Nitrogen species coupled with transpiration enhance Fe plaque assisted aquatic uranium removal via rhizofiltration of Phragmites australis Trin ex Steud

Abstract

The influences of N species and transpiration on the Fe plaque (IP) formation and related aquatic U rhizofiltration had not revealed yet, especially when these factors were co-existed. It was evaluated in a mesocosm experiment in the condition of respective ammonium (NH4+)/nitrate (NO3−) cultivation of Phragmites australis Trin ex Steud. coupled with different transpiration rates (TRs). The results suggested that the enhanced transpiration of P. australis improved the aquatic U rhizofiltration in both NO3− and NH4+ rich milieus. However, the NO3− dependent oxidizing milieu restricted aquatic U uptake by the root of P. australis (up to 47.6 ± 1.8 mg kg−1 under high TR) via IP assisted rhizofiltration. The high aquatic U availability and limited IP formation in NO3− rich milieu benefited the U retention within root tissue. On the contrary, the aquatic U rhizofiltration (up to 62.1 ± 1.0 mg kg−1 under high TR) was enhanced under NH4+ dependent reductive milieu. It was mainly contributed by U retention within IP. The area related U accumulation in different N species cultured roots was enhanced but did not significantly different under higher TR condition. The result suggested that the supplied NH4+ coupled with enhanced transpiration was supposed to be more optimized option for IP assisted aquatic U rhizofiltration via P. australis.