静水与流水条件下沉水植物生长对上覆水和沉积物磷迁移的影响

沉水植物生长可有效降低河湖内源磷污染. 为探究沉水植物在静水(v=0 m/s)和流水(v=0.10 m/s)条件下对上覆水和沉积物磷迁移影响，选取苦草(Vallisneria natans)和黑藻(Hydrilla verticillata)为研究对象，测定其生长期间上覆水、沉积物中各形态磷含量和沉水植物生物量，并监测环境因子变化. 结果表明:①苦草和黑藻生长期间上覆水和沉积物中各形态磷含量总体呈下降趋势，并在一定时期维持在较低水平. 相同流速下黑藻对上覆水磷的吸收效果优于苦草，苦草能抑制沉积物表面磷释放. ②试验20 d后，苦草和黑藻组上覆水各形态磷浓度显著低于对照组，试验结束时静水苦草组、静水黑藻组、流水苦草组和流水黑藻组上覆水TP(总磷)浓度相比对照组分别下降了0.13、0.15、0.19和0.25 mg/L. 静水条件下沉水植物以降低上覆水中DTP(溶解性总磷)为主，流水条件下以减少DTP和PP(颗粒磷)为主. ③试验结束时，苦草组和黑藻组沉积物TP含量在静水条件下分别下降了91.78、93.25 mg/kg，流水条件下分别下降了83.51、81.03 mg/kg；NaOH-P(NaOH提取磷)含量在静水条件下分别下降了57.76、55.86 mg/kg，流水条件下分别下降了24.52、19.24 mg/kg，沉积物从轻度污染逐步转为未受污染. ④试验50 d，苦草生物量在静水和流水条件下分别增加了353.08和402.03 g，黑藻生物量分别增加了415.00和477.08 g，沉水植物生物增长量在流水条件下显著高于静水组. 研究显示，苦草、黑藻生长均能有效吸收磷，在流水条件下可促进沉水植物生长和磷的吸收，同时改变了上覆水溶解氧(DO)浓度和pH等环境因子，从而影响磷在上覆水和沉积物的迁移及磷形态的转变. 

Effects of Submerged Macrophytes on Phosphorus Transport between Overlying Water and Sediment in the Growth Period under Static and Flowing Conditions

Submerged macrophytes can effectively reduce the internal loading of phosphorus (P) in lakes and rivers. To investigate the effects of submerged macrophytes on P migration and transformation in overlying water and sediment under static (v=0 m/s) and flowing (v=0.10 m/s) conditions, Vallisneria natans and Hydrilla verticillata were tested. The concentrations of different P forms in overlying water, sediment, and the biomass of submerged macrophytes during the growth period were measured. Changes in environmental factors were simultaneously monitored. The results showed that: (1) During the growth period of V. natans and H. verticillata, the concentrations of different P forms in the overlying water and sediment tended to decrease and maintain low over a period of a time. The absorption of P in overlying water by H. verticillata was better than that by V. natans, while V. natans inhibited the release of P from the sediment surface. (2) On the 20th day of the experiment, the concentrations of all P forms in the overlying water in the V. natans and H. verticillata groups were significantly lower than those in the control group. At the end of the experiment, the concentrations of total P (TP) in overlying water of the static V. natans, static H. verticillata, flowing V. natans, and flowing H. verticillata groups decreased by 0.13, 0.15, 0.19, and 0.25 mg/L, respectively, compared with that of the control group. In the static experimental group, the decrease of dissolved TP (DTP) was observed, while the decrease of both DTP and particulate P (PP) were seen in the flowing experimental group. (3) The TP concentrations in the V. natans and H. verticillata groups decreased by 91.78 and 93.25 mg/kg under static conditions and 83.51 and 81.03 mg/kg under flowing conditions, respectively. Meanwhile, the concentrations of NaOH extracted P (NaOH-P) in the V. natans and H. verticillata groups decreased by 57.76 and 55.86 mg/kg under static conditions and 24.52 and 19.24 mg/kg under flowing conditions, respectively. At the end of the experiment, the sediment had changed from slightly polluted to unpolluted in the experimental group in the experiment. (4) On the 50th day of the experiment, the biomass of V. natans increased by 353.08 and 402.03 g under static and flowing conditions, respectively, while the biomass of H. verticillata increased by 415.00 and 477.08 g, respectively. The growth of submerged macrophytes under flowing conditions was significantly better than that under static conditions. The results showed that V. natans and H. verticillate can absorb P during the growth period, and flowing conditions can promote the growth and P uptake of submerged macrophytes. The associated changes in the dissolved oxygen (DO), pH, and other environmental factors in the overlying water are attributable to P transport across the sediment-water interface and the P transformation.