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

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.