三峡库区消落带土壤在周期蓄水影响下的磁性变化

Soil Magnetism Variations Under the Influence of Periodic High Water Level in the Water-level-fluctuating Zone of Three Gorges Reservoir Area

对三峡库区消落带内紫色土土壤磁化率空间分布特征及土壤粒径组成进行了系统性研究。重点探寻在长时间高压淹水与高温干旱交替变化条件下,消落带土壤磁化率特性的演变过程,阐明磁化率特性与土壤粒径空间分布的特定相关关系。研究表明,库岸坡地土壤经反季节周期性淹没后,其磁化率值宏观上沿着不同海拔自高到低先缓慢下降,维持一段平稳状态后再急速抬升。根据土壤粒径分布的变化规律可推断,此现象是在高水位时江水冲蚀以及低水位时雨水侵蚀等作用引起的水土流失过程中,土壤在坡面中上部侵蚀、分选及在下部堆积等多因素迭合造成的。

The spatial distribution of the purple soil magnetic susceptibility and the soil particles composition within the water-level-fluctuating zone of the Three Gorges reservoir area in Yangtze River is systematically studied.The characteristics evolution of soil magnetic susceptibility is a key point in the condition of long alternating time of hot,dry,and high-pressure flooding.And next,the distribution of soil particle size is clarified in order to reflect the specific relationship between soil magnetic susceptibility and different sizes.SM-30 portable magnetic susceptibility meter and Bartington MS2 magnetic susceptibility meter are used to determine soil magnetism,and Malvern Mastersizer 2000 laser particle size analyzer is used to derive soil particle volume percentage.After that,the essential reason has been discussed and analyzed based on the relationship between them.It has been demonstrated that firstly,the magnetic susceptibility slowly declines from high level to lower part along different macro-level altitude.And then a rapidly uplift will suddenly happens until more than 120×10-8m3/kg after the stable value area at the middle level.The reason for that is reasonable inferred that the upper slope suffers from the river erosion with high water level,and from the rain erosion with low water level.At the same time,the lower slope is under the control by the consequences of superposition,such as soil accumulation and many other factors.