The apatite mineral family is the most abundant source of inorganic phosphate on earth, and especially common is hydroxyapatite [Hap; Ca₁₀(PO₄)₆(OH)₂], the primary component of bone matter. HAp has successfully been used in permeable reactive barriers (PRBs) for the remediation of groundwater heavy metals. As a neurotoxin widely present in soils, Pb remediation is of particular interest. It is suspected that the mechanism of Pb immobilization in HAp PRBs is through the formation of the Pb analogue, hydroxypyromorphite [HPm; Pb₁₀(PO₄)₆(OH)₂]. The solubility of HPm is extremely low in natural environments, making it an effective sink for Pb and limiting Pb bioavailability.

A solid solution series of HAp and HPm will be prepared by varying the Pb:Ca ratio in the growth solutions. Characterization of the products of these experiments will use a variety of analytical techniques; x-ray powder diffraction (XRD) will be used to verify the phases present, while the final Pb:Ca ratio will be determined using x-ray fluorescence spectroscopy (XRF). Additional spectroscopic techniques such as FT-IR and solid-state nuclear magnetic resonance (NMR) will also be utilized. These results will then be compared to those obtained from a novel synthesis mimicking the function of a HAp PRB in Pb-contaminated groundwater in order to determine the structural incorporation of Pb into the substrate.