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Trace Metal Associations with Manganese-Rich Surface Coatings of Lead Service Lines
Citation:
Welch, M. M., M. R. SCHOCK, M. K. DeSantis, AND A. Burkes. Trace Metal Associations with Manganese-Rich Surface Coatings of Lead Service Lines. Presented at AWWA Inorganic Contaminants Workshop, Denver, CO, February 28 - March 02, 2010.
Impact/Purpose:
To inform the public.
Description:
Analysis of lead service line samples from U. S. Environmental Protection Agency’s long-term research program to evaluate control and metal release from domestic drinking water service lines has revealed that Manganese-rich solids also contain Iron and sometimes Aluminum have frequently been found as the major surface layers in contact with drinking water. The scale layers present on these pipes were photographed, selectively scraped to isolate scale layers, and subjected to powder XRD, SEM, total C, total S, and ICP (emission and sometimes MS) analyses. The Mn solids are almost universally X-ray amorphous and are commonly found associated with Pb (II) carbonates and other Pb(II) minerals within and underlying the Mn-rich surface coatings. Manganese oxyhydroxide solids are also widely reported to be effective scavengers of numerous trace metals. Potential-pH and solubility diagrams indicate Mn is insoluble in highly oxidized conditions at a pH of ~8 or greater, conditions that are also conducive to forming Pb(IV) minerals. Formation conditions for these Mn solids are also expected to generally apply to large-diameter distribution mains, and other materials. This paper uses a variety of statistical and graphical techniques to investigate more thoroughly associations among various trace constituents and the surficial coatings on the lead pipes; possible impacts on lead solid mineralogy; and to provide suggestions and hypotheses of the significance of distribution system redox conditions on the accumulation of trace metals in association with manganese-based coatings. This is also important information because particular trace metals could be an undetected consumer exposure source that differs among drinking water systems depending on the specific major elements that compose the interior pipe surfaces.
URLs/Downloads:
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FOR FURTHER INFORMATION_PRINCIPAL INVESTIGATOR.PDF (PDF, NA pp, 5 KB, about PDF)