| 摘要: |
| 滆湖自90年代以来水生态环境变化迅速，水生植物几乎消亡，生态系统由“草型清水”湖演变为“藻型浊水”湖，其浅水特性在风力作用下常造成底床沉积物的再悬浮现象。泥沙和营养物质频繁重回上覆水体导致水质长期难以改善，故重建沉水植物生境被认为是恢复滆湖生态环境的措施之一。本文构建滆湖水环境模型，模拟和分析水动力及沉积物的再悬浮过程。研究表明，在常规风力条件下（约2.2~2.8 m/s），全湖底床切应力均值（(τ_b ) ?）约为0.023 N/m2，全湖几乎不存在沉积物再悬浮现象，而在强风条件下（如大于10 m/s），(τ_b ) ?可达0.45 N/m2，全湖绝大部分区域的沉积物均可以发生再悬浮，南部浅水区域及其东西沿岸为再悬浮发生的高频地区。模型设定了一种沉水植物生境的情景条件进行模拟与预测。研究结果表明，在易发生再悬浮且适合沉水植物生长的南部区域，重建覆盖度约为12%的沉水植物，可削减实际条件下(τ_b ) ?的24.4%，从而分别降低年均和强风时刻全湖固体悬浮物浓度（TSS）的29.3%和25.1%。对一次强风过程的模拟结果表明，情景条件下(τ_b ) ?由实际条件下的0.45 N/m2下降为0.34 N/m2，全湖TSS均值和最大值对比实际条件分别下降了20.9 mg/L和470 mg/L，沉水植物生境的存在对全湖TSS浓度改善效果显著。 |
| 关键词: 滆湖 沉水植物 沉积物再悬浮 数学模型 情景预测 |
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| 基金项目:国家自然科学基金项目（41971137、U2240224、42001109）；南京工程学院校级科研基金（ZKJ201804）；江西省科技计划项目（20213AAG01012、20212BBG71002、20222BCD46002）联合资助 |
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| Modeling Study on Inhibition Effect of Recreating Submerged Plants Habitat for Sediment Resuspension in Lake Gehu |
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GONG RAN1, XU LIGANG2
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1.Nanjing Institute of Technology;2.Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences
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| Abstract: |
| The aquatic environment of Lake Gehu, the second largest shallow lake in Taihu basin, has undergone rapid changes since the 1990s, with almost total destruction of aquatic plants and the changing of ecological type from “grass-limpid” to “algae-turbid”. The sediment in this type of shallow lake is easy to suspend induced by strong wind, hence, recreation of submerged plants community was recognized to be one of the valid measures for restoring ecological environment in Lake Gehu. In this article, an environmental model was developed, to investigate the hydrodynamic process and sediment resuspension. The results show that, under nomal wind condition (2.2~2.8 m/s), the mean value of bed shear stress of the whole lake is about 0.023 N/m2, and there is almost no sediments re-suspension. However, this value can reach over 0.45 N/m2 under extreme wind condition (>10m/s), and sediment resuspension probably occurs in most part of the whole lake. The southern shallow area and its east and west coast are the high-frequency areas where sediment resuspension occurs. A scenario of reconstructing submerged plant habitat in the area prone to sediment resuspension and suitable for plant growth (covering about 12%) was set for prediction analysis. The results indicate that, under scenario condition, the average annual bed shear stress of the whole lake reduced 24.4% and thus respectively 29.3% and 25.1% for suspended solids concentration both in annual average and at the moment of strong wind. During a strong wind in simulation, the mean bed shear stress of the whole lake decreased from 0.45 to 0.34 N/m2 compared with the actual situation, and the mean and maximum concentrations of suspended solids decreased by 20.9 mg/L and 470 mg/L, respectively. The presence of submerged plant habitat is capable of significantly decreasing the concentration of total suspended solids in the lake. |
| Key words: Lake Gehu submerged plants sediment resuspension mathematical modeling scenario prediction |
