Citation:

SCHOCK, M. R., R. N. Hyland, AND M. M. Welch. The Occurrence of Contaminant Accumulation in Lead Pipe Scales from Domestic Drinking Water Distribution Systems-ABSTRACT. Presented at HEALTH CANADA ENVIRONMENTAL AND OCCUPATIONAL AND OCCUPATIONAL TOXICOLOGY (EOT) SEMINAR SERIES, Ottawa, ON, CANADA, March 05, 2008.

Impact/Purpose:

Present at workshop

Description:

Previous work has shown that contaminants such as Al, As and Ra, can accumulate in drinking water distribution system solids. The release of accumulated contaminants back into the water supply could conceivably result in elevated levels at consumers’ taps. The current regulatory and typical monitoring practices are not designed in a way to detect such episodes of release. Thus, the magnitude of any problem that might exist is almost completely unknown. The objective of this study was to determine the occurrence of a broad suite of inorganic contaminants in distribution system lead service line scales, using different quantitative elemental analysis techniques. These techniques included multi-acid digestion or sintering decomposition followed by ICP-OES or ICP-MS, and total sulfur and carbon by combustion. A small number of samples were analyzed for mercury. Contaminants were categorized by average concentrations in samples. The frequency distributions of the individual contaminants were developed, and they were put into 4 categories depending on their average concentrations: minimal (0 – 99 mg/kg); minor (100-999 mg/kg); moderate (1000-9,999 mg/kg); and predominant (≥ 10,000 mg/kg). The contaminants Cu, S, Sn, V and Zn, which compose the moderate contaminants group, were all present in scale samples. Samples contained Cu concentrations as high as 42,600 mg/kg, S concentrations as high as 5972 mg/kg, Sn concentrations as high as 9,440 mg/kg, V concentrations as high as 22,000 mg/kg, and Zn concentrations as high as 24,700 mg/kg. In the “predominant” group for these water systems were aluminum, iron, manganese, and of course, lead. Al concentrations ranged as high as 44,000 mg/kg, Fe concentrations as high as 578,000 mg/kg, Mn concentrations as high as 177,200 mg/kg, and Pb concentrations as high as 915,000 mg/kg. Although this study was based on “samples of opportunity”, rather than a statistically-determined survey, it clearly establishes that many contaminants are present at concentrations that could possibly pose a risk to consumers if released back into the water. This provides a solid justification for future research on the mineralogy and speciation of the contaminants present in the scales, and their sensitivity and susceptibility to mobilization by different water chemistry changes.

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