The biosorption of arsenic species by dried lettuce leaves (L.sativa) was investigated. Arsenic sorption, that is not effective on in natura biomass, was enhanced when the biomass was previously loaded with Fe(III). Analysis of X-ray Absorption Near-Edge Spectroscopy (XANES) spectra showed that iron was incorporated as Fe(III) and arsenic as As(V), regardless the contact with the lowest or highest valence species of these elements. The features of Extended X-ray Absorption Fine-Structure Spectroscopy (EXAFS) spectra suggest that the nearest neighboring atoms of iron ions are the same in all the samples, even in the As-Fe loaded ones. These results indicate the arsenic oxyanions as the sorbed species on the iron-loaded biomass.