波浪对太湖梅梁湾底泥氧气侵蚀深度的影响

Effects of waves on oxygen penetration depth of sediment from Meiliang Bay of Taihu Lake

通过室内波浪水槽试验,利用溶解氧微电极研究了波浪对太湖梅梁湾底泥中氧气侵蚀深度的影响.结果显示:太湖梅梁湾底泥在水槽中一夜平衡后,氧气侵蚀深度约为5 mm.经4 cm波高的波影响2 h后,表层底泥基本没有被侵蚀,而表层溶解氧质量浓度从原来的6.29 mg/L上升至6.90 mg/L,氧气侵蚀深度约达6 mm.初始值和4 cm小波后两者拟合方程具有相近的斜率(-0.077 7与-0.072 8).经10 cm波高的波影响2 h后,可能受采泥管管壁形成的回旋涡流影响,底泥表层的物理侵蚀达到(1.33±0.15)cm.同时,氧气侵蚀深度降至3.2mm左右,其拟合方程的斜率减小为0.012 3.由此可以表明:小波可以增加底泥表层溶解氧和氧气侵蚀深度;而大波能造成表层底泥受到严重的物理侵蚀并破坏原溶氧层而形成新的较浅的溶氧层,最终将可能影响微生物活动和营养盐释放.

Through laboratory wave flume experiments,the effects of waves on oxygen penetration depth（OPD） of lake sediment from Meiliang Bay of Taihu Lake were studied by using oxygen microsensor.It was found that the OPD of sediment from Meiliang Bay was about 5 mm after being balanced in the flume for one night.After effects of little waves 4 cm in height for 2 hours,the surface of the sediment was not eroded by and large.While the oxygen concentration of sediment surface was raised from 6.29 mg/L to 6.90 mg/L,and the OPD was about 6 mm.The fitting equations for the initial values and the little waves had similar slopes（-0.077 7 and-0.072 8）.After effects of strong waves 10 cm in height for 2 hours,the surface of sediment was eroded about（1.33±0.15） cm,which might be influenced by the eddy waves produced by tube wall.Meanwhile,the OPD was reduced to about 3.2 mm,and the slope of the fitting equation became 0.012 3.A conclusion is drawn that the little waves can raise the surface oxygen concentration and the OPD,while the strong waves cause physical erosion of surface sediment and destroy the original oxygen layer so as to induce new and shallow OPD.It will further have impact on the activities of microbes and the release of nutrients in the sediment.