Worth a Closer Look: Raman Spectra of Lead-Pipe Scale

Abstract

The identification and characterization of lead-bearing and associated minerals in scales on lead pipes are essential to understanding and predicting the mobilization of lead into drinking water. Despite its long-recognized usefulness in the unambiguous identification of crystalline and amorphous solids, distinguishing between polymorphic phases, and rapid and non-destructive analysis on the micrometer spatial scale, the Raman spectroscopy (RS) technique has been applied only occasionally in the analysis of scales in lead service lines (LSLs). This article illustrates multiple applications of RS not just for the identification of phases, but also compositional and structural characterization of scale materials in harvested lead pipes and experimental pipe-loop/recirculation systems. RS is shown to be a sensitive monitor of these characteristics through analyses on cross-sections of lead pipes, raw interior pipe walls, particulates captured in filters, and scrapings from pipes. RS proves to be especially sensitive to the state of crystallinity of scale phases (important to their solubility) and to the specific chemistry of phases precipitated upon the introduction of orthophosphate to the water system. It can be used effectively alone as well as in conjunction with more standard analytical techniques. By means of fiber-optic probes, RS has potential for in situ, real-time analysis within water-filled pipes.

Density Functional Theory-Based Thermodynamic Model for Stable Scale Formation in Lead-Water Systems

“…Additionally, the sources of consumable leadbioavailable soluble lead and particulatesmust be understood on the materials science length scale, whether from electrochemical ejection from the lead pipe, chemical dissolution of lead corrosion products and scales, or particulate spallation. Finally, due to the complexity of the flowing drinking water systems and the grave consequences associated with lead release predictions, experimental works should also continue to explore these same questions, like the role of calcium in lead film formation and the presence/absence of phosphate-based films . The most compelling framework involves computational modeling working in harmony with experimental analysis.…”

Release of Particulate Lead from Four Lead Corrosion Products in Drinking Water: A Laboratory Study Coupled with Microscopic Observations and Computational Fluid Dynamics

“…Metallic lead was found in all samples due to the fact that underneath metallic lead was unavoidably scratched during the scalpel collection process. Hydrocerussite was also found in the lead dioxide sample since free chlorine could oxidize metallic lead to first form lead carbonate minerals, in which the uppermost layer could be further oxidized by free chlorine to form lead dioxide. ,,, It has been reported that under typical drinking water conditions, it requires a long-term free chlorine exposure to transform amorphous lead dioxide to crystalline lead dioxide such as plattnerite. , In this study, a much higher free chlorine concentration was employed, which could accelerate the transformation process. It should also be noted that the coexistence of hydroxypyromorphite with chloropyromorphite could not be completely ruled out as the two minerals have very similar XRD patterns.…”

“…It should also be noted that the coexistence of hydroxypyromorphite with chloropyromorphite could not be completely ruled out as the two minerals have very similar XRD patterns. One difference in the XRD pattern between chloropyromorphite and hydroxypyromorphite is that the former has a double peak at 2θ = 30° (Figure a), while the latter only has one . The diffraction pattern of hydroxypyromorphite could be masked by that of chloropyromorphite if the latter is much more abundant.…”

A holistic approach to lead pipe scale analysis: Importance, methodology, and limitations

“…While X‐ray amorphous phases can be detected using PXRD, this technique cannot be used to identify a particular amorphous phase or phases. Other analytical techniques such as Fourier‐transform infrared spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV/Vis) (Guo & Herrera, 2021; Kim & Herrera, 2010) or Raman spectroscopy (Pasteris et al, 2021), coupled with elemental analysis can better constrain the characteristics of amorphous scale phases. Amorphous material composed of Al, Si, Ca, Mg, P, Fe, and/or Mn is frequently found in the outer scale layer(s).…”

“…Aside from AMSARC, other academic or consulting groups have undertaken their own lead pipe scale analysis efforts following different methodologies (Breach et al, 1991; Colling et al, 1987; Davidson et al, 2004; Elzenga & Graveland, 1980; Feller et al, 1984; Guo & Herrera, 2021; Hopwood et al, 2002; Hopwood et al, 2016; Kim & Herrera, 2010; Maynard & Wasserstrom, 2017; Pasteris et al, 2021; Peters et al, 1999; Sandvig et al, 2008). Appreciation of the benefits of LSL scale analysis grew further in the years following the Flint Water Crisis.…”