Effects of in situ physical elution treatments of sediment on the germination and growth of Vallisneria natans (Lour.) Hara

In situ physical elution treatments are emerging techniques applied to remediate contaminated sediments, while the effect of sediments elution on the germination and growth of submerged macrophyte remains unclear. Two typical in situ physical elution treatments, including in situ air elution and in situ hydraulic elution, were simulated to treat the sediments enriched with organic matter to investigate the effects of physical elution on the germination and growth of Vallisneria natans (Lour.) Hara and the physiochemical properties of the sediments. The results indicated that the typical germination and growth index of Vallisneria natans (Lour.) Hara, such as the germination rate and speed of seeds, the fresh weight and the height, the leaf number and the root number all increased in post-eluted sediments. Compared to the control group, the indexes of the hydraulic elution group showed better, as the germination rate increased to 2.9 times, the plant height and the root number increased to 2.29 and 4.76 times. After the physical elution treatments on sediment, the ammonia (NH_4^--N) and acid volatile sulfide (AVS) contents decreased by 34.15%-35.19% and 7.67%-44.89%, respectively, and the concentrations of organic matter was lowered by 70.04%-77.90%. The oxidation-reduction potential of surface sediments (0-5 cm) was alleviated, from strong reduction state (ORP<-350 mV) to weak reduction state (ORP:-200--100 mV). In addition, the proportion of large sediment particles (50-2 000 μm) in the sedment increased to 89.02%-92.84%, promoting the diffusion of dissolved oxygen in the overlying water into the sediments, hence facilitating the germination and growth ofVallisneria natans (Lour.) Hara. After in-situ physical elution, especially after hydraulic elution, the physical and chemical conditions of the sediments were more favorable to the germination and growth of Vallisneria natans (Lour.) Hara.