Aging infrastructure has been identified as an issue that faces the Nation in the coming years. One such issue is legacy lead pipes used in drinking water distribution systems. The proposed project will advance the scientific and engineering basis for effective control of lead corrosion by developing a better and thorough understanding of lead-phosphate chemistry. The research is driven by: (a) evolving regulations for lead in drinking water, and, (b) unresolved scientific questions regarding the rates and mechanisms of lead phosphate nucleation, growth, aggregation, and deposition. The project will fill important knowledge gaps regarding the formation and stability of lead phosphate minerals and the molecular-level interfacial processes controlling lead phosphate precipitation.
State-of-the-art techniques will enable in situ quantification of the homogeneous (in solution) and heterogeneous (on substrates) nucleation of lead phosphates and their aggregation and deposition on pipe surfaces. The ability to observe and predict nucleation and to distinguish between homogeneous and heterogeneous nucleation is a remaining frontier in environmental chemistry. Advances in the understanding of colloidal and interfacial processes involving phosphate minerals can contribute to the fields of geology, materials science, and biomedical engineering as well as environmental engineering. The project will characterize the composition, structure, and in situ changes of the corrosion products that develop on existing scales after phosphate addition. This new knowledge will have direct relevance to lead corrosion control in water distribution systems, and it is also relevant to lead mobility in natural and engineered soil and aquatic systems. The team?s complementary expertise will help the project advance the infrastructure for environmental research by bringing nano-chemistry and mineralogy techniques to bear on important environmental engineering problems. The project objectives are to: (1) identify factors that control the homogeneous nucleation and aggregation of lead phosphates in solution and quantify the effects of water chemistry on those processes, (2) determine the rates of heterogeneous nucleation and deposition of lead phosphate particles on scales that form on pipe surfaces, and, (3) enable science-based optimization of phosphate application strategies that can be tailored to a particular water chemistry and scale type. The approach will build from fundamental studies of processes in solution and on surfaces, and, the consideration of processes occurring in intact pipes. This integrated approach will link advances in fundamental knowledge with important translational outcomes. A multi-scale approach will use atomic- and molecular-scale characterization techniques to yield mechanistic insights needed to interpret colloidal and interfacial processes responsible for the macroscopic uptake or release of lead from pipes. In addition to the potential impact of a better understanding lead (Pb) and phosphate chemistry, the proposed research will be integrated with educational activities that involve curriculum enrichment, student training, and outreach to K-12 students and the professional engineering community.
