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The Impact of Sampling Approach and Daily Water Usage on Lead Levels Measured at the Tap
Citation:
Lytle, D., C. Formal, K. Cahalan, C. Muhlen, AND S. Triantafyllidou. The Impact of Sampling Approach and Daily Water Usage on Lead Levels Measured at the Tap. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 197:117071, (2021). https://doi.org/10.1016/j.watres.2021.117071
Impact/Purpose:
Many reasons exist to sample drinking water for lead (Pb) (e.g., regulatory, remediation, or exposure assessment), and many sampling approaches are available. Selecting the best approach for its intended use is critical. To that end, the objective of this work was to compare Pb levels in water collected by multiple sampling approaches, from a model home plumbing system (HPS) that included an old Pb service line (LSL), as a function of daily water usage. Specifically, flushed, direct LSL, sequential profile, random daytime (RDT), first draw, manual composite and particle/soluble Pb samples were compared over 30 months. The HPS was designed to represent a typical household of four people, and a broad range of daily water usage spanning from 1.4 to 120 gallons/day. Pb levels in water collected directly from the LSL reached equilibrium after 7 to 15.5 hours of stagnation, and approximately 55% of the equilibrium Pb concentration was reached after 2 hours. Sequential sampling accurately identified the LSL; however, the peak profile Pb concentrations at four sampling taps were a fraction of the Pb measured directly from the LSL, depending on the tap’s distance from the LSL. Therefore, Pb solubility associated with LSL pipe scale minerals could not be estimated directly from the profiling sampling. Daily water usage patterns greatly impacted total Pb levels in all water sampling approaches, although manual composite and RDT samples were more sensitive to changes. Manual composite and RDT samples were equal to or greater than first draw samples throughout the study, and differences grew larger as water usage decreased.
Description:
Many reasons exist to sample drinking water for lead (Pb) (e.g., regulatory, remediation, or exposure assessment), and many sampling approaches are available. Selecting the best approach for its intended use is critical. To that end, the objective of this work was to compare Pb levels in water collected by multiple sampling approaches, from a model home plumbing system (HPS) that included an old Pb service line (LSL), as a function of daily water usage. Specifically, flushed, direct LSL, sequential profile, random daytime (RDT), first draw, manual composite and particle/soluble Pb samples were compared over 30 months. The HPS was designed to represent a typical household of four people, and a broad range of daily water usage spanning from 1.4 to 120 gallons/day. Pb levels in water collected directly from the LSL reached equilibrium after 7 to 15.5 hours of stagnation, and approximately 55% of the equilibrium Pb concentration was reached after 2 hours. Sequential sampling accurately identified the LSL; however, the peak profile Pb concentrations at four sampling taps were a fraction of the Pb measured directly from the LSL, depending on the tap’s distance from the LSL. Therefore, Pb solubility associated with LSL pipe scale minerals could not be estimated directly from the profiling sampling. Daily water usage patterns greatly impacted total Pb levels in all water sampling approaches, although manual composite and RDT samples were more sensitive to changes. Manual composite and RDT samples were equal to or greater than first draw samples throughout the study, and differences grew larger as water usage decreased.
URLs/Downloads:
DOI: The Impact of Sampling Approach and Daily Water Usage on Lead Levels Measured at the Tap
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