黄河中下游河水孢粉传输机制及其指示意义研究

Fluvial sediment is one of the sedimentary types that is frequently encountered in the study of Quaternary pollen. It widely distributes in inland basins and alluvial plains that in rivers’ downstream, and has great significance for restoring the paleoenvironment of the source areas. Although previous studies have shown that alluvial pollen reflects the environmental conditions in the upper reaches of the sample points, its transport mechanism in the river is still unclear, and the study of source areas is relatively weak. In this project, we select the mainstream and its main tributaries of the middle and lower reaches of the Yellow River as the research object. Thirty-five sampling sections are set up to collect water samples for pollen analysis during the flood or wet periods. The modern process of pollen in the middle and lower reaches of the Yellow River is studied and its transport mechanism and main influencing factors are revealed by using the methods of principal component analysis, dissimilarity coefficient analysis and Geodetector. On this basis, we aim at exploring the main source areas of water pollen in the lower reaches of the Yellow River and explaining their environmental significance. This study can provide scientific basis for the correct interpretation of stratum alluvial pollen, and the quantitative reconstruction of paleovegetation and paleoclimate. We expect that this study could solve the long-standing problem of how to use alluvial pollen to retrieve paleoenvironment in the floodplain of the Yellow River, and also provide great significance for similar studies in other basins.

河流相是第四纪孢粉研究中经常遇到的沉积类型之一，广泛分布于内陆盆地及河流下游冲积平原，对恢复源区古环境至关重要。尽管前人研究业已表明冲积物孢粉反映样点上游的环境状况，但其在河水中的传输机制尚不明确，源区研究也较为薄弱。本项目选取黄河中下游干流及其主要支流为研究对象，设置35个采样断面，在洪水期或丰水期采集河水样品进行孢粉分析，运用主成分分析、相异系数、地理探测器等研究方法，研究黄河中下游河水孢粉现代过程，揭示其传输机制和主要影响因素。在此基础上，探讨黄河下游河水孢粉的主要源区，进而阐明其环境意义。本项目可为地层冲积物孢粉的正确解译与古植被、古气候定量重建提供科学依据，可望在利用黄河下游泛滥平原冲积物孢粉反演古环境方面取得进展，对其他流域同类研究也具有重要参考意义。

厘清冲积物孢粉的形成机制及来源对古环境重建具有重要意义。尽管已有研究表明河流冲积物孢粉反映采样点上游流域的植被状况，但是孢粉在河水中的传输机制及影响因素尚不够明确，能否做到对源区植被的定量或半定量解译还需进一步研究。尤其是对于流域面积大、支流多、植被类型复杂的黄河流域河水孢粉源区的识别较为薄弱。针对以上问题，本项目以晋陕峡谷到开封段的黄河干流及其主要支流为研究对象，设置48个采样断面，在洪水期或丰水期采集河水样品和河流沉积物样品进行孢粉分析，采用相关性分析、相异系数分析、冗余分析、地理探测器等研究方法，揭示了黄河中游河水孢粉分布特征、河水孢粉来源及其与流域植被的关系，阐明了黄河中下游孢粉传输机制及其影响因素，探讨了黄河下游孢粉来源及其指示意义。项目执行期间发表论文5篇，获得授权国际发明专利2项，指导在读硕士研究生4名，较好的完成了项目成果目标。