Seasonal Variations in Lead Release to Potable Water

摘要

The influence of temperature on the solubility of representative lead solids present in drinking-water systems and the lead release to potable water was examined. Temperature had surprisingly little effect on the dissolution of cerrusite, hydrocerussite, chloropyromorphite, lead ortho-phosphate, and lead oxide solids; however, in the presence of natural organic matter, lead oxide dissolution was 36 times greater (36 versus 1277 ppb) at 20 ℃ compared to 4 ℃ due to accelerated reductive dissolution. The solubility of plumbonacrite was three times higher at 20 ℃ compared to 4 ℃ (260 versus 92 ppb). In full-scale pipe rigs using harvested lead service lines in Washington, DC and Providence, RI, dissolved lead release increased by as much as 2-3 times, and particulate lead increased 2-6 times in the summer versus winter. In four of the eight homes sampled in Providence, RI, dissolved lead levels were three times higher during the summer compared to the winter, and five homes had copper levels that were 2.5-15 times greater in the winter. These studies demonstrate a need to better understand how lead service line scales vary because patterns of release and temperature dependency sometimes vary markedly, even within the same distribution system.