Arsenic and heavy metal accumulation by Athyrium yokoscense from contaminated soils

Abstract

Athyrium yokoscense, a type of fern that grows vigorously in mining areas in Japan, is well known as a Cd hyperaccumulator as well as a Cu, Pb and Zn tolerant plant. However, no information is available on As accumulation of A. yokoscense, although it often grows on soils containing high levels of both heavy metals and As. In this study, young ferns collected from a mine area were grown in media containing As-spiked soils or mine soil in a greenhouse for 21 weeks. Athyrium yokosense was highly tolerant to arsenate and survived in soils containing up to 500 mg As (V) kg⁻¹. The addition of 100 mg As (V) kg⁻¹ resulted in the highest fern biomass (1.95 g plant⁻¹) among As-spiked soils. Although the As concentration of the fern was lower than other As hyperaccumulators, such as Pteris vittata, A. yokoscense could hyperaccumulate As in mature and old fronds. Arsenic was accumulated most efficiently in old fronds (922 mg kg⁻¹) in the media containing 5 mg As (III) kg⁻¹. Moreover, higher As accumulation was found in the roots of the ferns, with a range from 506 to 2,192 mg kg⁻¹. In addition, in the mine soil with elevated concentrations of As and heavy metals, A. yokoscense not only hyperaccumulated As (242 mg As kg⁻¹ in old fronds), but also accumulated Cd, Pb, Cu and Zn at concentrations much higher than those reported for other terrestrial plants. Athyrium yokoscense accumulated Cd mostly in fronds in high concentrations, up to 1095 mg kg⁻¹, while it accumulated Cu, Zn and Pb mainly in the roots and the concentrations were 375, 2040 and 1165 mg kg⁻¹, respectively.

Key words:

• accumulation
• arsenic
• Athyrium yokoscense
• heavy metal
• hyperaccumulator

ACKNOWLEDGMENTS

We thank Mitsubishi Material for providing soils and fern samples. This research was supported by a Sasakawa Scientific Research Grant (No. 16–317) from The Japan Science Society to T. K. Van and by the Grant-in-Aid for Scientific Research (B, No. 15380223) from Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan to K. Iwasaki.