Effects of Fertilizer on Arsenic Accumulation in a Hyperaccumulating Fern: A Two Year Phytoremediation Field Study.

Arsenic contamination is widespread in soils globally, due to use of arsenical pesticides and treated wood, mining activities, and arsenic-contaminated irrigation water. Sustainable remediation methods are needed to reduce human exposure to this carcinogen. Among in situ methods, phytoextraction is a promising new technology to remediate soils with shallow arsenic contamination; the hyperaccumulating fern Pteris vittata removes arsenic from soil with minimal site disturbance. However, estimates of remediation times using P. vittata are on the order of decades; rates are based mainly on greenhouse experiments, which likely over-predict field performance. More research is needed to increase remediation rates and optimize arsenic phytoextraction in field conditions.

The objective of this study is to quantify impacts of organic and inorganic fertilizers on P. vittata biomass production and arsenic uptake, in order to develop more efficient methods for in situ arsenic phytoremediation. A two year, large-scale (1600 fern) field study was established in an abandoned railroad right-of-way contaminated with arsenic (85.5±8.8 ppm). Organic N and inorganic N (50 kg N ha^-1), organic P and inorganic P (85 kg P ha^-1), and compost (151 kg N ha^-1, 34 kg P ha^-1), were applied to separate sub-plots; control ferns were grown in un-amended soil. Results 9 months post-planting suggest control ferns removed the most arsenic (7.8 kg As ha^-1 yr^-1), followed by compost-amended ferns (6.9 kg As ha^-1 yr^-1). All other treatments decreased arsenic removal by a factor of 2 to 3 compared to the control, contrary to what was observed under greenhouse conditions. Fertilizers had no effect on biomass, but inhibited arsenic uptake in the fern. New biomass and arsenic accumulation results from fronds harvested 21 months post-planting will be presented; preliminary data suggest that arsenic uptake in N-amended ferns increased by 2:1 compared to the first harvest, to half that of control ferns.