XAS speciation of arsenic in a hyper-accumulating fern

Samuel M. Webb, Jean-Francois Gaillard*, Lena Q. Ma, Cong Tu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

148 Scopus citations


The coordination environment and the redox speciation of arsenic in a newly discovered arsenic hyper-accumulating fern (Pteris vittata L.) were investigated by X-ray absorption spectroscopy. This method allowed us to probe arsenic directly, i.e., with minimal sample preparation. The results indicate that arsenic is predominantly accumulated as As(III) in the leaves. XANES and EXAFS results show that As(III) in the leaves is primarily present as aqueous arsenite species. The plant actively maintains arsenic in this reduced oxidation state, because after sample collection and subsequent aging and drying of the plant material, As(III) is gradually oxidized to As(V). We think that these arsenite species are sequestered in vacuoles. At extremely high As concentrations (ca. 1% As per dry weight) arsenic in the fern leaves is coordinated to a significant degree by sulfur in addition to oxygen. This spectral signature indicates that thiol-rich compounds are implicated in the biochemical transformations of arsenic within the plant.

Original languageEnglish (US)
Pages (from-to)754-760
Number of pages7
JournalEnvironmental Science and Technology
Issue number4
StatePublished - Feb 15 2003

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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