Simulation of influence of dredging on sediment resuspension and nutrient loading in lake

Abstract

选取太湖梅梁湾污染底泥为研究对象,利用沉积物再悬浮发生装置,通过室内模拟实验研究太湖夏季常规风情下底泥疏浚对沉积物再悬浮及上覆水营养盐动态变化的影响.结果表明,在模拟的风情扰动过程结束时(5 h),扰动过程未疏浚与疏浚处理水柱总悬浮颗粒物(TSS)含量变化差异显著,未疏浚对照水柱TSS含量是初始值的7.7倍,而疏浚水柱TSS在第2 h达到峰值,为初始值的3.8倍;未疏浚水柱TSS含量沉降过程最初1 h迅速降低了84.0%,而疏浚水柱TSS含量在沉降3 h后趋于平衡.伴随着沉积物的再悬浮过程,疏浚与未疏浚对照水柱中TP含量均在第5 h达到最大,分别增加负荷78.6和92.2 mg/m².就短时效而言,底泥疏浚后沉积物的再悬浮过程显著受到抑制,并能够显著地减小沉积物再悬浮过程中溶解性磷酸盐的释放;但对水柱中总磷、总氮、铵氮、硝酸盐和亚硝酸盐含量变化影响较小.;A simulated experiment using a new Y-shape sediment resuspension apparatus has been conducted to investigate the influence of dredging on sediment resuspension and the dynamics of nutrient loading in water column under the common wind-wave disturbance, and the contaminated sediment from Meiliang Bay, Lake Taihu, has been selected in this study. The results show that the loading of total suspended solid (TSS) in undredged and dredged water column were 7.7 and 3.8 times of that of the initial value, respectively, at the end of the wind-wave disturbance (5 h). TSS decreased to 16% of initial content in the undredged water column after initial 1 h of settling process; while TSS in the dredged water column had no significant decrease during the entire settling process, and reached its equilibrium after 3 h of settling process. TP in the dredged and undredged water column reached its maximum value after 5 h of disturbance, with the maximal increment of 78.6 and 92.2 mg/m², respectively. The results indicated that fulminant release of internal nitrogen and phosphor was caused by the wind-wave disturbance. In terms of the short-term effects of sediment dredging, sediment resuspension and PO₄^3--P release during resuspension were remarkably inhibited to a certain degree, but not for TP, TN, NO₃^--N and NO₂^--N content.