Iron oxidation states on root surfaces of a wetland plant (Phragmites australis)

Iron in root plaque is usually thought to be Fe(III) because of rhizosphere oxidation. This study was conducted to examine Fe oxidation states on root surfaces of the common reed [Phragmites australis (Cav,) Trin, ex Steudel], Using an EDTA-BPDS method, Fe(II) and Pe(III) on the surfaces of roots sampled from various environments were stabilized, extracted and determined simultaneously. The proportion of extracted Fe(II) to total Fe ranged from 0.17 to 0.65 for the roots grown in constructed wetlands, fields, and hydroponic culture; and from 0.34 to 0.70 for different sections of wetland plant roots. The observed results suggested that Fe plaque is caused not only by rhizosphere oxidation, but also by Fe(ll) compound formation on the root surfaces.