Finally, X-ray diffractometry was used to determine mineralogical changes that occurred in the slag during the course of the incubation. For apatite-amended slag, there generally were no significant differences in lead concentration for any fraction when compared to the control. There was also a slight but insignificant increase in cadmium concentration for the apatite-amended carbonate and residual fractions. Three and twelve weeks are the time increments shown. No cadmium was in the organic fraction.
Incubation time is again three weeks.
Quartz peaks are labelled A, and lead pyromorphite peaks are labelled B. Peak height is proportional to abundance. Some of the decrease in the quartz peak height may be due to silica dissolution. Pyromorphite increases in abundance as treatment progresses, indicating that this is the mineral phase in which the lead is being sequestered. This form of remediation has the advantage of being performed in situ , without the need for expensive excavation and waste removal. The addition of phosphate is more efficient at redistributing lead than cadmium, as the insoluble phosphate mineral pyromorphite is available to sequester this metal in a non-bioavailable form.