网纹红土红色基质与白色条纹铁迁移模型

THE MODEL FOR IRON MIGRATION BETWEEN WHITE RETICULATED MOTTLES AND RED MATRIX

中国南方网纹红土是记录古环境变化的重要信息载体。网纹层内分布有红色基质和白色条纹，目前对网纹红土风化成土过程中铁的迁移情况尚存争议。根据质量平衡思想，本研究构建了网纹红土的铁迁移质量平衡模型。利用该迁移模型，以均质红土为参照物，采用我国中亚热带网纹红土、汤溪网纹红土剖面白色条纹和红色基质中Al、Ti、Fe含量的平均值、庐山WJ网纹红土剖面白色条纹和红色基质中Al、Ti、Fe含量，对网纹红土形成过程中铁迁移情况进行了分析。由我国中亚热带网纹红土白色条纹和红色基质中Al、Ti、Fe含量均值得到的铁迁移比为0.87%；由汤溪网纹红土白色条纹和红色基质中Al、Ti、Fe含量均值得到的铁迁移比为0.65%；庐山WJ剖面网纹层1至5的铁迁移比分别为0.10%、0.32%、0.86%、0.98%和0.55%。铁的迁移比大于零，揭示了可能存在着铁从白色条纹迁出但未淋溶出网纹层。我国中亚热带网纹红土的铁迁淋比为55%，汤溪网纹红土的铁迁淋比为60%，庐山WJ剖面网纹层1至5的铁迁淋比分别为10%、26%、50%、70%和51%等。在白色条纹形成过程中，铁在网纹层内的迁移和向网纹层外淋出情况很可能并存。

The Pleistocene reticulated red soil is traditionally regarded as good records of the paleoclimatic changes. The reticulated red soil layer in reticulated red soil section includes two parts：namely, the white reticulated mottles and the red matrix. However, there are still controversies over the iron migration from white reticulated mottles to red matrix during the pedogenesis process of reticulated red soil. The migration model for the iron of reticulated red soil layer has been developed in this paper based on the mass conservation law. By taking homogeneous red soil as parent material, the developed model was simulated with data input of the average content of Al, Fe, Ti of both the white reticulated mottles and the red matrix in reticulated laterite layer in mid subtropical zone of China, and the average content of Al, Fe, Ti of both the white reticulated mottles and the red matrix in Tangxi laterite soil section in Zhejiang, South China, and the content of Al, Ti, Fe of both the white reticulated mottles and the red matrix in Lushan WJ laterite soil section in Jiangxi, south China. The simulated results showed that, the average migration amount of iron from the white reticulated mottles to the red matrix in the middle subtropical zone of China and Tangxi laterite soil section is 0.87% and 0.65%, respectively. The migration amount of iron from the white reticulated mottles to the red matrix in 5 reticulated red soil layers in Lushan WJ section is 0.10%, 0.32%, 0.86%, 0.98% and 0.55%, respectively, which are all greater than zero, indicating the potential iron migration from white reticulated mottles to red matrix. The simulated results also showed that, the average migration amount of iron from white reticulated mottles to red matrix accounts for 55% and 60% of the total iron migration in the reticulated red soil in the middle subtropical zone of China and Tangxi section, respectively. Meanwhile, the migration amount of iron from white reticulated mottles to red matrix accounts for 10%, 26%, 50%, 70% and 51% of total iron migration in 5 reticulated red soil layers in Lushan WJ section, respectively. These results suggested that, during formation of white reticulated mottles, migration of iron from the white reticulated mottles to red matrix may be coexist with migration of iron outside of the reticulated red soil layer.