398-8 Microscale Reactivity of Arsenic On a Soil Sand Grain.

See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Arsenic Dynamics In Near-Surface Systems: I

Wednesday, November 6, 2013: 10:40 AM
Tampa Convention Center, Room 25

Dean L. Hesterberg1, Montserrat Fuentes2, Matthew Polizzotto3, Joseph S. Guinness2, Ryan Tappero4, Keith Jones5, Chuanzhen Zhou6 and Eva M. Johannes7, (1)Soil Science, North Carolina State University, Raleigh, NC
(2)Statistics, NC State University, Raleigh, NC
(3)1272 University of Oregon, University of Oregon-Eugene, Eugene, OR
(4)Photon Sciences, National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY
(5)Environmental Sciences, US-DOE Brookhaven National Laboratory, Upton, NY
(6)Engineering Research, NC State University, Raleigh, NC
(7)Cellular & Molecular Imaging Facility, NC State University, Raleigh, NC
Abstract:
Soils regulate the movement of potentially toxic trace elements from natural or anthropogenic sources into food and water supplies. Because soil matrices are complex assemblages of minerals and organic matter, our most advanced analytical techniques are limited in their ability to elucidate specific geochemical reaction mechanisms that control trace-element mobility. This research aims to determine how the natural complexity of soil matrices affects arsenic reactivity. We characterized mineral-organic coatings on a quartz soil sand grain, and we measured progressive oxidation and accumulation of As following treatments with As(III). Synchrotron x-ray computed microtomography (CMT) indicated grain-coating thicknesses of tens of microns, micro x-ray fluorescence microprobe (μ-XRF) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) showed heterogeneous element distributions across the region mapped, and micro X-ray absorption near edge structure (μ-XANES) analysis revealed that a significant proportion of reacted As(III) was oxidized to As(V). Spatial statistical analyses showed a strong correlation between accumulated As and Fe except at high relative concentrations of Cr, suggesting an influence of Fe mineralogical differences. Direct analyses of chemical reactivity at a microscale in soil materials can potentially infer reaction mechanisms that control As mobility in the environment.

See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Arsenic Dynamics In Near-Surface Systems: I