Immobilization of phosphorus in sediment-water system by hydrous iron oxide and hydrous iron oxide/calcite mixture...

The efficiency and mechanism of hydrous iron oxide (HFO) and HFO/calcite mixture to inactivate the phosphorus in the overlying water (OW)/sediment system under the feed adding condition were explored, and the effect of HFO and HFO/calcite mixture addition on the diversity, composition and function of bacterial communities in the sediment was examined. HFO and HFO/calcite mixture direct addition can effectively lower the concentration of soluble reactive phosphorus (RSP) and diffusion gradient in thin film-unstable phosphorus (P_DGT) in OW and inactivate the P_DGT in the upper sediment. The elimination efficiencies of RSP by the direct HFO and HFO/calcite mixture addition were 48.9 %-97.0 % and 42.4 %-95.4 %, respectively. The alteration in the addition mode from the one-time to multiple direct addition was beneficial to the immobilization of RSP and P_DGT in OW and P_DGT in the upper sediment by HFO and HFO/calcite mixture under the feed input condition in the long run. Permeable fabric wrapping reduced the inactivation efficiency of RSP in OW by HFO and HFO/calcite mixture, but it made the recycling of these materials possible. Most of P immobilized by HFO and HFO/calcite mixture was relatively or very stable. After the HFO and HFO/calcite mixture addition, the composition of bacterial communities in the surface sediment changed. However, the bacterial communities in the amended sediments still can perform good ecological function. Our findings suggest that HFO and HFO/calcite mixture are promising phosphorus-immobilization materials for the inactivation of RSP and P_DGT in OW and P_DGT in the upper sediment under the feed inputting condition.