螺旋桨射流对底泥起悬及铅在底泥-水界面处迁移规律的研究

Research on sediment incipient motion and suspension caused by propeller jet and migration rules of Pb at sediment-water interface

河道中船舶螺旋桨射流会引起河道底泥悬浮并引发其中的重金属元素向水体释放。以物理模拟试验的方法,探讨了不同螺旋桨射流条件对底泥悬浮及底泥中重金属污染物——铅向水体释放的影响。试验设计了3个桨径和转速,在螺旋桨后2倍桨径处设置取样点,采集水体样品,并分析悬浮物的浓度。在不同条件下,采用薄膜扩散梯度技术原位获取了上覆水和底泥中铅的垂向分布规律。试验结果表明:在静水条件下转动螺旋桨,螺旋桨桨径越大、转速越高、桨叶叶尖距离床面的高度越小,上覆水悬浮物浓度的峰值越大。同时,增大桨径和转速,表层底泥中铅(界面以下8 cm)的垂向浓度和释放量均有所增大。

Ship propeller jet in river may cause the suspension of sediment and lead to the release of heavy metal elements into water.The effects of different propeller jet conditions on sediment suspension and release of heavy metal pollutant-Pb into water were discussed through physical simulation test.Three diameters and rotating speeds of propeller were setup in the test.Water samples were collected at a place of 2 times of the propeller diameter behind the propeller to analyze the concentration of suspended solid.Also,the vertical distribution of Pb in overlying water and sediment was obtained in situ by using the technique of diffusive gradients in thin films.The test results show that the larger the propeller diameter,the higher the rotor speed,and the smaller the distance between the blade tip and the riverbed surface,the bigger the peak value of the suspended matter concentration in the o verlying water when turning the propeller in still water.Meanwhile,the vertical concentration and release amount of Pb in and from the surface sediment(8 cm below the interface)increase with the propeller diameter and rotating speed increasing.