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The dissolution of lead corrosion products that are present as scales on lead pipes indistribution systems can be a source of lead to drinking water. Corrosion products that developin pipe scales include lead(II) oxides, carbonates, and phosphates as well as lead(IV) oxideswhen high concentrations of free chlorine are present. Changes in treatment processes thatinfluence the distribution system water chemistry have the potential to enhance or inhibit thedissolution of lead-containing corrosion products. The dissolution rates of three lead-containingsolids that have been observed in distribution systems have been systematically measured as afunction of important water chemistry parameters. The lead corrosion products studied are lead(II) carbonate hydrocerussite, lead(II) phosphate hydroxylpyromorphite, and lead(IV)oxide plattnerite. Dissolution rates were varied as a function of pH, dissolved inorganic carbon,orthophosphate concentration, and the presence or absence of monochloramine. The dissolutionrates of all three corrosion products were strongly influenced by pH. The presence of phosphatedramatically decreased the dissolution rate of all three phases; for hydrocerussite, the addition ofphosphate induced the gradual transformation of a lead(II) carbonate solid into a lead(II)phosphate solid. The influence of dissolved inorganic carbon was more complex. Includes 5 references, figure.

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Edition: Vol. - No. Published: 11/01/2009 Number of Pages: 6File Size: 1 file , 780 KB