| 密西西比河入海水体悬沙浓度变化过程研究 |
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| 引用本文： | 杨江洁,戴志军,梅雪菲,FagherazziSergio.密西西比河入海水体悬沙浓度变化过程研究[J].海洋学报,2022,44(7):71-81. |
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| 作者姓名： | 杨江洁 戴志军 梅雪菲 FagherazziSergio |
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| 作者单位： | 1.华东师范大学 河口海岸学国家重点实验室，上海 200241 |
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| 基金项目： | 国家重点研发计划政府间国际科技创新合作重点专项（2018YFE0109900）；国家自然科学基金委?中华人民共和国水利部?中国长江三峡集团有限公司长江水科学研究联合基金（U2040202）；上海市“一带一路国际联合实验室”基金(21230750600)。 |
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| 摘 要： | 河流入海水体悬沙浓度的变化直接反映该流域人类活动和自然应力的影响。基于密西西比河塔伯特兰丁站长期水文资料，本文采用百分位法、Mann-Kendall法等统计方法对近40年密西西比河入海水体悬沙浓度进行分析，探究密西西比河通过“鸟足状”三角洲进入墨西哥湾的水体悬沙浓度变化过程及其可能影响因素。结果表明:（1）在1976?2015年期间，密西西比河入海水体悬沙浓度展现阶段性下降趋势，其中第一时期即1976?1987年期间，入海水体悬沙浓度相对较高，平均值为0.33 kg/m3；第二时期即1988?2015年期间，悬沙浓度较低且平均值为0.25 kg/m3。（2）密西西比河日径流量与悬沙浓度之间的关系符合高斯分布。与1976?1987年相比，1988?2015年期间水沙关系曲线较为扁平，日均超过0.60 kg/m3的高悬沙浓度事件明显减少。在低流量及起动流量阶段，悬沙浓度随着流量的增加而增加，在流量接近20 000 m3/s时，悬沙浓度达到最大值，流量高于20 000 m3/s后，悬沙浓度反而随着流量增加而减小。同时，密西西比河月均水沙关系在1976?1987年期间呈双绳套样，1988?2015年期间则呈现“先沙后水”的顺时针单一型绳套样。（3）分洪工程建设及土壤保持措施是影响密西西比河入海水体悬沙浓度的主要原因。其中，工程建设减少了河道沿程沉积物物源，土壤保持措施使土地侵蚀减少，从而使得悬沙浓度保持较低水平。此外，极端水文事件对密西西比河入海悬沙浓度的影响较小。
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| 关 键 词： | 悬沙浓度 径流量 水沙关系 密西西比河 |
| 收稿时间： | 2021-08-17 |
Variations of suspended sediment concentration of the Mississippi River delivered from land into sea |
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| Institution: | 1.State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China2.Department of Earth and Environment, Boston University, Boston 02215, USA |
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| Abstract: | The change of fluvial suspended sediment concentration (SSC) to the sea directly reflects the effects of riverine anthropogenic activities and natural force. Based on long-term hydrological data at Tarbert Landing Station of the Mississippi River (MR), statistical means, such as percentile method and Mann-Kendall method are used to detect change process of SSC from the MR entering the Gulf of Mexico in recent 40 years, and associated possible influencing factors. The results show that: (1) SSC from the MR entering the Gulf of Mexico is characterized by a staged decline from 1976 to 2015, in the first stage from 1976 to 1987, the SSC is relatively high with an average value of 0.33 kg/m3; in the second stage from 1988 to 2015, the SSC is much lower with a mean value of 0.25 kg/m3. (2) The relationship between daily SSC and runoff of MR follows Gaussian distribution. Compared with the first stage (1976?1987), the rating curve between SSC and runoff in the second stage (1988?2015) is relatively flat, when the number of high daily SSC event over 0.60 kg/m3 reduces significantly. SSC increases with the runoff in low-action flows and reaches the maximum when the runoff approaches 20 000 m3/s, but decreases with the runoff thereafter. The rating curve between monthly SSC and water discharge of the MR exhibits “double-loop” shape during 1976?1987, but presents clockwise “single loop” with “sediment before water” during 1988?2015. (3) Flood diversion project construction and soil conservation measures dominate the fluvial SSC from the MR into the Gulf of Mexico. The construction of flood diversion engineering reduces the sediment source along the river channel, and the soil conservation measures repress the land erosion, which have combined to keep the SSC at a relatively low level. In addition, SSC in the MR presents minor response to extreme hydrological events. |
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