Suppression of phosphorus release from sediment by Vallisneria natans combined with iron- and zirconium-modified bentonites: Effectiveness, mechanism and response of sedimentary microbial communities

Abstract

The efficiency and mechanism in the reduction of internal phosphorus loading from sediment by Vallisneria natans combined with iron- and zirconium-modified bentonites (abbreviated as FeBT and ZrBT, respectively) were studied, and the responses of the microbial communities in sediments to Vallisneria natans combined with FeBT and ZrBT were also explored. ZrBT had stronger phosphate adsorption ability than FeBT. The greatest phosphate adsorption capacities for FeBT and ZrBT in the simultaneous presence of common ions can attain 1.60 and 4.29mgP/g, respectively, and those for the loaded iron in FeBT and zirconium in ZrBT can attain 55.2mgP/g Fe2O3 and 164mgP/g ZrO2, respectively. The combined utilization of FeBT and Vallisneria natans and that of ZrBT and Vallisneria natans can effectively lower the releasing risk of phosphorus from sediment into the overlying water (OW), and the combined use of ZrBT and Vallisneria natans had a higher controlling efficiency than that of FeBT and Vallisneria natans. The passivation of diffusion gradient in thin film (DGT)-labile phosphorus in the sediment layer was vital to the control of phosphorus release from sediment by Vallisneria natans combined with FeBT and ZrBT. The bacterial communities in the sediments under the conditions of FeBT + Vallisneria natans and ZrBT + Vallisneria natans can exert well ecological functions. This work indicates that the combined utilization of ZrBT and Vallisneria natans is a better method to lower the releasing risk of phosphorus from sediment into OW than that of FeBT and Vallisneria natans.