Abstract
Phosphate dosing of drinking water supplies, coupled with leakage from distribution networks, represents a significant input of phosphorus to the environment. The oxygen isotope composition of phosphate (δ(18)OPO4), a novel stable isotope tracer for phosphorus, offers new opportunities to understand the importance of phosphorus derived from sources such as drinking water. We report the first assessment of δ(18)OPO4 within drinking water supplies. A total of 40 samples from phosphate-dosed distribution networks were analyzed from across England and Wales. In addition, samples of the source orthophosphoric acid used for dosing were also analyzed. Two distinct isotopic signatures for drinking water were identified (average = +13.2 or +19.7‰), primarily determined by δ(18)OPO4 of the source acid (average = +12.4 or +19.7‰). Dependent upon the source acid used, drinking water δ(18)OPO4 appears isotopically distinct from a number of other phosphorus sources. Isotopic offsets from the source acid ranging from -0.9 to +2.8‰ were observed. There was little evidence that equilibrium isotope fractionation dominated within the networks, with offsets from temperature-dependent equilibrium ranging from -4.8 to +4.2‰. While partial equilibrium fractionation may have occurred, kinetic effects associated with microbial uptake of phosphorus or abiotic sorption and dissolution reactions may also contribute to δ(18)OPO4 within drinking water supplies.
Highlights
In many developed countries, legacy lead piping is a major source of lead contamination in drinking water,[1,2] which has been associated with reduced cognitive development in young children[3,4] and an increased risk of coronary heart disease or stroke because of increased blood pressure.[5,6] Public water utilities in the U.K. and parts of Europe and North America routinely dose drinking water supplies with phosphate to prevent pipe corrosion and the dissolution of lead
Inorganic phosphate is dosed to drinking water supplies, leading to the formation of lead phosphate or calcium phosphate precipitates on the inside of service lines and household plumbing. These precipitates have lower solubility than lead corrosion products that otherwise line the inside of drinking water supply pipes, thereby reducing the concentration of lead in solution alongside the concentration of other solutes derived from pipe corrosion products, including copper.[7]
A sampling transect running for 7 km from the point of water entry into the drinking water distribution network was established at one site in the southeast of England
Summary
Legacy lead piping is a major source of lead contamination in drinking water,[1,2] which has been associated with reduced cognitive development in young children[3,4] and an increased risk of coronary heart disease or stroke because of increased blood pressure.[5,6] Public water utilities in the U.K. and parts of Europe and North America routinely dose drinking water supplies with phosphate to prevent pipe corrosion and the dissolution of lead. Isotope fractionation of the oxygen atoms in phosphate ions only occurs at a typical Earth surface water temperature and pressure by enzyme-mediated biochemical reactions.[26] In particular, intracellular metabolic reactions catalyzed by the inorganic pyrophosphatase enzyme lead to rapid, temperature-dependent equilibrium between oxygen in phosphate and oxygen within the intracellular fluid The latter is expected to be identical in oxygen isotope composition to water oxygen (δ18OH2O) in the extracellular environment. This paper reports data from a wide range of drinking water supplies in England and Wales to evaluate these hypotheses and contribute to the global library of δ18OPO4 for a range of P sources within the environment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
