Arsenic speciation in tissues of the hyperaccumulator P. calomelanos var. austroamericana using X-ray absorption spectroscopy.

The fate and chemical speciation of arsenic (As) during uptake, translocation, and storage by the As hyperaccumulating fern Pityrogramma calomelanos var. austroamericana (Pteridaceae) were examined using inductively coupled plasma−atomic emission spectrometry (ICP−AES) and synchrotron-based μ-X-ray absorption near edge structure (μ-XANES) and μ-X-ray fluorescence (μ-XRF) spectroscopies. Chemical analysis revealed total As concentration was ca. 6.5 times greater in young fronds (5845 mg kg−1 dry weight (DW)) than in old fronds (903 mg kg−1 DW). In pinnae, As concentration decreased from the base (6822 mg kg−1 DW) to the apex (4301 mg kg−1 DW) of the fronds. The results from μ-XANES and μ-XRF of living tissues suggested that more than 60% of arsenate (AsV) absorbed was reduced to arsenite (AsIII) in roots, prior to transport through vascular tissues as AsV and AsIII. In pinnules, AsIII was the predominant redox species (72−90%), presumably as solvated, oxygen coordinated compounds. The presence of putative ...