Summary• Pteris vittata is the first plant reported to be a hyperaccumulator of arsenic (As), and little is known about the mechanisms of As hyperaccumulation in this plant.• Arsenic distribution at the whole plant (fronds) and cellular level was investigated using chemical analyses and energy dispersive X-ray microanalyses (EDXA). Speciation of As in the fronds was determined using X-ray absorption near edge spectroscopy (XANES) analyses.• The majority of As was found in the pinnae (96% of total As). The concentration of As in pinnae decreased from the base to the apex of the fronds. Arsenic concentrations in spores and midribs were much lower than in the pinnae. EDXA analyses revealed that As was compartmentalized mainly in the upper and lower epidermal cells, probably in the vacuoles. The distribution pattern of potassium was similar to As, whereas other elements (Ca, Cl, K, Mg, P and S) were distributed differently.• XANES analyses showed that approximately 75% of the As in fronds was present in the As(III) oxidation state and the remaining as As(V).

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A field study was conducted to investigate the potential of three plant species for phytoremediation of a 137Cs‐contaminated site. Approximately 40‐fold more 137Cs was removed from the contaminated soil in shoots of red root pigweed (Amaranthus retroflexus L.) than in those of Indian mustard [Brassica juncea (L.) Czern] and tepary bean (Phaseolus acutifolius A. Gray). The greater potential for 137Cs removal from the soil by A. retroflexus was associated with both high concentration of 137Cs in shoots and high shoot biomass production. Approximately 3% of the total 137Cs was removed from the top 15 cm of the soil (which contained most of the soil radiocesium) in shoots of 3‐too‐old A. retroflexus plants. Soil leaching tests conducted with 0.1 and 0.5 M NH4NO3 solutions eluted as much as 15 and 19%, respectively, of the soil 137Cs. Addition of NH4NO3 to the soil, however, had no positive effect on 137Cs accumulation in shoots in any of the species investigated. It is proposed that either NH4NO3 solution quickly percolated through the soil before interacting at specific 137Cs binding sites or radiocesium mobilized by NH4NO3 application moved below the rhizosphere, becoming unavailable for root uptake. Further research is required to optimize the phytotransfer of the NH4NO3‐mobilized 137Cs. With two croppings of A. retroflexus per year and a sustained rate of extraction, phytoremediation of this 137Cs‐contaminated soil appears feasible in <15 yr.

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