es500994u_si_001.pdf (578.73 kB)
In Situ Formation of Pyromorphite Is Not Required for the Reduction of in Vivo Pb Relative Bioavailability in Contaminated Soils
journal contribution
posted on 2014-06-17, 00:00 authored by Albert L. Juhasz, Dorota Gancarz, Carina Herde, Stuart McClure, Kirk G. Scheckel, Euan SmithThe
effect of phosphate treatment on lead relative bioavailability
(Pb RBA) was assessed in three distinct Pb-contaminated soils. Phosphoric
acid (PA) or rock phosphate were added to smelter (PP2), nonferrous
slag (SH15), and shooting range (SR01) impacted soils at a P:Pb molar
ratio of 5:1. In all of the phosphate amended soils, Pb RBA decreased
compared to that in untreated soils when assessed using an in vivo
mouse model. Treatment effect ratios (i.e., the ratio of Pb RBA in
treated soil divided by Pb RBA in untreated soil) ranged from 0.39
to 0.67, 0.48 to 0.90, and 0.03 to 0.19 for PP2, SH15, and SR01, respectively.
The decrease in Pb RBA following phosphate amendment was attributed
to the formation of poorly soluble Pb phosphates (i.e., chloropyromorphite,
hydroxypyromorphite, and Pb phosphate) that were identified by X-ray
absorption spectroscopy (XAS). However, a similar decrease in Pb RBA
was also observed in untreated soils following the sequential gavage
of phosphate amendments. This suggests that in vivo processes may
also facilitate the formation of poorly soluble Pb phosphates, which
decreases Pb absorption. Furthermore, XAS analysis of PA-treated PP2
indicated further in vivo changes in Pb speciation as it moved through
the gastrointestinal tract, which resulted in the transformation of
hydroxypyromorphite to chloropyromorphite.