Use of the DCB Technique for Extraction of Hydrous Iron Oxides from Roots of Wetland Plants

Replicate samples of Phragmites communis roots coated with hydrous iron oxide were analyzed for internal and external Fe using the dithionite-citrate-bicarbonate technique (hot DCB), a modified DCB technique (cold DCB), Ethylenediamine tetraacetic acid (EDTA), Diethylenetriamine pentaacetic acid (DTPA), and a total Fe analysis. EDTA and DTPA were found to be inefficient in extracting FeOOH while both DCB techniques were efficient. Concentrations of Fe extracted (8.93% and 9.37% by weight) and percent of total Fe extracted (98.3% and 98.6%) by the hot and cold DCB techniques (respectively) were not significantly different. Results of the total Fe analysis (8.58% Fe by weight) were the same as extracted Fe and total Fe determined by the DCB techniques. This may reflect the large external Fe : internal Fe ratio of the sample roots. Despite equivalent results, the cold DCB technique is preferred over the hot DCB technique due to a reduced likelihood of structural damage to roots.