II), the Newport and Neuse Rivers were modeled for copper speciation as a function of pH, total copper, carbonate alkalinity and total dissolved organic matter. Speciation models were calculated from the equation ... 

In my laboratory we studied the effect of copper on whole cells of meth-anotrophs. These experiments involved growing different pure cultures of methanotrophs in medium containing different initial amounts of copper, added as copper sulfate, as described previously (9), and analyzing both growth rate and methane oxidation kinetics. We did not measure free copper in these experiments, so the effects noted have not yet been correlated to copper speciation but rather to total copper added at the start of growth. 

These findings have important implications for methane oxidation in natural samples. First, they suggest that the pMMO is the predominant enzyme system for methane oxidation in natural populations and thus provide more impetus for understanding this enzyme system. Second, the response of natural populations to changes in methane concentrations will most likely depend on a complex set of parameters, of which available copper concentration may be the key. It is now important to study how methanotrophs utilize copper and how they respond to changes in copper and methane concentrations and to copper speciation, in order to predict how natural populations will respond to environmental perturbations. 

Breault, R.F., Colman, J.A., Aiken, G.R. and McKnight, D. (1996) Copper speciation and binding by organic matter in copper-contaminated stream water. Environ. Sci. Technol., 30, 3477-3486. 

Ortiz-Viana, M. M., da Salva, M. P., Agraz, R., Procopio, J. R., Sevilla, M. T., and Hernandez. L. (1999). Comparison of two kinetic approaches for copper speciation using ion-exchange modified carbon paste electrodes. Anal. Chim. Acta 382, 179-188. 

The Cu(I)-bathocuproine complex retained on the solid-phase extractant can be used for copper speciation in fresh water [6]. Second derivative spectrophotometry using mixtures of ligands, 5-phenyl-3-(4-phenyl-2-pyridinyl)-l,2,4-triazine and bathocuproine, was used for simultaneous determination of copper and iron in tap and river water [7]. 

Parthasarathy N, Buffle J, Capabilities of supported liquid membrane for metal speciation in natural waters application to copper speciation. Anal. Chim. Acta 1994 284 649-659. 

The strength of the copper-organic bond and the well-established dual potential of copper as a biological stimulant or inhibitor has led to many studies of the effect of copper speciation on growth. A few of these studies, showing that strong organic... 

Figure 2. Copper Speciation in Ground Water from Well 3 Computed Using the Complexation Parameters Determined by ISE and CSV. S CuL is Organically Complexed Cu.

A very large amount of information is available on the levels of total copper in various compartments of the environment, but little information on copper speciation (WHO 1998). Copper is transformed in the environment to forms that are either more or less bioavailable, depending upon the physical and chemical conditions present in the environment of interest. The net uptake of copper by microorganisms, plants, and animals from the surrounding environment (water, sediment, soil, and diet) is defined as bioaccumulation . The species of copper present in environmental media and its associated bioavailability, together with differences in plant and animal uptake and excretion rates, determine the extent of bioaccumulation. 

Copper speciation in vapor-phase fluid inclusions. The X-ray microprobe is valuable in studying the chemistry of intact fluid inclusions. Much of the work focuses on determining the chemical compositions of inclusions (Mavrogenes et al. 1995 Hayashi and Iida 2001 Menez et al. 2001 Philippot et a. 2001 Vanko et al. 2001) but chemical speciation studies using pXAFS have also become fruitful (Anderson et al. 1995, 1998 Mavrogenes et al. 2002). 

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