Synchroton X-ray microprobe analysis was used to determine the source of arsenic in a Bangladesh rice soil sand fraction.  Most Fe oxide grains and micas contained arsenic but high arsenic concentrations were found associated with small rock fragments and Fe-oxide coatings on root surfaces.  It was hypothesized that the high arsenic contaminations are the result of arsenic adsorption at localized oxidized environments in the otherwise reduced soils during rice cultivation.  To test this hypothesis, thin sections were prepared using epoxy hardened by irradiation and the arsenic concentration mapped using scanning electron microscopy with energy dispersive X-ray analysis