258 Use of Synchrotron Techniques to Determine Coordination and Speciation of Arsenic in the Desert Plant Parkinsonia Florida

Thursday, November 5, 2009: 3:20 PM
Kohlberg (Camino Real Hotel)
Hiram Castillo-Michel, M.S. , Chemistry, University of Texas at El Paso, El Paso, TX
Kenneth Dokken, Ph.D , Chemistry, University of Texas at El Paso, El Paso, TX
Jose Peralta-Videa, Ph.D. , Chemistry, University of Texas at El Paso, El Paso, TX
Jorge Gardea-Torresdey, Ph.D , Chemistry, University of Texas at El Paso, El Paso, TX
Parkinsonia florida is a plant species native to semi-desert regions of North America. Preliminary results suggest that this plant could be studied for phytoremediation purposes in the southwest USA. This work investigated the As uptake by P. florida plants from two soil types using synchrotron μXAS and ICP-OES techniques. Plants grown for 8 weeks in As(III) and (V) spiked soils (20 mg/L) from the area of El Paso, TX accumulated As only in root tissues. Plants grown in sandy type soil (SS) accumulated 164.39 ±5.38 mg As/kg dry tissue (DWT) for As(V) treatment and 102.18 ± 30.0 mg As/kg DWT for As(III) treatment. Arsenic accumulation decreased in plants grown in sandy clay loam (SCL) type soil (53.19 ± 4.78 mg As/kg DWT for As(V) treatment and 35.16 ± 2.59 for As(III) treatment). LC-XANES results show that a fraction of As higher than 86% was reduced to As(III) in plants grown in the As(V) treated SS soil. Also, a fraction of the reduced As, higher than 70%, was found coordinating to S in the form of As2S3 type compound. LC-XANES results from As(III) treated plants in the SS soil also show a high percentage of As(III) coordinated to sulfur (>63%). Additionally, a fraction higher than 20% of As was found as As(V). LC-XANES analyses of plants grown in the SCL soil showed similar results. However in SCL soil, for both As(V) and As(III), plants presented a smaller percentage of As coordinated to sulfur, when compared to the SS soil.