沉积物原位物理洗脱技术对苦草萌发生长的影响

原位物理洗脱技术是一种应用于修复受污染的沉积物的新兴技术,但沉积物洗脱处理后对沉水植物萌发生长的影响尚不明确。通过模拟原位空气洗脱与原位水力洗脱2种典型原位物理洗脱技术,处理富含有机质的沉积物,研究洗脱对苦草萌发和生长指标的影响,以及洗脱后沉积物的理化性质的变化。结果表明:2种方式洗脱后沉积物中苦草种子的萌发率、萌发速度以及幼苗的株高、鲜质量、根数、叶数等指标均优于未洗组,其中水力洗脱后沉积物中苦草的萌发生长状况最好,萌发率是未洗组的2.9倍,株高和根数分别是未洗组的2.29和4.76倍;物理洗脱后,沉积物中氨氮($NH_{4}^{-}$-N)与酸可挥发性硫化物(AVS)等还原性物质浓度分别下降34.15%~35.19%和7.67%~44.89%,有机质浓度下降70.04%~77.90%,表层(0~5 cm)沉积物由强还原状态(ORP<-350 mV)改善至弱还原状态(ORP为-200~-100 mV);此外,沉积物中大粒径(50~2 000 μm)颗粒占比增至89.02%~92.84%,有利于上覆水中的O₂向沉积物中扩散,促进苦草的萌发生长。原位物理洗脱尤其是水力洗脱后,沉积物的理化条件更有利于苦草的萌发生长。

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.