Quantitative simulative method of sediment resuspension in Lake Taihu

Abstract

由于风浪对浅水湖泊底泥的强烈扰动作用, 底泥再悬浮的生态效应研究成为目前国际研究热点之一。但方法的缺乏极大地限制了有关底泥再悬浮环境效应的深入研究。本研究应用一种新的沉积物再悬浮装置, 模拟了太湖南部长兜港水域不同风浪影响下悬浮物的垂向分布, 获得水柱总悬浮物量(T)与扰动频率(n)的定量关系:T=19.77×exp(n/2.61)-71.7。结合现场实测风情下的水柱总悬浮物量, 建立了室内水动力条件、水柱总悬浮物量和现场风情的定量关系。研究2004年10月至2005年10月太湖全年代表性小风、中风及大风与再悬浮装置的扰动频率对应关系, 估算了小风、中风和大风常规风情引起的总悬浮物量分别为159、230、425g/m²。结果表明, 模拟获得的太湖悬浮物垂向分布规律与现场状况较为接近, 是目前较为适用的浅水水体沉积物再悬浮模拟方法。;Concerns on ecological effects of sediment resuspension are on the rise because the sediments in shallow lakes are frequently disturbed by winds. However, few methods could be suitable for supporting its related study. In this paper, Y-shape apparatus for simulating sediment resuspension was used to study vertical distribution of suspended sediments in water column and their total suspended amounts driving by different wind speed in Chang-dougang Harbor, southern Lake Taihu. The results showed that the relationship between the total suspended amount of sediments in water column (T) and the motor rotation frequency(n) could be expressed byT=19.77 exp(n/2.61)-71.7. Based on the total suspended amounts in water column under field wind conditions, quantitative relationships were achieved among the simulated hydrodynamic conditions, the total suspended amounts of sediments and the field wind conditions. According to the correspondent frequency of motor rotation to field wind speed in Lake Taihu from October 2004 to October 2005, the total suspended amounts of sediments were estimated at 159, 230 and 425 g/m² for field light, moderate and strong winds, respectively. The estimated amounts, together with the vertical distribution of suspended sediments in water column, were consistent with those observed under field conditions. The Y-shape apparatus was thus recommended for use in studying the ecological effects of sediment resuspension in shallow aqueous system.