TY - JOUR
T1 - Spherulitic Lead Calcium Apatite Minerals in Lead Water Pipes Exposed to Phosphate-Dosed Tap Water
AU - Hopwood, Jeremy
AU - Casey, Helen
AU - Cussons, Martin
AU - Knott, Porsha
AU - Humphreys, Paul
AU - Andrews, Hayley
AU - Banks, Jenny
AU - Coleman, Stephen
AU - Haley, John
N1 - Funding Information:
This study was funded by Yorkshire Water, a major U.K. water utility. Yorkshire Water manages the collection, treatment, and distribution of 1.3 billion liters of drinking water per day to 5 million people in the North East of England. The authors thank Prof. Fiona Meldrum, Department of Chemistry, University of Leeds, and Dr. Alexander E. S. Van Driessche, CNRS, Université of Grenoble Alpes, for discussions on classical and non-classical crystal growth. The authors also thank Dr. Peter Cardew for discussions on the chemistry of lead pipe mineral scale.
Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.
PY - 2023/3/28
Y1 - 2023/3/28
N2 - Phosphate dosing is the principle strategy used in the United Kingdom to reduce the concentration of lead in tap waters supplied by lead water pipes. The mechanisms of phosphate-mediated lead control are not fully understood, but solid solutions of lead calcium apatite are thought to play an important role. This study investigated the microstructure of a lead pipe, supplied with high-alkalinity tap water, in which the lead calcium apatite crystals were spherulitic having rounded and dumb-bell-shaped morphologies. XRD, Fourier transform infrared spectroscopy, optical microscopy, Raman spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy showed that the lead pipe had a well-established inner layer of litharge; a middle layer containing lead calcium apatite spherulites, plumbonacrite, and some hydrocerussite; and an outer layer containing iron, lead, phosphorus, calcium, silicon, and aluminum. It was found that spherulitic lead calcium apatite could be grown in the laboratory by adding hydrocerussite to synthetic soft and hard water-containing phosphate, chloride, and citrate ions at pH 5.5 but not when the citrate was absent. This suggests that dissolved organic molecules might play a role in spherulite formation on lead water pipes. These molecules might inhibit the formation of lead calcium apatite, reducing the effectiveness of phosphate dosing in lead water pipes.
AB - Phosphate dosing is the principle strategy used in the United Kingdom to reduce the concentration of lead in tap waters supplied by lead water pipes. The mechanisms of phosphate-mediated lead control are not fully understood, but solid solutions of lead calcium apatite are thought to play an important role. This study investigated the microstructure of a lead pipe, supplied with high-alkalinity tap water, in which the lead calcium apatite crystals were spherulitic having rounded and dumb-bell-shaped morphologies. XRD, Fourier transform infrared spectroscopy, optical microscopy, Raman spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy showed that the lead pipe had a well-established inner layer of litharge; a middle layer containing lead calcium apatite spherulites, plumbonacrite, and some hydrocerussite; and an outer layer containing iron, lead, phosphorus, calcium, silicon, and aluminum. It was found that spherulitic lead calcium apatite could be grown in the laboratory by adding hydrocerussite to synthetic soft and hard water-containing phosphate, chloride, and citrate ions at pH 5.5 but not when the citrate was absent. This suggests that dissolved organic molecules might play a role in spherulite formation on lead water pipes. These molecules might inhibit the formation of lead calcium apatite, reducing the effectiveness of phosphate dosing in lead water pipes.
KW - lead pipe
KW - plumbosolvency
KW - spherulite
KW - apatite
KW - tap water
KW - phosphate mineral
KW - crystallization
KW - phosphate
KW - mineral
UR - http://www.scopus.com/inward/record.url?scp=85150351668&partnerID=8YFLogxK
U2 - 10.1021/acs.est.2c04538
DO - 10.1021/acs.est.2c04538
M3 - Article
VL - 57
SP - 4796
EP - 4805
JO - Environmental Science & Technology
JF - Environmental Science & Technology
SN - 0013-936X
IS - 12
ER -
