高等水生植物对太湖沉积物再悬浮特征的影响

目的]研究高等水生植物对太湖沉积物再悬浮的影响。方法]采用新型再悬浮模拟器,在底泥中种植沉水植物伊乐藻(Elodea nuttalli)和挺水植物芦苇(Phragmites australis),并设置不同的种植密度,在0.2～0.5 N/m2的切应力下和1～30 min的持续搅拌条件下,对太湖原状沉积物的再悬浮特征开展模拟实验研究。结果]种植水生植物可以有效减少水体中悬浮物浓度,各试验组及对照组最终上覆水悬浮物(Suspended Particulate Matter,SPM)浓度大小均为:无植物>覆盖度30%的伊乐藻>覆盖度60%的伊乐藻>密度50株/m2的芦苇>覆盖度90%的伊乐藻>密度80株/m2的芦苇>密度150株/m2的芦苇;各组的SPM浓度均随切应力的增大显著增大;在不同切应力下,各组内SPM浓度均随搅拌时间变化呈现先增加后逐渐趋于稳定的规律,无水生植物的桶内SPM浓度初期变化更为剧烈,而种植水生植物的桶内SPM浓度初期变化较为缓和,且种植密度越大该变化越小;种植挺水植物芦苇对SPM浓度的削减程度要明显大于沉水植物伊乐藻,在不同切应力下,增大芦苇种植密度使SPM浓度降低的幅度要比增大伊乐藻覆盖度更大。结论]通过全面地开展水体沉积物再悬浮特征研究,可以更好地为控制水体环境提供有力的科学依据。

Effects of Aquatic Plants on the Feature of Sediment Resuspension in Tai Lake

Objective] The aim was to study effects of aquatic plants on resuspension of sediment in Lake Taihu.Method] New resuspension simulator was used in the research.Elodea nuttalli,submerged plant,and Phragmites australis,emerging plant,were grown in substrate sludge with varied planting density set.Study of simulation experiment on the feature of sediment resuspension was carried on under shearing stress of 0.2-0.5 N/m2 and agitation of 1-30 min.Result] Aquatic plant growing would effectively reduce seston concentration in water.Concentrations of final Suspended Particulate Matter(SPM) in experimental groups and control groups were as follows: water without plant > coverage of 30% of Elodea nuttalli > coverage of 60% of Elodea nuttalli > Phragmites australis with concentration of 50 stock/m2>coverage of 90% of Elodea nuttalli > Phragmites australis with concentration of 80 stock/m2 > Phragmites australis with concentration of 150 stock/m2;SPM concentration showed a tendency from increasing to stable with change of stirring time under different shearing stresses: SPM concentration was of severe change at early stage in barrel without aquatic plant while change of SPM concentration in barrel with aquatic plant was quite mild and grew smaller with concentration increasing;SPM concentration was reduced much more if Phragmites australis planted compared with that of Elodea nuttalli;under different shearing stresses,reduction of SPM concentration by increase of Phragmites australis area was much more than by increase of Elodea nuttalli area.Conclusion] It would provide powerful scientific reference for control on aquatic environment through comprehensive research on the feature of sediment resuspension.