The concentration of lead in drinking water correlates with that in blood. Higher levels of lead in the blood are associated with learning deficits and neurobehavioral disorders in children. Lead service lines (LSLs) are a major source of drinking water lead. To control drinking water lead, often an orthophosphate-based corrosion inhibitor is added. Lead phosphate minerals have a low solubility at neutral pH and can act as a passivating film, separating lead from the aqueous environment.
Benjamin F. Trueman and Graham A. Gagnon, Dalhousie University, Halifax, Canada, investigated lead−iron interactions in drinking water systems, which can be important when lead pipes are supplied by an iron main line. The team built a model distribution system out of pipes and analyzed the water with size-exclusion chromatography with inductively coupled plasma mass spectrometry (ICP-MS) detection. Lead release was on average 96 μg L–1 higher from LSLs supplied by corroded iron pipes compared to those supplied by PVC pipes.
The researchers explored the galvanic corrosion of lead by semiconducting iron oxide particles as a possible mechanism for this increased lead release. When galvanic cells with lead and magnetite (Fe3O4) electrodes were short-circuited, lead release increased 8-fold. Doubling the orthophosphate concentration reduced the average lead release slightly, but did not significantly reduce the effect of an upstream iron main.
- Understanding the Role of Particulate Iron in Lead Release to Drinking Water,
Benjamin F. Trueman, Graham A. Gagnon,
Environ. Sci. Technol. 2016.