Uptake of phosphorus and lead by Brassica juncea and Medicago sativa from chloropyromorphite

In situ remediation of lead (Pb)-contaminated soils via phosphate amendments has been extensively used to immobilize Pb as pyromorphite. However, in phosphorus (P) deficient soils, plants may develop extensive root systems to access P in any P-containing minerals, thereby affecting the stability of Pb5 (PO4)3Cl (Chloropyromorphite; CP). We grew Brassica juncea and Medicago sativa in sand culture to evaluate the stability of CP in the presence or absence of hydroxyapatite (HA) as P source. Treatments (per kilogram of sand) watered with P-nutrient solution were control [PC0, (without CP)], 1, and 5 g Pb as CP [PC1, and PC5] and 0.45 g P as HA (PA), and those of watered with P-free nutrient solution were 1 and 5 g Pb as CP [NC1 and NC5], 5 g Pb as CP plus 0.45 g P as HA [NAC5], and 0.45 g P as HA [NA]. Plants in NC1 and NC5 treatments showed stunted growth and reductions in shoot elongation and leaf size. Among CP treated pots, the highest shoot Pb uptake was observed in NAC5 treatment. The results suggested that Pb accumulation and translocation in the plants was markedly higher in P-sufficient conditions than in P-deficient conditions.