Poster: Heavy Metals

Abs # 679: Spatial Distribution of Arsenic Species in Brake Fern (Pteris vittata L.) Using X-ray Absorption Spectroscopy

Presenter:	Bondada, Bhaskar R, bbondada@hotmail.com
Additional Authors	Ma, Lena Q (A)   Underhill, Royale S (B)   Duran, Randolph  (B)   Davidson, Mark  (C)
Affiliations:	(A): University of Florida, Soil and Water Sciences Department, 2169 McCarty Hall, P.O. Box 110290, Gainesville, FL 32611. (B): University of Florida, Butler Polymer Laboratories, Department of Chemistry, 318 Leigh Hall, P.O. Box 117200, Gainesville, FL32611. (C): University of Florida, Microfabritech, P.O. Box 116500, Gainesville, FL 32611

The levels of arsenic (As), a naturally occurring metalloid in earth's crust, have increased substantially in the environment due to anthropogenic activities. The recent discovery of an As-hyperaccumulating fern (Pteris vittata L.; Nature, 409:579, 2001), commonly known as brake fern, seems promising in phytoremediating As-contaminated sites. The central emphasis of this study was to determine the spatial distribution of As and its speciation in tissues of various organs of brake fern using Extended X-ray Absorption Fine Structure (EXAFS) at the Argonne National Laboratory, Argonne, IL. Cross-sections from fresh lamina of frond, stipe, and root were taken from fern plants treated with 100 ppm soil As and examined with a standard X-ray microprobe. The xylem cells of root and stipe displayed the lowest As levels. The greatest As concentration occurred in the xylem and mesophyll cells of the lamina, especially in those cells that existed in close proximity with the blade margins. Such distribution pattern of As by fern plant was reflective of its hyperaccumulating property. For EXAFS study, cryosections of fronds from fern plants treated with 100 ppm As were used to determine speciation of As in the epidermal cells, mesophyll tissues, and xylem strands. Most of the As occurred as arsenite in all tissues and the epidermal and mesophyll cells accommodated the largest concentration of As. The basic knowledge obtained from this study will be utilized to design phytoremediation strategies to cleanse As- contaminated sites.