Arsenic and Chromium Uptake By Pteris Vittata from Contaminated Soils: A Long Term Study.

Arsenic (As) and chromium (Cr) are toxic to plants, animals and humans, thus it is important to reduce their exposure to humans. Phytoextraction is a low-cost technology that utilizes hyperaccumulator plants to extract metals from soil. As-hyperaccumulator Pteris vittata (Chinese brake fern) can accumulate up to 23,000 mg kg^-1 As in the fronds. It can also accumulate large amounts of Cr in the roots in hydroponic experiments, with little Cr being translocated to the fronds. The ability of P. vittata in taking up As and Cr from contaminated soils was assessed over 6 years using plots containing 162 kg soil each supporting 9 plants. Initial soil As and Cr concentrations were 129 and 83 mg kg^-1. P. vittata removed 47% of soil As, reducing soil concentration to 69 mg kg^-1. After 3 years, As accumulation in P. vittata fronds decreased probably due to labile As being depleted. Over time, the As from the amorphous fraction exhibited the highest decrease, showing the unique ability of P. vittata to solubilize non-labile As in soil. However, Cr concentration did not change much over the 6 years, indicating that PV was ineffective in taking up Cr from contaminated soil. Cr concentrations in PV fronds were <2 mg kg^-1, consistent with little translocation. PV was effective in remediating As-contaminated soils but not Cr-contaminated soil.