Effects of Sediment Microenvironment on Sedimentary Phosphorus Release Under Capping

Abstract

The sediment microenvironment has an important effect on the release of endogenous phosphorus. In this study, the influence of two different in-situ covering materials on the sediment microenvironment were compared, and the controlling effect of endogenous phosphorus release were studied. The sediment microenvironment was represented by the concentration of NH4+-N, Fe2+ in interstitial water, and microbial activity. The results showed that the concentrations of NH4+-N and Fe2+ were lower under ACPM coverage than those of the Phoslock® group, and the microbial activity was higher, indicating that the redox potential of ACPM coverage was higher than that of Phoslock®. Furthermore, the bottom sediment microenvironment was in an aerobic state. Compared with the Phoslock® group, the DIP concentrations in both the overcover water and porewater in the ACPM group were higher, indicating that Phoslock® was superior to ACPM with respect to the phosphate adsorption capacity, suggesting that the sediment microenvironment was not the only criterion for phosphorus adsorption. In the fixation process of endogenous phosphorus, both of the covering materials were conducive to the fixation of inter phosphorus, and Ca-P increased significantly. On the other hand, oxidizing ACPM led to an increase in NH4Cl-P and a significant decrease in Fe/Al-P. This promotes the release of active phosphorus, which is conducive to the cleaning of the sediment and phosphorus release.