基于地球化学方法定量示踪江苏海岸废黄河三角洲沉积物的来源

The scientific question in the present proposal is how much sediments are contributed to the abandoned Yellow River delta from Yellow River and Huai River, respectively. Identification of sediment sources plays an important role for understanding the sediment source-to-sink transport process from estuary to coast and continental shelf. Whilst, many researches about sediment sources at the estuaries or coast depositions in the past are qualitative or semi-quantitative. Furthermore, the study for quantifying the sediment sources at the estuaries or coast is limited because of the sediment grain size sorting and the material component differentiation during the sediment transport. Here, the sedimentary system of abandoned Yellow River delta is selected as the study area, as well as the Yellow River and Huai River deposition areas. First, the best tracer fingerprints for the sediment from Yellow River and Huai River transported to abandoned Yellow River delta are established, on the basis of the geochemical approach and statistical analysis. Then, the muddy and sandy sediment sources on the abandoned Yellow River delta are quantified by applying the sediment source mixing model and geochemical tracers. Finally, a scientific hypothesis could be tested: the muddy sediments on the abandoned Yellow River delta are mainly supplied by Yellow River; whereas, the sandy sediments are controlled by Huai River. The theoretical significance of the study lies in an improved understanding of the formation and evolution for muddy and sandy depositions on abandoned Yellow River delta, and also help to enrich the application of geochemical tracer methods in sediment dynamics.

本项目的科学问题是废黄河三角洲沉积中黄河与淮河来源的物质各有多大贡献。沉积物物源判别是认识流域-海岸-陆架沉积物输运源汇过程的重要依据。然而以往对于河口海岸沉积体的物源追踪研究多停留在定性或者半定量程度，定量追踪物源因海洋沉积物在输运过程中的粒度分选和物质组分发生分异而受到限制。本项目以废黄河陆上三角洲沉积体（汇区）为载体，结合黄河和淮河沉积物（源区），由沉积物“从源到汇”的地球化学过程入手，以元素地球化学为主要示踪方法，结合统计分析等手段，建立废黄河三角洲沉积物源区端元示踪指标体系；通过沉积物地球化学物源示踪混合模型，分粒级（泥质和砂质）定量追踪废黄河三角洲沉积体的物源贡献。验证工作假说：废黄河三角洲泥质沉积主要由黄河源物质补给，砂质沉积主要以淮河输入为主。该项研究成果将对揭示废黄河三角洲泥质和砂质沉积的形成和演化机制奠定基础，有助于丰富和完善地球化学示踪方法在沉积动力学中的应用。

沉积物物源识别是认识流域-海岸-陆架沉积物输运源汇过程的重要依据；然而以往对于河口海岸沉积体的物源追踪研究多停留在定性或者半定量程度，定量追踪物源因海洋沉积物在输运过程中的粒度分选和物质组分发生分异而受到限制。苏北废黄河三角洲作为中国一个典型的经历建设发育和破坏演变的河流三角洲，以快速淤积、快速侵蚀为主要特色，是定量化研究流域-海岸沉积物输运源汇过程的典型区域。为此，本项目针对废黄河三角洲沉积体，及其不同端元物质（黄河源和淮河源）开展了野外调查取样，完成了室内沉积物粒度分析、分粒级提取泥质和砂质沉积、地球化学元素测试分析、沉积相分析和14C测年分析。通过实验数据和统计分析，建立识别黄河源和淮河源泥质沉积物的最佳示踪指标组合为：Ca、Zn、Ba、Mn、P、Al；识别黄河源和淮河源砂质沉积物的最佳示踪指标组合为：Ca、Ba、Al。依据物质质量守恒原理，建立废黄河三角洲沉积体中泥质和砂质沉积的地球化学物源混合模型，定量化模拟计算了黄河源和淮河源对废黄河三角洲沉积体的贡献。结果表明：黄河源和淮河源对废黄河三角洲中泥质沉积的贡献分别为~82%和~18%；对其砂质沉积的贡献分别为~37%和~63%，基本验证了本研究的前期工作假说：废黄河三角洲泥质沉积主要由黄河源物质补给，砂质沉积主要以淮河输入为主。此外，不同物源显示的时空分布格局在一定程度上深化了目前对废黄河三角洲形成演化机制的认识和理解，丰富和完善了地球化学示踪方法在沉积动力学中的应用。