Industrial zinc mobilization

Zinc ligands are soluble in neutral and acidic solutions, so that zinc is readily transported in most natural waters (USEPA 1980, 1987), but zinc oxide, the compound most commonly used in industry, has a low solubility in most solvents (Elinder 1986). Zinc mobility in aquatic ecosystems is a function of the composition of suspended and bed sediments, dissolved and particulate iron and manganese concentrations, pH, salinity, concentrations of complexing ligands, and the concentration of zinc (USEPA 1980). In freshwater, zinc is most soluble at low pH and low alkalinity 10 mg Zn/L of solution at pH 6 that declines to 6.5 at pH 7, 0.65 at pH 8, and 0.01 mg/L at pH 9 (Spear 1981). Dissolved zinc rarely exceeds 40 pg/L in Canadian rivers and lakes higher concentrations are usually associated with zinc-enriched ore deposits and anthropogenic activities. Marine... 

Of the total quantity of thallium mobilized by industry amounting to about 1600 tons in the United States during 1977, 70% was reemitted to the environment either in the form of air pollution (15%) or as solid waste (55%). Coal burning power plants account for the greater part of this air pollution, but the smelting of copper, zinc, and lead may also result in concentrated local emissions. The remaining 30% is incorporated in the final products, though usually at a lower level than in the raw materials. ... 

Jinzu Valley, Japan. One of the most infamous cases of contaminated land and health occurred in Japan and the effects were most prominent immediately after the Second World War. Around the end of the 19th century, soils in the Jinzu River basin, part of the Toyama prefecture, became contaminated with cadmium as a result of activities upstream at the Kamioka mines. The main activity at this mine was the mining and processing of zinc (cadmium is often associated with zinc ores) with the result that wastewater rich in heavy metals was discharged into the Jinzu River. Contaminants from this industry moved down-stream and caused contamination of soils in paddy fields as a result of abstraction of river water into fields in order to cultivate the local rice crop. Under favourable conditions, cadmium can be a fairly mobile heavy metal, particularly in soils with low pH, and increases in soil cadmium can often result in an increase in the uptake of cadmium by plants. This in turn results in an increase in dietary exposure and the consumption of contaminated agricultural crops can be a major pathway of human exposure. 

Stationary phase 0.1% Thorium nitrate impregnated silica layer. Mobile phase 1.0 M Aqueous sodium formate solution (pH 7.65). Detection 0.1% Dithizone in CCL for Zn " and Cd hydrogen sulfide gas for TD and Hg ". Conditions Ascending technique, run 10 cm. layer thickness 0.25 mm, plate activation at 100° for I h, loading volume 0.01 ml of 1% test solution, pH value of spiked industrial wastewater and seawater were 1.5 and 8.3 respectively. Remarks Th -impregnated silica layers were found useful for the detection and separation of zinc, cadmium, mercury, and thallium from industrial wastewater and seawater in the presence of common pesticides. 

Metals such as zinc, cadmium and mercury are often more mobile at industrially contaminated sites than copper, nickel and lead (Fig. lb shows their general mobility fields). This is because they can form aqueous complexes with chloride, carbonate and hydroxide, even where these ligands are present at the modest levels often found at contaminated sites. Such complexes are often only weakly sorbed to solids. 

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