Biochar Application Effects on Soil Phosphorus Sorption and Release

We investigated the effects of chromate (CrVI) and phosphate (P) on their uptake and translocation in As-hyperaccumulator Pteris vittata (PV). Plants were exposed to 1) 0.05 mM CrVI and 0, 0.05, 0.25 or 1.25 mM P or 2) 0.25 mM P and 0, 0.05, 0.25 or 1.25 mM CrVI for 24 h in hydroponics. PV accumulated 2,919 mg/kg Cr in the roots at CrVI0.05, and 5,100 and 3,500 mg/kg P in the fronds and roots at P0.25. When co-present, CrVI and P inhibited each other’s uptake in PV. Increasing P concentrations reduced Cr root concentrations by 6282% whereas increasing CrVI concentrations reduced frond P concentrations by 5259% but increased root P concentrations by 1115%. Chromate reduced P transport, with more P being accumulated in PV roots. Though CrVI was supplied, 6478% and 92% CrIII were in PV fronds and roots. Based on X-ray diffraction, Cr2O3 was detected in roots confirming CrVI reduction to CrIII by PV. In short, CrVI and P inhibited each other in uptake and translocation by PV and CrVI reduction to CrIII in PV roots served as its detoxification mechanism. The finding helps to understand the interactions of P and Cr during their uptake in PV.