Optimizing Arsenic Phytoremediation: Effects of Fertilizer on Brake Fern Arsenic Uptake and Biomass Production in Heterogeneous Field Conditions.

Arsenic contamination in urban soils is gaining recognition as a widespread problem, due to historical use of arsenical pesticides, coal combustion, mining activities, and use of arsenic-contaminated water in metropolitan areas.  The potential for human exposure to such contamination increases in industrial population centers, leading to a growing need for sustainable remediation techniques. Phytoextraction is an emerging technology to remediate soils with shallow arsenic contamination; the hyperaccumulating fern Pteris vittata removes arsenic from soil while leaving soil in place. Estimates of arsenic phytoremediation rates using P. vittata, based mainly on greenhouse experiments, are on the order of decades. More research is needed to optimize P. vittata performance in complex, heterogeneous field conditions and thus develop successful remediation methods.

The objective of this study is to determine fertilizer impact on P. vittata biomass production and arsenic uptake, in order to develop new methods for in situ arsenic phytoremediation that increase efficiency and decrease remediation time. Five slow-release agricultural amendments, including organic N, inorganic N, organic P, inorganic P, and compost, were applied to separate fern plots to see if healthier ferns accumulate more arsenic. The field study site is an abandoned railroad right-of-way (sandy loam to clay loam) moderately contaminated with arsenic (85.5±8.8 ppm) characterized by a Mediterranean climate. P. vittata ferns (200-400 per treatment) were planted 30 cm apart (11 ferns m^-2) in February 2013. Fern arsenic accumulation and biomass data 9 months post-planting suggest control ferns are most effective at removing 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 accumulation by a factor of 2 to 3, compared to control and compost-amended ferns. Increasing fern biomass did not increase phytoremediation efficiency; research should focus on increasing arsenic uptake in the fern.