Immobilization
of Pb by phosphate-containing compounds involves
the formation of Pb phosphate (pyromorphite), which is
highly stable even in low pH. The formation of pyromorphite
will not only reduce the mobility of Pb in soil
(McGowen et al., 2001), but also the bioavailability of Pb
to plants and human digestion systems (Cheng and Hseu,
2002). Chemical immobilization is preferred for its relatively
low cost, and also the addition of phosphate is a normal
agricultural practice anyway.