| 摘要: |
| 基于2002年对太湖底泥分布的调查数据，利用最优插值法计算了整个太湖不同区域的底泥厚度。结果表明，太湖底泥总蓄积量大约在18．57亿m3，有泥区面积占整个水面积的47.5%左右。此外，利用Shields方法，计算了太湖表层1m内不同深度上底泥悬浮的临界切应力值，采用SMB浅水波动模式，计算了夏季受东南风和冬季受西北风影响下的波切应力，确定了不同风速情况下所能引起的底泥悬浮量。计算结果发现，上述何种风向情况下，能产生悬浮的临界风速大约在5—6m/s，当风速大于临界风速时，悬浮量随着风速的增加而增加；若风速达到20m/s时，所能引起的最大悬浮量约为2.75亿m3。 |
| 关键词: 底泥,再悬浮,太湖 |
| DOI： |
| 分类号: |
| 基金项目:中国科学院战略重大资助项目，KZCX1-SW-12号和国家自然科学基金资助项目，40071019号 |
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| CALCULATION OF TOTAL AND RESUSPENDABLE SEDIMENT VOLUME IN LAKE TAIHU |
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LUO Lian-Cong1,2, QIN Bo-Qiang1, ZHU Guang-Wei1
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1.Nanjing Institute of Geography and Limnology，Chinese Academy of Sciences;2.Graduate School of Chinese Academy of Sciences
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| Abstract: |
| Sediments in shallow lake are very informative to understand eutrophic problems duo to resuspension that results in increasing nutrient concentration, light attenuation and weakening phytoplankton photosynthesis related to primary production in water body. This preliminary work is to explore possible effects of sediment on water quality and to map the sediment distribution pattern. An investigation was made into recent sediment depth (RSD) in Lake Taihu in September 2002. A total of 119 sampling sites were irregularly but reasonably scattered in the lake. Constant pressure is imposed on an iron stick and the local RSD is arbitrarily decided by the stick. By employing optimum interpolation scheme, RSD was calculated based on a 1000 x 1000m grid net. Results show that tota1 recent sediment volume is about 18.57 x 108m3, mainly deposited in the western shoreline and northern parts. A notable exception is a patch between the center and Xishan Island where the maximum depth is more than 4.0m. which is probably associated with the high-speed current in this domain. The area of mud sedimention accounts for 47.5% of the whole water surface area with mean sediment depth ranging between 0.5— 3.5m. Of all the sediment regions, the area with RSD<0.5m are 16.2%; between 0.5— 1.0m, 12.6% ; 1.0— 2.0m, 21.2% ; 2.0— 3.0m, 25% , and>3.0m is 25% . Position to the inflow fiver is accountable for such a distributional pattern. To decide the threshold stresses for sediment resuspension at different depth(τcri, i=1, 2, 3, ? , 100), sediment size, density and water content in the top 30cm deposits were measured in laboratory. Based on fitting equation for density and Shields method, calculation was performed at different depth in the top 100cm to produce all the possible values of τcri. A SMB model for shallow-water area with verification conducted in Lake Taihu was used to predict significant wave height and period, which were then used to decide the bottom wave-induced stress(τu). The resuspension depth of sediment at the grid can be determined by finding the critical stress at a definite layer equal to or slightly smaller than τu, and resuspendable sediment amount can be then obtained by following the rule of volume calculation in a cube. Calculation results reveal that the minimum wind speed of wind (SE in summer and NW in winter) to resuspend the muddy sediment is 5— 6 m/s, and the suspended sediment amount would increase with increasing wind speed that is more drastically in summer than in winter. Possible maximum wind speed in Lake Taihu is 20.0 m/s by which the corresponding resuspended sediment volume would be about 2.75 x 108m3. Similarly, 0.25 x 108m3 sediment could be suspended at 10.0 m/s. These results could be of considerable assistance in limnic ecosystem research. |
| Key words: Sediment, Resuspension, Lake Taihu |
