Background Nitrogen (N) and phosphorus (P) control in sediment remediation through adding natural material has been paid more and more attention. In this study, different natural material including iron-rich clay mineral, calcite, kaoline, sugarcane bagasse and Phragmites detritus was applied to test the effect on N and P control in a mesocosm experiment.
Results Iron-rich clay mineral and Phragmites detritus had an obvious advantage on P control in terms of almost undetectable soluble reactive phosphorus (SRP) in water column throughout the experiment, which could be explained by strong P adsorption ability. The high available organic carbon in sediment and water column after sugarcane bagasse addition provided enough electron donors for denitrification and dissimilatory nitrate reduction to ammonium (DNRA), which was responsible for nitrate (NO 3 - -N) deficiency and ammonium (NH 4 + -N) accumulation in water column. Also this resulted in anaerobic status, further fuelling P release from iron-bound P induced by anoxia. Thus, sugarcane bagasse application should be considered its dosage in order to balance the denitrification and DNRA as well as P release. Calcite and Phragmites detritus should be recommended as remediation material for N removal according to the significant promotion of denitrification and limitation of DNRA, finally resulting in low NO 3 - -N and NH 4 + -N. These results could be explained by the shift of functional microbial community composition and abundance after natural material addition.
Conclusions Iron-rich clay mineral and Phragmites detritus should be regarded as the promising sediment remediation material for P immobilization due to the increase of P adsorption ability. Taken together, the selection of sediment remediation material should combine the N and P coupling relationship, avoiding that NO 3 - -N removal caused the P leaching or NH 4 + -N accumulation.