东平湖沉积物物源示踪及黄河洪水事件判识

Dongping Lake is the largest flood storage lake at the lower reaches of the Yellow River, and this region was often influenced by the Yellow River floods during historical periods, which has formed a series of flood sediments. However, due to the influence of regional floods in this basin, distinguishing the Yellow River flood sediments from sediments of Dongping Lake is very difficult at the present time, and then affect identification of the Yellow River flooding events. Mineral and element geochemical tracing methods will be applied to investigate the sediment sources and its spatio-temporal distribution in Dongping Lake. Based on the result of provenance analysis, combining analyses of particle size, organic matter, magnetic susceptibility and sporopollen, the signatures between the Yellow River flood sediments and the regional flood sediments are distinguished, and then the Yellow River flooding events recorded by the Dongping Lake sediments were identified. This proposed project would be of great significance in further understanding the sedimentary source-sink process and environmental evolution in the area of Dongping Lake, revealing the Yellow River flooding events and its effects at the lower reaches of the Yellow River, as well as the study on river-lake relationship, flood control works construction, etc.

东平湖是黄河下游地区最大的蓄洪湖泊，历史时期黄河泛滥洪水经常影响该区域，形成了一系列的洪水沉积物。然而，由于流域区域性洪水的影响，黄河洪水沉积物判识存在较大困难，进而影响黄河洪水事件的判读。本项目拟运用矿物学、元素地球化学等物源示踪手段，分析东平湖地区沉积物来源及时空变化特征；根据物源示踪分析结果，结合沉积物粒度、有机质、磁化率、孢粉等多指标分析，区分出东平湖地区区域性洪水沉积物和黄河洪水沉积物之间的差别与特点，进而判识出历史时期东平湖沉积记录的黄河洪水事件。该研究对深入理解东平湖地区的沉积源汇过程与环境演化历史，揭示黄河下游地区的黄河洪水事件及其影响，以及在黄河下游地区河湖关系研究、蓄洪工程建设等方面均具有重要意义。

东平湖是黄河下游地区最大的蓄洪湖泊，历史时期黄河泛滥洪水经常影响该区域，形成了系列的洪水沉积物。本项目通过采集黄河、大汶河河漫滩以及东平湖表层与岩芯沉积物样品，重点分析了样品的黏土矿物、碎屑矿物、孢粉、粒度、元素等指标，区分出黄河洪水沉积物与东平湖流域大汶河洪水沉积物之间的差别与特点，运用矿物学物源示踪方法分析了东平湖地区沉积物来源及时空变化特征，并根据基于分层的贝叶斯定理的端元分析模型，定量计算出黄河与大汶河物质对东平湖现代沉积物的相对贡献量。研究结果表明，黄河沉积物的粘土矿物组成以伊利石为主（56.57%），其次为绿泥石（21.36%）、蒙皂石（12.01%）和高岭石（10.06%），伊利石结晶度平均为0.28；重矿物含量相对较低，为1.24%，重矿物组合为“普通角闪石－绿帘石－褐铁矿－阳起石”，特征矿物为辉石类矿物。大汶河沉积物粘土矿物中伊利石含量最高（70.66%），高岭石（12.24%）、绿泥石（11.99%）次之，含少量蒙皂石（5.11%），伊利石结晶度平均为0.46；大汶河沉积物中重矿物含量较黄河略高，为3.06%，重矿物组合为“绿帘石－普通角闪石－阳起石”，具有高绿帘石的特征。物源判识结果表明，东平湖现代沉积物主要受黄河物质影响，同时大汶河物质对其也有一定作用，主要集中在湖区东部。利用BEMMA模型进行端元分析，并根据东平湖粘土矿物对线性混合模型进行源反演，结果表明东平湖现代沉积物中黄河物质贡献约为58.99–72.33%，大汶河贡献相对较低，约为27.67–41.01%。该研究对深入理解东平湖地区的沉积源汇过程与环境演化历史，揭示黄河下游地区的黄河洪水事件及其影响，以及在黄河下游地区河湖关系研究、蓄洪工程建设等方面均具有重要意义。