典型砂姜黑土碳酸盐结核的物质来源、形成机制及环境意义

Carbonate nodules are key features used for paleoclimatic reconstructions and soil classification. The existence of carbonate nodules also affects physical and chemical properties of soil, such as soil texture, porosity, structure, nutrient content and water movement. The study on sources, formation mechanisms of carbonate nodules is very important in theory and practice. Shajiang Black Soils are a soil with special pedogenic characters and agricultural properties in Chinese subhumid area. Shajiang Black Soils are formed in low-lying and wet environment, the parent materials of Shajiang Black Soils are fluvio-lacustrine sediments. Shajiang Black Soils have two special layers:black soil layer and Shajiang layer. There are many studies about sources, element contents and formation mechanisms of carbonate noudles. But the direct evidence about sources of carbonate nodules and whole illustrate are absent . This study selected Yi river and Shu river drainage basin as study area. According to data about Shandong soil species, five typical Shajiang Black Soil profiles will be sampled.At the same time,relative surface water, ground water and rock samples are gathered. Through micromorphology, stable isotope geochemistry and element geochemistry, study the sources and formation mechanisms of carbonate nodules.Study the environmental implications of different part in carbonate nodules by sectioning. Make it clear the relations between the configuration and distribution of carbonate nodules and soil properties,such as texture,structure and porocity. The results can provide scientific evidences for reconstruction of historic environment and instruction for soil taxonomy.

碳酸盐结核（砂姜）是砂姜黑土成土过程的重要产物，关于其物质来源、元素组成及形成机制虽然已经开展了较多研究工作，但未能从区域尺度系统地研究其物质来源和形成机制，且对结核不同部位所揭示的环境变化研究较少。因此，本项目将以典型砂姜黑土分布的沂沭河流域为研究区域，系统采集不同景观部位的土壤剖面样品，同时采集相关的地表水、地下水及源区母岩样品，借助微形态特征、同位素组成（δ13C、δ18O、87Sr/86Sr）和元素地球化学组成特征，对碳酸盐结核的物质来源和形成机制进行综合研究。通过切片和微区分析，明确碳酸盐结核的性状特征与准确的物质来源，探讨碳酸盐结核所携带的环境信息，并据此分析结核形成的环境指示意义。通过野外实地观察和室内理化分析，明确土壤质地、结构、孔隙度等性质对碳酸盐结核的存在形态与剖面分布的影响。研究结果可为更好地发挥碳酸盐结核在重建古环境与土壤分类中的作用提供详实的科学依据。

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