中国东北深厚黄土母质发育土壤发生学特征及其环境学意义

Deep soils derived from loess contain a wealth of paleoenvironment information. The deposition of loess is synchronous with pedogenic processes, which may mask original information of parent material and pedogenesis. The reliability and accuracy of paleoenvironmental information obtained by using different properties of loess as proxies is facing challenge. In order to improve the accuracy of paleoenvironment, pedogenesis researches of deep soils derived from loess should be enhanced and the properties of loess as parent material should be differentiated from that produced during soil formation. In this research, four or five deep loess profiles in the northeastern China will be selected. Soil samples will be collected in high resolution. The samples properties, such as elemental composition, basic physical and chemical properties, mineralogical features, micro-morphological characteristics and magnetic susceptibility will be analyzed according to the methodology of pedology, Quaternary geology, and geochemistry. X-ray diffraction, scanning electron microscopy, thin section, and X-ray diffraction fluorescence spectrometer and other instruments and techniques will be used. The parent material uniformity of deep loess soils should be firstly evaluated based on the field morphology, micro-morphology, particle size distribution, geochemical features, and clay mineralogy. Following this, quantitative models are used to explore the pedogenic process of deep loess and reconstruct the paleoenvironment. The results will be compared with the achievements obtained by other scientists in Chinese Loess Plateau and other areas. The results of this study should better reveal the formation process and mechanism of deep loess soils, enrich pedogenic theory, and improve the reliability and accuracy of the interpretation using different climate proxies. In addition, the findings will contribute to improve the understanding of spatial and temporal variation of loess by expanding the study area of loess research in China.

深厚黄土母质发育土壤蕴藏着丰富的古环境信息。然而，黄土沉积与土壤发育过程同时进行，母质特性与土壤发育属性混杂，以此为气候代用指标解译古环境信息的可靠性和准确性受到质疑。加强土壤发生学研究，厘清母深厚黄土质属性与土壤发育信息，是提高气候替代指标解译古环境信息可靠性和准确性的关键。本研究拟以东北地区4～5个深厚黄土母质发育土壤剖面为研究材料，综合运用土壤学、第四纪地质学、地球化学等多学科的研究方法，在测年的基础上，系统分析深厚黄土母质发育土壤的基本理化性质、地球化学元素组成、矿物学类型、磁化率、微形态学特征等，判定土壤母质均一性，利用定量模型探讨黄土形成发育过程，解译黄土中所蕴藏的环境信息，并与已有相关研究成果比较。研究结果不仅可以更好地揭示黄土的形成过程和机制，也能够提高气候替代指标的解译可靠性和准确性；并通过扩大我国黄土研究的区域范围，可以深化对黄土时空变化规律的认识。

黄土母质特性与土壤发育属性混杂，厘清黄土母质属性与土壤发育信息，是深入认识土壤形成机制，提高古环境信息解译准确性的关键。本研究以东北地区典型深厚黄土母质发育土壤为研究材料，系统分析了粒度大小、沉积速率等沉积特征，考察了粉尘沉降后土壤颗粒变化、地球化学元素运移等土壤发育特征，提出了深厚黄土母质土壤的形成模式，探讨了黄土低山丘陵区土壤类型的分布特征；定量重建11万年以来沈阳地区的古气候变化。主要研究成果有：.1.东北地区黄土母质粒度组成主要是粉砂粒，黏粒含量较低，质地以粉壤土、粉土和砂质壤土为主；自西向东砂粒含量明显减少，粉粒和黏粒增加；平均降尘沉积速率介于2.03-22.98cm/ka，空间变异较大，自西向东粉尘平均沉积速率不断减小，厚度减薄；现代粉尘沉积和土层加积增厚过程仍在继续。.2. 东北朝阳剖面（CY剖面）与黄土高原灵台剖面（LT剖面）AUCC标准化元素分布模式相似，具有相似的物源，然而，CY剖面发生了较强的脱硅和富铁铝化过程，而LT剖面土壤仍处于Ca和Na的淋失阶段。研究结果同时表明，深厚黄土剖面中各土层都有不同程度的发育。.3. 与传统土壤学普遍接受岩石风化土层逐步加深的土壤形成模式不同，深厚黄土的土壤形成模式是黄土沉积加厚与成土作用同步进行；气候变化造成深厚黄土母质土壤中出现处于不同发育阶段的多种古土壤类型。.4.在东北黄土低山丘陵区，同时存在多种反映水热条件的地带性土壤类型，它们不全是现代生物气候条件下的产物，而是深厚黄土母质发育土壤遭受侵蚀后不同深度不同发育程度的古土壤出露地表造成的结果。.5.定量重建了11万年以来沈阳地区的古气候，古年均降水量和古年均温度变化于501-807mm和8.5-13.5℃之间，期间气候经历过多次波动，总体呈现出从湿热至干冷的变化趋势。.研究结果加深了对东北地区黄土沉积与深厚黄土发育土壤形成过程和机制的理解，为正确认识土壤分布规律和提高古气候解译精度提供了科学基础。