| 引用本文: | 冉凤维,聂小东,王诗兰,廖文飞,李忠武.近百年来洞庭湖粒度指示的沉积环境演变特征.湖泊科学,2023,35(3):1111-1125. DOI:10.18307/2023.0328 |
| Ran Fengwei,Nie Xiaodong,Wang Shilan,Liao Wenfei,Li Zhongwu.Evolutionary patterns of the sedimentary environment signified by grain size characteristics in Lake Dongting during the last century. J. Lake Sci.2023,35(3):1111-1125. DOI:10.18307/2023.0328 |
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| 摘要: |
| 湖泊沉积物储存着长时期的流域环境信息，是百年尺度湖泊环境演变研究的高分辨率记录器。本文通过210Pbex、137Cs组合定年法，分析放射性核素剖面特征，研究沉积速率时空变化规律，并解析沉积物粒度指示的环境信息，揭示百年尺度湖泊沉积环境演变。结果表明：洞庭湖210Pbex剖面分布呈现多段衰变型、混合-衰变-平衡型、衰变-本底型和无沉积型4种类型。3大湖体200 cm的沉积深度对应的年代跨度为127~162年，构建了洞庭湖沉积物深度-年代关系。洞庭湖平均质量沉积速率为1.47~3.11 g/（cm2·a），整体上呈现南洞庭湖>西洞庭湖>东洞庭湖的空间特征；自1900年后，质量沉积速率增加了3~7倍，呈时序增加趋势。沉积年代上，沉积物粒度特征表明洞庭湖沉积环境呈3个阶段2个过渡期的演变特征，与同时期区域内毁林开荒、水利建设、植树造林等人为活动有较好的对应关系，说明近百年来人为活动是洞庭湖泥沙沉积的重要因素。本研究结果可为强化湖泊及其流域生态环境保护提供理论参考。 |
| 关键词: 湖泊沉积物 放射性核素 沉积速率 粒度 洞庭湖 |
| DOI：10.18307/2023.0328 |
| 分类号: |
| 基金项目:国家自然科学基金项目（U19A2047）和湖南省自然科学基金项目（2022JJ30390）联合资助。 |
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| Evolutionary patterns of the sedimentary environment signified by grain size characteristics in Lake Dongting during the last century |
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Ran Fengwei1, Nie Xiaodong1, Wang Shilan1, Liao Wenfei2, Li Zhongwu1,2
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1.Hunan Provincial Key Laboratory for Eco-environmental Changes and Carbon Sequestration of the Dongting Lake Basin, School of Geographic Sciences, Hunan Normal University, Changsha 440081, P. R. China;2.College of Environmental Science and Engineering, Hunan University, Changsha 440082, P. R. China
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| Abstract: |
| Lake sediments record large amount of environmental information from the watershed over a long time, and has become a high-resolution archives for investigating the lake environmental change at the centennial scale. In this paper, we analyzed the features of radionuclide profiles through the combined dating method of 210Pbex and 137Cs, investigated the temporal and spatial changes of sedimentation rate, and extracted the environmental information indicated by sediment particle size to reveal the patterns of the sedimentary environment during the last century. The results showed that 210Pbex profiles presented four stages:a multi-stage decay, a mixed-decay-equilibrium, a decay-background and a no-deposition. The sediment depths of 200 cm in the three major lake bodies covered a chronological span of 127-162 years, and a depth-age relationship was constructed for Lake Dongting sediments. The mean mass accumulative rate (MAR) ranged from 1.47 to 3.11 g/(cm2·a), demonstrating an overall spatial characteristic of the highest MARs in the south, and higher in the west than the east. Since 1900, MARs in Lake Dongting increased 3-7 times, showing an upward trend in the chronology. The depositional change of sediment grain size in Lake Dongting was characterized by three stages and two transitional periods, which corresponded well with anthropogenic activities such as deforestation, hydrological construction, and afforestation in the basin in the period. These findings suggested that anthropogenic activities had been an important factor for sediment deposition in Lake Dongting. The foundings in our study can provide a theoretical reference for enhancing the ecological protection of the lake and its watershed. |
| Key words: Lake sediments radionuclide sedimentation rate grain size Lake Dongting |
