Water speciation

Wallace P.J., Dufek J., Anderson A.T., and Zhang Y. (2003) Cooling rates of Plinian-fall and pyroclastic-flow deposits in the Bishop Tuff inferences from water speciation in quartz-hosted glass inclusions. Bull. Volcanol. 65, 105-123. 

Demianov, P D. DeStefano, A. Gianguzza, and S. Sammartano, Equilibrium studies in natural waters Speciation of phenolic compounds in synthetic seawater at different salinities , Environ. Toxicol. Chem, 14,767-773 (1995). 

Exactly what is the analytical problem and what is the minimum analytical information needed to provide a reasonable answer In this connection it is well to categorize the type of analysis desired oxyhalides in drinking water, arsenic speciation in drinking water, speciation of chromium in plating baths, etc. 

Numerous species, OIT, H, H2O, etc., have been suggested as potential candidates in the diffusion process involving water. Zhang et al. (1991a) described an expression for the apparenf diffusivity of total oxygen in a solid (crystal, glass) or melt (D o) as a function of water speciation given here as... 

The thermodynamic data compilations of Sillen and Martell catalyzed rapid advances in equilibrium models of seawater speciation. These works were followed by additional compilations that were critically important to modern sea-water speciation assessments. In view of these developments, and additional extensive experimental analyses appropriate to seawater. Principal Species assessments ten to fifteen years after the pioneering work of Sillen demonstrated a much improved awareness of the importance of hydrolysis in elemental speciation. 

In aquatic sediments or soils, there are also a range of trace elements species ranging from ions exchanged to particles, to those bound to organic matter or in various inorganic forms (e.g., oxides, carbonates, sulfides) or as more inert crystalline mineral phases. As in waters, speciation studies in soils and sediments are generally undertaken to better understand the bioavailability of toxic substances and to investigate transport pathways to and from other parts of the ecosystem. Sediment and soil pore waters (soil solutions) are of particular interest because they are in equilibrium with the solid phase and are the medium for contaminant uptake by plants and many other biota. The techniques used for speciation analysis in these aqueous samples differ little from those for waters. 

The saturation indices discussed previously can be calculated based upon total analytical values for all possible reactants. Ions in water, however, do not tend to exist totally as free ions [21]. Calcium, for example, may be paired with sulfate, bicarbonate, carbonate, phosphate, and other species. Bound ions are not readily available for scale formation and such binding, or reduced availability of the reactants, decreases the effective ion-activity product Saturation indices such as the LSI are based upon total analytical values rather than free species primarily because of the intense calculation requirements for determining the distribution of species in water. Speciation breakdown of all species in a given water requires numerous computer iterations to achieve the following [22] ... 

Since the Minamata disaster in the 1950s, when hundreds of people were poisoned and several died because their fish diet was highly loaded with methylmercury, element species information has become of public interest. With the movie Erin Brokovich , a true story about a young woman who discovered chromium(VI) contamination of drinking water, speciation even made it into the cinema. ... 

Determine the speciation of each metal in this sample of sea water. 

A detailed review of the methods for deterrnination of low manganese concentration in water and waste is available (179). A review on the speciation of Mn in fresh waters has been reported (180). Reviews for the chemical analysis of Mn in seawater, soil and plants, and air are presented in References 181, 182, and 183, respectively. 

METHODOLOGICAL APPROACHES TO THE INVESTIGATION OF THE METAL SPECIATION IN THE NATURAL WATER... 

In this work ion-exchange and gel-permeation chromatography coupled with membrane filtration, photochemical oxidation of organic metal complexes and CL detection were applied to the study of the speciation of cobalt, copper, iron and vanadium in water from the Dnieper reservoirs and some rivers of Ukraine. The role of various groups of organic matters in the complexation of metals is established. 

A development of the study of adsorption currents is referred to as Tensammetry, and a useful review50 refers to the application of this technique to the examination of natural waters as an aid to speciation , the procedure for deciding how a metal ion is distributed between the various species in which the metal may be present. 

In Figure 2 the solubility and speciation of plutonium have been calculated, using stability data for the hydroxy and carbonate complexes in Table III and standard potentials from Table IV, for the waters indicted in Figure 2. Here, the various carbonate concentrations would correspond to an open system in equilibrium with air (b) and closed systems with a total carbonate concentration of 30 mg/liter (c,e) and 485 mg/liter (d,f), respectively. The two redox potentials would roughly correspond to water in equilibrium wit air (a-d cf 50) and systems buffered by an Fe(III)(s)/Fe(II)(s)-equilibrium (e,f), respectively. Thus, the natural span of carbonate concentrations and redox conditions is illustrated. 

Eh-pH diagram for the speciation of plutonium in equilibrium with Pu02 in water (10). 

Speciation of plutonium leached from the glass cubes is shown in Figure 1. The first bar represents the total amount of insoluble plutonium and is the summation of suspended plutonium (the difference between the values for filtered and unfiltered waters) and sorbed plutonium—viz., the amount removed from the cubes by a 0.1 M perchloric acid wash, normalized to the volumes of leachant solutions so that it is comparable to the other values in the graphs. For simplicity, the insoluble fractions are combined in one bar, whereas the various oxidation states in the soluble fraction are represented by separate bars. It should be noted that the ordinate scale varies among the graphs. 

Clevelend, J.M. Rees, T.F. Nash, K.L. "Plutonium Speciation in Selected Basalt, Granite, Shale, and Tuff Ground Waters", in press. 

The high concentration of oxygen in the atmosphere plays a central role in the photochemistry and chemical reactivity of the atmosphere. Atmospheric oxygen also defines the oxidation reduction potential of surface waters saturated with oxygen. The presence of oxygen defines the speciation of many other aquatic species in surface waters. 

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