Using phosphate rock to immobilize metals in soil and increase arsenic uptake by hyperaccumulator Pteris vittata

Abstract

This greenhouse experiment evaluated the effects of phosphate rock (PR) on arsenic and metal uptake by the arsenic hyperaccumulator Pteris vittata in a soil spiked with arsenic and heavy metals Cd, Pb and Zn. Five soil treatments were used, 1) control with no arsenic, 2) spiked with 50 mg kg − 1 As (As) as Na 2H AsO 4, 3) spiked with 50 mg kg − 1 As and P as PR (AsP), 4) spiked with 50 mg kg − 1 As, Pb, Cd, and Zn (AsM), and 5) spiked with 50 mg kg − 1 As, Pb, Cd, Zn and P (AsMP). The plants were harvested after growing in the soil for five weeks. Compared to the As treatment, the presence of heavy metals (AsM) reduced arsenic concentrations in the fronds from 1631 to 608 mg kg − 1 . However, this effect was mitigated by PR (AsMP), with arsenic concentrations in the fronds increased from 608 to 1046 mg kg − 1 . Phosphate rock also significantly reduced Pb (13.5 to 4.10 mg kg − 1 ) and Cd (13.0 to 3.45 mg kg − 1 ) concentrations in the fronds. Most of the arsenic in P. vittata was accumulated in the fronds (89–93%). Compared to the control, P was more concentrated in the roots along with less P being translocated to the fronds in the treatments with arsenic. While in those same treatments higher Ca concentrations in both the fronds and roots were observed. This research shows that PR was effective in increasing arsenic uptake and decreasing metal uptake by P. vittata and thus can be used as a cost-effective amendment for phytoremediation of arsenic and metal polluted soils.